Effects of phytoextraction on heavy metal concentrations and pH of pore-water of biosolids determined using an in situ sampling technique.

PubMed

Huynh, T T; Laidlaw, W S; Singh, B; Gregory, D; Baker, A J M

2008-12-01

Heavy metal concentrations and pH of pore-water in contaminated substrates are important factors in controlling metal uptake by plants. We investigated the effects of phytoextraction on these properties in the solution phase of biosolids and diluted biosolids in a 12-month phytoextraction column experiment. Phytoextraction using Salix and Populus spp. temporarily decreased pore-water pH of the substrates over the experimental period followed by a return to initial pH conditions. Salixxreichardtii and Populus balsamifera effectively extracted Ni, Zn and Cd and actively mobilized these metals from the solid to the solution phase. S.xreichardtii had the stronger effect on mobilization of metals due to its larger root system. Phytoextraction did not affect Cu in the solution phase of the biosolids. Heavy metals were leached down to lower depths of the columns during the phytoextraction process.

Chemistry of Sulfur-Contaminated Soil Substrate from a Former Frasch Extraction Method Sulfur Mine Leachate with Various Forms of Litter in a Controlled Experiment.

PubMed

Likus-Cieślik, Justyna; Pietrzykowski, Marcin; Chodak, Marcin

2018-01-01

The impact of tree litter on soil chemistry leachate and sulfurous substrates of mine soils from former Jeziórko sulfur mine was investigated. Composites were used: soil substrate (less contaminated at mean 5090 mg kg -1  S or high contaminated at 42,500 mg kg -1  S) + birch or pine litter and control substrate (no litter). The composites were rinsed with distilled water over 12 weeks. In the obtained leachate, pH, EC, dissolved organic carbon, N, Ca, Mg, Al, and S were determined. Physicochemical parameters of the substrates and their basal respiration rate were determined. Rinsing and litter application lowered sulfur concentration in high contamination substrates. Pine litter application decreased EC and increased pH of the low-contaminated substrate. The substrate pH remained at low phytotoxic level (i.e., below 3.0), resulting in the low biological activity of the composites. Birch litter application increased leaching of N and Mg, indicating the possibility of an intensification of soil-forming processes in contaminated sites.

A multiphase mixture model for substrate concentration distribution characteristics and photo-hydrogen production performance of the entrapped-cell photobioreactor.

PubMed

Guo, Cheng-Long; Cao, Hong-Xia; Pei, Hong-Shan; Guo, Fei-Qiang; Liu, Da-Meng

2015-04-01

A multiphase mixture model was developed for revealing the interaction mechanism between biochemical reactions and transfer processes in the entrapped-cell photobioreactor packed with gel granules containing Rhodopseudomonas palustris CQK 01. The effects of difference operation parameters, including operation temperature, influent medium pH value and porosity of packed bed, on substrate concentration distribution characteristics and photo-hydrogen production performance were investigated. The results showed that the model predictions were in good agreement with the experimental data reported. Moreover, the operation temperature of 30 °C and the influent medium pH value of 7 were the most suitable conditions for photo-hydrogen production by biodegrading substrate. In addition, the lower porosity of packed bed was beneficial to enhance photo-hydrogen production performance owing to the improvement on the amount of substrate transferred into gel granules caused by the increased specific area for substrate transfer in the elemental volume. Copyright © 2015 Elsevier Ltd. All rights reserved.

Stabilizing the baseline current of a microbial fuel cell-based biosensor through overpotential control under non-toxic conditions.

PubMed

Stein, Nienke E; Hamelers, Hubertus V M; Buisman, Cees N J

2010-04-01

A MFC-based biosensor can act as online toxicity sensor. Electrical current is a direct linear measure for metabolic activity of electrochemically active microorganisms. Microorganisms gain energy from anodic overpotential and current strongly depends on anodic overpotential. Therefore control of anodic overpotential is necessary to detect toxic events and prevent false positive alarms. Anodic overpotential and thus current is influenced by anode potential, pH, substrate and bicarbonate concentrations. In terms of overpotential all factor showed a comparable effect, anode potential 1.2% change in current density per mV, pH 0.43%/mV, bicarbonate 0.75%/mV and acetate 0.8%/mV. At acetate saturation the maximum acetate conversion rate is reached and with that a constant bicarbonate concentration. Control of acetate and bicarbonate concentration can be less strict than control of anode potential and pH. Current density changes due to changing anode potential and pH are in the same order of magnitude as changes due to toxicity. Strict control of pH and anode potential in a small range is required. The importance of anodic overpotential control for detection of toxic compounds is shown. To reach a stable baseline current under nontoxic conditions a MFC-based biosensor should be operated at controlled anode potential, controlled pH and saturated substrate concentrations. 2009 Elsevier B.V. All rights reserved.

Relative significances of pH and substrate starch level to roles of Streptococcus bovis S1 in rumen acidosis.

PubMed

Chen, Lianmin; Liu, Shimin; Wang, Hongrong; Wang, Mengzhi; Yu, Lihuai

2016-12-01

To clarify the relative importance of pH and substrate starch level in fermentation characteristics and regulatory mechanism of Streptococcus bovis S1 in rumen acidosis, an in vitro fermentation of three levels of soluble starch (1, 3 and 9 g/L) was established with pH in the media were maintained constant at 5.5 or 6.5. The results showed that the dominant product of S. bovis S1 was lactate at both pH, the production depended on the starch level, and more lactate was produced at pH 6.5 than that at pH 5.5 (P < 0.001). At pH 5.5, the activity of lactate dehydrogenase (LDH) and α-amylase (α-AMY), their abundances, the relative expressions of LDH, PFL (gene encoding pyruvate formate-lyase), CCPA (gene encoding global catabolite control protein A) and α-AMY genes were higher than those at pH 6.5 (P < 0.05), whereas the concentration of fructose-1,6-diphosphate (FDP) was lower. The activity of LDH, α-AMY and FDP, and the relative expressions of LDH, PFL, CCPA and α-AMY genes were, in general, positively related to the starch level. The canonical regression analysis indicated that the pH had more profound effect compared with the starch level, in terms of the acid productions, enzyme activity and gene expressions. It was concluded that the fermentation of S. bovis was regulated at the transcription level in response to both pH and substrate starch concentration, but more sensitive to pH changes.

Zeta potential of microfluidic substrates: 1. Theory, experimental techniques, and effects on separations.

PubMed

Kirby, Brian J; Hasselbrink, Ernest F

2004-01-01

This paper summarizes theory, experimental techniques, and the reported data pertaining to the zeta potential of silica and silicon with attention to use as microfluidic substrate materials, particularly for microchip chemical separations. Dependence on cation concentration, buffer and cation type, pH, cation valency, and temperature are discussed. The Debye-Hückel limit, which is often correctly treated as a good approximation for describing the ion concentration in the double layer, can lead to serious errors if it is extended to predict the dependence of zeta potential on the counterion concentration. For indifferent univalent electrolytes (e.g., sodium and potassium), two simple scalings for the dependence of zeta potential on counterion concentration can be derived in high- and low-zeta limits of the nonlinear Poisson-Boltzman equation solution in the double layer. It is shown that for most situations relevant to microchip separations, the high-zeta limit is most applicable, leading to the conclusion that the zeta potential on silica substrates is approximately proportional to the logarithm of the molar counterion concentration. The zeta vs. pH dependence measurements from several experiments are compared by normalizing the zeta based on concentration.

[Research on the preparative method of Arctigenin].

PubMed

Zhang, Li-Ying; Yang, Yi-Shun; Zhang, Tong; Ding, Yue; Cai, Zhen-Zhen; Tao, Jian-Sheng

2012-03-01

To research on the preparation of Arctigenin in vitro. Took enzyme concentration, time course and substrate concentration as investigation factors, used Box-Behnken design-response surface methodology to optimize the enzyme hydrolysis path of Arctigenin. The best operational path for Arctigenin was as follows: the temperature was 50 degrees C, pH was 4.8, enzyme concentration was 0.44 U/mL, time course was 46.81 min, substrate concentration was 0.29 mg/mL, the conversion rate was 90.94%. This research can be regarded as a referencein preparing Arctigenin in vitro.

Solid-substrate bioprocessing of cow dung for the production of carboxymethyl cellulase by Bacillus halodurans IND18.

PubMed

Vijayaraghavan, P; Prakash Vincent, S G; Dhillon, G S

2016-02-01

The production of carboxymethyl cellulase (CMCase) by Bacillus halodurans IND18 under solid substrate fermentation (SSF) using cow dung was optimized through two level full factorial design and second order response surface methodology (RSM). The central composite design (CCD) was employed to optimize the vital fermentation parameters, such as pH of the substrate, concentration of nitrogen source (peptone) and ion (sodium dihydrogen phosphate) sources in medium for achieving higher enzyme production. The optimum medium composition was found to be 1.46% (w/w) peptone, 0.095% (w/w) sodium dihydrogen phosphate and pH 8.0. The model prediction of 4210IU/g enzyme activity at optimum conditions was verified experimentally as 4140IU/g. The enzyme was active over a broad temperature range (40-60±1°C) and pH (7.0-9.0) with maximal activity at 60±1°C and pH 8.0. This study demonstrated the potential of cow dung as novel substrate for CMCase production. Copyright © 2015 Elsevier Ltd. All rights reserved.

Decolorization of Anthraquinonic Dyes from Textile Effluent Using Horseradish Peroxidase: Optimization and Kinetic Study

PubMed Central

Šekuljica, Nataša Ž.; Prlainović, Nevena Ž.; Stefanović, Andrea B.; Žuža, Milena G.; Čičkarić, Dragana Z.; Mijin, Dušan Ž.; Knežević-Jugović, Zorica D.

2015-01-01

Two anthraquinonic dyes, C.I. Acid Blue 225 and C.I. Acid Violet 109, were used as models to explore the feasibility of using the horseradish peroxidase enzyme (HRP) in the practical decolorization of anthraquinonic dyes in wastewater. The influence of process parameters such as enzyme concentration, hydrogen peroxide concentration, temperature, dye concentration, and pH was examined. The pH and temperature activity profiles were similar for decolorization of both dyes. Under the optimal conditions, 94.7% of C.I. Acid Violet 109 from aqueous solution was decolorized (treatment time 15 min, enzyme concentration 0.15 IU/mL, hydrogen peroxide concentration 0.4 mM, dye concentration 30 mg/L, pH 4, and temperature 24°C) and 89.36% of C.I. Acid Blue 225 (32 min, enzyme concentration 0.15 IU/mL, hydrogen peroxide concentration 0.04 mM, dye concentration 30 mg/L, pH 5, and temperature 24°C). The mechanism of both reactions has been proven to follow the two substrate ping-pong mechanism with substrate inhibition, revealing the formation of a nonproductive or dead-end complex between dye and HRP or between H2O2 and the oxidized form of the enzyme. Both chemical oxygen demand and total organic carbon values showed that there was a reduction in toxicity after the enzymatic treatment. This study verifies the viability of use of horseradish peroxidase for the wastewaters treatment of similar anthraquinonic dyes. PMID:25685837

Stabilization of pH in solid-matrix hydroponic systems

NASA Technical Reports Server (NTRS)

Frick, J.; Mitchell, C. A.

1993-01-01

2-[N-morpholino]ethanesulfonic acid (MES) buffer or Amberlite DP-1 (cation-exchange resin beads) were used to stabilize substrate pH of passive-wicking, solid-matrix hydroponic systems in which small canopies of Brassica napus L. (CrGC 5-2, genome : ACaacc) were grown to maturity. Two concentrations of MES (5 or 10 mM) were included in Hoagland 1 nutrient solution. Alternatively, resin beads were incorporated into the 2 vermiculite : 1 perlite (v/v) growth medium at 6% or 12% of total substrate volume. Both strategies stabilized pH without toxic side effects on plants. Average seed yield rates for all four pH stabilization treatments (13.3 to 16.9 g m-2 day-1) were about double that of the control (8.2 g m-2 day-1), for which there was no attempt to buffer substrate pH. Both the highest canopy seed yield rate (16.9 g m-2 day-1) and the highest shoot harvest index (19.5%) occurred with the 6% resin bead treatment, even though the 10 mM MES and 12% bead treatments maintained pH within the narrowest limits. The pH stabilization methods tested did not significantly affect seed oil and protein contents.

Some characteristics of fructose 1,6-diphosphatase activity in rat liver

NASA Technical Reports Server (NTRS)

Ashman, P. U.; Lampkin, S. L.; Dillon, L.; Parks, R.

1974-01-01

A reliable assay for hepatic fructose 1,6-diphosphatase in the rat was developed. It was found that the greatest enzymic activity and highest protein levels were eluted from the colored portion of the homogenate. When the substrate concentration was 0.01M, the enzyme had optimal activity when incubated with 0.01M MgSO4 for 10 min. at 37 C in 0.05M Tris-HC1 buffer, pH 7.5. Specificity for the substrate, fructose 1,6-diphosphate, was obtained at substrate concentration of 0.01M.

[Study on preparation of sagittatoside B with epimedin B converted from cellulase].

PubMed

Xu, Feng-Juan; Sun, E; Zhang, Zhen-Hai; Cui, Li; Jia, Xiao-Bin

2014-01-01

To prepare sagittatoside B with epimedin B Hydrolyzed from cellulase. With the conversion ratio as the index, the effects of pH value, temperature, reaction time, dosage of enzyme and concentration of substrates on the conversion ratio were detected. L9 (3(4)) orthogonal design was adopted to optimize the preparation process. Hydrolyzed products were identified by MS, 1H-NMR, and 13C-NMR. The results showed that the optimum reaction conditions for the enzymatic hydrolysis were that the temperature was 50 degrees C, the reaction medium was pH 5.6 acetic acid-sodium acetate buffer solution, the concentration of substrates was 20 g x L(-1), the mass ratio between enzyme and substrate was 3: 5, and the relative molecular mass of the reaction product was 646.23. NMR data proved that the product was sagittatoside B. The process is simple and reliable under mild reaction conditions, thus suitable for industrial production.

Mechanistic Studies of the Yeast Polyamine Oxidase Fms1: Kinetic Mechanism, Substrate Specificity, and pH Dependence†

PubMed Central

Adachi, Mariya S.; Torres, Jason M.; Fitzpatrick, Paul F.

2010-01-01

The flavoprotein oxidase Fms1 from Saccharomyces cerevisiae catalyzes the oxidation of spermine and N1-acetylspermine to yield spermidine and 3-aminopropanal or N-acetyl-3-aminopropanal. The kinetic mechanism of the enzyme has been determined with both substrates. The initial velocity patterns are ping-pong, consistent with reduction being kinetically irreversible. Reduction of Fms1 by either substrate is biphasic. The rate constant for the rapid phase varies with the substrate concentration, with limiting rates for reduction of the enzyme of 126 and 1410 s−1 and apparent Kd values of 24.3 and 484 μM for spermine and N1-acetylspermine, respectively. The rapid phase is followed by a concentration-independent phase that is slower than turnover. The reaction of the reduced enzyme with oxygen is monophasic, with a rate constant of 402 mM−1 s−1 with spermine at 25 °C, and 204 mM−1 s−1 with N1-acetylspermine at 4 °C, pH 9.0. This step is followed by rate-limiting product dissociation. The kcat/Kamine-pH profiles are bell-shaped, with an average pKa value of 9.3 with spermine and pKa values of 8.3 and 9.6 with N1-acetylspermine. Both profiles are consistent with the active forms of substrates having two charged nitrogens. The pH profiles for the rate constant for flavin reduction show pKa values of 8.3 and 7.2 for spermine and N1-acetylspermine, respectively, for groups that must be unprotonated; these pKa values are assigned to the substrate N4. The kcat/KO2-pH profiles show pKa values of 7.5 for spermine and 6.8 for N1-acetylspermine. With both substrates, the kcat value decreases when a single residue is protonated. PMID:21067138

The Impact of the Hepatocyte-to-Plasma pH Gradient on the Prediction of Hepatic Clearance and Drug-Drug Interactions for CYP2C9 and CYP3A4 Substrates.

PubMed

Rougée, Luc R A; Mohutsky, Michael A; Bedwell, David W; Ruterbories, Kenneth J; Hall, Stephen D

2017-09-01

Surrogate assays for drug metabolism and inhibition are traditionally performed in buffer systems at pH 7.4, despite evidence that hepatocyte intracellular pH is 7.0. This pH gradient can result in a pK a -dependent change in intracellular/extracellular concentrations for ionizable drugs that could affect predictions of clearance and P450 inhibition. The effect of microsomal incubation pH on in vitro enzyme kinetic parameters for CYP2C9 (diclofenac, (S)-warfarin) and CYP3A4 (midazolam, dextromethorphan, testosterone) substrates, enzyme specific reversible inhibitors (amiodarone, desethylamiodarone, clozapine, nicardipine, fluconazole, fluvoxamine, itraconazole) and a mechanism-based inhibitor (amiodarone) was investigated. Intrinsic clearance through CYP2C9 significantly increased (25% and 50% for diclofenac and (S)-warfarin respectively) at intracellular pH 7.0 compared with traditional pH 7.4. The CYP3A4 substrate dextromethorphan intrinsic clearance was decreased by 320% at pH 7.0, while midazolam and testosterone remained unchanged. Reversible inhibition of CYP2C9 was less potent at pH 7.0 compared with 7.4, while CYP3A4 inhibition potency was variably affected. Maximum enzyme inactivation rate of amiodarone toward CYP2C9 and CYP3A4 decreased at pH 7.0, while the irreversible inhibition constant remained unchanged for CYP2C9, but decreased for CYP3A4 at pH 7.0. Predictions of clearance and drug-drug interactions made through physiologically based pharmacokinetic models were improved with the inclusion of predicted intracellular concentrations based at pH 7.0 and in vitro parameters determined at pH 7.0. No general conclusion on the impact of pH could be made and therefore a recommendation to change buffer pH to 7.0 cannot be made at this time. It is recommended that the appropriate hepatocyte intracellular pH 7.0 be used for in vitro determinations when in vivo predictions are made. Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.

Overlay coating degradation by simultaneous oxidation and coating/substrate interdiffusion. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Nesbitt, J. A.

1983-01-01

Degradation of NiCrAlZr overlay coatings on various NiCrAl substrates was examined after cyclic oxidation. Concentration/distance profiles were measured in the coating and substrate after various oxidation exposures at 1150 C. For each stubstrate, the Al content in the coating decreased rapidly. The concentration/distance profiles, and particularly that for Al, reflected the oxide spalling resistance of each coated substrate. A numerical model was developed to simulate diffusion associated with overlay-coating degradation by oxidation and coating/substrate interdiffusion. Input to the numerical model consisted of the Cr and Al content of the coating and substrate, ternary diffusivities, and various oxide spalling parameters. The model predicts the Cr and Al concentrations in the coating and substrate after any number of oxidation/thermal cycles. The numerical model also predicts coating failure based on the ability of the coating to supply sufficient Al to the oxide scale. The validity of the model was confirmed by comparison of the predicted and measured concentration/distance profiles. The model was subsequently used to identify the most critical system parameters affecting coating life.

Process Optimization on Micro-Aeration Supply for High Production Yield of 2,3-Butanediol from Maltodextrin by Metabolically-Engineered Klebsiella oxytoca

PubMed Central

Jantama, Sirima Suvarnakuta; Kanchanatawee, Sunthorn

2016-01-01

An optimization process with a cheap and abundant substrate is considered one of the factors affecting the price of the production of economical 2,3-Butanediol (2,3-BD). A combination of the conventional method and response surface methodology (RSM) was applied in this study. The optimized levels of pH, aeration rate, agitation speed, and substrate concentration (maltodextrin) were investigated to determine the cost-effectiveness of fermentative 2,3-BD production by metabolically-engineered Klebsiella oxytoca KMS005. Results revealed that pH, aeration rate, agitation speed, and maltodextrin concentration at levels of 6.0, 0.8 vvm, 400 rpm, and 150 g/L respectively were the optimal conditions. RSM also indicated that the agitation speed was the most influential parameter when either agitation and aeration interaction or agitation and substrate concentration interaction played important roles for 2,3-BD production by the strain from maltodextrin. Under interim fed-batch fermentation, 2,3-BD concentration, yield, and productivity were obtained at 88.1±0.2 g/L, 0.412±0.001 g/g, and 1.13±0.01 g/L/h respectively within 78 h. PMID:27603922

Yeast Acid Phosphatase in a Student Laboratory.

ERIC Educational Resources Information Center

Barbaric, Sloeodan; Ries, Blanka

1988-01-01

Examines the influence of enzyme and substrate concentrations, pH, temperature, and inhibitors on catalytic activity. Follows the influence of different phosphate concentrations in the growth medium on enzyme activity. Studies regulation of enzyme synthesis by repression. Includes methodology for six experiments. (MVL)

Continuous ethanol production from cheese whey fermentation by Candida pseudotropicalis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghaly, A.E.; El-Taweel, A.A.

1997-12-01

Three pilot-scale continuous mix reactors of 5-L volume each were used to study the effects of retention time (18--42 hours) and initial substrate concentration (50--150 g/L) on the cell yield, lactose consumption, and maximum ethanol concentration during continuous fermentation of cheese whey using the yeast Candida pseudotropicalis. A microaeration rate of 480 mL/min and a nutrient supplement (yeast extract) concentration of 0.1% vol/vol were used. The results indicated that the dissolved oxygen concentration, temperature, cell concentration, lactose utilization rate, and ethanol concentration were affected by hydraulic retention time and initial substrate concentration. The highest cell concentration of 5.46 g/L andmore » the highest ethanol concentration of 57.96 g/L (with a maximum ethanol yield of 99.6% from the theoretical yield) were achieved at the 42-hour hydraulic retention time and the 150 g/L initial substrate concentration, whereas the highest cell yield was observed at the 50 g/L initial substrate concentration and the 36-hour hydraulic retention time. Lactose utilizations of 98, 91, and 83% were obtained with 50, 100, and 150 g/L initial substrate concentrations at the 42-hour hydraulic retention time. A pH control system was found unnecessary.« less

Simultaneous saccharification and fermentation of fungal pretreated cornstalk for hydrogen production using Thermoanaerobacterium thermosaccharolyticum W16.

PubMed

Zhao, Lei; Cao, Guang-Li; Wang, Ai-Jie; Guo, Wan-Qian; Ren, Hong-Yu; Ren, Nan-Qi

2013-10-01

In this research, environmentally friendly fungal pretreatment was first adopted for deconstruction of cornstalk. Then the fungal-pretreated cornstalk was employed to produce hydrogen in simultaneous saccharification and fermentation (SSF) using crude enzyme from Trichoderma viride and Thermoanaerobacterium thermosaccharolyticum W16. The influence of various factors including substrate concentration, initial pH, and enzyme loading on hydrogen production were evaluated. The highest hydrogen yield of 89.3 ml/g-cornstalk was obtained with an initial pH 6.5, 0.75% substrate concentration, and 34 FPU/g cellulose. Compared the result with SSF of physical or chemical pretreated lignocellulosic materials, this research suggested an economic and efficient way for hydrogen production from lignocellulosic biomass. Copyright © 2013 Elsevier Ltd. All rights reserved.

Modeling of ultrasonic degradation of non-volatile organic compounds by Langmuir-type kinetics.

PubMed

Chiha, Mahdi; Merouani, Slimane; Hamdaoui, Oualid; Baup, Stéphane; Gondrexon, Nicolas; Pétrier, Christian

2010-06-01

Sonochemical degradation of phenol (Ph), 4-isopropylphenol (4-IPP) and Rhodamine B (RhB) in aqueous solutions was investigated for a large range of initial concentrations in order to analyze the reaction kinetics. The initial rates of substrate degradation and H(2)O(2) formation as a function of initial concentrations were determined. The obtained results show that the degradation rate increases with increasing initial substrate concentration up to a plateau and that the sonolytic destruction occurs mainly through reactions with hydroxyl radicals in the interfacial region of cavitation bubbles. The rate of H(2)O(2) formation decreases with increasing substrate concentration and reaches a minimum, followed by almost constant production rate for higher substrate concentrations. Sonolytic degradation data were analyzed by the models of Okitsu et al. [K. Okitsu, K. Iwasaki, Y. Yobiko, H. Bandow, R. Nishimura, Y. Maeda, Sonochemical degradation of azo dyes in aqueous solution: a new heterogeneous kinetics model taking into account the local concentration OH radicals and azo dyes, Ultrason. Sonochem. 12 (2005) 255-262.] and Seprone et al. [N. Serpone, R. Terzian, H. Hidaka, E. Pelizzetti, Ultrasonic induced dehalogenation and oxidation of 2-, 3-, and 4-chlorophenol in air-equilibrated aqueous media. Similarities with irradiated semiconductor particulates, J. Phys. Chem. 98 (1994) 2634-2640.] developed on the basis of a Langmuir-type mechanism. The five linearized forms of the Okitsu et al.'s equation as well as the non-linear curve fitting analysis method were discussed. Results show that it is not appropriate to use the coefficient of determination of the linear regression method for comparing the best-fitting. Among the five linear expressions of the Okitsu et al.'s kinetic model, form-2 expression very well represent the degradation data for Ph and 4-IPP. Non-linear curve fitting analysis method was found to be the more appropriate method to determine the model parameters. An excellent representation of the experimental results of sonolytic destruction of RhB was obtained using the Serpone et al.'s model. The Serpone et al.'s model gives a worse fit for the sonolytic degradation data of Ph and 4-IPP. These results indicate that Ph and 4-IPP undergo degradation predominantly at the bubble/solution interface, whereas RhB undergoes degradation at both bubble/solution interface and in the bulk solution. (c) 2010 Elsevier B.V. All rights reserved.

Ultrasonic degradation of acetaminophen in water: effect of sonochemical parameters and water matrix.

PubMed

Villaroel, Erica; Silva-Agredo, Javier; Petrier, Christian; Taborda, Gonzalo; Torres-Palma, Ricardo A

2014-09-01

This paper deals about the sonochemical water treatment of acetaminophen (ACP, N-acetyl-p-aminophenol or paracetamol), one of the most popular pharmaceutical compounds found in natural and drinking waters. Effect of ultrasonic power (20-60 W), initial ACP concentration (33-1323 μmol L(-1)) and pH (3-12) were evaluated. High ultrasonic powers and, low and natural acidic pH values favored the efficiency of the treatment. Effect of initial substrate concentration showed that the Langmuir-type kinetic model fit well the ACP sonochemical degradation. The influence of organic compounds in the water matrix, at concentrations 10-fold higher than ACP, was also evaluated. The results indicated that only organic compounds having a higher value of the Henry's law constant than the substrate decrease the efficiency of the treatment. On the other hand, ACP degradation in mineral natural water showed to be strongly dependent of the initial substrate concentration. A positive matrix effect was observed at low ACP concentrations (1.65 μmol L(-1)), which was attributed to the presence of bicarbonate ion in solution. However, at relative high ACP concentrations a detrimental effect of matrix components was noticed. Finally, the results indicated that ultrasonic action is able to transform ACP in aliphatic organic compounds that could be subsequently eliminated in a biological system. Copyright © 2014 Elsevier B.V. All rights reserved.

pH-dependent electron-transport properties of carbon nanotubes.

PubMed

Back, Ju Hee; Shim, Moonsub

2006-11-30

Carbon nanotube electrochemical transistors integrated with microfluidic channels are utilized to examine the effects of aqueous electrolyte solutions on the electron-transport properties of single isolated carbon nanotubes. In particular, pH and concentration of supporting inert electrolytes are examined. A systematic threshold voltage shift with pH is observed while the transconductance and subthreshold swing remain independent of pH and concentration. Decreasing pH leads to a negative shift of the threshold voltage, indicating that protonation does not lead to hole doping. Changing the type of contact metal does not alter the observed pH response. The pH-dependent charging of SiO2 substrate is ruled out as the origin based on measurements with suspended nanotube transistors. Increasing the ionic strength leads to reduced pH response. Contributions from possible surface chargeable chemical groups are considered.

Strategy for pH control and pH feedback-controlled substrate feeding for high-level production of L-tryptophan by Escherichia coli.

PubMed

Cheng, Li-Kun; Wang, Jian; Xu, Qing-Yang; Zhao, Chun-Guang; Shen, Zhi-Qiang; Xie, Xi-Xian; Chen, Ning

2013-05-01

Optimum production of L-tryptophan by Escherichia coli depends on pH. Here, we established conditions for optimizing the production of L-tryptophan. The optimum pH range was 6.5-7.2, and pH was controlled using a three-stage strategy [pH 6.5 (0-12 h), pH 6.8 (12-24 h), and pH 7.2 (24-38 h)]. Specifically, ammonium hydroxide was used to adjust pH during the initial 24 h, and potassium hydroxide and ammonium hydroxide (1:2, v/v) were used to adjust pH during 24-38 h. Under these conditions, NH4 (+) and K(+) concentrations were kept below the threshold for inhibiting L-tryptophan production. Optimization was also accomplished using ratios (v/v) of glucose to alkali solutions equal to 4:1 (5-24 h) and 6:1 (24-38 h). The concentration of glucose and the pH were controlled by adjusting the pH automatically. Applying a pH-feedback feeding method, the steady-state concentration of glucose was maintained at approximately 0.2 ± 0.02 g/l, and acetic acid accumulated to a concentration of 1.15 ± 0.03 g/l, and the plasmid stability was 98 ± 0.5 %. The final, optimized concentration of L-tryptophan was 43.65 ± 0.29 g/l from 52.43 ± 0.38 g/l dry cell weight.

Effect of various factors on the activity of trehalase from the larvae of Sesamia inferens Walker (Insect).

PubMed

Agarwal, A K

1976-12-15

Trehalase from the salivary glands and the midgut of Sesamia inferens showed optimum activity at pH 5.8, and at temperatures of 50 and 60 degrees C respectively. The increase in the incubation period, enzyme concentration, and substrate concentration respectively increased the end-product, the hydrolysis, and the rate of hydrolysis of the substrate. Dialysis did not affect, tryptophan accelerated, and other amino acids and end-product inhibited the enzyme activity.

Method for plating with metal oxides

DOEpatents

Silver, Gary L.; Martin, Frank S.

1994-08-23

A method of plating hydrous metal oxides on at least one substrate, which method is indifferent to the electrochemical properties of the substrate, and comprises reacting metallic ions in aqueous solution with an appropriate oxidizing agent such as sodium hypochlorite or calcium sulfite with oxygen under suitable conditions of pH and concentration such that oxidation and precipitation of metal oxide are sufficiently slow to allow satisfactory plating of metal oxide on the substrate.

Irrigation water acidification to neutralize alkalinity for nursery crop production: Substrate pH, electrical conductivity, nutrient concentrations, and plant nutrition and growth

USDA-ARS?s Scientific Manuscript database

Liming agents in irrigation water, typically associated with carbonates and bicarbonates of calcium and magnesium, contribute to water alkalinity. Repeated application of LA to container crops can cause media-solution pH to rise overtime, that uncorrected, can lead to a nutrient availability imbalan...

Corrosion protection of galvanized steels by silane-based treatments

NASA Astrophysics Data System (ADS)

Yuan, Wei

The possibility of using silane coupling agents as replacements for chromate treatments was investigated on galvanized steel substrates. In order to understand the influence of deposition parameters on silane film formation, pure zinc substrates were first used as a model for galvanized steel to study the interaction between silane coupling agents and zinc surfaces. The silane films formed on pure zinc substrates from aqueous solutions were characterized by ellipsometry, contact angle measurements, reflection absorption infrared spectroscopy, x-ray photoelectron spectroscopy, and atomic force microscopy. The deposition parameters studied include solution concentration, solution dipping time and pH value of the applied solution. It appears that silane film formation involved a true equilibrium of hydrolysis and condensation reactions in aqueous solutions. It has been found that the silane film thickness obtained depends primarily on the solution concentration and is almost independent of the solution dipping time. The molecular orientation of applied silane films is determined by the pH value of applied silane solutions and the isoelectric point of metal substrates. The deposition window in terms of pH value for zinc substrates is between 6.0 and 9.0. The total surface energy of the silane-coated pure zinc substrates decreases with film aging time, the decrease rate, however, is determined by the nature of silane coupling agents. Selected silane coupling agents were applied as prepaint or passivation treatments onto galvanized steel substrates. The corrosion protection provided by these silane-based treatments were evaluated by salt spray test, cyclic corrosion test, electrochemical impedance spectroscopy, and stack test. The results showed that silane coupling agents can possibly be used to replace chromates for corrosion control of galvanized steel substrates. Silane coatings provided by these silane treatments serve mainly as physical barriers. Factors that affect the performance of a silane coupling agent in the application of corrosion control include chemical reactivity, hydrophobic character, siloxane crosslinker network, and film thickness. Good protections afforded by the silane treatments are a synergetic effect of all these factors.

Kinetic study of alkaline protease 894 for the hydrolysis of the pearl oyster Pinctada martensii

NASA Astrophysics Data System (ADS)

Chen, Xin; Chen, Hua; Cai, Bingna; Liu, Qingqin; Sun, Huili

2013-05-01

A new enzyme (alkaline protease 894) obtained from the marine extremophile Flavobacterium yellowsea (YS-80-122) has exhibited strong substrate-binding and catalytic activity, even at low temperature, but the characteristics of the hydrolysis with this enzyme are still unclear. The pearl oyster Pinctada martensii was used in this study as the raw material to illustrate the kinetic properties of protease 894. After investigating the intrinsic relationship between the degree of hydrolysis and several factors, including initial reaction pH, temperature, substrate concentration, enzyme concentration, and hydrolysis time, the kinetics model was established. This study showed that the optimal conditions for the enzymatic hydrolysis were an initial reaction pH of 5.0, temperature of 30°C, substrate concentration of 10% (w/v), enzyme concentration of 2 500 U/g, and hydrolysis time of 160 min. The kinetic characteristics of the protease for the hydrolysis of P. martensii were obtained. The inactivation constant was found to be 15.16/min, and the average relative error between the derived kinetics model and the actual measurement was only 3.04%, which indicated a high degree of fitness. Therefore, this study provides a basis for the investigation of the concrete kinetic characteristics of the new protease, which has potential applications in the food industry.

Biohydrogen production from lactose: influence of substrate and nitrogen concentration.

PubMed

Moreno, R; Fierro, J; Fernández, C; Cuetos, M J; Gómez, X

2015-01-01

Hydrogen produced from renewable sources may be considered the energy vector of the future. However, reducing process costs is imperative in order to achieve this goal. In the present research, the effect of nitrogen (N), initial pH and substrate content for starting up the dark fermentative process was studied using the response surface methodology. Anaerobic digested dried sludge (biosolid pellets) was used as the inoculum. Synthetic wastewater was used as the substrate in batch reactors. A decrease in H2 production was observed with the increase in N and lactose concentrations. This drop was considerably greater when the concentration of lactose was at its lower level. Although the increase in lactose concentration results in a lower H2 production, the effect of N on the response is attenuated at higher levels of lactose. On the other hand, the effect of initial pH on the fermentation system was not significant. The evaluation on the process under semi-continuous conditions was performed using anaerobic sequencing batch reactors (ASBRs). The process was evaluated at different C/N ratios using synthetic wastewater. Results showed higher hydrogen yields with the gradual decrease in nitrogen content. The addition of cheese whey to the ASBR resulted in a H2 production rate of 0.18 L H2 L(-1) d(-1).

Lignosulfonate and elevated pH can enhance enzymatic saccharification of lignocelluloses

PubMed Central

2013-01-01

Background Nonspecific (nonproductive) binding (adsorption) of cellulase by lignin has been identified as a key barrier to reduce cellulase loading for economical sugar and biofuel production from lignocellulosic biomass. Sulfite Pretreatment to Overcome Recalcitrance of Lignocelluloses (SPORL) is a relatively new process, but demonstrated robust performance for sugar and biofuel production from woody biomass especially softwoods in terms of yields and energy efficiencies. This study demonstrated the role of lignin sulfonation in enhancing enzymatic saccharification of lignocelluloses – lignosulfonate from SPORL can improve enzymatic hydrolysis of lignocelluloses, contrary to the conventional belief that lignin inhibits enzymatic hydrolysis due to nonspecific binding of cellulase. Results The study found that lignosulfonate from SPORL pretreatment and from a commercial source inhibits enzymatic hydrolysis of pure cellulosic substrates at low concentrations due to nonspecific binding of cellulase. Surprisingly, the reduction in enzymatic saccharification efficiency of a lignocellulosic substrate was fully recovered as the concentrations of these two lignosulfonates increased. We hypothesize that lignosulfonate serves as a surfactant to enhance enzymatic hydrolysis at higher concentrations and that this enhancement offsets its inhibitive effect from nonspecific binding of cellulase, when lignosulfonate is applied to lignocellulosic solid substrates. Lignosulfonate can block nonspecific binding of cellulase by bound lignin on the solid substrates, in the same manner as a nonionic surfactant, to significantly enhance enzymatic saccharification. This enhancement is linearly proportional to the amount of lignosulfonate applied which is very important to practical applications. For a SPORL-pretreated lodgepole pine solid, 90% cellulose saccharification was achieved at cellulase loading of 13 FPU/g glucan with the application of its corresponding pretreatment hydrolysate coupled with increasing hydrolysis pH to above 5.5 compared with only 51% for the control run without lignosulfonate at pH 5.0. The pH-induced lignin surface modification at pH 5.5 further reduced nonspecific binding of cellulase by lignosulfonate. Conclusions The results reported in this study suggest significant advantages for SPORL-pretreatment in terms of reducing water usage and enzyme dosage, and simplifying process integration, i.e., it should eliminate washing of SPORL solid fraction for direct simultaneous enzymatic saccharification and combined fermentation of enzymatic and pretreatment hydrolysates (SSCombF). Elevated pH 5.5 or higher, rather than the commonly believed optimal and widely practiced pH 4.8-5.0, should be used in conducting enzymatic saccharification of lignocelluloses. PMID:23356796

Method for plating with metal oxides

DOEpatents

Silver, G.L.; Martin, F.S.

1994-08-23

A method is disclosed of plating hydrous metal oxides on at least one substrate, which method is indifferent to the electrochemical properties of the substrate, and comprises reacting metallic ions in aqueous solution with an appropriate oxidizing agent such as sodium hypochlorite or calcium sulfite with oxygen under suitable conditions of pH and concentration such that oxidation and precipitation of metal oxide are sufficiently slow to allow satisfactory plating of metal oxide on the substrate. 1 fig.

Temperature and substrate chemistry as major drivers of interregional variability of leaf microbial decomposition and cellulolytic activity in headwater streams.

PubMed

Fenoy, Encarnación; Casas, J Jesús; Díaz-López, Manuel; Rubio, Juan; Guil-Guerrero, J Luís; Moyano-López, Francisco J

2016-11-01

Abiotic factors, substrate chemistry and decomposers community composition are primary drivers of leaf litter decomposition. In soil, much of the variation in litter decomposition is explained by climate and substrate chemistry, but with a significant contribution of the specialisation of decomposer communities to degrade specific substrates (home-field advantage, HFA). In streams, however, HFA effects on litter decomposition have not been explicitly tested. We evaluated responses of microbial decomposition and β-glucosidase activity to abiotic factors, substrate and decomposer assemblages, using a reciprocal litter transplant experiment: 'ecosystem type' (mountain vs lowland streams) × 'litter chemistry' (alder vs reed). Temperature, pH and ionic concentration were higher in lowland streams. Decomposition for both species was faster in lowland streams. Decomposition of reed was more accelerated in lowland compared with mountain streams than that of alder, suggesting higher temperature sensitivity of decomposition in reed. Q10 (5°C-15°C) values of β-glucosidase activity were over 2. The alkaline pH and high ionic concentration of lowland streams depleted enzyme activity. We found similar relationships of decomposition or enzyme activity with abiotic factors for both species, suggesting limited support to the HFA hypothesis. Overall, our results suggest a prime role of temperature interacting with substrate chemistry on litter decomposition. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Biochemical characterisation of the esterase activities of wine lactic acid bacteria.

PubMed

Matthews, Angela; Grbin, Paul R; Jiranek, Vladimir

2007-11-01

Esters are an important group of volatile compounds that can contribute to wine flavour. Wine lactic acid bacteria (LAB) have been shown to produce esterases capable of hydrolysing ester substrates. This study aims to characterise the esterase activities of nine LAB strains under important wine conditions, namely, acidic conditions, low temperature (to 10 degrees C) and in the presence of ethanol (2-18% v/v). Esterase substrate specificity was also examined using seven different ester substrates. The bacteria were generally found to have a broad pH activity range, with the majority of strains showing maximum activity close to pH 6.0. Exceptions included an Oenococcus oeni strain that retained most activity even down to a pH of 4.0. Most strains exhibited highest activity across the range 30-40 degrees C. Increasing ethanol concentration stimulated activity in some of the strains. In particular, O. oeni showed an increase in activity up to a maximum ethanol concentration of around 16%. Generally, strains were found to have greater activity towards short-chained esters (C2-C8) compared to long-chained esters (C10-C18). Even though the optimal physicochemical conditions for enzyme activity differed from those found in wine, these findings are of potential importance to oenology because significant activities remained under wine-like conditions.

Irrigation water acidification to neutralize alkalinity for nursery crop production: Substrate pH, electrical conductivity, and nutrient concentrations; and plant nutrition and growth

USDA-ARS?s Scientific Manuscript database

Liming agents (LA) in irrigation water, typically associated with carbonates and bicarbonates of calcium (Ca) and magnesium (Mg), contribute to water alkalinity. Repeated application of LA to container crops can cause media-solution pH to rise overtime, that uncorrected, can lead to a nutrient avail...

[Monolithic column-gold composite substrate preparation and application to SERS detection of pigment].

PubMed

Xie, Yun-Fei; Li, Yan; Yu, Hui; Qian, He; Yao, Wei-Rong

2014-03-01

In the present study, we developed a novel SERS substrate with the porous monolith material combined with classic gold nanoparticles, and erythrosine as the research object, by adjusting the different experimental conditions for optimal SERS enhancements, including system pH and mixing time, and ultimately selected the optimum pH value 5.06 and mixing time 25 min. Compared with the traditional gold plastic substrate enhancement effect, the experimental conditions were applied to the monolith substrate SERS detection of dye erythrosine, different concentrations of samples were used for erythrosine SERS detection, and the detection limit reached 0.1 g x mL(-1). The method uses the payload of gold nanoparticles in mesoporous materials to effectively enhance the SERS signal. And this method has the advantages of simpleness and good stability, which provides a favorable theoretical basis for the rapid prohibited colorings screening.

Enrichment of a mixed microbial culture for polyhydroxyalkanoates production: Effect of pH and N and P concentrations.

PubMed

Montiel-Jarillo, Gabriela; Carrera, Julián; Suárez-Ojeda, María Eugenia

2017-04-01

Polyhydroxyalkanoates (PHA) are biopolymers that can be an alternative against conventional plastics. The study reported herein evaluated the enrichment of a mixed microbial culture (MMC) operated under feast/famine regime and different pHs in a sequencing batch reactor (SBR) using acetate as sole carbon source to produce polyhydroxyalkanoates (PHAs). The enrichment step was evaluated at controlled pH of 7.5 and also without pH control (averaged value of 9.0). The acetate uptake rate (-q S ) of both enrichments at the end of the experimental period exhibited similar behaviour being about 0.18CmolAcCmolX -1 h -1 and 0.19CmolAcCmolX -1 h -1 for SBR-A and SBR-B, respectively. However, the PHA-storing capacity of the biomass enriched without pH control was better, exhibiting a maximum PHA content of 36% (gPHAg -1 VSS) with a PHA production rate (q PHA ) of 0.16CmolPHACmolX -1 h -1 . Batch experiments were performed to evaluate PHA-storing capacity of the enriched culture at different pHs and nutrients concentrations. In the pH experiments (without nutrient limitation), it was found that in the absence of controlled pH, the enriched biomass exhibited a PHA content of 44% gPHAg -1 VSS with -q S and PHA to substrate yield (Y PHA/Ac ) of 0.57CmolAcCmolX -1 h -1 and 0.33CmolPHACmolAc -1 , respectively. Regarding the experiments at variable nutrients concentration (pH ranging 8.8 to 9.2), the results indicate that the PHA content in the enriched biomass is significantly higher being around 51% gPHAg -1 VSS under nitrogen limitation. This work demonstrated the feasibility of the enrichment of a MMC with PHA storage ability without pH control. Results also suggest that better PHAs contents and substrate uptake rates are obtained without controlling the pH in the accumulation step. Finally, this work also highlights the importance of understanding the role of nutrients concentration during the accumulation step. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of citric acid on metals mobility in pruning wastes and biosolids compost and metals uptake in Atriplex halimus and Rosmarinus officinalis.

PubMed

Tapia, Y; Eymar, E; Gárate, A; Masaguer, A

2013-05-01

To assess metal mobility in pruning waste and biosolids compost (pH 6.9 and total concentration of metals in milligram per kilogram of Cd 1.9, Cu 132, Fe 8,513, Mn 192, Pb 81, and Zn 313), shrubs species Atriplex halimus and Rosmarinus officinalis were transplanted in this substrate and irrigated with citric acid (4 g L(-1), pH 2.9) and nutrient solution daily for 60 days. Citric acid significantly increased the concentrations of soluble Mn and Fe in the nutrient substrate solution measured by suction probes, while other metals did not vary in concentration (Cu and Zn) or were not observed at detectable levels (Cd and Pb). In plants, citric acid significantly increased the concentrations of Cu (2.7 ± 0.1-3.3 ± 0.1 mg kg(-1)), Fe (49.2 ± 5.2-76.8 ± 6.8 mg kg(-1)), and Mn (7.2 ± 1.1-11.4 ± 0.7 mg kg(-1)) in leaves of R. officinalis, whereas the concentration of only Mn (25.4 ± 0.3-42.2 ± 2.9 mg kg(-1)) was increased in A. halimus. Increasing Fe and Mn solubility by citric acid addition indicates the possibility of using it to improve plant nutrition. The mobility of metals in this substrate was influenced for the concentration of the metal, the degree of humification of organic matter and its high Fe content.

In vitro fermentation of total mixed diets differing in concentrate proportion: relative effects of inocula and substrates.

PubMed

Serment, Amélie; Giger-Reverdin, Sylvie; Schmidely, Philippe; Dhumez, Ophélie; Broudiscou, Laurent P; Sauvant, Daniel

2016-01-15

In vitro techniques are used to predict ruminant feedstuff values or characterise rumen fermentation. As the results are influenced by several factors, such as the relative effects of inocula and substrates, this study aimed to examine in vitro incubation of two total mixed rations (substrates) differing in their proportion of concentrate [low (L): 350 g kg(-1) vs. high (H): 700 g kg(-1)] incubated in inocula provided by goats fed either a L or a H diet. Gas production and composition in carbon dioxide (CO2), methane (CH4 ) and hydrogen (H2), volatile fatty acids (VFAs), soluble carbohydrates (SCs) and ammonia (NH3) concentrations, and pH of the fermentation fluid were measured. In comparison with the L inoculum and L substrate, the H ones produced more CO2 and CH4 gas, which led to higher SCs and VFA concentrations, and lower acetate-to-propionate ratio and NH3 concentration, with a predominant effect of the inoculum. The effects of the inocula and of the substrates were additive using donor animals adapted to the diets. © 2015 Society of Chemical Industry.

Effect of lactose concentration on batch production of ethanol from cheese whey using Candida pseudotropicalis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghaly, A.E.; El-Taweel, A.A.

1995-07-01

The effect of lactose concentration on growth of Candida pseudotropicalis and ethanol production from cheese whey under batch conditions was investigated. Four initial lactose concentrations ranging from 50 to 200 g/L (5 to 20% wt/vol) were used. High concentration of lactose had an inhibitory effect on the specific growth rate, lactose utilization rate, and ethanol production rate. The maximum cell concentration was influenced by the initial substrate concentration as well as ethanol concentration. Inhibition of ethanol production was more pronounced at higher initial lactose concentrations. The maximum ethanol yield (96.6% of the theoretical yield) was achieved with the 100 g/Lmore » initial substrate concentration. The results indicated that pH control during alcohol fermentation of cheese whey is not necessary. 41 refs., 12 figs., 1 tab.« less

An interfacial and comparative in vitro study of gastrointestinal lipases and Yarrowia lipolytica LIP2 lipase, a candidate for enzyme replacement therapy.

PubMed

Bénarouche, Anaïs; Point, Vanessa; Carrière, Frédéric; Cavalier, Jean-François

2014-07-01

Lipolytic activities of Yarrowia lipolytica LIP2 lipase (YLLIP2), human pancreatic (HPL) and dog gastric (DGL) lipases were first compared using lecithin-stabilized triacylglycerol (TAG) emulsions (Intralipid) at various pH and bile salt concentrations. Like DGL, YLLIP2 was able to hydrolyze TAG droplets covered by a lecithin monolayer, while HPL was not directly active on that substrate. These results were in good agreement with the respective kinetics of adsorption on phosphatidylcholine (PC) monomolecular films of the same three lipases, YLLIP2 being the most tensioactive lipase. YLLIP2 adsorption onto a PC monolayer spread at the air/water interface was influenced by pH-dependent changes in the enzyme/lipid interfacial association constant (KAds) which was optimum at pH 6.0 on long-chain egg PC monolayer, and at pH 5.0 on medium chain dilauroylphosphatidylcholine film. Using substrate monolayers (1,2-dicaprin, trioctanoin), YLLIP2 displayed the highest lipolytic activities on both substrates in the 25-35 mN m(-1) surface pressure range. YLLIP2 was active in a large pH range and displayed a pH-dependent activity profile combining DGL and HPL features at pH values found in the stomach (pH 3-5) and in the intestine (pH 6-7), respectively. The apparent maximum activity of YLLIP2 was observed at acidic pH 4-6 and was therefore well correlated with an efficient interfacial binding at these pH levels, whatever the type of interfaces (Intralipid emulsions, substrate or PC monolayers). All these findings support the use of YLLIP2 in enzyme replacement therapy for the treatment of pancreatic exocrine insufficiency, a pathological situation in which an acidification of intestinal contents occurs. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Rennin--a Neglected Enzyme?

ERIC Educational Resources Information Center

Gill, John; Saunders, Terry

1987-01-01

Presents investigations to explore the substrate specificity, pH, concentration, and temperature relations of an enzyme with only inexpensive commercial rennet and basic laboratory equipment. Describes how the activities were carried out with a group of 15-year-old students. (CW)

Investigating a Bio-Engineered Enzyme.

ERIC Educational Resources Information Center

Bullerwell, Lornie; And Others

1994-01-01

Describes science experiments with the enzyme lactose, which is available commercially as Lactaid and Dairy Ease. Experiments show how the rate of reaction of lactose converted to glucose and galactose is influenced by temperature, pH, and substrate concentration. (PR)

Modelling and optimization of environmental conditions for kefiran production by Lactobacillus kefiranofaciens.

PubMed

Cheirsilp, B; Shimizu, H; Shioya, S

2001-12-01

A mathematical model for kefiran production by Lactobacillus kefiranofaciens was established, in which the effects of pH, substrate and product on cell growth, exopolysaccharide formation and substrate assimilation were considered. The model gave a good representation both of the formation of exopolysaccharides (which are not only attached to cells but also released into the medium) and of the time courses of the production of galactose and glucose in the medium (which are produced and consumed by the cells). Since pH and both lactose and lactic acid concentrations differently affected production and growth activity, the model included the effects of pH and the concentrations of lactose and lactic acid. Based on the mathematical model, an optimal pH profile for the maximum production of kefiran in batch culture was obtained. In this study, a simplified optimization method was developed, in which the optimal pH profile was determined at a particular final fermentation time. This was based on the principle that, at a certain time, switching from the maximum specific growth rate to the critical one (which yields the maximum specific production rate) results in maximum production. Maximum kefiran production was obtained, which was 20% higher than that obtained in the constant-pH control fermentation. A genetic algorithm (GA) was also applied to obtain the optimal pH profile; and it was found that practically the same solution was obtained using the GA.

Formation of ethyl ferulate from feruloylated oligosaccharide by transesterification of rice koji enzyme under sake mash conditions.

PubMed

Suzuki, Nobukazu; Ito, Toshihiko; Hiroshima, Kai; Tokiwano, Tetsuo; Hashizume, Katsumi

2016-03-01

Formation of ethyl ferulate (EF) and ferulic acid (FA) under sake mash conditions was studied using feruloylated oligosaccharide (FO), prepared from rice grains, as the substrate for rice koji enzyme. EF and FA were produced from FO over six times faster than from alkyl ferulates however, under the same ethanol concentration, only small differences were observed between the EF/FA ratios when either FO or methyl ferulate were used as substrates. Esterification and hydrolysis of FO or methyl ferulate showed similar pH dependencies and similar EF/FA ratios for each substrate in all of the pH ranges tested. Ethanol concentration clearly affected the EF/FA ratio; the ratio increased as ethanol concentration increased. Formation of EF and FA in the sake mash simulated rice digest was accelerated by addition of exogenous FO. These results indicated that supply of FO to sake mash is a crucial step for EF and FA formation, and ethanol is an influencing factor in the EF/FA ratio. The rice koji enzyme reaction suggested that EF and FA are formed through a common feruloylated enzyme intermediate complex by transesterification or hydrolysis, and these reactions occur competitively. Copyright © 2015 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Purification of polluted water with spent mushroom (Agaricus bisporus) substrate: from agricultural waste to biosorbent of phenanthrene, Cd and Pb.

PubMed

García-Delgado, C; Alonso-Izquierdo, M; González-Izquierdo, M; Yunta, F; Eymar, E

2017-07-01

The present research was aimed to (i) report the recycling of spent A. bisporus substrate (SAS) to remove heavy metals (Cd and Pb) and phenanthrene (Phe) from polluted water and (ii) assess the possibility to use the treated water for irrigation. Batch experiments were carried out to assess, firstly, the effect of interaction time between pollutants with SAS and, secondly, the pH of the polluted water. Then a biofilter was designed by using pressurized glass columns. Chemical parameters such as pH, electrical conductivity and content of Pb, Cd, Phe, nutrients (NPK) and Cl - were determined. Equilibrium for contaminants was quickly reached (1-2 h). The pH of the polluted water was the key factor for pollutants' adsorption. The polluted water's pH was increased after biofilter interaction. Phe was not detected in any fraction. Pb and Cd sorption rates were higher than 99%. The pollutant concentrations were within the permitted range to be used for agriculture purposes. Purified water showed significant concentrations of NPK, indicating its potential use as fertilizer. The SAS shows potential to be used as Phe, Pb and Cd biosorbent and the resulting treated water can be used for irrigation according to pollutant contents and agronomical evaluation.

Controlled production of Camembert-type cheeses. Part I: Microbiological and physicochemical evolutions.

PubMed

Leclercq-Perlat, Marie-Noëlle; Buono, Frédéric; Lambert, Denis; Latrille, Eric; Spinnler, Henry-Eric; Corrieu, Georges

2004-08-01

A holistic approach of a mould cheese ripening is presented. The objective was to establish relationships between the different microbiological and biochemical changes during cheese ripening. Model cheeses were prepared from pasteurized milk inoculated with Kluyveromyces lactis, Geotrichum candidum, Penicillium camemberti and Brevibacterium linens under aseptic conditions. Two cheese-making trials with efficient control of environmental parameters were carried out and showed similar ripening characteristics. K. lactis grew rapidly between days 1 and 6 (generation time around 48 h). G. candidum grew exponentially between days 4 and 10 (generation time around 4.6 d). Brevi. linens also grew exponentially but after day 6 when Pen. camemberti mycelium began developing and the pH of the rind was close to 7. Its exponential growth presented 3 phases in relation to carbon and nitrogen substrate availability. Concentrations of Pen. camemberti mycelium were not followed by viable cell count but they were evaluated visually. The viable microorganism concentrations were well correlated with the carbon substrate concentrations in the core and in the rind. The lactose concentrations were negligible after 10 d ripening, and changes in lactate quantities were correlated with fungi flora. The pH of the inner part depended on NH3. Surface pH was significantly related to NH3 concentration and to fungi growth. The acid-soluble nitrogen (ASN) and non-protein nitrogen (NPN) indexes and NH3 concentrations of the rind were low until day 6, and then increased rapidly to follow the fungi concentrations until day 45. The ASN and NPN indexes and NH3 concentrations in the core were lower than in the rind and they showed the same evolution. G. candidum and Pen. camemberti populations have a major effect on proteolysis; nevertheless, K. lactis and Brevi. linens cell lysis also had an impact on proteolysis. Viable cell counts of K. lactis, G. candidum, Pen. camemberti and Brevi. linens were correlated with the environmental conditions, with proteolytic products and with carbon substrate assimilation. NH3 diffusion from surface to the cheese core during ripening was highly suspected. Interaction phenomena between microorganisms are discussed.

SPERMINE OXIDASE: AN AMINE OXIDASE WITH SPECIFICITY FOR SPERMINE AND SPERMIDINE

PubMed Central

Hirsch, James G.

1953-01-01

Sheep serum and bovine serum contain an enzyme which brings about a rapid oxidative deamination of certain biological amines. This enzyme differs from previously described amine oxidases in several regards and especially in its substrate specificity. Studies thus far indicate that only spermine and the closely related compound spermidine serve as substrates for the enzyme in sheep serum. For this reason, the enzyme has been named spermine oxidase. Spermine oxidase is active in a variety of fluids of various ionic strength and buffer composition. The reaction takes place between pH 6.0 and pH 8.0 with an optimal rate in the vicinity of neutrality. Under certain conditions, the rate of oxygen consumption during the initial phase of the reaction is independent of the concentration of substrate. The diminution in rate observed during the latter phase of the enzymatic attack appears to be due to an alteration in the kinetics at low concentrations of substrate, or to competitive inhibition by a product of the reaction. Carbonyl reagents almost completely block the action of spermine oxidase, while certain amines and the cyanide ion bring about partial inhibition. Thiol reagents and sequestering compounds do not alter the course of the oxidative process. In the presence of low concentrations of mercuric chloride, the sheep serum-spermine system consumes approximately twice as much oxygen as controls containing no mercuric ion. The mechanism by which the mercuric ion stimulates additional oxygen uptake is obscure. PMID:13052805

Effects of the acid-tolerant engineered bacterial strain Megasphaera elsdenii H6F32 on ruminal pH and the lactic acid concentration of simulated rumen acidosis in vitro.

PubMed

Long, M; Feng, W J; Li, P; Zhang, Y; He, R X; Yu, L H; He, J B; Jing, W Y; Li, Y M; Wang, Z; Liu, G W

2014-02-01

The aim of this study was to examine the effects of the acid-tolerant engineered bacterial strain Megasphaera elsdenii H6F32 (M. elsdenii H6F32) on ruminal pH and the lactic acid concentrations in simulated rumen acidosis conditions in vitro. A mixed culture of ruminal bacteria, buffer, and primarily degradable substrates was inoculated with equal numbers of M. elsdenii H6 or M. elsdenii H6F32. The pH and lactic acid concentrations in the mixed culture were determined at 0, 2, 4, 6, 8, 10, 12, 14, 16, and 18 h of incubation. Acid-tolerant M. elsdenii H6F32 reduced the accumulation of lactic acid and increased the pH value. These results indicate that acid-tolerant M. elsdenii H6F32 could be a potential candidate for preventing rumen acidosis. Copyright © 2013 Elsevier Ltd. All rights reserved.

How gastric lipase, an interfacial enzyme with a Ser-His-Asp catalytic triad, acts optimally at acidic pH.

PubMed

Chahinian, Henri; Snabe, Torben; Attias, Coralie; Fojan, Peter; Petersen, Steffen B; Carrière, Frédéric

2006-01-24

Gastric lipase is active under acidic conditions and shows optimum activity on insoluble triglycerides at pH 4. The present results show that gastric lipase also acts in solution on vinyl butyrate, with an optimum activity above pH 7, which suggests that gastric lipase is able to hydrolyze ester bonds via the classical mechanism of serine hydrolases. These results support previous structural studies in which the catalytic triad of gastric lipase was reported to show no specific features. The optimum activity of gastric lipase shifted toward lower pH values, however, when the vinyl butyrate concentration was greater than the solubility limit. Experiments performed with long-chain triglycerides showed that gastric lipase binds optimally to the oil-water interface at low pH values. To study the effects of the pH on the adsorption step independently from substrate hydrolysis, gastric lipase adsorption on solid hydrophobic surfaces was monitored by total internal reflection fluorescence (TIRF), as well as using a quartz crystal microbalance. Both techniques showed a pH-dependent reversible gastric lipase adsorption process, which was optimum at pH 5 (Kd = 6.5 nM). Lipase adsorption and desorption constants (ka = 147,860 M(-1) s(-1) and kd = 139 x 10(-4) s(-1) at pH 6) were estimated from TIRF experiments. These results indicate that the optimum activity of gastric lipase at acidic pH is only "apparent" and results from the fact that lipase adsorption at lipid-water interfaces is the pH-dependent limiting step in the overall process of insoluble substrate hydrolysis. This specific kinetic feature of interfacial enzymology should be taken into account when studying any soluble enzyme acting on an insoluble substrate.

Anaerobic monodigestion of poultry manure: determination of operational parameters for CSTR.

PubMed

Chamy, R; León, C; Vivanco, E; Poirrier, P; Ramos, C

2012-01-01

In this work the anaerobic monodigestion for the treatment of turkey manure was evaluated, without its codigestion with another substrate. The effect of the organic loading rate (OLR) and the substrate concentration (high total solids (TS) concentration) or product concentration (high volatile fatty acids (VFA) and/or ammonia (NH(3)-N) concentrations) was studied. The results show that for a continuous stirred tank reactor (CSTR) operation, a maximum of 40 g/L of TS and 4.0 g/L of ammonium (NH(4)(+)) was required. In addition, the maximum organic loading rate (OLR) will not exceed 1.5 kg VS/m(3)d. Higher TS and NH(4)(+) concentrations and OLR lead to a reduction on the methane productivity and volatile solids (VS) removal. During the CSTR operation, a high alkalinity concentration (above 10 g/L CaCO(3)) was found; this situation allowed maintaining a constant and appropriate pH (close to 7.8), despite the VFA accumulation. In this sense, the alkalinity ratio (α) is a more appropriate control and monitoring parameter of the reactor operation compared to pH. Additionally, with this parameter a VS removal of 80% with a methane productivity of 0.50 m(3)(CH4)/m(3)(R)d is achieved.

Conversion of woody biomass into fermentable sugars by cellulase from Agaricus arvensis.

PubMed

Jeya, Marimuthu; Nguyen, Ngoc-Phuong-Thao; Moon, Hee-Jung; Kim, Sang-Hwan; Lee, Jung-Kul

2010-11-01

Agaricus arvensis, a newly isolated basidiomycetous fungus, was found to secrete efficient cellulases. The strain produced the highest endoglucanase (EG), cellobiohydrolase (CBH) and beta-glucosidase (BGL) activities of 0.3, 3.2 and 8U/mg-protein, respectively, with rice straw as the carbon source. Saccharification of the woody biomass with A. arvensis cellulase as the enzyme source released a high level of fermentable sugars. Enzymatic hydrolysis of the poplar biomass was optimized using the response surface methodology in order to study the influence of the variables (pH, temperature, cellulases concentration and substrate concentration). The enzyme and substrate concentrations were identified as the limiting factors for the saccharification of poplar wood biomass. A total reducing sugar level of 29g/L (293mg/g-substrate) was obtained at an enzyme concentration of 65FPU/g-substrate after optimization of the hydrolysis parameters. The model validation showed a good agreement between the experimental results and the predicted responses. A. arvensis could be a good candidate for the production of reducing sugars from a cellulosic biomass.

Inorganic Carbon Source for Photosynthesis in the Seagrass Thalassia hemprichii (Ehrenb.) Aschers.

PubMed

Abel, K M

1984-11-01

Photosynthetic carbon uptake of the tropical seagrass Thalassia hemprichii (Ehrenb.) Aschers was studied by several methods. Photosynthesis in buffered seawater in media in the range of pH 6 to pH 9 showed an exponentially increasing rate with decreasing pH, thus indicating that free CO(2) was a photosynthetic substrate. However, these experiments were unable to determine whether photosynthesis at alkaline pH also contained some component due to HCO(3) (-) uptake. This aspect was further investigated by studying photosynthetic rates in a number of media of varying pH (7.8-8.61) and total inorganic carbon (0.75-13.17 millimolar). In these media, photosynthetic rate was correlated with free CO(2) concentration and was independent of the HCO(3) (-) concentration in the medium. Short time-course experiments were conducted during equilibration of free CO(2) and HCO(3) (-) after injection of (14)C labeled solution at acid or alkaline pH. High initial photosynthetic rates were observed when acidic solutions (largely free CO(2)) were used but not with alkaline solutions. The concentration of free CO(2) was found to be a limiting factor for photosynthesis in this plant.

pH and generation dependent morphologies of PAMAM dendrimers on a graphene substrate.

PubMed

Gosika, Mounika; Maiti, Prabal K

2018-03-07

The adsorption of PAMAM dendrimers at solid/water interfaces has been extensively studied, and is mainly driven by electrostatic and van der Waals interactions between the substrate and the dendrimers. However, the pH dependence of the adsorption driven predominantly by the van der Waals interactions is poorly explored, although it is crucial for investigating the potentiality of these dendrimers in supercapacitors and surface patterning. Motivated by this aspect, we have studied the adsorption behavior of PAMAM dendrimers of generations 2 (G2) to 5 (G5) with pH and salt concentration variation, on a charge neutral graphene substrate, using fully atomistic molecular dynamics simulations. The instantaneous snapshots from our simulations illustrate that the dendrimers deform significantly from their bulk structures. Based on various structural property calculations, we classify the adsorbed dendrimer morphologies into five categories and map them to a phase diagram. Interestingly, the morphologies we report here have striking analogies with those reported in star-polymer adsorption studies. From the fractional contacts and other structural property analyses we find that the deformations are more pronounced at neutral pH as compared to high and low pH. Higher generation dendrimers resist deformation following the deformation trend, G2 > G3 > G4 > G5 at any given pH level. As the adsorption here is mainly driven by van der Waals interactions, we observe no desorption of the dendrimers as the salt molarity is increased, unlike that reported in the electrostatically driven adsorption studies.

Identification of lipolytic enzymes isolated from bacteria indigenous to Eucalyptus wood species for application in the pulping industry.

PubMed

Ramnath, L; Sithole, B; Govinden, R

2017-09-01

This study highlights the importance of determining substrate specificity at variable experimental conditions. Lipases and esterases were isolated from microorganisms cultivated from Eucalyptus wood species and then concentrated (cellulases removed) and characterized. Phenol red agar plates supplemented with 1% olive oil or tributyrin was ascertained to be the most favourable method of screening for lipolytic activity. Lipolytic activity of the various enzymes were highest at 45-61 U/ml at the optimum temperature and pH of between at 30-35 °C and pH 4-5, respectively. Change in pH influenced the substrate specificity of the enzymes tested. The majority of enzymes tested displayed a propensity for longer aliphatic acyl chains such as dodecanoate (C 12 ), myristate (C 14 ), palmitate (C 16 ) and stearate (C 18 ) indicating that they could be characterised as potential lipases. Prospective esterases were also detected with specificity towards acetate (C 2 ), butyrate (C 4 ) and valerate (C 5 ). Enzymes maintained up to 95% activity at the optimal pH and temperature for 2-3 h. It is essential to test substrates at various pH and temperature when determining optimum activity of lipolytic enzymes, a method rarely employed. The stability of the enzymes at acidic pH and moderate temperatures makes them excellent candidates for application in the treatment of pitch during acid bi-sulphite pulping, which would greatly benefit the pulp and paper industry.

Geochemical controls on lead concentrations in stream water and sediments

USGS Publications Warehouse

Hem, J.D.

1976-01-01

The equilibrium distribution of lead in solution and adsorbed on cation exchange sites in sediment theoretically may be calculated from equations representing selectivities of substrate for lead over H+, Ca2+ and Na+, and the stabilities of lead solute species. Such calculations include consideration of total concentrations of major ions, cation exchange capacity (CEC) of substrate, and pH, at values expected in various natural systems. Measurements of CEC and selectivity coefficients were made for synthetic halloysite, a finely divided amorphous 1:1 clay prepared by precipitation from a mixture of solutions of aluminum and silica. Where suspended sediment having the same properties is present in concentrations of 10-1,000 mg/1 at pH 6-8, more than 90% of the lead present can be adsorbed on sediment surfaces. The cation exchange behavior of lead and other minor cationic species in natural systems could be predicted by this type of model if enough other supporting information were available. Information of the type needed describing natural stream sediments, however, is presently inadequate for accurate predictions. ?? 1976.

Production of ethanol and arabitol by Debaryomyces nepalensis: influence of process parameters

PubMed Central

2013-01-01

Debaryomyces nepalensis, osmotolerant yeast isolated from rotten apple, is known to utilize both hexoses and pentoses and produce industrially important metabolites like ethanol, xylitol and arabitol. In the present study, the effect of different growth substrates, trace elements, nitrogen concentration and initial pH on growth and formation of ethanol and arabitol were examined. Optimum conditions for maximizing the product yields were established: glucose as carbon source, an initial pH of 6.0, 6 g/L of ammonium sulphate and addition of micronutrients. Under these best suited conditions, a concentration of 11g/L of arabitol and 19 g/L of ethanol was obtained in shake flask fermentations. The fermentation was scaled up to 2.5 L bioreactor and the influence of aeration, agitation and initial substrate concentration was also determined. Under optimal conditions (150 g/L glucose, 400 rpm and 0.5 vvm) ethanol concentration reached 52 g/L, which corresponds to a yield of 0.34 g/g and volumetric productivity of 0.28 g/L/h, whereas arabitol production reached a maximum of 14 g/L with a yield and volumetric productivity of 0.1 g/g and 0.07 g/L/h respectively. PMID:23659479

Supplementation of banana flower powder pellet and plant oil sources on in vitro ruminal fermentation, digestibility, and methane production.

PubMed

Kang, Sungchhang; Wanapat, Metha; Viennasay, Bounnaxay

2016-12-01

The objective of this study was to evaluate the effects of banana flower power pellet (BAFLOP-pellet) and plant oil source on in vitro gas production, fermentation efficiency, and methane (CH 4 ) production. Rumen fluid was collected from two rumen-fistulated dairy steers fed on rice straw-based diet with concentrate supplement to maintain normal rumen ecology. All supplemented feed were added to respective treatments in the 30:70 roughage to concentrate-based substrate. The treatments were arranged according to a 3 × 3 factorial arrangement in a completely randomized design. First factor was different levels of BAFLOP-pellet supplementation (0, 30, and 60 g/kg of dietary substrate) and second factor was plant oil source supplementation [non-supplemented, 20 g/kg krabok seed oil (KSO), and 20 g/kg coconut oil (CO) of dietary substrate, respectively]. Under this investigation, BAFLOP-pellet supplementation increased gas production kinetics and in vitro digestibility (P < 0.05). Ruminal pH was dropped post incubation time in the non-supplemented group but was enhanced in BAFLOP-pellet-supplemented treatments. On the other hand, supplementation of KSO and CO depressed gas production and digestibility, but did not influence ruminal pH. In addition, protozoal population and CH 4 production were decreased by BAFLOP-pellet and plant oil addition (P < 0.05). Based on this study, it could be concluded that supplementation of BAFLOP-pellet and plant oil source could enhance the in vitro fermentation efficiency while reduced protozoal population and CH 4 production. It is suggested that BAFLOP-pellet (60 g/kg of dietary substrate) and KSO/CO (20 g/kg of dietary substrate) could be used to manipulate rumen fermentation characteristics fed on high-concentrate diet.

Kinetics of thermophilic anaerobes in fixed-bed reactors.

PubMed

Perez, M; Romero, L I; Sales, D

2001-08-01

The main objective of this study is to estimate growth kinetic constants and the concentration of "active" attached biomass in two anaerobic thermophilic reactors which contain different initial sizes of immobilized anaerobic mixed cultures and decompose distillery wastewater. This paper studies the substrate decomposition in two lab-scale fixed-bed reactors operating at batch conditions with corrugated tubes as support media. It can be demonstrated that high micro-organisms-substrate ratios favor the degradation activity of the different anaerobic cultures, allowing the stable operation without lag-phases and giving better quality in effluent. The kinetic parameters obtained--maximum specific growth rates (mu(max)), non-biodegradable substrate (S(NB)) and "active or viable biomass" concentrations (X(V0))--were obtained by applying the Romero kinetic model [L.I. Romero, 1991. Desarrollo de un modelo matemático general para los procesos fermentativos, Cinética de la degradación anaerobia, Ph.D. Thesis, University of Cádiz (Spain), Serv. Pub. Univ. Cádiz], with COD as substrate and methane (CH4) as the main product of the anaerobic process. This method is suitable to calculate and to differentiate the main kinetic parameters of both the total anaerobic mixed culture and the methanogenic population. Comparison of experimental measured concentration of volatile attached solids (VS(att)) in both reactors with the estimated "active" biomass concentrations obtained by applying Romero kinetic model [L.I. Romero, 1991. Desarrollo de un modelo matemático general para los procesos fermentativos, Cinética de la degradación anaerobia, Ph.D. Thesis, University of Cádiz (Spain), Serv. Pub. Univ. Cádiz] shows that a large amount of inert matter is present in the fixed-bed reactor.

Effect of substrate concentration on hydrogen production by photo-fermentation in the pilot-scale baffled bioreactor.

PubMed

Lu, Chaoyang; Zhang, Zhiping; Zhou, Xuehua; Hu, Jianjun; Ge, Xumeng; Xia, Chenxi; Zhao, Jia; Wang, Yi; Jing, Yanyan; Li, Yameng; Zhang, Quanguo

2018-01-01

Effect of substrate concentration on photo-fermentative hydrogen production was studied with a self-designed 4m 3 pilot-scale baffled photo-fermentative hydrogen production reactor (BPHR). The relationships between parameters, such as hydrogen production rate (HPR, mol H 2 /m 3 /d), hydrogen concentration, pH value, oxidation-reduction potential, biomass concentration (volatile suspended solids, VSS) and reducing sugar concentration, during the photo-fermentative hydrogen production process were investigated. The highest HPR of 202.64±8.83mol/m 3 /d was achieved in chamber #3 at a substrate concentration of 20g/L. Hydrogen contents were in the range of 42.19±0.94%-49.71±0.27%. HPR increased when organic loading rate was increased from 3.3 to 20g/L/d, then decreased when organic loading rate was further increased to 25g/L/d. A maximum HPR of 148.65±4.19mol/m 3 /d was obtained when organic loading rate was maintained at 20g/L/d during continuous bio-hydrogen production. Copyright © 2017 Elsevier Ltd. All rights reserved.

Coupled biotic-abiotic oxidation of organic matter by biogenic MnO_{2}

NASA Astrophysics Data System (ADS)

Gonzalez, Julia; Peña, Jasquelin

2016-04-01

Some reactive soil minerals are strongly implicated in stabilising organic matter. However, others can play an active role in the oxidation of organic molecules. In natural systems, layer-type manganese oxide minerals (MnO2) typically occur as biomineral assemblages consisting of mineral particles and microbial biomass. Both the mineral and biological fractions of the assemblage can be powerful oxidants of organic C. The biological compartment relies on a set of enzymes to drive oxidative transformations of reduced C-substrates, whereas MnO2 minerals are strong, less specific abiotic oxidants that are assumed to rely on interfacial interactions between C-substrates and the mineral surface. This project aims to understand the coupling between microbial C mineralization and abiotic C oxidation mediated by MnO2 in bacterial-MnO2 assemblages. Specifically, under conditions of high C turnover, microbial respiration can significantly alter local pH, dissolved oxygen and pool of available reductants, which may modify rates and mechanism of C oxidation by biotic and abiotic components. We first investigated changes in the solution chemistry of Pseudomonas putida suspensions exposed to varying concentrations of glucose, chosen to represent readily bioavailable substrates in soils. Glucose concentrations tested ranged between 0 and 5.5mM and changes in pH, dissolved oxygen and dissolved organic and inorganic carbon were tracked over 48h. We then combined literature review and wet-chemical experiments to compile the pH dependence of rates of organic substrate oxidation by MnO2, including glucose. Our results demonstrate a strong pH dependence for these abiotic reactions. In assemblages of P. putida - MnO2, kinetic limitations for abiotic C oxidation by MnO2 are overcome by changes in biogeochemical conditions that result from bacterial C metabolism. When extrapolated to a soil solution confronted to an input of fresh dissolved organic matter, bacterial C metabolism of the labile fraction may lower solution pH into a regime that favours abiotic oxidation of recalcitrant C by MnO2. This project demonstrates that the co-occurrence of mineral particles with metabolically active cells provides a direct link between the C and Mn cycles.

Mechanism of papain-catalyzed synthesis of oligo-tyrosine peptides.

PubMed

Mitsuhashi, Jun; Nakayama, Tsutomu; Narai-Kanayama, Asako

2015-01-01

Di-, tri-, and tetra-tyrosine peptides with angiotensin I-converting enzyme inhibitory activity were synthesized by papain-catalyzed polymerization of L-tyrosine ethyl ester in aqueous media at 30 °C. Varying the reaction pH from 6.0 to 7.5 and the initial concentration of the ester substrate from 25 to 100 mM, the highest yield of oligo-tyrosine peptides (79% on a substrate basis) was produced at pH 6.5 and 75 mM, respectively. In the reaction initiated with 100 mM of the substrate, approx. 50% yield of insoluble, highly polymerized peptides accumulated. At less than 15 mM, the reaction proceeded poorly; however, from 30 mM to 120 mM a dose-dependent increase in the consumption rate of the substrate was observed with a sigmoidal curve. Meanwhile, each of the tri- and tetra-tyrosine peptides, even at approx. 5mM, was consumed effectively by papain but was not elongated to insoluble polymers. For deacylation of the acyl-papain intermediate through which a new peptide bond is made, L-tyrosine ethyl ester, even at 5mM, showed higher nucleophilic activity than di- and tri-tyrosine. These results indicate that the mechanism through which papain polymerizes L-tyrosine ethyl ester is as follows: the first interaction between papain and the ester substrate is a rate-limiting step; oligo-tyrosine peptides produced early in the reaction period are preferentially used as acyl donors, while the initial ester substrate strongly contributes as a nucleophile to the elongation of the peptide product; and the balance between hydrolytic fragmentation and further elongation of oligo-tyrosine peptides is dependent on the surrounding concentration of the ester substrate. Copyright © 2015 Elsevier Inc. All rights reserved.

Maize Root Phytase (Purification, Characterization, and Localization of Enzyme Activity and Its Putative Substrate).

PubMed Central

Hubel, F.; Beck, E.

1996-01-01

Three phytase (EC 3.1.3.26) isoforms from the roots of 8-d-old maize (Zea mays L. var Consul) seedlings were separated from phosphatases and purified to near homogeneity. The molecular mass of the native protein was 71 kD, and the isoelectric points of the three isoforms were pH 5.0, 4.9, and 4.8. Each of the three isoforms consisted of two subunits with a molecular mass of 38 kD. The temperature and pH optima (40[deg]C, pH 5.0) of these three isoforms, as well as the apparent Michaelis constants for sodium inositol hexakisphosphate (phytate) (43, 25, and 24 [mu]M) as determined by the release of inorganic phosphate, were only slightly different. Phytate concentrations higher than 300 [mu]M were inhibitory to all three isoforms. In contrast, the dephosphorylation of 4-nitrophenyl phosphate was not inhibited by any substrate concentration, but the Michaelis constants for this substrate were considerably higher (137-157 [mu]M). Hydrolysis of phytate by the phytase isoforms is a nonrandom reaction. D/L-Inositol-1,2,3,4,5- pentakisphosphate was identified as the first and D/L-inositol-1,2,5,6-tetrakisphosphate as the second intermediate in phytate hydrolysis. Phytase activity was localized in root slices. Although phosphatase activity was present in the stele and the cortex of the primary root, phytase activity was confined to the endodermis. Phytate was identified as the putative native substrate in maize roots (45 [mu]g P g-1 dry matter). It was readily labeled upon supplying [32P]phosphate to the roots. PMID:12226456

AFM study of adsorption of protein A on a poly(dimethylsiloxane) surface

NASA Astrophysics Data System (ADS)

Yu, Ling; Lu, Zhisong; Gan, Ye; Liu, Yingshuai; Li, Chang Ming

2009-07-01

In this paper, the morphology and kinetics of adsorption of protein A on a PDMS surface is studied by AFM. The results of effects of pH, protein concentration and contact time of the adsorption reveal that the morphology of adsorbed protein A is significantly affected by pH and adsorbed surface concentration, in which the pH away from the isoelectric point (IEP) of protein A could produce electrical repulsion to change the protein conformation, while the high adsorbed surface protein volume results in molecular networks. Protein A can form an adsorbed protein film on PDMS with a maximum volume of 2.45 × 10-3 µm3. This work enhances our fundamental understanding of protein A adsorption on PDMS, a frequently used substrate component in miniaturized immunoassay devices.

Citric Acid Production by Aspergillus niger Cultivated on Parkia biglobosa Fruit Pulp

PubMed Central

Abidoye, Khadijat Toyin; Tahir, Hauwa; Ibrahim, Aliyu Dabai; Aransiola, Sesan Abiodun

2014-01-01

The study was conducted to investigate the potential of Parkia biglobosa fruit pulp as substrate for citric acid production by Aspergillus niger. Reducing sugar was estimated by 3,5-dinitrosalicylic acid and citric acid was estimated spectrophotometrically using pyridine-acetic anhydride methods. The studies revealed that production parameters (pH, inoculum size, substrate concentration, incubation temperature, and fermentation period) had profound effect on the amount of citric acid produced. The maximum yield was obtained at the pH of 2 with citric acid of 1.15 g/L and reducing sugar content of 0.541 mMol−1, 3% vegetative inoculum size with citric acid yield of 0.53 g/L and reducing sugar content of 8.87 mMol−1, 2% of the substrate concentration with citric acid yield of 0.83 g/L and reducing sugar content of 9.36 mMol−1, incubation temperature of 55°C with citric acid yield of 0.62 g/L and reducing sugar content of 8.37 mMol−1, and fermentation period of 5 days with citric acid yield of 0.61 g/L and reducing sugar content of 3.70 mMol−1. The results of this study are encouraging and suggest that Parkia biglobosa pulp can be harnessed at low concentration for large scale citric acid production. PMID:27433535

Regulatory properties of 6-phosphofructokinase and control of glycolysis in boar spermatozoa.

PubMed

Kamp, G; Schmidt, H; Stypa, H; Feiden, S; Mahling, C; Wegener, G

2007-01-01

Glycolysis is crucial for sperm functions (motility and fertilization), but how this pathway is regulated in spermatozoa is not clear. This prompted to study the location and the regulatory properties of 6-phosphofructokinase (PFK, EC 2.7.1.11), the most important element for control of glycolytic flux. Unlike some other glycolytic enzymes, PFK showed no tight binding to sperm structures. It could readily be extracted from ejaculated boar spermatozoa by sonication and was then chromatographically purified. At physiological pH, the enzyme was allosterically inhibited by near-physiological concentrations of its co-substrate ATP, which induced co-operativity, i.e. reduced the affinity for the substrate fructose 6-phosphate. Inhibition by ATP was reinforced by citrate and H+. Above pH 8, PFK lost all its regulatory properties and showed maximum activity. However, in the physiological pH range, PFK activity was very sensitive to small changes in effectors. At near-physiological substrate concentrations, PFK activity requires activators (de-inhibitors) of which the combination of AMP and fructose 2,6-bisphosphate (F2,6P2) was most efficient as a result of synergistic effects. The kinetics of PFK suggest AMP, F2,6P2, H+, and citrate as allosteric effectors controlling PFK activity in boar spermatozoa. Using immunogold labeling, PFK was localized in the mid-piece and principal piece of the flagellum as well as in the acrosomal area at the top of the head and in the cytoplasmic droplets released from the mid-piece after ejaculation.

Peptide hydrogelation triggered by enzymatic induced pH switch

NASA Astrophysics Data System (ADS)

Cheng, Wei; Li, Ying

2016-07-01

It remains challenging to develop methods that can precisely control the self-assembling kinetics and thermodynamics of peptide hydrogelators to achieve hydrogels with optimal properties. Here we report the hydrogelation of peptide hydrogelators by an enzymatically induced pH switch, which involves the combination of glucose oxidase and catalase with D-glucose as the substrate, in which both the gelation kinetics and thermodynamics can be controlled by the concentrations of D-glucose. This novel hydrogelation method could result in hydrogels with higher mechanical stability and lower hydrogelation concentrations. We further illustrate the application of this hydrogelation method to differentiate different D-glucose levels.

Continuous operation of thermophilic food waste digestion with side-stream ammonia stripping.

PubMed

Zhang, Wei; Heaven, Sonia; Banks, Charles J

2017-11-01

Digesters fed on food waste (high nitrogen content) were operated successfully over an extended period using sidestream biogas stripping to control total ammonia nitrogen (TAN) below inhibitory concentrations. This is the first time biogas stripping has been used to achieve stable thermophilic operation with undiluted substrate of this type. Stripping columns operated batch-wise treated the equivalent of 1.7-4.1% of digester contents daily at pH >10 and 70°C, with no detrimental effect on digestion. TKN removal was 54%, with potential to recover 3.5kgNtonne -1 substrate. When stripping was stopped in one digester TAN increased, accompanied by rising propionic acid concentrations with progressive instability observed from 2.5gNL -1 . Eventual failure as TAN approached 5gNL -1 was due to rapid acetic acid accumulation, resulting in a fall in pH to below 6.5. The pattern of VFA accumulation indicated failure of both acetoclastic methanogenesis and acetate oxidation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Chloroplast Phosphofructokinase

PubMed Central

Kelly, Grahame J.; Latzko, Erwin

1977-01-01

Chloroplast phosphofructokinase from spinach (Spinacia oleracea L.) was purified approximately 40-fold by a combination of fractionations with ammonium sulfate and acetone followed by chromatography on DEAE-Sephadex A-50. Positive cooperative kinetics was observed for the interaction between the enzyme and the substrate fructose 6-phosphate. The optimum pH shifted from 7.7 toward 7.0 as the fructose 6-phosphate concentration was taken below 0.5 mm. The second substrate was MgATP2− (Michaelis constant 30 μm). Free ATP inhibited the enzyme. Chloroplast phosphofructokinase was sensitive to inhibition by low concentration of phosphoenolpyruvate and glycolate 2-phosphate (especially at higher pH); these compounds inhibited in a positively cooperative fashion. Inhibitions by glycerate 2-phosphate (and probably glycerate 3-phosphate), citrate, and inorganic phosphate were also recorded; however, inorganic phosphate effectively relieved the inhibitions by phosphoenolpyruvate and glycolate 2-phosphate. These regulatory properties are considered to complement those of ADP-glucose pyrophosphorylase and fructosebisphosphatase in the regulation of chloroplast starch metabolism. PMID:16660079

Using an artificial neural network to predict the optimal conditions for enzymatic hydrolysis of apple pomace.

PubMed

Gama, Repson; Van Dyk, J Susan; Burton, Mike H; Pletschke, Brett I

2017-06-01

The enzymatic degradation of lignocellulosic biomass such as apple pomace is a complex process influenced by a number of hydrolysis conditions. Predicting optimal conditions, including enzyme and substrate concentration, temperature and pH can improve conversion efficiency. In this study, the production of sugar monomers from apple pomace using commercial enzyme preparations, Celluclast 1.5L, Viscozyme L and Novozyme 188 was investigated. A limited number of experiments were carried out and then analysed using an artificial neural network (ANN) to model the enzymatic hydrolysis process. The ANN was used to simulate the enzymatic hydrolysis process for a range of input variables and the optimal conditions were successfully selected as was indicated by the R 2 value of 0.99 and a small MSE value. The inputs for the ANN were substrate loading, enzyme loading, temperature, initial pH and a combination of these parameters, while release profiles of glucose and reducing sugars were the outputs. Enzyme loadings of 0.5 and 0.2 mg/g substrate and a substrate loading of 30% were optimal for glucose and reducing sugar release from apple pomace, respectively, resulting in concentrations of 6.5 g/L glucose and 28.9 g/L reducing sugars. Apple pomace hydrolysis can be successfully carried out based on the predicted optimal conditions from the ANN.

Crystal structures of different substrates of bacteriorhodopsin's M intermediate at various pH levels.

PubMed

Yamamoto, Masataka; Hayakawa, Naoki; Murakami, Midori; Kouyama, Tsutomu

2009-10-30

The hexagonal P622 crystal of bacteriorhodopsin, which is made up of stacked membranes, is stable provided that the precipitant concentration in the soaking solution is higher than a critical value (i.e., 1.5 M ammonium sulfate). Diffraction data showed that the crystal lattice shrank linearly with increasing precipitant concentration, due primarily to narrowing of intermembrane spaces. Although the crystal shrinkage did not affect the rate of formation of the photoreaction M intermediate, its lifetime increased exponentially with the precipitant concentration. It was suggested that the energetic barrier of the M-to-N transition becomes higher when the motional freedom of the EF loop is reduced by crystal lattice force. As a result of this property, the M state accumulated predominantly when the crystal that was soaked at a high precipitant concentration was illuminated at room temperature. Structural data obtained at various pH levels showed that the overall structure of M is not strongly dependent on pH, except that Glu194 and Glu204 in the proton release complex are more separated at pH 7 than at pH 4.4. This result suggests that light-induced disruption of the paired structure of Glu194 and Glu204 is incomplete when external pH is lower than the pK(a) value of the proton release group in the M state.

Growth strategies to control tapering in Ge nanowires

NASA Astrophysics Data System (ADS)

Periwal, P.; Baron, T.; Gentile, P.; Salem, B.; Bassani, F.

2014-04-01

We report the effect of PH3 on the morphology of Au catalyzed Ge nanowires (NWs). Ge NWs were grown on Si (111) substrate at 400 °C in the presence of PH3, using vapor-liquid-solid method by chemical vapor deposition. We show that high PH3/GeH4 ratio causes passivation at NW surface. At high PH3 concentration phosphorous atoms attach itself on NW surface and form a self-protection coating that prevents conformal growth and leads to taper free nanostructures. However, in case of low PH3 flux the combination of axial and radial growth mechanism occurs resulting in conical structure. We have also investigated axial PH3-intrinsic junctions in Ge NWs. The unusual NW shape is attributed to a combination of catalyzed, uncatalyzed and diffusion induced growth.

A biologically inspired variable-pH strategy for enhancing short-chain fatty acids (SCFAs) accumulation in maize straw fermentation.

PubMed

Meng, Yao; Mumme, Jan; Xu, Heng; Wang, Kaijun

2016-02-01

This study investigates the feasibility of varying the pH to enhance the accumulation of short-chain fatty acids (SCFAs) in the in vitro fermentation of maize straw. The corresponding hydrolysis rate and the net SCFA yield increased as inoculum ratio (VSinoculum/VSsubstrate) increased from 0.09 to 0.79. The pH were maintained at 5.3, 5.8, 6.3, 6.8, 7.3, and 7.8, respectively. A neutral pH of approximately 6.8 was optimal for hydrolysis. The net SCFA yield decreased by 34.9% for a pH of less than 5.8, but remained constant at approximately 721±5mg/gvs for a pH between 5.8 and 7.8. In addition, results were obtained for variable and constant pH levels at initial substrate concentrations of 10, 30 and 50g/L. A variable pH increased the net SCFA yield by 23.6%, 29.0%, and 36.6% for concentrations of 10, 30 and 50g/L. Therefore, a variable pH enhanced SCFA accumulation in maize straw fermentation. Copyright © 2015 Elsevier Ltd. All rights reserved.

A Sensitive Microplate Assay for Lipase Activity Measurement Using Olive Oil Emulsion Substrate: Modification of the Copper Soap Colorimetric Method.

PubMed

Mustafa, Ahmad; Karmali, Amin; Abdelmoez, Wael

2016-01-01

The present work involves a sensitive high-throughput microtiter plate based colorimetric assay for estimating lipase activity using cupric acetate pyridine reagent (CAPR). In the first approach, three factors two levels factorial design methodology was used to evaluate the interactive effect of different parameters on the sensitivity of the assay method. The optimization study revealed that the optimum CAPR concentration was 7.5% w/v, the optimum solvent was heptane and the optimum CAPR pH was 6. In the second approach, the optimized colorimetric microplate assay was used to measure lipase activity based on enzymatic hydrolysis of olive oil emulsion substrate at 37°C and 150 rpm. The emulsion substrates were formulated by using olive oil, triton X-100 (10% v/v in pH 8) and sodium phosphate buffer of pH 8 in ratio of 1:1:1 in the case of Candida sp. lipase. While in the case of immobilized lipozyme RMIM, The emulsion substrates were formulated by using olive oil, triton X-100 (1% v/v in pH 8) and sodium phosphate buffer of pH 8 in ratio of 2:1:1. Absorbance was measured at 655 nm. The stability of this assay (in terms of colored heptane phase absorbance readings) retained more than 92.5% after 24 h at 4°C compared to the absorbance readings measured at zero time. In comparison with other lipase assay methods, beside the developed sensitivity, the reproducibility and the lower limit of detection (LOD) of the proposed method, it permits analyzing of 96 samples at one time in a 96-well microplate. Furthermore, it consumes small quantities of chemicals and unit operations.

Enzymatic Saccharification of Lignocelluloses Should be Conducted at Elevated pH 5.2-6.2

Treesearch

T.Q. Lan; Hongming Lou; J.Y. Zhu

2013-01-01

This study revealed that cellulose enzymatic saccharification response curves of lignocellulosic substrates were very different from those of pure cellulosic substrates in terms of optimal pH and pH operating window. The maximal enzymatic cellulose saccharification of lignocellulosic substrates occurs at substrate suspension

A new lime material for container substrates

USDA-ARS?s Scientific Manuscript database

The primary component in greenhouse potting substrates is sphagnum peatmoss. Substrate solution pH of non-amended peatmoss ranges from 4.0 to 4.5. Ideal pH for most greenhouse floriculture crops ranges from 5.8 to 6.2. Dolomitic lime is most often used to elevate substrate pH in peatmoss-based me...

Probing cathepsin K activity with a selective substrate spanning its active site.

PubMed

Lecaille, Fabien; Weidauer, Enrico; Juliano, Maria A; Brömme, Dieter; Lalmanach, Gilles

2003-10-15

The limited availability of highly selective cathepsin substrates seriously impairs studies designed to monitor individual cathepsin activities in biological samples. Among mammalian cysteine proteases, cathepsin K has a unique preference for a proline residue at P2, the primary determinant of its substrate specificity. Interestingly, congopain from Trypanosoma congolense also accommodates a proline residue in its S2 subsite. Analysis of a congopain model showed that amino acids forming its S2 subsite are identical with those of cathepsin K, except Leu67 which is replaced by a tyrosine residue in cathepsin K. Furthermore, amino acid residues of the congopain S2' binding pocket, which accepts a proline residue, are strictly identical with those of cathepsin K. Abz-HPGGPQ-EDN2ph [where Abz represents o-aminobenzoic acid and EDN2ph (=EDDnp) represents N -(2,4-dinitrophenyl)-ethylenediamine], a substrate initially developed for trypanosomal enzymes, was efficiently cleaved at the Gly-Gly bond by cathepsin K (kcat/ K(m)=426000 M(-1) x s(-1)). On the other hand, Abz-HPGGPQ-EDN2ph was resistant to hydrolysis by cathepsins B, F, H, L, S and V (20 nM enzyme concentration) and the Y67L (Tyr67-->Leu)/L205A cathepsin K mutant (20 nM), but still acted as a competitive inhibitor. Taken together, the selectivity of Abz-HPGGPQ-EDN2ph to cathepsin K primarily depends on the S2 and S2' subsite specificities of cathepsin K and the ionization state of histidine at P3. Whereas Abz-HPGGPQ-EDN2ph was hydrolysed by wild-type mouse fibroblast lysates, its hydrolysis was completely abolished in the cathepsin K-deficient samples, indicating that Abz-HPGGPQ-EDN2ph can be used to monitor selectively cathepsin K activity in physiological fluids and cell lysates.

Probing cathepsin K activity with a selective substrate spanning its active site.

PubMed Central

Lecaille, Fabien; Weidauer, Enrico; Juliano, Maria A; Brömme, Dieter; Lalmanach, Gilles

2003-01-01

The limited availability of highly selective cathepsin substrates seriously impairs studies designed to monitor individual cathepsin activities in biological samples. Among mammalian cysteine proteases, cathepsin K has a unique preference for a proline residue at P2, the primary determinant of its substrate specificity. Interestingly, congopain from Trypanosoma congolense also accommodates a proline residue in its S2 subsite. Analysis of a congopain model showed that amino acids forming its S2 subsite are identical with those of cathepsin K, except Leu67 which is replaced by a tyrosine residue in cathepsin K. Furthermore, amino acid residues of the congopain S2' binding pocket, which accepts a proline residue, are strictly identical with those of cathepsin K. Abz-HPGGPQ-EDN2ph [where Abz represents o-aminobenzoic acid and EDN2ph (=EDDnp) represents N -(2,4-dinitrophenyl)-ethylenediamine], a substrate initially developed for trypanosomal enzymes, was efficiently cleaved at the Gly-Gly bond by cathepsin K (kcat/ K(m)=426000 M(-1) x s(-1)). On the other hand, Abz-HPGGPQ-EDN2ph was resistant to hydrolysis by cathepsins B, F, H, L, S and V (20 nM enzyme concentration) and the Y67L (Tyr67-->Leu)/L205A cathepsin K mutant (20 nM), but still acted as a competitive inhibitor. Taken together, the selectivity of Abz-HPGGPQ-EDN2ph to cathepsin K primarily depends on the S2 and S2' subsite specificities of cathepsin K and the ionization state of histidine at P3. Whereas Abz-HPGGPQ-EDN2ph was hydrolysed by wild-type mouse fibroblast lysates, its hydrolysis was completely abolished in the cathepsin K-deficient samples, indicating that Abz-HPGGPQ-EDN2ph can be used to monitor selectively cathepsin K activity in physiological fluids and cell lysates. PMID:12837132

Offline and online capillary electrophoresis enzyme assays of β-N-acetylhexosaminidase.

PubMed

Křížek, Tomáš; Doubnerová, Veronika; Ryšlavá, Helena; Coufal, Pavel; Bosáková, Zuzana

2013-03-01

Enzyme assays of β-N-acetylhexosaminidase from Aspergillus oryzae using capillary electrophoresis in the offline and online setup have been developed. The pH value and concentration of the borate-based background electrolyte were optimized in order to achieve baseline separation of N,N',N″-triacetylchitotriose, N,N'-diacetylchitobiose, and N-acetyl-D-glucosamine. The optimized method using 25 mM tetraborate buffer, pH 10.0, was evaluated in terms of repeatability, limits of detection, quantification, and linearity. The method was successfully applied to the offline enzyme assay of β-N-acetylhexosaminidase, which was demonstrated by monitoring the hydrolysis of N,N',N″-triacetylchitotriose. The presented method was also utilized to study the pH dependence of enzyme activity. An online assay with N,N'-diacetylchitobiose as a substrate was developed using the Transverse Diffusion of Laminar Flow Profiles model to optimize the injection sequence and in-capillary mixing of substrate and enzyme plugs. The experimental results were in good agreement with predictions of the model. The online assay was successfully used to observe the inhibition effect of N,N'-dimethylformamide on the activity of β-N-acetylhexosaminidase with nanoliter volumes of reagents used per run and a high degree of automation. After adjustment of background electrolyte pH, an online assay with N,N',N″-triacetylchitotriose as a substrate was also performed.

Use of fruit residues for pectinase production by Aspergillus flavipes FP-500 and Aspergillus terreus FP-370.

PubMed

Martínez-Trujillo, A; Arreguín-Rangel, L; García-Rivero, M; Aguilar-Osorio, G

2011-08-01

Utilization of fruit residues for pectinase production by two Aspergillus strains for recognizing the effects of some factors during fermentation and describing enzyme production kinetics. Pectinase production on several fruit residues was compared. The effects of three factors on the production of several pectinases were evaluated by a full factorial 2(k) experimental design. Higher activities were obtained on lemon peel. In both strains, acidic pH values and high carbon source concentration favoured exopectinase and endopectinase production, while higher pH values and low carbon source concentration promoted pectin lyase and rhamnogalacturonase production. Unstructured mathematical modelling provided a good description of pectinase production in a submerged batch culture. Fruit residues were very good substrates for pectinase production, and Aspergillus strains used showed a promising performance in submerged fermentation. Mathematical modelling was useful to describe growth and pectinase production. Lemon peel can be used as a substrate to obtain high pectinase titres by Aspergillus flavipes FP-500 and Aspergillus terreus FP-370. The factors that contributed to improve the yield were identified, which supports the possibility of using this substrate in the industrial production of these enzymes. © 2011 The Authors. Letters in Applied Microbiology © 2011 The Society for Applied Microbiology.

Solution and interfacial behavior of modified silicone polymers and their interactions with solid substrates

NASA Astrophysics Data System (ADS)

Purohit, Parag

Surface treatment is very important step in many applications such as fabric finishing, coatings, cosmetics and personal care. Silicone polymers are a class of organic/inorganic materials that show unique properties such as weak intermolecular forces and high flexibility enabling even a very high molecular weight chain to achieve optimal orientation on surfaces. Material properties such as softness, repellency, bounciness and friction can therefore be tailored by using appropriately modified silicone polymers. Despite wide applications, the underlying mechanisms of material modification are unknown and tailoring silicones for applications remains mostly empirical. Thus the objective of this research is to understand the solution and interfacial behavior of functionalized silicone polymers, which govern their performance in material modification. Modified silicones are simultaneously hydrophobic and oleophobic in nature and due to this nearly universal non-compatibility, the studies of these polymers present unusual challenges. Due to this incompatible nature, the functionalized silicone polymers were emulsified into O/W emulsions to study their solution and interfacial properties. The colloidal properties such as electrokinetic and droplet distribution of these emulsions are assumed to play an important role in the observed surface and physical properties of solid substrates (in present study, cellulosic substrates) as well the stability of emulsions itself. To understand the effects of modified silicones on cellulosic substrates a variety of techniques such as frictional analysis, scanning electron microscopy and atomic force microscopy that can probe from macro to nano level were used. It is hypothesized that the size distribution and charge of silicone emulsions as well as the physiochemical conditions such as pH, control silicone conformation which in turn affect the modification of the substrate properties. With bimodal droplet distribution of silicone emulsions, the nano-sized droplets can penetrate deeper into the substrate to provide bounciness, whereas macro-sized droplets can coat the top layer leading to friction reduction. It was observed that at pH 5.5 the silicone treatment resulted in charge reversal of fibers as opposed to treatment at pH 9.5. On a macroscopic scale 20% reduction in frictional coefficient of the fabric was observed after treatment with quaternized (cationically modified) silicones as compared to untreated fibers. It was also observed using AFM that the fibrils treated with quaternized silicones are uniform, well stacked and smoother than the untreated fibers. Spectroscopic analysis of treated fibers using Raman spectroscopy indicated a decrease in fiber stress as a function of modification of silicone polymer and the interaction pH. It is concluded that the protonated amine functional silicone (below pH 7) as well as the quaternized silicone interacts with the negatively charged cellulose fibers primarily through electrostatic interactions. It is proposed that this initial surface coating is a uniform thin film which allows further deposition of polymer from the emulsion. It was observed that at high pH the zetapotential of silicone emulsions decreases drastically and the nano emulsions turn turbid. It is proposed that the observed electrophoretic and nephelometric behavior at high pH is due to flocculation of nanosized droplets to micron size, which eventually leads to droplets coalescing and emulsion destabilization. It is also postulated that the nano emulsion possess a critical dilution concentration (CDC), above which dilution leads to rapid coalescence. This critical dilution phase was further confirmed through polarity parameter and excimer formation studies which show significantly different polymer and surfactant microstructures near the CDC. Hence it is concluded that the observed surface properties of the substrate obtained above the CDC are significantly different than those below the CDC. The results reveal the vital role of physiochemical parameters such as pH, droplet size, and concentration on the emulsion stability as well as the observed physical/chemical properties of the substrates.

In vitro metabolism of radiolabeled carbohydrates by protective cecal anaerobic bacteria.

PubMed

Hume, M E; Beier, R C; Hinton, A; Scanlan, C M; Corrier, D E; Peterson, D V; DeLoach, J R

1993-12-01

Cecal anaerobic bacteria from adult broilers were cultured in media containing .25% glucose or .25% lactose. Media also contained either [14C]-labeled lactose, glucose, galactose, or lactic acid as metabolic tracers. Cultures were analyzed at 4, 8, and 12 h for pH, radiolabeled and unlabeled volatile fatty acids, and lactic acid. The pH values of cultures containing .25% lactose were significantly (P < .05) higher than the pH values of cultures containing .25% glucose. Lactose cultures reached their lowest pH more slowly than glucose cultures. Concentrations of unlabeled volatile fatty acids increased and lactic acid decreased during incubation of the cultures. Radiolabeled sugars and lactic acid were more readily metabolized to volatile fatty acids in media containing lactose than in media containing glucose. The preferred metabolism of [14C]substrates, independent of media carbohydrate, was in the following order: lactic acid > galactose, lactose > glucose. The volatile fatty acids in which radiolabel was most concentrated were acetic acid, propionic acid, or butyric acid.

Production of a Pseudomonas lipase in n-alkane substrate and its isolation using an improved ammonium sulfate precipitation technique.

PubMed

Kanwar, Lambit; Gogoi, Binod Kumar; Goswami, Pranab

2002-09-01

Among the various lipidic and non-lipidic substances, normal alkanes within the chain lengths of C-12 to C-20 served as the best carbon substrates for the production of extracellular lipase by Pseudomonas species G6. Maximum lipase production of 25 U/ml of the culture broth was obtained by using n-hexadecane as the sole carbon substrate. The optimum pH of 8 and temperature of 34 + 1 degrees C were demonstrated for the production of lipase in n-hexadecane substrate. The optimum concentration of iron, which played a critical role on the lipase production, was found to be 0.25 mg/l. Lipase production could be enhanced to nearly 2.4-fold by using tributyrin at a concentration of 0.05% (v/v) in the culture medium. High recovery of the lipase protein (83%) from the culture broth was achieved by treating the culture supernatant with Silicone 21 Defoamer followed by ammonium sulfate (60% saturation) fractionation.

Improve biogas production from low-organic-content sludge through high-solids anaerobic co-digestion with food waste.

PubMed

Liu, Chuanyang; Li, Huan; Zhang, Yuyao; Liu, Can

2016-11-01

Anaerobic co-digestion of sewage sludge and food waste was tested at two different total solid (TS) concentrations. In the low-solids group with TS 4.8%, the biogas production increased linearly as the ratio of food waste in substrate increased from 0 to 100%, but no synergetic effect was found between the two substrates. Moreover, the additive food waste resulted in the accumulation of volatile fatty acids and decelerated biogas production. Thus, the blend ratio of food waste should be lower than 50%. While in the high-solids group with TS 14%, the weak alkaline environment with pH 7.5-8.5 avoided excessive acidification but high concentration of free ammonia was a potential risk. However, good synergetic effect was found between the two substrates because the added food waste improved mass transfer in sludge cake. Thus, 50% was recommended as the optimum ratio of food waste in substrate because of the best synergetic effect. Copyright © 2016 Elsevier Ltd. All rights reserved.

Modeling and verification of process parameters for the production of tannase by Aspergillus oryzae under submerged fermentation using agro-wastes.

PubMed

Varadharajan, Venkatramanan; Vadivel, Sudhan Shanmuga; Ramaswamy, Arulvel; Sundharamurthy, Venkatesaprabhu; Chandrasekar, Priyadharshini

2017-01-01

Tannase production by Aspergillus oryzae using various agro-wastes as substrates by submerged fermentation was studied in this research. The microbe was isolated from degrading corn kernel obtained from the corn fields at Tiruchengode, India. The microbial identification was done using 18S rRNA gene analysis. The agro-wastes chosen for the study were pomegranate rind, Cassia auriculata flower, black gram husk, and tea dust. The process parameters chosen for optimization study were substrate concentration, pH, temperature, and incubation period. During one variable at a time optimization, the pomegranate rind extract produced maximum tannase activity of 138.12 IU/mL and it was chosen as the best substrate for further experiments. The quadratic model was found to be the effective model for prediction of tannase production by A. oryzae. The optimized conditions predicted by response surface methodology (RSM) with genetic algorithm (GA) were 1.996% substrate concentration, pH of 4.89, temperature of 34.91 °C, and an incubation time of 70.65 H with maximum tannase activity of 138.363 IU/mL. The confirmatory experiment under optimized conditions showed tannase activity of 139.22 IU/mL. Hence, RSM-GA pair was successfully used in this study to optimize the process parameters required for the production of tannase using pomegranate rind. © 2015 International Union of Biochemistry and Molecular Biology, Inc.

pH-adjustment strategy for volatile fatty acid production from high-strength wastewater for biological nutrient removal.

PubMed

Xie, Li; Liu, Hui; Chen, Yin-Guang; Zhou, Qi

2014-01-01

Volatile fatty acid (VFA) production from three types of high-strength organic wastewater (cassava thin stillage, starch wastewater and yellow-wine processing wastewater) were compared. The results showed that cassava thin stillage was the most suitable substrate, based on its high specific VFA production (0.68 g chemical oxygen demand (COD)/g initial soluble chemical oxygen demand (SCOD)) and yield (0.72 g COD/g SCOD) as well as low nutrient content in the substrate and fermented liquid. The acid fermented cassava thin stillage was evaluated and compared with sodium acetate in a sequencing batch reactor system. Total nitrogen removal efficiency was higher with fermented cassava thin stillage than with the sodium acetate. The effects of pH and a pH-adjustment strategy on VFA production and composition were determined using cassava thin stillage. At an initial pH range of 7-11, a relatively high VFA concentration of about 9 g COD/L was obtained. The specific VFA production (g COD/g initial SCOD) increased from 0.27 to 0.47 to 0.67 at pH 8 and from 0.26 to 0.68 to 0.81 at pH 9 (initial pH, interval pH, and constant pH adjustment, respectively). The dominant VFA species changed significantly with the increasing frequency of the pH adjustment. Further studies will examine the metabolic pathways responsible for VFA composition.

Low Substrate Loading Limits Methanogenesis and Leads to High Coulombic Efficiency in Bioelectrochemical Systems

PubMed Central

Sleutels, Tom H. J. A.; Molenaar, Sam D.; Heijne, Annemiek Ter; Buisman, Cees J. N.

2016-01-01

A crucial aspect for the application of bioelectrochemical systems (BESs) as a wastewater treatment technology is the efficient oxidation of complex substrates by the bioanode, which is reflected in high Coulombic efficiency (CE). To achieve high CE, it is essential to give a competitive advantage to electrogens over methanogens. Factors that affect CE in bioanodes are, amongst others, the type of wastewater, anode potential, substrate concentration and pH. In this paper, we focus on acetate as a substrate and analyze the competition between methanogens and electrogens from a thermodynamic and kinetic point of view. We reviewed experimental data from earlier studies and propose that low substrate loading in combination with a sufficiently high anode overpotential plays a key-role in achieving high CE. Low substrate loading is a proven strategy against methanogenic activity in large-scale reactors for sulfate reduction. The combination of low substrate loading with sufficiently high overpotential is essential because it results in favorable growth kinetics of electrogens compared to methanogens. To achieve high current density in combination with low substrate concentrations, it is essential to have a high specific anode surface area. New reactor designs with these features are essential for BESs to be successful in wastewater treatment in the future. PMID:27681899

Low Substrate Loading Limits Methanogenesis and Leads to High Coulombic Efficiency in Bioelectrochemical Systems.

PubMed

Sleutels, Tom H J A; Molenaar, Sam D; Heijne, Annemiek Ter; Buisman, Cees J N

2016-01-05

A crucial aspect for the application of bioelectrochemical systems (BESs) as a wastewater treatment technology is the efficient oxidation of complex substrates by the bioanode, which is reflected in high Coulombic efficiency (CE). To achieve high CE, it is essential to give a competitive advantage to electrogens over methanogens. Factors that affect CE in bioanodes are, amongst others, the type of wastewater, anode potential, substrate concentration and pH. In this paper, we focus on acetate as a substrate and analyze the competition between methanogens and electrogens from a thermodynamic and kinetic point of view. We reviewed experimental data from earlier studies and propose that low substrate loading in combination with a sufficiently high anode overpotential plays a key-role in achieving high CE. Low substrate loading is a proven strategy against methanogenic activity in large-scale reactors for sulfate reduction. The combination of low substrate loading with sufficiently high overpotential is essential because it results in favorable growth kinetics of electrogens compared to methanogens. To achieve high current density in combination with low substrate concentrations, it is essential to have a high specific anode surface area. New reactor designs with these features are essential for BESs to be successful in wastewater treatment in the future.

Kinetic, Thermodynamic, and Structural Insight into the Mechanism of Phosphopantetheine Adenylyltransferase from Mycobacterium tuberculosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wubben, Thomas J.; Mesecar, Andrew D.; UIC)

Phosphopantetheine adenylyltransferase (PPAT) catalyzes the penultimate step in the coenzyme A (CoA) biosynthetic pathway, reversibly transferring an adenylyl group from ATP to 4'-phosphopantetheine (PhP) to form dephosphocoenzyme A. This reaction sits at the branch point between the de novo pathway and the salvage pathway, and has been shown to be a rate-limiting step in the biosynthesis of CoA. Importantly, bacterial and mammalian PPATs share little sequence homology, making the enzyme a potential target for antibiotic development. A series of steady-state kinetic, product inhibition, and direct binding studies with Mycobacterium tuberculosis PPAT (MtPPAT) was conducted and suggests that the enzyme utilizesmore » a nonrapid-equilibrium random bi-bi mechanism. The kinetic response of MtPPAT to the binding of ATP was observed to be sigmoidal under fixed PhP concentrations, but substrate inhibition was observed at high PhP concentrations under subsaturating ATP concentrations, suggesting a preferred pathway to ternary complex formation. Negative cooperativity in the kinetic response of MtPPAT to PhP binding was observed under certain conditions and confirmed thermodynamically by isothermal titration calorimetry, suggesting the formation of an asymmetric quaternary structure during sequential ligation of substrates. Asymmetry in binding was also observed in isothermal titration calorimetry experiments with dephosphocoenzyme A and CoA. X-ray structures of MtPPAT in complex with PhP and the nonhydrolyzable ATP analogue adenosine-5'-[({alpha},{beta})-methyleno]triphosphate were solved to 1.57 {angstrom} and 2.68 {angstrom}, respectively. These crystal structures reveal small conformational changes in enzyme structure upon ligand binding, which may play a role in the nonrapid-equilibrium mechanism. We suggest that the proposed kinetic mechanism and asymmetric character in MtPPAT ligand binding may provide a means of reaction and pathway regulation in addition to that of the previously determined CoA feedback.« less

Dolomitic lime amendment affects pine bark substrate pH, nutrient availability, and plant growth: A review

USDA-ARS?s Scientific Manuscript database

Dolomitic lime (DL) is one of the most commonly used fertilizer amendments in nursery container substrates. It is used to adjust pH of pine bark substrates from their native pH, 4.1 to 5.1, up to about pH 6. Additions of DL have been shown to be beneficial, inconsequential, or detrimental dependin...

Dewetting behavior of polystyrene film filled with (C6H5C2H4NH3)2PbI4

NASA Astrophysics Data System (ADS)

Xue, Longjian; Cheng, Ziyong; Fu, Jun; Han, Yanchun

2008-08-01

The dewetting behavior of thin (about 30 nm) polystyrene (PS) films filled with different amount of (C6H5C2H4NH3)2PbI4 (PhE-PbI4) on the silicon substrate with a native oxide layer was investigated. For different additive concentrations, PhE-PbI4 showed different spatial distributions in the PS films, which had a strong influence on the film wettability, dewetting dynamics, and mechanism. With 0.5 wt % additive, PhE-PbI4 formed a noncontinuous diffusion layer, which caused a continuous hole nucleation in the film. With about 1 wt % additive, a continuous gradient distribution layer of PhE-PbI4 formed in the film, which inhibited the dewetting. When the concentration is higher (2 wt %), large PhE-PbI4 aggregates, in addition to the PhE-PbI4 continuous layer, formed in the film. These large aggregates (larger than radius of gyration of PS) migrated to the interface, resulting in the hole nucleation and eventually the complete dewetting of the film.

78 FR 59555 - Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for the Fluted...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-26

... physical and chemical water quality parameters (such as temperature, dissolved oxygen, pH, and conductivity... unknown. High temperatures can reduce dissolved oxygen concentrations in the water, which slows growth... encystment, increase oxygen consumption, reduce the speed in which they orient themselves in the substrate...

Isolation and identification of chitinolytic bacteria of pohara river of South East Sulawesi and the optimization production of chitinase enzyme

NASA Astrophysics Data System (ADS)

Halimahtussadiyah, R.; Natsir, Muh.; Kurniawati, Desy; Utamy, Sukma Puspita

2017-03-01

Isolation and identification of chitinolytic bacteria from pohara river and optimation of chitinase enzyme production has been conducted. The aims of the study were isolation, characterize and optimaze of chitinase enzyme production. This study was carried out in three stages; isolation and selection of chitinolytic bacteria, characterization and identification of selected bacteria; optimization of the production of the enzyme (substrate concentration, temperature, and pH), and the determination of growth curve of T3 isolate. The chitinase activity assay was carried out using Schales method. The results of the screening obtained 6 isolates of potential bacteria of chitinolytic. The T3 isolate then was selected for the enzyme production, because it had the highest chitinolytic index of 22.31 mm. The morphological and biochemical observation showed that T3 isolate as a group of bacteria Aerobacter with Gram-negative nature, and shaped bacillus. The optimum condition for chitinase enzyme production was in chitin substrat concentration 0.06%, temperature of 30°C, and pH of 6.

Colloidal chitin stained with Remazol Brilliant Blue R, a useful substrate to select chitinolytic microorganisms and to evaluate chitinases.

PubMed

Gómez Ramírez, M; Rojas Avelizapa, L I; Rojas Avelizapa, N G; Cruz Camarillo, R

2004-02-01

A simple and sensitive method based on the use of colloidal chitin stained with Remazol Brilliant Blue R (RBB) is proposed to evaluate chitinase activity. If this colloidal-stained substrate is included as a carbon source in a liquid medium, this technique allows the selection or the comparison of chitinolytic microorganisms. The colloidal substrate is proportionally solubilized and the dye released is spectrophotometrically quantified at 595 nm. The procedures used for the staining and fixing of RBB in the colloidal chitin, and a comparison with the commercial substrate chitin-azure, are presented. The influence of several physicochemical and enzymatic parameters on the release of dyes is also shown. Both stained substrates were used for studying the effect of pH, substrate concentration, temperature and time on the chitinase reaction of Bacillus thuringiensis Bt-107.

Optimization of volatile fatty acid production with co-substrate of food wastes and dewatered excess sludge using response surface methodology.

PubMed

Hong, Chen; Haiyun, Wu

2010-07-01

Central-composite design (CCD) and response surface methodology (RSM) were used to optimize the parameters of volatile fatty acid (VFA) production from food wastes and dewatered excess sludge in a semi-continuous process. The effects of four variables (food wastes composition in the co-substrate of food wastes and excess sludge, hydraulic retention time (HRT), organic loading rate (OLR), and pH) on acidogenesis were evaluated individually and interactively. The optimum condition derived via RSM was food wastes composition, 88.03%; HRT, 8.92 days; OLR, 8.31 g VSS/ld; and pH 6.99. The experimental VFA concentration was 29,099 mg/l under this optimum condition, which was well in agreement with the predicted value of 28,000 mg/l. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Fungi immobilization for landfill leachate treatment.

PubMed

Saetang, Jenjira; Babel, Sandhya

2010-01-01

This paper investigated treatment of landfill leachate collected from Nonthaburi landfill site, Thailand, by using immobilized white rot fungi, namely, Trametes versicolor BCC 8725 and Flavodon flavus BCC 17421. Effects of pH and co-substrates were investigated at different contact times. Three types of co-substrates as carbon source used in this study are glucose, corn starch and cassava. Treatment efficiency was evaluated based on color, BOD, and COD removal. Initial BOD and COD were found to be 5,600 and 34,560 mg/L, respectively. The optimum pH was found to be 4, the optimum co-substrate concentration (glucose, corn starch and cassava) was 3 g/L and the optimum contact time was 10 days for both types of fungi. Addition of glucose, corn starch and cassava as co-substrate at optimum conditions could remove 78, 74, and 66% of color, respectively for T. versicolor and 73, 68, and 60%, respectively, for F. flavus. Moreover, for T. versicolor, BOD and COD reduction of 69 and 57%, respectively, could be achieved at optimum conditions when using glucose as a co-substrate. For F. flavus, BOD and COD reduction of 66 and 52%, respectively were obtained when using glucose as a co-substrate. White rot fungi can be considered potentially useful in the treatment of landfill leachate as they can help in removing color, BOD and COD due to their biodegradative abilities.

Atomic force microscopy of gastric mucin

NASA Astrophysics Data System (ADS)

Chasan, Bernard; Hong, Zhenning; Bansil, Rama; Turner, Bradley; Ramakrishnan Bhaskar, K.; Afdhal, Nezam

2001-03-01

We report on the first results from an AFM study of porcine gastric mucin employing the tapping mode technique in aqueous solution. This glycoprotein is responsible for protecting the stomach epithelium from acid damage. Mucin was imaged on a mica substrate at pH7, and at pH2. At the higher pH we detected individual molecules in disordered configuration, with characteristic lengths of 20-40 nm. At the lower pH the mucin forms extended rod-like clusters that, at high concentrations, are aligned into planar arrays. Individual clusters are of order 50 nm long and 20 nm wide while the entire array is of order several hundred nm both in length and width. The clustering behavior at low pH is consistent with that previously detected in dynamic light scattering experiments by Cao et. al. (Biophysical J. 76:120-1258 1999).

Production of fructanase by a wild strain of Saccharomyces cerevisiae on tequila agave fructan.

PubMed

Corona-González, R I; Pelayo-Ortiz, C; Jacques, G; Guatemala, G; Arriola, E; Arias, J A; Toriz, G

2015-01-01

A new wild strain of Saccharomyces cerevisiae (CF3) isolated from tequila must was evaluated for production of fructanase on Agave tequilana Weber fructan (FT). Fructanase activity (F) was assessed by a 3(3) factorial design (substrate, temperature and pH). High enzymatic activity (31.1 U/ml) was found at 30 °C, pH 5, using FT (10 g/l) as substrate. The effect of initial substrate concentration on F (FT0, 5.7-66 g/l) was studied and it was found that F was highest (44.8 U/ml) at FT0 25 g/l. A 2(2) factorial experimental design with five central points was utilized to study the effect of stirring and aeration on fructanase activity; stirring exhibited a stronger effect on F. The ratio fructanase to invertase (F/S) was 0.57, which confirms that the enzymes are fructanase. Crude fructanase reached high substrate hydrolysis (48 wt%) in 10 h. It is shown that S. cerevisiae CF3 was able to produce large amounts of fructanase by growing it on fructan from A. tequilana.

Organic cation rhodamines for screening organic cation transporters in early stages of drug development.

PubMed

Ugwu, Malachy C; Oli, Angus; Esimone, Charles O; Agu, Remigius U

The aim of this study was to investigate the suitability of rhodamine-123, rhodamine-6G and rhodamine B as non-radioactive probes for characterizing organic cation transporters in respiratory cells. Fluorescent characteristics of the compounds were validated under standard in vitro drug transport conditions (buffers, pH, and light). Uptake/transport kinetics and intracellular accumulation of the compounds were investigated. Uptake/transport mechanisms were investigated by comparing the effect of pH, temperature, concentration, polarity, OCTs/OCTNs inhibitors/substrates, and metabolic inhibitors on the cationic dyes uptake in Calu-3 cells. Fluorescence stability and intensity of the compounds were altered by buffer composition, light, and pH. Uptake of the dyes was concentration-, temperature- and pH-dependent. OCTs/OCTNs inhibitors significantly reduced intracellular accumulation of the compounds. Whereas rhodamine-B uptake was sodium-dependent, pH had no effect on rhodamine-123 and rhodamine-6G uptake. Transport of the dyes across the cells was polarized: (AP→BL>BL→AP transport) and saturable: {V max =14.08±2.074, K m =1821±380.4 (rhodamine-B); V max =6.555±0.4106, K m =1353±130.4 (rhodamine-123) and V max =0.3056±0.01402, K m =702.9±60.97 (rhodamine-6G)}. The dyes were co-localized with MitoTracker®, the mitochondrial marker. Cationic rhodamines, especially rhodamine-B and rhodamine- 6G can be used as organic cation transporter substrates in respiratory cells. During such studies, buffer selection, pH and light exposure should be taken into consideration. Copyright © 2016 Elsevier Inc. All rights reserved.

Microbial Community Responses to Organophosphate Substrate Additions in Contaminated Subsurface Sediments

PubMed Central

Martinez, Robert J.; Wu, Cindy H.; Beazley, Melanie J.; Andersen, Gary L.; Conrad, Mark E.; Hazen, Terry C.; Taillefert, Martial; Sobecky, Patricia A.

2014-01-01

Background Radionuclide- and heavy metal-contaminated subsurface sediments remain a legacy of Cold War nuclear weapons research and recent nuclear power plant failures. Within such contaminated sediments, remediation activities are necessary to mitigate groundwater contamination. A promising approach makes use of extant microbial communities capable of hydrolyzing organophosphate substrates to promote mineralization of soluble contaminants within deep subsurface environments. Methodology/Principal Findings Uranium-contaminated sediments from the U.S. Department of Energy Oak Ridge Field Research Center (ORFRC) Area 2 site were used in slurry experiments to identify microbial communities involved in hydrolysis of 10 mM organophosphate amendments [i.e., glycerol-2-phosphate (G2P) or glycerol-3-phosphate (G3P)] in synthetic groundwater at pH 5.5 and pH 6.8. Following 36 day (G2P) and 20 day (G3P) amended treatments, maximum phosphate (PO4 3−) concentrations of 4.8 mM and 8.9 mM were measured, respectively. Use of the PhyloChip 16S rRNA microarray identified 2,120 archaeal and bacterial taxa representing 46 phyla, 66 classes, 110 orders, and 186 families among all treatments. Measures of archaeal and bacterial richness were lowest under G2P (pH 5.5) treatments and greatest with G3P (pH 6.8) treatments. Members of the phyla Crenarchaeota, Euryarchaeota, Bacteroidetes, and Proteobacteria demonstrated the greatest enrichment in response to organophosphate amendments and the OTUs that increased in relative abundance by 2-fold or greater accounted for 9%–50% and 3%–17% of total detected Archaea and Bacteria, respectively. Conclusions/Significance This work provided a characterization of the distinct ORFRC subsurface microbial communities that contributed to increased concentrations of extracellular phosphate via hydrolysis of organophosphate substrate amendments. Within subsurface environments that are not ideal for reductive precipitation of uranium, strategies that harness microbial phosphate metabolism to promote uranium phosphate precipitation could offer an alternative approach for in situ sequestration. PMID:24950228

Partial Purification and Properties of an Alkaline α-Galactosidase from Mature Leaves of Cucurbita pepo1

PubMed Central

Gaudreault, Pierre-Richard; Webb, John A.

1983-01-01

A fourth molecular from of α-galactosidase, designated LIV, an alkaline α-galactosidase, was isolated from leaves of Cucurbita pepo and purified 165-fold. It was active over a narrow pH range with optimal hydrolysis of p-nitrophenyl-α-d-galactoside and stachyose at pH 7.5. The rate of stachyose hydrolysis was 10 times that of raffinose. Km determinations in McIlvaine buffer (200 millimolar Na2-phosphate, 100 millimolar citric acid, pH 7.5) for p-nitrophenyl-α-d-galactoside, stachyose, and raffinose were 1.40, 4.5, and 36.4 millimolar, respectively. LIV was partially inhibited by Ca2+, Mg2+, and Mn2+, more so by Ni2+, Zn2+, and Co2+, and highly so by Cu2+, Ag2+, Hg2+ and by p-chloromercuribenzoate. It was not inhibited by high concentrations of the substrate p-nitrophenyl-α-d-galactoside or by myo-inositol, but α-d-galactose was a strong inhibitor. As observed for most other forms of α-galactosidase, LIV only catalyzed the hydrolysis of glycosides possessing the α-d-galactose configuration at C1, C2, and C4, and did not hydrolyze p-nitrophenyl-α-d-fucoside (α-d-galactose substituted at C6). The enzyme was highly sensitive to buffers and chelating agents. Maximum hydrolytic activity for p-nitrophenyl-α-d-galactoside was obtained in McIlvaine buffer (pH 7.5). In 10 millimolar triethanolaminehydrochloride-NaOH (pH 7.5) or 10 millimolar Hepes-NaOH (pH 7.5), hydrolytic activity was virtually eliminated, but the addition of low concentrations of either ethylenediaminetetraacetate or citrate to these buffers restored activity almost completely. Partial restoration of activity was also observed, but at higher concentrations, with pyruvate and malate. Similar effects were found for stachyose hydrolysis, but in addition some inhibition of LIV in McIlvaine buffer, possibly due to the high phosphate concentration, was observed with this substrate. It is questionable whether the organic acid anions possess any regulatory control of LIVin vivo. It was possible that the results reflected the ability of these anions, and ethylene-diaminetetraacetate, to restore LIV activity through coordination with some toxic cation introduced as a buffer contaminant. Images Fig. 1 PMID:16662884

Nitrogen form affects pH and EC of whole pine tree substrate and growth of petunia

USDA-ARS?s Scientific Manuscript database

Wood-based substrates are potential alternatives or amendments to traditional peat-based and pine bark substrates. Undesirable changes in substrate pH may result from the application of supplemental fertilizer required by some crops grown in wood-based substrates. Experiments were conducted to evalu...

Adsorption behavior of methacryloyloxydecyl dihydrogen phosphate on an apatite surface at neutral pH.

PubMed

Bista, Baba; Nakashima, Syozi; Nikaido, Toru; Sadr, Alireza; Takagaki, Tomohiro; Romero, Maria J R H; Sato, Takaaki; Tagami, Junji

2016-04-01

This study aimed to quantify the adsorption affinity of neutralized 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP-N) toward hydroxyapatite (HA) and dicalcium phosphate dihydrate (DCPD) at pH 7.0 by employing the Langmuir isotherm model. Furthermore, the effects of inorganic phosphate (Pi) and fluoride (F(-) ) ions on the adsorption of 10-MDP-N onto HA and DCPD were examined. Fixed amounts of HA and DCPD powders were suspended in different concentrations of 10-MDP-N solutions and were incubated for 18 h. Equilibrated concentrations of 10-MDP-N were measured by spectrophotometry and the adsorption affinity was estimated using the Langmuir model. Moreover, the adsorption was examined by zeta-potential analysis. The results indicated that significant Langmuir correlation was noted in both substrates, along with an increasing negative zeta-potential; however, in DCPD the correlation was less strong. The addition of 1.0 mM Pi slightly delayed the adsorption of 10-MDP-N onto both substrates, whereas 3.0 mM Pi drastically delayed adsorption onto HA but completely inhibited adsorption onto DCPD. Up to 50 ppm, F(-) enhanced the adsorption onto HA, and the adsorption plateaued at higher concentrations of F(-) , whereas no obvious influence of F(-) on the adsorption onto DCPD was noted. © 2016 Eur J Oral Sci.

Polyhydroxyalkanoate Production on Waste Water Treatment Plants: Process Scheme, Operating Conditions and Potential Analysis for German and European Municipal Waste Water Treatment Plants

PubMed Central

Pittmann, Timo; Steinmetz, Heidrun

2017-01-01

This work describes the production of polyhydroxyalkanoates (PHA) as a side stream process on a municipal waste water treatment plant (WWTP) and a subsequent analysis of the production potential in Germany and the European Union (EU). Therefore, tests with different types of sludge from a WWTP were investigated regarding their volatile fatty acids (VFA) production-potential. Afterwards, primary sludge was used as substrate to test a series of operating conditions (temperature, pH, retention time (RT) and withdrawal (WD)) in order to find suitable settings for a high and stable VFA production. In a second step, various tests regarding a high PHA production and stable PHA composition to determine the influence of substrate concentration, temperature, pH and cycle time of an installed feast/famine-regime were conducted. Experiments with a semi-continuous reactor operation showed that a short RT of 4 days and a small WD of 25% at pH = 6 and around 30 °C is preferable for a high VFA production rate (PR) of 1913 mgVFA/(L×d) and a stable VFA composition. A high PHA production up to 28.4% of cell dry weight (CDW) was reached at lower substrate concentration, 20 °C, neutral pH-value and a 24 h cycle time. A final step a potential analysis, based on the results and detailed data from German waste water treatment plants, showed that the theoretically possible production of biopolymers in Germany amounts to more than 19% of the 2016 worldwide biopolymer production. In addition, a profound estimation regarding the EU showed that in theory about 120% of the worldwide biopolymer production (in 2016) could be produced on European waste water treatment plants. PMID:28952533

The copper spoil heap Knappenberg, Austria, as a model for metal habitats - Vegetation, substrate and contamination.

PubMed

Adlassnig, Wolfram; Weiss, Yasmin S; Sassmann, Stefan; Steinhauser, Georg; Hofhansl, Florian; Baumann, Nils; Lichtscheidl, Irene K; Lang, Ingeborg

2016-09-01

Historic mining in the Eastern Alps has left us with a legacy of numerous spoil heaps hosting specific, metal tolerant vegetation. Such habitats are characterized by elevated concentrations of toxic elements but also by high irradiation, a poorly developed substrate or extreme pH of the soil. This study investigates the distribution of vascular plants, mosses and lichens on a copper spoil heap on the ore bearing Knappenberg formed by Prebichl Layers and Werfener Schist in Lower Austria. It serves as a model for discriminating between various ecological traits and their effects on vegetation. Five distinct clusters were distinguished: (1) The bare, metal rich Central Spoil Heap was only colonised by highly resistant specialists. (2) The Northern and (3) Southern Peripheries contained less copper; the contrasting vegetation was best explained by the different microclimate. (4) A forest over acidic bedrock hosted a vegetation overlapping with the periphery of the spoil heap. (5) A forest over calcareous bedrock was similar to the spoil heap with regard to pH and humus content but hosted a vegetation differing strongly to all other habitats. Among the multiple toxic elements at the spoil heap, only Cu seems to exert a crucial influence on the vegetation pattern. Besides metal concentrations, irradiation, humidity, humus, pH and grain size distribution are important for the establishment of a metal tolerant vegetation. The difference between the species poor Northern and the diverse Southern Periphery can be explained by the microclimate rather than by the substrate. All plant species penetrating from the forest into the periphery of the spoil heap originate from the acidic but not from the calcareous bedrock. Copyright © 2016 Elsevier B.V. All rights reserved.

Plackett-Burman Design for rGILCC1 Laccase Activity Enhancement in Pichia pastoris: Concentrated Enzyme Kinetic Characterization.

PubMed

Morales-Álvarez, Edwin D; Rivera-Hoyos, Claudia M; Cardozo-Bernal, Ángela M; Poutou-Piñales, Raúl A; Pedroza-Rodríguez, Aura M; Díaz-Rincón, Dennis J; Rodríguez-López, Alexander; Alméciga-Díaz, Carlos J; Cuervo-Patiño, Claudia L

2017-01-01

Laccases are multicopper oxidases that catalyze aromatic and nonaromatic compounds with concomitant reduction of molecular oxygen to water. They are of great interest due to their potential biotechnological applications. In this work we statistically improved culture media for recombinant GILCC1 (rGILCC1) laccase production at low scale from Ganoderma lucidum containing the construct pGAPZ α A- GlucPost -Stop in Pichia pastoris . Temperature, pH stability, and kinetic parameter characterizations were determined by monitoring concentrate enzyme oxidation at different ABTS substrate concentrations. Plackett-Burman Design allowed improving enzyme activity from previous work 36.08-fold, with a laccase activity of 4.69 ± 0.39 UL -1 at 168 h of culture in a 500 mL shake-flask. Concentrated rGILCC1 remained stable between 10 and 50°C and retained a residual enzymatic activity greater than 70% at 60°C and 50% at 70°C. In regard to pH stability, concentrated enzyme was more stable at pH 4.0 ± 0.2 with a residual activity greater than 90%. The lowest residual activity greater than 55% was obtained at pH 10.0 ± 0.2. Furthermore, calculated apparent enzyme kinetic parameters were a V max of 6.87 × 10 -5  mM s -1 , with an apparent K m of 5.36 × 10 -2  mM. Collectively, these important stability findings open possibilities for applications involving a wide pH and temperature ranges.

Plackett-Burman Design for rGILCC1 Laccase Activity Enhancement in Pichia pastoris: Concentrated Enzyme Kinetic Characterization

PubMed Central

Morales-Álvarez, Edwin D.; Rivera-Hoyos, Claudia M.; Cardozo-Bernal, Ángela M.; Pedroza-Rodríguez, Aura M.; Díaz-Rincón, Dennis J.; Rodríguez-López, Alexander; Alméciga-Díaz, Carlos J.; Cuervo-Patiño, Claudia L.

2017-01-01

Laccases are multicopper oxidases that catalyze aromatic and nonaromatic compounds with concomitant reduction of molecular oxygen to water. They are of great interest due to their potential biotechnological applications. In this work we statistically improved culture media for recombinant GILCC1 (rGILCC1) laccase production at low scale from Ganoderma lucidum containing the construct pGAPZαA-GlucPost-Stop in Pichia pastoris. Temperature, pH stability, and kinetic parameter characterizations were determined by monitoring concentrate enzyme oxidation at different ABTS substrate concentrations. Plackett-Burman Design allowed improving enzyme activity from previous work 36.08-fold, with a laccase activity of 4.69 ± 0.39 UL−1 at 168 h of culture in a 500 mL shake-flask. Concentrated rGILCC1 remained stable between 10 and 50°C and retained a residual enzymatic activity greater than 70% at 60°C and 50% at 70°C. In regard to pH stability, concentrated enzyme was more stable at pH 4.0 ± 0.2 with a residual activity greater than 90%. The lowest residual activity greater than 55% was obtained at pH 10.0 ± 0.2. Furthermore, calculated apparent enzyme kinetic parameters were a Vmax of 6.87 × 10−5 mM s−1, with an apparent Km of 5.36 × 10−2 mM. Collectively, these important stability findings open possibilities for applications involving a wide pH and temperature ranges. PMID:28421142

Modeling carbon dioxide, pH, and un-ionized ammonia relationships in serial reuse systems

USGS Publications Warehouse

Colt, J.; Watten, B.; Rust, M.

2009-01-01

In serial reuse systems, excretion of metabolic carbon dioxide has a significant impact on ambient pH, carbon dioxide, and un-ionized ammonia concentrations. This impact depends strongly on alkalinity, water flow rate, feeding rate, and loss of carbon dioxide to the atmosphere. A reduction in pH from metabolic carbon dioxide can significantly reduce the un-ionized ammonia concentration and increase the carbon dioxide concentrations compared to those parameters computed from influent pH. The ability to accurately predict pH in serial reuse systems is critical to their design and effective operation. A trial and error solution to the alkalinity-pH system was used to estimate important water quality parameters in serial reuse systems. Transfer of oxygen and carbon dioxide across the air-water interface, at overflow weirs, and impacts of substrate-attached algae and suspended bacteria were modeled. Gas transfer at the weirs was much greater than transfer across the air-water boundary. This simulation model can rapidly estimate influent and effluent concentrations of dissolved oxygen, carbon dioxide, and un-ionized ammonia as a function of water temperature, elevation, water flow, and weir type. The accuracy of the estimates strongly depends on assumed pollutional loading rates and gas transfer at the weirs. The current simulation model is based on mean daily loading rates; the impacts of daily variation loading rates are discussed. Copies of the source code and executable program are available free of charge.

Modeling Carbon Dioxide, pH and Un-Ionized Ammonia Relationships in Serial Reuse Systems

USGS Publications Warehouse

Watten, Barnaby J.; Rust, Michael; Colt, John

2009-01-01

In serial reuse systems, excretion of metabolic carbon dioxide has a significant impact on ambient pH, carbon dioxide, and un-ionized ammonia concentrations. This impact depends strongly on alkalinity, water flow rate, feeding rate, and loss of carbon dioxide to the atmosphere. A reduction in pH from metabolic carbon dioxide can significantly reduce the un-ionized ammonia concentration and increase the carbon dioxide concentrations compared to those parameters computed from influent pH. The ability to accurately predict pH in serial reuse systems is critical to their design and effective operation. A trial and error solution to the alkalinity–pH system was used to estimate important water quality parameters in serial reuse systems. Transfer of oxygen and carbon dioxide across the air–water interface, at overflow weirs, and impacts of substrate-attached algae and suspended bacteria were modeled. Gas transfer at the weirs was much greater than transfer across the air–water boundary. This simulation model can rapidly estimate influent and effluent concentrations of dissolved oxygen, carbon dioxide, and un-ionized ammonia as a function of water temperature, elevation, water flow, and weir type. The accuracy of the estimates strongly depends on assumed pollutional loading rates and gas transfer at the weirs. The current simulation model is based on mean daily loading rates; the impacts of daily variation loading rates are discussed. Copies of the source code and executable program are available free of charge.

Impact of steel slag on the ammonium adsorption by zeolite and a new configuration of zeolite-steel slag substrate for constructed wetlands.

PubMed

Shi, Pengbo; Jiang, Yingbo; Zhu, Hongtao; Sun, Dezhi

2017-07-01

The CaO dissolution from slag, as well as the effects of influencing parameters (i.e. pH and Ca 2+ concentration) on the ammonium adsorption onto zeolite, was systematically studied in this paper. Modeling results of Ca 2+ and OH - release from slag indicated that pseudo-second-order reaction had a better fitness than pseudo-first-order reaction. Changing pH value from 7 to 12 resulted in a drastic reduction of the ammonium adsorption capacity on zeolite, from the peak adsorption capacity at pH 7. High Ca 2+ concentration in solution also inhibited the adsorption of ammonium onto zeolite. There are two proposed mechanisms for steel slag inhibiting the ammonium adsorption capacity of zeolite. On the one hand, OH - released from steel slag can react with ammonium ions to produce the molecular form of ammonia (NH 3 ·H 2 O), which would cause the dissociation of NH 4 + from zeolite. On the other hand, Ca 2+ could replace the NH 4 + ions to adhere onto the surface of zeolite. An innovative substrate filling configuration with zeolite placed upstream of the steel slag was then proposed to eliminate the disadvantageous effects of steel slag. Experimental results showed that this novel filling configuration was superior to two other filling configurations in terms of ammonium removal.

Optimization of polyhydroxybutyrate production utilizing waste water as nutrient source by Botryococcus braunii Kütz using response surface methodology.

PubMed

Kavitha, Ganapathy; Kurinjimalar, Chidambaram; Sivakumar, Krishnan; Kaarthik, Muthukumar; Aravind, Rajamani; Palani, Perumal; Rengasamy, Ramasamy

2016-12-01

Investigations have been made to optimize various factors including pH, temperature, and substrate for enhanced polyhydroxybutyrate (PHB) production in Botryococcus braunii which serves as a pioneer for production of bioplastic (PHB). Polyhydroxybutyrate is a natural, decomposable polymers accumulated by the microorganism under different nutritional condition. Strain selection was done by staining method using Sudan black and Nile red dye. Using response surface methodology (RSM), three level- three variables Box Behnken design (BBD), the best potential combination of pH (4-11), temperature (30-50°C) and sewage waste water as substrate fed at different concentrations at 20%-100% for maximum PHB production was investigated. Maximum yield (247±0.42mg/L) of PHB dry weight was achieved from the 60% concentration of sewage waste water as a growth medium at pH 7.5 at 40°C. It was well in close agreement with the value predicted by RSM model yield (246± 0.32mg/L). Thus the study shows the production of PHB by B. braunii along with the basic characterization of PHB by using FTIR and TEM analysis. These preliminary studies indicated that PHB can also be produced by B. braunii utilizing waste water. There is no report on the optimization of PHB production in this microalgae have been documented. Copyright © 2016 Elsevier B.V. All rights reserved.

Characterization of dolichol and dolichyl phosphate phosphatase from soya beans (Glycine max).

PubMed Central

Ravi, K; Rip, J W; Carroll, K K

1983-01-01

A series of polyprenols, ranging in length from 15 to 22 isoprene units, has been isolated from soya beans (Glycine max) and purified by high-pressure liquid chromatography. N.m.r., i.r. and mass spectra of the compounds indicated that they are alpha-saturated polyprenols of the dolichol type. The amount present in dry seeds was about 9 mg/100 g, whereas dolichyl phosphate (Dol-P) was present only in trace amounts. Dol-P phosphatase activity was detected in the microsomal fraction of 5-day-old germinating soya-bean cotyledons. The Dol-P phosphatase activity was linear with respect to time and protein concentration and exhibited a broad pH optimum (pH 7-9). Triton X-100 was necessary for significant enzyme activity. Enzyme activity was slightly enhanced by EDTA, whereas dithiothreitol was without effect. An apparent Km of 5 microM was determined for Dol-P. Bivalent metal ions were not required for enzyme activity. A number of phosphorylated compounds tested as enzyme substrates (including a number of nucleoside phosphates, glucose 6-phosphate, sodium beta-glycerophosphate and Na4P2O7) did not compete with [1-3H]Dol-P as substrate. A number of phospholipids were also tested for their ability to act as Dol-P phosphatase substrates. At 1 mM concentration, phosphatidylcholine, phosphatidylethanolamine, phosphatidic acid and lysophosphatidic acid each inhibited enzymic activity. However, at 0.1 mM concentration, phosphatidylcholine and phosphatidylethanolamine were slightly stimulatory, whereas phosphatidic acid and lysophosphatidic acid were still inhibitory. Phosphatidic acid showed competitive inhibition. PMID:6311165

Activation of the proteasomes of sand dollar eggs at fertilization depends on the intracellular pH rise.

PubMed

Chiba, K; Alderton, J M; Hoshi, M; Steinhardt, R A

1999-05-01

The mechanism of the activation of intracellular proteasomes at fertilization was measured in living sand dollar eggs using the membrane-impermeant fluorogenic substrate, succinyl-Phe-Leu-Arg-coumarylamido-4-methanesulfonic acid. When the substrate was microinjected into unfertilized eggs, the initial velocity of hydrolysis of the substrate (V0) was low. V0 measured 5 to 10 min after fertilization was five to nine times the prefertilization level and remained high throughout the first cell cycle. Hydrolysis of the substrate was inhibited by clasto-lactacystin beta-lactone, a specific inhibitor of the proteasome. There has been in vitro evidence that calcium may be involved in regulation of proteasome activity to either inhibit the increase in peptidase activity associated with PA 28 binding to the 20S proteasome or stimulate activity of the PA 700-proteasome complex. Since both intracellular free Ca2+ concentration ([Ca2+]i) and intracellular pH (pHi) increase after fertilization, hydrolysis of the proteasome substrate was measured under conditions in which [Ca2+]i and pHi were varied independently during activation. When the pHi of unfertilized eggs was elevated by exposure to 15 mM ammonium chloride in pH 9 seawater, V0 increased to a level comparable to that measured after fertilization. In contrast, [Ca2+]i elevation without pHi change, induced by calcium ionophore in sodium-free seawater, had no effect on V0 in the unfertilized egg. Moreover, when unfertilized eggs were microinjected with buffers modulating pHi, V0 increased in a pH-dependent manner. These results indicate that the pHi rise at fertilization is the necessary prerequisite for activation of the proteasome, an essential component in the regulation of the cell cycle. Copyright 1999 Academic Press.

Ethanol Fermentation of Various Pretreated and Hydrolyzed Substrates at Low Initial pH

NASA Astrophysics Data System (ADS)

Kádár, Zsófia; Maltha, San Feng; Szengyel, Zsolt; Réczey, Kati; de Laat, Wim

Lignocellulosic materials represent an abundant feedstock for bioethanol production. Because of their complex structure pretreatment is necessary to make it accessible for enzymatic attack. Steam pretreatment with or without acid catalysts seems to be one of the most promising techniques, which has already been applied for large variety of lignocellulosics in order to improve enzymatic digestibility. During this process a range of toxic compounds (lignin and sugar degradation products) are formed which inhibit ethanol fermentation. In this study, the toxicity of hemicellulose hydrolysates obtained in the steam pretreatment of spruce, willow, and corn stover were investigated in ethanol fermentation tests using a yeast strain, which has been previously reported to have a resistance to inhibitory compounds generated during steam pretreatment. To overcome bacterial contamination, fermentations were carried out at low initial pH. The fermentability of hemicellulose hydrolysates of pretreated lignocellulosic substrates at low pH gave promising results with the economically profitable final 5 vol% ethanol concentration corresponding to 85% of theoretical. Adaptation experiments have shown that inhibitor tolerance of yeast strain can be improved by subsequent transfer of the yeast to inhibitory medium.

Polyelectrolyte brushes on dielectric surfaces

NASA Astrophysics Data System (ADS)

Antila, Hanne; Luijten, Erik

When chains of charged polymers are grafted to a solid surface, a polyelectrolyte (PE) brush results. These types of PE assemblies have a wide range of applications ranging from fuel cells and switchable electrodes to drug delivery. Many of these applications stem from the ability of PE brushes to respond to external stimuli: the brush properties can be tuned, for example, by varying electric field, PE grafting density, pH, salt concentration or salt valency. Accordingly, deciphering the brush behavior under different conditions has been a subject of considerable experimental, theoretical, and computational research efforts. However, the effect of the dielectric properties of the substrate on the PE brush has received much less attention. We use coarse-grained molecular dynamics simulations to show how varying the dielectric mismatch between the solvent and the substrate can significantly affect the brush. We demonstrate how tuning this mismatch can either diminish or enhance the effects of other control parameters, such as pH, on the brush properties. Furthermore, we investigate how dielectric properties of the substrate affect the brush, and the ion distribution and mobility within the brush, when the brush is exposed to an electric field.

Effect of pH of spray solution on the electrical properties of cadmium oxide thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hodlur, R. M.; Gunnagol, Raghu M.; Rabinal, M. K., E-mail: mkrabinal@yahoo.com

2015-06-24

Highly conducting transparent cadmium oxide thin films were prepared by conventional spray pyrolysis technique on glass at 375 °C substrate temperature. The pH of the spray solution was varied by adding ammonia/hydrochloric acid in the spray solution. The XRD pattern showed cubic phase. A lowest resistivity of 9.9 × 10{sup −4} Ω cm (with carrier concentration (n) = 5.1 × 10{sup 20} cm{sup −3}, mobility (µ)=12.4 cm{sup 2}/Vs) is observed for pH ∼12. The resistivity is tuned almost by three orders of magnitude by controlling the bath pH with optical transmittance more than 70 %. Thus, without any doping, the electricalmore » conductivity of CdO films could be easily tuned by simply varying the pH of spray solution without compromising the transparency and keeping the other deposition parameters fixed.« less

Use of carbonates for biological and chemical synthesis

DOEpatents

Rau, Gregory Hudson

2014-09-09

A system of using carbonates, especially water-insoluble or sparing soluble mineral carbonates, for maintaining or increasing dissolved inorganic carbon concentrations in aqueous media. In particular, the system generates concentrated dissolve inorganic carbon substrates for photosynthetic, chemosynthetic, or abiotic chemical production of carbonaceous or other compounds in solution. In some embodiments, the invention can also enhance the dissolution and retention of carbon dioxide in aqueous media, and can produce pH buffering capacity, metal ions, and heat, which can be beneficial to the preceding syntheses.

Porous cellulose as promoter of oil production by the oleaginous yeast Lipomyces starkeyi using mixed agroindustrial wastes.

PubMed

Ganatsios, Vassilios; Koutinas, Athanasios A; Bekatorou, Argyro; Panagopoulos, Vassilios; Banat, Ibrahim M; Terpou, Antonia; Kopsahelis, Nikolaos

2017-11-01

Enhanced single cell oil (SCO) production by the oleaginous yeast Lipomyces starkeyi DSM 70296, immobilised on delignified porous cellulose, is reported. Pure glucose media were initially used. The effects of substrate pH and treatment temperature were evaluated, showing that 30°C and pH 5.0 were the optimum conditions for SCO production by the immobilised yeast. The immobilisation technique led to increased lipid accumulation and cell growth by 44% and 8%, respectively, in the glucose media, compared to free cells in suspension. This positive effect was also shown when low concentration mixed agro-industrial waste suspensions were used as substrates, leading to 85% enhanced SCO production in comparison with free cells. Higher fatty acid (HFA) analysis showed that yeast immobilisation led to increased formation of unsaturated HFAs (6%) and reduced saturated HFAs (5%) compared to free cells. Copyright © 2017 Elsevier Ltd. All rights reserved.

The ANAMMOX reactor under transient-state conditions: process stability with fluctuations of the nitrogen concentration, inflow rate, pH and sodium chloride addition.

PubMed

Yu, Jin-Jin; Jin, Ren-Cun

2012-09-01

The process stability of an anaerobic ammonium oxidation (ANAMMOX) was investigated in an upflow anaerobic sludge blanket reactor subjected to overloads of 2.0- to 3.0-fold increases in substrate concentrations, inflow rates lasting 12 or 24h, extreme pH levels of 4 and 10 for 12h and a 12-h 30 g l(-1) NaCl addition. During the overloads, the nitrogen removal rate improved, and the shock period was an important factor affecting the reactor performance. In the high pH condition, the reactor performance significantly degenerated; while in the low pH condition, it did not happen. The NaCl addition caused the most serious deterioration in the reactor, which took 108 h to recover and was accompanied by a stoichiometric ratio divergence. There are well correlations between the total nitrogen and the electrical conductivity which is considered to be a convenient signal for controlling and monitoring the ANAMMOX process under transient-state conditions. Copyright © 2012 Elsevier Ltd. All rights reserved.

Development of an In Vivo and In Vitro Ileal Fermentation Method in a Growing Pig Model.

PubMed

Montoya, Carlos A; de Haas, Edward S; Moughan, Paul J

2018-02-01

Substantial microbial fermentation may occur mainly in the lower small intestine (SI) of human adults, but there is no established methodology to determine this. The study aimed to develop a combined in vivo and in vitro methodology for ileal fermentation based on the pig as an animal model for digestion in human adults. Several aspects of a combined in vivo/in vitro ileal fermentation assay were evaluated. Male 9-wk-old pigs (n = 30; mean ± SD body weight: 23 ± 1.6 kg) were fed a human-type diet (143, 508, 45, 49, and 116 g/kg dry matter diet of crude protein, starch, total lipid, ash, and total dietary fiber) for 15 d. On day 15, pigs were killed, and the last third of the SI was collected to prepare an ileal digesta-based inoculum. Terminal jejunal digesta (last 50 cm of the second third of the SI) were collected as substrate for the assay to test the form of substrate (fresh or freeze-dried), origin (location in jejunum or SI) of the substrate, storage of the inoculum, incubation time (1.2-6.8 h), pH of the medium, and inoculum concentration (6-26 mg inoculum/100 mg substrate). The group of donor pigs used to prepare the inoculum, form of the substrate, origin of the substrate, origin of the inoculum (location in the SI), storage of the inoculum, incubation time, and inoculum concentration did not influence the in vitro ileal organic matter (OM) fermentability (P > 0.05). The in vitro ileal OM fermentability decreased when the pH of the medium increased from 5.5 to 7.5 (31% to 28%; P ≤ 0.05). Predicted (in vivo/in vitro) apparent ileal OM digestibility was similar to the value measured in vivo. Thirty-percent of the terminal jejunal digesta OM was fermented in the ileum. Fiber fermentation in the ileum can be studied using the optimized in vivo/in vitro ileal fermentation method.

Adsorption of 6-mercaptopurine and 6-mercaptopurine riboside on silver colloid: a pH dependent surface enhanced Raman spectroscopy and density functional theory study. Part I. 6-Mercaptopurine

NASA Astrophysics Data System (ADS)

Szeghalmi, A. V.; Leopold, L.; Pînzaru, S.; Chis, V.; Silaghi-Dumitrescu, I.; Schmitt, M.; Popp, J.; Kiefer, W.

2005-02-01

Surface enhanced Raman spectroscopy (SERS) on silver colloid has been applied to characterize the interaction of 6-mercaptopurine (6MP), an active drug used in chemotherapy of acute lymphoblastic leukemia, with a model biological substrate at therapeutical concentrations and as function of the pH value. The adsorption active sites and molecular orientation on the metal surface have been determined on the basis of SERS 'surface selection rules' subsequent to a detailed vibrational analysis of the 6MP tautomeric forms. Therefore, DFT calculations (vibrational wavenumbers, Raman scattering activities, partial atomic charges) of the optimized tautomers and potential energy distribution calculations have been performed. Around neutral pH value reorientation of the molecule has been observed. Under basic conditions the 6MP molecule is probably adsorbed on the silver colloid through the N1 atom of the purine ring and possibly the S atom, and adopts a tilted orientation to the surface. A reduction in the number of adsorbed molecules under basic conditions is proposed, since the SERS spectrum recorded at 10-6 M concentration at neutral pH value resembles the SERS spectra obtained under basic conditions at 10-5 M concentration. At acidic pH values a stronger interaction through the N9 and N3 atoms is suggested with an end-on orientation.

CRYSTALLINE INORGANIC PYROPHOSPHATASE ISOLATED FROM BAKER'S YEAST

PubMed Central

Kunitz, M.

1952-01-01

Crystalline inorganic pyrophosphatase has been isolated from baker's yeast. The crystalline enzyme is a protein of the albumin type with an isoelectric point near pH 4.8. Its molecular weight is of the order of 100,000. It contains about 5 per cent tyrosine and 3.5 per cent tryptophane. It is most stable at pH 6.8. The new crystalline protein acts as a specific catalyst for the hydrolysis of inorganic pyrophosphate into orthophosphate ions. It does not catalyze the hydrolysis of the pyrophosphate radical of such organic esters as adenosine di- and triphosphate, or thiamine pyrophosphate. Crystalline pyrophosphatase requires the presence of Mg, Co, or Mn ions as activators. These ions are antagonized by calcium ions. Mg is also antagonized by Co or Mn ions. The rate of the enzymatic hydrolysis of inorganic pyrophosphate is proportional to the concentration of enzyme and is a function of pH, temperature, concentration of substrate, and concentration of activating ion. The approximate conditions for optimum rate are: 40°C. and pH 7.0 at a concentration of 3 to 4 x 10–3 M Na4P2O7 and an equivalent concentration of magnesium salt. The enzymatic hydrolysis of Na4P2O7 or K4P2O7 proceeds to completion and is irreversible under the conditions at which hydrolysis is occurring. Details are given of the method of isolation of the crystalline enzyme. PMID:14898026

Polyhydroxyalkanoate production as a side stream process on a municipal waste water treatment plant.

PubMed

Pittmann, T; Steinmetz, H

2014-09-01

This work describes the production of polyhydroxyalkanoates (PHAs) as a side stream process on a municipal waste water treatment plant (WWTP) at different operation conditions. Therefore various tests were conducted regarding a high PHA production and stable PHA composition. Influence of substrate concentration, temperature, pH and cycle time of an installed feast/famine-regime were investigated. The results demonstrated a strong influence of the operating conditions on the PHA production. Lower substrate concentration, 20°C, neutral pH-value and a 24h cycle time are preferable for high PHA production up to 28.4% of cell dry weight (CDW). PHA composition was influenced by cycle time only and a stable PHA composition was reached. Copyright © 2014 Elsevier Ltd. All rights reserved.

Process optimization and analysis of product inhibition kinetics of crude glycerol fermentation for 1,3-Dihydroxyacetone production.

PubMed

Dikshit, Pritam Kumar; Padhi, Susant Kumar; Moholkar, Vijayanand S

2017-11-01

In present study, statistical optimization of biodiesel-derived crude glycerol fermentation to DHA by immobilized G. oxydans cells over polyurethane foam is reported. Effect of DHA (product) inhibition on crude glycerol fermentation was analyzed using conventional biokinetic models and new model that accounts for both substrate and product inhibition. Optimum values of fermentation parameters were: pH=4.7, temperature=31°C, initial substrate concentration=20g/L. At optimum conditions, DHA yield was 89% (17.83g/L). Effect of product inhibition on fermentation was trivial for DHA concentrations ≤30g/L. At higher concentrations (≥50g/L), kinetics and yield of fermentation showed marked reduction with sharp drop in V max and K S values. Inhibition effect was more pronounced for immobilized cells due to restricted transport of fermentation mixture across polyurethane foam. Retention of fermentation mixture in immobilized matrix resulted in higher localized DHA concentration that possibly enhanced inhibition effect. Copyright © 2017 Elsevier Ltd. All rights reserved.

Steel slag raises pH of greenhouse substrates

USDA-ARS?s Scientific Manuscript database

Dolomitic lime (DL) is the primary liming agent used for increasing pH in peatmoss-based substrates. Steel slag (SS) is a byproduct of the steel manufacturing industry that has been used to elevate field soil pH. The objective of this research was to determine the pH response of a peatmoss-based g...

Development of a high-throughput liquid state assay for lipase activity using natural substrates and rhodamine B.

PubMed

Zottig, Ximena; Meddeb-Mouelhi, Fatma; Beauregard, Marc

2016-03-01

A fluorescence-based assay for the determination of lipase activity using rhodamine B as an indicator, and natural substrates such as olive oil, is described. It is based on the use of a rhodamine B-natural substrate emulsion in liquid state, which is advantageous over agar plate assays. This high-throughput method is simple and rapid and can be automated, making it suitable for screening and metagenomics application. Reaction conditions such as pH and temperature can be varied and controlled. Using triolein or olive oil as a natural substrate allows monitoring of lipase activity in reaction conditions that are closer to those used in industrial settings. The described method is sensitive over a wide range of product concentrations and offers good reproducibility. Copyright © 2015 Elsevier Inc. All rights reserved.

Relative effect of temperature and pH on diel cycling of dissolved trace elements in prickly pear creek, Montana

USGS Publications Warehouse

Jones, Clain A.; Nimick, D.A.; McCleskey, R. Blaine

2004-01-01

Diel (24 hr) cycles in dissolved metal and As concentrations have been documented in many northern Rocky Mountain streams in the U.S.A. The cause(s) of the cycles are unknown, although temperature- and pH-dependent sorption reactions have been cited as likely causes. A light/dark experiment was conducted to isolate temperature and pH as variables affecting diel metal cycles in Prickly Pear Creek, Montana. Light and dark chambers containing sediment and a strand of macrophyte were placed in the stream to simulate instream temperature oscillations. Photosynthesis-induced pH changes were allowed to proceed in the light chambers while photosynthesis was prevented in the dark chambers. Water samples were collected periodically for 22 hr in late July 2001 from all chambers and the stream. In the stream, dissolved Zn concentrations increased by 300% from late afternoon to early morning, while dissolved As concentrations exhibited the opposite pattern, increasing 33% between early morning and late afternoon. Zn and As concentrations in the light chambers showed similar, though less pronounced, diel variations. Conversely, Zn and As concentrations in the dark chambers had no obvious diel variation, indicating that light, or light-induced reactions, caused the variation. Temperature oscillations were nearly identical between light and dark chambers, strongly suggesting that temperature was not controlling the diel variations. As expected, pH was negatively correlated (P < 0.01) with dissolved Zn concentrations and positively correlated with dissolved As concentrations in both the light and dark chambers. From these experiments, photosynthesis-induced pH changes were determined to be the major cause of the diel dissolved Zn and As cycles in Prickly Pear Creek. Further research is necessary in other streams to verify that this finding is consistent among streams having large differences in trace-element concentrations and mineralogy of channel substrate. ?? 2004 Kluwer Academic Publishers.

[Optimization of process of icraiin be hydrolyzed to Baohuoside I by cellulase based on Plackett-Burman design combined with CCD response surface methodology].

PubMed

Song, Chuan-xia; Chen, Hong-mei; Dai, Yu; Kang, Min; Hu, Jia; Deng, Yun

2014-11-01

To optimize the process of Icraiin be hydrolyzed to Baohuoside I by cellulase by Plackett-Burman design combined with Central Composite Design (CCD) response surface methodology. To select the main influencing factors by Plackett-Burman design, using CCD response surface methodology to optimize the process of Icraiin be hydrolyzed to Baohuoside I by cellulase. Taking substrate concentration, the pH of buffer and reaction time as independent variables, with conversion rate of icariin as dependent variable,using regression fitting of completely quadratic response surface between independent variable and dependent variable,the optimum process of Icraiin be hydrolyzed to Baohuoside I by cellulase was intuitively analyzed by 3D surface chart, and taking verification tests and predictive analysis. The best enzymatic hydrolytic process was as following: substrate concentration 8. 23 mg/mL, pH 5. 12 of buffer,reaction time 35. 34 h. The optimum process of Icraiin be hydrolyzed to Baohuoside I by cellulase is determined by Plackett-Burman design combined with CCD response surface methodology. The optimized enzymatic hydrolytic process is simple, convenient, accurate, reproducible and predictable.

A general synthetic strategy and the anti-proliferation properties on prostate cancer cell lines for natural phenylethanoid glycosides.

PubMed

Mulani, Shaheen K; Guh, Jih-Hwa; Mong, Kwok-Kong Tony

2014-05-14

A general strategy for the synthesis of phenylethanoid glycosides (PhG) including echinacoside 1, acteoside 2, calceolarioside-A 3 and calceolarioside-B 4 is reported. The strategy features the application of low substrate concentration glycosylation and N-formyl morpholine modulated glycosylation methods for the construction of 1,2-trans β- and α-glycosidic bonds. The reported strategy does not invoke the use of the participatory acyl protecting function, which is incompatible with the ester function present in target PhG compounds. A preliminary study of the anti-proliferation properties of the PhG compounds 1–4 was performed; the acteoside 2 exhibited the best inhibition on the prostatic cancer cell proliferation.

Detection of mercury compounds using invertase-glucose oxidase-based biosensor

NASA Astrophysics Data System (ADS)

Amine, A.; Cremisini, C.; Palleschi, G.

1995-10-01

Mercury compounds have been determined with an electrochemical biosensor based on invertase inhibition. When invertase is in the presence of mercury its activity decreases; this causes a decrease of glucose production which is monitored by the glucose sensor and correlated to the concentration of mercury in solution. Parameters as pH, enzyme concentration, substrate concentration, and reaction and incubation time were optimized. Mercury compounds determination using soluble or immobilized invertase were reported. Results show that the inhibition was competitive and reversible. Mercury compounds can be detected directly in aqueous solution in the range 2 - 10 ppb.

One-pot conjugated linoleic acid production from castor oil by Rhizopus oryzae lipase and resting cells of Lactobacillus plantarum.

PubMed

Khaskheli, Abid Ali; Talpur, Farah Naz; Cebeci Aydin, Aysun; Jawaid, Sana; Surhio, Muhammad Ali; Afridi, Hassan Imran

2017-10-01

Conjugated linoleic acid (CLA) has attracted as novel type of fatty acids having unusual health-promoting properties such as anticarcinogenic and antiobesitic effects. The present work employed castor oil as substrate for one-pot production of CLA using washed cells of Lactobacillus plantarum (L. plantarum) and lipases as catalysts. Among the screened lipases, the lipase Rhizopus oryzae (ROL) greatly assisted resting cells to produce CLA. Mass spectral analysis of the product showed that two major isomers of CLA were produced in the reaction mixture i.e. cis-9, trans-11 56.55% and trans-10, cis-12 43.45%. Optimum factors for CLA synthesis were found as substrate concentration (8 mg/mL), pH (6.5), washed cell concentration (12% w/v), and incubation time of 20 h. Hence, the combination of ROL with L. plantarum offers one pot production of CLA selectively using castor oil as a cost-effective substrate.

Maximizing the production of butyric acid from food waste as a precursor for ABE-fermentation.

PubMed

Stein, Ullrich Heinz; Wimmer, B; Ortner, M; Fuchs, W; Bochmann, G

2017-11-15

The current study reports on the maximization of butyric acid production from food waste using a mixed microbial fermentation. In semi-continuous fermentations the effect of three different pH values (5.5, 7.0 and 9.0), three different temperatures (37°C, 55°C and 70°C) and two levels of hydraulic retention time (HRT, 2days and 6days) on the formation of butyric acid as well as total volatile fatty acid production (tVFA) were investigated. Overall, pH5.5 provided the lowest butyric acid concentrations regardless of the temperature and the HRT. At mesophilic temperature (37°C) alkaline conditions (pH9.0) lead to a strong incline of tVFA as well as butyric acid concentration probably due to a decreased solubilization of the substrate. However, most efficient in terms of butyric acid production was the fermentation conducted at 55°C and pH7 where a butyric acid concentrations of 10.55g/L (HRT 2days) and 13.00g/L (HRT 6days) were achieved. Additional experiments at 70°C showed declining butyric acid production. Increase of the HRT from 2days to 6days provided an increment of butyric acid concentration throughout almost all experimental settings. However, regarding volumetric productivity the increase in concentration does not compensate for the bigger reactor volume required to establish a higher HRT. At pH7 and 55°C the resulting volumetric production rates were 5.27g/L∗d at a HRT 2days and only 2.17g/L∗d at a HRT of 6days. Copyright © 2017 Elsevier B.V. All rights reserved.

Enzyme biosensor systems based on porous silicon photoluminescence for detection of glucose, urea and heavy metals.

PubMed

Syshchyk, Olga; Skryshevsky, Valeriy A; Soldatkin, Oleksandr O; Soldatkin, Alexey P

2015-04-15

A phenomenon of changes in photoluminescence of porous silicon at variations in medium pH is proposed to be used as a basis for the biosensor system development. The method of conversion of a biochemical signal into an optical one is applied for direct determination of glucose and urea as well as for inhibitory analysis of heavy metal ions. Changes in the quantum yield of porous silicon photoluminescence occur at varying pH of the tested solution due to the enzyme-substrate reaction. When creating the biosensor systems, the enzymes urease and glucose oxidase (GOD) were used as a bioselective material; their optimal concentrations were experimentally determined. It was shown that the photoluminescence intensity of porous silicon increased by 1.7 times when increasing glucose concentration in the GOD-containing reaction medium from 0 to 3.0mM, and decreased by 1.45 times at the same increase in the urea concentration in the urease-containing reaction medium. The calibration curves of dependence of the biosensor system responses on the substrate concentrations are presented. It is shown that the presence of heavy metal ions (Cu(2+), Pb(2+), and Cd(2+)) in the tested solution causes an inhibition of the enzymatic reactions catalyzed by glucose oxidase and urease, which results in a restoration of the photoluminescence quantum yield of porous silicon. It is proposed to use this effect for the inhibitory analysis of heavy metal ions. Copyright © 2014 Elsevier B.V. All rights reserved.

Characterization of the respiration-induced yeast mitochondrial permeability transition pore.

PubMed

Bradshaw, Patrick C; Pfeiffer, Douglas R

2013-12-01

When isolated mitochondria from the yeast Saccharomyces cerevisiae oxidize respiratory substrates in the absence of phosphate and ADP, the yeast mitochondrial unselective channel, also called the yeast permeability transition pore (yPTP), opens in the inner membrane, dissipating the electrochemical gradient. ATP also induces yPTP opening. yPTP opening allows mannitol transport into isolated mitochondria of laboratory yeast strains, but mannitol is not readily permeable through the yPTP in an industrial yeast strain, Yeast Foam. The presence of oligomycin, an inhibitor of ATP synthase, allowed for respiration-induced mannitol permeability in mitochondria from this strain. Potassium (K+) had varied effects on the respiration-induced yPTP, depending on the concentration of the respiratory substrate added. At low respiratory substrate concentrations K+ inhibited respiration-induced yPTP opening, while at high substrate concentrations this effect diminished. However, at the high respiratory substrate concentrations, the presence of K+ partially prevented phosphate inhibition of yPTP opening. Phosphate was found to inhibit respiration-induced yPTP opening by binding a site on the matrix space side of the inner membrane in addition to its known inhibitory effect of donating protons to the matrix space to prevent the pH change necessary for yPTP opening. The respiration-induced yPTP was also inhibited by NAD, Mg2+, NH4 + or the oxyanion vanadate polymerized to decavanadate. The results demonstrate similar effectors of the respiration-induced yPTP as those previously described for the ATP-induced yPTP and reconcile previous strain-dependent differences in yPTP solute selectivity. Copyright © 2013 John Wiley & Sons, Ltd.

Risk analysis of the thermal sterilization process. Analysis of factors affecting the thermal resistance of microorganisms.

PubMed

Akterian, S G; Fernandez, P S; Hendrickx, M E; Tobback, P P; Periago, P M; Martinez, A

1999-03-01

A risk analysis was applied to experimental heat resistance data. This analysis is an approach for processing experimental thermobacteriological data in order to study the variability of D and z values of target microorganisms depending on the deviations range of environmental factors, to determine the critical factors and to specify their critical tolerance. This analysis is based on sets of sensitivity functions applied to a specific case of experimental data related to the thermoresistance of Clostridium sporogenes and Bacillus stearothermophilus spores. The effect of the following factors was analyzed: the type of target microorganism; nature of the heating substrate; pH, temperature; type of acid employed and NaCl concentration. The type of target microorganism to be inactivated, the nature of the substrate (reference or real food) and the heating temperature were identified as critical factors, determining about 90% of the alteration of the microbiological risk. The effect of the type of acid used for the acidification of products and the concentration of NaCl can be assumed to be negligible factors for the purposes of engineering calculations. The critical non-uniformity in temperature during thermobacteriological studies was set as 0.5% and the critical tolerances of pH value and NaCl concentration were 5%. These results are related to a specific case study, for that reason their direct generalization is not correct.

Yeast hexokinase: substrate-induced association--dissociation reactions in the binding of glucose to hexokinase P-II.

PubMed

Hoggett, J G; Kellett, G L

1976-06-15

A method is described for the purification of native hexokinases P-I and P-II from yeast using preparative isoelectric focussing to separate the isozymes. The binding of glucose to hexokinase P-II, and the effect of this on the monomer--dimer association--dissociation reaction have been investigated quantitatively by a combination of titrations of intrinsic protein fluorescence and equilibrium ultracentrifugation. Association constants for the monomer-dimer reaction decreased with increasing pH, ionic strength and concentration of glucose. Saturating concentrations of glucose did not bring about complete dissociation of the enzyme showing that both sites were occupired in the dimer. At pH 8.0 and high ionic strength, where the enzyme existed as monomer, the dissociation constant of the enzyme-glucose complex was 3 X 10(-4) mol 1(-1) and was independent of the concentration of enzyme. Binding to the dimeric form at low pH and ionic strength (I=0.02 mol 1(-1), pH less than 7.5) was also independent of enzyme concentration (in the range 10-1000 mug ml-1) but was much weaker. The process could be described by a single dissociation constant, showing that the two available sites on the dimer were equivalent and non-cooperative; values of the intrinsic dissociation constant varied from 2.5 X 10(-3) mol 1(-1) at pH 7.0 to 6 X 10(-3) at pH 6.5. Under intermediate conditions (pH 7.0, ionic strength=0.15 mol 1(-1)), where monomer and dimer coexisted, the binding of glucose showed weak positive cooperatively (Hill coefficient 1.2); in addition, the binding was dependent upon the concentration of enzyme in the direction of stronger binding at lower concentrations. The results show that the phenomenon of half-sites reactivity observed in the binding of glucose to crystalline hexokinase P-II does not occur in solution; the simplest explanation of our finding the two sites to be equivalent is that the dimer results from the homologous association of two identical subunits.

[Effects of dissolved oxygen and pH on Candida utilis batch fermentation of glutathione].

PubMed

Wei, Gong-Yuan; Li, Yin; Du, Guo-Cheng; Chen, Jian

2003-11-01

The effects of dissolved oxygen (DO) and pH on glutathione batch fermentation by Candida utilis WSH-02-08 in a 7 liters stirred fermentor were investigated. It was shown that DO concentration is an important factor in glutathione production. With the initial glucose concentration of 30 g/L and a 5 L/min air flow rate, and the agitation rate less than 250 r/min, the DO concentration was not sufficient to satisfy the oxygen requirement during the fermentation. With an agitation rate of more than 300 r/min, the cell growth and glutathione production were enhanced significantly, with the dry cell mass and glutathione production were 20% and 25% higher than that at 200 r/min. When C. utilis WSH 02-08 was cultivated in a batch process without pH control, cell growth and glutathione production were inhibited, likely due to a dramatic decrease in the pH. Intracellular glutathione leakages were observed when the pH was 1.5 or less. To assess the effect of pH on glutathione production, six batch processes controlled at pH 4.0, 4.5, 5.0, 5.5, 6.0 and 6.5 were conducted. The yield was highest at pH 5.5, when the dry cell mass and yield were 27% and 95% respectively higher than fermentation without pH control. The maximal intracellular glutathione content (2.15 %) was also achieved at the pH. To improve our understandings on the effect of pH on the batch glutathione production, a modified Logistic equation and Luedeking-Piret equation were used to simulate cell growth and glutathione production, respectively, under different pH. Based on the parameters obtained by the nonlinear estimation, kinetic analysis was performed to elucidate the effect of pH on the batch glutathione production. The process controlled at pH 5.5 was proven to be the best due to the higher value of K(I) (substrate inhibitory constant in the Logistic equation), lower value of a and higher value of beta (slope and intercept in the Luedeking-Piret equation, respectively).

Laccase-catalyzed removal of 2,4-dimethylphenol from synthetic wastewater: effect of polyethylene glycol and dissolved oxygen.

PubMed

Ghosh, J P; Taylor, K E; Bewtra, J K; Biswas, N

2008-04-01

The potential use of laccase (SP-504) in an advanced oxidation-based treatment technology to remove 2,4-dimethylphenol (DMP) from water was investigated with and without the additive, polyethylene glycol (PEG). The DMP concentration was varied between 1.0 and 5.0 mM. The optimization of pH and enzyme concentration in the presence and absence of PEG was carried out. All experiments were carried out in continuously stirred reactors for 3h at room temperature. The reaction was initiated by adding enzyme to the reaction mixture. For more than 95% removal of DMP, the presence of PEG reduced the inactivation of enzyme so that the required enzyme concentrations were reduced by about 2-fold compared to the same reactions in the absence of PEG. Finally, the PEG concentrations were optimized to obtain the minimum dose required. For higher substrate concentrations, the availability of oxygen was insufficient in achieving 95% or more removal. Therefore, the effect of increasing dissolved oxygen at higher substrate concentration was investigated. The laccase studied was capable of efficiently removing DMP at very low enzyme concentrations and hence shows great potential for cost-effective industrial applications.

Relationship of Cell Sap pH to Organic Acid Change During Ion Uptake 1

PubMed Central

Hiatt, A. J.

1967-01-01

Excised roots of barley (Hordeum vulgare, var. Campana) were incubated in KCl, K2SO4, CaCl2, and NaCl solutions at concentrations of 10−5 to 10−2 n. Changes in substrate solution pH, cell sap pH, and organic acid content of the roots were related to differences in cation and anion absorption. The pH of expressed sap of roots increased when cations were absorbed in excess of anions and decreased when anions were absorbed in excess of cations. The pH of the cell sap shifted in response to imbalances in cation and anion uptake in salt solutions as dilute as 10−5 n. Changes in cell sap pH were detectable within 15 minutes after the roots were placed in 10−3 n K2SO4. Organic acid changes in the roots were proportional to expressed sap pH changes induced by unbalanced ion uptake. Changes in organic acid content in response to differential cation and anion uptake appear to be associated with the low-salt component of ion uptake. PMID:16656506

Volatile fatty acids production from marine macroalgae by anaerobic fermentation.

PubMed

Pham, Thi Nhan; Nam, Woo Joong; Jeon, Young Joong; Yoon, Hyon Hee

2012-11-01

Volatile fatty acids (VFAs) were produced from the marine macroalgae, Laminaria japonica, Pachymeniopsis elliptica, and Enteromorpha crinite by anaerobic fermentation using a microbial community derived from a municipal wastewater treatment plant. Methanogen inhibitor (iodoform), pH control, substrate concentration, and alkaline and thermal pretreatments affected VFA productivity. Acetic, propionic, and butyric acids were the main products. A maximum VFA concentration of 15.2g/L was obtained from 50 g/L of L. japonica in three days at 35°C and pH 6.5-7.0. Pretreatment with 0.5 N NaOH improved VFA productivity by 56% compared to control. The result shows the applicability of marine macroalgae as biomass feedstock for the production of VFAs which can be converted to mixed alcohol fuels. Copyright © 2012 Elsevier Ltd. All rights reserved.

Optimized Production of Xylitol from Xylose Using a Hyper-Acidophilic Candida tropicalis.

PubMed

Tamburini, Elena; Costa, Stefania; Marchetti, Maria Gabriella; Pedrini, Paola

2015-08-19

The yeast Candida tropicalis DSM 7524 produces xylitol, a natural, low-calorie sweetener, by fermentation of xylose. In order to increase xylitol production rate during the submerged fermentation process, some parameters-substrate (xylose) concentration, pH, aeration rate, temperature and fermentation strategy-have been optimized. The maximum xylitol yield reached at 60-80 g/L initial xylose concentration, pH 5.5 at 37 °C was 83.66% (w/w) on consumed xylose in microaerophilic conditions (kLa = 2·h(-1)). Scaling up on 3 L fermenter, with a fed-batch strategy, the best xylitol yield was 86.84% (w/w), against a 90% of theoretical yield. The hyper-acidophilic behaviour of C. tropicalis makes this strain particularly promising for industrial application, due to the possibility to work in non-sterile conditions.

Optimized Production of Xylitol from Xylose Using a Hyper-Acidophilic Candida tropicalis

PubMed Central

Tamburini, Elena; Costa, Stefania; Marchetti, Maria Gabriella; Pedrini, Paola

2015-01-01

The yeast Candida tropicalis DSM 7524 produces xylitol, a natural, low-calorie sweetener, by fermentation of xylose. In order to increase xylitol production rate during the submerged fermentation process, some parameters-substrate (xylose) concentration, pH, aeration rate, temperature and fermentation strategy-have been optimized. The maximum xylitol yield reached at 60–80 g/L initial xylose concentration, pH 5.5 at 37 °C was 83.66% (w/w) on consumed xylose in microaerophilic conditions (kLa = 2·h−1). Scaling up on 3 L fermenter, with a fed-batch strategy, the best xylitol yield was 86.84% (w/w), against a 90% of theoretical yield. The hyper-acidophilic behaviour of C. tropicalis makes this strain particularly promising for industrial application, due to the possibility to work in non-sterile conditions. PMID:26295411

The crystallogenesis of a human estradiol dehydrogenase-substrate complex

NASA Astrophysics Data System (ADS)

Zhu, Dao-Wei; Azzi, Arezki; Rehse, Peter; Lin, Sheng-Xiang

1996-10-01

Human 17β-hydroxysteroid dehydrogenase type 1 is an important steroidogenic enzyme catalyzing the synthesis of the most active estrogen: estradiol. The enzyme is formed by two identical subunits (34.5 kDa). In this paper, we report the preparation of a stoichiometric 17β-HSD1-estradiol complex sample at a much higher concentration than the solubility of the free substrate, using a gradual concentration of the enzyme-substrate mixture starting at low concentration. The complex is successfully crystallized by vapor diffusion at pH 7.5 with polyethyleneglycol 4000 as the precipitating agent. The space group is C2 with a = 123.56 Å, b = 45.21 Å, c = 61.30 Å and β = 99.06°. There is one monomer in the asymmetric unit and two molecules of the enzyme in a unit cell. A diffraction data set to 2.5 Å has been collected to 86% completeness on native crystals. The high quality of the electronic density map of estradiol supports the full occupancy of the binding site, thus confirming the efficiency of the complex preparation. This method will also be useful in crystallizing other steroid-dehydrogenase complexes.

Experimental design approach applied to the elimination of crystal violet in water by electrocoagulation with Fe or Al electrodes.

PubMed

Durango-Usuga, Paula; Guzmán-Duque, Fernando; Mosteo, Rosa; Vazquez, Mario V; Peñuela, Gustavo; Torres-Palma, Ricardo A

2010-07-15

An experimental design methodology was applied to evaluate the decolourization of crystal violet (CV) dye by electrocoagulation using iron or aluminium electrodes. The effects and interactions of four parameters, initial pH (3-9), current density (6-28 A m(-2)), substrate concentration (50-200 mg L(-1)) and supporting electrolyte concentration (284-1420 mg L(-1) of Na(2)SO(4)), were optimized and evaluated. Although the results using iron anodes were better than for aluminium, the effects and interactions of the studied parameters were quite similar. With a confidence level of 95%, initial pH and supporting electrolyte concentration showed limited effects on the removal rate of CV, whereas current density, pollutant concentration and the interaction of both were significant. Reduced models taking into account significant variables and interactions between variables have shown good correlations with the experimental results. Under optimal conditions, almost complete removal of CV and chemical oxygen demand were obtained after electrocoagulation for 5 and 30 min, using iron and aluminium electrodes, respectively. These results indicate that electrocoagulation with iron anodes is a rapid, economical and effective alternative to the complete removal of CV in waters. Evolutions of pH and residual iron or aluminium concentrations in solution are also discussed. 2010 Elsevier B.V. All rights reserved.

Single molecule force measurements delineate salt, pH and surface effects on biopolymer adhesion

NASA Astrophysics Data System (ADS)

Pirzer, T.; Geisler, M.; Scheibel, T.; Hugel, T.

2009-06-01

In this paper we probe the influence of surface properties, pH and salt on the adhesion of recombinant spider silk proteins onto solid substrates with single molecule force spectroscopy. A single engineered spider silk protein (monomeric C16 or dimeric (QAQ)8NR3) is covalently bound with one end to an AFM tip, which assures long-time measurements for hours with one and the same protein. The tip with the protein is brought into contact with various substrates at various buffer conditions and then retracted to desorb the protein. We observe a linear dependence of the adhesion force on the concentration of three selected salts (NaCl, NaH2PO4 and NaI) and a Hofmeister series both for anions and cations. As expected, the more hydrophobic C16 shows a higher adhesion force than (QAQ)8NR3, and the adhesion force rises with the hydrophobicity of the substrate. Unexpected is the magnitude of the dependences—we never observe a change of more than 30%, suggesting a surprisingly well-regulated balance between dispersive forces, water-structure-induced forces as well as co-solute-induced forces in biopolymer adhesion.

Saccharification of sunflower stalks using lignocellulases from a fungal consortium comprising Pholiota adiposa and Armillaria gemina.

PubMed

Ramachandran, Priyadharshini; Kim, Tae-Su; Dhiman, Saurabh Sudha; Li, Jinglin; Park, Ji-Hyun; Choi, Joon-Ho; Kim, Jae Young; Kim, Dongwook; Lee, Jung-Kul

2015-09-01

Lignocellulases from Armillaria gemina and Pholiota adiposa are efficient in hydrolyzing aspen and poplar biomass, respectively. In the present study, lignocellulosic enzymes obtained from a fungal consortium comprising P. adiposa and A. gemina were used for the saccharification of sunflower stalks. Sunflower stalks were thermochemically pretreated using 2 % NaOH at 50 °C for 24 h. The saccharification process parameters including substrate concentration, enzyme loading, pH, and temperature were optimized using response surface methodology to improve the saccharification yield. The highest enzymatic hydrolysis (84.3 %) was obtained using the following conditions: enzyme loading 10 FPU/g-substrate, substrate 5.5 %, temperature 50 °C, and pH 4.5. The hydrolysis yield obtained using the enzymes from the fungal consortium was equivalent to that obtained using a mixture of commercial enzymes Celluclast and Novozyme β-glucosidase. Addition of up to 500 ppm of heavy metal ions (As, Cu, Fe, Mn, Ni, Pb, and Zn) during saccharification did not significantly affect the saccharification yield. Thus, the biomass grown for phytoremediation of heavy metals can be used for the production of reducing sugars followed by ethanol fermentation.

Branched-chain amino acid transport in Streptococcus mutans Ingbritt.

PubMed

Dashper, S G; Reynolds, E C

1993-06-01

Leucine transport in glucose-energized cells of Streptococcus mutans exhibited Michaelis-Menten-type kinetics at low extracellular concentrations, with a K1 of 15.3 microM and a Vmax of 6.1 nmol/mg dry weight/min. At high extracellular leucine concentrations, the transmembrane diffusion of leucine was not saturable, indicating that passive diffusion becomes a significant mechanism of leucine transmembrane movement under these conditions. The proton motive force (PMF) was measured in glucose-energized cells of S. mutans and was found to have a maximum value of 126 mV at an extracellular pH (pH0) of 5.0; this decreased to 45 mV at pH0 8.0. The intracellular accumulation of leucine was significantly correlated with the magnitude of the PMF. The addition of excess isoleucine or valine caused a marked decrease in the leucine transport rate. Maximal rates of leucine transport occurred at pH0 6.0, and the rate of leucine transport was independent of the growth medium. The results suggest that there is a PMF-driven, branched-chain amino acid carrier in S. mutans with a proton: substrate stoichiometry of 1.

Free Energy Simulations of Ligand Binding to the Aspartate Transporter GltPh

PubMed Central

Heinzelmann, Germano; Baştuğ, Turgut; Kuyucak, Serdar

2011-01-01

Glutamate/Aspartate transporters cotransport three Na+ and one H+ ions with the substrate and countertransport one K+ ion. The binding sites for the substrate and two Na+ ions have been observed in the crystal structure of the archeal homolog GltPh, while the binding site for the third Na+ ion has been proposed from computational studies and confirmed by experiments. Here we perform detailed free energy simulations of GltPh, giving a comprehensive characterization of the substrate and ion binding sites, and calculating their binding free energies in various configurations. Our results show unequivocally that the substrate binds after the binding of two Na+ ions. They also shed light into Asp/Glu selectivity of GltPh, which is not observed in eukaryotic glutamate transporters. PMID:22098736

Thermostable, alkaline and detergent-tolerant lipase from a newly isolated thermophilic Bacillus stearothermophilus.

PubMed

Ben Bacha, Abir; Moubayed, Nadine M S; Abid, Islam

2015-04-01

Lipases are the enzymes of choice for laundry detergent industries, owing to their triglyceride removing ability from the soiled fabric, which eventually reduces the usage of phosphate-based chemical cleansers in the detergent formulation. In this study, a novel thermo-alkaline lipase-producing strain identified as Bacillus stearothermophilus was isolated from the soil samples of olive oil mill. Enhanced lipase production was observed at 55 degrees C, pH 11 and after 48 h of incubation. Among the substrates tested, xylose (a carbon source), peptone (a nitrogen source) and olive oil at a concentration of 1% were suitable substrates for enhancing lipase production. MgSO4 and Tween-80 were suitable substrates for maximizing lipase production. The enzyme was purified to homogeneity by a single CM-Sephadex column chromatography and revealed molecular mass of 67 kDa. The enzyme (BL1) was active over a wide range of pH from 9.0 to 13.0, with an optimum at pH 11.0, exhibited maximal activity at 55 degreesC and retained more than 70% of its activity after incubation at 70 degrees C or pH 13 for 0.5 h or 24 h, respectively. The enzyme hydrolyzed both short and long-chain triacylglycerols at comparable rates. BL1 was studied in a preliminary evaluation for use in detergent formulation solutions. This novel lipase showed extreme stability towards non-ionic and anionic surfactants after pre-incubation for 1 h at 40 degrees C, and good stability towards oxidizing agents. Additionally, the enzyme showed excellent stability and compatibility with various commercial detergents, suggesting its potential as an additive in detergent formulations.

Cadmium (II) removal mechanisms in microbial electrolysis cells.

PubMed

Colantonio, Natalie; Kim, Younggy

2016-07-05

Cadmium is a toxic heavy metal, causing serious environmental and human health problems. Conventional methods for removing cadmium from wastewater are expensive and inefficient for low concentrations. Microbial electrolysis cells (MECs) can simultaneously treat wastewater, produce hydrogen gas, and remove heavy metals with low energy requirements. Lab-scale MECs were operated to remove cadmium under various electric conditions: applied voltages of 0.4, 0.6, 0.8, and 1.0 V; and a fixed cathode potential of -1.0 V vs. Ag/AgCl. Regardless of the electric condition, rapid removal of cadmium was demonstrated (50-67% in 24 h); however, cadmium concentration in solution increased after the electric current dropped with depleted organic substrate under applied voltage conditions. For the fixed cathode potential, the electric current was maintained even after substrate depletion and thus cadmium concentration did not increase. These results can be explained by three different removal mechanisms: cathodic reduction; Cd(OH)2 precipitation; and CdCO3 precipitation. When the current decreased with depleted substrates, local pH at the cathode was no longer high due to slowed hydrogen evolution reaction (2H(+)+2e(-)→H2); thus, the precipitated Cd(OH)2 and CdCO3 started dissolving. To prevent their dissolution, sufficient organic substrates should be provided when MECs are used for cadmium removal. Copyright © 2016 Elsevier B.V. All rights reserved.

Observation of the retarded transportation of a photogenerated hole on epitaxial graphene.

PubMed

Wang, Shujie; Yuan, Xizhi; Bi, Xiaofeng; Wang, Xiaomei; Huang, Qingsong

2015-10-07

Graphene is usually adopted as an assistant additive for catalysts in photocatalytic processes, because of its ability to accelerate the separation of photogenerated charge carriers. To elucidate the mechanism, hydrogen peroxide is adopted to convert the O2(-)˙ active species into OH˙ for degradation of an organic dye. If the pH value is less than 7, the concentration of the OH˙ species can be reduced more quickly with the addition of graphene than without, because negatively charged electrons can be transported quickly on graphene. If the pH value is larger than 7, the concentration of OH˙ can be promoted by the catalyst SiC with photogenerated h(+) release and reaction with OH(-), however the concentration is reduced if the SiC catalyst is covered by a graphene sheet, as it retards h(+) release from the SiC substrate. Our findings have provided a certification for the role of graphene in photo-catalytic processes.

Protease production by fermentation of fish solubles from salmon canning processes.

PubMed

Wah-On, H C; Branion, R M; Strasdine, G A

1980-09-01

Production of protease by fermentation, using Sorangium 495, of a substrate based on condensed fish solubles is demonstrated. The effects of carbohydrate addition, pH, fish solubles concentration, scale-up, agitation, and air flow rate on protease yields are described. While the fish solubles medium alone could give rise to measurable yields of protease, these were, at worst, doubled when 1% glucose was added to the medium. pH 7 was optimal for protease yield. Although the concentration of fish solubles in the basic medium showed no significant effect on cell yield, maximum protease yield was observed at a protein concentration equivalent to 3.85 mg/mL of bovine serum albumin. Protease production rates decreased as medium protein fermentor showed no significant effect on maximum protease yields. The effects of agitator speed and air flow rate on protease yield suggested that the rate of O2 transfer from air to medium could limit the rate of protease production. It was also noted that protease production is not growth associated.

Application of concrete surfaces as novel substrate for immobilization of TiO2 nano powder in photocatalytic treatment of phenolic water.

PubMed

Delnavaz, Mohammad; Ayati, Bita; Ganjidoust, Hossein; Sanjabi, Sohrab

2015-01-01

In this study, concrete application as a substrate for TiO2 nano powder immobilization in heterogeneous photocatalytic process was evaluated. TiO2 immobilization on the pervious concrete surface was done by different procedures containing slurry method (SM), cement mixed method (CMM) and different concrete sealer formulations. Irradiation of TiO2 was prepared by UV-A and UV-C lamps. Phenolic wastewater was selected as a pollutant and efficiency of the process was determined in various operation conditions including influent phenol concentration, pH, TiO2 concentration, immobilization method and UV lamp intensity. The removal efficiency of photocatalytic process in 4 h irradiation time and phenol concentration ranges of 25-500 mg/L was more than 80 %. Intermediates were identified by GC/Mass and spectrophotometric analysis. According to the results, photocatalytic reactions followed the pseudo-first-order kinetics and can effectively treate phenol under optimal conditions.

The use of metalorganics in the preparation of semiconductor materials. VIII - Feasibility studies of the growth of Group III-Group V compounds of boron by MOCVD

NASA Technical Reports Server (NTRS)

Manasevit, H. M.; Hewitt, W. B.; Nelson, A. J.; Mason, A. R.

1989-01-01

The MOCVD growth of B-As and B-P films on Si, sapphire, and Si-on-sapphire substrates is described; in this process, trimethylborane (TMB) or triethylborane (TEB) is pyrolyzed in the presence of AsH3 or PH3 in an H2 atmosphere. The procedures employed are outlined, and the results are presented in graphs, tables, and micrographs. It is found that the growth rate of the primarily amorphous films is dependent on the TMB or TEB concentration but approximately constant for TEB and AsH3 at 550-900 C. The nominal compositions of films grown using TMB are given as B(12-16)As2 and B(1-1.3)P. Carbon impurities and significant stress, bowing, and crazing are observed in the films grown on Si substrates, with the highest carbon content in the films grown from TMB and PH3.

Ameliorating effects of industrial sugar residue on the Jales gold mine spoil (NE Portugal) using Holcus lanatus and Phaseolus vulgaris as indicators.

PubMed

Bleeker, P M; Teiga, P M; Santos, M H; de Koe, T; Verkleij, J A C

2003-01-01

Phytostabilisation of bare heavily contaminated substrate, such as abandoned mine sites, is considered a very appropriate technology in order to diminish erosion and dispersion of contaminants into the surroundings. In this short-term pot study, application of industrial sugar residue (ISR), a waste product of the sugar industry, proved to ameliorate spoils conditions for plant performance by elevating pH and immobilising several metals. Although arsenate concentrations were positively correlated to spoil pH and spoil treatment with ISR mobilised As, growth of both Phaseolus vulgaris and Holcus lanatus improved significantly after applications of 3.75 g ISR kg(-1) dry spoil. Nutrient uptake from the substrate, with the exception of potassium, was elevated by ISR. As a remediation technique ISR application could be effective although in As-contaminated sites application might be restricted to areas where leaching to (ground) water does not form a risk.

Optimization of Levan Production by Cold-Active Bacillus licheniformis ANT 179 and Fructooligosaccharide Synthesis by Its Levansucrase.

PubMed

Xavier, Janifer Raj; Ramana, Karna Venkata

2017-03-01

Fructooligosaccharides (FOS) and levan attract much attention due to a wide range of applications in food technology and pharmaceutical and cosmetic industry. Bacillus licheniformis ANT 179, isolated from Antarctica soil, produced levansucrase and levan in a medium containing sucrose as carbon substrate. In this study, characterization of levansucrase and production of short-chain FOS and levan were investigated. Temperature and pH optimum of the enzyme were found to be 60 °C and pH 6.0, respectively. The optimization of fermentation conditions for levan production using sugarcane juice by response surface methodology (RSM) was carried out. Central composite rotatable design was used to study the main and the interactive effects of medium components: sugarcane juice and casein peptone concentration on levan production by the bacterium. The optimized medium with sugarcane juice at 20 % (v/v) and casein peptone at 2 % (w/v) was found to be optimal at an initial pH of 7.0 and incubation temperature of 35 °C for 48 h. Under these conditions, the maximum levan concentration was 50.25 g/L on wet weight basis and 16.35 g/L on dry weight basis. The produced inulin type FOS (kestose and neokestose) and levan were characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) analysis. The study revealed that the levansucrase could form FOS from sucrose. The locally available low-cost substrate such as sugarcane juice in the form of a renewable substrate is proposed to be suitable even for scale-up production of enzyme and FOS for industrial applications. The levan and FOS synthesized by the bacterium are suitable for food applications and biomedical uses as the bacterium has GRAS status and devoid of endotoxin as compared to other Gram-negative bacteria.

Influence of extracellular pH on growth, viability, cell size, acidification activity, and intracellular pH of Lactococcus lactis in batch fermentations.

PubMed

Hansen, Gunda; Johansen, Claus Lindvald; Marten, Gunvor; Wilmes, Jacqueline; Jespersen, Lene; Arneborg, Nils

2016-07-01

In this study, we investigated the influence of three extracellular pH (pHex) values (i.e., 5.5, 6.5, and 7.5) on the growth, viability, cell size, acidification activity in milk, and intracellular pH (pHi) of Lactococcus lactis subsp. lactis DGCC1212 during pH-controlled batch fermentations. A universal parameter (e.g., linked to pHi) for the description or prediction of viability, specific acidification activity, or growth behavior at a given pHex was not identified. We found viability as determined by flow cytometry to remain high during all growth phases and irrespectively of the pH set point. Furthermore, regardless of the pHex, the acidification activity per cell decreased over time which seemed to be linked to cell shrinkage. Flow cytometric pHi determination demonstrated an increase of the averaged pHi level for higher pH set points, while the pH gradient (pHi-pHex) and the extent of pHi heterogeneity decreased. Cells maintained positive pH gradients at a low pHex of 5.5 and even during substrate limitation at the more widely used pHex 6.5. Moreover, the strain proved able to grow despite small negative or even absent pH gradients at a high pHex of 7.5. The larger pHi heterogeneity at pHex 5.5 and 6.5 was associated with more stressful conditions resulting, e.g., from higher concentrations of non-dissociated lactic acid, while the low pHi heterogeneity at pHex 7.5 most probably corresponded to lower concentrations of non-dissociated lactic acid which facilitated the cells to reach the highest maximum active cell counts of the three pH set points.

Influence of modified carbon substrate on boron doped ultrananocrystalline diamond deposition

NASA Astrophysics Data System (ADS)

Sizuka Oishi, Silvia; Mieko Silva, Lilian; Cocchieri Botelho, Edson; Cerqueira Rezende, Mirabel; Alves Cairo, Carlos Alberto; Gomes Ferreira, Neidenêi

2018-02-01

Boron doped ultrananocrystalline diamond (B-UNCD) growth was studied on modified reticulated vitreous carbon (RVC) produced from poly(furfuryl alcohol) (PFA) resin with sodium hydroxide additions at two different heat treatment temperatures. The different amounts of NaOH in PFA (up to reaching pH values of around 3, 5, 7, and 9) aimed to neutralize the acid catalyst and to increase the PFA storage life. Besides, this procedure was responsible for increasing the oxygen content of RVC samples. Thus, the effect of carbon and oxygen coming from the substrates in addition to their different graphitization indexes on diamond morphology, grain size, preferential growth and boron doping level were investigated by FEG-SEM, x-ray diffraction and Raman spectroscopy. Therefore, B-UNCD films were successfully grown on RVC with pH values of 3, 5, 7, and 9 heat treated at 1000 and 1700 °C. Nonetheless, the higher oxygen amount during B-UNCD growth for samples with pH 7 and 9 heat treated at 1000 °C was responsible for the RVC surface etching and the decrease in the boron concentration of such samples. The cross section images showed that B-UNCD infiltrated at around 0.9 mm in depth of RVC samples while carbon nanowalls were observed mainly on RVC samples heat treated at 1000 °C for all pH range studied.

Human Salivary Aldehyde Dehydrogenase: Purification, Kinetic Characterization and Effect of Ethanol, Hydrogen Peroxide and Sodium Dodecyl Sulfate on the Activity of the Enzyme.

PubMed

Alam, Md Fazle; Laskar, Amaj Ahmed; Choudhary, Hadi Hasan; Younus, Hina

2016-09-01

Human salivary aldehyde dehydrogenase (hsALDH) enzyme appears to be the first line of defense in the body against exogenous toxic aldehydes. However till date much work has not been done on this important member of the ALDH family. In this study, we have purified hsALDH to homogeneity by diethylaminoethyl-cellulose (DEAE-cellulose) ion-exchange chromatography in a single step. The molecular mass of the homodimeric enzyme was determined to be approximately 108 kDa. Four aromatic substrates; benzaldehyde, cinnamaldehyde, 2-naphthaldehyde and 6-methoxy-2-naphthaldehyde were used for determining the activity of pure hsALDH. K m values for these substrates were calculated to be 147.7, 5.31, 0.71 and 3.31 μM, respectively. The best substrates were found to be cinnamaldehyde and 2-naphthaldehyde since they exhibited high V max /K m values. 6-methoxy-2-naphthaldehyde substrate was used for further kinetic characterization of pure hsALDH. The pH and temperature optima of hsALDH were measured to be pH 8 and 45 °C, respectively. The pure enzyme is highly unstable at high temperatures. Ethanol, hydrogen peroxide and SDS activate hsALDH, therefore it is safe and beneficial to include them in mouthwashes and toothpastes in low concentrations.

Purification and properties of rennin-like enzyme from Aspergillus ochraceus.

PubMed

Ismail, A A; Foda, M S; Khorshid, M A

1978-01-01

An active milk-clotting enzyme was purified some 40-fold from culture supernatant of Aspergillus ochraceus. The purification steps included ammonium sulfate precipitation, G-100 Sephadex gel filtration, and ion exchange chromatography, using DEAE Cellulose column. The enzyme exhibited milk-clotting activity and proteolytic behaviour, an optimum at pH 6.0 and in the range of 7--8.5, respectively. The purified enzyme was actively proteolytic against casein, haemoglobin, and bovine serum albumin at pH 8. The milk-clotting activity was greatly enhanced by manganous ions and by increasing concentrations of calcium chloride. Copper, zinc, and ammonium ions were potent inhibitors of the milk-curdling activity of the purified enzyme. Significant inhibition was also noted with sodium chloride at concentrations of 3% or more. Under the specified reaction condition, maximum rate of proteolysis against casein was obtained at 0.4% substrate concentration, whereas the milk-clotting time was linear proportional to dry skim milk concentration in the range of 8 to 24%. The results are discussed in comparison with other microbial milk-clotting enzymes, and limitations of applicability are also presented.

Novel Bacillus subtilis IND19 cell factory for the simultaneous production of carboxy methyl cellulase and protease using cow dung substrate in solid-substrate fermentation.

PubMed

Vijayaraghavan, Ponnuswamy; Arun, Arumugaperumal; Al-Dhabi, Naif Abdullah; Vincent, Samuel Gnana Prakash; Arasu, Mariadhas Valan; Choi, Ki Choon

2016-01-01

Hydrolytic enzymes, such as cellulases and proteases, have various applications, including bioethanol production, extraction of fruit and vegetable juice, detergent formulation, and leather processing. Solid-substrate fermentation has been an emerging method to utilize low-cost agricultural residues for the production of these enzymes. Although the production of carboxy methyl cellulase (CMCase) and protease in solid state fermentation (SSF) have been studied extensively, research investigating multienzyme production in a single fermentation process is limited. The production of multienzymes from a single fermentation system could reduce the overall production cost of enzymes. In order to achieve enhanced production of enzymes, the response surface methodology (RSM) was applied. Bacillus subtilis IND19 utilized cow dung substrates for the production of CMCase and protease. A central composite design and a RSM were used to determine the optimal concentrations of peptone, NaH2PO4, and medium pH. Maximum productions of CMCase and protease were observed at 0.9 % peptone, 0.78 % NaH2PO4, and medium pH of 8.41, and 1 % peptone, 0.72 % NaH2PO4, and medium pH of 8.11, respectively. Under the optimized conditions, the experimental yield of CMCase and protease reached 473.01 and 4643 U/g, which were notably close to the predicted response (485.05 and 4710 U/g). These findings corresponded to an overall increase of 2.1- and 2.5-fold in CMCase and protease productions, respectively. Utilization of cow dung for the production of enzymes is critical to producing multienzymes in a single fermentation step. Cow dung is available in large quantity throughout the year. This report is the first to describe simultaneous production of CMCase and protease using cow dung. This substrate could be directly used as the culture medium without any pretreatment for the production of these enzymes at an industrial scale.

Impact of Lactic Acid and Hydrogen Ion on the Simultaneous Fermentation of Glucose and Xylose by the Carbon Catabolite Derepressed Lactobacillus brevis ATCC 14869.

PubMed

Jeong, Kyung Hun; Israr, Beenish; Shoemaker, Sharon P; Mills, David A; Kim, Jaehan

2016-07-28

Lactobacillus brevis ATCC 14869 exhibited a carbon catabolite de-repressed (CCR) phenotype which has ability to consume fermentable sugar simultaneously with glucose. To evaluate this unusual phenotype under harsh conditions during fermentation, the effect of lactic acid and hydrogen ion concentrations on L. brevis ATCC 14869 were examined. Kinetic equations describing the relationship between specific cell growth rate and lactic acid or hydrogen ion concentration has been reduced. The change of substrate utilization and product formation according to lactic acid and hydrogen ion concentration in the media were quantitatively described. Moreover; utilization of other compounds were also observed along with hydrogen ion and lactic acid concentration simultaneously. It has been found that substrate preference changes significantly regarding to utilization of compounds in media. That could result into formation of two-carbon products. In particular, acetic acid present in the media as sodium acetate were consumed by L. brevis ATCC 14869 under extreme pH of both acid and alkaline conditions.

Determination of Urease Biochemical Properties of Asparagus Bean (Vigna unguiculata ssp sesquipedalis L.)

NASA Astrophysics Data System (ADS)

Zusfahair; Ningsih, D. R.; Fatoni, A.; Pertiwi, D. S.

2018-04-01

Urease is enzyme that plays a role in nitrogen metabolism during plant germination. Plants that produce a lot of urease are grains. This study used asparagus bean as source of urease. The purpose of this research is to learn the effect of germination time on the activity of urease enzyme from asparagus bean and its biochemical properties. The research was started by germination of asparagus bean on day 2, 4, 6, 8, 10 and 12. Asparagus bean sprouts were extracted using acetone and separated by centrifugation to obtain the crude extract of urease. The biochemical properties of the crude extract of urease was further determined including: the effect of temperature, pH, substrate concentration, and metal addition to urease activity. The urease activity is determined by the Nessler method. The germination time of asparagus bean in yielding urease enzyme reached the optimum activity on the 8th day with activity value of 593.7 U/mL. The biochemical properties of urease from asparagus bean have optimum activity at 35 °C, pH 7.0 and substrate concentration 0.125% with activity value of 600 U/mL. Addition of CaCl2, SnCl2 and ZnCl2 metals decrease the activity of urease.

Determination of long-range scalar (1)H-(1)H coupling constants responsible for polarization transfer in SABRE.

PubMed

Eshuis, Nan; Aspers, Ruud L E G; van Weerdenburg, Bram J A; Feiters, Martin C; Rutjes, Floris P J T; Wijmenga, Sybren S; Tessari, Marco

2016-04-01

SABRE (Signal Amplification By Reversible Exchange) nuclear spin hyperpolarization method can provide strongly enhanced NMR signals as a result of the reversible association of small molecules with para-hydrogen (p-H2) at an iridium metal complex. The conversion of p-H2 singlet order to enhanced substrate proton magnetization within such complex is driven by the scalar coupling interactions between the p-H2 derived hydrides and substrate nuclear spins. In the present study these long-range homonuclear couplings are experimentally determined for several SABRE substrates using an NMR pulse sequence for coherent hyperpolarization transfer at high magnetic field. Pyridine and pyrazine derivatives appear to have a similar ∼1.2 Hz (4)J coupling to p-H2 derived hydrides for their ortho protons, and a much lower (5)J coupling for their meta protons. Interestingly, the (4)J hydride-substrate coupling for five-membered N-heterocyclic substrates is well below 1 Hz. Copyright © 2016 Elsevier Inc. All rights reserved.

Determination of long-range scalar 1H-1H coupling constants responsible for polarization transfer in SABRE

NASA Astrophysics Data System (ADS)

Eshuis, Nan; Aspers, Ruud L. E. G.; van Weerdenburg, Bram J. A.; Feiters, Martin C.; Rutjes, Floris P. J. T.; Wijmenga, Sybren S.; Tessari, Marco

2016-04-01

SABRE (Signal Amplification By Reversible Exchange) nuclear spin hyperpolarization method can provide strongly enhanced NMR signals as a result of the reversible association of small molecules with para-hydrogen (p-H2) at an iridium metal complex. The conversion of p-H2 singlet order to enhanced substrate proton magnetization within such complex is driven by the scalar coupling interactions between the p-H2 derived hydrides and substrate nuclear spins. In the present study these long-range homonuclear couplings are experimentally determined for several SABRE substrates using an NMR pulse sequence for coherent hyperpolarization transfer at high magnetic field. Pyridine and pyrazine derivatives appear to have a similar ∼1.2 Hz 4J coupling to p-H2 derived hydrides for their ortho protons, and a much lower 5J coupling for their meta protons. Interestingly, the 4J hydride-substrate coupling for five-membered N-heterocyclic substrates is well below 1 Hz.

Bioprocess design guided by in situ substrate supply and product removal: process intensification for synthesis of (S)-1-(2-chlorophenyl)ethanol.

PubMed

Schmölzer, Katharina; Mädje, Katharina; Nidetzky, Bernd; Kratzer, Regina

2012-03-01

We report herein on bioprocess development guided by the hydrophobicities of substrate and product. Bioreductions of o-chloroacetophenone are severely limited by instability of the catalyst in the presence of aromatic substrate and (S)-1-(2-chlorophenyl)ethanol. In situ substrate supply and product removal was used to protect the utilized Escherichia coli whole cell catalyst based on Candida tenuis xylose reductase during the reaction. Further engineering at the levels of the catalyst and the reaction media was matched to low substrate concentrations in the aqueous phase. Productivities obtained in aqueous batch reductions were 21-fold improved by addition of 20% (v/v) hexane, NAD(+), expression engineering, cell permeabilization and pH optimization. Reduction of 300 mM substrate was accomplished in 97% yield and use of the co-solvent hexane in subsequent extraction steps led to 88% recovery. Product loss due to high catalyst loading was minimized by using the same extractant in bioreduction and product isolation. Copyright © 2012 Elsevier Ltd. All rights reserved.

The effects of liming an Adirondack lake watershed on downstream water chemistry: Effects of liming on stream chemistry

USGS Publications Warehouse

Burns, Douglas A.

1996-01-01

Calcite treatment of chronically acidic lakes has improved fish habitat, but the effects on downstream water quality have not previously been examined. In this study, the spatial and temporal effects of watershed CaCO3 treatment on the chemistry of a lake outlet stream in the Adirondack Mountains of New York were examined. Before CaCO3 treatment, the stream was chronically acidic. During spring snowmelt before treatment, pH and acid-neutralizing capacity (ANC) in the outlet stream declined, and NO3- and inorganic monomeric aluminum (AlIM) concentrations increased sharply. During that summer, SO42- and NO3- concentrations decreased downstream, and dissolved organic carbon (DOC) concentrations and ANC increased, in association with the seasonal increase in decomposition of organic matter and the attendant SO42--reduction process. A charge-balance ANC calculation closely matched measured downstream changes in ANC in the summer and indicated that SO42- reduction was the major process contributing to summer increases in ANC. Increases in Ca2+ concentration and ANC began immediately after CaCO3 application, and within 3 months, exceeded their pretreatment values by more than 130 ??eq/L. Within 2 months after treatment, downstream decreases in Ca2+ concentration, ANC, and pH, were noted. Stream mass balances between the lake and the sampling site 1.5 km downstream revealed that the transport of all chemical constituents was dominated by conservative mixing with tributaries and ground water; however, non-conservative processes resulted in significant Ca2+ losses during the 13-month period after CaCO3 treatment. Comparison of substrate samples from the buffered outlet stream with those from its untreated tributaries showed that the percentage of cation-exchange sites occupied by Ca2+, as well as non-exchangeable Ca, were higher in the outlet-stream substrate than in tributary-stream substrate. Mass-balance data for Ca2+, H+, AlIM, and DOC revealed net downstream losses of these constituents and indicated that a reasonable set of hypothesized reactions involving AlIM, HCO3-, Ca2+, SO42-, NO3-7, and DOC could have caused the measured changes in stream acid/base chemistry. In the summer, the sharp decrease in ANC continued despite significant downstream decreases in SO42- concentrations. After CaCO3 treatment, reduction of SO42- was only a minor contributor to ANC changes relative to those caused by Ca2+ dilution from acidic tributaries and acidic ground water, and Ca2+ interactions with stream substrate. ?? 1996 Kluwer Academic Publishers.

Does elevated pCO2 affect reef octocorals?

PubMed

Gabay, Yasmin; Benayahu, Yehuda; Fine, Maoz

2013-03-01

Increasing anthropogenic pCO2 alters seawater chemistry, with potentially severe consequences for coral reef growth and health. Octocorals are the second most important faunistic component in many reefs, often occupying 50% or more of the available substrate. Three species of octocorals from two families were studied in Eilat (Gulf of Aqaba), comprising the zooxanthellate Ovabunda macrospiculata and Heteroxenia fuscescens (family Xeniidae), and Sarcophyton sp. (family Alcyoniidae). They were maintained under normal (8.2) and reduced (7.6 and 7.3) pH conditions for up to 5 months. Their biolological features, including protein concentration, polyp weight, density of zooxanthellae, and their chlorophyll concentration per cell, as well as polyp pulsation rate, were examined under conditions more acidic than normal, in order to test the hypothesis that rising pCO2 would affect octocorals. The results indicate no statistically significant difference between the octocorals exposed to reduced pH values compared to the control. It is therefore suggested that the octocorals' tissue may act as a protective barrier against adverse pH conditions, thus maintaining them unharmed at high levels of pCO2.

Characterization of an Alkali- and Halide-Resistant Laccase Expressed in E. coli: CotA from Bacillus clausii

PubMed Central

Brander, Søren; Mikkelsen, Jørn D.; Kepp, Kasper P.

2014-01-01

The limitations of fungal laccases at higher pH and salt concentrations have intensified the search for new extremophilic bacterial laccases. We report the cloning, expression, and characterization of the bacterial cotA from Bacillus clausii, a supposed alkalophilic ortholog of cotA from B. subtilis. Both laccases were expressed in E. coli strain BL21(DE3) and characterized fully in parallel for strict benchmarking. We report activity on ABTS, SGZ, DMP, caffeic acid, promazine, phenyl hydrazine, tannic acid, and bilirubin at variable pH. Whereas ABTS, promazine, and phenyl hydrazine activities vs. pH were similar, the activity of B. clausii cotA was shifted upwards by ∼0.5–2 pH units for the simple phenolic substrates DMP, SGZ, and caffeic acid. This shift is not due to substrate affinity (KM) but to pH dependence of catalytic turnover: The kcat of B. clausii cotA was 1 s−1 at pH 6 and 5 s−1 at pH 8 in contrast to 6 s−1 at pH 6 and 2 s−1 at pH 8 for of B. subtilis cotA. Overall, kcat/KM was 10-fold higher for B. subtilis cotA at pHopt. While both proteins were heat activated, activation increased with pH and was larger in cotA from B. clausii. NaCl inhibited activity at acidic pH, but not up to 500–700 mM NaCl in alkaline pH, a further advantage of the alkali regime in laccase applications. The B. clausii cotA had ∼20 minutes half-life at 80°C, less than the ∼50 minutes at 80°C for cotA from B. subtilis. While cotA from B. subtilis had optimal stability at pH∼8, the cotA from B. clausii displayed higher combined salt- and alkali-resistance. This resistance is possibly caused by two substitutions (S427Q and V110E) that could repel anions to reduce anion-copper interactions at the expense of catalytic proficiency, a trade-off of potential relevance to laccase optimization. PMID:24915287

Enhancing polyphenol extraction from unripe apples by carbohydrate-hydrolyzing enzymes.

PubMed

Zheng, Hu-zhe; Hwang, In-Wook; Chung, Shin-Kyo

2009-12-01

The effects of process variables such as enzyme types, enzyme ratio, reaction temperature, pH, time, and ethanol concentration on the extraction of unripe apple polyphenol were investigated. The results indicated that Viscozyme L had the strongest effect on polyphenols extraction and was selected to study the polyphenol composition. The ratio of enzyme (Viscozyme L) to substrate (2 fungal beta-glucanase units (FBG)) at 0.02, reaction at pH 3.7, 50 degrees C for 12 h, and ethanol concentration of 70% were chosen as the most favorable extraction condition. Total phenolic content (TPC), reducing sugar content (RSC), and extraction yield increased by about 3, 1.5, and 2 times, respectively, compared with control. The contents of p-coumaric acid, ferulic acid, and caffeic acid increased to 8, 4, and 32 times, respectively. The enzyme-aided polyphenol extraction process from unripe apples might be applied to food industry for enhancing bioactive compound production.

Enhancing polyphenol extraction from unripe apples by carbohydrate-hydrolyzing enzymes*

PubMed Central

Zheng, Hu-zhe; Hwang, In-Wook; Chung, Shin-Kyo

2009-01-01

The effects of process variables such as enzyme types, enzyme ratio, reaction temperature, pH, time, and ethanol concentration on the extraction of unripe apple polyphenol were investigated. The results indicated that Viscozyme L had the strongest effect on polyphenols extraction and was selected to study the polyphenol composition. The ratio of enzyme (Viscozyme L) to substrate (2 fungal beta-glucanase units (FBG)) at 0.02, reaction at pH 3.7, 50 °C for 12 h, and ethanol concentration of 70% were chosen as the most favorable extraction condition. Total phenolic content (TPC), reducing sugar content (RSC), and extraction yield increased by about 3, 1.5, and 2 times, respectively, compared with control. The contents of p-coumaric acid, ferulic acid, and caffeic acid increased to 8, 4, and 32 times, respectively. The enzyme-aided polyphenol extraction process from unripe apples might be applied to food industry for enhancing bioactive compound production. PMID:19946955

Solution NMR study of environmental effects on substrate seating in human heme oxygenase: influence of polypeptide truncation, substrate modification and axial ligand.

PubMed

Zhu, Wenfeng; Li, Yiming; Wang, Jinling; Ortiz de Montellano, Paul R; La Mar, Gerd N

2006-01-01

Solution proton NMR has been used here to show that, as either the high-spin ferric, protohemin (PH) substrate complex at neutral pH, or the low-spin ferric, cyanide-inhibited PH substrate complex, the active site electronic and molecular structure of the 233- and 265-residue recombinant constructs of human heme oxygenase-1, hHO, are essentially indistinguishable. It is shown, moreover, that the equilibrium PH orientational isomerism about the alpha,gamma-meso axis is 1:1 in the water-ligated, resting-state complex, but changes to a 4:1 equilibrium ratio as the cyanide-inhibited complex, with the minor species in solution corresponding to the only one found in crystals. The introduction of significant PH orientational preference in the cyanide over the aquo complex is rationalized by the crystallographic observation for the same H2O and CN ligated complexes of rat heme oxygenase (rHO), where the steric tilt of the Fe-CN unit resulted in a approximately 1 A transition of PH into the hydrophobic interior, and stronger interaction of the vinyls with the HO matrix [M. Sugishima, H. Sakamoto, M. Noguchi, K. Fukugama, Biochemistry 42 (2003) 9898-9905]. 1H NMR spectra of the cyanide-inhibited PH complex are the most used, and most useful, for determining the distribution of orientational isomerism for PH in complexes of HO. Hence, it is imperative that the time-course of the spectra after sample preparation be considered in order to reach conclusions that relate isomeric seating of the heme with variable isomeric biliverdin products. The natural orientational isomerism of PH leads to spectral congestion that has prompted the use of a synthetic, twofold symmetric substrate, 2,4-dimethyldeuterohemin, DMDH. While the hyperfine shift pattern for non-ligated residues are very similar and are consistent with largely conserved molecular structure with the alternate substrates, the steric tilt of the Fe-CN vector towards the protein interior, as determined by the orientation of the major magnetic axes, is 2 degrees smaller for DMDH than PH, and is rationalized by the substrate translating even further into the hydrophobic interior in the cyanide complex when the bulky vinyl groups are replaced by methyl groups.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qasim, Mohammad A., E-mail: qasimm@ipfw.edu; Song, Jikui; Markley, John L.

Research highlights: {yields} Large pK shifts in ionizable groups when buried in the protein interior. {yields} Substrate dependent shifts in pH optimum for serine proteases. {yields} Lys side chain is a stronger acid in serine protease S{sub 1} pocket than Asp side chain. -- Abstract: Enzymatic hydrolysis of the synthetic substrate succinyl-Ala-Ala-Pro-Xxx-pNA (where Xxx = Leu, Asp or Lys) catalyzed by bovine chymotrypsin (CHYM) or Streptomyces griseus protease B (SGPB) has been studied at different pH values in the pH range 3-11. The pH optima for substrates having Leu, Asp, and Lys have been found to be 7.5-8.0, 5.5-6.0, andmore » {approx}10, respectively. At the normally reported pH optimum (pH 7-8) of CHYM and SGPB, the substrate with Leu at the reactive site is more than 25,000-fold more reactive than that with Asp. However, when fully protonated, Asp is nearly as good a substrate as Leu. The pK values of the side chains of Asp and Lys in the hydrophobic S{sub 1} pocket of CHYM and SGPB have been calculated from pH-dependent hydrolysis data and have been found to be about 9 for Asp and 7.4 and 9.7 for Lys for CHYM and SGPB, respectively. The results presented in this communication suggest a possible application of CHYM like enzymes in cleaving peptide bonds contributed by acidic amino acids between pH 5 and 6.« less

Efficient butanol-ethanol (B-E) production from carbon monoxide fermentation by Clostridium carboxidivorans.

PubMed

Fernández-Naveira, Ánxela; Abubackar, Haris Nalakath; Veiga, María C; Kennes, Christian

2016-04-01

The fermentation of waste gases rich in carbon monoxide using acetogens is an efficient way to obtain valuable biofuels like ethanol and butanol. Different experiments were carried out with the bacterial species Clostridium carboxidivorans as biocatalyst. In batch assays with no pH regulation, after complete substrate exhaustion, acetic acid, butyric acid, and ethanol were detected while only negligible butanol production was observed. On the other side, in bioreactors, with continuous carbon monoxide supply and pH regulation, both C2 and C4 fatty acids were initially formed as well as ethanol and butanol at concentrations never reported before for this type of anaerobic bioconversion of gaseous C1 compounds, showing that the operating conditions significantly affect the metabolic fermentation profile and butanol accumulation. Maximum ethanol and butanol concentrations in the bioreactors were obtained at pH 5.75, reaching values of 5.55 and 2.66 g/L, respectively. The alcohols were produced both from CO fermentation as well as from the bioconversion of previously accumulated acetic and butyric acids, resulting in low residual concentrations of such acids at the end of the bioreactor experiments. CO consumption was often around 50% and reached up to more than 80%. Maximum specific rates of ethanol and butanol production were reached at pH 4.75, with values of 0.16 g/h*g of biomass and 0.07 g/h*g of biomass, respectively, demonstrating that a low pH was more favorable to solventogenesis in this process, although it negatively affects biomass growth which does also play a role in the final alcohol titer.

Selecting the best AOP for isoxazolyl penicillins degradation as a function of water characteristics: Effects of pH, chemical nature of additives and pollutant concentration.

PubMed

Villegas-Guzman, Paola; Silva-Agredo, Javier; Florez, Oscar; Giraldo-Aguirre, Ana L; Pulgarin, Cesar; Torres-Palma, Ricardo A

2017-04-01

To provide new insights toward the selection of the most suitable AOP for isoxazolyl penicillins elimination, the degradation of dicloxacillin, a isoxazolyl penicillin model, was studied using different advanced oxidation processes (AOPs): ultrasound (US), photo-Fenton (UV/H 2 O 2 /Fe 2+ ) and TiO 2 photocatalysis (UV/TiO 2 ). Although all processes achieved total removal of the antibiotic and antimicrobial activity, and increased the biodegradability level of the solutions, significant differences concerning the mineralization extend, the pH of the solution, the pollutant concentration and the chemical nature of additives were found. UV/TiO 2 reached almost complete mineralization; while ∼10% mineralization was obtained for UV/H 2 O 2 /Fe 2+ and practically zero for US. Effect of initial pH, mineral natural water and the presence of organic (glucose, 2-propanol and oxalic acid) were then investigated. UV/H 2 O 2 /Fe 2+ and US processes were improved in acidic media, while natural pH favored UV/TiO 2 system. According to both the nature of the added organic compound and the process, inhibition, no effect or enhancement of the degradation rate was observed. The degradation in natural mineral water showed contrasting results according to the antibiotic concentration: US process was enhanced at low concentration of dicloxacillin followed by detrimental effects at high substrate concentrations. A contrary effect was observed during photo-Fenton, while UV/TiO 2 was inhibited in all of cases. Finally, a schema illustrating the enhancement or inhibiting effects of water matrix is proposed as a tool for selecting the best process for isoxazolyl penicillins degradation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Associations between iron concentration and productivity in montane streams of the Black Hills, South Dakota

USGS Publications Warehouse

Hayer, Cari Ann; Holcomb, Benjamin M.; Chipps, Steven R.

2013-01-01

Iron is an important micronutrient found in aquatic systems that can influence nutrient availability (e.g., phosphorus) and primary productivity. In streams, high iron concentrations often are associated with low pH as a result of acid mine drainage, which is known to affect fish and invertebrate communities. Streams in the Black Hills of South Dakota are generally circumneutral in pH, yet select streams exhibit high iron concentrations associated with natural iron deposits. In this study, we examined relationships among iron concentration, priphyton biomass, macroinvertebrate abundance, and fish assemblages in four Black Hills streams. The stream with the highest iron concentration (~5 mg Fe/L) had reduced periphyton biomass, invertebrate abundance, and fish biomass compared to the three streams with lower iron levels (0.1 to 0.6 mg Fe/L). Reduced stream productivity was attributed to indirect effects of ferric iron Fe+++), owing to iron-hydroxide precipitation that influenced habitat quality (i.e., substrate and turbidity) and food availability (periphyton and invertebrates) for higher trophic levels (e.g., fish). Additionally, reduced primary and secondary production was associated with reduced standing stocks of salmonid fishes. Our findings suggested that naturally occurring iron deposits may constrain macroinvertebrate and fish production.

Suspension chemistry and electrophoretic deposition of zirconia electrolyte on conducting and non-conducting substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, Debasish; Basu, Rajendra N., E-mail: rnbasu@cgcri.res.in

2013-09-01

Graphical abstract: - Highlights: • Stable suspension of yttria stabilized zirconia (YSZ) obtained in isopropanol medium. • Suspension chemistry and process parameters for electrophoretic deposition optimized. • Deposited film quality changed with iodine and water (dispersants) concentration. • Dense YSZ film (∼5 μm) fabricated onto non-conducting porous NiO-YSZ anode substrate. - Abstract: Suspensions of 8 mol% yttria stabilized zirconia (YSZ) particulates in isopropanol medium are prepared using acetylacetone, iodine and water as dispersants. The effect of dispersants concentration on suspension stability, particle size distribution, electrical conductivity and pH of the suspensions are studied in detail to optimize the suspension chemistry.more » Electrophoretic deposition (EPD) has been conducted to produce thin and dense YSZ electrolyte films. Deposition kinetics have been studied in depth and good quality films on conducting substrate are obtained at an applied voltage of 15 V for 3 min. YSZ films are also fabricated on non-conducting NiO-YSZ anode substrate using a steel plate on the reverse side of the substrate. Upon co-firing at 1400 °C for 6 h a dense YSZ film of thickness ∼5 μm is obtained. Such a half cell (anode + electrolyte) can be used to fabricate a solid oxide fuel cell on applying a suitable cathode layer.« less

Purification and characterization of a novel cytosolic NADP(H)-dependent retinol oxidoreductase from rabbit liver.

PubMed

Huang, D Y; Ichikawa, Y

1997-03-07

Rabbit liver cytosol exhibits very high retinol dehydrogenase activity. At least two retinol dehydrogenases were demonstrated to exist in rabbit liver cytosol, and the major one, a cytosolic NADP(H)-dependent retinol dehydrogenase (systematic name: retinol oxidoreductase) was purified about 1795-fold to electrophoretic and column chromatographic homogeneity by a procedure involving column chromatography on AF-Red Toyopearl twice and then hydroxyapatite. Its molecular mass was estimated to be 34 kDa by SDS-PAGE, and 144 kDa by HPLC gel filtration, suggesting that it is a homo-tetramer. The enzyme uses free retinol and retinal, and their complexes with CRBP as substrates in vitro. The optimum pH values for retinol oxidation of free retinol and CRBP-retinol were 8.8-9.2 and 8.0-9.0, respectively, and those for retinal reduction of free retinal and retinal-CRBP were the same, 7.0-7.6. Km for free retinol and Vmax for retinal formation were 2.8 microM and 2893 nmol/min per mg protein at 37 degrees C (pH 9.0) and the corresponding values with retinol-CRBP as a substrate were 2.5 microM and 2428 nmol/min per mg protein at 37 degrees C (pH 8.6); Km for free retinal and Vmax for retinol formation were 6.5 microM and 4108 nmol/min per mg protein, and the corresponding values with retinal-CRBP as a substrate were 5.1 microM and 3067 nmol/min per mg protein at 37 degrees C, pH 7.4. NAD(H) was not effective as a cofactor. 4-Methylpyrazole was a weak inhibitor (IC50 = 28 mM) of the enzyme, and ethanol was neither a substrate nor an inhibitor of the enzyme. This enzyme exhibits relatively broad aldehyde reductase activity and some ketone reductase activity, the activity for aromatic substitutive aldehydes being especially high and effective. Whereas, except in the case of retinol, oxidative activity toward the corresponding alcohols was not detected. This novel cytosolic enzyme may play an important role in vivo in maintaining the homeostasis of retinal, the substrate of retinoic acid synthesis, at least in rabbit liver, since a high concentration of retinol in liver and the lower Km of the enzyme for retinol force the oxidative reaction, while higher activity of retinal reductase at physiological pH forces the reductive reaction.

Polycrystalline silicon ion sensitive field effect transistors

NASA Astrophysics Data System (ADS)

Yan, F.; Estrela, P.; Mo, Y.; Migliorato, P.; Maeda, H.; Inoue, S.; Shimoda, T.

2005-01-01

We report the operation of polycrystalline silicon ion sensitive field effect transistors. These devices can be fabricated on inexpensive disposable substrates such as glass or plastics and are, therefore, promising candidates for low cost single-use intelligent multisensors. In this work we have developed an extended gate structure with a Si3N4 sensing layer. Nearly ideal pH sensitivity (54mV /pH) and stable operation have been achieved. Temperature effects have been characterized. A penicillin sensor has been fabricated by functionalizing the sensing area with penicillinase. The sensitivity to penicillin G is about 10mV/mM, in solutions with concentration lower than the saturation value, which is about 7 mM.

Biohydrogen Production from Pineapple Waste: Effect of Substrate Concentration and Acid Pretreatment

NASA Astrophysics Data System (ADS)

Cahyari, K.; Putri, A. M.; Oktaviani, E. D.; Hidayat, M. A.; Norajsha, J. D.

2018-05-01

Biohydrogen is the ultimate choice of energy carrier in future due to its superior qualities such as fewer greenhouse gases emission, high energy density (142 kJ/gram), and high energy conversion using a fuel cell. Production of biohydrogen from organic waste e.g. pineapple waste offers a simultaneous solution for renewable energy production and waste management. It is estimated that pineapple cultivation in Indonesia generated more than 1 million ton/year comprising of rotten pineapple fruit, leaves, and stems. Majority of this waste is dumped into landfill area without any treatments which lead to many environmental problems. This research was meant to investigate the utilization of pineapple waste i.e. peel and the core of pineapple fruit and leaves to produce biohydrogen through mesophilic dark fermentation (30°C, 1 atm, pH 5.0). Effect of dilute acid treatment and substrate concentration was particularly investigated in these experiments. Peel and core of pineapple waste were subjected to fermentation at 3 various substrate concentration i.e. 8.8, 17.6 and 26.4-gram VS/liter. Meanwhile, pineapple leaves were pretreated using dilute acid (H2SO4) at 0.2, 0.3 and 0.4 N and followed by dark fermentation. Results show that the highest yield of biohydrogen was obtained at a substrate concentration of 26.4-gram VS/liter both for peel and core of the waste. Pretreatment using dilute acid (H2SO4) 0.3 N might improve fermentation process with a higher yield at 0.8 ml/gram VS. Hydrogen percentage in biogas produced during fermentation process was in the range between 5 – 32% of volume ratio. In summary, it is possible to utilize pineapple waste for production of biohydrogen at an optimum substrate concentration of 26.4-gram VS/liter and acid pretreatment (H2SO4) of 0.3 N.

Integrating pH, substrate, and plant regrowth effects on soil nitrogen cycling after fire

NASA Astrophysics Data System (ADS)

Hanan, E. J.; Schimel, J.; Tague, C.; D'Antonio, C. M.

2014-12-01

Mediterranean-type ecosystems are structured by fire. In California chaparral, fires uncouple N production and consumption by enhancing nitrification and reducing plant uptake. NO3- that accumulates after fire is vulnerable to leaching. However, the extent to which fires decouple N fluxes can vary spatially and with timing of fire, and the specific mechanisms controlling N metabolism in recovering chaparral are not well understood. We combined empirical analysis and modeling in two chaparral watersheds to better understand how these systems recover from fire, and to explore their sensitivity to changing climate and fire regimes. To evaluate how pH, charcoal, and NH4+ supply influence N cycling, we measured mineralization and nitrification rates in chaparral soils that burned 1, 4, 20 and 40 years prior to sampling. We then experimentally adjusted pH, charcoal, and NH4+ concentrations for all soils in a factorial design, and incubated them for 8 weeks. Each week, we measured respiration, exchangeable NH4+ and NO3- content, nitrification potential, microbial biomass, and pH. Then to project the effects of altered precipitation patterns and fire timing on nitrogen dynamics and recovery, we used the hydro-biogeochemical model RHESSys. Fires were imposed at the beginning and end of the growing season under various climates. NO3- production was highest in soils collected from the most recently burned sites. Also, NO3- concentrations increased over the course of incubation in soils from all sites, especially at high pH, and with NH4+ addition. Charcoal slightly augmented the effects of elevated pH and NH4+ on NO3- production iduring the early stages of incubation in 1 and 4-year old sites, while it slightly dampened their effects by week 8. However, in 20 and 40-year old sites, charcoal had no effect. Overall, nitrification was most powerfully constrained by NH4+ supply. However, increases in pH that occur after fire may enhance nitrification rates when substrate is available. Also, charcoal might enhance N cycling immediately after fire, perhaps by supplying C to microbes, but impacts are short-lived. Modeling results suggest that soil acidity and rapid plant recovery reduce leaching. However, during drought and temperature extremes nutrients pools recover more slowly when fires occur prior to the hot, dry summer.

Effect of fermentation parameters on bio-alcohols production from glycerol using immobilized Clostridium pasteurianum: an optimization study.

PubMed

Khanna, Swati; Goyal, Arun; Moholkar, Vijayanand S

2013-01-01

This article addresses the issue of effect of fermentation parameters for conversion of glycerol (in both pure and crude form) into three value-added products, namely, ethanol, butanol, and 1,3-propanediol (1,3-PDO), by immobilized Clostridium pasteurianum and thereby addresses the statistical optimization of this process. The analysis of effect of different process parameters such as agitation rate, fermentation temperature, medium pH, and initial glycerol concentration indicated that medium pH was the most critical factor for total alcohols production in case of pure glycerol as fermentation substrate. On the other hand, initial glycerol concentration was the most significant factor for fermentation with crude glycerol. An interesting observation was that the optimized set of fermentation parameters was found to be independent of the type of glycerol (either pure or crude) used. At optimum conditions of agitation rate (200 rpm), initial glycerol concentration (25 g/L), fermentation temperature (30°C), and medium pH (7.0), the total alcohols production was almost equal in anaerobic shake flasks and 2-L bioreactor. This essentially means that at optimum process parameters, the scale of operation does not affect the output of the process. The immobilized cells could be reused for multiple cycles for both pure and crude glycerol fermentation.

Temperature sensitivity of organic substrate decay varies with pH

NASA Astrophysics Data System (ADS)

Min, K.; Lehmeier, C.; Ballantyne, F.; Billings, S. A.

2012-12-01

Cellulose is the most abundant biopolymer in soils and globally ubiquitous. It serves as a primary carbon source for myriad microbes able to release cellulases which cleave the cellulose into smaller molecules. For example, β-glucosidase, one type of cellulase, breaks down a terminal β-glycosidic bond of cellulose. The carbon of the liberated glucose becomes available for microbial uptake, after which it can then be mineralized and returned to the atmosphere via heterotrophic respiration. Thus, exoenzymes play an important role in the global cycling of carbon. Numerous studies suggest that global warming potentially increases the rate at which β-glucosidase breaks down cellulose, but it is not known how pH of the soil solution influences the effect of temperature on cellulose decomposition rates; this is important given the globally wide range of soil pH. Using fluorescence enzyme assay techniques, we studied the effect of temperature and pH on the reaction rate at which purified β-Glucosidase decays β-D-cellobioside (a compound often employed to simulate cellulose). We evaluated the temperature sensitivity of this reaction at five temperatures (5, 10, 15, 20, and 25°C) and six pH values (3.5, 4.5, 5.5, 6.5, 7.5, and 8.5)encompassing the naturally occurring range in soils, in a full-factorial design. First, we determined Vmax at 25°C and pH 6.5, standard conditions for measuring enzyme activities in many studies. The Vmax was 858.65 μmol h-1mg-1and was achieved at substrate concentration of 270 μM. At all pH values, the reaction rate slowed down at lower temperatures; at a pH of 3.5, no enzymatic activity was detected. The enzyme activity was significantly different between pH 4.5 and higher pHs. For example, enzyme reactivity at pH 4.5 was significantly lower than that at 7.5 at 20 and 25°C (Bonferroni-corrected P =0.0006, 0.0004, respectively), but not at lower temperatures. Similarly, enzyme reactivity at pH 4.5 was lower than that at pH 8.5 at 10, 15, and 25°C (P=0.0009, 0.0007, 0.0005, respectively), with a near-significant trend at 20°C (P=0.0023), and exhibited a nearly significant depression in response to temperature at 25°C compared to that at pH 6.5 (P=0.0015). Our results suggest that exoenzymatic cellulose decomposition with warming may be more enhanced in soil systems exhibiting higher pH. This work highlights the importance of soil solution pH as a driver of temperature sensitivity of substrate decay, and adds a level of complexity for developing accurate predictions of soil carbon cycling with climate change.

Reversible covalent binding of neratinib to human serum albumin in vitro.

PubMed

Chandrasekaran, Appavu; Shen, Li; Lockhead, Susan; Oganesian, Aram; Wang, Jianyao; Scatina, JoAnn

2010-12-01

Neratinib (HKI-272), an irreversible inhibitor of Her 2 tyrosine kinase, is currently in development as an alternative for first and second line therapy in metastatic breast cancer patients who overexpress Her 2. Following incubation of [(14)C]neratinib in control human plasma at 37°C for 6 hours, about 60% to 70% of the radioactivity was not extractable, due to covalent binding to albumin. In this study, factors that could potentially affect the covalent binding of neratinib to plasma proteins, specifically to albumin were investigated. When [(14)C]neratinib was incubated at 10 μg/mL in human serum albumin (HSA) or control human plasma, the percent binding increased with time; the highest percentages of binding (46 and 67%, respectively) were observed at 6 hours, the longest duration of incubation examined. Binding increased with increasing temperature; the highest percentages of binding to HSA or human plasma (59 and 78%) were observed at 45°C, the highest temperature tested. The binding also increased with increasing pH of incubation; the highest percentages of binding (56 and 65%) were observed at pH 8.5, the highest pH value tested. The percentages of binding were similar (53% to 57%) when a wide range of concentrations of [(14)C]neratinib (50 ng/mL to 10 μg/mL) were incubated with human plasma at 37°C for 6 hours, indicating that the binding was independent of the substrate concentration, especially in the therapeutic range (50 to 200 ng/mL). When human plasma proteins containing covalently bound [(14)C]neratinb were suspended in a 10 fold volume of phosphate buffer at pH 4.0, 6.0, 7.4, and 8.5, and further incubated at 37°C for ~ 16 hours, about 45%, 44%, 32%, and 12% of the total radioactivity, respectively, was released as unchanged [(14)C]neratinib, indicating that the binding is reversible in nature, with more released at pH 7.4 and below. In conclusion, the covalent binding of neratinib to serum albumin is pH, time and temperature dependent, but not substrate concentration dependent, especially in the therapeutic range. Acidification and incubation of human plasma proteins that contained covalently bound [(14)C]neratinib leads to the release of the drug, indicating that the binding is reversible in nature. It is reasonable to speculate that the release of neratinib from human serum albumin provides a transport system leading to release of neratinib in the more acidic environment of the tumor.

Micro-patterning and characterization of PHEMA-co-PAM-based optical chemical sensors for lab-on-a-chip applications.

PubMed

Zhu, Haixin; Zhou, Xianfeng; Su, Fengyu; Tian, Yanqing; Ashili, Shashanka; Holl, Mark R; Meldrum, Deirdre R

2012-10-01

We report a novel method for wafer level, high throughput optical chemical sensor patterning, with precise control of the sensor volume and capability of producing arbitrary microscale patterns. Monomeric oxygen (O(2)) and pH optical probes were polymerized with 2-hydroxyethyl methacrylate (HEMA) and acrylamide (AM) to form spin-coatable and further crosslinkable polymers. A micro-patterning method based on micro-fabrication techniques (photolithography, wet chemical process and reactive ion etch) was developed to miniaturize the sensor film onto glass substrates in arbitrary sizes and shapes. The sensitivity of fabricated micro-patterns was characterized under various oxygen concentrations and pH values. The process for spatially integration of two sensors (Oxygen and pH) on the same substrate surface was also developed, and preliminary fabrication and characterization results were presented. To the best of our knowledge, it is the first time that poly (2-hydroxylethyl methacrylate)-co-poly (acrylamide) (PHEMA-co-PAM)-based sensors had been patterned and integrated at the wafer level with micron scale precision control using microfabrication techniques. The developed methods can provide a feasible way to miniaturize and integrate the optical chemical sensor system and can be applied to any lab-on-a-chip system, especially the biological micro-systems requiring optical sensing of single or multiple analytes.

Improving the performance of immobilized β-glucosidase using a microreactor.

PubMed

Wei, Ce; Zhou, Yan; Zhuang, Wei; Li, Ganlu; Jiang, Min; Zhang, Hongman

2018-04-01

Here, we have presented a technically simple and efficient method for preparing a continuous flow microreactor by employing immobilized β-glucosidase in a silica quartz capillary tube. Developing an immobilized enzyme layer on the inner wall of the capillary tube involved the modification of the inner wall using bifunctional crosslinking agents 3-aminopropyltriethoxysilane and glutaraldehyde before attaching β-glucosidase. The microreactor afforded unique reaction capacities compared with conventional batch operational configurations. These included enhanced pH and thermal stability during storage tests, increased conversion rates of cellobiose, and reduced product inhibition. The maximum conversion rate of soluble substrate cellobiose digestion in the microreactor was 76% at 50°C and pH 4.8 when the microreactor was operated continually over 10 h at a flow rate of 7 μL/min. This was markedly contrasting to the observed conversion rate of 56% when cellobiose was digested in a conventional batch mode under the same pH and temperature conditions. Reaction inhibition by glucose was significantly reduced in the microreactor. We postulate that the increased capacity of glucose to diffuse into the continual flowing media above the immobilized enzyme layer prevents glucose from reaching inhibitory concentrations at the substrate-enzyme interface. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Optimization of pretreatment and fermentation conditions for production of extracellular cellulase complex using sugarcane bagasse.

PubMed

Ashfaque, Mohammad; Solomon, Sushil; Pathak, Neelam

2014-01-01

Sugarcane bagasse (SCB), a lignocellulosic byproduct of juice extraction from sugarcane, is rich in cellulose (40-42%). This could be used as a substrate for the production of cellulase complex. Fermentation conditions were optimized for production of cellulase complex (CMCase, Cellulobiase and FPase) by wild type Trichoderma sp. using sugarcane bagasse as sole carbon source. Alkaline treatment (2% NaOH) of bagasse (AlSCB) was found suitable for the production of reducing sugar over the acidic pretreatment method. After 5 days of incubation period, 5% substrate concentration at pH 5.0 and 400C resulted in maximum production of CMCase (0.622 U), while maximum (3.388 U) production of cellulobiase was obtained at 300C. The CMCase was precipitated and purified to the extent of 59.06 fold by affinity chromatography with 49.09% recovery. On 12% SDS-PAGE, a single band corresponding to 33 kDa was observed. The Km and Vmax for CMCase from Trichoderma was found 507.04 mg/ml and 65.32 mM/min, respectively. The enzyme exhibited maximum activity at 300C at pH-5.0 (0.363 U) and was stable over range of 20-60°C and pH 5.0-7.5.

Electrodeposition of Zn-Co-Mo Alloy on the Steel Substrate from Citrate Bath and Its Corrosion Behavior in the Chloride Media

NASA Astrophysics Data System (ADS)

Keyvani, A.; Yeganeh, M.; Rezaeyan, H.

2017-04-01

In this study, Zn-Co-Mo coatings were deposited on the steel substrate from a citrate bath after adjusting pH, concentration, and current density. The morphology, the content of alloying elements, and the thickness of deposits were studied. Deposition behavior of these ternary coatings was examined by cathodic polarization and cyclic voltammetry (CV) techniques. The synthesized deposits were investigated by scanning electron microscopy (SEM), energy-dispersive x-ray (EDX) analysis, x-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization methods. The results showed that the deposition potential of Zn-Co-Mo alloy was feasible in negative potentials higher than about -1.25 V versus Ag/AgCl. Moreover, the corrosion behavior of these coatings was found to be related to the extent of Mo as well as the local anodes and cathodes. The amount of molybdenum in the Zn-Co-Mo coating varied from 2.6 to 14 wt.% as a result of changing the pH. Based on the experimental findings, a narrow range of pH values between 5 and 5.5 could contribute to the high quality of coating in conjunction with the corrosion resistant alloy. Besides, the coatings with Mo element could show a passive-like behavior in the anodic region.

Electrochemically deposited gallium oxide nanostructures on silicon substrates

PubMed Central

2014-01-01

We report a synthesis of β-Ga2O3 nanostructures on Si substrate by electrochemical deposition using a mixture of Ga2O3, HCl, NH4OH, and H2O. The presence of Ga3+ ions contributed to the deposition of Ga2O3 nanostructures on the Si surface with the assistance of applied potentials. The morphologies of the grown structures strongly depended on the molarity of Ga2O3 and pH level of electrolyte. β-Ga2O3 nanodot-like structures were grown on Si substrate at a condition with low molarity of Ga2O3. However, Ga2O3 nanodot structures covered with nanorods on top of their surfaces were obtained at higher molarity, and the densities of nanorods seem to increase with the decrease of pH level. High concentration of Ga3+ and OH- ions may promote the reaction of each other to produce Ga2O3 nanorods in the electrolyte. Such similar nature of Ga2O3 nanorods was also obtained by using hydrothermal process. The grown structures seem to be interesting for application in electronic and optoelectronic devices as well as to be used as a seed structure for subsequent chemical synthesis of GaN by thermal transformation method. PMID:24629107

Hydroxyapatite and Other Calcium Phosphates for the Conservation of Cultural Heritage: A Review

PubMed Central

2018-01-01

The present paper reviews the methods and the performance of in situ formation of calcium phosphates (CaP) for the conservation of materials belonging to cultural heritage. The core idea is to form CaP (ideally hydroxyapatite, HAP, the most stable CaP at pH > 4) by reaction between the substrate and an aqueous solution of a phosphate salt. Initially proposed for the conservation of marble and limestone, the treatment has been explored for a variety of different substrates, including sandstones, sulphated stones, gypsum stuccoes, concrete, wall paintings, archaeological bones and paper. First, the studies aimed at identifying the best treatment conditions (e.g., nature and concentration of the phosphate precursor, solution pH, treatment duration, ionic and organic additions to the phosphate solution, mineralogical composition of the new CaP phases) are summarized. Then, the treatment performance on marble and limestone is reviewed, in terms of protective and consolidating effectiveness, compatibility (aesthetic, microstructural and physical) and durability. Some pilot applications in real case studies are also reported. Recent research aimed at extending the phosphate treatment to other substrates is then illustrated. Finally, the strengths of the phosphate treatment are summarized, in comparison with alternative products, and some aspects needing future research are outlined. PMID:29617322

Highly selective anti-Prelog synthesis of optically active aryl alcohols by recombinant Escherichia coli expressing stereospecific alcohol dehydrogenase.

PubMed

Li, Ming; Nie, Yao; Mu, Xiao Qing; Zhang, Rongzhen; Xu, Yan

2016-07-03

Biocatalytic asymmetric synthesis has been widely used for preparation of optically active chiral alcohols as the important intermediates and precursors of active pharmaceutical ingredients. However, the available whole-cell system involving anti-Prelog specific alcohol dehydrogenase is yet limited. A recombinant Escherichia coli system expressing anti-Prelog stereospecific alcohol dehydrogenase from Candida parapsilosis was established as a whole-cell system for catalyzing asymmetric reduction of aryl ketones to anti-Prelog configured alcohols. Using 2-hydroxyacetophenone as the substrate, reaction factors including pH, cell status, and substrate concentration had obvious impacts on the outcome of whole-cell biocatalysis, and xylose was found to be an available auxiliary substrate for intracellular cofactor regeneration, by which (S)-1-phenyl-1,2-ethanediol was achieved with an optical purity of 97%e.e. and yield of 89% under the substrate concentration of 5 g/L. Additionally, the feasibility of the recombinant cells toward different aryl ketones was investigated, and most of the corresponding chiral alcohol products were obtained with an optical purity over 95%e.e. Therefore, the whole-cell system involving recombinant stereospecific alcohol dehydrogenase was constructed as an efficient biocatalyst for highly enantioselective anti-Prelog synthesis of optically active aryl alcohols and would be promising in the pharmaceutical industry.

An Investigational RNAi Therapeutic Targeting Glycolate Oxidase Reduces Oxalate Production in Models of Primary Hyperoxaluria

PubMed Central

Li, Xingsheng; Racie, Timothy; Hettinger, Julia; Bettencourt, Brian R.; Najafian, Nader; Haslett, Patrick; Fitzgerald, Kevin; Holmes, Ross P.; Erbe, David; Querbes, William; Knight, John

2017-01-01

Primary hyperoxaluria type 1 (PH1), an inherited rare disease of glyoxylate metabolism, arises from mutations in the enzyme alanine-glyoxylate aminotransferase. The resulting deficiency in this enzyme leads to abnormally high oxalate production resulting in calcium oxalate crystal formation and deposition in the kidney and many other tissues, with systemic oxalosis and ESRD being a common outcome. Although a small subset of patients manages the disease with vitamin B6 treatments, the only effective treatment for most is a combined liver-kidney transplant, which requires life-long immune suppression and carries significant mortality risk. In this report, we discuss the development of ALN-GO1, an investigational RNA interference (RNAi) therapeutic targeting glycolate oxidase, to deplete the substrate for oxalate synthesis. Subcutaneous administration of ALN-GO1 resulted in potent, dose-dependent, and durable silencing of the mRNA encoding glycolate oxidase and increased serum glycolate concentrations in wild-type mice, rats, and nonhuman primates. ALN-GO1 also increased urinary glycolate concentrations in normal nonhuman primates and in a genetic mouse model of PH1. Notably, ALN-GO1 reduced urinary oxalate concentration up to 50% after a single dose in the genetic mouse model of PH1, and up to 98% after multiple doses in a rat model of hyperoxaluria. These data demonstrate the ability of ALN-GO1 to reduce oxalate production in preclinical models of PH1 across multiple species and provide a clear rationale for clinical trials with this compound. PMID:27432743

Multi-wavelength dye concentration determination for enzymatic assays: evaluation of chromogenic para-nitrophenol over a wide pH range.

PubMed

Max, Jean-Joseph; Meddeb-Mouelhi, Fatma; Beauregard, Marc; Chapados, Camille

2012-12-01

Enzymatic assays need robust, rapid colorimetric methods that can follow ongoing reactions. For this, we developed a highly accurate, multi-wavelength detection method that could be used for several systems. Here, it was applied to the detection of para-nitrophenol (pNP) in basic and acidic solutions. First, we confirmed by factor analysis that pNP has two forms, with unique spectral characteristics in the 240 to 600 nm range: Phenol in acidic conditions absorbs in the lower range, whereas phenolate in basic conditions absorbs in the higher range. Thereafter, the method was used for the determination of species concentration. For this, the intensity measurements were made at only two wavelengths with a microtiter plate reader. This yielded total dye concentration, species relative abundance, and solution pH value. The method was applied to an enzymatic assay. For this, a chromogenic substrate that generates pNP after hydrolysis catalyzed by a lipase from the fungus Yarrowia lipolytica was used. Over the pH range of 3-11, accurate amounts of acidic and basic pNP were determined at 340 and 405 nm, respectively. This method surpasses the commonly used single-wavelength assay at 405 nm, which does not detect pNP acidic species, leading to activity underestimations. Moreover, alleviation of this pH-related problem by neutralization is not necessary. On the whole, the method developed is readily applicable to rapid high-throughput of enzymatic activity measurements over a wide pH range.

Regulation of activity in vitro and in vivo of three phospholipases B from Saccharomyces cerevisiae

PubMed Central

2004-01-01

The genome of the yeast, Saccharomyces cerevisiae, contains three highly similar genes coding for phospholipases B/lysophospholipases. These enzymes behave differently with respect to substrate preferences in vitro and relative contributions to phospholipid catabolism in vivo [Merkel, Fido, Mayr, Prüger, Raab, Zandonella, Kohlwein and Paltauf (1999) J. Biol. Chem. 274, 28121–28127]. It is shown in the present study that, in vitro, pH markedly affects the substrate preference of Plb1p and Plb2p, but not of Plb3p. At the pH optimum of 2.5–3.5, the order of substrate preference of Plb1p and Plb2p is PtdSer (phosphatidylserine)>PtdIns>PtdCho (phosphatidylcholine>PtdEtn (phosphatidylethanolamine). At pH values of 5 and above, the substrate preferences change to PtdCho=PtdEtn for Plb1p and PtdSer=PtdEtn for Plb2p. Accordingly, with cultured cells the ratio of PtdIns/PtdCho breakdown, as reflected in the ratio of GroPIns (glycerophosphoinositol)/GroPCho (glycerophosphocholine) released into the culture medium, is inversely related to the pH of the growth medium. This effect is ascribed to the pH response of Plb1p, because Plb2p does not contribute to the degradation of PtdIns and PtdCho in vivo. Bivalent and tervalent cations activate phospholipases B at pH 5.5, but are inhibitory at pH 2.5. Al3+ at a concentration of 20 mM increases Plb1p activity in vitro by 8-fold and leads to a 9-fold increase in GroPCho release by whole cells. In vivo, cycloheximide strongly inhibits the breakdown of PtdIns, and to a lesser extent PtdCho. However, Al3+-stimulated GroPCho release is almost completely inhibited by cycloheximide. Deletion of PLB3 leads to increased sensitivity to toxic Al3+. Addition of SDS or melittin to cultured cells leads to a significant increase in phospholipid degradation, which is insensitive to inhibition by cycloheximide. Deletion mutants defective in the PLB1 gene are significantly more resistant to SDS than are wild-type cells. PMID:15588231

Automatic pH Control and Soluble and Insoluble Substrate Input for Continuous Culture of Rumen Microorganisms

PubMed Central

Slyter, Leonard L.

1975-01-01

An artifical rumen continuous culture with pH control, automated input of water-soluble and water-insoluble substrates, controlled mixing of contents, and a collection system for gas is described. Images PMID:16350029

Utilisation of Chlorella vulgaris cell biomass for the production of enzymatic protein hydrolysates.

PubMed

Morris, Humberto J; Almarales, Angel; Carrillo, Olimpia; Bermúdez, Rosa C

2008-11-01

Studies on enzymatic hydrolysis of cell proteins in green microalgae Chlorella vulgaris 87/1 are described. Different proteases can be used for production of hydrolysates from ethanol extracted algae. The influence of reaction parameters on hydrolysis of extracted biomass with pancreatin was considered, and the composition of hydrolysates (Cv-PH) was investigated in relation to the starting materials. Significant changes in the degree of hydrolysis were observed only during the first 2h and it remained constant throughout the process. An enzyme-substrate ratio of 30-45 units/g algae, an algae concentration of 10-15% and pH values of 7.5-8.0 could be recommended. Differences in the chromatographic patterns of Cv-PH and a hot-extract from Chlorella biomass were observed. Adequate amounts of essential amino acids (44.7%) in relation to the reference pattern of FAO for human nutrition were found, except for sulfur amino acids. Cv-PH could be considered as a potential ingredient in the food industry.

Importance of water quality in container plant production

Treesearch

John M. Ruter

2013-01-01

High substrate pH is a major problem for producers of container-grown plants and seedlings. The primary cause of high substrate pH is irrigation water with high alkalinity. Alkalinity is defined as the capacity of water to neutralize acids. Some alkalinity in irrigation water is beneficial as it serves as a buffer to large swings in pH levels, but high alkalinity in...

Batch kinetics of Pseudomonas sp. growth on benzene. Modeling of product and substrate inhibitions.

PubMed

Monero, Alessandra; Lanza, Luca; Zilli, Mario; Sene, Luciane; Converti, Attilio

2003-01-01

Batch tests of benzene degradation were performed in liquid phase at 30 degrees C, pH 6.8 +/- 0.2, and 200 rpm in two 3-L stirred tank bioreactors, using the benzene-degrading bacterium Pseudomonas sp. NCIMB 9688. A relatively high starting biomass level (220-270 mg(X)/L) and starting benzene concentration ranging from 20 to 200 mg(S)/L were selected as conditions to investigate possible inhibition phenomena. Volumetric as well as specific rates of biomass formation and substrate consumption were calculated from experimental data of both growth and benzene degradation and used to propose and check a new overall kinetic model for cell growth simultaneously accounting for both product and substrate inhibitions. The results of the present study evidenced the occurrence of a competitive-type product inhibition due to 2-hydroxymuconic semialdehyde (K(iP)' = 0.902 mg(S)/L), which was stronger than the uncompetitive-type inhibition exerted by substrate (K(iS) = 7.69 mg(S)/L).

Batch and fixed-bed biosorption of Cd(II) from aqueous solution using immobilized Pleurotus ostreatus spent substrate.

PubMed

Jin, Yu; Teng, Chunying; Yu, Sumei; Song, Tao; Dong, Liying; Liang, Jinsong; Bai, Xin; Liu, Xuesheng; Hu, Xiaojing; Qu, Juanjuan

2018-01-01

To prevent the blockage in a continuous fix-bed system, Pleurotus Ostreatus spent substrate (POSS), a composite agricultural waste, was immobilized into granular adsorbents (IPOSS) with polymeric matrix, and used to remove Cd(II) from synthetic wastewater in batch experiment as well as in continuous fixed-bed column system. In batch experiment, higher pH, temperature and Cd(II) initial concentration were conducive to a higher biosorption capacity, and the maximum biosorption capacity reached up to 87.2 mg/g at Cd(II) initial concentration of 200 mg/L, pH 6 and 25 °C. The biosorption of Cd(II) onto IPOSS followed the Langmuir isotherm model with the maximum adsorption capacity(q max ) of 100 mg/g. The biosorption was an endothermic reaction and a spontaneous process based on positive value of ΔH 0 and negative value of ΔG 0 . In fixed-bed column system, higher bed depth, lower flow rate and influent Cd(II) concentration led to a longer breakthrough and exhaustion time, and the best performance (equilibrium uptake (q e ) of 14.4 mg, breakthrough time at 31 h and exhaustion time at 78 h) was achieved at a bed depth of 110 cm, a flow rate of 1.2 L/h and an influent concentration of 100 mg/L. Furthermore, regeneration experiment revealed a good reusability of IPOSS with 0.1 M HNO 3 as eluting agent during three cycles of adsorption and desorption. Cd(II) biosorption onto IPOSS mainly relied on a chemical process including ion exchange and complexation or coordination revealed by SEM-EDX, FTIR and XRD analysis. Copyright © 2017. Published by Elsevier Ltd.

Repeat-swap homology modeling of secondary active transporters: updated protocol and prediction of elevator-type mechanisms

PubMed Central

Vergara-Jaque, Ariela; Fenollar-Ferrer, Cristina; Kaufmann, Desirée; Forrest, Lucy R.

2015-01-01

Secondary active transporters are critical for neurotransmitter clearance and recycling during synaptic transmission and uptake of nutrients. These proteins mediate the movement of solutes against their concentration gradients, by using the energy released in the movement of ions down pre-existing concentration gradients. To achieve this, transporters conform to the so-called alternating-access hypothesis, whereby the protein adopts at least two conformations in which the substrate binding sites are exposed to one or other side of the membrane, but not both simultaneously. Structures of a bacterial homolog of neuronal glutamate transporters, GltPh, in several different conformational states have revealed that the protein structure is asymmetric in the outward- and inward-open states, and that the conformational change connecting them involves a elevator-like movement of a substrate binding domain across the membrane. The structural asymmetry is created by inverted-topology repeats, i.e., structural repeats with similar overall folds whose transmembrane topologies are related to each other by two-fold pseudo-symmetry around an axis parallel to the membrane plane. Inverted repeats have been found in around three-quarters of secondary transporter folds. Moreover, the (a)symmetry of these systems has been successfully used as a bioinformatic tool, called “repeat-swap modeling” to predict structural models of a transporter in one conformation using the known structure of the transporter in the complementary conformation as a template. Here, we describe an updated repeat-swap homology modeling protocol, and calibrate the accuracy of the method using GltPh, for which both inward- and outward-facing conformations are known. We then apply this repeat-swap homology modeling procedure to a concentrative nucleoside transporter, VcCNT, which has a three-dimensional arrangement related to that of GltPh. The repeat-swapped model of VcCNT predicts that nucleoside transport also occurs via an elevator-like mechanism. PMID:26388773

Effect of sulphur concentration on bioleaching of heavy metals from contaminated dredged sediments.

PubMed

Fang, D; Zhao, L; Yang, Z Q; Shan, H X; Gao, Y; Yang, Q

2009-11-01

The sulphur-based bioleaching process using sulphur-oxidizing bacteria (SOB) has been demonstrated to be a feasible technology for removing heavy metals from contaminated sediments, but the excess sulphur application will lead to the re-acidification of bioleached sediments. The objective of the present study was to examine the effect of sulphur concentration on the bioleaching of heavy metals from contaminated sediments, with the ultimate purpose of minimizing the sulphur addition. The results showed that the inoculation of 7% of indigenous SOB, containing 3.6 x 10(8) colony forming units (CFU) mL(-1), and addition of elemental sulphur as a substrate (0.5 to 7.0 g L(-1)) resulted in a sharp decrease in sediment pH from an initial pH 8.0 to pH 1.4-2.4 and an increase in ORP (oxidation-reduction potential) from -10 mV to 500 mV within 10 days of bioleaching. Although the increase in sulphur concentration enhanced the rates of pH reduction and ORP elevation, the bioleaching process with the addition of 3.0 g L(-1) of sulphur was already sufficient to reach conditions of acidity (pH < 2.0) and ORP (500 mV) necessary for a satisfactory removal of metals, and, at day 10, 71.8% of Cu, 58.2% of Zn, and 25.3% of Cr were removed from the sediments. During the bioleaching process, Zn removal increased with a reduction in pH, whereas the removal of Cu and Cr increased not only with a reduction in pH but also with an increase in ORP. Results of sequential selective extraction indicated that the final levels of metal removals were dependent on their speciation distribution in the original sediments, and after bioleaching those unremoved metals in the bioleached sediments mainly existed in the residual fraction.

Proline transport in Leishmania donovani amastigotes: dependence on pH gradients and membrane potential.

PubMed

Glaser, T A; Mukkada, A J

1992-03-01

Amastigotes of Leishmania donovani develop and multiply within the acidic phagolysosomes of mammalian macrophages. Isolated amastigotes are acidophilic; they catabolize substrates and synthesize macromolecules optimally at pH 5.5. Substrate transport in amastigotes has not been characterized. Here we show that amastigotes exhibit an uphill transport of proline (active transport) with an acid pH optimum (pH 5.5). It is dependent upon metabolic energy and is driven by proton motive force. Agents which selectively disturb the component forces of proton motive force, such as carbonyl cyanide chlorophenylhydrazone, nigericin and valinomycin, inhibit proline transport. Transport is sensitive to dicyclohexylcarbodiimide and insensitive to ouabain, demonstrating the involvement of a proton ATPase in the maintenance of proton motive force. It is suggested that the plasma membrane pH gradient probably makes the greatest contribution to proton motive force that drives substrate transport in the amastigote stage.

Improved specific productivity in cephalexin synthesis by immobilized PGA in silica magnetic micro-particles.

PubMed

Bernardino, Susana M S A; Fernandes, Pedro; Fonseca, Luís P

2010-12-01

There is a marked trend in pharmaceutical industry towards the replacement of classical organic methods by "green" alternatives that minimize or eliminate the generation of waste and avoid, where possible, the use of toxic and/or hazardous reagents and solvents. In this work the kinetically controlled synthesis of cephalexin by soluble and penicillin G acylase immobilized in sol-gel micro-particles with magnetic properties was performed in aqueous media with PGME and 7-ADCA as substrates, at different concentrations of substrate, temperature, pH, enzyme to substrate ratio and acyl donor to nucleophile ratio. Excess acyl donor had a strong effect on cephalexin productivity. A PGME/7-ADCA ratio of 3 was considered optimum. A maximum specific productivity of 5.9 mmol h(-1), gbiocatalyst(-1) at 160 mM 7-ADCA, 480 mM PGME and low enzyme to substrate ratio at 32.5 U mmol(-1) 7-ADCA was obtained with immobilized PGA in full aqueous medium, suggesting that diffusional limitations were minimized when compared with other commercial biocatalysts. A half-life of 133 h for the immobilized biocatalyst was estimated during cephalexin synthesis in the presence of 100 mM 7-ADCA and 300 mM PGME, in 50 mM Tris/HCl at pH 7.2 and 14°C. These results compare quite favorably with those previously reported for the kinetically controlled synthesis of cephalexin. © 2010 Wiley Periodicals, Inc.

Discovery and characterization of a thermostable two-domain GH6 endoglucanase from a compost metagenome.

PubMed

Jensen, Marianne S; Fredriksen, Lasse; MacKenzie, Alasdair K; Pope, Phillip B; Leiros, Ingar; Chylenski, Piotr; Williamson, Adele K; Christopeit, Tony; Østby, Heidi; Vaaje-Kolstad, Gustav; Eijsink, Vincent G H

2018-01-01

Enzymatic depolymerization of recalcitrant polysaccharides plays a key role in accessing the renewable energy stored within lignocellulosic biomass, and natural biodiversities may be explored to discover microbial enzymes that have evolved to conquer this task in various environments. Here, a metagenome from a thermophilic microbial community was mined to yield a novel, thermostable cellulase, named mgCel6A, with activity on an industrial cellulosic substrate (sulfite-pulped Norway spruce) and a glucomannanase side activity. The enzyme consists of a glycoside hydrolase family 6 catalytic domain (GH6) and a family 2 carbohydrate binding module (CBM2) that are connected by a linker rich in prolines and threonines. MgCel6A exhibited maximum activity at 85°C and pH 5.0 on carboxymethyl cellulose (CMC), but in prolonged incubations with the industrial substrate, the highest yields were obtained at 60°C, pH 6.0. Differential scanning calorimetry (DSC) indicated a Tm(app) of 76°C. Both functional data and the crystal structure, solved at 1.88 Å resolution, indicate that mgCel6A is an endoglucanase. Comparative studies with a truncated variant of the enzyme showed that the CBM increases substrate binding, while not affecting thermal stability. Importantly, at higher substrate concentrations the full-length enzyme was outperformed by the catalytic domain alone, underpinning previous suggestions that CBMs may be less useful in high-consistency bioprocessing.

Increasing surface enhanced Raman spectroscopy effect of RNA and DNA components by changing the pH of silver colloidal suspensions.

PubMed

Primera-Pedrozo, Oliva M; Rodríguez, Gabriela Del Mar; Castellanos, Jorge; Felix-Rivera, Hilsamar; Resto, Oscar; Hernández-Rivera, Samuel P

2012-02-15

This work focused on establishing the parameters for enhancing the Raman signals of DNA and RNA constituents: nitrogenous bases, nucleosides and nucleotides, using metallic nanoparticles as surface enhanced Raman scattering substrates. Silver nanospheres were synthesized using sodium borohydride as a reducing agent and sodium citrate as a capping agent. The prepared nanoparticles had a surface plasmon band at ∼384nm and an average size of 12±3nm. The nanoparticles' surface charge was manipulated by changing the pH of the Ag colloidal suspensions in the range of 1-13. Low concentrations as 0.7μM were detected under the experimental conditions. The optimum pH values were: 7 for adenine, 9 for AMP, 5 for adenosine, 7 for dAMP and 11 for deoxyadenosine. Copyright © 2011 Elsevier B.V. All rights reserved.

Box-Behnken methodology for Cr (VI) and leather dyes removal by an eco-friendly biosorbent: F. vesiculosus.

PubMed

Cobas, M; Sanromán, M A; Pazos, M

2014-05-01

This study focused on leather industrial effluents treatment by biosorption using Fucus vesiculosus as low-cost adsorbent. These effluents are yellowish-brown color and high concentration of Cr (VI). Therefore, biosorption process was optimized using response surface methodology based on Box-Behnken design operating with a simulated leather effluent obtained by mixture of Cr (VI) solution and four leather dyes. The key variables selected were initial solution pH, biomass dosage and CaCl2 concentration in the pretreatment stage. The statistical analysis shows that pH has a negligible effect, being the biomass dosage and CaCl2 concentration the most significant variables. At optimal conditions, 98% of Cr (VI) and 88% of dyes removal can be achieved. Freundlich fitted better to the obtained equilibrium data for all studied systems than Temkin, Langmuir or D-R models. In addition, the use of the final biosorbent as support-substrate to grown of enzyme producer fungi, Pleurotus ostreatus, was also demonstrated. Copyright © 2014 Elsevier Ltd. All rights reserved.

Functionalized vertically aligned ZnO nanorods for application in electrolyte-insulator-semiconductor based pH sensors and label-free immuno-sensors

NASA Astrophysics Data System (ADS)

Kumar, Narendra; Senapati, Sujata; Kumar, Satyendra; Kumar, Jitendra; Panda, Siddhartha

2016-04-01

Vertically aligned ZnO nanorods were grown on a SiO2/Si surface by optimization of the temperature and atmosphere for annealing of the seed. The seed layer annealed at 500 °C in vacuum provided well separated and uniform seeds which also provided the best condition to get densely packed, uniformly distributed, and vertically aligned nanorods. These nanorods grown on the substrates were used to fabricate electrolyte-insulator-semiconductor (EIS) devices for pH sensing. Etching of ZnO at acidic pH prevents the direct use of nanorods for pH sensing. Therefore, the nanorods functionalised with 3-aminopropyltriethoxysilane (APTES) were utilized for pH sensing and showed the pH sensitivity of 50.1 mV/pH. APTES is also known to be used as a linker to immobilize biomolecules (such as antibodies). The EIS device with APTES functionalized nanorods was used for the label free detection of prostate-specific antigen (PSA). Finally, voltage shifts of 23 mV and 35 mV were observed with PSA concentrations of 1 ng/ml and 100 ng/ml, respectively.

[Biodegradation characteristics of o-chlorophenol with photosynthetic bacteria PSB-1D].

PubMed

Hu, Xiao-min; Dong, Yi-hu; Li, Liang; Lu, Juan; He, Ying-dian; Gao, Yang

2010-07-01

A strain of photosynthetic bacteria named PSB-1D with degradation of o-chlorophenol (2-CP) was isolated and screened from the shallow substrate sludge in downstream side of the sewage outfall of an insecticide factory. The PSB-1D is identified preliminarily as Rhodopseudomonas sp. according to its colony and cell morphological properties, physiological biochemical characteristics and absorption spectrum analysis of living cells. The experiments results of relationship between PSB-1D growth and o-chlorophenol degradation showed that the degradation rate of o-chlorophenol was up to 57.26% after 7 days cultural time. The main environmental factors including way of illumination and oxygen, initial pH, cultural temperature, illumination intensity had distinctly influenced on the o-chlorophenol degradation with PSB-1D. The results showed that the optimum conditions were as following: an anaerobic light, pH 7.0, temperature 30 degrees C, illumination intensity 4000 lx,initial o-chlorophenol concentration 50 mg/L. Under that cultural condition, the degradation rate of o-chlorophenol could reach to 62.08%. The degradation kinetic data fitted the Andrews model well. In addition, the biodegradation process of o-chlorophenol can be well described by enzymatic reaction of high concentration inhibition, with the maximum substrate utilization rate 0.309 d(-1), Michaelis-Menten constant 2.733 mg/L, inhibitory constant 230.15 mg/L respectively.

PLLA scaffolds surface-engineered via poly (propylene imine) dendrimers for improvement on its biocompatibility/controlled pH biodegradability

NASA Astrophysics Data System (ADS)

Ganjalinia, Atiyeah.; Akbari, Somaye.; Solouk, Atefeh.

2017-02-01

Novel aminolyzed Poly (L) Lactic Acid (PLLA) films and electrospun nanofibrous scaffolds were fabricated and characterized as potential substrates for tissue engineering. The second generation polypropylene imine dendrimer (PPI-G2) was used as the aminolysis agent to functionalize the inert surface of PLLA substrates directly without any pre-modification process. The effect of the solvent type, G2 concentration, reaction temperature and time were studied by following weight reduction percentage, FTIR and contact angle measurements due to determined optimum conditions. In addition, the modified scaffolds abbreviated by PLLA/G2 were analyzed using mechanical properties, SEM images and dye assays as host-guest modeling. The results indicate that under the 0.5 (wt.%) G2 concentration, ethanol as the solvent, room temperature and 4 h of treatment, the optimum conditions were obtained. It was shown that the hydrophilic properties of PLLA/G2 were greatly enhanced. Also, pH value analysis revealed that after 4 weeks, the biodegradation of PLLA caused massive immune cells infusion and inflammation in the medium through increasing the acidic rate by secretion the lactic acid, whereas the PLLA/G2 scaffolds greatly reduced and stabilize the acidic rate through aminolysis reaction. Finally, promoted cell adhesion and viability underlined the favorable properties of PLLA/G2 scaffolds as a biodegradable biomaterial for biomedical implants.

MODELING SUBSTRATE TRANSPORT INTO BIOFILMS: ROLE OF MULTIPLE IONS AND PH EFFECTS

EPA Science Inventory

Steady-state substrate utilization in biofilms has traditionally been modeled by coupling Fickian diffusion with Monod reaction kinetics. An inherent assumption in most of the previous models was that the pH remains constant within the biofilm. Experiments have shown differences ...

Monitoring the degrafting of polyelectrolyte brushes by using surface gradients

NASA Astrophysics Data System (ADS)

Ko, Yeongun; Genzer, Jan

Polymer brushes comprise densely grafted polymer chains on surfaces, which possess high stability and high concentration of reactive centers per unit area compared to physisorbed polymer film. Polymer brushes are employed in many applications, including anti-fouling surfaces, cell adhesive surfaces, responsive surfaces, low-friction surfaces, etc. Recently, researchers reported that charged (or chargeable) polymer brushes can be degrafted from substrate while incubated in buffer solutions. Based on previous experiments conducted in our group and by others, we assume that chain degrafting results from the hydrolysis of Si-O groups in head-group of the initiator and/or the ester groups in main body of the initiator. The kinetic of hydrolysis is affected by mechanical forces acting on the initiator. Those forces depend on the molecular weight and the grafting density of the brush, and the concentration and distribution of charges along the macromolecule (tuned by pH - for weak electrolytes - and concentration of external salt). In this work, we study the stability of poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) brushes in two solvents (ethanol and water) at various pH values in water and under different levels of external salt concentration. National Science Foundation.

Bioelectrochemical desalination and electricity generation in microbial desalination cell with dewatered sludge as fuel.

PubMed

Meng, Fanyu; Jiang, Junqiu; Zhao, Qingliang; Wang, Kun; Zhang, Guodong; Fan, Qingxin; Wei, Liangliang; Ding, Jing; Zheng, Zhen

2014-04-01

Microbial desalination cells (MDCs) with common liquid anodic substrate exhibit a slow startup and destructive pH drop, and abiotic cathodes have high cost and low sustainability. A biocathode MDC with dewatered sludge as fuel was developed for synergistic desalination, electricity generation and sludge stabilization. Experimental results indicated that the startup period was reduced to 3d, anodic pH was maintained between 6.6 and 7.6, and high stability was shown under long-term operation (300d). When initial NaCl concentrations were 5 and 10g/L, the desalinization rates during stable operation were 46.37±1.14% and 40.74±0.89%, respectively. The maximum power output of 3.178W/m(3) with open circuit voltage (OCV) of 1.118V was produced on 130d. After 300d, 25.71±0.15% of organic matter was removed. These results demonstrated that dewatered sludge was an appropriate anodic substrate to enhance MDC stability for desalination and electricity generation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Beneficial Use of Drilling Waste - A Wetland Restoration Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pioneer Natural Resources

1999-07-01

The results obtained thus far are promising with regard to the low toxicity of restored drill cuttings (particularly the Cameron substrate) with increasing levels of salinity. Water extraction, acid digestion, and interstitial water samples from the restored drill cuttings, as well as redox potential, soil pH and interstitial nitrate/ammonium concentrations, and the photosynthetic response, have been determined for the baseline fresh water condition (June-August 1998), at 9ppt (September-November 1998), at 18ppt (December-February 1998,1999), and at 27ppt (currently underway). Salinities will be brought to full-strength seawater (36ppt) on May 24, 1999. The Cameron drill cuttings are remarkably similar to dredge spoil,more » which is currently being used as a wetland creation substrate. The few elements that were extracted into the interstitial water were primarily cations (Ca, K, Mg) and were not elevated to a level that would pose a threat to wetlands productivity. Swaco drill cuttings remained high in aluminum with concomitant high pH, which likely resulted in limited plant productivity through hindered nutrient uptake.« less

Role of Peroxidase in Lignification of Tobacco Cells 1

PubMed Central

Mäder, Michael; Füssl, Resi

1982-01-01

Coniferyl alcohol is the primary substrate for peroxidase-mediated lignification, a process which depends on the generation of H2O2 by NADH oxidation. We measured the concentrations of various phenols (synthetic and natural) at which maximal enhancement of NADH oxidation occurs. Coniferyl alcohol was found to stimulate NADH oxidation at a much lower concentration (0.01 mm) than other natural or synthetic phenols (1-100 mm). In addition, coniferyl alcohol prevented the conversion of active peroxidase into the inactive intermediate compound III—which is usually formed in the presence of NADH—at equally low concentrations. This conversion was found to be a prerequisite for stimulation of NADH-oxidation, but it was not necessarily connected to stimulation. The oxidation of NADH and coniferyl alcohol (or guaiacol) can occur simultaneously, but there is a strong competitive interaction between these two substrates. At pH 5, the presence of NADH at concentrations 30 to 60 times lower than the phenols completely prevents their oxidation. The results are discussed in relation to the role of cell wall peroxidases in conversion of coniferyl alcohol to lignin and in formation of H2O2. PMID:16662627

Carbon nanotube sensors integrated inside a microfluidic channel for water quality monitoring

NASA Astrophysics Data System (ADS)

Liu, Yu; Li, Xinghui; Dokmeci, Mehmet R.; Wang, Ming L.

2011-04-01

Single-walled carbon nanotubes (SWNTs) with their unique electrical properties and large surface area are remarkable materials for detecting low concentration of toxic and hazardous chemicals (both from the gaseous and liquid phases). Ionic adsorbates in water will attach on to SWNTs and drastically alter their electrical properties. Several SWNTs based pH and chemical sensors have been demonstrated. However, most of them require external components to test and analyze the response of SWNTs to ions inside the liquid samples. Here, we report a water quality monitoring sensor composed of SWNTs integrated inside microfluidic channels and on-chip testing components with a wireless transmission board. To detect multiple analytes in water requires the functionalization of SWNTs with different chemistries. In addition, microfluidic channels are used to guide liquid samples to individual nanotube sensors in an efficient manner. Furthermore, the microfluidic system enables sample mixing and separation before testing. To realize the nanosensors, first microelectrodes were fabricated on an oxidized silicon substrate. Next, PDMS micro channels were fabricated and bonded on the substrate. These channels can be incorporated with a microfluidic system which can be designed to manipulate different analytes for specific molecule detection. Low temperature, solution based Dielectrophoretic (DEP) assembly was conducted inside this microfluidic system which successfully bridged SWNTs between the microelectrodes. The SWNTs sensors were next characterized with different pH buffer solutions. The resistance of SWNTs had a linearly increase as the pH values ranged from 5 to 8. The nanosensor incorporated within the microfluidic system is a versatile platform and can be utilized to detect numerous water pollutants, including toxic organics and microorganisms down to low concentrations. On-chip processing and wireless transmission enables the realization of a full autonomous system for real time monitoring of water quality.

Enrichment of Secondary Wastewater Sludge for Production of Hydrogen from Crude Glycerol and Comparative Evaluation of Mono-, Co- and Mixed-Culture Systems

PubMed Central

Pachapur, Vinayak Laxman; Kutty, Prianka; Brar, Satinder Kaur; Ramirez, Antonio Avalos

2016-01-01

Anaerobic digestion using mixed-culture with broader choice of pretreatments for hydrogen (H2) production was investigated. Pretreatment of wastewater sludge by five methods, such as heat, acid, base, microwave and chloroform was conducted using crude glycerol (CG) as substrate. Results for heat treatment (100 °C for 15 min) showed the highest H2 production across the pretreatment methods with 15.18 ± 0.26 mmol/L of medium at 30 °C in absence of complex media and nutrient solution. The heat-pretreated inoculum eliminated H2 consuming bacteria and produced twice as much as H2 as compared to other pretreatment methods. The fermentation conditions, such as CG concentration (1.23 to 24 g/L), percentage of inoculum size (InS) (1.23% to 24% v/v) along with initial pH (2.98 to 8.02) was tested using central composite design (CCD) with H2 production as response parameter. The maximum H2 production of 29.43 ± 0.71 mmol/L obtained at optimum conditions of 20 g/L CG, 20% InS and pH 7. Symbiotic correlation of pH over CG and InS had a significant (p-value: 0.0011) contribution to H2 production. The mixed-culture possessed better natural acclimatization activity for degrading CG, at substrate inhibition concentration and provided efficient inoculum conditions in comparison to mono- and co-culture systems. The heat pretreatment step used across mixed-culture system is simple, cheap and industrially applicable in comparison to mono-/co-culture systems for H2 production. PMID:26771607

Glucose ameliorates the metabolic profile and mitochondrial function of platelet concentrates during storage in autologous plasma

PubMed Central

Amorini, Angela M.; Tuttobene, Michele; Tomasello, Flora M.; Biazzo, Filomena; Gullotta, Stefano; De Pinto, Vito; Lazzarino, Giuseppe; Tavazzi, Barbara

2013-01-01

Background It is essential that the quality of platelet metabolism and function remains high during storage in order to ensure the clinical effectiveness of a platelet transfusion. New storage conditions and additives are constantly evaluated in order to achieve this. Using glucose as a substrate is controversial because of its potential connection with increased lactate production and decreased pH, both parameters triggering the platelet lesion during storage. Materials and methods In this study, we analysed the morphological status and metabolic profile of platelets stored for various periods in autologous plasma enriched with increasing glucose concentrations (13.75, 27.5 and 55 mM). After 0, 2, 4, 6 and 8 days, high energy phosphates (ATP, GTP, ADP, AMP), oxypurines (hypoxanthine, xanthine, uric acid), lactate, pH, mitochondrial function, cell lysis and morphology, were evaluated. Results The data showed a significant dose-dependent improvement of the different parameters in platelets stored with increasing glucose, compared to what detected in controls. Interestingly, this phenomenon was more marked at the highest level of glucose tested and in the period of time generally used for platelet transfusion (0–6 days). Conclusion These results indicate that the addition of glucose during platelet storage ameliorates, in a dose-dependent manner, the biochemical parameters related to energy metabolism and mitochondrial function. Since there was no correspondence between glucose addition, lactate increase and pH decrease in our experiments, it is conceivable that platelet derangement during storage is not directly caused by glucose through an increase of anaerobic glycolysis, but rather to a loss of mitochondrial functions caused by reduced substrate availability. PMID:22682337

Purification of peroxidase from Horseradish (Armoracia rusticana) roots.

PubMed

Lavery, Christopher B; Macinnis, Morgan C; Macdonald, M Jason; Williams, Joanna Bassey; Spencer, Colin A; Burke, Alicia A; Irwin, David J G; D'Cunha, Godwin B

2010-08-11

Peroxidase (EC 1.11.1.7) from horseradish ( Armoracia rusticana ) roots was purified using a simple, rapid, three-step procedure: ultrasonication, ammonium sulfate salt precipitation, and hydrophobic interaction chromatography on phenyl Sepharose CL-4B. The preparation gave an overall yield of 71%, 291-fold purification, and a high specific activity of 772 U mg(-1) protein. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the purified enzyme was homogeneous and had a molecular weight of approximately 40 kDa. The isolated enzyme had an isoelectric point of 8.8 and a Reinheitszahl value of 3.39 and was stable when stored in the presence of glycerol at -20 degrees C, with >95% retention of original enzyme activity for at least 6 months. Maximal activity of purified horseradish peroxidase (HRP) was obtained under different optimized conditions: substrate (guaiacol and H(2)O(2)) concentrations (0.5 and 0.3 mM, respectively), type of buffer (50 mM phosphate buffer), pH (7.0), time (1.0 min), and temperature of incubation (30 degrees C). In addition, the effect of HRP and H(2)O(2) in a neutral-buffered aqueous solution for the oxidation of phenol and 2-chlorophenol substrates was also studied. Different conditions including concentrations of phenol/2-chlorophenol, H(2)O(2), and enzyme, time, pH, and temperature were standardized for the maximal activity of HRP with these substrates; under these optimal conditions 89.6 and 91.4% oxidations of phenol and 2-chlorophenol were obtained, respectively. The data generated from this work could have direct implications in studies on the commercial production of this biotechnologically important enzyme and its stability in different media.

Carbonate species as OH- carriers for decreasing the pH gradient between cathode and anode in biological fuel cells.

PubMed

Torres, César I; Lee, Hyung-Sool; Rittmann, Bruce E

2008-12-01

Anodes of biological fuel cells (BFCs) normally must operate at a near-neutral pH in the presence of various ionic species required for the function of the biological catalyst (e.g., substrate, nutrients, and buffers). These ionic species are in higher concentration than protons (H+) and hydroxides (OH-); slow transport of H+ and OH- equivalents between anode and cathode compartments can lead to a large pH gradient that can inhibit the function of biological components, decrease voltage efficiency in BFCs, or both. We evaluate the use of carbonate species as OH- carriers from the cathode to the anode compartment. This is achieved by adding CO2 to the influent air in the cathode. CO2 is an acid that combines with OH- in the cathode to produce bicarbonate and carbonate. These species can migrate to the anode compartment as OH- carriers at a rate much greater than can OH- itself when the pH is not extremely high in the cathode compartment We demonstrate this concept by feeding different air/CO2 mixtures to the cathode of a dual-chamber microbial fuel cell (MFC) fed with acetate as substrate. Our results show a 45% increase in power density (from 1.9 to 2.8 W/m2) by feeding air augmented with 2-10% CO2. The cell voltage increased by as much as 120 mV, indicating that the pH gradient decreased by as much as 2 pH units. Analysis of the anode effluent showed an average increase of 4.9 mM in total carbonate, indicating that mostly carbonate was transferred from the cathode compartment This process provides a simple way to minimize potential losses in BFCs due to pH gradients between anode and cathode compartments.

Factors affecting Archaeal Lipid Compositions of the Sulfolobus Species

NASA Astrophysics Data System (ADS)

He, L.; Han, J.; Wei, Y.; Lin, L.; Wei, Y.; Zhang, C.

2010-12-01

Temperature is the best known variable affecting the distribution of the archaeal glycerol dibiphytanyl glycerol tetraethers (GDGTs) in marine and freshwater systems. Other variables such as pH, ionic strength, or bicarbonate concentration may also affect archaeal GDGTs in terrestrial systems. Studies of pure cultures can help us pinpoint the specific effects these variables may have on archaeal lipid distribution in natural environments. In this study, three Sulfolobus species (HG4, HB5-2, HB9-6) isolated from Tengchong hot springs (pH 2-3, temperature 73-90°C) in China were used to investigate the effects of temperature, pH, substrate, and type of strain on the composition of GDGTs. Results showed that increase in temperature had negative effects on the relative contents of GDGT-0 (no cyclopentyl rings), GDGT-1 (one cyclopentyl ring), GDGT-2 and GDGT-3 but positive effects on GDGT-4, GDGT-4', GDGT-5 and GDGT-5'. Increase in pH, on the other hand, had negative effects on GDGT-0, GDGT-1, GDGT-4', GDGT-5 and GDGT-5', and positive effects on GDGT-3 and GDGT-4. GDGT-2 remained relatively constant with changing pH. When the HG4 was grown on different substrates, GDGT-5 was five time more abundant in sucrose-grown cultures than in yeast extract- or sulfur- grown cultures, suggesting that carbohydrates may stimulate the production of GDGT-5. For all three species, the ring index (average number of rings) of GDGTs correlated positively with incubation temperature. In HG4, ring index was much lower at optimal pH (3.5) than at other pH values. Ring index of HB5-2 or HB9-6 is higher than that of HG4, suggesting that speciation may affect the degree of cyclization of GDGT of the Sulfolobus. These results indicate that individual archaeal lipids respond differently to changes in environmental variables, which may be also species specific.

Substrate and pH-Dependent Kinetic Profile of 3-Mercaptopropionate Dioxygenase from Pseudomonas aeruginosa.

PubMed

Fellner, Matthias; Aloi, Sekotilani; Tchesnokov, Egor P; Wilbanks, Sigurd M; Jameson, Guy N L

2016-03-08

Thiol dioxygenases catalyze the synthesis of sulfinic acids in a range of organisms from bacteria to mammals. A thiol dioxygenase from the bacterium Pseudomonas aeruginosa oxidizes both 3-mercaptopropionic acid and cysteine, with a ∼70 fold preference for 3-mercaptopropionic acid over all pHs. This substrate reactivity is widened compared to other thiol dioxygenases and was exploited in this investigation of the residues important for activity. A simple model incorporating two protonation events was used to fit profiles of the Michaelis-Menten parameters determined at different pH values for both substrates. The pKs determined using plots of k(cat)/Km differ at low pH, but not in a way easily attributable to protonation of the substrate alone and share a common value at higher pH. Plots of k(cat) versus pH are also quite different at low pH showing the monoprotonated ES complexes with 3-mercaptopropionic acid and cysteine have different pKs. At higher pH, k(cat) decreases sigmoidally with a similar pK regardless of substrate. Loss of reactivity at high pH is attributed to deprotonation of tyrosine 159 and its influence on dioxygen binding. A mechanism is proposed by which deprotonation of tyrosine 159 both blocks oxygen binding and concomitantly promotes cystine formation. Finally, the role of tyrosine 159 was further probed by production of a G95C variant that is able to form a cysteine-tyrosine crosslink homologous to that found in mammalian cysteine dioxygenases. Activity of this variant is severely impaired. Crystallography shows that when un-crosslinked, the cysteine thiol excludes tyrosine 159 from its native position, while kinetic analysis shows that the thioether bond impairs reactivity of the crosslinked form.

Mechanistic deductions from kinetic isotope effects and pH studies of pyridoxal phosphate dependent carbon-carbon lyases: Erwinia herbicola and Citrobacter freundii tyrosine phenol-lyase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kiick, D.M.; Phillips, R.S.

1988-09-20

The pH dependence of the kinetic parameters and primary deuterium isotope effects have been determined for tyrosine phenol-lyase from both Erwinia herbicola and Citrobacter freundii. The primary deuterium isotope effects indicate that proton abstraction from the 2-position of the substrate is partially rate-limiting for both enzymes. The C. freundii enzyme primary deuterium isotope effects (DV = 3.5 and D(V/Ktyr) = 2.5) are pH independent, indicating that tyrosine is not sticky (i.e., does not dissociate slower than it reacts to give products). Since Vmax for both tyrosine and the alternate substrate S-methyl-L-cysteine is also pH independent, substrate binds only to themore » correctly protonated form of the enzyme. For the E. herbicola enzyme, both Vmax and V/K for tyrosine or S-methyl-L-cysteine are pH dependent, as well as both DV and D(V/Ktyr). Thus, while both the protonated and unprotonated enzyme can bind substrate, and may be interconverted directly, only the unprotonated Michaelis complex is catalytically competent. At pH 9.5, DV = 2.5 and D(V/Ktyr) = 1.5. However, at pH 6.4 the isotope effect on both parameters is equal to 4.1. From these data, the forward commitment factor (cf = 5.2) and catalytic ratio (cvf = 1.1) for tyrosine and S-methyl-L-cysteine (cf = 2.2, cvf = 24) are calculated. Also, the Michaelis complex partition ratio (cf/cvf) for substrate and products is calculated to be 4.7 for tyrosine and 0.1 for S-methyl-L-cysteine.« less

Differences in the response of soil dehydrogenase activity to Cd contamination are determined by the different substrates used for its determination.

PubMed

Tan, Xiangping; Liu, Yanju; Yan, Kaihong; Wang, Ziquan; Lu, Guannan; He, Yike; He, Wenxiang

2017-02-01

Dehydrogenase activity (DHA) is an important indicator of heavy metal toxicity in contaminated soils. Different instances of DHA were determined using various substrates and which could affect the description of heavy metal toxicity. Currently, too few investigations have been done on selecting appropriate substrates. This study employed indoor simulation to determine soil DHA and its response to external cadmium (Cd) using two substrates (TTC and INT). Hormesis for DHA obtained using the TTC method (DHA-TTC) in low Cd concentration was observed which was quickly inhibited in high Cd concentration. While DHA obtained using the INT method (DHA-INT) decreased slowly when Cd concentration increased. The DHA-TTC and DHA-INT in soils at Cd concentration of 500 mg kg -1 decreased 86% and 53%, respectively, compared to the control. The dose-response relationship of Cd to DHA can be well simulated using the logistic model (p < 0.01), which indicated DHA could be used to indicate soil Cd toxicity. Multiple stepwise regression analysis revealed that total organic matter (TOC) is the major factor influencing the toxicity of Cd to DHA-TTC, while TOC, pH and cation exchange capacity (CEC) are major factors influencing the toxicity of Cd to DHA-INT. The different responses of soil DHA-TTC and DHA-INT to Cd are due to the differences in electron transport chain characteristics between TTC and INT, as well as the influence of soil properties. Although both DHA-TTC and DHA-INT can monitor soil Cd contamination, DHA-INT is recommended as a superior bio-indicator to indicate and assess contamination of Cd in soil. Copyright © 2016 Elsevier Ltd. All rights reserved.

Oxidation of monohydric phenol substrates by tyrosinase. An oximetric study.

PubMed

Naish-Byfield, S; Riley, P A

1992-11-15

The purity of commercially available mushroom tyrosinase was investigated by non-denaturing PAGE. Most of the protein in the preparation migrated as a single band under these conditions. This band contained both tyrosinase and dopa oxidase activity. No other activity of either classification was found in the preparation. Oxygen consumption by tyrosinase during oxidation of the monohydric phenol substrates tyrosine and 4-hydroxyanisole (4HA) was monitored by oximetry in order to determine the stoichiometry of the reactions. For complete oxidation, the molar ratio of oxygen: 4HA was 1:1. Under identical conditions, oxidation of tyrosine required 1.5 mol of oxygen/mol of tyrosine. The additional oxygen uptake during tyrosine oxidation is due to the internal cyclization of dopaquinone to form cyclodopa, which undergoes a redox reaction with dopaquinone to form dopachrome and dopa, which is then oxidized by the enzyme, leading to an additional 0.5 mol of oxygen/mol of original substrate. Oxygen consumption for complete oxidation of 200 nmol of 4HA was constant over a range of concentrations of tyrosinase of 33-330 units/ml of substrate. The maximum rate of reaction was directly proportional to the concentration of tyrosinase, whereas the length of the lag phase decreased non-linearly with increasing tyrosinase concentration. Activation of the enzyme by exposure to citrate was not seen, nor was the lag phase abolished by exposure of the enzyme to low pH. Michaelis-Menten analysis of tyrosinase in which the lag phase is abolished by pre-exposure of the enzyme to a low concentration of dithiothreitol gave Km values for tyrosine and 4HA of 153 and 20 microM respectively.

Mechanism-based inactivation of dopamine beta-hydroxylase by p-cresol and related alkylphenols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goodhart, P.J.; DeWolf, W.E. Jr.; Kruse, L.I.

1987-05-05

The mechanism-based inhibition of dopamine beta-hydroxylase by p-cresol (4-methylphenol) and other simple structural analogues of dopamine, which lack a basic side-chain nitrogen, is reported. p-Cresol binds DBH by a mechanism that is kinetically indistinguishable from normal dopamine substrate binding. Under conditions (pH 6.6) of random oxygen and phenethylamine substrate addition p-cresol adds randomly, whereas at pH 4.5 or in the presence of fumarate activator addition of p-cresol precedes oxygen binding as is observed with phenethylamine substrate. p-Cresol is shown to be a rapid (kinact = 2.0 min-1, pH 5.0) mechanism-based inactivator of DBH. This inactivation exhibits pseudo-first-order kinetics, is irreversible,more » is prevented by tyramine substrate or competitive inhibitor, and is dependent upon oxygen and ascorbic acid cosubstrates. Inhibition occurs with partial covalent incorporation of p-cresol into DBH. A plot of -log kinact vs. pH shows maximal inactivation occurs at pH 5.0 with dependence upon enzymatic groups with apparent pK values of 4.51 +/- 0.06 and 5.12 +/- 0.06. p-Cresol and related alkylphenols, unlike other mechanism-based inhibitors of DBH, lack a latent electrophile. These inhibitors are postulated to covalently modify DBH by a direct insertion of an aberrant substrate-derived benzylic radical into an active site residue.« less

Calcium dependent formation of tubular assemblies by recombinant S-layer proteins in vivo and in vitro

NASA Astrophysics Data System (ADS)

Korkmaz, Nuriye; Ostermann, Kai; Rödel, Gerhard

2011-03-01

Surface layer proteins have the appealing property to self-assemble in nanosized arrays in solution and on solid substrates. In this work, we characterize the formation of assembly structures of the recombinant surface layer protein SbsC of Geobacillus stearothermophilus ATTC 12980, which was tagged with enhanced green fluorescent protein and expressed in the yeast Saccharomyces cerevisiae. The tubular structures formed by the protein in vivo are retained upon bursting the cells by osmotic shock; however, their average length is decreased. During dialysis, monomers obtained by treatment with chaotropic chemicals recrystallize again to form tube-like structures. This process is strictly dependent on calcium (Ca2 + ) ions, with an optimal concentration of 10 mM. Further increase of the Ca2 + concentration results in multiple non-productive nucleation points. We further show that the lengths of the S-layer assemblies increase with time and can be controlled by pH. After 48 h, the average length at pH 9.0 is 4.13 µm compared to 2.69 µm at pH 5.5. Successful chemical deposition of platinum indicates the potential of recrystallized mSbsC-eGFP structures for nanobiotechnological applications.

Microbial ecological succession during municipal solid waste decomposition.

PubMed

Staley, Bryan F; de Los Reyes, Francis L; Wang, Ling; Barlaz, Morton A

2018-04-28

The decomposition of landfilled refuse proceeds through distinct phases, each defined by varying environmental factors such as volatile fatty acid concentration, pH, and substrate quality. The succession of microbial communities in response to these changing conditions was monitored in a laboratory-scale simulated landfill to minimize measurement difficulties experienced at field scale. 16S rRNA gene sequences retrieved at separate stages of decomposition showed significant succession in both Bacteria and methanogenic Archaea. A majority of Bacteria sequences in landfilled refuse belong to members of the phylum Firmicutes, while Proteobacteria levels fluctuated and Bacteroidetes levels increased as decomposition proceeded. Roughly 44% of archaeal sequences retrieved under conditions of low pH and high acetate were strictly hydrogenotrophic (Methanomicrobiales, Methanobacteriales). Methanosarcina was present at all stages of decomposition. Correspondence analysis showed bacterial population shifts were attributed to carboxylic acid concentration and solids hydrolysis, while archaeal populations were affected to a higher degree by pH. T-RFLP analysis showed specific taxonomic groups responded differently and exhibited unique responses during decomposition, suggesting that species composition and abundance within Bacteria and Archaea are highly dynamic. This study shows landfill microbial demographics are highly variable across both spatial and temporal transects.

Rapid detection of ciprofloxacin effects on Fusarium graminearum and F. avenaceum cells in modulating environmental pH using a reactive, non-toxic food-dye indicator.

PubMed

Yuan, Xiakun; Goh, Yit Kheng; Low, Nicholas; Vujanovic, Vladimir

2011-09-01

The objective of the study was to assess the effect of ciprofloxacin antibiotic on the physiological or phenotypic characteristics of food-borne toxigenic Fusarium graminearum and F. avenaceum molds under in vitro conditions. In the presence of ciprofloxacin, Fusarium mycelia growth and morphology were altered based on the antibiotic concentration range used. Results showed that ciprofloxacin in concentrations ≥40μg/mL induced chlamydospore formation in Fusaria and as such, this antibiotic should be considered as an important abiotic stress factor and growth inhibitor. A novel method was investigated to correlate chlamydospore formation with the colour changes observed in FD&C Green Number 3, a common water soluble food dye. The antibiotic-treated F. graminearum and F. avenaceum isolates produced chamydospores, which in turn altered environmental pH with concomitant changes in the colour and intensity of the dye. The colour changes observed as a function of environmental pH were supported by instrumental methods (pH meter and spectroscopy), and a commercial pH indicator (thymol blue) results. In conclusion, we propose that FD&C Green Number 3 can be used as an accurate indicator for the rapid assessment of Fusarium molds when grown on ciprofloxacin antibiotic-containing substrate. Special emphasis should be given to an indirect risk assessment of antibiotic effects on toxic molds. Copyright © 2011 Elsevier B.V. All rights reserved.

Addition of citrate to Acidithiobacillus ferrooxidans cultures enables precipitate-free growth at elevated pH and reduces ferric inhibition.

PubMed

Li, Xiaozheng; Mercado, Roel; Kernan, Timothy; West, Alan C; Banta, Scott

2014-10-01

Acidithiobacillus ferrooxidans is an acidophilic chemolithoautotroph that is important in biomining and other biotechnological operations. The cells are able to oxidize inorganic iron, but the insolubility and product inhibition by Fe(3+) complicates characterization of these cultures. Here we explore the growth kinetics of A. ferrooxidans in iron-based medium in a pH range from 1.6 to 2.2. It was found that as the pH was increased from 1.6 to 2.0, the maintenance coefficient decreased while both the growth kinetics and maximum cell yield increased in the precipitate-free, low Fe(2+) concentration medium. In higher iron media a similar trend was observed at low pH, but the formation of precipitates at higher pH (2.0) hampered cell growth and lowered the specific growth rate and maximum cell yield. In order to eliminate ferric precipitates, chelating agents were introduced into the medium. Citric acid was found to be relatively non-toxic and did not appear to interfere with iron oxidation at a maximum concentration of 70 mM. Inclusion of citric acid prevented precipitation and A. ferrooxidans growth parameters resumed their trends as a function of pH. The addition of citrate also decreased the apparent substrate saturation constant (KS ) indicating a reduction in the competitive inhibition of growth by ferric ions. These results indicate that continuous cultures of A. ferrooxidans in the presence of citrate at elevated pH will enable enhanced cell yields and productivities. This will be critical as these cells are used in the development of new biotechnological applications such as electrofuel production. © 2014 Wiley Periodicals, Inc.

In vitro fermentation characteristics of novel fibers, coconut endosperm fiber and chicory pulp, using canine fecal inoculum.

PubMed

de Godoy, M R C; Mitsuhashi, Y; Bauer, L L; Fahey, G C; Buff, P R; Swanson, K S

2015-01-01

The objective of this experiment was to determine the effects of in vitro fermentation of coconut endosperm fiber (CEF), chicory pulp (CHP), and selective blends of these substrates on SCFA production and changes in microbiota using canine fecal inocula. A total of 6 individual substrates, including short-chain fructooligosaccharide (scFOS; a well-established prebiotic source), pectin (PEC; used as a positive control), pelletized cellulose (PC; used as a negative control), beet pulp (BP; considered the gold standard fiber source in pet foods), CEF, and CHP, and 3 CEF:CHP blends (75:25% CEF:CHP [B1], 50:50% CEF:CHP [B2], and 25:75% CEF:CHP [B3]) were tested. Triplicate samples of each substrate were fermented for 0, 8, and 16 h after inoculation. A significant substrate × time interaction (P < 0.05) was observed for pH change and acetate, propionate, butyrate, and total SCFA concentrations. After 8 and 16 h, pH change was greatest for scFOS (-2.0 and -3.0, respectively) and smallest for PC (0.0 and -0.1, respectively). After 16 h, CEF had a greater butyrate concentration than CHP and all the CEF:CHP blends and it was not different than PEC. The substrate × time interaction was significant for bifidobacteria (P < 0.05) and lactobacilli (P < 0.05). After 8 h, bifidobacteria was greatest for BP and lowest for PC (12.7 and 10.0 log10 cfu/tube, respectively). After 16 h, PC had the lowest and scFOS had the greatest bifidobacteria (6.7 and 13.3 log10 cfu/tube, respectively). In general, CEF, CHP, and their blends had similar bifidobacteria populations after 8 and 16 h of fermentation when compared with BP and scFOS. After 16 h, lactobacilli populations were greatest for B1, B2, B3, BP, and scFOS, intermediate for PEC, and lowest for PC (P < 0.05). Overall, our data suggest that CEF had a butyrogenic effect and that CEF, CHP, and their blends had similar bifidobacteria and lactobacilli populations as popular prebiotic and fiber substrates. Future research should investigate the effects of CEF, CHP, and their blends on gastrointestinal health and fecal quality in dogs.

Study of Local Herb Potency as Rumen Modifier: The Effect of Red Ginger (Zingiber officinale Var.Rubrum) on Parameters of Ruminal Fermentation In Vitro

NASA Astrophysics Data System (ADS)

Kurniawati, A.; Widodo; Artama, W. T.; Yusiati, L. M.

2018-02-01

Essential oil is one of rumen modifier alternatives due to its antimicrobial property. Red ginger is one of local herbs with high essential oil content. The effect of red ginger on rumen fermentation parameters was studied in this research using in vitro gas production method. Five level of red ginger meal was added to the diet to meet final essential oil concentration in fermentation medium of 0, 25, 50, 75 and 100 mg/L. Substrate of fermentation as microbial feed composed of Penisetum hybride, rice bran, and wheat pollard in ratio 60:20:20 DM basis. Fermentation was carried out for 24 h at 39°C. Total gas production was measured at the end of incubation and sample for methane analysis was taken. Medium sample was taken for analysis of pH, ammonium and VFA concentration, microbial protein and protozoa number. Data showed that addition of red ginger in the diet did not affect the pH, ammonia and VFA concentration, microbial protein and also protozoa number. However, red ginger addition significantly decrease ammonia concentration in all treatment. It could be concluded that addition of red ginger in the diet reduced degradation protein in the rumen as illustrated in lower ammonia concentration.

Fate and distribution of pharmaceutically active compounds in mesocosm constructed wetlands.

PubMed

He, Yujie; Sutton, Nora B; Lei, Yu; Rijnaarts, Huub H M; Langenhoff, Alette A M

2018-05-22

Removal of pharmaceutically active compounds (PhACs) in constructed wetlands (CWs) is a complex interplay of different processes. We studied fate and distribution of seven PhACs (caffeine, CAF; naproxen, NAP; metoprolol, MET; propranolol, PRO; ibuprofen, IBP; carbamazepine, CBZ; diclofenac, DFC) in mesocosm CWs and effects of irradiation via pre-photocatalysis, substrate composition (mainly sediment) through addition of litter (dead plant biomass), and plants. CWs showed high removal of CAF, NAP, MET, PRO, and IBP (79-99%). All seven PhACs were detected in substrate and plant tissues as well as IBP intermediates. Estimated PhAC mass balance showed that sorption dominated PRO removal in CWs while other PhACs were mainly removed by biodegradation and/or phytodegradation. Pre-photocatalysis significantly increased removal of PhACs except for CAF and IBP, and decreased accumulation of PhACs in substrate and plant tissues of the following wetland compartment. Litter addition in CW significantly enhanced removal of PRO and CBZ via biodegradation and/or phytodegradation. Plants played an essential and positive role in removing PhACs, resulting from direct phytoremediation and indirectly enhancing sorption and biodegradation. Our study provides knowledge to understand removal mechanisms of PhACs in CWs and to potentially enhance PhAC removal by developing pre-photocatalysis, adding dead plant biomass, and optimizing vegetation. Copyright © 2018 Elsevier B.V. All rights reserved.

Enzyme characteristics of aminotransferase FumI of Sphingopyxis sp. MTA144 for deamination of hydrolyzed fumonisin B₁.

PubMed

Hartinger, Doris; Schwartz, Heidi; Hametner, Christian; Schatzmayr, Gerd; Haltrich, Dietmar; Moll, Wulf-Dieter

2011-08-01

Fumonisins are carcinogenic mycotoxins that are frequently found as natural contaminants in maize from warm climate regions around the world. The aminotransferase FumI is encoded as part of a gene cluster of Sphingopyxis sp. MTA144, which enables this bacterial strain to degrade fumonisin B(1) and related fumonisins. FumI catalyzes the deamination of the first intermediate of the catabolic pathway, hydrolyzed fumonisin B(1). We used a preparation of purified, His-tagged FumI, produced recombinantly in Escherichia coli in soluble form, for enzyme characterization. The structure of the reaction product was studied by NMR and identified as 2-keto hydrolyzed fumonisin B(1). Pyruvate was found to be the preferred co-substrate and amino group receptor (K (M) = 490 μM at 10 μM hydrolyzed fumonisin B(1)) of FumI, but other α-keto acids were also accepted as co-substrates. Addition of the co-enzyme pyridoxal phosphate to the enzyme preparation enhanced activity, and saturation was already reached at the lowest tested concentration of 10 μM. The enzyme showed activity in the range of pH 6 to 10 with an optimum at pH 8.5, and in the range of 6°C to 50°C with an optimum at 35°C. The aminotransferase worked best at low salt concentration. FumI activity could be recovered after preincubation at pH 4.0 or higher, but not lower. The aminotransferase was denatured after preincubation at 60°C for 1 h, and the residual activity was also reduced after preincubation at lower temperatures. At optimum conditions, the kinetic parameters K (M) = 1.1 μM and k (cat) = 104/min were determined with 5 mM pyruvate as co-substrate. Based on the enzyme characteristics, a technological application of FumI, in combination with the fumonisin carboxylesterase FumD for hydrolysis of fumonisins, for deamination and detoxification of hydrolyzed fumonisins seems possible, if the enzyme properties are considered.

Immobilization of an L-aminoacylase-producing strain of Aspergillus oryzae into gelatin pellets and its application in the resolution of D,L-methionine.

PubMed

Yuan Yj, Ying-jin; Wang Sh, Shu-hao; Song Zx, Zheng-xiao; Gao Rc, Rui-chang

2002-04-01

The conditions for immobilization of an l-aminoacylase-producing strain of Aspergillus oryzae in gelatin and the enzymic characteristics of the immobilized pellets were studied. The optimal concentrations of gelatin, glutaraldehyde and ethyldiamine and time of immobilization were determined. Scanning electron micrographs reveal the cross-linked structure differences between the native and immobilized pellets. Optimum pH and temperature of the native and immobilized pellets were determined. Effects of ionic strength and substrate concentration on relative activity of the native and immobilized pellets were investigated in detail. The immobilized pellets were more stable over broader temperature and pH ranges. In addition, the immobilized pellets showed stable activity under operational and storage conditions. The immobilized pellets lost about 20% of their initial activity after five cycles of reuse. The results reported in this paper show the potential for using the immobilized A. oryzae pellets to resolve d,l-methionine.

Purification and Characterization of Glucose 6-Phosphate Dehydrogenase, 6-Phosphogluconate Dehydrogenase, and Glutathione Reductase from Rat Heart and Inhibition Effects of Furosemide, Digoxin, and Dopamine on the Enzymes Activities.

PubMed

Adem, Sevki; Ciftci, Mehmet

2016-06-01

The present study was aimed to investigate characterization and purification of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and glutathione reductase from rat heart and the inhibitory effect of three drugs. The purification of the enzymes was performed using 2',5'-ADP sepharose 4B affinity material. The subunit and the natural molecular weights were analyzed by SDS-PAGE and gel filtration. Biochemical characteristics such as the optimum temperature, pH, stable pH, and salt concentration were examined for each enzyme. Types of product inhibition and Ki values with Km and Vmax values of the substrates and coenzymes were determined. According to the obtained Ki and IC50 values, furosemide, digoxin, and dopamine showed inhibitory effect on the enzyme activities at low millimolar concentrations in vitro conditions. Dopamine inhibited the activity of these enzymes as competitive, whereas furosemide and digoxin inhibited the activity of the enzyme as noncompetitive. © 2016 Wiley Periodicals, Inc.

Biomimetic synthesis of silver nanoparticles and evaluation of their catalytic activity towards degradation of methyl orange

NASA Astrophysics Data System (ADS)

Manjari Mishra, Pravat; Bihari Pani, Khirod

2017-11-01

This paper described the significant effect of process variables like reductant concentrations, substrate concentration, reaction pH and reaction temperature on the size, morphology and yield of the silver nanoparticles (AgNPs) synthesized using aqueous leaf extract of a medicinal plant Momordica charantia (Bitter guard). By means of UV-vis spectroscopy, XRD analysis, TEM analysis and Fluorescence analysis, it is observed that the reaction solution containing 10-3 M of AgNO3 of pH 5.3  +  10 ml of aqueous leaf extract at normal room temperature, was optimum for synthesis of stable, polydisperse, predominantly spherical AgNPs with average size of 12.15 nm. FT-IR and TEM studies confirmed the stability of AgNPs was due to the capping of phytoconstituents present in the leaf extract. The aqueous solution of leaf extract containing AgNPs showed remarkable catalytic activity towards degradation of methyl orange (MO) in aqueous medium.

Lactulose production by a thermostable glycoside hydrolase from the hyperthermophilic archaeon Caldivirga maquilingensis IC-167.

PubMed

Letsididi, Rebaone; Hassanin, Hinawi Am; Koko, Marwa Yf; Zhang, Tao; Jiang, Bo; Mu, Wanmeng

2018-02-01

Lactulose has various uses in the food and pharmaceutical fields. Thermostable enzymes have many advantages for industrial exploitation, including high substrate solubilities as well as reduced risk of process contamination. Enzymatic synthesis of lactulose employing a transgalactosylation reaction by a recombinant thermostable glycoside hydrolase (GH1) from the hyperthermophilic archaeon Caldivirga maquilingensis IC-167 was investigated. The optimal pH for lactulose production was found to be 4.5, while the optimal temperature was 85 °C, before it dropped moderately to 83% at 90 °C. However, the relative activity for lactulose synthesis dropped sharply to 35% at 95 °C. At optimal reaction conditions of 70% (w/w) initial sugar substrates with molar ratio of lactose to fructose of 1:4, 15 U mL -1 enzyme concentration and 85 °C, the time course reaction produced a maximum lactulose concentration of 108 g L -1 at 4 h, corresponding to a lactulose yield of 14% and 27 g L -1  h -1 productivity with 84% lactose conversion. The transgalactosylation reaction for lactulose synthesis was greatly influenced by the ratio of galactose donor to acceptor. This novel GH1 may be useful for process applications owing to its high activity in very concentrated substrate reaction media and promising thermostability. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Study on the preparation process of cross-linked porous cassava starch

NASA Astrophysics Data System (ADS)

Yin, Xiulian; You, Qinghong; Wan, Miaomiao; Zhang, Xuejuan; Dai, Chunhua

2017-04-01

Using cassava starch as raw material, preparation process of porous cross-linked cassava starch was studied. Using TSTP as cross-linking agents, Orthogonal design was applied for the optimization of cross-linked porous starch preparation process. The results showed that the opitmal conditions of cross-linked porous cassava starch were as follows: reaction temperature 45°C, reaction time 20 h, 1% of the amount of the enzyme, the enzyme ratio of 1:5, pH 5.50, substrate concentration of 40%.

Relationships between transit time in man and in vitro fermentation of dietary fiber by fecal bacteria.

PubMed

Oufir, L E; Barry, J L; Flourié, B; Cherbut, C; Cloarec, D; Bornet, F; Galmiche, J P

2000-08-01

To assess the effects of drug-induced changes in mean transit time (MTT) on the activity of human fecal flora in vitro. The activity of fecal flora was estimated by the ability of a fecal inoculum to ferment a substrate (beet fiber) in vitro in a batch system for 24 h. The inoculum was collected from 8 healthy volunteers studied during three 3-week randomized periods, who received a controlled diet alone (control period) or the same diet with either cisapride or loperamide. Cisapride and loperamide were adjusted in order to halve and double MTT measured during the control period. At the end of each period, the percentage disappearance of the initial added substrate and the concentration and the profile of short-chain fatty acids (SCFAs), were determined. In the control period, the pH of the inoculum and SCFA concentration were inversely related to MTT (P=0.0001). Individual SCFA production was also significantly related to MTT (P<0.01). Cisapride-reduced transit time was associated with a significant rise in the concentrations of total SCFAs (P<0.05), propionic and butyric acids (P<0.05) and the percentage substrate disappearance (P<0.05). Inverse relations were observed during the loperamide period. Moreover, MTT was inversely related to the percentage substrate disappearance (P<0.001), SCFA production (P<0.001) and butyrate production (P<0.0005). Changes in MTT alter bacterial activity and modify the bacterial pathways affecting the proportion of individual SCFAs. European Journal of Clinical Nutrition (2000) 54, 603-609

Fermentative hydrogen production from liquid swine manure with glucose supplement using an anaerobic sequencing batch reactor

NASA Astrophysics Data System (ADS)

Wu, Xiao

2009-12-01

The idea of coupling renewable energy production and agricultural waste management inspired this thesis. The production of an important future fuel---hydrogen gas---from high strength waste stream-liquid swine manure---using anaerobic treatment processes makes the most sustainable sense for both wastewater utilization and energy generation. The objectives of this thesis were to develop a fermentation process for converting liquid swine manure to hydrogen and to maximize hydrogen productivity. Anaerobic sequencing batch reactor (ASBR) systems were constructed to carry out this fermentation process, and seed sludge obtained from a dairy manure anaerobic digester and pretreated by nutrient acclimation, heat and pH treatment was used as inoculum. High system stability was indicated by a short startup period of 12 days followed by stable hydrogen production, and successful sludge granulation occurred within 23 days of startup at a hydraulic retention time (HRT) of 24 hours. Operation at a progressively decreasing HRT from 24 to 8h gave rise to an increasing biogas production rate from 15.2-34.4L/d, while good linear relationships were observed between both total biogas and hydrogen production rates correlated to HRT, with R2 values of 0.993 and 0.997, respectively. The maximum hydrogen yield of 1.63 mol-H 2/mol-hexose-feed occurred at HRT of 16h, while the HRT of 12h was highly suggested to achieve both high production rate and efficient yield. Hexose utilization efficiencies over 98%, considerable hydrogen production rate up to 14.3 L/d and hydrogen percentage of off-gas up to 43% (i.e., a CO 2/H2 ratio of 1.2) with the absence of CH4 production throughout the whole course of experiment at a pH of 5.0 strongly validated the feasibility of the fermentative H2 production from liquid swine manure using an ASBR system. Ethanol as well as acetic, butyric and valeric acids were produced in the system accompanying the hydrogen production, with acetic acid being the dominant one, which contributed to 56-58% of the total soluble metabolite production, indicative of an acetic acid fermentation system, and acetate-to-butyrate ratio was found to be closely related to hydrogen yield. pH level influenced every aspect of the ASBR performance for hydrogen production. ASBR operation at five pHs ranging from 4.4 to 5.6 (4.4, 4.7, 5.0, 5.3, 5.6) showed distinct dynamic profiles of both biogas production and the changes of H2 and CH4 percentage in the biogas during a running period of 22 days. The H2 content in biogas, H 2 production rate and H2 yield were all pH-dependent, in the range of 5.1-36.9 %, 0.71-8.97 L/d and 0.12-1.50 mol-H2/mol-glucose, respectively, and maximum values for all three responses were simultaneously achieved at pH 5.0. Methanogens appeared to be significantly activated at pH of 5.3 or higher since significant CH4 evolution and concurrent reduction in H2 production was observed at pH 5.3 and 5.6. Acetate, propionate, butyrate, valerate, and ethanol were main aqueous products in all pH tests and their distribution was influenced by pH. Analysis of kinetic models developed from modified Gompertz equations for batch experiments showed that pH had a profound effect on all kinetic parameters for hydrogen production including hydrogen potential, maximum hydrogen production rate and the length of the lag phase, as well as the maximum substrate utilization rate. The low pH of 4.4 gave the highest hydrogen production potential but with the lowest hydrogen production rate. A contrast experiment was conducted with an initial pH of 5.3 but not controlled, came up with a rapid pH decline, leading to a low hexose degradation efficiency of 33.2% and a significantly suppressed H2 production, indicating the importance of pH control and the effect of pH on H2 production and substrate consumption. pH 5.0 was verified as the optimal for the proposed fermentation system by kinetic models. An extremely linear relationship (R2= 0.993) between the maximum H2 production rate and the maximum hexose degradation rate suggested that the pH inhibition on H2 production was a result of the suppression on the bacterial activity for substrate utilization due to an unfavorable pH level. System optimization was realized through experiments conducted according to a response surface methodology, with a central composite design and empirical quadratic response equations obtained for three responses including the hydrogen content in the biogas, hydrogen evolution rate and hydrogen yield, against three independent variables, pH (4.4-5.6), HRT (8-24h) and substrate glucose concentrations (Cg, 0-20 g/L). Contour plots revealed that all three responses were significantly impacted by the variable and squared pH. Furthermore, pH and Cg had a significant interaction effect on H2 production rate, while HRT and glucose concentration were interdependent, or they had a mildly significant interaction effect on H2 production rate. The hydrogen content decreased when pH was greater than 5.0 or less than 4.6 and a largest value of 42.7% could be obtained at pH 4.8, HRT 8 h, and Cg of 18.7 g/L. The highest hydrogen production rate of 26.1 L/d happened under a pH of 4.6, HRT of 8h, and Cg of 20 g/L; Lower HRT and higher Cg was found to benefit the H2 production rate because they provide elevated organic loading and food to microorganism ratio for the system. HRT shorter than 17h resulted in declined hydrogen yield, while the glucose concentration up to 20 g/L did not cause suppression on hydrogen yield. The revised optimal condition of pH 4.8, HRT 11h, and Cg of 20 g/L, which could achieve 85% of the maximum values of all three hydrogen productivity responses, was determined by surface response methodology. Highly reproducible results from confirming experiments at the optimal condition indicated that the results modeled in this study possessed a high reliability, while the results of H2 content, H2 production rate and yield were obtained as 40.3%, 23.16 L/d, and 1.36mol H2/mol hexose, respectively. Results obtained in this study indicated that ASBR system using swine manure based substrate had significant potential of fermentative hydrogen production. Key words: biohydrogen production, hydrogen fermentation, liquid swine manure, anaerobic sequencing batch reactor (ASBR), hydrogen content, hydrogen production rate, hydrogen yield

Exogenous lactobacilli mitigate microbial changes associated with grain fermentation (corn, oats, and wheat) by equine fecal microflora ex vivo.

PubMed

Harlow, Brittany E; Lawrence, Laurie M; Harris, Patricia A; Aiken, Glen E; Flythe, Michael D

2017-01-01

Cereal grains are often included in equine diets. When starch intake exceeds foregut digestion starch will reach the hindgut, impacting microbial ecology. Probiotics (e.g., lactobacilli) are reported to mitigate GI dysbioses in other species. This study was conducted to determine the effect of exogenous lactobacilli on pH and the growth of amylolytic and lactate-utilizing bacteria. Feces were collected from 3 mature geldings fed grass hay with access to pasture. Fecal microbes were harvested by differential centrifugation, washed, and re-suspended in anaerobic media containing ground corn, wheat, or oats at 1.6% (w/v) starch and one of five treatments: Control (substrate only), L. acidophilus, L. buchneri, L. reuteri, or an equal mixture of all three (107 cells/mL, final concentration). After 24 h of incubation (37°C, 160 rpm), samples were collected for pH and enumerations of total amylolytics, Group D Gram-positive cocci (GPC; Enterococci, Streptococci), lactobacilli, and lactate-utilizing bacteria. Enumeration data were log transformed prior to ANOVA (SAS, v. 9.3). Lactobacilli inhibited pH decline in corn and wheat fermentations (P < 0.0001). Specifically, addition of either L. reuteri or L. acidophilus was most effective at mitigating pH decline with both corn and wheat fermentation, in which the greatest acidification occurred (P < 0.05). Exogenous lactobacilli decreased amylolytics, while increasing lactate-utilizers in corn and wheat fermentations (P < 0.0001). In oat fermentations, L. acidophilus and L. reuteri inhibited pH decline and increased lactate-utilizers while decreasing amylolytics (P < 0.0001). For all substrates, L. reuteri additions (regardless of viability) had the lowest number of GPC and the highest number of lactobacilli and lactate-utilizers (P < 0.05). There were no additive effects when lactobacilli were mixed. Exogenous lactobacilli decreased the initial (first 8 h) rate of starch catalysis when wheat was the substrate, but did not decrease total (24 h) starch utilization in any case. These results indicate that exogenous lactobacilli can impact the microbial community and pH of cereal grain fermentations by equine fecal microflora ex vivo. Additionally, dead (autoclaved) exogenous lactobacilli had similar effects as live lactobacilli on fermentation. This latter result indicates that the mechanism by which lactobacilli impact other amylolytic bacteria is not simple resource competition.

Exogenous lactobacilli mitigate microbial changes associated with grain fermentation (corn, oats, and wheat) by equine fecal microflora ex vivo

PubMed Central

Harlow, Brittany E.; Lawrence, Laurie M.; Harris, Patricia A.; Aiken, Glen E.

2017-01-01

Cereal grains are often included in equine diets. When starch intake exceeds foregut digestion starch will reach the hindgut, impacting microbial ecology. Probiotics (e.g., lactobacilli) are reported to mitigate GI dysbioses in other species. This study was conducted to determine the effect of exogenous lactobacilli on pH and the growth of amylolytic and lactate-utilizing bacteria. Feces were collected from 3 mature geldings fed grass hay with access to pasture. Fecal microbes were harvested by differential centrifugation, washed, and re-suspended in anaerobic media containing ground corn, wheat, or oats at 1.6% (w/v) starch and one of five treatments: Control (substrate only), L. acidophilus, L. buchneri, L. reuteri, or an equal mixture of all three (107 cells/mL, final concentration). After 24 h of incubation (37°C, 160 rpm), samples were collected for pH and enumerations of total amylolytics, Group D Gram-positive cocci (GPC; Enterococci, Streptococci), lactobacilli, and lactate-utilizing bacteria. Enumeration data were log transformed prior to ANOVA (SAS, v. 9.3). Lactobacilli inhibited pH decline in corn and wheat fermentations (P < 0.0001). Specifically, addition of either L. reuteri or L. acidophilus was most effective at mitigating pH decline with both corn and wheat fermentation, in which the greatest acidification occurred (P < 0.05). Exogenous lactobacilli decreased amylolytics, while increasing lactate-utilizers in corn and wheat fermentations (P < 0.0001). In oat fermentations, L. acidophilus and L. reuteri inhibited pH decline and increased lactate-utilizers while decreasing amylolytics (P < 0.0001). For all substrates, L. reuteri additions (regardless of viability) had the lowest number of GPC and the highest number of lactobacilli and lactate-utilizers (P < 0.05). There were no additive effects when lactobacilli were mixed. Exogenous lactobacilli decreased the initial (first 8 h) rate of starch catalysis when wheat was the substrate, but did not decrease total (24 h) starch utilization in any case. These results indicate that exogenous lactobacilli can impact the microbial community and pH of cereal grain fermentations by equine fecal microflora ex vivo. Additionally, dead (autoclaved) exogenous lactobacilli had similar effects as live lactobacilli on fermentation. This latter result indicates that the mechanism by which lactobacilli impact other amylolytic bacteria is not simple resource competition. PMID:28358885

Evaluation of the Accumulation of Trace Metals (as, U, CR, CU, PB, Zn) on Iron-Manganese Coatings on in Situ Stream Pebbles and Emplaced Substrates

NASA Astrophysics Data System (ADS)

Turpin, M. M.; Blake, J.; Crossey, L. J.; Ali, A.; Hansson, L.

2015-12-01

Exposure to trace metals (As, U, Cr, Cu, Pb, Zn) has potential negative health effects on human populations and wildlife. Geothermal waters often have elevated concentrations of trace elements and understanding the geochemical cycling of these elements can be challenging. Previous studies have utilized in situ stream pebbles and glass or ceramic substrates with iron-manganese oxide coatings to understand contamination and or chemical cycling. This project's main focus is to develop an ideal tracing method using adsorption onto substrate surfaces and to define key parameters that are necessary for the phenomenon of adsorption between trace metals and these surface coatings to occur. Sampling locations include the Jemez River and Rio San Antonio in the Jemez mountains, northern New Mexico. Both streams have significant geothermal inputs. Pebbles and cobbles were gathered from the active stream channel and 6mm glass beads and 2 X1 in. ceramic plates were placed in streams for three weeks to allow for coating accumulation. Factors such as leachate type, water pH, substrate type, coating accumulation period and leach time were all considered in this experiment. It was found that of the three leachates (aqua regia, 10% aqua regia and hydroxylamine), hydroxylamine was the most effective at leaching coatings without dissolving substrates. Samples leached with aqua regia and 10% aqua regia were found to lose weight and mass over the following 5, 7, and 10 day measurements. Glass beads were determined to be more effective than in stream pebbles as an accumulation substrate: coatings were more easily controlled and monitored. Samples leached with hydroxylamine for 5 hours and 72 hours showed little difference in their leachate concentrations, suggesting that leach time has little impact on the concentration of leachate samples. This research aims to find the best method for trace metal accumulation in streams to aid in understanding geochemical cycling.

Kinetic study of hydroxytyrosol oxidation and its related compounds by Red Globe grape polyphenol oxidase.

PubMed

García-García, María Inmaculada; Hernández-García, Samanta; Sánchez-Ferrer, Álvaro; García-Carmona, Francisco

2013-06-26

Red Globe grape polyphenol oxidase, partially purified using phase partitioning with Triton-X114, was used to study the oxidation of hydroxytytosol (HT) and its related compounds tyrosol (TS), tyrosol acetate (TSA), and hydroxytyrosol acetate (HTA). The enzyme showed activity toward both monophenols (monophenolase activity) and o-diphenols (diphenolase activity) with a pH optimum (pH 6.5) that was independent of the phenol used. However, the optimal temperature for diphenolase activity was substrate-dependent, with a broad optimum of 25-65 °C for HT, compared with the maximum obtained for HTA (40 °C). Monophenolase activity showed the typical lag period, which was modulated by pH, substrate and enzyme concentrations, and the presence of catalytic amounts of o-diphenols. When the catalytic power (Vmax/K(M)) was determined for both activities, higher values were observed for o-diphenols than for monophenols: 9-fold higher for the HT/TS pair and 4-fold higher for HTA/TSA pair. Surprisingly, this ratio was equally higher for TSA (2.2-fold) compared with that of TS, whereas no such effect was observed for o-diphenols. This higher efficiency of TSA could be related to its greater hydrophobicity. Acetyl modification of these phenols not only changes the kinetic parameters of the enzyme but also affects their antioxidant activity (ORAC-FL assays), which is lower in HTA than in HT.

Micro-patterning and characterization of PHEMA-co-PAM-based optical chemical sensors for lab-on-a-chip applications

PubMed Central

Zhu, Haixin; Zhou, Xianfeng; Su, Fengyu; Tian, Yanqing; Ashili, Shashanka; Holl, Mark R.; Meldrum, Deirdre R.

2012-01-01

We report a novel method for wafer level, high throughput optical chemical sensor patterning, with precise control of the sensor volume and capability of producing arbitrary microscale patterns. Monomeric oxygen (O2) and pH optical probes were polymerized with 2-hydroxyethyl methacrylate (HEMA) and acrylamide (AM) to form spin-coatable and further crosslinkable polymers. A micro-patterning method based on micro-fabrication techniques (photolithography, wet chemical process and reactive ion etch) was developed to miniaturize the sensor film onto glass substrates in arbitrary sizes and shapes. The sensitivity of fabricated micro-patterns was characterized under various oxygen concentrations and pH values. The process for spatially integration of two sensors (Oxygen and pH) on the same substrate surface was also developed, and preliminary fabrication and characterization results were presented. To the best of our knowledge, it is the first time that poly (2-hydroxylethyl methacrylate)-co-poly (acrylamide) (PHEMA-co-PAM)-based sensors had been patterned and integrated at the wafer level with micron scale precision control using microfabrication techniques. The developed methods can provide a feasible way to miniaturize and integrate the optical chemical sensor system and can be applied to any lab-on-a-chip system, especially the biological micro-systems requiring optical sensing of single or multiple analytes. PMID:23175599

COMPARATIVE STUDIES OF THREE METHODS FOR MEASURING PEPSIN ACTIVITY

PubMed Central

Loken, Merle K.; Terrill, Kathleen D.; Marvin, James F.; Mosser, Donn G.

1958-01-01

Comparison has been made of a simple method originated by Absolon and modified in our laboratories for assay of proteolytic activity using RISA (radioactive iodinated serum albumin—Abbott Laboratories), with the commonly used photometric methods of Anson and Kunitz. In this method, pepsin was incubated with an albumin substrate containing RISA, followed by precipitation of the undigested substrate with trichloroacetic acid and measurement of radioactive digestion products in the supernatant fluid. The I131—albumin bond was shown in the present studies to be altered only by the proteolytic activity, and not by the incubation procedures at various values of pH. Any free iodine present originally in the RISA was removed by a single passage through a resin column (amberlite IRA-400-C1). Pepsin was shown to be most stable in solution at a pH of 5.5. Activity of pepsin was shown to be maximal when it was incubated with albumin at a pH of 2.5. Pepsin activity was shown to be altered in the presence of various electrolytes. Pepsin activity measured by the RISA and Anson methods as a function of concentration or of time of incubation indicated that these two methods are in good agreement and are equally sensitive. Consistently smaller standard errors were obtained by the RISA method of pepsin assay than were obtained with either of the other methods. PMID:13587910

Phosphatase activities as biosignatures of extant life

NASA Astrophysics Data System (ADS)

Kobayashi, K.; Itoh, Y.; Edazawa, Y.; Moroi, A.; Takano, Y.

It has been recognized that terrestrial biosphere expands to such extreme environments as deep subsurface lithosphere high temperature hot springs and stratosphere Possible extraterrestrial biospheres in Mars Europa and Titan are being discussed Many biosignatures or biomarkers have been proposed to detect microbial activities in such extreme environments Phosphate esters are essential for the terrestrial life since they are constituents of nucleic acids and cell mebranes Thus all the terrestrial organisms have phosphatases that are enzymes catalyzing hydrolysis of phosphate esters We analyzed phosphatase activities in the samples obtained in extreme environments such as submarine hydrothermal systems and discussed whether they can be used as biosignatures for extant life Core samples and chimney samples were collected at the Suiyo Seamount Izu-Bonin Arc the Pacific Ocean in 2001 and 2002 and in South Mariana hydrothermal systems the Pacific Oceanas in 2003 both in a part of the Archaean Park Project Phosphatase activity in solid rock samples was measured spectrometrically by using 25 mM p-nitrophenyl phosphate pH 8 0 or pH 6 5 as a substrate as follows Pulverized samples were incuvated with substrate solution for an hour and then production rate of p-nitrophenol was calculated with absorbance at 410 nm Phosphatase activity in extracts was measured fluorometrically by using 4-methylumberyferryl phosphate as a substrate Concentration of amino acids and their enantiomeric ratio were determined by HPLC after HF digestion of the

Horseradish peroxidase-mediated decolourization of Orange II: modelling hydrogen peroxide utilization efficiency at different pH values.

PubMed

Morales Urrea, Diego Alberto; Haure, Patricia Mónica; García Einschlag, Fernando Sebastián; Contreras, Edgardo Martín

2018-05-09

Enzymatic decolourization of azo-dyes could be a cost-competitive alternative compared to physicochemical or microbiological methods. Stoichiometric and kinetic features of peroxidase-mediated decolourization of azo-dyes by hydrogen peroxide (P) are central for designing purposes. In this work, a modified version of the Dunford mechanism of peroxidases was developed. The proposed model takes into account the inhibition of peroxidases by high concentrations of P, the substrate-dependant catalatic activity of peroxidases (e.g. the decomposition of P to water and oxygen), the generation of oxidation products (OP) and the effect of pH on the decolourization kinetics of the azo-dye Orange II (OII). To obtain the parameters of the proposed model, two series of experiments were performed. In the first set, the effects of initial P concentration (0.01-0.12 mM) and pH (5-10) on the decolourization degree were studied at a constant initial OII concentration (0.045 mM). Obtained results showed that at pH 9-10 and low initial P concentrations, the consumption of P was mainly to oxidize OII. From the proposed model, an expression for the decolourization degree was obtained. In the second set of experiments, the effect of the initial concentrations of OII (0.023-0.090 mM), P (0.02-4.7 mM), HRP (34-136 mg/L) and pH (5-10) on the initial specific decolourization rate (q 0 ) was studied. As a general rule, a noticeable increase in q 0 was observed for pHs higher than 7. For a given pH, q 0 increased as a function of the initial OII concentration. Besides, there was an inhibitory effect of high P concentrations on q 0 . To asses the possibility of reusing the enzyme, repeated additions of OII and P were performed. Results showed that the enzyme remained active after six reuse cycles. A satisfactory accordance between the change of the absorbance during these experiments and absorbances calculated using the proposed model was obtained. Considering that this set of data was not used during the fitting procedure of the model, the agreement between predicted and experimental absorbances provides a powerful validation of the model developed in the present work.

A pH sensor based on electric properties of nanotubes on a glass substrate

PubMed Central

Nakamura, Motonori; Ishii, Atsushi; Subagyo, Agus; Hosoi, Hirotaka; Sueoka, Kazuhisa; Mukasa, Koichi

2007-01-01

We fabricated a pH-sensitive device on a glass substrate based on properties of carbon nanotubes. Nanotubes were immobilized specifically on chemically modified areas on a substrate followed by deposition of metallic source and drain electrodes on the area. Some nanotubes connected the source and drain electrodes. A top gate electrode was fabricated on an insulating layer of silane coupling agent on the nanotube. The device showed properties of ann-type field effect transistor when a potential was applied to the nanotube from the top gate electrode. Before fabrication of the insulating layer, the device showed that thep-type field effect transistor and the current through the source and drain electrodes depend on the buffer pH. The current increases with decreasing pH of the CNT solution. This device, which can detect pH, is applicable for use as a biosensor through modification of the CNT surface. PMID:21806848

Optimisation of the expression of a Trametes versicolor laccase gene in Pichia pastoris.

PubMed

O'Callaghan, J; O'Brien, M M; McClean, K; Dobson, A D W

2002-08-01

A cDNA encoding a laccase enzyme was isolated from a Trametes versicolor cDNA library. The gene was subcloned into the Pichia pastoris expression vector pPIC3.5 and transformed into the P. pastoris strains KM71 and GS115. Laccase-secreting transformants were selected by their ability to oxidise the substrate ABTS. No difference in laccase activity was observed between culture supernatants from GS115 (proteolytic) and KM71 (nonproteolytic) strains. The presence of at least 200 microM copper was necessary for optimal laccase activity in the culture supernatants. During growth of P. pastoris on minimal medium the pH of the medium was reduced to <3.0. If alanine was added to the medium the pH reduction was not as pronounced and at alanine concentrations >0.6% w/v the pH was kept constant for >7 days. Cultures in which the pH was maintained by alanine metabolism produced higher levels of laccase activity than those grown in the absence of alanine. This study describes the development of a medium that allows convenient pH control of P. pastoris without the need for continuous neutralisation.

Surface modification of poly(L-lactic acid) to improve its cytocompatibility via assembly of polyelectrolytes and gelatin.

PubMed

Lin, Yuan; Wang, Luling; Zhang, Peibiao; Wang, Xin; Chen, Xuesi; Jing, Xiabin; Su, Zhaohui

2006-03-01

Poly(L-lactide) (PLLA) surface was modified via aminolysis by poly(allylamine hydrochloride) (PAH) at high pH and subsequent electrostatic self-assembly of poly(sodium styrenesulfonate) (PSS) and PAH, and the process was monitored by X-ray photoelectron spectroscopy (XPS) and contact angle measurement. These modified PLLAs were then used as charged substrates for further incorporation of gelatin to improve their cytocompatibility. The amphoteric nature of the gelatin was exploited and the gelatin was adsorbed to the negatively charged PLLA/PSS and positively charged PLLA/PAH at pH=3.4 and 7.4, respectively. XPS and water contact angle data indicated that the gelatin adsorption at pH=3.4 resulted in much higher surface coverage by gelatin than at pH=7.4. All the modified PLLA surfaces became more hydrophilic than the virgin PLLA. Chondrocyte culture was used to test the cell attachment, cell morphology and cell viability on the modified PLLA substrates. The results showed that the PAH and PSS modified PLLA exhibited better cytocompatibility than virgin PLLA, and the incorporation of the gelatin on these modified PLLA substrates further improved their cytocompatibility, with the PLLA/PSS substrate treated with the gelatin at pH=3.4 being the best, exceeding the chondrocyte compatibility of the tissue culture polystyrene.

Soil acidification as a confounding factor on metal phytotoxicity in soils spiked with copper-rich mine wastes.

PubMed

Ginocchio, Rosanna; De la Fuente, Luz María; Sánchez, Pablo; Bustamante, Elena; Silva, Yasna; Urrestarazu, Paola; Rodríguez, Patricio H

2009-10-01

Pollution of soil with mine wastes results in both Cu enrichment and soil acidification. This confounding effect may be very important in terms of phytotoxicity, because pH is a key parameter influencing Cu solubility in soil solution. Laboratory toxicity tests were used to assess the effect of acidification by acidic mine wastes on Cu solubility and on root elongation of barley (Hordeum vulgare L.). Three contrasting substrates (two soils and a commercial sand) and two acidic, Cu-rich mine wastes (oxidized tailings [OxT] and smelter dust [SmD]) were selected as experimental materials. Substrates were spiked with a fixed amount of either SmD or OxT, and the pH of experimental mixtures was then modified in the range of 4.0 to 6.0 and 7.0 using PIPES (piperazine-1,4-bis(2-ethanesulfonic acid)), MES (2-(N-morpholino)ethanesulfonic acid), and MOPS (3-(N-Morpholino)-propanesulfonic acid) buffers. Chemical (pore-water Cu and pH) and toxicological (root length of barley plants) parameters were determined for experimental mixtures. Addition of SmD and OxT to substrates resulted in acidification (0.11-1.16 pH units) and high levels of soluble Cu and Zn. Neutralization of experimental mixtures with MES (pH 6.0) and MOPS (pH 7.0) buffers resulted in a marked decrease in soluble Cu and Zn, but the intensity of the effect was substrate-dependent. Adjustment of soil pH above the range normally considered to be toxic to plants (pH in water extract, > 5.5) significantly reduced metal toxicity in barley, but phytotoxicity was not completely eliminated. The present results stress the importance of considering confounding effects on derivation of toxicity thresholds to plants when using laboratory phytotoxicity tests.

Synergetic effect of pH and biochemical components on bacterial diversity during mesophilic anaerobic fermentation of biomass-origin waste.

PubMed

Lü, F; Shao, L M; Bru, V; Godon, J J; He, P J

2009-02-01

To investigate the synergetic effect of pH and biochemical components on bacterial community structure during mesophilic anaerobic degradation of solid wastes with different origins, and under acidic or neutral conditions. The bacterial community in 16 samples of solid wastes with different biochemical compositions and origins was evaluated during mesophilic anaerobic degradation at acidic and neutral pH. Denaturing gradient gel electrophoresis (DGGE) and single-strand conformation polymorphism (SSCP) were used to compare the communities. Multivariate analysis of the DGGE and SSCP results revealed that most of the dominant microbes were dependent on the content of easily degradable carbohydrates in the samples. Furthermore, the dominant microbes were divided into two types, those that preferred an acid environment and those that preferred a neutral environment. A shift in pH was found to change their preference for medium substrates. Although most of the substrates with similar origin and biochemical composition had similar microbial diversity during fermentation, some microbes were found only in substrates with specific origins. For example, two microbes were only found in substrate that contained lignocellulose and animal protein without starch. These microbes were related to micro-organisms that are found in swine manure, as well as in other intestinal or oral niches. In addition, the distribution of fermentation products was less sensitive to the changes in pH and biochemical components than the microbial community. Bacterial diversity during anaerobic degradation of organic wastes was affected by both pH and biochemical components; however, pH exerted a greater effect. The results of this study reveal that control of pH may be an effective method to produce a stable bacterial community and relatively similar product distribution during anaerobic digestion of waste, regardless of variation in the waste feedstocks.

Transformation of halogen-, alkyl-, and alkoxy-substituted anilines by a lactase of Trametes versicolor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoff, T.; Liu, S.Y.; Bollag, J.M.

1985-05-01

The lactase of the fungus Trametes versicolor was able to polymerize various halogen-, alkyl-, and alkoxy-substituted anilines, showing substrate specificity similar to that of horseradish peroxidase, whereas the lactase of Rhizoctonia praticola was active only with p-methoxyaniline. The substrate specificities of the enzymes were determined by using gas chromatography to measure the decrease in substrate concentration during incubation. With p-chloroaniline as the substrate, the peroxidase and the Trametes lactase showed maximum activity near pH 4.2. The transformation of this substrate gave rise to a number of oligomers, ranging from dimers to pentamers, as determined by mass spectrometry. The product profilesmore » obtained by high-pressure liquid chromatography were similar for the two enzymes. A chemical reaction was observed between p-chloroaniline and an enzymatically formed dimer, resulting in the formation of a trimer. All three enzymes oxidized p-methoxyaniline to 2-amino-5-p-anisidinobenzoquinone di-p-methoxyphenylimine, but only the T. versicolor lactase and the peroxidase caused the formation of a pentamer (2,5-di-p-anisidinobenzoquinone di-p-methoxyphenylimine). These results demonstrate that in addition to horseradish peroxidase, a T. versicolor lactase can also polymerize aniline derivatives.« less

Synthesis of iron composites on nano-pore substrates: identification and its application to removal of cyanide.

PubMed

Do, Si-Hyun; Jo, Young-Hoon; Park, Ho-Dong; Kong, Sung-Ho

2012-11-01

Two types of nano-pore substrates, waste-reclaimed (WR) and soil mineral (SM) with the relatively low density, were modified by the reaction with irons (i.e. Fe(II):Fe(III)=1:2) and the applicability of the modified substrates (i.e. Fe-WR and Fe-SM) on cyanide removal was investigated. Modification (i.e. Fe immobilization on substrate) decreased the BET surface area and PZC of the original substrates while it increased the pore diameter and the cation exchange capacity (CEC) of them. XRD analysis identified that maghemite (γ-Fe(2)O(3)) and iron silicate composite ((Mg, Fe)SiO(3)) existed on Fe-WR, while clinoferrosilite (FeSiO(3)) was identified on Fe-SM. Cyanide adsorption showed that WR adsorbed cyanide more favorably than SM. The adsorption ability of both original substrates was enhanced by the modification, which increased the negative charges of the surfaces. Without the pH adjustment, cyanide was removed as much as 97% by the only application of Fe-WR, but the undesirable transfer to hydrogen cyanide was possible because the pH was dropped to around 7.5. With a constant pH of 12, only 54% of cyanide was adsorbed on Fe-WR. On the other hand, the pH was kept as 12 without adjustment in Fe-WR/H(2)O(2) system and cyanide was effectively removed by not only adsorption but also the catalytic oxidation. The observed first-order rate constant (k(obs)) for cyanide removal were 0.49 (± 0.081) h(-1). Moreover, the more cyanate production with the modified substrates indicated the iron composites, especially maghemite, on substrates had the catalytic property to increase the reactivity of H(2)O(2). Copyright © 2012 Elsevier Ltd. All rights reserved.

Some limitation in the use of the I- method for measuring the peroxidase activity from bovine thyroid gland.

PubMed

Salano, F; Iborra, J L; Lozano, J A

1981-09-01

Studied for measuring the peroxidase activity from thyroid gland have usually been achieved on the basis of the H2O2 oxidation of I- to I3- catalyzed by peroxidase. The activity assay has been found to depend on several factors such as the relative order of reagent addition, protein content of the enzyme preparation, presence of detergent and the pH of the reaction medium. At below 7.0 pH, the contribution of the non-enzymic transformation of I- to total activity became quite significant, to the extent that at below 6.5 pH, the chemical reaction predominates over the enzymic one. At values above 7.0 pH, a very rapid decomposition of the product was observed. Guaiacol oxidation has been considered to be a more reliable method than the iodide one, especially when the substrate concentration and temperature vary, and when the activity of relatively rich in protein samples, as well as of some other substances that might interfere with the I3- formation, are going to be measured.

[Characteristics and operation of enhanced continuous bio-hydrogen production reactor using support carrier].

PubMed

Ren, Nan-qi; Tang, Jing; Gong, Man-li

2006-06-01

A kind of granular activated carbon, whose granular size is no more than 2mm and specific gravity is 1.54g/cm3, was used as the support carrier to allow retention of activated sludge within a continuous stirred-tank reactor (CSTR) using molasses wastewater as substrate for bio-hydrogen production. Continuous operation characteristics and operational controlling strategy of the enhanced continuous bio-hydrogen production system were investigated. It was indicated that, support carriers could expand the activity scope of hydrogen production bacteria, make the system fairly stable in response to organic load impact and low pH value (pH <3.8), and maintain high biomass concentration in the reactor at low HRT. The reactor with ethanol-type fermentation achieved an optimal hydrogen production rate of 0.37L/(g x d), while the pH value ranged from 3.8 to 4.4, and the hydrogen content was approximately 40% approximately 57% of biogas. It is effective to inhibit the methanogens by reducing the pH value of the bio-hydrogen production system, consequently accelerate the start-up of the reactor.

Turnover-Dependent Inactivation of the Nitrogenase MoFe-Protein at High pH

PubMed Central

2013-01-01

Proton uptake accompanies the reduction of all known substrates by nitrogenase. As a consequence, a higher pH should limit the availability of protons as a substrate essential for turnover, thereby increasing the proportion of more highly reduced forms of the enzyme for further study. The utility of the high-pH approach would appear to be problematic in view of the observation reported by Pham and Burgess [(1993) Biochemistry 32, 13725–13731] that the MoFe-protein undergoes irreversible protein denaturation above pH 8.65. In contrast, we found by both enzyme activity and crystallographic analyses that the MoFe-protein is stable when incubated at pH 9.5. We did observe, however, that at higher pHs and under turnover conditions, the MoFe-protein is slowly inactivated. While a normal, albeit low, level of substrate reduction occurs under these conditions, the MoFe-protein undergoes a complex transformation; initially, the enzyme is reversibly inhibited for substrate reduction at pH 9.5, yet in a second, slower process, the MoFe-protein becomes irreversibly inactivated as measured by substrate reduction activity at the optimal pH of 7.8. The final inactivated MoFe-protein has an increased hydrodynamic radius compared to that of the native MoFe-protein, yet it has a full complement of iron and molybdenum. Significantly, the modified MoFe-protein retains the ability to specifically interact with its nitrogenase partner, the Fe-protein, as judged by the support of ATP hydrolysis and by formation of a tight complex with the Fe-protein in the presence of ATP and aluminum fluoride. The turnover-dependent inactivation coupled to conformational change suggests a mechanism-based transformation that may provide a new probe of nitrogenase catalysis. PMID:24392967

Turnover-dependent inactivation of the nitrogenase MoFe-protein at high pH.

PubMed

Yang, Kun-Yun; Haynes, Chad A; Spatzal, Thomas; Rees, Douglas C; Howard, James B

2014-01-21

Proton uptake accompanies the reduction of all known substrates by nitrogenase. As a consequence, a higher pH should limit the availability of protons as a substrate essential for turnover, thereby increasing the proportion of more highly reduced forms of the enzyme for further study. The utility of the high-pH approach would appear to be problematic in view of the observation reported by Pham and Burgess [(1993) Biochemistry 32, 13725-13731] that the MoFe-protein undergoes irreversible protein denaturation above pH 8.65. In contrast, we found by both enzyme activity and crystallographic analyses that the MoFe-protein is stable when incubated at pH 9.5. We did observe, however, that at higher pHs and under turnover conditions, the MoFe-protein is slowly inactivated. While a normal, albeit low, level of substrate reduction occurs under these conditions, the MoFe-protein undergoes a complex transformation; initially, the enzyme is reversibly inhibited for substrate reduction at pH 9.5, yet in a second, slower process, the MoFe-protein becomes irreversibly inactivated as measured by substrate reduction activity at the optimal pH of 7.8. The final inactivated MoFe-protein has an increased hydrodynamic radius compared to that of the native MoFe-protein, yet it has a full complement of iron and molybdenum. Significantly, the modified MoFe-protein retains the ability to specifically interact with its nitrogenase partner, the Fe-protein, as judged by the support of ATP hydrolysis and by formation of a tight complex with the Fe-protein in the presence of ATP and aluminum fluoride. The turnover-dependent inactivation coupled to conformational change suggests a mechanism-based transformation that may provide a new probe of nitrogenase catalysis.

Limited Carbonate Dissolution by Boring Microflora at Two Volcanically Acidified Temperate Sites: Ischia (Italy, Mediterranean Sea) and Faial (Azores, NE Atlantic Ocean)

NASA Astrophysics Data System (ADS)

Tribollet, A.; Grange, J. S.; Parra, H.; Rodolfo-Metalpa, R.; Carreiro-Silva, M.

2018-01-01

In situ effects of ocean acidification on carbonate dissolution by microboring flora, also called biogenic dissolution, have only been studied once in tropical environments. Naturally acidified seawaters due to CO2 vents offer a perfect setting to study these effects in temperate systems. Three sites were selected at Ischia (Italy, Mediterranean Sea) with one experiencing ambient pH and the two others a mean pHT of 7.2 and 7.5. At Faial (Azores, NE Atlantic), one site with ambient pH and one acidified site with a mean pHT of 7.4 were selected. Experiments were carried out during 1.5 months and 6 months in Azores and Ischia, respectively, to determine the effects of OA on microboring communities in various carbonate substrates. Low pH influenced negatively boring microflora development by limiting their depth of penetration and abundance in substrates. Biogenic dissolution was thus reduced by a factor 3 to 7 depending on sites and substrate types. At sites with ambient pH in Faial, biogenic dissolution contributed up to 23% to the total weight loss, while it contributed less than 1% to the total weight loss of substrates at the acidified sites. Most of the dissolution at these sites was due to chemical dissolution (often Ω ≤ 1). Such conditions maintained microboring communities at a pioneer stage with a limited depth of penetration in substrates. Our results, together with previous findings that showed an increase of biogenic dissolution at pH > 7.7, suggest that there is a pH tipping point below which microborer development and thus carbonate biogenic dissolution is strongly limited.

pH-induced conformational changes in human ABO(H) blood group glycosyltransferases confirm the importance of electrostatic interactions in the formation of the semi-closed state.

PubMed

Johal, Asha R; Blackler, Ryan J; Alfaro, Javier A; Schuman, Brock; Borisova, Svetlana; Evans, Stephen V

2014-03-01

The homologous human ABO(H) A and B blood group glycosyltransferases GTA and GTB have two mobile polypeptide loops surrounding their active sites that serve to allow substrate access and product egress and to recognize and sequester substrates for catalysis. Previous studies have established that these enzymes can move from the "open" state to the "semi-closed" then "closed" states in response to addition of a substrate. The contribution of electrostatic interactions to these conformational changes has now been demonstrated by the determination at various pH of the structures of GTA, GTB and the chimeric enzyme ABBA. At near-neutral pH, GTA displays the closed state in which both mobile loops order around the active site, whereas ABBA and GTB display the open state. At low pH, the apparent protonation of the DXD motif in GTA leads to the expulsion of the donor analog to yield the open state, whereas at high pH, both ABBA and GTB form the semi-closed state in which the first mobile loop becomes an ordered α-helix. Step-wise deprotonation of GTB in increments of 0.5 between pH 6.5 and 10.0 shows that helix ordering is gradual, which indicates that the formation of the semi-closed state is dependent on electrostatic forces consistent with the binding of substrate. Spectropolarimetric studies of the corresponding stand-alone peptide in solution reveal no tendency toward helix formation from pH 7.0 to 10.0, which shows that pH-dependent stability is a product of the larger protein environment and underlines the importance of substrate in active site ordering.

Production of lipopeptides by Bacillus amyloliquefaciens XZ-173 in solid state fermentation using soybean flour and rice straw as the substrate.

PubMed

Zhu, Zhen; Zhang, Guoyi; Luo, Yi; Ran, Wei; Shen, Qirong

2012-05-01

This work was aimed to produce lipopeptides by Bacillus amyloliquefaciens XZ-173 in solid state fermentation using agro-industrial byproducts. A central composite design was used to get the highest lipopeptides production. Results revealed that the optimal conditions for maximum lipopeptides production were 1.79% starch and 1.91% yeast extract by employing 5.58 g soybean flour and 3.67 g rice straw as the solid substrate with initial pH 7.5, moisture content 55% and a 10% inoculum level at 30°C for 2 days. Under these conditions, the experimental yield of lipopeptides reached 50.01 mg/gds, which was very close to the predicted value (49.91 mg/gds). At high concentration, the lipopeptides extracted from fermented substrates showed strong antibiotic activity against Rhizoctonia solani and Ralstonia solanacearum and certain emulsification but good emulsion stability. This is the first report on lipopeptides production that uses rice straw as a major substrate. Copyright © 2012 Elsevier Ltd. All rights reserved.

Sulfhydryl modification of V449C in the glutamate transporter EAAT1 abolishes substrate transport but not the substrate-gated anion conductance

PubMed Central

Seal, Rebecca P.; Shigeri, Yasushi; Eliasof, Scott; Leighton, Barbara H.; Amara, Susan G.

2001-01-01

Excitatory amino acid transporters (EAATs) buffer and remove synaptically released l-glutamate and maintain its concentrations below neurotoxic levels. EAATs also mediate a thermodynamically uncoupled substrate-gated anion conductance that may modulate cell excitability. Here, we demonstrate that modification of a cysteine substituted within a C-terminal domain of EAAT1 abolishes transport in both the forward and reverse directions without affecting activation of the anion conductance. EC50s for l-glutamate and sodium are significantly lower after modification, consistent with kinetic models of the transport cycle that link anion channel gating to an early step in substrate translocation. Also, decreasing the pH from 7.5 to 6.5 decreases the EC50 for l-glutamate to activate the anion conductance, without affecting the EC50 for the entire transport cycle. These findings demonstrate for the first time a structural separation of transport and the uncoupled anion flux. Moreover, they shed light on some controversial aspects of the EAAT transport cycle, including the kinetics of proton binding and anion conductance activation. PMID:11752470

Improved volatile fatty acids anaerobic production from waste activated sludge by pH regulation: Alkaline or neutral pH?

PubMed

Ma, Huijun; Chen, Xingchun; Liu, He; Liu, Hongbo; Fu, Bo

2016-02-01

In this study, the anaerobic fermentation was carried out for volatile fatty acids (VFAs) production at different pH (between 7.0 and 10.0) conditions with untreated sludge and heat-alkaline pretreated waste activated sludge. In the fermentation with untreated sludge, the extent of hydrolysis of organic matters and extent of acidification at alkaline pH are 54.37% and 30.37%, respectively, resulting in the highest VFAs yield at 235.46mg COD/gVS of three pH conditions. In the fermentation with heat-alkaline pretreated sludge, the acidification rate and VFAs yield at neutral pH are 30.98% and 240.14mg COD/gVS, respectively, which are higher than that at other pH conditions. With the glucose or bovine serum albumin as substrate for VFAs production, the neutral pH showed a higher VFAs concentration than the alkaline pH condition. The results of terminal restriction fragment length polymorphism (T-RFLP) analysis indicated that the alkaline pH caused low microbial richness. Based on the results in this study, we demonstrated that the alkaline pH is favor of hydrolysis of organic matter in sludge while neutral pH improved the acidogenesis for the VFAs production from sludge. Our finding is obvious different to the previous research and helpful for the understanding of how heat-alkaline pretreatment and alkaline fermentation influence the VFAs production, and beneficial to the development of VFAs production process. Copyright © 2015 Elsevier Ltd. All rights reserved.

2,3-Dihydro-2,5-dihydroxy-4H-benzopyran-4-one: a nonphysiological substrate for fungal melanin biosynthetic enzymes.

PubMed

Thompson, J E; Basarab, G S; Pierce, J; Hodge, C N; Jordan, D B

1998-02-01

We have synthesized an alternate substrate for trihydroxynaphthalene reductase (3HNR) and scytalone dehydratase (SD), two enzymes in the fungal melanin biosynthetic pathway. The oxidation of 2,3-dihydro-2,5-dihydroxy-4H-benzopyran-4-one (DDBO) to 4,5-dihydroxy-2H-benzopyran-2-one (DBO) with concomitant reduction of NADP+ is catalyzed by 3HNR. DDBO is dehydrated by SD to 5-hydroxy-4H-1-benzopyran-4-one (HBO). These reactions can be monitored using continuous spectrophotometric assays. DDBO race-mizes rapidly, so chiral synthesis to mimic the natural substrate is not required. DDBO, DBO, and HBO are stable in aerated aqueous solution, in contrast to the rapidly autooxidizing trihydroxynaphthalene, a physiological substrate for 3HNR and product of SD. Unlike the natural substrates, DDBO, DBO, and HBO do not change protonation state between pH's 4 and 9. Oxidation of DDBO is effectively irreversible at pH 7, as DBO deprotonates with a pKa of 2.5. At pH 7.0 and 25 degrees C, the kcat for 3HNR catalyzed DDBO oxidation is 14 s-1 and the K(m) is 5 microM; the kcat for SD catalyzed DDBO dehydration is 400 s-1 and the K(m) is 15 microM. Based on these kinetic constants, DDBO is a better substrate than the natural substrate scytalone for both 3HNR and SD at neutral pH. An explanation for the preference of DDBO over scytalone in the oxidation and dehydration reactions is offered.

Dynamic Effects of Initial pH of Substrate on Biological Growth and Metamorphosis of Black Soldier Fly (Diptera: Stratiomyidae).

PubMed

Ma, Junhua; Lei, Yanyan; Rehman, Kashif Ur; Yu, Ziniu; Zhang, Jibin; Li, Wu; Li, Qing; Tomberlin, Jeffery K; Zheng, Longyu

2018-02-08

Edible insects have become a recognized alternative and sustainable source of high-quality proteins and fats for livestock or human consumption. In the production process of black soldier fly (BSF), (Hermetia illucens L. [Diptera: Stratiomyidae]), initial substrate pH is a critical parameter to ensure the best value of insect biomass, life history traits, and quality bio-fertilizer. This study examined the impact of initial pH values on BSF larvae production, development time, and adult longevity. The BSF were reared on artificial diet with initial pH of 2.0, 4.0, 6.0, 8.0, and 10.0; the control was set at 7.0. Final BSF larval weight was significantly greater in substrates having initial pH 6.0 (0.21 g), control 7.0 (0.20 g), and 10.0 (0.20 g) with no significant difference among them, whereas larval weight reared with initial pH 2.0 and 4.0 were lowest at 0.16 g (-23%). Prepupal weight was greatest when larvae were reared on substrates with initial pH 6.0 (0.18 g), control 7.0 (0.19 g), 8.0 (0.18 g), and 10.0 (0.18 g). In contrast, the prepupal weight of larvae reared on diets with initial pH 2.0 was lowest at 0.15 g (-22%). Larval development time was 21.19 d at pH 8.0, about 3 d (12.5%) shorter than that of those reared on diets with initial pH 6.0, 7.0 control, and 10.0. In all treatments, pH shifted to 5.7 after 3-4 d and 8.5 after 16-17 d except for two groups (2.0 and 4.0) where the pH remained slightly acidic 5.0 and 6.5, respectively. © The Author(s) 2018. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Product development studies of amino acid conjugate of Aceclofenac.

PubMed

Singh, Ajay Pal; Ramadan, Wafa Mossa; Dahiya, Rajiv; Sarpal, A S; Pathak, Kamla

2009-04-01

The prodrugs designed by classical approach increase lipophilicity of the drug, which decreases the water solubility thus decreasing the concentration gradient, which controls drug absorption. To overcome the limitations of traditional prodrug approach, water soluble prodrugs can be designed by adding selected amino acid to the drug moiety that are the substrates for the enzyme located at the intestinal brush border thus overcoming pharmaceutical problem without compromising bioavailability. ACaa (Amino acid conjugate of Aceclofenac) was synthesized by conjugation with l-phenylalanine by conventional coupling method using N, N-dicyclohexylcarbodiimide and ACaa was characterized by melting point, TLC, photomicrograph, UV, FT-IR, FT-NMR, MS-FAB, XRD and DSC. As a part of product development study ACaa was subjected to studies like In-vivo in albino rats and in-vitro like ACaa reversion to AC (Aceclofenac) in aqueous buffers of pH 1.21, 2.38. 3.10, 6.22 and 7.41, at a constant concentration (0.05M), ionic strength (micro = 0.5) and at a temperature of 37 degrees C +/- 0.5 degrees C, ACaa showed negligible reversion (2.15 %) up to 24 hrs study at acidic pH thus suggesting stability in acidic environment of stomach, the rate of reversion increased as pH of medium increased. pH- partition profile, pH- solubility profile and micromeritic studies were also carried out in comparison to pure drug. The solubility and lipophilicity of ACaa exhibited higher values at all pH range when compared to AC. The micromeritic properties also evaluated in terms of particle shape and size, IQCS and kurtosis. Resulting IQCS value approached zero thus suggesting reducing in the degree of skewness.

Fermentation pH Modulates the Size Distributions and Functional Properties of Gluconobacter albidus TMW 2.1191 Levan

PubMed Central

Ua-Arak, Tharalinee; Jakob, Frank; Vogel, Rudi F.

2017-01-01

Bacterial levan has gained an increasing interest over the last decades due to its unique characteristics and multiple possible applications. Levan and other exopolysaccharides (EPSs) production are usually optimized to obtain the highest concentration or yield while a possible change of the molecular size and mass during the production process is mostly neglected. In this study, the molar mass and radius of levan samples were monitored during fermentations with the food-grade, levan-producing acetic acid bacterium Gluconobacter (G.) albidus TMW 2.1191 in shake flasks (without pH control) and bioreactors (with pH control at 4.5, 5.5 and 6.5, respectively). In uncontrolled fermentations, the levan size/molar mass continuously decreased concomitantly with the continuous acidification of the nutrient medium. On the contrary, the amount, molar mass and size of levan could be directly influenced by controlling the pH during fermentation. Using equal initial substrate amounts, the largest weight average molar mass and geometric radius of levan were observed at constant pH 6.5, while the highest levan concentration was obtained at constant pH 4.5. Since there is a special demand to find suitable hydrocolloids from food-grade bacteria to develop novel gluten-free (GF) products, these differently produced levans were used for baking of GF breads, and the best quality improvement was obtained by addition of levan with the highest mass and radius. This work, therefore, demonstrates for the first time that one bacterial strain can produce specific high molecular weight fractions of one EPS type, which differ in properties and sizes among each other in dependence of the controllable production conditions. PMID:28522999

Smooth model surfaces from lignin derivatives. II. Adsorption of polyelectrolytes and PECs monitored by QCM-D.

PubMed

Norgren, Magnus; Gärdlund, Linda; Notley, Shannon M; Htun, Myat; Wågberg, Lars

2007-03-27

For the first time to the knowledge of the authors, well-defined and stable lignin model surfaces have been utilized as substrates in polyelectrolyte adsorption studies. The adsorption of polyallylamine (PAH), poly(acrylic acid) (PAA), and polyelectrolyte complexes (PECs) was monitored using quartz crystal microgravimetry with dissipation (QCM-D). The PECs were prepared by mixing PAH and PAA at different ratios and sequences, creating both cationic and anionic PECs with different charge levels. The adsorption experiments were performed in 1 and 10 mM sodium chloride solutions at pH 5 and 7.5. The highest adsorption of PAH and cationic PECs was found at pH 7.5, where the slightly negatively charged nature of the lignin substrate is more pronounced, governing electrostatic attraction of oppositely charged polymeric substances. An increase in the adsorption was further found when the electrolyte concentration was increased. In comparison, both PAA and the anionic PEC showed remarkably high adsorption to the lignin model film. The adsorption of PAA was further studied on silica and was found to be relatively low even at high electrolyte concentrations. This indicated that the high PAA adsorption on the lignin films was not induced by a decreased solubility of the anionic polyelectrolyte. The high levels of adsorption on lignin model surfaces found both for PAA and the anionic PAA-PAH polyelectrolyte complex points to the presence of strong nonionic interactions in these systems.

[Enzymatic characteristics of peroxidase from Chrysanthemum morifolium cv. Bo-ju].

PubMed

Zhu, Yu-Yun; Lyu, Xin-Lin; Li, Xiang-Wei; Zhang, Dong; Dong, Li-Hua; Zhu, Jing-Jing; Wang, Zhi-Min; Zhang, Jin-Zhen

2018-04-01

The enzymatic browning is one of the main reasons for affecting the quality of medicinal flowers. In the process of chrysanthemum harvesting and processing, improper treatment will lead to the browning and severely impact the appearance and quality of chrysanthemum. Peroxidase enzyme is one of the oxidoreductases that cause enzymatic browning of fresh chrysanthemum. The enzymatic characteristics of peroxidase (POD) in chrysanthemum were studied in this paper. In this experiment, the effects of different reaction substrates and their concentrations, PH value of buffer and reaction temperatures on the activity of POD enzyme were investigated. The results showed that the optimal substrate of POD was guaiacol, and the optimal concentration of POD was 50 mmol·L⁻¹. The optimal pH value and reaction temperature were 4.4 and 30-35 °C, respectively. Michaelis-Menten equation was obtained to express the kinetics of enzyme-catalyzed reaction of POD, Km=0.193 mol·L⁻¹, Vmax=0.329 D·min⁻¹. In addition, the results of POD enzyme thermal stability test showed that the POD enzyme activity was inhibited when being treated at 80 °C for 4 min or at 100 °C for 2 min. The above results were of practical significance to reveal the enzymatic browning mechanism, control the enzymatic browning and improve the quality of chrysanthemum, and can also provide the basis for the harvesting and processing of medicinal materials containing polyphenols. Copyright© by the Chinese Pharmaceutical Association.

The Effect of Nitrogen Form on pH and Petunia Growth in a WholeTree Substrate

USDA-ARS?s Scientific Manuscript database

The objective of our research was to investigate the effect of nitrogen form and proportion on peat-lite (PL) and WholeTree (WT) substrate pH and petunia growth. Chipped whole pine trees (consisting of needles, limbs, bark, wood and cones) were obtained from a commercial fuel wood chipping operation...

Production of ethanol from enzymatically hydrolyzed orange peel by the yeast Saccharomyces cerevisiae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grohmann, K.; Baldwin, E.A.; Buslig, B.S.

The authors extended their previous investigations of enzymatic hydrolysis of polysaccharides in orange peel by commercial cellulase and pectinase enzymes to higher, more practical concentrations of orange peel solids. High yields of saccharification could be maintained even at substrate concentrations as high as 22-23%, but the rates of solubilization and saccarification decreased 2-3-fold. They also tested the fermentability of these hydrolysates by the yeast Saccharomyces cerevisiae, which revealed the presence of inhibitory compounds. These compounds could be removed by the filtration of hydrolyzed peel. Successful fermentations of filtered hydrolysates were achieved after pH adjustment with calcium carbonate. 27 refs., 6more » figs., 1 tab.« less

Yield and cold storage of Trichoderma conidia is influenced by substrate pH and storage temperature.

PubMed

Steyaert, Johanna M; Chomic, Anastasia; Nieto-Jacobo, Maria; Mendoza-Mendoza, Artemio; Hay, Amanda J; Braithwaite, Mark; Stewart, Alison

2017-05-01

In this study we examined the influence of the ambient pH during morphogenesis on conidial yield of Trichoderma sp. "atroviride B" LU132 and T. hamatum LU593 and storage at low temperatures. The ambient pH of the growth media had a dramatic influence on the level of Trichoderma conidiation and this was dependent on the strain and growth media. On malt-extract agar, LU593 yield decreased with increasing pH (3-6), whereas yield increased with increasing pH for LU132. During solid substrate production the reverse was true for LU132 whereby yield decreased with increasing pH. The germination potential of the conidia decreased significantly over time in cold storage and the rate of decline was a factor of the strain, pH during morphogenesis, growth media, and storage temperature. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Paper-based potentiometric pH sensor using carbon electrode drawn by pencil

NASA Astrophysics Data System (ADS)

Kawahara, Ryotaro; Sahatiya, Parikshit; Badhulika, Sushmee; Uno, Shigeyasu

2018-04-01

A flexible and disposable paper-based pH sensor fabricated with a pencil-drawn working electrode and a Ag/AgCl paste reference electrode is demonstrated for the first time to show pH response by the potentiometric principle. The sensor substrate is made of chromatography paper with a wax-printed hydrophobic area, and various types of carbon pencils are tested as working electrodes. The pH sensitivities of the electrodes drawn by carbon pencils with different hardnesses range from 16.5 to 26.9 mV/pH. The proposed sensor is expected to be more robust against shape change in electrodes on a flexible substrate than other types of chemiresistive/amperometric pH sensors.

Comparative reactivity of TpRu(L)(NCMe)Ph (L = CO or PMe3): impact of ancillary ligand l on activation of carbon-hydrogen bonds including catalytic hydroarylation and hydrovinylation/oligomerization of ethylene.

PubMed

Foley, Nicholas A; Lail, Marty; Lee, John P; Gunnoe, T Brent; Cundari, Thomas R; Petersen, Jeffrey L

2007-05-30

Complexes of the type TpRu(L)(NCMe)R [L = CO or PMe3; R = Ph or Me; Tp = hydridotris(pyrazolyl)borate] initiate C-H activation of benzene. Kinetic studies, isotopic labeling, and other experimental evidence suggest that the mechanism of benzene C-H activation involves reversible dissociation of acetonitrile, reversible benzene coordination, and rate-determining C-H activation of coordinated benzene. TpRu(PMe3)(NCMe)Ph initiates C-D activation of C6D6 at rates that are approximately 2-3 times more rapid than that for TpRu(CO)(NCMe)Ph (depending on substrate concentration); however, the catalytic hydrophenylation of ethylene using TpRu(PMe3)(NCMe)Ph is substantially less efficient than catalysis with TpRu(CO)(NCMe)Ph. For TpRu(PMe3)(NCMe)Ph, C-H activation of ethylene, to ultimately produce TpRu(PMe3)(eta3-C4H7), is found to kinetically compete with catalytic ethylene hydrophenylation. In THF solutions containing ethylene, TpRu(PMe3)(NCMe)Ph and TpRu(CO)(NCMe)Ph separately convert to TpRu(L)(eta3-C4H7) (L = PMe3 or CO, respectively) via initial Ru-mediated ethylene C-H activation. Heating mesitylene solutions of TpRu(L)(eta3-C4H7) under ethylene pressure results in the catalytic production of butenes (i.e., ethylene hydrovinylation) and hexenes.

Selective uptake of major and trace elements in Erica andevalensis, an endemic species to extreme habitats in the Iberian Pyrite Belt.

PubMed

Monaci, Fabrizio; Leidi, Eduardo O; Dolores, Mingorance Maria; Valdés, Benito Oliva; Rossini, Sabina Sabina; Bargagli, Roberto

2011-01-01

To assess the ecophysiological traits and the phytoremediation potential of the endemic heather Erica andevalensis, we determined the concentrations of major and trace elements in different plant parts and in rizosphere soils from Riotinto mining district (Huelva, Spain). The results showed that E. andevalensis may grow on substrates with very high As, Cu, Fe and Pb concentrations (up to 4114, 1050, 71900 and 15614 microg/g dry weight, respectively), very low availability of macro- and micronutrients and with pH values ranging from 3.3 to 4.9. In these harsh edaphic conditions E. andevalensis selectively absorbed and translocated essential nutrients and excludes potentially phytotoxic elements, which were accumulated in the root epidermis. The concentrations of major and trace elements in E. andevalensis aerial parts from the Riotinto mining district were in the normal range for plants; likewise other Erica species it accumulated Mn and only in a very polluted site we measured leaf concentrations of As and Pb within the excessive or toxic limits for plants. Differently from previous studies, which emphasized the soil pH and bioavailability of phytotoxic elements as the main stress factors, this study showed that in the Riotinto region, E. andevalensis can tolerate wide range of pH and toxic element concentrations; the harshest environments colonized by monospecific patches of this species were characterized above all by very low availability of nutrients. The extraordinary capability to adapt to these extreme habitats made E. andevalensis a priority species to promote the phytostabilization and the development of a self-sustaining vegetative cover on Riotinto mine tailings.

Hydrogen and lipid production from starch wastewater by co-culture of anaerobic sludge and oleaginous microalgae with simultaneous COD, nitrogen and phosphorus removal.

PubMed

Ren, Hong-Yu; Liu, Bing-Feng; Kong, Fanying; Zhao, Lei; Ren, Nanqi

2015-11-15

Anaerobic sludge (AS) and microalgae were co-cultured to enhance the energy conversion and nutrients removal from starch wastewater. Mixed ratio, starch concentration and initial pH played critical roles on the hydrogen and lipid production of the co-culture system. The maximum hydrogen production of 1508.3 mL L(-1) and total lipid concentration of 0.36 g L(-1) were obtained under the optimized mixed ratio (algae:AS) of 30:1, starch concentration of 6 g L(-1) and initial pH of 8. The main soluble metabolites in dark fermentation were acetate and butyrate, most of which can be consumed in co-cultivation. When sweet potato starch wastewater was used as the substrate, the highest COD, TN and TP removal and energy conversion efficiencies reached 80.5%, 88.7%, 80.1% and 34.2%, which were 176%, 178%, 200% and 119% higher than that of the control group (dark fermentation), respectively. This research provided a novel approach and achieved efficient simultaneous energy recovery and nutrients removal from starch wastewater by the co-culture system. Copyright © 2015 Elsevier Ltd. All rights reserved.

Arsenic in the rhizosphere soil solution of ferns.

PubMed

Wei, Chaoyang; Zheng, Huan; Yu, Jiangping

2012-12-01

The aim of this study was to explore the evidence of arsenic hyperaccumulation in plant rhizosphere solutions. Six common fern plants were selected and grown in three types of substrate: arsenic (As) -tailings, As-spiked soil, and soil-As-tailing composites. A rhizobox was designed with an in-situ collection of soil solutions to analyze changes in the As concentration and valence as well as the pH, dissolved organic carbon (DOC) and total nitrogen (TN). Arsenite composed less than 20% of the total As, and As depletion was consistent with N depletion in the rhizosphere solutions of the various treatments. The As concentrations in the rhizosphere and non-rhizosphere solutions in the presence of plants were lower than in the respective controls without plants, except for in the As-spiked soils. The DOC concentrations were invariably higher in the rhizosphere versus non-rhizosphere solutions from the various plants; however, no significant increase in the DOC content was observed in Pteris vittata, in which only a slight decrease in pH appeared in the rhizosphere compared to non-rhizosphere solutions. The results showed that As reduction by plant roots was limited, acidification-induced solubilization was not the mechanism for As hyperaccumulation.

Ionically cross-linked poly(allylamine) as a stimulus-responsive underwater adhesive: ionic strength and pH effects.

PubMed

Lawrence, Patrick G; Lapitsky, Yakov

2015-02-03

Gel-like coacervates that adhere to both hydrophilic and hydrophobic substrates under water have recently been prepared by ionically cross-linking poly(allylamine) (PAH) with pyrophosphate (PPi) and tripolyphosphate (TPP). Among the many advantages of these underwater adhesives (which include their simple preparation and low cost) is their ability to dissolve on demand when exposed to high or low pH. To further analyze their stimulus-responsive properties, we have investigated the pH and ionic strength effects on the formation, rheology and adhesion of PAH/PPi and PAH/TPP complexes. The ionic cross-linker concentrations needed to form these adhesives decreased with increasing pH and ionic strength (although the complexes ceased to form when the parent solution pH exceeded ca. 8.5; i.e., the effective pKa of PAH). Once formed, their ionic cross-links were most stable (as inferred from their relaxation times) at near-neutral or slightly alkaline pH values (of roughly 6.5-9) and at low ionic strengths. The decrease in ionic cross-link stability within complexes prepared at other pH values and at elevated (150-300 mM) NaCl concentrations diminished both the strength and longevity of adhesion (although, under most conditions tested, the short-term tensile adhesion strengths remained above 10(5) Pa). Additionally, the sensitivity of PAH/PPi and PAH/TPP complexes to ionic strength was demonstrated as a potential route to injectable adhesive design (where spontaneous adhesive formation was triggered via injection of low-viscosity, colloidal PAH/TPP dispersions into phosphate buffered saline). Thus, while the sensitivity of ionically cross-linked PAH networks to pH and ionic strength can weaken their adhesion, it can also impart them with additional functionality, such as minimally invasive, injectable delivery, and ability to form and dissolve their bonds on demand.

Electro-oxidation and characterization of nickel foam electrode for removing boron.

PubMed

Kartikaningsih, Danis; Huang, Yao-Hui; Shih, Yu-Jen

2017-01-01

The electrocoagulation (EC) using metallic Ni foam as electrodes was studied for the removal of boron from solution. The electrolytic parameters were pH (4-12), current density (0.6-2.5 mA cm -2 ), and initial concentration of boron (10-100 mg L -1 ). Experimental results revealed that removal efficiency was maximized at pH 8-9, and decreased as the pH increased beyond that range. At particular onset potentials (0.5-0.8 V vs. Hg/HgO), the micro-granular nickel oxide that was created on the surface of the nickel metal substrate depended on pH, as determined by cyclic voltammetry. Most of the crystallites of the precipitates comprised a mixed phase of β-Ni(OH) 2 , a theophrastite phase, and NiOOH, as revealed by XRD and SEM analyses. A current density of 1.25 mA cm -2 was effective in the EC of boron, and increasing the concentration of boric acid from 10 to 100 mg L -1 did not greatly impair removal efficiency. A kinetic investigation revealed that the reaction followed a pseudo-second order rate model. The optimal conditions under which 99.2% of boron was removed from treated wastewater with 10 mg L -1 -B, leaving less than 0.1 mg L -1 -B in the electrolyte, were pH 8 and 1.25 mA cm -2 for 120 min. Copyright © 2016 Elsevier Ltd. All rights reserved.

Structure and substrate ion binding in the sodium/proton antiporter PaNhaP

PubMed Central

Wöhlert, David; Kühlbrandt, Werner; Yildiz, Özkan

2014-01-01

Sodium/proton antiporters maintain intracellular pH and sodium levels. Detailed structures of antiporters with bound substrate ions are essential for understanding how they work. We have resolved the substrate ion in the dimeric, electroneutral sodium/proton antiporter PaNhaP from Pyrococcus abyssi at 3.2 Å, and have determined its structure in two different conformations at pH 8 and pH 4. The ion is coordinated by three acidic sidechains, a water molecule, a serine and a main-chain carbonyl in the unwound stretch of trans-membrane helix 5 at the deepest point of a negatively charged cytoplasmic funnel. A second narrow polar channel may facilitate proton uptake from the cytoplasm. Transport activity of PaNhaP is cooperative at pH 6 but not at pH 5. Cooperativity is due to pH-dependent allosteric coupling of protomers through two histidines at the dimer interface. Combined with comprehensive transport studies, the structures of PaNhaP offer unique new insights into the transport mechanism of sodium/proton antiporters. DOI: http://dx.doi.org/10.7554/eLife.03579.001 PMID:25426802

Direct immobilization of tyrosinase enzyme from natural mushrooms (Agaricus bisporus) on D-sorbitol cinnamic ester.

PubMed

Marín-Zamora, María Elisa; Rojas-Melgarejo, Francisco; García-Cánovas, Francisco; García-Ruiz, Pedro Antonio

2006-11-10

Mushroom tyrosinase was immobilized from an extract onto the totally cinnamoylated derivative of D-sorbitol by direct adsorption as a result of the intense hydrophobic interactions that took place. The immobilization pH value and mass of lyophilized mushrooms were important parameters that affected the immobilization efficiency, while the immobilization time and immobilization support concentration were not important in this respect. The extracted/immobilized enzyme could best be measured above pH 3.5 and the optimum measuring temperature was 55 degrees C. The apparent Michaelis constant using 4-tert-butylcatechol as substrate was 0.38+/-0.02 mM, which was lower than for the soluble enzyme from Sigma (1.41+/-0.20 mM). Immobilization stabilized the extracted enzyme against thermal inactivation and made it less susceptible to activity loss during storage. The operational stability was higher than in the case of the tyrosinase supplied by Sigma and immobilized on the same support. The results show that the use of p-nitrophenol as enzyme-inhibiting substrate during enzyme extraction and immobilization made the use of ascorbic acid unnecessary and is a suitable method for extracting and immobilizing the tyrosinase enzyme, providing good enzymatic activity and stability.

Rhamnolipid CMC prediction.

PubMed

Kłosowska-Chomiczewska, I E; Mędrzycka, K; Hallmann, E; Karpenko, E; Pokynbroda, T; Macierzanka, A; Jungnickel, C

2017-02-15

Relationships between the purity, pH, hydrophobicity (logK ow ) of the carbon substrate, and the critical micelle concentration (CMC) of rhamnolipid type biosurfactants (RL) were investigated using a quantitative structure-property relationship (QSPR) approach and are presented here for the first time. Measured and literature CMC values of 97 RLs, representing biosurfactants at different stages of purification, were considered. An arbitrary scale for RLs purity was proposed and used in the modelling. A modified evolutionary algorithm was used to create clusters of equations to optimally describe the relationship between CMC and logK ow , pH and purity (the optimal equation had an R 2 of 0.8366). It was found that hydrophobicity of the carbon substrate used for the biosynthesis of the RL had the most significant influence on the final CMC of the RL. Purity of the RLs was also found to have a significant impact, where generally the less pure the RL the higher the CMC. These results were in accordance with our experimental data. Therefore, our model equation may be used for controlling the biosynthesis of biosurfactants with properties targeted for specific applications. Copyright © 2016 Elsevier Inc. All rights reserved.

Modified kinetic-hydraulic UASB reactor model for treatment of wastewater containing biodegradable organic substrates.

PubMed

El-Seddik, Mostafa M; Galal, Mona M; Radwan, A G; Abdel-Halim, Hisham S

2016-01-01

This paper addresses a modified kinetic-hydraulic model for up-flow anaerobic sludge blanket (UASB) reactor aimed to treat wastewater of biodegradable organic substrates as acetic acid based on Van der Meer model incorporated with biological granules inclusion. This dynamic model illustrates the biomass kinetic reaction rate for both direct and indirect growth of microorganisms coupled with the amount of biogas produced by methanogenic bacteria in bed and blanket zones of reactor. Moreover, the pH value required for substrate degradation at the peak specific growth rate of bacteria is discussed for Andrews' kinetics. The sensitivity analyses of biomass concentration with respect to fraction of volume of reactor occupied by granules and up-flow velocity are also demonstrated. Furthermore, the modified mass balance equations of reactor are applied during steady state using Newton Raphson technique to obtain a suitable degree of freedom for the modified model matching with the measured results of UASB Sanhour wastewater treatment plant in Fayoum, Egypt.

Effect of Organic Substrates on the Photocatalytic Reduction of Cr(VI) by Porous Hollow Ga2O3 Nanoparticles

PubMed Central

Liu, Jin; Gan, Huihui; Wu, Hongzhang; Zhang, Xinlei; Zhang, Jun; Li, Lili; Wang, Zhenling

2018-01-01

Porous hollow Ga2O3 nanoparticles were successfully synthesized by a hydrolysis method followed by calcination. The prepared samples were characterized by field emission scanning electron microscope, transmission electron microscope, thermogravimetry and differential scanning calorimetry, UV-vis diffuse reflectance spectra and Raman spectrum. The porous structure of Ga2O3 nanoparticles can enhance the light harvesting efficiency, and provide lots of channels for the diffusion of Cr(VI) and Cr(III). Photocatalytic reduction of Cr(VI), with different initial pH and degradation of several organic substrates by porous hollow Ga2O3 nanoparticles in single system and binary system, were investigated in detail. The reduction rate of Cr(VI) in the binary pollutant system is markedly faster than that in the single Cr(VI) system, because Cr(VI) mainly acts as photogenerated electron acceptor. In addition, the type and concentration of organic substrates have an important role in the photocatalytic reduction of Cr(VI). PMID:29690548

Effect of an ADP analog on isometric force and ATPase activity of active muscle fibers.

PubMed

Karatzaferi, Christina; Myburgh, Kathryn H; Chinn, Marc K; Franks-Skiba, Kathleen; Cooke, Roger

2003-04-01

The role played by ADP in modulating cross-bridge function has been difficult to study, because it is hard to buffer ADP concentration in skinned muscle preparations. To solve this, we used an analog of ADP, spin-labeled ADP (SL-ADP). SL-ADP binds tightly to myosin but is a very poor substrate for creatine kinase or pyruvate kinase. Thus ATP can be regenerated, allowing well-defined concentrations of both ATP and SL-ADP. We measured isometric ATPase rate and isometric tension as a function of both [SL-ADP], 0.1-2 mM, and [ATP], 0.05-0.5 mM, in skinned rabbit psoas muscle, simulating fresh or fatigued states. Saturating levels of SL-ADP increased isometric tension (by P'), the absolute value of P' being nearly constant, approximately 0.04 N/mm(2), in variable ATP levels, pH 7. Tension decreased (50-60%) at pH 6, but upon addition of SL-ADP, P' was still approximately 0.04 N/mm(2). The ATPase was inhibited competitively by SL-ADP with an inhibition constant, K(i), of approximately 240 and 280 microM at pH 7 and 6, respectively. Isometric force and ATPase activity could both be fit by a simple model of cross-bridge kinetics.

Effect of chelators and nisin produced in situ on inhibition and inactivation of gram negatives.

PubMed

Boziaris, I S; Adams, M R

1999-12-15

The ability of chelators and nisin generated in situ to inhibit and inactivate E. coli and other gram negatives in a model substrate was investigated. The effect of various chelators and different concentrations of exogenous nisin on inhibition of E. coli in broth medium showed that only EDTA and pyrophosphates were able to cause appreciable inhibition of E. coli by nisin. In a broth where L. lactis NCFB 497 produced nisin in a concentration of 250-300 IU/ml, pyrophosphates were unable to inactivate E. coli. Under the same conditions, addition of EDTA led to inactivation of E. coli at neutral and slightly acidic pH only. A cocktail of strains of E. coli was less sensitive than E. coli ATCC 25922 alone. Pseudomonas aeruginosa was more sensitive and salmonellae more resistant. EDTA also caused a slight reduction in the L. lactis population and its biochemical activity as regards pH drop and acid production. Some of the inhibition of E. coli could be ascribed to the physical presence of Lactococcus cells rather than their metabolites excreted into the medium. Failure to observe any inhibition in fermented broths at their natural pH (4.0) was ascribed to the poor chelating power of EDTA under acid conditions.

Inhibition factors and Kinetic model for ammonium inhibition on the anammox process of the SNAD biofilm.

PubMed

Zheng, Zhaoming; Li, Jun; Ma, Jing; Du, Jia; Wang, Fan; Bian, Wei; Zhang, Yanzhuo; Zhao, Baihang

2017-03-01

The aim of the present work was to evaluate the anaerobic ammonium oxidation (anammox) activity of simultaneous partial nitrification, anammox and denitrification (SNAD) biofilm with different substrate concentrations and pH values. Kaldnes rings taken from the SNAD biofilm reactor were incubated in batch tests to determine the anammox activity. Haldane model was applied to investigate the ammonium inhibition on anammox process. As for nitrite inhibition, the NH 4 + -N removal rate of anammox process remained 87.4% of the maximum rate with the NO 2 - -N concentration of 100mg/L. Based on the results of Haldane model, no obvious difference in kinetic coefficients was observed under high or low free ammonia (FA) conditions, indicating that ammonium rather than FA was the true inhibitor for anammox process of SNAD biofilm. With the pH value of 7.0, the r max , Ks and K I of ammonium were 0.209kg NO 2 - -N/kg VSS/day, 9.5mg/L and 422mg/L, respectively. The suitable pH ranges for anammox process were 5.0 to 9.0. These results indicate that the SNAD biofilm performs excellent tolerance to adverse conditions. Copyright © 2016. Published by Elsevier B.V.

Enzymatic saccharification and fermentation of cellulosic date palm wastes to glucose and lactic acid.

PubMed

Alrumman, Sulaiman A

2016-01-01

The bioconversion of cellulosic wastes into high-value bio-products by saccharification and fermentation processes is an important step that can reduce the environmental pollution caused by agricultural wastes. In this study, enzymatic saccharification of treated and untreated date palm cellulosic wastes by the cellulases from Geobacillus stearothermophilus was optimized. The alkaline pre-treatment of the date palm wastes was found to be effective in increasing the saccharification percentage. The maximum rate of saccharification was found at a substrate concentration of 4% and enzyme concentration of 30 FPU/g of substrate. The optimum pH and temperature for the bioconversions were 5.0 and 50°C, respectively, after 24h of incubation, with a yield of 31.56mg/mL of glucose at a saccharification degree of 71.03%. The saccharification was increased to 94.88% by removal of the hydrolysate after 24h by using a two-step hydrolysis. Significant lactic acid production (27.8mg/mL) was obtained by separate saccharification and fermentation after 72h of incubation. The results indicate that production of fermentable sugar and lactic acid is feasible and may reduce environmental pollution by using date palm wastes as a cheap substrate. Copyright © 2015 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

Nucleoside pyrophosphatase activity associated with pig kidney alkaline phosphatase

PubMed Central

Wass, Milica; Butterworth, P. J.

1971-01-01

1. A study was made of the hydrolysis, at pH9.0, of ATP and ADP catalysed by pig kidney alkaline phosphatase. Both of these nucleoside pyrophosphates are substrates for the enzyme; Km values are 4×10−5m for ATP and 6.3×10−5m for ADP. Vmax. for ADP is approximately double that of ATP. 2. Above 0.1mm approximately, both ATP and ADP are inhibitory, but the inhibition is reversible by the addition of Mg2+ ions to form MgATP2− or MgADP− complexes. The complexes, besides being non-inhibitory, are also substrates for the enzyme with Km values identical with those of the respective free nucleotides. 3. Mg2+ ions are inhibitory when present in excess of ATP or ADP. The degree of inhibition is greater with ATP as substrate, but with both ATP and ADP a mixed competitive–non-competitive type of inhibition is observed. 4. It is suggested that under normal conditions the enzyme is inhibited by cellular concentrations of ATP plus ADP but that an increase in the concentration of Mg2+ ions stimulates activity by relieving nucleoside pyrophosphate inhibition. The properties may be of importance in the regulation of the transport of bivalent cations. PMID:4331861

Enzymatic saccharification and fermentation of cellulosic date palm wastes to glucose and lactic acid

PubMed Central

Alrumman, Sulaiman A.

2016-01-01

The bioconversion of cellulosic wastes into high-value bio-products by saccharification and fermentation processes is an important step that can reduce the environmental pollution caused by agricultural wastes. In this study, enzymatic saccharification of treated and untreated date palm cellulosic wastes by the cellulases from Geobacillus stearothermophilus was optimized. The alkaline pre-treatment of the date palm wastes was found to be effective in increasing the saccharification percentage. The maximum rate of saccharification was found at a substrate concentration of 4% and enzyme concentration of 30 FPU/g of substrate. The optimum pH and temperature for the bioconversions were 5.0 and 50 °C, respectively, after 24 h of incubation, with a yield of 31.56 mg/mL of glucose at a saccharification degree of 71.03%. The saccharification was increased to 94.88% by removal of the hydrolysate after 24 h by using a two-step hydrolysis. Significant lactic acid production (27.8 mg/mL) was obtained by separate saccharification and fermentation after 72 h of incubation. The results indicate that production of fermentable sugar and lactic acid is feasible and may reduce environmental pollution by using date palm wastes as a cheap substrate. PMID:26887233

The complicated substrates enhance the microbial diversity and zinc leaching efficiency in sphalerite bioleaching system.

PubMed

Xiao, Yunhua; Xu, YongDong; Dong, Weiling; Liang, Yili; Fan, Fenliang; Zhang, Xiaoxia; Zhang, Xian; Niu, Jiaojiao; Ma, Liyuan; She, Siyuan; He, Zhili; Liu, Xueduan; Yin, Huaqun

2015-12-01

This study used an artificial enrichment microbial consortium to examine the effects of different substrate conditions on microbial diversity, composition, and function (e.g., zinc leaching efficiency) through adding pyrite (SP group), chalcopyrite (SC group), or both (SPC group) in sphalerite bioleaching systems. 16S rRNA gene sequencing analysis showed that microbial community structures and compositions dramatically changed with additions of pyrite or chalcopyrite during the sphalerite bioleaching process. Shannon diversity index showed a significantly increase in the SP (1.460), SC (1.476), and SPC (1.341) groups compared with control (sphalerite group, 0.624) on day 30, meanwhile, zinc leaching efficiencies were enhanced by about 13.4, 2.9, and 13.2%, respectively. Also, additions of pyrite or chalcopyrite could increase electric potential (ORP) and the concentrations of Fe3+ and H+, which were the main factors shaping microbial community structures by Mantel test analysis. Linear regression analysis showed that ORP, Fe3+ concentration, and pH were significantly correlated to zinc leaching efficiency and microbial diversity. In addition, we found that leaching efficiency showed a positive and significant relationship with microbial diversity. In conclusion, our results showed that the complicated substrates could significantly enhance microbial diversity and activity of function.

Design and testing of a unique randomized gravity, continuous flow bioreactor

NASA Technical Reports Server (NTRS)

Lassiter, Carroll B.

1993-01-01

A rotating, null gravity simulator, or Couette bioreactor was successfully used for the culture of mammalian cells in a simulated microgravity environment. Two limited studies using Lipomyces starkeyi and Streptomyces clavuligerus were also conducted under conditions of simulated weightlessness. Although these studies with microorganisms showed promising preliminary results, oxygen limitations presented significant limitations in studying the biochemical and cultural characteristics of these cell types. Microbial cell systems such as bacteria and yeast promise significant potential as investigative models to study the effects of microgravity on membrane transport, as well as substrate induction of inactive enzyme systems. Additionally, the smaller size of the microorganisms should further reduce the gravity induced oscillatory particle motion and thereby improve the microgravity simulation on earth. Focus is on the unique conceptual design, and subsequent development of a rotating bioreactor that is compatible with the culture and investigation of microgravity effects on microbial systems. The new reactor design will allow testing of highly aerobic cell types under simulated microgravity conditions. The described reactor affords a mechanism for investigating the long term effects of reduced gravity on cellular respiration, membrane transfer, ion exchange, and substrate conversions. It offers the capability of dynamically altering nutrients, oxygenation, pH, carbon dioxide, and substrate concentration without disturbing the microgravity simulation, or Couette flow, of the reactor. All progeny of the original cell inoculum may be acclimated to the simulated microgravity in the absence of a substrate or nutrient. The reactor has the promise of allowing scientists to probe the long term effects of weightlessness on cell interactions in plants, bacteria, yeast, and fungi. The reactor is designed to have a flow field growth chamber with uniform shear stress, yet transfer high concentrations of oxygen into the culture medium. The system described allows for continuous, on line sampling for production of product without disturbing fluid and particle dynamics in the reaction chamber. It provides for the introduction of substrate, or control substances after cell adaptation to simulated microgravity has been accomplished. The reactor system provides for the nondisruptive, continuous flow replacement of nutrient and removal of product. On line monitoring and control of growth conditions such as pH and nutrient status are provided. A rotating distribution valve allows cessation of growth chamber rotation, thereby preserving the simulated microgravity conditions over longer periods of time.

Activity of influenza C virus O-acetylesterase with O-acetyl-containing compounds.

PubMed Central

Garcia-Sastre, A; Villar, E; Manuguerra, J C; Hannoun, C; Cabezas, J A

1991-01-01

Influenza C virus (strain C/Johannesburg/1/66) was grown, harvested, purified and used as source for the enzyme O-acetylesterase (N-acyl-O-acetylneuraminate O-acetylhydrolase; EC 3.1.1.53). This activity was studied and characterized with regard to some new substrates. The pH optimum of the enzyme is around 7.6, its stability at different pH values shows a result similar to that of the pH optimum, and its activity is well maintained in the pH range from 7.0 to 8.5 (all these tests were performed with 4-nitrophenyl acetate as substrate). Remarkable differences were found in the values of both Km and Vmax, with the synthetic substrates 4-nitrophenyl acetate, 2-nitrophenyl acetate, 4-methylumbelliferyl acetate, 1-naphthyl acetate and fluorescein diacetate. The use of 4-nitrophenyl acetate, 4-methylumbelliferyl acetate or 1-naphthyl acetate as substrate seems to be convenient for routine work, but it is better to carry out the measurements in parallel with those on bovine submandibular gland mucin (the latter is a natural and commercially available substrate). It was found that 4-acetoxybenzoic acid, as well as the methyl ester of 2-acetoxybenzoic acid, but not 2-acetoxybenzoic acid itself, are cleaved by this enzyme. Triacetin, di-O-acetyladenosine, tri-O-acetyladenosine, and di-O-acetyl-N-acetyladenosine phosphate, hitherto unreported as substrates for this viral esterase, are hydrolysed at different rates by this enzyme. We conclude that the O-acetylesterase from influenza C virus has a broad specificity towards both synthetic and natural non-sialic acid-containing substrates. Zn2+, Mn2+ and Pb2+ (as their chloride salts), N-acetylneuraminic acid, 4-methyl-umbelliferone and 2-acetoxybenzoic acid (acetylsalicylic acid) did not act as inhibitors. Images Fig. 1. PMID:1991039

Phosphatidic acid synthesis in yeast

PubMed Central

Kuhn, N. J.; Lynen, F.

1965-01-01

1. The presence of palmitoyl-CoA–l-glycerol 1-phosphate palmitoyltransferase (EC2.3.1.15) has been demonstrated in a particulate fraction of baker's yeast. 2. The enzyme has been characterized, and its activity studied as a function of pH and concentration of substrates. 3. Inhibition by thiol poisons and protection by acyl-CoA have been used to obtain information on the active site. 4. By various methods of supplying acyl radicals, the species `palmitoyl-CoA' has been shown to be the true acyl donor to the transferase. PMID:14342236

Heat resistance of Bacillus cereus spores: effects of milk constituents and stabilizing additives.

PubMed

Mazas, M; López, M; Martínez, S; Bernardo, A; Martin, R

1999-04-01

Heat resistance of Bacillus cereus spores (ATCC 7004, 4342, and 9818) heated in different types of milk (skim, whole, and concentrated skim milk), skim milk containing stabilizing additives (sodium citrate, monopotassium phosphate, or disodium phosphate, 0.1%), and cream was investigated. Thermal resistance experiments were performed at temperatures within the range of 92 to 115 degrees C under continuous monitoring of pH. For strain 4342 no significant differences (P < 0.05) in D values were detected in any case. For strains 7004 and 9818 higher D values of about 20% were obtained in whole and concentrated skim milk than those calculated in skim milk. From all stabilizing additives tested, only sodium citrate and sodium phosphate increased the heat resistance for strain 9818. However, when the menstruum pH was measured at the treatment temperature, different pH values were found between the heating media. The differences in heat resistance observed could be due to a pH effect rather than to the difference in the substrates in which spores were heated. In contrast, when cream (fat content 20%) was used, lower D values were obtained, especially for strains 7004 and 9818. z values were not significantly modified by the milk composition, with an average z value of 7.95+/-0.20 degrees C for strain 7004, 7.88+/-0.10 degrees C for strain 4342, and 9.13+/-0.16 degrees C for strain 9818.

Hepatectomy-Related Hypophosphatemia: A Novel Phosphaturic Factor in the Liver-Kidney Axis

PubMed Central

Nomura, Kengo; Miyagawa, Atsumi; Shiozaki, Yuji; Sasaki, Shohei; Kaneko, Ichiro; Ito, Mikiko; Kido, Shinsuke; Segawa, Hiroko; Sano, Mitsue; Fukuwatari, Tsutomu; Shibata, Katsumi

2014-01-01

Marked hypophosphatemia is common after major hepatic resection, but the pathophysiologic mechanism remains unknown. We used a partial hepatectomy (PH) rat model to investigate the molecular basis of hypophosphatemia. PH rats exhibited hypophosphatemia and hyperphosphaturia. In renal and intestinal brush-border membrane vesicles isolated from PH rats, Na+-dependent phosphate (Pi) uptake decreased by 50%–60%. PH rats also exhibited significantly decreased levels of renal and intestinal Na+-dependent Pi transporter proteins (NaPi-IIa [NaPi-4], NaPi-IIb, and NaPi-IIc). Parathyroid hormone was elevated at 6 hours after PH. Hyperphosphaturia persisted, however, even after thyroparathyroidectomy in PH rats. Moreover, DNA microarray data revealed elevated levels of nicotinamide phosphoribosyltransferase (Nampt) mRNA in the kidney after PH, and Nampt protein levels and total NAD concentration increased significantly in the proximal tubules. PH rats also exhibited markedly increased levels of the Nampt substrate, urinary nicotinamide (NAM), and NAM catabolites. In vitro analyses using opossum kidney cells revealed that NAM alone did not affect endogenous NaPi-4 levels. However, in cells overexpressing Nampt, the addition of NAM led to a marked decrease in cell surface expression of NaPi-4 that was blocked by treatment with FK866, a specific Nampt inhibitor. Furthermore, FK866-treated mice showed elevated renal Pi reabsorption and hypophosphaturia. These findings indicate that hepatectomy-induced hypophosphatemia is due to abnormal NAM metabolism, including Nampt activation in renal proximal tubular cells. PMID:24262791

Potential application of waste from castor bean (Ricinus communis L.) for production for xylanase of interest in the industry.

PubMed

Herculano, Polyanna Nunes; Moreira, Keila Aparecida; Bezerra, Raquel Pedrosa; Porto, Tatiana Souza; de Souza-Motta, Cristina Maria; Porto, Ana Lúcia Figueiredo

2016-12-01

Xylanases activity (XY) from Aspergillus japonicus URM5620 produced by Solid-State Fermentation (SSF) of castor press cake (Ricinus communis) on different conditions of production and extraction by PEG/citrate aqueous two-phase system (ATPS) were investigated. XY production was influenced by substrate amount (5-10 g), initial moisture (15-35 %), pH (4.0-6.0) and temperature (25-35 °C), obtaining the maximum activity of 29,085 ± 1808 U g ds -1 using 5.0 g of substrate with initial moisture of 15 % at 25 °C and pH 6.0, after 120 h of fermentation. The influence of PEG molar mass (1000-8000 g mol -1 ), phase concentrations (PEG 20.0-24.0 % w/w and sodium citrate 15-20 % w/w) and pH (6.0-8.0) on partition coefficient, purification factor, yield and selectivity of XY were determinate. Enzyme partitioning into the PEG rich phase was favored by M PEG 8000 (g mol -1 ), C PEG 24 % (w/w), C C 20 % (w/w) and pH 8.0, resulting in partition coefficient of 50.78, activity yield of 268 %, 7.20-fold purification factor and selectivity of 293. A. japonicus URM5620 has a potential role in the development of a bioprocess for the XY production using low-cost media. In addition, the present study proved it is feasible to extract xylanase from SSF by adopting the one step ATPS consisting of PEG/citrate.

Melanin as an active layer in biosensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piacenti da Silva, Marina, E-mail: marinaness@yahoo.com; Congiu, Mirko, E-mail: congiumat@gmail.com; Oliveira Graeff, Carlos Frederico de, E-mail: graeff@fc.unesp.br

2014-03-15

The development of pH sensors is of great interest due to its extensive application in several areas such as industrial processes, biochemistry and particularly medical diagnostics. In this study, the pH sensing properties of an extended gate field effect transistor (EGFET) based on melanin thin films as active layer are investigated and the physical mechanisms related to the device operation are discussed. Thin films were produced from different melanin precursors on indium tin oxide (ITO) and gold substrates and were investigated by Atomic Force Microscopy and Electrochemical Impedance Spectroscopy. Experiments were performed in the pH range from 2 to 12.more » EGFETs with melanin deposited on ITO and on gold substrates showed sensitivities ranging from 31.3 mV/pH to 48.9 mV/pH, depending on the melanin precursor and the substrate used. The pH detection is associated with specific binding sites in its structure, hydroxyl groups and quinone imine.« less

Novel inexpensive fungi proteases: Production by solid state fermentation and characterization.

PubMed

Novelli, Paula Kern; Barros, Margarida Maria; Fleuri, Luciana Francisco

2016-05-01

A comparative study was carried out for proteases production using agroindustrial residues as substrate for solid state fermentation (SSF) of several fungal strains. High protease production was observed for most of the microorganisms studied, as well as very different biochemical characteristics, including activities at specific temperatures and a wide range of pH values. The enzymes produced were very different regarding optimum pH and they showed stability at 50 °C. Aspergillus oryzae showed stability at all pH values studied. Penicillium roquefortii and Aspergillus flavipes presented optimum activity at temperatures of 50 °C and 90 °C, respectively. Lyophilized protease from A. oryzae reached 1251.60 U/g and yield of 155010.66 U/kg of substrate. Therefore, the substrate as well as the microorganism strain can modify the biochemical character of the enzyme produced. The high protease activity and stability established plus the low cost of substrates, make these fungal proteases potential alternatives for the biotechnological industry. Copyright © 2015 Elsevier Ltd. All rights reserved.

Exploring the pH-Dependent Substrate Transport Mechanism of FocA Using Molecular Dynamics Simulation

PubMed Central

Lv, Xiaoying; Liu, Huihui; Ke, Meng; Gong, Haipeng

2013-01-01

FocA belongs to the formate-nitrate transporter family and plays an essential role in the export and uptake of formate in organisms. According to the available crystal structures, the N-terminal residues of FocA are structurally featureless at physiological conditions but at reduced pH form helices to harbor the cytoplasmic entrance of the substrate permeation pathway, which apparently explains the cessation of electrical signal observed in electrophysiological experiments. In this work, we found by structural analysis and molecular dynamics simulations that those N-terminal helices cannot effectively preclude the substrate permeation. Equilibrium simulations and thermodynamic calculations suggest that FocA is permeable to both formate and formic acid, the latter of which is transparent to electrophysiological studies as an electrically neutral species. Hence, the cease of electrical current at acidic pH may be caused by the change of the transported substrate from formate to formic acid. In addition, the mechanism of formate export at physiological pH is discussed. PMID:24359743

Sensing properties of separative paper-based extended-gate ion-sensitive field-effect transistor for cost effective pH sensor applications

NASA Astrophysics Data System (ADS)

Cho, Won-Ju; Lim, Cheol-Min

2018-02-01

In this study, we developed a cost-effective ion-sensing field-effect transistor (FET) with an extended gate (EG) fabricated on a separative paper substrate. The pH sensing characteristics of the paper EG was compared with those of other EGs fabricated on silicon, glass, or polyimide substrates. The fabricated paper-based EGFET exhibited excellent sensitivity close to the Nernst response limit as well as to that of the other substrate-based EGFETs. In addition, we found that all EGFETs, regardless of the substrate, have similar non-ideal behavior, i.e., drift phenomenon and hysteresis width. To investigate the degradation and durability of the paper EG after prolonged use, aging-effect tests were carried out in terms of the hysteresis width and sensitivity over a course of 30 days. As a result, the paper EG maintained stable pH sensing characteristics after 30 days. Therefore, we expect that paper EGFETs can provide a cost-effective sensor platform.

Performance of a completely autotrophic nitrogen removal over nitrite process for treating wastewater with different substrates at ambient temperature.

PubMed

Chang, Xiaoyan; Li, Dong; Liang, Yuhai; Yang, Zhuo; Cui, Shaoming; Liu, Tao; Zeng, Huiping; Zhang, Jie

2013-04-01

The stability and parameters of a bio-ceramic filter for completely autotrophic nitrogen removal were investigated. The completely autotrophic nitrogen removal over nitrite (CANON) reactor was fed with different concentrations of ammonia (400, 300, and 200 mg N/L) but constant influent ammonia load. The results showed that the CANON system can achieve good treatment performance at ambient temperature (15-23 degrees C). The average removal rate and removal loading of NH4(+)-N and TN was 83.90%, 1.26 kg N/(m3 x day), and 70.14%, 1.09 kg N/(m3 x day), respectively. Among the influencing factors like pH, dissolved oxygen and alkalinity, it was indicated that the pH was the key parameter of the performance of the CANON system. Observing the variation of pH would contribute to better control of the CANON system in an intuitive and fast way. Denaturing gradient gel electrophoresis analysis of microorganisms further revealed that there were some significant changes in the community structure of ammonium oxidizing bacteria, which had low diversity in different stages, while the species of anaerobic ammonium oxidizing (anammox) bacteria were fewer and the community composition was relatively stable. These observations showed that anaerobic ammonia oxidation was more stable than the aerobic ammonia oxidation, which could explain that why the CANON system maintained a good removal efficiency under the changing substrate conditions.

Phosphates (V) recovery from phosphorus mineral fertilizers industry wastewater by continuous struvite reaction crystallization process.

PubMed

Hutnik, Nina; Kozik, Anna; Mazienczuk, Agata; Piotrowski, Krzysztof; Wierzbowska, Boguslawa; Matynia, Andrzej

2013-07-01

Continuous DT MSMPR (Draft Tube Mixed Suspension Mixed Product Removal) crystallizer was provided with typical wastewater from phosphorus mineral fertilizers industry (pH < 4, 0.445 mass % of PO4(3-), inorganic impurities presence), dissolved substrates (magnesium and ammonium chlorides) and solution alkalising the environment of struvite MgNH4PO4·6H2O reaction crystallization process. Research ran in constant temperature 298 K assuming stoichiometric proportions of substrates or 20% excess of magnesium ions. Influence of pH (8.5-10) and mean residence time (900-3600 s) on product size distribution, its chemical composition, crystals shape, size-homogeneity and process kinetics was identified. Crystals of mean size ca. 25-37 μm and homogeneity CV 70-83% were produced. The largest crystals, of acceptable homogeneity, were produced using 20% excess of magnesium ions, pH 9 and mean residence time 3600 s. Under these conditions nucleation rate did not exceed 9 × 10(7) 1/(s m(3)) according to SIG (Size Independent Growth) MSMPR kinetic model. Linear crystal growth rate was 4.27 × 10(-9) m/s. Excess of magnesium ions influenced struvite reaction crystallization process yield advantageously. Concentration of phosphate(V) ions decreased from 0.445 to 9.2 × 10(-4) mass %. This can be regarded as a very good process result. In product crystals, besides main component - struvite, all impurities from wastewater were detected analytically. Copyright © 2013 Elsevier Ltd. All rights reserved.

Kinetics and thermodynamics of the interchange of the morpheein forms of human porphobilinogen synthase.

PubMed

Selwood, Trevor; Tang, Lei; Lawrence, Sarah H; Anokhina, Yana; Jaffe, Eileen K

2008-03-11

A morpheein is a homo-oligomeric protein that can adopt different nonadditive quaternary assemblies (morpheein forms) with different functionalities. The human porphobilinogen synthase (PBGS) morpheein forms are a high activity octamer, a low activity hexamer, and two structurally distinct dimer conformations. Conversion between hexamer and octamer involves dissociation to dimers, conformational change at the dimer level, followed by association to the alternate assembly. The current work promotes an alternative and novel view of the physiologically relevant dimeric structures, which are derived from the crystal structures, but are distinct from the asymmetric units of their crystal forms. Using a well characterized heteromeric system (WT+F12L; Tang, L. et al. (2005) J. Biol. Chem. 280, 15786-15793), extensive study of the human PBGS morpheein reequilibration process now reveals that the intervening dimers do not dissociate to monomers. The morpheein equilibria of wild type (WT) human PBGS are found to respond to changes in pH, PBGS concentration, and substrate turnover. Notably, the WT enzyme is predominantly an octamer at neutral pH, but increasing pH results in substantial conversion to lower order oligomers. Most significantly, the free energy of activation for the conversion of WT+F12L human PBGS heterohexamers to hetero-octamers is determined to be the same as that for the catalytic conversion of substrate to product by the octamer, remarkably suggesting a common rate-limiting step for both processes, which is postulated to be the opening/closing of the active site lid.

Post fire organic matter biodegradation in permafrost soils: Case study after experimental heating of mineral horizons.

PubMed

Masyagina, O V; Tokareva, I V; Prokushkin, A S

2016-12-15

Periodical ground fires of high frequency in permafrost forest ecosystems of Siberia (Russian Federation) are essential factors determining quantitative and qualitative parameters of permafrost soil organic matter. Specific changes in physical and chemical parameters and microbial activity of permafrost soil mineral horizons of northern taiga larch stands were revealed after heating at high temperatures (150-500°C) used for imitation of different burn intensities. Burning at 150-200°C resulted in decreasing of soil pH, whilst heating at 300-500°C caused increase of pH compare to unheated soils. Water-soluble organic carbon concentration in permafrost soils heated at 150-200°C was much higher than that of unheated soils. All these changes determined soil microbial activity in heated soils. In particular, in soils heated at 300-500°C there was momentary stimulating effect on substrate-induced respiration registered and on basal respiration values in soils burned at 150°C and 300-400°C. Four-month laboratory incubation of permafrost soils heated at different temperatures showed stimulation of microbial activity in first several days after inoculation due to high substrate availability after heating. Then soon after that soil microbial community started to be depleted on substrate because of decreasing water-soluble organic carbon, C and N content and it continued to the end of incubation. Copyright © 2016 Elsevier B.V. All rights reserved.

GLUTAMIC DECARBOXYLASE OF ERGOT, CLAVICEPS PURPUREA

PubMed Central

Anderson, John A.; Cheldelin, Vernon H.; King, Tsoo E.

1961-01-01

Anderson, John A. (Oregon State University, Corvallis), Vernon H. Cheldelin, and Tsoo E. King. Glutamic decarboxylase of ergot, Claviceps purpurea. J. Bacteriol. 82:354–358. 1961.—l-Glutamic acid is the only naturally occurring amino acid which can be decarboxylated by cell-free extracts of Claviceps purpurea. This decarboxylase was partially purified and the properties of the enzyme studied. The specific activity of the purified preparation was 111 μliters per 10 min per mg of protein. The products formed, stability, inhibition, stimulation of activity with pyridoxal phosphate, and pH activity curve were typical of l-glutamic decarboxylase in Escherichia coli and other microorganisms. The substrate constants at pH 4.6, 5.25, and 5.65 were 0.0169 m, 0.0174 m, and 0.0139 m, respectively. The respective maximal velocities at these pH values were 104, 104, and 90 μliters per 10 min. The pH optimum was 4.8 to 5.2. The enzyme was unstable below pH 4.5 and it was suggested that the fall in activity at the lower end of the pH curve was due to inactivation of the enzyme. The decrease in activity above pH 5.2 did not appear to be due to a change in affinity of enzyme for substrate but to a change of the enzyme-substrate complex into an inactive form. PMID:13683214

Gas-phase cationic benzoylation of ambient aromatic substrates studied with the decay technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Occhiucci, G.; Cacace, F.; Speranza, M.

1986-03-05

The gas-phase benzoylation of typical ambient aromatic substrates PhY (Y = OH, OMe, and NH/sub 2/) has been investigated by a combination of the decay technique and of FT ICR mass spectrometry. Labeled phenylium ions, C/sub 6/X/sub 5//sup +/ (X = H and T), from the decay of multiply tritiated benzene, C/sub 6/X/sub 6/, have been allowed to react with excess CO-containing traces of PhY (Y = OH, OMe, and NH/sub 2/), in the pressure range from 90 to 650 torr. Radio GLC and HPLC of the tritiated products demonstrate two competitive reaction channels, i.e., phenylation and benzoylation of themore » aromatic substrates. The results indicate a sharp kinetic bias of the gaseous phenylium ions for the aromatic substrates, measured by an apparent k/sub CO//k/sub PhY/ ratio of 0.12 (Y = OH), 0.13 (Y = OMe), and 0.04 (Y = NH/sub 2/) in the systems at nearly atmospheric pressure. Gas-phase benzoylation displays a high intramolecular selectivity, occurring exclusively at the n-type center of PhOH and PhNH/sub 2/. In the case of PhOMe, appreciable ring benzoylation is observed, characterized by a remarkably high (up to 30:1) bias for the para position. The mechanistic features of the gas-phase benzoylation and phenylation processes, deduced from the decay and the ICR experiments, are discussed and compared with those of related aromatic acylation and alkylation reactions occurring in the dilute gas state. 30 references, 2 tables.« less

Transient kinetic studies of pH-dependent hydrolyses by exo-type carboxypeptidase P on a 27-MHz quartz crystal microbalance.

PubMed

Furusawa, Hiroyuki; Takano, Hiroki; Okahata, Yoshio

2008-02-15

pH-Dependent kinetic parameters (k(on), k(off), and k(cat)) of protein (myoglobin) hydrolyses catalyzed by exo-enzyme (carboxypeptidase P, CPP) were obtained by using a protein-immobilized quartz crystal microbalance (QCM) in acidic aqueous solutions. The formation of the enzyme-substrate (ES) complex (k(on)), the decay of the ES complex (k(off)), and the formation of the product (k(cat)) could be analyzed by transient kinetics as mass changes on the QCM plate. The Kd (k(off)/k(on)) value was different from the Michaelis constant Km calculated from (k(off) + k(cat))/k(on) due to k(cat) > k(off). The rate-determining step was the binding step (k(on), and the catalytic rate k(cat) was faster than other k(on) and k(off) values. In the range of pH 2.5-5.0, values of k(on) gradually increased with decreasing pH showing a maximum at pH 3.7, values of k(off) were independent of pH, and k(cat) increased gradually with decreasing pH. As a result, the apparent rate constant (k(cat)/Km) showed a maximum at pH 3.7 and gradually increased with decreasing pH. The optimum pH at 3.7 of k(on) is explained by the optimum binding ability of CPP to the COOH terminus of the substrate with hydrogen bonds. The increase of k(cat) at the lower pH correlated with the decrease of alpha-helix contents of the myoglobin substrate on the QCM.

Molecular characterization of the Na+/H+-antiporter NhaA from Salmonella Typhimurium.

PubMed

Lentes, Christopher J; Mir, Syed H; Boehm, Marc; Ganea, Constanta; Fendler, Klaus; Hunte, Carola

2014-01-01

Na+/H+ antiporters are integral membrane proteins that are present in almost every cell and in every kingdom of life. They are essential for the regulation of intracellular pH-value, Na+-concentration and cell volume. These secondary active transporters exchange sodium ions against protons via an alternating access mechanism, which is not understood in full detail. Na+/H+ antiporters show distinct species-specific transport characteristics and regulatory properties that correlate with respective physiological functions. Here we present the characterization of the Na+/H+ antiporter NhaA from Salmonella enterica serovar Thyphimurium LT2, the causing agent of food-born human gastroenteritis and typhoid like infections. The recombinant antiporter was functional in vivo and in vitro. Expression of its gene complemented the Na+-sensitive phenotype of an E. coli strain that lacks the main Na+/H+ antiporters. Purified to homogeneity, the antiporter was a dimer in solution as accurately determined by size-exclusion chromatography combined with multi-angle laser-light scattering and refractive index monitoring. The purified antiporter was fully capable of electrogenic Na+(Li+)/H+-antiport when reconstituted in proteoliposomes and assayed by solid-supported membrane-based electrophysiological measurements. Transport activity was inhibited by 2-aminoperimidine. The recorded negative currents were in agreement with a 1Na+(Li+)/2H+ stoichiometry. Transport activity was low at pH 7 and up-regulation above this pH value was accompanied by a nearly 10-fold decrease of KmNa (16 mM at pH 8.5) supporting a competitive substrate binding mechanism. K+ does not affect Na+ affinity or transport of substrate cations, indicating that selectivity of the antiport arises from the substrate binding step. In contrast to homologous E. coli NhaA, transport activity remains high at pH values above 8.5. The antiporter from S. Typhimurium is a promising candidate for combined structural and functional studies to contribute to the elucidation of the mechanism of pH-dependent Na+/H+ antiporters and to provide insights in the molecular basis of species-specific growth and survival strategies.

Molecular Characterization of the Na+/H+-Antiporter NhaA from Salmonella Typhimurium

PubMed Central

Lentes, Christopher J.; Mir, Syed H.; Boehm, Marc; Ganea, Constanta; Fendler, Klaus; Hunte, Carola

2014-01-01

Na+/H+ antiporters are integral membrane proteins that are present in almost every cell and in every kingdom of life. They are essential for the regulation of intracellular pH-value, Na+-concentration and cell volume. These secondary active transporters exchange sodium ions against protons via an alternating access mechanism, which is not understood in full detail. Na+/H+ antiporters show distinct species-specific transport characteristics and regulatory properties that correlate with respective physiological functions. Here we present the characterization of the Na+/H+ antiporter NhaA from Salmonella enterica serovar Thyphimurium LT2, the causing agent of food-born human gastroenteritis and typhoid like infections. The recombinant antiporter was functional in vivo and in vitro. Expression of its gene complemented the Na+-sensitive phenotype of an E. coli strain that lacks the main Na+/H+ antiporters. Purified to homogeneity, the antiporter was a dimer in solution as accurately determined by size-exclusion chromatography combined with multi-angle laser-light scattering and refractive index monitoring. The purified antiporter was fully capable of electrogenic Na+(Li+)/H+-antiport when reconstituted in proteoliposomes and assayed by solid-supported membrane-based electrophysiological measurements. Transport activity was inhibited by 2-aminoperimidine. The recorded negative currents were in agreement with a 1Na+(Li+)/2H+ stoichiometry. Transport activity was low at pH 7 and up-regulation above this pH value was accompanied by a nearly 10-fold decrease of Km Na (16 mM at pH 8.5) supporting a competitive substrate binding mechanism. K+ does not affect Na+ affinity or transport of substrate cations, indicating that selectivity of the antiport arises from the substrate binding step. In contrast to homologous E. coli NhaA, transport activity remains high at pH values above 8.5. The antiporter from S. Typhimurium is a promising candidate for combined structural and functional studies to contribute to the elucidation of the mechanism of pH-dependent Na+/H+ antiporters and to provide insights in the molecular basis of species-specific growth and survival strategies. PMID:25010413

Accumulating the hydride state in the catalytic cycle of [FeFe]-hydrogenases

NASA Astrophysics Data System (ADS)

Winkler, Martin; Senger, Moritz; Duan, Jifu; Esselborn, Julian; Wittkamp, Florian; Hofmann, Eckhard; Apfel, Ulf-Peter; Stripp, Sven Timo; Happe, Thomas

2017-07-01

H2 turnover at the [FeFe]-hydrogenase cofactor (H-cluster) is assumed to follow a reversible heterolytic mechanism, first yielding a proton and a hydrido-species which again is double-oxidized to release another proton. Three of the four presumed catalytic intermediates (Hox, Hred/Hred and Hsred) were characterized, using various spectroscopic techniques. However, in catalytically active enzyme, the state containing the hydrido-species, which is eponymous for the proposed heterolytic mechanism, has yet only been speculated about. We use different strategies to trap and spectroscopically characterize this transient hydride state (Hhyd) for three wild-type [FeFe]-hydrogenases. Applying a novel set-up for real-time attenuated total-reflection Fourier-transform infrared spectroscopy, we monitor compositional changes in the state-specific infrared signatures of [FeFe]-hydrogenases, varying buffer pH and gas composition. We selectively enrich the equilibrium concentration of Hhyd, applying Le Chatelier's principle by simultaneously increasing substrate and product concentrations (H2/H+). Site-directed manipulation, targeting either the proton-transfer pathway or the adt ligand, significantly enhances Hhyd accumulation independent of pH.

Biohydrogen production and wastewater treatment from organic wastewater by anaerobic fermentation with UASB

NASA Astrophysics Data System (ADS)

Wang, Lu; Li, Yong-feng; Wang, Yi-xuan; Yang, Chuan-ping

2010-11-01

In order to discuss the ability of H2-production and wastewater treatment, an up-flow anaerobic sludge bed (UASB) using a synthesized substrate with brown sugar wastewater was conducted to investigate the hydrogen yield, hydrogen producing rate, fermentation type of biohydrogen production, and the chemical oxygen demand (COD) removal rate, respectively. The results show that when the biomass of inoculants was 22.5 g SSṡL-1 and the influent concentration, hydraulic retention time (HRT) and initial pH were within the ranges of 4000˜6000 mg CODṡL-1, 8 h and 5-5.5, respectively, and the biohydrogen producing reactor could work effectively. The maximum hydrogen production rate is 5.98 Lṡd-1. Simultaneously, the concentration of ethanol and acetic acid is around 80% of the aqueous terminal production in the system, which presents the typical ethanol type fermentation. pH is at the range of 4˜4.5 during the whole performing process, however, the removal rate of COD is just about 20%. Therefore, it's still needs further research to successfully achieve the biohydrogen production and wastewater treatment, simultaneously.

Tagatose production by immobilized recombinant Escherichia coli cells containing Geobacillus stearothermophilus l-arabinose isomerase mutant in a packed-bed bioreactor.

PubMed

Jung, Eun-Sook; Kim, Hye-Jung; Oh, Deok-Kun

2005-01-01

Using immobilized recombinant Escherichia coli cells containing Geobacillus stearothermophilus l-arabinose isomerase mutant (Gali 152), we found that the galactose isomerization reaction was maximal at 70 degrees C and pH 7.0. Manganese ion enhanced galactose isomerization to tagatose. The immobilized cells were most stable at 60 degrees C and pH 7.0. The cell and substrate concentrations and dilution rate were optimal at 34 g/L, 300 g/L, and 0.05 h(-1), respectively. Under the optimum conditions, the immobilized cell reactor with Mn2+ produced an average of 59 g/L tagatose with a productivity of 2.9 g/L.h and a conversion yield of 19.5% for the first 20 days. The operational stability of immobilized cells with Mn2+ was demonstrated, and their half-life for tagatose production was 34 days. Tagatose production was compared for free and immobilized enzymes and free and immobilized cells using the same mass of cells. Immobilized cells produced the highest tagatose concentration, indicating that cell immobilization was more efficient for tagatose production than enzyme immobilization.

[Study on intestinal absorption features of oligosaccharides in Morinda officinalis How. with sigle-pass perfusion].

PubMed

Deng, Shao-Dong; Zhang, Peng; Lin, Li; Xiao, Feng-Xia; Lin, Jing-Ran

2015-01-01

To study the in situ intestinal absorption of five oligosaccharides contained in Morinda officinalis How. (sucrose, kestose, nystose, 1F-Fructofuranosyinystose and Bajijiasu). The absorption of the five oligosaccharides in small intestine (duodenum, jejunum and ileum) and colon of rats and their contents were investigated by using in situ single-pass perfusion model and HPLC-ELSD. The effects of drug concentration, pH in perfusate and P-glycoprotein inhibitor on the intestinal absorption were investigated to define the intestinal absorption mechanism of the five oligosaccharides in rats. According to the results, all of the five oligosaccharides were absorbed in the whole intestine, and their absorption rates were affected by the pH of the perfusion solution, drug concentration and intestinal segments. Verapamil Hydrochloride could significantly increase the absorptive amount of sucrose and Bajijiasu, suggesting sucrose and Bajijiasu are P-gp's substrate. The five oligosaccharides are absorbed mainly through passive diffusion in the intestinal segments, without saturated absorption. They are absorbed well in all intestines and mainly in duodenum and jejunum.

Water-quality parameters and benthic algal communities at selected streams in Minnesota, August 2000 - Study design, methods and data

USGS Publications Warehouse

Lee, K.E.

2002-01-01

This report describes the study design, sampling methods, and summarizes the physical, chemical, and benthic algal data for a component of the multiagency study that was designed to document diurnal water-quality measurements (specific conductance, pH, water temperature, and dissolved oxygen), benthic algal community composition and chlorophyll-a content, and primary productivity at 12 stream sites on 6 streams in Minnesota during August 2000. Specific conductance, pH, water temperature, dissolved oxygen concentrations and percent dissolved oxygen saturation measurements were made with submersible data recorders at 30 minute intervals for a period of 3-6 days during August 2000. Benthic algae collected from wood and rock substrate were identified and enumerated. Biovolume (volume of algal cells per unit area), density (number of cells per unit area), and chlorophyll-a content from benthic algae were determined. These data can be used as part of the multiagency study to develop an understanding of the relations among nutrient concentrations, algal abundance, algal community composition, and primary production and respiration processes in rivers of differing ecoregions in Minnesota.

Potential of Immobilized Whole-Cell Methylocella tundrae as a Biocatalyst for Methanol Production from Methane.

PubMed

Mardina, Primata; Li, Jinglin; Patel, Sanjay K S; Kim, In-Won; Lee, Jung-Kul; Selvaraj, Chandrabose

2016-07-28

Methanol is a versatile compound that can be biologically synthesized from methane (CH4) by methanotrophs using a low energy-consuming and environment-friendly process. Methylocella tundrae is a type II methanotroph that can utilize CH4 as a carbon and energy source. Methanol is produced in the first step of the metabolic pathway of methanotrophs and is further oxidized into formaldehyde. Several parameters must be optimized to achieve high methanol production. In this study, we optimized the production conditions and process parameters for methanol production. The optimum incubation time, substrate, pH, agitation rate, temperature, phosphate buffer and sodium formate concentration, and cell concentration were determined to be 24 h, 50% CH4, pH 7, 150 rpm, 30°C, 100 mM and 50 mM, and 18 mg/ml, respectively. The optimization of these parameters significantly improved methanol production from 0.66 to 5.18 mM. The use of alginate-encapsulated cells resulted in enhanced methanol production stability and reusability of cells after five cycles of reuse under batch culture conditions.

Ion sensitivity of large-area epitaxial graphene film on SiC substrate

NASA Astrophysics Data System (ADS)

Mitsuno, Takanori; Taniguchi, Yoshiaki; Ohno, Yasuhide; Nagase, Masao

2017-11-01

We investigated the intrinsic ion sensitivity of graphene field-effect transistors (FETs) fabricated by a resist-free stencil mask lithography process from a large-scale graphene film epitaxially grown on a SiC substrate. A pH-adjusted phosphate-buffered solution was used for the measurement to eliminate the interference of other ions on the graphene FET's ion sensitivity. The charge neutrality point shifted negligibly with changing pH for the pH-adjusted phosphate-buffered solution, whereas for the mixed buffer solution, it shifted toward the negative gate voltage owing to the decrease in the concentration of phthalate ions. This phenomenon is contrary to that observed in previous reports. Overall, our results indicate that the graphene film is intrinsically insensitive to ions except for those with functional groups that interact with the graphene surface.

Characterization of a novel deep-sea microbial esterase EstC10 and its use in the generation of ( R)-methyl2-chloropropionate

NASA Astrophysics Data System (ADS)

Gong, Yanhui; Ma, Sanmei; Wang, Yongfei; Xu, Yongkai; Sun, Aijun; Zhang, Yun; Hu, Yunfeng

2018-03-01

A novel esterase EstC10 from Bacillus sp. CX01 isolated from the deep sea of the Western Pacific Ocean and the functionalities of EstC10 was characterized. At present, the reports about the kinetic resolution of racemic methyl 2-chloropropionate were quite rare. So we developed deep-sea microbial esterase EstC10 as a novel biocatalyst in the kinetic resolution of racemic methyl 2-chloropropionate and generate ( R)-methyl 2-chloropropionate with high enantiomeric excess (>99%) after the optimization of process parameters such as pH, temperature, organic co-solvents, surfactants, substrate concentration and reaction time. Notably, the optimal substrate concentration (80 mmol/L) of esterase EstC10 was higher than the kinetic resolution of another esterase, Est12-7 (50 mmol/L). The novel microbial esterase EstC10 identified from the deep sea was a promising green biocatalyst in the generation of ( R)-methyl 2-chloropropionate as well of many other valuable chiral chemicals in industry.

Effect of mass transfer in a recirculation batch reactor system for immobilized penicillin amidase.

PubMed

Park, J M; Choi, C Y; Seong, B L; Han, M H

1982-10-01

The effect of external mass transfer resistance on the overall reaction rate of the immobilized whole cell penicillin amidase of E. coli in a recirculation batch reactor was investigated. The internal diffusional resistance was found negligible as indicated by the value of effectiveness factor, 0.95. The local environmental change in a column due to the pH drop was successfully overcome by employing buffer solution. The reaction rate was measured by pH-stat method and was found to follow the simple Michaelis-Menten law at the initial stage of the reaction. The values of the net reaction rate experimentally determined were used to calculate the substrate concentration at the external surface of the catalyst pellet and then to calculate the mass transfer coefficient, k(L), at various flow rates and substrate concentrations. The correlation proposed by Chilton and Colburn represented adequately the experimental data. The linear change of log j(D) at low log N(Re) with negative slope was ascribed to the fact that the external mass transfer approached the state of pure diffusion in the limit of zero superficial velocity.

Valorization of kitchen biowaste for ethanol production via simultaneous saccharification and fermentation using co-cultures of the yeasts Saccharomyces cerevisiae and Pichia stipitis.

PubMed

Ntaikou, Ioanna; Menis, Nikolaos; Alexandropoulou, Maria; Antonopoulou, Georgia; Lyberatos, Gerasimos

2018-04-30

The biotransformation of the pre-dried and shredded organic fraction of kitchen waste to ethanol was investigated, via co-cultures of the yeasts Saccharomyces cerevisiae and Pichia stipitis (Scheffersomyces stipitis). Preliminary experiments with synthetic media were performed, in order to investigate the effect of different operational parameters on the ethanol production efficiency of the co-culture. The control of the pH and the supplementation with organic nitrogen were shown to be key factors for the optimization of the process. Subsequently, the ethanol production efficiency from the waste was assessed via simultaneous saccharification and fermentation experiments. Different loadings of cellulolytic enzymes and mixtures of cellulolytic with amylolytic enzymatic blends were tested in order to enhance the substrate conversion efficiency. It was further shown that for solids loading up to 40% waste on dry mass basis, corresponding to 170 g.L -1 initial concentration of carbohydrates, no substrate inhibition occurred, and ethanol concentration up to 45 g.L -1 was achieved. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effects of organic loading rate on biogas production from macroalgae: Performance and microbial community structure.

PubMed

Sun, Meng-Ting; Fan, Xiao-Lei; Zhao, Xiao-Xian; Fu, Shan-Fei; He, Shuai; Manasa, M R K; Guo, Rong-Bo

2017-07-01

Macroalgae biomass has been considered as a promising feedstock for biogas production. In order to improve the efficiency of anaerobic digestion (AD) of macroalgae, semi-continuous fermentation was conducted to examine the effects of organic loading rate (OLR) on biogas production from Macrocystis pyrifer. Results showed that, under OLRs of 1.37, 2.74, 4.12 and 6.85kgVS substrate /(m 3 ·d), the average unit biogas yields were 438.9, 477.3, 480.1 and 188.7mL/(gVS substrate d), respectively. It indicated that biogas production was promoted by the increased OLR in an appropriate range while inhibited by the OLR beyond the appropriate range. The investigation on physical-chemical parameters revealed that unfavorable VFAs concentration, pH and salinity might be the main causes for system failure due to the overrange OLR, while the total phenols failed to reach the inhibitory concentration. Microbial community analysis demonstrated that several bacterial and archaeal phyla altered with increase in OLR apparently. Copyright © 2017 Elsevier Ltd. All rights reserved.

Enzymatic hydrolysis of 1-monoacyl-SN-glycerol-3-phosphoryl-choline (1-lysolecithin) by phospholipases from peanut seeds.

PubMed

Strauss, H; Leibovitz-Ben Gershon, Z; Heller, M

1976-06-01

Hydrolysis of 1-lysolecithin (1-acyl glycerophosphorylcholine [1-acyl GPC]) by preparations of phospholipase D from peanut seeds was investigated. 1-Lysolecithin was hydrolyzed at a much slower rate than phosphatidylcholine (lecithin). Although Ca+2 ions are required for the cleavage of lecithin by the enzyme, their effect on the hydrolysis of lysolecithin depended upon the concentration of the substrate: at 0.2 mM 1-lysolecithin, Ca+2 ions increased the reaction rates, whereas at concentrations of the substrate lower than 0.1 mM, Ca+2 ions were inhibitory. A broad pH activity curve between 5 and 8 was obtained with higher rates in the alkaline range, both in the absence and presence of Ca+2 ions. The increased hydrolysis of lysolecithin due to Ca+2 was noticed over the entire pH range. Upon storage of the enzyme solutions at 4 C, decreased rates of hydrolysis of lecithin were observed, with t 1/2 values of ca. 50 and 100 days depending on the purity of the preparation. During the same period, no reduction occurred in the activity of these preparations on lysolecithin as substrate. The effects of Ca+2 ions and the analysis of the products of 1-acyl GPC cleavage by the enzyme preparations revealed the presence of more than one enzyme and the formation of the following compounds: lysophosphatidic acids (1 acyl glycerophosphoric acids), free fatty acids, glycerophosphorylcholine, and choline. The possible pathways leading to the degradation of lysolecithin and the formation of these products include reactions catalyzed by lysophospholipase A1 (lysophosphatidylcholine 1-acyl hydrolase, E.C. 3.1.1.5) and a phosphodiesterase (L-3-glycerylphosphorylcholine glycerophosphohydrolase, E.C.3.1.4.2), in addition to phospholipase D (phosphatidyl-choline phosphatidohydrolase, E.C. 3.1.4.4).

Substrate specificity of human metallocarboxypeptidase D: Comparison of the two active carboxypeptidase domains

PubMed Central

Tanco, Sebastian; Díaz, Lucía; Dasgupta, Sayani; Fernandez-Recio, Juan; Lorenzo, Julia; Aviles, Francesc X.; Fricker, Lloyd D.

2017-01-01

Metallocarboxypeptidase D (CPD) is a membrane-bound component of the trans-Golgi network that cycles to the cell surface through exocytic and endocytic pathways. Unlike other members of the metallocarboxypeptidase family, CPD is a multicatalytic enzyme with three carboxypeptidase-like domains, although only the first two domains are predicted to be enzymatically active. To investigate the enzymatic properties of each domain in human CPD, a critical active site Glu in domain I and/or II was mutated to Gln and the protein expressed, purified, and assayed with a wide variety of peptide substrates. CPD with all three domains intact displays >50% activity from pH 5.0 to 7.5 with a maximum at pH 6.5, as does CPD with mutation of domain I. In contrast, the domain II mutant displayed >50% activity from pH 6.5–7.5. CPD with mutations in both domains I and II was completely inactive towards all substrates and at all pH values. A quantitative peptidomics approach was used to compare the activities of CPD domains I and II towards a large number of peptides. CPD cleaved C-terminal Lys or Arg from a subset of the peptides. Most of the identified substrates of domain I contained C-terminal Arg, whereas comparable numbers of Lys- and Arg-containing peptides were substrates of domain II. We also report that some peptides with C-terminal basic residues were not cleaved by either domain I or II, showing the importance of the P1 position for CPD activity. Finally, the preference of domain I for C-terminal Arg was validated through molecular docking experiments. Together with the differences in pH optima, the different substrate specificities of CPD domains I and II allow the enzyme to perform distinct functions in the various locations within the cell. PMID:29131831

Chemical modification and pH dependence of kinetic parameters to identify functional groups in a glucosyltransferase from Strep. Mutans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bell, J.E.; Leone, A.; Bell, E.T.

1986-05-01

A glucosyltransferase, forming a predominantly al-6 linked glucan, was partially purified from the culture filtrate of S. mutans GS-5. The kinetic properties of the enzyme, assessed using the transfer of /sup 14/C glucose from sucrose into total glucan, were studied at pH values from pH 3.5 to 6.5. From the dependence of km on pH, a group with pKa = 5.5 must be protonated to maximize substrate binding. From plots of V/sub max/ vs pH two groups, with pKa's of 4.5 and 5.5 were indicated. The results suggest the involvement of either two carboxyl groups (one protonated, one unprotonated inmore » the native enzyme) or a carboxyl group (unprotonated) and some other protonated group such as histidine, cysteine. Chemical modification studies showed that Diethylyrocarbonate (histidine specific) had no effect on enzyme activity while modification with p-phydroxy-mercuribenzoate or iodoacetic acid (sulfhydryl reactive) and carbodimide reagents (carboxyl specific) resulted in almost complete inactivation. Activity loss was dependent upon time of incubation and reagent concentration. The disaccharide lylose, (shown to be an inhibitor of the enzyme with similar affinity to sucrose) offers no protection against modification by the sulfhydryl reactive reagents.« less

Oxidase-functionalized Fe(3)O(4) nanoparticles for fluorescence sensing of specific substrate.

PubMed

Liu, Cheng-Hao; Tseng, Wei-Lung

2011-10-03

This study reports the development of a reusable, single-step system for the detection of specific substrates using oxidase-functionalized Fe(3)O(4) nanoparticles (NPs) as a bienzyme system and using amplex ultrared (AU) as a fluorogenic substrate. In the presence of H(2)O(2), the reaction pH between Fe(3)O(4) NPs and AU was similar to the reaction of oxidase and the substrate. The catalytic activity of Fe(3)O(4) NPs with AU was nearly unchanged following modification with poly(diallyldimethylammonium chloride) (PDDA). Based on these features, we prepared a composite of PDDA-modified Fe(3)O(4) NPs and oxidase for the quantification of specific substrates through the H(2)O(2)-mediated oxidation of AU. By monitoring fluorescence intensity at 587 nm of oxidized AU, the minimum detectable concentrations of glucose, galactose, and choline were found to be 3, 2, and 20 μM using glucose oxidase-Fe(3)O(4), galactose oxidase-Fe(3)O(4), and choline oxidase-Fe(3)O(4) composites, respectively. The identification of glucose in blood was selected as the model to validate the applicability of this proposed method. Copyright © 2011 Elsevier B.V. All rights reserved.

Stretchable, wireless sensors and functional substrates for epidermal characterization of sweat.

PubMed

Huang, Xian; Liu, Yuhao; Chen, Kaile; Shin, Woo-Jung; Lu, Ching-Jui; Kong, Gil-Woo; Patnaik, Dwipayan; Lee, Sang-Heon; Cortes, Jonathan Fajardo; Rogers, John A

2014-08-13

This paper introduces materials and architectures for ultrathin, stretchable wireless sensors that mount on functional elastomeric substrates for epidermal analysis of biofluids. Measurement of the volume and chemical properties of sweat via dielectric detection and colorimetry demonstrates some capabilities. Here, inductively coupled sensors consisting of LC resonators with capacitive electrodes show systematic responses to sweat collected in microporous substrates. Interrogation occurs through external coils placed in physical proximity to the devices. The substrates allow spontaneous sweat collection through capillary forces, without the need for complex microfluidic handling systems. Furthermore, colorimetric measurement modes are possible in the same system by introducing indicator compounds into the depths of the substrates, for sensing specific components (OH(-) , H(+) , Cu(+) , and Fe(2+) ) in the sweat. The complete devices offer Young's moduli that are similar to skin, thus allowing highly effective and reliable skin integration without external fixtures. Experimental results demonstrate volumetric measurement of sweat with an accuracy of 0.06 μL/mm(2) with good stability and low drift. Colorimetric responses to pH and concentrations of various ions provide capabilities relevant to analysis of sweat. Similar materials and device designs can be used in monitoring other body fluids. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nickel-Aluminum Layered Double Hydroxide Coating on the Surface of Conductive Substrates by Liquid Phase Deposition.

PubMed

Maki, Hideshi; Takigawa, Masashi; Mizuhata, Minoru

2015-08-12

The direct synthesis of the adhered Ni-Al LDH thin film onto the surface of electrically conductive substrates by the liquid phase deposition (LPD) reaction is carried out for the development of the positive electrode. The complexation and solution equilibria of the dissolved species in the LPD reaction have been clarified by a theoretical approach, and the LPD reaction conditions for the Ni-Al LDH depositions are shown to be optimized by controlling the fluoride ion concentration and the pH of the LPD reaction solutions. The yields of metal oxides and hydroxides by the LPD method are very sensitive to the supersaturation state of the hydroxide in the reaction solution. The surfaces of conductive substrates are completely covered by the minute mesh-like Ni-Al LDH thin film; furthermore, there is no gap between the surfaces of conductive substrates and the deposited Ni-Al LDH thin film. The active material layer thickness was able to be controlled within the range from 100 nm to 1 μm by the LPD reaction time. The high-crystallinity and the arbitrary-thickness thin films on the conductive substrate surface will be beneficial for the interface control of charge transfer reaction fields and the internal resistance reduction of various secondary batteries.

Surface-enhanced infrared spectroscopic studies of the catalytic behavior of silver nanoparticles on a germanium substrate.

PubMed

Liou, Yen-Chen Maggie; Yang, Jyisy; Fasasi, Ayuba; Griffiths, Peter R

2011-05-01

The catalytic activity of silver nanoparticles (AgNPs) on a germanium substrate is reported. Para-nitrothiophenol (pNTP) that had been adsorbed on this substrate is converted to p-aminothiophenol (pATP) under very mild reaction conditions, such as simply soaking in water. The AgNPs may be formed either by physical vapor deposition or by electroless deposition from a solution of silver nitrate. Analogous reactions were not observed on copper nanoparticles on germanium or AgNPs on silicon or zinc selenide even though very slow conversion of pNTP to pATP was observed with Au nanoparticles (AuNPs) on Ge under controlled reaction conditions. The effects of factors that could influence the catalytic reaction were examined; these included the particle size of the AgNPs, reaction temperature, concentration and chemical nature of other ions present in the solution, the pH of the water, and the nature of the substrate. The reaction rate was approximately independent of the particle size for AgNPs between 50 and 150 nm in diameter. Increasing the temperature accelerates the reaction significantly; at temperatures above 40 °C, the adsorbed pNTP is completely converted by water within five minutes. Not surprisingly, the reaction rate was increased as the pH of the solution was decreased, as the reduction of each nitro group to an amino group requires six protons. The presence of Br(-) and I(-) ions accelerated the reaction to the point that even at 4 °C, the conversion of the nitro group was still observable, while solutions containing chloride ions had to be heated to 40 °C before their effect became apparent. Apparently, Br(-) and I(-) ions remove the oxide layer from the surface of the germanium substrate, facilitating transfer of electrons from the germanium to the nitro group of the pNTP.

ABCG2/BCRP decreases the transfer of a food-born chemical carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in perfused term human placenta.

PubMed

Myllynen, Päivi; Kummu, Maria; Kangas, Tiina; Ilves, Mika; Immonen, Elina; Rysä, Jaana; Pirilä, Rauna; Lastumäki, Anni; Vähäkangas, Kirsi H

2008-10-15

We have studied the role of ATP binding cassette (ABC) transporters in fetal exposure to carcinogens using 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) a known substrate for ABC transporters as a model compound. In perfusion of human term placenta, transfer of (14)C-PhIP (2 microM) through the placenta resulted in fetal-to-maternal concentration ratio (FM ratio) of 0.72+/-0.09 at 6 h. The specific ABCG2 inhibitor KO143 increased the transfer of (14)C-PhIP from maternal to fetal circulation (FM ratio 0.90+/-0.08 at 6 h, p<0.05) while the ABCC1/ABCC2 inhibitor probenecid had no effect (FM ratio at 6 h 0.75+/-0.10, p=0.84). There was a negative correlation between the expression of ABCG2 protein in perfused tissue and the FM ratio of (14)C-PhIP (R=-0.81, p<0.01) at the end of the perfusion. The expression of ABCC2 protein did not correlate with FM ratio of PhIP (R: -0.11, p=0.76). In addition, PhIP induced the expression of ABC transporters in BeWo cells at mRNA level. In conclusion, our data indicates that ABCG2 decreases placental transfer of (14)C-PhIP in perfused human placenta. Also, PhIP may modify ABC transporter expression in choriocarcinoma cells.

ABCG2/BCRP decreases the transfer of a food-born chemical carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in perfused term human placenta

DOE Office of Scientific and Technical Information (OSTI.GOV)

Myllynen, Paeivi; Kummu, Maria; Kangas, Tiina

2008-10-15

We have studied the role of ATP binding cassette (ABC) transporters in fetal exposure to carcinogens using 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) a known substrate for ABC transporters as a model compound. In perfusion of human term placenta, transfer of {sup 14}C-PhIP (2 {mu}M) through the placenta resulted in fetal-to-maternal concentration ratio (FM ratio) of 0.72 {+-} 0.09 at 6 h. The specific ABCG2 inhibitor KO143 increased the transfer of {sup 14}C-PhIP from maternal to fetal circulation (FM ratio 0.90 {+-} 0.08 at 6 h, p < 0.05) while the ABCC1/ABCC2 inhibitor probenecid had no effect (FM ratio at 6 h 0.75 {+-}more » 0.10, p = 0.84). There was a negative correlation between the expression of ABCG2 protein in perfused tissue and the FM ratio of {sup 14}C-PhIP (R = - 0.81, p < 0.01) at the end of the perfusion. The expression of ABCC2 protein did not correlate with FM ratio of PhIP (R: - 0.11, p = 0.76). In addition, PhIP induced the expression of ABC transporters in BeWo cells at mRNA level. In conclusion, our data indicates that ABCG2 decreases placental transfer of {sup 14}C-PhIP in perfused human placenta. Also, PhIP may modify ABC transporter expression in choriocarinoma cells.« less

Alkaline fermentation of waste activated sludge stimulated by saponin: volatile fatty acid production, mechanisms and pilot-scale application.

PubMed

Huang, Xiangfeng; Mu, Tianshuai; Shen, Changming; Lu, Lijun; Liu, Jia

2016-12-01

Volatile fatty acid (VFA) production stimulated by saponin (SP), an environmentally friendly bio-surfactant, was investigated during sludge alkaline fermentation in laboratory studies and pilot applications. The combined use of SP and pH 9 condition significantly enhanced VFA production to approximately 425 mg COD/g VSS, which was 4.7-fold of raw sludge and 1.5-fold of sole pH 10 adjustment (the optimum pH for alkaline fermentation). Further results indicated that SP & pH 9 condition provided sufficient substrates for acidification and decreased the consumption of VFAs through methanogenesis. Moreover, SP accompanied by moderate alkaline condition (i.e. pH 9) showed weaker inhibitory effects on key enzyme activities and metabolic potential of acidification microorganisms than sole pH 10 adjustment. On this basis, a pilot-scale system involving anaerobic fermentation and anaerobic-anoxic-aerobic step-feed bioreaction tanks was established to study the potential of VFAs as supplementary carbon sources for wastewater treatment. The influent of the pilot system was sanitary wastewater characterized by low C/N ratios from a scenic rural area. After flocculation and nutrient precipitation, the fermentation supernatant was mixed with the influent at a volume ratio of 1:30. With this approach, nitrogen and phosphorus concentrations in effluent fulfilled the first-A wastewater discharge standard in China.

Cloning and expression of cyclodextrin glycosyltransferase gene from Paenibacillus sp. T16 isolated from hot spring soil in northern Thailand.

PubMed

Charoensakdi, Ratiya; Murakami, Shuichiro; Aoki, Kenji; Rimphanitchayakit, Vichien; Limpaseni, Tipaporn

2007-05-31

Gene encoding cyclodextrin glycosyltransferase (CGTase), from thermotolerant Paenibacillus sp. T16 isolated from hot spring area in northern Thailand, was cloned and expressed in E. coli (JM109). The nucleotide sequences of both wild type and transformed CGTases consisted of 2139 bp open reading frame, 713 deduced amino acids residues with difference of 4 amino acid residues. The recombinant cells required 24 h culture time and a neutral pH for culture medium to produce compatible amount of CGTase compared to 72 h culture time and pH 10 for wild type. The recombinant and wild-type CGTases were purified by starch adsorption and phenyl sepharose column chromatography and characterized in parallel. Both enzymes showed molecular weight of 77 kDa and similar optimum pHs and temperatures with recombinant enzyme showing broader range. There were some significant difference in pH, temperature stability and kinetic parameters. The presence of high starch concentration resulted in higher thermostability in recombinant enzyme than the wild type. The recombinant enzyme was more stable at higher temperature and lower pH, with lower K(m) for coupling reaction using cellobiose and cyclodextrins as substrates.

Optimization of buffer injection for the effective bioremediation of chlorinated solvents in aquifers

NASA Astrophysics Data System (ADS)

Brovelli, A.; Robinson, C.; Barry, A.; Kouznetsova, I.; Gerhard, J.

2008-12-01

Various techniques have been proposed to enhance biologically-mediated reductive dechlorination of chlorinated solvents in the subsurface, including the addition of fermentable organic substrate for the generation of H2 as an electron donor. One rate-limiting factor for enhanced dechlorination is the pore fluid pH. Organic acids and H+ ions accumulate in dechlorination zones, generating unfavorable conditions for microbial activity (pH < 6.5). The pH variation is a nonlinear function of the amount of reduced chlorinated solvents, and is affected by the organic material fermented, the chemical composition of the pore fluid and the soil's buffering capacity. Consequently, in some cases enhanced remediation schemes rely on buffer injection (e.g., bicarbonate) to alleviate this problem, particularly in the presence of solvent nonaqueous phase liquid (NAPL) source zones. However, the amount of buffer required - particularly in complex, evolving biogeochemical environments - is not well understood. To investigate this question, this work builds upon a geochemical numerical model (Robinson et al., Science of the Total Environment, submitted), which computes the amount of additional buffer required to maintain the pH at a level suitable for bacterial activity for batch systems. The batch model was coupled to a groundwater flow/solute transport/chemical reaction simulator to permit buffer optimization computations within the context of flowing systems exhibiting heterogeneous hydraulic, physical and chemical properties. A suite of simulations was conducted in which buffer optimization was examined within the bounds of the minimum concentration necessary to sustain a pH favorable to microbial activity and the maximum concentration to avoid excessively high pH values (also not suitable to bacterial activity) and mineral precipitation (e.g., calcite, which may lead to pore-clogging). These simulations include an examination of the sensitivity of this buffer concentration range to aquifer heterogeneity and groundwater velocity. This work is part of SABRE (Source Area BioREmediation), a collaborative international research project that aims to evaluate and improve enhanced bioremediation of chlorinated solvent source zones. In this context, numerical simulations are supporting the upscaling of the technique, including identifying the most appropriate buffer injection strategies for field applications

Immobilization of glucose oxidase to nanostructured films of polystyrene-block-poly(2-vinylpyridine).

PubMed

Bhakta, Samir A; Benavidez, Tomas E; Garcia, Carlos D

2014-09-15

A critical step for the development of biosensors is the immobilization of the biorecognition element to the surface of a substrate. Among other materials that can be used as substrates, block copolymers have the untapped potential to provide significant advantages for the immobilization of proteins. To explore such possibility, this manuscript describes the fabrication and characterization of thin-films of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP). These films were then used to investigate the immobilization of glucose oxidase, a model enzyme for the development of biosensors. According to the results presented, the nanoporous films can provide significant increases in surface area of the substrate and the immobilization of larger amounts of active enzyme. The characterization of the substrate-enzyme interface discussed in the manuscript aims to provide critical information about relationship between the surface (material, geometry, and density of pores), the protein structure, and the immobilization conditions (pH, and protein concentration) required to improve the catalytic activity and stability of the enzymes. A maximum normalized activity of 3300±700 U m(-2) was achieved for the nanoporous film of PS-b-P2VP. Copyright © 2014 Elsevier Inc. All rights reserved.

Immobilization of Glucose Oxidase to Nanostructured Films of Polystyrene-block-poly(2-vinylpyridine)

PubMed Central

Bhakta, Samir A; Benavidez, Tomas E; Garcia, Carlos D

2014-01-01

A critical step for the development of biosensors is the immobilization of the biorecognition element to the surface of a substrate. Among other materials that can be used as substrates, block copolymers have the untapped potential to provide significant advantages for the immobilization of proteins. To explore such possibility, this manuscript describes the fabrication and characterization of thin-films of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP). These films were then used to investigate the immobilization of glucose oxidase, a model enzyme for the development of biosensors. According to the results presented, the nanoporous films can provide significant increases in surface area of the substrate and the immobilization of larger amounts of active enzyme. The characterization of the substrate-enzyme interface discussed in the manuscript aims to provide critical information about relationship between the surface (material, geometry, and density of pores), the protein structure, and the immobilization conditions (pH, ionic strength, and protein concentration) required to improve the catalytic activity and stability of the enzymes. A maximum normalized activity of 3300 ± 700 U m−2 was achieved for the nanoporous film of PS-b-P2VP. PMID:24980481

Optical and structural properties in type-II InAlAs/AlGaAs quantum dots observed by photoluminescence, X-ray diffraction and transmission electron microscopy

NASA Astrophysics Data System (ADS)

Ben Daly, A.; Craciun, D.; Laura Ursu, E.; Lemaître, A.; Maaref, M. A.; Iacomi, F.; Vasile, B. S.; Craciun, V.

2017-10-01

We present the effects of AlGaAs alloy composition on InAlAs quantum dots (QDs) optical and structural properties. Photoluminescence (PL) analysis of samples having a variety of aluminium composition values covering type-II transitions clearly in QDs showed the presence of two transitions X-Sh and X-Ph. High-resolution X-ray diffraction (HRXRD) investigations showed that the layers grew epitaxially on the GaAs substrate, with no relaxation regardless the Al content of AlGaAs layer. From the reciprocal space map (RSM) investigation around (004) and (115) diffraction peaks, it was shown that the InAlAs layer is fully strained, the in-plane lattice parameters (a and b, a = b) being identical to those of GaAs substrate, while the c lattice parameter was dependent on the In and Al concentrations, being larger than that of the substrate. High-resolution transmission electronic microscopy (HRTEM) investigations confirmed that films grew epitaxially on the GaAs substrate with no visible dislocations or other major defects within the InAlAs/GaAlAs QDs structure.

Preparation by site-directed mutagenesis and characterization of the E211Q mutant of yeast enolase 1.

PubMed

Sangadala, V S; Glover, C V; Robson, R L; Holland, M J; Lebioda, L; Brewer, J M

1995-08-16

The published 'charge shuttle' mechanism of enolase (Lebioda, L. and Stec, B. (1991) Biochemistry 30, 2817-2822) assigns Glu-211 the task of orienting a water molecule that serves as the catalytic base which removes the proton from carbon-2 of the substrate. We prepared the E211Q mutant of yeast enolase 1 by site-directed mutagenesis. It appears to be folded correctly and to respond similarly to many of the normal ligands of enolase: it is stabilized against thermal denaturation by conformational Mg2+ and by Mg2+ and substrate and binds the chromophoric substrate analogue D-tartronate semialdehyde-2-phosphate (TSP) with affinity comparable to that of the native enzyme. However, it has only 0.01% (10(-4)) of the activity of native enolase under standard assay conditions and does not exhibit significantly more activity at various pH values or higher concentrations of substrate and Mg2+. Its ability to produce the form of enzyme-bound and reacted TSP that absorbs at shorter wavelengths is greatly slowed, while the longer wavelength absorbing form is produced rapidly. Overall, these observations are consistent with the hypothetical mechanism.

Isolation and characterization of a novel 2-methyl-4-chlorophenoxyacetic acid-degrading Enterobacter sp. strain SE08.

PubMed

Tan, Lin; Hu, Qiulong; Xiong, Xingyao; Su, Xiaojun; Huang, Yanning; Jiang, Ziwei; Zhou, Qingming; Zhao, Songyi; Zeng, Wei-ai

2013-10-01

A bacterial strain (SE08) capable of utilizing 2-methyl-4-chlorophenoxy acetic acid (MCPA) as the sole carbon and energy source for growth was isolated by continuous enrichment culturing in minimal salt medium (MSM) from a long term MCPA exposed soil. This bacterial strain was identified as Enterobacter sp. based on morphological, physiological and biochemical tests, as well as 16S rRNA sequence analysis. Its ability to degrade MCPA was determined using high performance liquid chromatography. The strain SE08 can tolerate unusually high MCPA concentrations (125-2000mg/L). The influences of culturing factors (initial concentration, pH, and temperature) on the bacterial growth and substrate degradation were studied. The results showed that the optimal MCPA degradation occurred at an MCPA concentration of 500mg/L, 30°C and pH 6.0. Under these conditions, 68.5 percent of MCPA in MSM was degraded by SE08, and the OD600nm reached 0.64 after culturing for 72h. The degradation of MCPA could be enhanced by addition of both carbon and nitrogen sources. At an initial MCPA concentration of 500mg/L, when 5g/L glucose and 2.5g/L yeast extract were added into the MSM media, the MCPA degradation was significantly increased to 83.8 percent, and OD600nm was increased to 1.09 after incubation at 30°C and pH 6.0 for 72h. This is the first study showing that an Enterobacter sp. strain is capable of degrading MCPA, which might provide a new approach for the remediation of MCPA contaminated soil and contribute to the limited knowledge about the function of Enterobacter species. Crown Copyright © 2013. Published by Elsevier Inc. All rights reserved.

Effects of halophilic peptide fusion on solubility, stability, and catalytic performance of D-phenylglycine aminotransferase.

PubMed

Javid, Hossein; Jomrit, Juntratip; Chantarasiri, Aiya; Isarangkul, Duangnate; Meevootisom, Vithaya; Wiyakrutta, Suthep

2014-05-01

D-Phenylglycine aminotransferase (D-PhgAT) from Pseudomonas stutzeri ST-201 is useful for enzymatic synthesis of enantiomerically pure D-phenylglycine. However, its low protein solubility prevents its application at high substrate concentration. With an aim to increase the protein solubility, the N-terminus of D-PhgAT was genetically fused with short peptides (A1 α- helix, A2 α-helix, and ALAL, which is a hybrid of A1 and A2) from a ferredoxin enzyme of a halophilic archaeon, Halobacterium salinarum. The fused enzymes A1-D-PhgAT, A2-D-PhgAT, and ALAL-D-PhgAT displayed a reduced pI and increased in solubility by 6.1-, 5.3-, and 8.1- fold in TEMP (pH 7.6) storage, respectively, and 5-, 4.5-, and 5.9-fold in CAPSO (pH 9.5) reaction buffers, respectively, compared with the wild-type enzyme (WT-D-PhgAT). In addition, all the fused D-PhgAT displayed higher enzymatic reaction rates than the WT-DPhgAT at all concentrations of L-glutamate monosodium salt used. The highest rate, 23.82 ± 1.47 mM/h, was that obtained from having ALAL-D-PhgAT reacted with 1,500 mM of the substrate. Moreover, the halophilic fusion significantly increased the tolerance of D-PhgAT in the presence of NaCl and KCl, being slightly in favor of KCl, where under the same condition at 3.5 M NaCl or KCl all halophilic-fused variants showed higher activity than WT-D-PhgAT.

An organic solvent-stable lipase from a newly isolated Staphylococcus aureus ALA1 strain with potential for use as an industrial biocatalyst.

PubMed

Ben Bacha, Abir; Moubayed, Nadine Ms; Al-Assaf, Alaa

2016-05-01

In this study, a new strain, ALA1, was identified as Staphylococcus aureus by biochemical tests, and its 16S ribosomal DNA sequence was isolated from dromedary milk. ALA1 lipase production was optimized in shake flask experiments and measured with varying pH (3-11), temperature (20-55 °C) and substrate concentrations. The maximum lipase production was recorded at pH 8 and 30 °C for up to 30 H of culture period for the S. aureus ALA1 strain. Among the substrates tested, selected carbon sources, xylose, nitrogen source, yeast extract, and olive oil (1%) were suitable for maximizing lipase production. The effects of surfactants were investigated and showed that Tween 20, Tween 80, and Triton X-100 prevented lipase production. Interestingly, isolate ALA1 was able to grow in high concentrations of benzene or toluene (up to 50% (v/v)). Moreover, the lipolytic activity of the S. aureus ALA1 lipase was stimulated by diethyl ether, whereas almost 100% of S. aureus ALA1 lipase activity was retained in 25% acetone, acetonitrile, benzene, 2-propanol, ethanol, methanol, or toluene. Because of its stability in organic solvent, the S. aureus ALA1 lipase was used as a biocatalyst to synthesize high levels of added value molecules. S. aureus ALA1 lipase could be considered as an ideal choice for applications in detergent formulations because of its high stability and compatibility with various surfactants, oxidizing agents, and commercial detergents. © 2015 International Union of Biochemistry and Molecular Biology, Inc.

Citric acid production by Koji fermentation using banana peel as a novel substrate.

PubMed

Karthikeyan, Alagarsamy; Sivakumar, Nallusamy

2010-07-01

The growing demand for citric acid and the current need for alternative sources have encouraged biotechnologists to search for novel and economical substrates. Koji fermentation was conducted using the peels of banana (Musa acuminata) as an inexpensive substrate for the production of citric acid using Aspergillus niger. Various crucial parameters that affect citric acid production such as moisture content, temperature, pH, inoculum level and incubation time were quantified. Moisture (70%), 28 degrees C temperature, an initial pH 3, 10(8) spores/ml as inoculum and 72h incubation was found to be suitable for maximum citric acid production by A. niger using banana peel as a substrate. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Steel slag affects pH and Si content of container substrates

USDA-ARS?s Scientific Manuscript database

A substrate representing a typical greenhouse potting mix was prepared using 85% sphagnum peat and 15% perlite. The substrate was filled into 10 cm wide containers. A pulverized steel slag (SS) from a basic oxygen furnace, and dolomitic limestone (DL) were amended to the base substrate at a rate o...

Simultaneous saccharification and fermentation of acid-pretreated rapeseed meal for succinic acid production using Actinobacillus succinogenes.

PubMed

Chen, Kequan; Zhang, Han; Miao, Yelian; Wei, Ping; Chen, Jieyu

2011-04-07

Rapeseed meal was evaluated for succinic acid production by simultaneous saccharification and fermentation using Actinobacillus succinogenes ATCC 55618. Diluted sulfuric acid pretreatment and subsequent hydrolysis with pectinase was used to release sugars from rapeseed meal. The effects of culture pH, pectinase loading and yeast extract concentration on succinic acid production were investigated. When simultaneous saccharification and fermentation of diluted acid pretreated rapeseed meal with a dry matter content of 12.5% (w/v) was performed at pH 6.4 and a pectinase loading of 2% (w/w, on dry matter) without supplementation of yeast extract, a succinic acid concentration of 15.5 g/L was obtained at a yield of 12.4 g/100g dry matter. Fed-batch simultaneous saccharification and fermentation was carried out with supplementation of concentrated pretreated rapeseed meal and pectinase at 18 and 28 h to yield a final dry matter content of 20.5% and pectinase loading of 2%, with the succinic acid concentration enhanced to 23.4 g/L at a yield of 11.5 g/100g dry matter and a productivity of 0.33 g/(Lh). This study suggests that rapeseed meal may be an alternative substrate for the efficient production of succinic acid by A. succinogenes without requiring nitrogen source supplementation. Copyright © 2011 Elsevier Inc. All rights reserved.

Substrate specificity of sheep liver sorbitol dehydrogenase.

PubMed Central

Lindstad, R I; Köll, P; McKinley-McKee, J S

1998-01-01

The substrate specificity of sheep liver sorbitol dehydrogenase has been studied by steady-state kinetics over the range pH 7-10. Sorbitol dehydrogenase stereo-selectively catalyses the reversible NAD-linked oxidation of various polyols and other secondary alcohols into their corresponding ketones. The kinetic constants are given for various novel polyol substrates, including L-glucitol, L-mannitol, L-altritol, D-altritol, D-iditol and eight heptitols, as well as for many aliphatic and aromatic alcohols. The maximum velocities (kcat) and the substrate specificity-constants (kcat/Km) are positively correlated with increasing pH. The enzyme-catalysed reactions occur by a compulsory ordered kinetic mechanism with the coenzyme as the first, or leading, substrate. With many substrates, the rate-limiting step for the overall reaction is the enzyme-NADH product dissociation. However, with several substrates there is a transition to a mechanism with partial rate-limitation at the ternary complex level, especially at low pH. The kinetic data enable the elucidation of new empirical rules for the substrate specificity of sorbitol dehydrogenase. The specificity-constants for polyol oxidation vary as a function of substrate configuration with D-xylo> D-ribo > L-xylo > D-lyxo approximately L-arabino > D-arabino > L-lyxo. Catalytic activity with a polyol or an aromatic substrate and various 1-deoxy derivatives thereof varies with -CH2OH > -CH2NH2 > -CH2OCH3 approximately -CH3. The presence of a hydroxyl group at each of the remaining chiral centres of a polyol, apart from the reactive C2, is also nonessential for productive ternary complex formation and catalysis. A predominantly nonpolar enzymic epitope appears to constitute an important structural determinant for the substrate specificity of sorbitol dehydrogenase. The existence of two distinct substrate binding regions in the enzyme active site, along with that of the catalytic zinc, is suggested to account for the lack of stereospecificity at C2 in some polyols. PMID:9461546

Partial purification and kinetic characterization of acid phosphatase from garlic seedling.

PubMed

Yenigün, Begüm; Güvenilir, Yüksel

2003-01-01

The objective of this study was to obtain purer acid phosphatases than produced by prior art by operating under conditions that improve the final product. The study features are the use of a mild nonionic detergent, 40-80% saturation with (NH4)2SOm4, maintained at low temperature to remove impurity, and the use of chromatografic columns to concentrate the acid phosphatase and remove non-acid phosphatase proteins with lower or higher molecular weights. Acid phosphatase was isolated and purified from garlic seedlings by a streamline method without the use of proteolytic and lipolytic enzymes, butanol, or other organic solvents. Grown garlic seedlings of 10- 15 cm height were homogenized with 0.1 M acetate buffer containing 0.1 M NaCl and 0.1% Triton X-100. After homogenization, the supernatant was filtered with paper filters. Filtrated supernatant was cooled to 4 degrees C, followed by a threestep fractionation of the proteins with ammonium sulfate. The crude enzyme was isolated as a green precipitate that was dissolved in a small amount of 0.1 M acetate buffer containing 0.1 M NaCl and 0.1% Triton X-100. Garlic seedling acid phosphatase was purified with ion-exchange chromatography (DEAE cellulose). The column was equilibrated with 0.1 M acetate buffer. Acid phosphatase was purified 40-fold from the starting material. The specific activity of the pure enzyme was 168 U/mg. A variety of stability and activity profiles were determined for the purified garlic seedling acid phosphatase: optimum pH, optimum temperature, pH stability, temperature stability, thermal inactivation, substrate specificity, effect of enzyme concentration, effect of substrate concentration, activation energy, and effect of inhibitor and activator. The molecular mass of acid phosphatase was estimated to be 58 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The optimum pH was 5.7 and the optimum temperature was 50 degrees C. The enzyme was stable at pH 4.0-10.0 and 40-60 degrees C. Activation energy was between 10 and 20 kcal, and as Michaelis Menten coefficients, Vm values were 100 and 20 mM/s and Km values were 21.27 and 8.33 mM for paranitrophenylphosphate and paranitrophenyl, respectively. Studies of the effect of metal ions on enzyme activity showed both an activating and a deactivating effect. While Cu, Mo, and Mn showed strong inhibitory effects, Na, Ca, and K were the significant activators of acid phosphatase.

Feeding barley grain steeped in lactic acid modulates rumen fermentation patterns and increases milk fat content in dairy cows.

PubMed

Iqbal, S; Zebeli, Q; Mazzolari, A; Bertoni, G; Dunn, S M; Yang, W Z; Ametaj, B N

2009-12-01

The objectives of the present in vivo and in situ trials were to evaluate whether feeding barley grain steeped in lactic acid (LA) would affect rumen fermentation patterns, in situ dry matter (DM) degradation kinetics, and milk production and composition in lactating dairy cows. The in vivo trial involved 8 rumen-fistulated Holstein cows fed once daily a total mixed ration containing rolled barley grain (27% in DM) steeped for 48 h in an equal quantity of tap water (CTR) or in 0.5% LA (TRT) in a 2 x 2 crossover design. The in situ trials consisted of incubation of untreated rolled barley grain in cows fed CTR or TRT diets and of incubation of 3 different substrates including CTR or barley grain steeped in 0.5% or 1.0% LA (TRT1 and TRT2, respectively) up to 72 h in the rumen. Results of the in vivo trial indicated that cows fed the TRT diet had greater rumen pH during most intensive fermentation phases at 10 and 12 h post-feeding. The latter effect was associated with a shorter duration in which rumen pH was below 5.8 for cows fed the TRT diet (2.4 h) compared with CTR diet (3.9 h). Furthermore, cows fed the TRT diet had lower concentrations of volatile fatty acids at 2 and 4 h post-feeding. In addition, concentrations of preprandial volatile fatty acids were lower in the rumen fluid of cows fed the TRT diet. Results also showed that molar proportion of acetate was lower, whereas propionate tended to increase by feeding cows the TRT diet. Cows fed the TRT diet demonstrated greater rumen in situ lag time of substrate DM degradation and a tendency to lower the fractional degradation rate. Other in situ results indicated a quadratic effect of LA on the effective rumen degradability of substrates whereby the latter variable was decreased from CTR to TRT1 but increased for TRT2 substrate. Although the diet did not affect actual milk yield, fat-corrected milk, percentages of milk protein, and lactose and concentration of milk urea nitrogen, cows fed the TRT diet increased milk fat content and tended to increase fat:protein ratio in the milk. In conclusion, results demonstrated that treatment of barley grain with LA lowered the risk of subacute rumen acidosis and maintained high milk fat content in late-lactating Holstein cows fed diets based on barley grain.

Computational Investigation of the pH Dependence of Loop Flexibility and Catalytic Function in Glycoside Hydrolases*

PubMed Central

Bu, Lintao; Crowley, Michael F.; Himmel, Michael E.; Beckham, Gregg T.

2013-01-01

Cellulase enzymes cleave glycosidic bonds in cellulose to produce cellobiose via either retaining or inverting hydrolysis mechanisms, which are significantly pH-dependent. Many fungal cellulases function optimally at pH ∼5, and their activities decrease dramatically at higher or lower pH. To understand the molecular-level implications of pH in cellulase structure, we use a hybrid, solvent-based, constant pH molecular dynamics method combined with pH-based replica exchange to determine the pKa values of titratable residues of a glycoside hydrolase (GH) family 6 cellobiohydrolase (Cel6A) and a GH family 7 cellobiohydrolase (Cel7A) from the fungus Hypocrea jecorina. For both enzymes, we demonstrate that a bound substrate significantly affects the pKa values of the acid residues at the catalytic center. The calculated pKa values of catalytic residues confirm their proposed roles from structural studies and are consistent with the experimentally measured apparent pKa values. Additionally, GHs are known to impart a strained pucker conformation in carbohydrate substrates in active sites for catalysis, and results from free energy calculations combined with constant pH molecular dynamics suggest that the correct ring pucker is stable near the optimal pH for both Cel6A and Cel7A. Much longer molecular dynamics simulations of Cel6A and Cel7A with fixed protonation states based on the calculated pKa values suggest that pH affects the flexibility of tunnel loops, which likely affects processivity and substrate complexation. Taken together, this work demonstrates several molecular-level effects of pH on GH enzymes important for cellulose turnover in the biosphere and relevant to biomass conversion processes. PMID:23504310

Characteristic of Fermented Whey Beverage with Addition of Tomato Juice (Lycopersicum esculentum)

NASA Astrophysics Data System (ADS)

Nursiwi, A.; Nurhartadi, E.; Utami, R.; Sari, A. M.; Laksono, P. W.; Aprilia, E. N.

2017-04-01

Whey is the liquid resulting from the coagulation of milk from cheese manufacture. The availability of lactose in whey and presence of other essential nutrients for the growth of microorganisms makes it one of the potential substrate for the production of different bio-products through fermentation process. Lactic acid production through fermentation from lactic acid bacteria could be an alternative processing route for whey lactose utilization. However, a problem with such approaches is the low total solids content. Sucrose and tomato juice added to increases the total solids content. The aim of this work was to study the characteristic of fermented whey beverage with different tomato juice concentration (5, 10, 15%) using probiotic bacteria Lactobacillus acidophilus and Lactobacillus plantarum. Lactic acid content, pH, antioxidant activity, and sensory properties of fermented whey beverage samples were examined after 18hours fermentation. Fermented whey beverage with 5% tomato juice obtained the highest scores for color, aroma, flavor, texture and overall attributes. The lactic acid content and pH of fermented whey beverage ranged from 0.326 to 0.437% and from 4.13 to 4.64, respectively. The highest antioxidant activity (9.073%) was found in sample with 15% tomato juice concentration. The best formulation is the sample with 5% of tomato juice concentration.

[Biodegradation of nitrobenzene by a halophilic Myroides odoratimimus strain Y6].

PubMed

Li, Tian; Qian, Kun; Xiao, Wei; Wang, Jin-Jun; Deng, Xin-Ping

2013-02-01

Aimed at efficient remediation of nitrobenzene-contaminated saline wastewater, the nitrobenzene-degrading characteristics of a Myroides odoratimimus strain Y6 were studied and analyzed. The effects of temperature, pH, initial concentration of nitrobenzene, inoculum concentration and culture type on the biodegradation of nitrobenzene by strain Y6 under saline conditions were studied. Strain Y6 showed the highest efficiency of nitrobenzene degradation in 7% NaC1 (mass fraction). The optimal conditions for the biodegradation of nitrobenzene by strain Y6 were at pH 6.0, 28 degrees C and D600 = 1. With initial concentrations of 100 and 200 mg.L-1, 97.5% and 65.7% of nitrobenzene were transformed after 168 h in 7% NaCL, respectively. Three kinds of additional compounds, glucose, starch and glycerin were tested to choose a favorite carbon source for the co-metabolism of strain Y6. The results showed that all these three compounds could promote nitrobenzene biodegradation and cell growth. And the rate of degradation could increase to 93.3% ,with 800 mg.L-1 glucose as the primary substrate. These results suggest that strain Y6 could be a potential candidate for treating nitrobenzene-contaminated saline wastewater. To date, this is the only study on the degradation of nitrobenzene by M. odoratimimus.

Corrosion inhibition by inorganic cationic inhibitors on the high strength alumunium alloy, 2024-T3

NASA Astrophysics Data System (ADS)

Chilukuri, Anusha

The toxicity and carcinogenic nature of chromates has led to the investigation of environmentally friendly compounds that offer good corrosion resistance to AA 2024-T3. Among the candidate inhibitors are rare earth metal cationic (REM) and zinc compounds, which have received much of attention over the past two decades. A comparative study on the corrosion inhibition caused by rare earth metal cations, Ce3+, Pr3+, La3+ and Zn2+ cations on the alloy was done. Cathodic polarization showed that these inhibitor ions suppress the oxygen reduction reaction (ORR) to varying extents with Zn2+ providing the best inhibition. Pr3+ exhibited windows of concentration (100-300 ppm) in which the corrosion rate is minimum; similar to the Ce3+ cation. Scanning Electron Microscopy (SEM) studies showed that the mechanism of inhibition of the Pr3+ ion is also similar to that of the Ce3+ ion. Potentiodynamic polarization experiments after 30 min immersion time showed greatest suppression of oxygen reduction reaction in neutral chloride solutions (pH 7), which reached a maximum at a Zn2+ ion concentration of 5 mM. Anodic polarization experiments after 30 min immersion time, showed no anodic inhibition by the inhibitor in any concentration (0.1 mM - 10 mM) and at any pH. However, anodic polarization of samples immersed after longer immersion times (upto 4 days) in mildly acidic Zn2+ (pH 4) solutions showed significant reduction in anodic kinetics indicating that zinc also acts as a “slow anodic inhibitor”. In contrast to the polarization experiments, coupons exposed to inhibited acidic solutions at pH 4 showed complete suppression of dissolution of Al2CuMg particles compared to zinc-free solutions in the SEM studies. Samples exposed in pH 4 Zn2+-bearing solution exhibited highest polarization resistance which was also observed to increase with time. In deaerated solutions, the inhibition by Zn2+ at pH 4 is not observed as strongly. The ability to make the interfacial electrolyte alkaline is retarded in the absence of oxygen. As a result precipitation of Zn oxides and hydroxides was suppressed. Impedance in decarbonated chloride solutions showed that the absence of CO 2 reduces inhibition by Zn2+ at pH 4. The carbonate protective layer formed in aerated solutions is essential for providing better protection of the substrate at pH 4. Inhibitor cations were exchanged into insoluble ion-exchanging sodium bentonites and incorporated as pigments in organic coatings applied to AA 2024-T3 substrates. XRD of the pigments ensured ion exchange and UV-visible spectroscopy was used to characterize inhibitor ion release from the bentonites. Salt spray exposure tests on scribed panels were preformed and results were compared to those from SrCrO4 pigmented coatings. Zn-exchanged bentonite pigmented coatings showed better performance compared to the other exchanged bentonites when incorporated into epoxy coatings with total impedance magnitude in the same order as SrCrO4. PVB (Polyvinyl Butyral) coatings containing Zn bentonite, however, did not show superior behaviour in the impedance response due to less or no water uptake. Salt spray exposures for a period of 336 h, showed that Zn bentonite incorporated into PVB suppressed blistering compared to the neat PVB and other pigmented bentonites.

Preparation and evaluation of nanocellulose-gold nanoparticle nanocomposites for SERS applications.

PubMed

Wei, Haoran; Rodriguez, Katia; Renneckar, Scott; Leng, Weinan; Vikesland, Peter J

2015-08-21

Nanocellulose is of research interest due to its extraordinary optical, thermal, and mechanical properties. The incorporation of guest nanoparticles into nanocellulose substrates enables production of novel nanocomposites with a broad range of applications. In this study, gold nanoparticle/bacterial cellulose (AuNP/BC) nanocomposites were prepared and evaluated for their applicability as surface-enhanced Raman scattering (SERS) substrates. The nanocomposites were prepared by citrate mediated in situ reduction of Au(3+) in the presence of a BC hydrogel at 303 K. Both the size and morphology of the AuNPs were functions of the HAuCl4 and citrate concentrations. At high HAuCl4 concentrations, Au nanoplates form within the nanocomposites and are responsible for high SERS enhancements. At lower HAuCl4 concentrations, uniform nanospheres form and the SERS enhancement is dependent on the nanosphere size. The time-resolved increase in the SERS signal was probed as a function of drying time with SERS 'hot-spots' primarily forming in the final minutes of nanocomposite drying. The application of the AuNP/BC nanocomposites for detection of the SERS active dyes MGITC and R6G as well as the environmental contaminant atrazine is illustrated as is its use under low and high pH conditions. The results indicate the broad applicability of this nanocomposite for analyte detection.

Fungal trehalose phosphorylase: kinetic mechanism, pH-dependence of the reaction and some structural properties of the enzyme from Schizophyllum commune.

PubMed Central

Eis, C; Watkins, M; Prohaska, T; Nidetzky, B

2001-01-01

Initial-velocity measurements for the phospholysis and synthesis of alpha,alpha-trehalose catalysed by trehalose phosphorylase from Schizophyllum commune and product and dead-end inhibitor studies show that this enzyme has an ordered Bi Bi kinetic mechanism, in which phosphate binds before alpha,alpha-trehalose, and alpha-D-glucose is released before alpha-D-glucose 1-phosphate. The free-energy profile for the enzymic reaction at physiological reactant concentrations displays its largest barriers for steps involved in reverse glucosyl transfer to D-glucose, and reveals the direction of phospholysis to be favoured thermodynamically. The pH dependence of kinetic parameters for all substrates and the dissociation constant of D-glucal, a competitive dead-end inhibitor against D-glucose (K(i)=0.3 mM at pH 6.6 and 30 degrees C), were determined. Maximum velocities and catalytic efficiencies for the forward and reverse reactions decrease at high and low pH, giving apparent pK values of 7.2--7.8 and 5.5--6.0 for two groups whose correct protonation state is required for catalysis. The pH dependences of k(cat)/K are interpreted in terms of monoanionic phosphate and alpha-D-glucose 1-phosphate being the substrates, and of the pK value seen at high pH corresponding to the phosphate group in solution or bound to the enzyme. The K(i) value for the inhibitor decreases outside the optimum pH range for catalysis, indicating that binding of D-glucal is tighter with incorrectly ionized forms of the complex between the enzyme and alpha-D-glucose 1-phosphate. Each molecule of trehalose phosphorylase contains one Mg(2+) that is non-dissociable in the presence of metal chelators. Measurements of the (26)Mg(2+)/(24)Mg(2+) ratio in the solvent and on the enzyme by using inductively coupled plasma MS show that exchange of metal ion between protein and solution does not occur at measurable rates. Tryptic peptide mass mapping reveals close structural similarity between trehalose phosphorylases from basidiomycete fungi. PMID:11389683

Electroless Cu Plating on Anodized Al Substrate for High Power LED.

PubMed

Rha, Sa-Kyun; Lee, Youn-Seoung

2015-03-01

Area-selective copper deposition on screen printed Ag pattern/anodized Al/Al substrate was attempted using a neutral electroless plating processes for printed circuit boards (PCBs), according to a range of variation of pH 6.5-pH 8 at 70 °C. The utilized basic electroless solution consisted of copper(II) sulfate pentahydrate, sodium phosphinate monohydrate, sodium citrate tribasic dihydrate, ammonium chloride, and nickel(II) sulfate hexahydrate. The pH of the copper plating solutions was adjusted from pH 6.5 to pH 8 using NH4OH. Using electroless plating in pH 6.5 and pH 7 baths, surface damage to the anodized Al layer hardly occurred; the structure of the plated Cu-rich films was a typical fcc-Cu, but a small Ni component was co-deposited. In electroless plating at pH 8, the surface of the anodized Al layer was damaged and the Cu film was composed of a lot of Ni and P which were co-deposited with Cu. Finally, in a pH 7 bath, we can make a selectively electroless plated Cu film on a PCB without any lithography and without surface damage to the anodized Al layer.

Characteristics of strain-sensitive photonic crystal cavities in a flexible substrate.

PubMed

No, You-Shin; Choi, Jae-Hyuck; Kim, Kyoung-Ho; Park, Hong-Gyu

2016-11-14

High-index semiconductor photonic crystal (PhC) cavities in a flexible substrate support strong and tunable optical resonances that can be used for highly sensitive and spatially localized detection of mechanical deformations in physical systems. Here, we report theoretical studies and fundamental understandings of resonant behavior of an optical mode excited in strain-sensitive rod-type PhC cavities consisting of high-index dielectric nanorods embedded in a low-index flexible polymer substrate. Using the three-dimensional finite-difference time-domain simulation method, we calculated two-dimensional transverse-electric-like photonic band diagrams and the three-dimensional dispersion surfaces near the first Γ-point band edge of unidirectionally strained PhCs. A broken rotational symmetry in the PhCs modifies the photonic band structures and results in the asymmetric distributions and different levels of changes in normalized frequencies near the first Γ-point band edge in the reciprocal space, which consequently reveals strain-dependent directional optical losses and selected emission patterns. The calculated electric fields, resonant wavelengths, and quality factors of the band-edge modes in the strained PhCs show an excellent agreement with the results of qualitative analysis of modified dispersion surfaces. Furthermore, polarization-resolved time-averaged Poynting vectors exhibit characteristic dipole-like emission patterns with preferentially selected linear polarizations, originating from the asymmetric band structures in the strained PhCs.

Methane production and consumption in grassland and boreal ecosystems

NASA Technical Reports Server (NTRS)

Schimel, David S.; Burke, Ingrid C.; Johnston, Carol; Pastor, John

1994-01-01

The objectives of the this project were to develop a mechanistic understanding of methane production and oxidation suitable for incorporation into spatially explicit models for spatial extrapolation. Field studies were undertaken in Minnesota, Canada, and Colorado to explore the process controls over the two microbial mediated methane transformations in a range of environments. Field measurements were done in conjunction with ongoing studies in Canada (the Canadian Northern Wetlands Projects: NOWES) and in Colorado (The Shortgrass Steppe Long Term Ecological Research Project: LTER). One of the central hypotheses of the proposal was that methane production should be substrate limited, as well as being controlled by physical variables influencing microbial activity (temperature, oxidation status, and pH). Laboratory studies of peats from Canada and Minnesota (Northern and Southern Boreal) were conducted with amendments of a methanogenic substrate at multiple temperatures and at multiple pHs (the latter by titrating samples). The studies showed control by substrate, pH, and temperature in order in anaerobic samples. Field and laboratory manipulations of natural plant litter, rather than an acetogenic substrate, showed similarly large effects. The studies concluded that substrate is an important control over methanogenesis, that substrate availability in the field is closely coupled to the chemistry of the dominant vegetation influencing its decomposition rate, that most methane is produced from recent plant litter, and that landscape changes in pH are an important control, highly correlated with vegetation.

Development of an IrO x micro pH sensor array on flexible polymer substrate

NASA Astrophysics Data System (ADS)

Huang, Wen-Ding; Wang, Jianqun; Ativanichayaphong, Thermpon; Chiao, Mu; Chiao, J. C.

2008-03-01

pH sensor is an essential component used in many chemical, food, and bio-material industries. Conventional glass electrodes have been used to construct pH sensors, however, have some disadvantages in specific applications. It is difficult to use glass electrodes for in vivo biomedical or food monitoring applications due to size limitation and no deformability. In this paper, we present design and fabrication processes of a miniature iridium oxide thin film pH sensor array on flexible polymer substrates. The amorphous iridium oxide thin film was used as the sensing material. A sol-gel dip-coating process of iridium oxide film was demonstrated in this paper. A super-Nernstian response has been measured on individual sensors of the array with a slope of -71.6+/-3 mV/pH at 25°C within the pH range between 2.83 and 11.04.

From small molecules to polymeric catalysts in the oscillatory carbonylation reaction: multiple effects of adding HI.

PubMed

Isakova, Anna; Murdoch, Billy J; Novakovic, Katarina

2018-04-04

The oscillatory palladium-catalysed carbonylation reaction opens new horizons for applications in smart materials due to the versatility of its conditions and substrates, as well as the adjustability of amplitude and period of pH oscillations. A variety of viable substrates have been demonstrated, including polymeric alkyne-terminated substrates. However, so far, there have not been any reports of polymer-based palladium catalysts in oscillatory mode. In this paper, we demonstrate pH oscillations in various systems, using commercially available palladium acetate, a triphenylphosphine palladium acetate complex and a polymer-bound palladium catalyst. While palladium acetate was able to generate oscillations under the conditions already established in our previous research on PdI2-catalysed oscillators, the other two catalysts needed the addition of HI to induce oscillations. HI forced an initial pH drop, bringing pH into the range where oscillations generally occur. Addition of HI had a significant effect on all catalysts, modifying the amplitude and period of oscillations, oscillation mode, as well as starting material conversion and product distribution.

Cadmium Coating Alternatives for High- Strength Steel JTP - Phase 2

DTIC Science & Technology

2009-09-03

Substrate 4130 Washer 17 - 4PH Washer CuBe Washer AlNiBr Washer Salt Spray Cyclic Salt Spray Cyclic Salt Spray Cyclic Salt Spray Cyclic No coating...2009, Westminster, CO. Sponsored by SERDP/ESTCP. 14. ABSTRACT 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17 . LIMITATION OF ABSTRACT Same...Passed Appearance Testing U.S. AIR FORCE Primary Coating Bend Adhesion Test Results Coating Bend Adhesion Results 4130 steel substrate 17 -4 PH stainless

pH, dissolved oxygen, and adsorption effects on metal removal in anaerobic bioreactors.

PubMed

Willow, Mark A; Cohen, Ronald R H

2003-01-01

Anaerobic bioreactors were used to test the effect of the pH of influent on the removal efficiency of heavy metals from acid-rock drainage. Two studies used a near-neutral-pH, metal-laden influent to examine the heavy metal removal efficiency and hydraulic residence time requirements of the reactors. Another study used the more typical low-pH mine drainage influent. Experiments also were done to (i) test the effects of oxygen content of feed water on metal removal and (ii) the adsorptive capacity of the reactor organic substrate. Analysis of the results indicates that bacterial sulfate reduction may be a zero-order kinetic reaction relative to sulfate concentrations used in the experiments, and may be the factor that controls the metal mass removal efficiency in the anaerobic treatment systems. The sorptive capacities of the organic substrate used in the experiments had not been exhausted during the experiments as indicated by the loading rates of removal of metals exceeding the mass production rates of sulfide. Microbial sulfate reduction was less in the reactors receiving low-pH influent during experiments with short residence times. Sulfate-reducing bacteria may have been inhibited by high flows of low-pH water. Dissolved oxygen content of the feed waters had little effect on sulfate reduction and metal removal capacity.

Separation of polyphenols and arecoline from areca nut (Areca catechu L.) by solvent extraction, its antioxidant activity, and identification of polyphenols.

PubMed

Chavan, Yogita V; Singhal, Rekha S

2013-08-15

Areca nut (Areca catechu L.) or betel nut, a commercial cash crop, is a rich source of polyphenols but also contains toxic alkaloids, mainly arecoline. Separation of these bioactive polyphenols from toxic constituents could propel the safe and beneficial use of betel nut; also it will help arecanut processing industries to produce arecoline-free products. With the aim to develop an effective method for maximum extraction of polyphenols with minimum arecoline, several factors such as nature of the solvent, pH (2-10), substrate concentration (6-14 %) and extraction time (30-150 min) under shaking conditions were evaluated. Qualitative analysis was done using spectrophotometry and high-performance liquid chromatography (HPLC). Maximum extraction of polyphenols (407.47 mg GAE g(-1)), total tannin and its antioxidant activity with minimum arecoline (1.73 mg g(-1) of sample) was achieved by using 80% acetone at pH 4 for 90 min with 10% w/v substrate under shaking conditions. Solvent extraction under optimized parameters gave maximum polyphenols with minimum extraction of arecoline, and highest ratio of polyphenols to arecoline. HPLC and liquid chromatography-mass spectrometry results confirmed the presence of catechin and epicatechin in the extract, which suggests its potential as a source of bioactives. © 2013 Society of Chemical Industry.

Optimal production of 7,10-dihydroxy-8(E)-hexadecenoic acid from palmitoleic acid by Pseudomonas aeruginosa PR3.

PubMed

Bae, Jae-Han; Suh, Min-Jung; Kim, Beom-Soo; Hou, Ching T; Lee, In-Jung; Kim, In-Hwan; Kim, Hak-Ryul

2010-09-30

The hydroxylation of unsaturated fatty acids by bacterial strains is one type of value-adding bioconversion processes. This process generates new hydroxy fatty acids (HFA) carrying special properties such as higher viscosity and reactivity compared with normal fatty acids. Among microbial strains tested for HFA production, Pseudomonas aeruginosa PR3 is well known to utilize various unsaturated fatty acids to produce mono-, di- and tri-hydroxy fatty acids. Previously we reported that strain PR3 could produce a novel value-added hydroxy fatty acid 7,10-dihydroxy-8(E)-hexadecenoic acid (DHD) from palmitoleic acid (Bae et al. (2007) Appl. Microbiol. Biotechnol. 75, 435-440). In this study, we focused on the development of the optimal nutritional and environmental conditions for DHD production from palmitoleic acid by PR3. Optimal carbon and nitrogen sources for DHD production were fructose and yeast extract, respectively. Optimal initial medium pH and incubation temperature were pH 8.0 and 30 degrees C and magnesium ion was essentially required for DHD production. Substrate concentration and time of substrate addition were also optimized. Under optimized conditions, maximal DHD production was 1600mg/l representing 26.7% conversion yield. Copyright 2009 Elsevier B.V. All rights reserved.

Valorization of cruor slaughterhouse by-product by enzymatic hydrolysis for the production of antibacterial peptides: focus on α 1-32 family peptides mechanism and kinetics modeling.

PubMed

Hedhili, K; Dimitrov, K; Vauchel, P; Sila, A; Chataigné, G; Dhulster, P; Nedjar, N

2015-10-01

Bovine hemoglobin is the major component of the cruor (slaughterhouse by-product) and can be considered as an important source of active peptides that could be obtained by pepsic hydrolysis. The kinetics of appearance and disappearance of several antibacterial peptides from α 1-32 family during hydrolysis of synthesized α 1-32 peptide, of purified bovine hemoglobin and of cruor was studied, and reaction scheme for the hydrolysis of α 1-32 family peptides from these three sources was determined. On this basis, a mathematical model was proposed to predict the concentration of each peptide of interest of this family depending on hydrolysis time, and also on temperature (in the range 15-37 °C), pH (in the range 3.5-5.5) and enzyme to substrate ratio (in the range 1/50-1/200 for the synthesized peptide and 1/5-1/20 for purified bovine hemoglobin and cruor). Apparent rate constants of reactions were determined by applying the model on a set of experimental data and it was shown that they depended on the temperature according to Arrhenius's law, that their dependence on the pH was linear, and that enzyme to substrate ratio influence was limited (in the studied range).

Experimental study of bioethanol production using mixed cassava and durian seed

NASA Astrophysics Data System (ADS)

Seer, Q. H.; Nandong, J.; Shanon, T.

2017-06-01

The production of biofuels using conventional fermentation feedstocks, such as sugar-and starch-based agricultural crops will in the long-term lead to a serious competition with human-animal food consumption. To avoid this competition, it is important to explore various alternative feedstocks especially those from inedible waste materials. Potentially, fruit wastes such as damaged fruits, peels and seeds represent alternative cheap feedstocks for biofuel production. In this work, an experimental study was conducted on ethanol production using mixed cassava and durian seeds through fermentation by Saccharomyces cerevisiae yeast. The effects of pH, temperature and ratio of hydrolyzed cassava to durian seeds on the ethanol yield, substrate consumption and product formation rates were analyzed in the study. In flask-scale fermentation using the mixed cassava-durian seeds, it was found that the highest ethanol yield of 45.9 and a final ethanol concentration of 24.92 g/L were achieved at pH 5.0, temperature 35°C and 50:50 volume ratio of hydrolyzed cassava to durian seeds for a batch period of 48 hours. Additionally, the ethanol, glucose and biomass concentration profiles in a lab-scale bioreactor were examined for the fermentation using the proposed materials under the flask-scale optimum conditions. The ethanol yield of 35.7 and a final ethanol concentration of 14.61 g/L were obtained over a period of 46 hours where the glucose was almost fully consumed. It is worth noting that both pH and temperature have significant impacts on the fermentation process using the mixed cassava-durian seeds.

[Isolation, identification and rumen fermentation characteristics of Propionibacterium acnes].

PubMed

Wu, Ling; Zhao, Mingjuan; Xia, Cheng; Ni, Hongbo; Zhang, Hongyou

2009-02-01

Characteristic of energy metabolism in ruminant is a negative energy balance in perinatal period. Propionic acid from ruminal microbe fermentation is a vital glyconeogenesis substrate for preventing negative energy balance. We isolated and screened a Propionibacterium acnes strain from health cow rumen fluid, and studied its rumen fermentation characteristics. A Propionibacterium acnes strain from rumen fluid of health cow with permanent rumen fistula under sterile condition was isolated by segregation procedure of anaerobic bacterium and Sodium Lactate Broth (SLB), and identified by extraction of the genome DNA, cloning of the 16S rRNA gene, and sequencing. We studied the effect of the strain on pH, volatile fatty acid and lactic acid in rumen fluid in vitro and in vivo. A bacterium isolated from health cow rumen fluid was identified as Propionibacterium acnes by morphology, biochemical characteristics and sequence homology. In vitro, pH in rumen fluid decreased to the lowest after rumen fermentation of the strain for 12 h, then increased gradually. However, concentration of volatile fatty acid, such as acetic acid, propionic acid and butyric acid, increased to the highest after rumen fermentation of the strain for 12 h, then decreased gradually in vitro. The concentration of lactic acid and ratio of acetate to propionate decreased overall in vitro. In vivo, pH in rumen fluid decreased overall, concentration, of the volatile fatty acid increased overall. A strain of Propionibacterium acnes was isolated successfully from health cow rumen fluid. It is an important basis to develop microecological preparation for preventing cows' negative energy balance in perinatal period in future.

Carbon Source Preference in Chemosynthetic Hot Spring Communities

PubMed Central

Urschel, Matthew R.; Kubo, Michael D.; Hoehler, Tori M.; Peters, John W.

2015-01-01

Rates of dissolved inorganic carbon (DIC), formate, and acetate mineralization and/or assimilation were determined in 13 high-temperature (>73°C) hot springs in Yellowstone National Park (YNP), Wyoming, in order to evaluate the relative importance of these substrates in supporting microbial metabolism. While 9 of the hot spring communities exhibited rates of DIC assimilation that were greater than those of formate and acetate assimilation, 2 exhibited rates of formate and/or acetate assimilation that exceeded those of DIC assimilation. Overall rates of DIC, formate, and acetate mineralization and assimilation were positively correlated with spring pH but showed little correlation with temperature. Communities sampled from hot springs with similar geochemistries generally exhibited similar rates of substrate transformation, as well as similar community compositions, as revealed by 16S rRNA gene-tagged sequencing. Amendment of microcosms with small (micromolar) amounts of formate suppressed DIC assimilation in short-term (<45-min) incubations, despite the presence of native DIC concentrations that exceeded those of added formate by 2 to 3 orders of magnitude. The concentration of added formate required to suppress DIC assimilation was similar to the affinity constant (Km) for formate transformation, as determined by community kinetic assays. These results suggest that dominant chemoautotrophs in high-temperature communities are facultatively autotrophic or mixotrophic, are adapted to fluctuating nutrient availabilities, and are capable of taking advantage of energy-rich organic substrates when they become available. PMID:25819970

Efficient DNA ligation in DNA–RNA hybrid helices by Chlorella virus DNA ligase

PubMed Central

Lohman, Gregory J. S.; Zhang, Yinhua; Zhelkovsky, Alexander M.; Cantor, Eric J.; Evans, Thomas C.

2014-01-01

Single-stranded DNA molecules (ssDNA) annealed to an RNA splint are notoriously poor substrates for DNA ligases. Herein we report the unexpectedly efficient ligation of RNA-splinted DNA by Chlorella virus DNA ligase (PBCV-1 DNA ligase). PBCV-1 DNA ligase ligated ssDNA splinted by RNA with kcat ≈ 8 x 10−3 s−1 and KM < 1 nM at 25°C under conditions where T4 DNA ligase produced only 5′-adenylylated DNA with a 20-fold lower kcat and a KM ≈ 300 nM. The rate of ligation increased with addition of Mn2+, but was strongly inhibited by concentrations of NaCl >100 mM. Abortive adenylylation was suppressed at low ATP concentrations (<100 µM) and pH >8, leading to increased product yields. The ligation reaction was rapid for a broad range of substrate sequences, but was relatively slower for substrates with a 5′-phosphorylated dC or dG residue on the 3′ side of the ligation junction. Nevertheless, PBCV-1 DNA ligase ligated all sequences tested with 10-fold less enzyme and 15-fold shorter incubation times than required when using T4 DNA ligase. Furthermore, this ligase was used in a ligation-based detection assay system to show increased sensitivity over T4 DNA ligase in the specific detection of a target mRNA. PMID:24203707

Application of a long-lasting colloidal substrate with pH and hydrogen sulfide control capabilities to remediate TCE-contaminated groundwater.

PubMed

Sheu, Y T; Chen, S C; Chien, C C; Chen, C C; Kao, C M

2015-03-02

A long-lasting emulsified colloidal substrate (LECS) was developed for continuous carbon and nanoscale zero-valent iron (nZVI) release to remediate trichloroethylene (TCE)-contaminated groundwater under reductive dechlorinating conditions. The developed LECS contained nZVI, vegetable oil, surfactants (Simple Green™ and lecithin), molasses, lactate, and minerals. An emulsification study was performed to evaluate the globule droplet size and stability of LECS. The results show that a stable oil-in-water emulsion with uniformly small droplets (0.7 μm) was produced, which could continuously release the primary substrates. The emulsified solution could serve as the dispensing agent, and nZVI particles (with diameter 100-200 nm) were distributed in the emulsion evenly without aggregation. Microcosm results showed that the LECS caused a rapid increase in the total organic carbon concentration (up to 488 mg/L), and reductive dechlorination of TCE was significantly enhanced. Up to 99% of TCE (with initial concentration of 7.4 mg/L) was removed after 130 days of operation. Acidification was prevented by the production of hydroxide ion by the oxidation of nZVI. The formation of iron sulfide reduced the odor from produced hydrogen sulfide. Microbial analyses reveal that dechlorinating bacteria existed in soils, which might contribute to TCE dechlorination. Copyright © 2014 Elsevier B.V. All rights reserved.

In Vivo 31P-Nuclear Magnetic Resonance Studies of Glyphosate Uptake, Vacuolar Sequestration, and Tonoplast Pump Activity in Glyphosate-Resistant Horseweed1[W

PubMed Central

Ge, Xia; d’Avignon, D. André; Ackerman, Joseph J.H.; Sammons, R. Douglas

2014-01-01

Horseweed (Conyza canadensis) is considered a significant glyphosate-resistant (GR) weed in agriculture, spreading to 21 states in the United States and now found globally on five continents. This laboratory previously reported rapid vacuolar sequestration of glyphosate as the mechanism of resistance in GR horseweed. The observation of vacuole sequestration is consistent with the existence of a tonoplast-bound transporter. 31P-Nuclear magnetic resonance experiments performed in vivo with GR horseweed leaf tissue show that glyphosate entry into the plant cell (cytosolic compartment) is (1) first order in extracellular glyphosate concentration, independent of pH and dependent upon ATP; (2) competitively inhibited by alternative substrates (aminomethyl phosphonate [AMPA] and N-methyl glyphosate [NMG]), which themselves enter the plant cell; and (3) blocked by vanadate, a known inhibitor/blocker of ATP-dependent transporters. Vacuole sequestration of glyphosate is (1) first order in cytosolic glyphosate concentration and dependent upon ATP; (2) competitively inhibited by alternative substrates (AMPA and NMG), which themselves enter the plant vacuole; and (3) saturable. 31P-Nuclear magnetic resonance findings with GR horseweed are consistent with the active transport of glyphosate and alternative substrates (AMPA and NMG) across the plasma membrane and tonoplast in a manner characteristic of ATP-binding cassette transporters, similar to those that have been identified in mammalian cells. PMID:25185124

Time and substrate dependent exudation of carboxylates by Lupinus albus L. and Brassica napus L.

PubMed

Mimmo, Tanja; Hann, Stephan; Jaitz, Leonhard; Cesco, Stefano; Gessa, Carlo Emanuele; Puschenreiter, Markus

2011-11-01

Root exudates influence significantly physical, chemical and biological characteristics of rhizosphere soil. Their qualitative and quantitative composition is affected by environmental factors such as pH, soil type, oxygen status, light intensity, soil temperature, plant growth, nutrient availability and microorganisms. The aim of the present study was to assess the influence of growth substrate and plant age on the release of carboxylates from Lupinus albus L. and Brassica napus L. Both plant species were studied in continuously percolated microcosms filled with either sand, soil or sand + soil (1:1) mixture. Soil solution was collected every week at 7, 14, 21, 28 and 35 days after planting (DAP). Carboxylate concentrations were determined by reversed-phase liquid chromatography - electrospray ionization - time of flight mass spectrometry (LC-ESI-TOFMS). Oxalate, citrate, succinate, malate and maleate were detected in soil solutions of both plant species. Their concentrations were correlated with the physiological status of the plant and the growth substrate. Oxalate was the predominant carboxylate detected within the soil solution of B. napus plants while oxalate and citrate were the predominant ones found in the soil solutions of L. albus plants. The sampling determination of carboxylates released by plant roots with continuous percolation systems seems to be promising as it is a non-destructive method and allows sampling and determination of soluble low molecular weight organic compounds derived from root exudation as well as the concentration of soluble nutrients, which both might reflect the nutritional status of plants. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

Sulphoxidation reaction catalysed by myeloperoxidase from human leucocytes.

PubMed

Capeillère-Blandin, C; Martin, C; Gaggero, N; Pasta, P; Carrea, G; Colonna, S

1998-10-01

The oxidation of alkyl aryl sulphides by myeloperoxidase (MPO) at the expense of hydrogen peroxide was investigated under steady-state conditions. The sulphide concentration effect was studied under saturating H2O2 concentrations at pH 5.0 and 20 degreesC. The kinetic constants, kcat and Km, of the different substrates were determined and the values were in the 1-10 s-1 range and around 43+/-26 microM respectively, whatever the sulphide considered. In the case of p-substituted thioanisoles, the oxidation rate was dependent upon the substituent effect. The correlation of log(kcat) with the substituent constants (sigma+ values) (Hammett equation) could be explained by a reaction mechanism involving the enzyme compound II and a sulphenium radical cation. This conclusion was also supported by spectrophotometric analysis of catalytic intermediates of the enzyme, showing the accumulation of compound II. Moreover, chiral HPLC analyses showed that MPO oxidation of alkyl aryl sulphides produced the corresponding (R)-sulphoxides with a low enantioselectivity (4-8%). Chloride ion effects on the MPO-catalysed oxygenation of sulphides were also studied. Chloride acted as a substrate for MPO and as an activator in MPO-catalysed sulphoxidation. Inhibition occurred at chloride concentrations above 120 mM, whereas below 120 mM, chloride increased the reaction rate when using p-tolyl methyl sulphide as the substrate. In the presence of 100 mM chloride the catalytic efficiency (kcat/Km) of MPO increased 3-4-fold, whatever the sulphide considered, but racemic products were obtained. These data have been interpreted in the light of known structural information on the accessibility of the distal haem cavity.

Insight into Cr6+ reduction efficiency of Rhodococcus erythropolis isolated from coalmine waste water.

PubMed

Banerjee, Soumya; Joshi, S R; Mandal, Tamal; Halder, Gopinath

2017-01-01

A microbial treatment of Cr 6+ contaminated wastewater with a chromium reducing bacteria isolated from coal mine area was investigated. In a series of batch study metal removal was executed under different parametric conditions which include pH (2-7), temperature (20-50 °C), initial Cr 6+ concentration (1-100 mg/L), substrate utilization and its overall effect on biomass generation. Impact of oxygen availability was checked at different agitation speed and its role on the remedial process. Liquid phase reduction of Cr 6+ was measured in terms of substrate reduction and total biomass yield. The bacterium species isolated was able to tolerate Cr 6+ over a wide range from 1 to 100 mg/L before it reached minimum inhibition concentration. Apart from Cr 6+ , the bacterial isolate showed tolerance towards Fe, As, Cu, Ag, Zn, Mn, Mg and Pb. Removal mechanism adopted by the bacterium recommended that it employed accumulation of Cr 6+ as Cr 3+ both within and outside the cell. Classical Monod equation was used to determine the biokinetics of the bacterial isolate along with the interference of metal ion concentration and substrate utilization. Cr 6+ removal was found prominent even in bimetallic solutions. The bacterial isolate was confirmed to be Rhodococcus erythopolis by 16s rRNA molecular characterization. Thus the bacterial isolate obtained from the coal mine area proved to be a potential agent for microbial remediation of Cr 6+ laden waste water. Copyright © 2016 Elsevier Ltd. All rights reserved.

Using Plant Source as a Buffering Agent to Manipulating Rumen Fermentation in an In vitro Gas Production System.

PubMed

Kang, S; Wanapat, M

2013-10-01

The objective of this study was to investigate the effect of banana flower powder (BAFLOP) supplementation on gas production kinetics and rumen fermentation efficiency in in vitro incubation with different ratios of roughage to concentrate in swamp buffalo and cattle rumen fluid. Two male, rumen fistulated dairy steers and swamp buffaloes were used as rumen fluid donors. The treatments were arranged according to a 2×2×3 factorial arrangement in a Completely randomized design by using two ratios of roughage to concentrate (R:C; 75:25 and 25:75) and 3 levels of BAFLOP supplementation (0, 2 and 4% of dietary substrate) into two different kinds of rumen fluid (beef cattle and swamp buffalo). Under this investigation, the results revealed that the rumen ecology was affected by R:C ratio. The pH declined as a result of using high concentrate ratio; however, supplementation of BAFLOP could buffer the pH which led to an improvement of ruminal efficiency. BAFLOP supplementation affected acetic acid (C2) when the proportion of concentrate was increased. However, there were no effect on total volatile fatty acid (TVFA) and butyric acid (C4) by BAFLOP supplementation. The microbial community was affected by BAFLOP supplementation, especially the bacterial population. As revealed by real-time PCR, the populations of F. succinogenes and R. albus were reduced by the high concentrate treatments while that of R. flavafaciens were increased. The populations of three dominant cellulolytic bacteria were enhanced by BAFLOP supplementation, especially on high concentrate diet. BAFLOP supplementation did not influence the ammonia nitrogen (NH3-N) concentration, while R:C did. In addition, the in vitro digestibility was improved by either R:C or BAFLOP supplementation. The BAFLOP supplementation showed an effect on gas production kinetics, except for the gas production rate constant for the insoluble fraction (c), while treatments with high concentrate ratio resulted in the highest values. In addition, BAFLOP tended to increase gas production. Based on this study, it could be concluded that R:C had an effect on rumen ecology both in buffalo and cattle rumen fluid and hence, BAFLOP could be used as a rumen buffering agent for enhancing rumen ecology fed on high concentrate diet. It is recommended that level of BAFLOP supplementation should be at 2 to 4% of total dry matter of substrate. However, in vivo trials should be subsequently conducted to investigate the effect of BAFLOP in high concentrate diets on rumen ecology as well as ruminant production.

Nicotinamide riboside, an unusual, non-typical, substrate of purified purine-nucleoside phosphorylases.

PubMed

Wielgus-Kutrowska, B; Kulikowska, E; Wierzchowski, J; Bzowska, A; Shugar, D

1997-01-15

Nicotinamide 1-beta-D-riboside (Nir), the cationic, reducible moiety of the coenzyme NAD+, has been confirmed as an unusual substrate for purified purine-nucleoside phosphorylase (PNP) from a mammalian source (calf spleen). It is also a substrate of the enzyme from Escherichia coli. The Km values at pH 7, 1.48 mM and 0.62 mM, respectively, were 1-2 orders of magnitude higher than for the natural substrate inosine, but the Vmax values were comparable, 96% and 35% that for Ino. The pseudo first-order rate constants, Vmax/Km, were 1.1% and 2.5% for the calf spleen and E. coli enzymes. The aglycon, nicotinamide, was neither a substrate nor an inhibitor of PNP. Nir was a weak inhibitor of inosine phosphorolysis catalyzed by both enzymes, with Ki values close to the Km for its phosphorolysis, consistent with simple competitive inhibition; this was further confirmed by Dixon plots. Phosphorolysis of the fluorescent positively charged substrate 7-methylguanosine was also inhibited in a competitive manner by both Ino and Nir. Phosphorolysis of Nir by both enzymes was inhibited competitively by several specific inhibitors of calf spleen and E. coli PNP, with Ki values similar to those for inhibition of other natural substrates. The pH dependence of the kinetic constants for the phosphorolysis of Nir and of a variety of other substrates, was extensively investigated, particularly in the alkaline pH range, where Nir exhibited abnormally high substrate activity relative to the reduced reaction rates of both enzymes towards other anionic or neutral substrates. The overall results are discussed in relation to present concepts regarding binding and phosphorolysis of substrates by PNP based on crystallographic data of enzyme-inhibitor complexes, and current studies on enzymatic and nonenzymatic mechanisms of the cleavage of the Nir glycosidic bond.

Towards field detection of polycyclic aromatic hydrocarbons (PAHs) in environment water using a self-assembled SERS sensor

NASA Astrophysics Data System (ADS)

Yan, Xia; Shi, Xiaofeng; Yang, Jie; Zhang, Xu; Jia, Wenjie; Ma, Jun

2017-10-01

A self-assembled surface enhanced Raman scattering (SERS) sensor is reported in this paper. To achieve high sensitivity, a high sensitive SERS substrate and a high efficient self-constructed light path were made. The SERS substrate was composed by gold nanoparticles (AuNPs, pH=13), glycidyl methacrylate-ethylene dimethacrylate (GMA-EDMA) porous material and syringe filter. The substrate had a good repeatability, and the relative standard deviation (RSD) of the same substrate was less than 5%. The efficiency of the self-constructed light path is about two times better than RPB Y type reflection fiber when the energy density was roughly equal on samples. The size of the SERS sensor is 350×300×180 mm and the weight is 15 kg. Its miniaturization and portable can comply with the requirements of field detection. Besides, it has good sensitivity, stability and selectivity. For lab experiments, strong enhancements of Raman scattering from organic pollutant polycyclic aromatic hydrocarbons (PAHs) molecules were exhibited. The dependences of SERS intensities on concentrations of PAHs were investigated, and the results indicated that they revealed a satisfactory linear relationship in low concentrations. The limits of detection (LODs) of PAHs phenanthrene and fluorene are 8.3×10-10 mol/L and 7.1×10-10 mol/L respectively [signal to noise ratio (S/N) =3]. Based on this SERS sensor, signals of benzo (a) pyrene and pyrene were found in environmental water and the sensor would be an ideal candidate for field detection of PAHs.

Characterization, kinetic, and thermodynamic studies of marine pectinase from Bacillus subtilis.

PubMed

Joshi, Manasi; Nerurkar, Madhura; Adivarekar, Ravindra

2015-01-01

Characterization, kinetic and thermodynamic parameters of purified pectinase from Bacillus subtilis, isolated from a marine sediment sample collected from Chinchani beach at Tarapore, India, were studied. Marine pectinase produced under submerged growth conditions was purified by ammonium sulfate precipitation followed by gel filtration chromatography using DEAE cellulose. Partial characterization of the marine pectinase was carried out in terms of effect of pH, temperature, substrate concentration, and metal ions. It was found that pectinase from marine B. subtilis showed maximal activity in alkaline buffer at pH 9.0 and at 40°C. It was also found that metal ions, namely, Mn(2+) and Fe(2+), stimulate pectinase activity. Marine pectinase followed Michaelis-Menten kinetics. The kinetics and thermodynamic parameters of the purified marine pectinase from B. subtilis were studied as the characterization of the enzyme is vital for its use in industrial processes.

Structural and physical properties of InAlAs quantum dots grown on GaAs

NASA Astrophysics Data System (ADS)

Vasile, B. S.; Daly, A. Ben; Craciun, D.; Alexandrou, I.; Lazar, S.; Lemaître, A.; Maaref, M. A.; Iacomi, F.; Craciun, V.

2018-04-01

Quantum dots (QDs), which have particular physical properties due to the three dimensions confinement effect, could be used in many advanced optoelectronic applications. We investigated the properties of InAlAs/AlGaAs QDs grown by molecular beam epitaxy on GaAs/Al0.5Ga0.5As layers. The optical properties of QDs were studied by low-temperature photoluminescence (PL). Two bandgap transitions corresponding to the X-Sh and X-Ph energy structure were observed. The QDs structure was investigated using high-resolution X-ray diffraction (HRXRD) and high-resolution transmission electron microscopy (HRTEM). HRXRD investigations showed that the layers grew epitaxially on the substrate, with no relaxation. HRTEM investigations confirmed the epitaxial nature of the grown structures. In addition, it was revealed that the In atoms aggregated in some prismatic regions, forming areas of high In concentration, that were still in perfect registry with the substrate.

A novel multilayer model with controllable mechanical properties for magnesium-based bone plates.

PubMed

Zhou, Juncen; Huang, Wanru; Li, Qing; She, Zuxin; Chen, Funan; Li, Longqin

2015-04-01

Proper mechanical properties are essential for the clinical application of magnesium-based implants. In the present work, a novel multilayer model composed of three layers with desirable features was developed. The modulus of the multilayer model can be adjusted by changing the thickness of each layer. To combine three layers and improve the corrosion resistance of the whole multilayer model, the polycaprolactone coating was employed. In the immersion test, pH values, the concentration of released magnesium ions, and weight loss indicate that the corrosion rate of multilayer models is considerable lower than that of the one-layer bare substrate. The three-point bending test, which is used to examine models' mechanical properties, shows that the flexural modulus of multilayer models is reduced effectively. In addition, the mechanical degradation of multilayer models is more stable, compared to the one-layer substrate.

A novel type of thermostable alpha-D-glucosidase from Thermoanaerobacter thermohydrosulfuricus exhibiting maltodextrinohydrolase activity.

PubMed Central

Wimmer, B; Lottspeich, F; Ritter, J; Bronnenmeier, K

1997-01-01

An alpha-glucosidase with the ability to attack polymeric substrates was purified to homogeneity from culture supernatants of Thermoanaerobacter thermohydrosulfuricus DSM 567. The enzyme is apparently a glycoprotein with a molecular mass of 160 kDa. Maximal activity is observed between pH5 and 7 at 75 degrees C. The alpha-glucosidase is active towards p-nitrophenyl-alpha-D-glucoside, maltose, malto-oligosaccharides, starch and pullulan. Highest activity is displayed towards the disaccharide maltose. In addition to glucose, maltohexaose and maltoheptaose can be detected as the initial products of starch hydrolysis. After short incubations of pullulan, glucose is found as the only product. At high substrate concentrations, maltose and malto-oligosaccharide, but not glucose, are used as acceptors for glucosyl-transfer. These findings indicate that the T. thermohydrosulfuricus enzyme represents a novel type of alpha-glucosidase exhibiting maltase, glucohydrolase and 'maltodextrinohydrolase' activity. PMID:9371718

Bioactive and Porous Metal Coatings for Improved Tissue Regeneration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, A. A.

Our first objective was to develop the SIM process for the deposition of calcium phosphate films. This process is based on the observation that, in nature, living organisms use macromolecules to control the nucleation and growth of mineral phases. These macromolecules act as templates where various charged functional groups, contained within the molecule, can interact with the ions in the surrounding media, thus stimulating crystal nucleation and growth. Rather than using complex proteins or biopolymers, surface modification schemes were developed to place simple functional groups on the underlying substrate using self-assembling monolayers. Once the substrate was chemically modified, it wasmore » then placed into an aqueous solution containing soluble precursors of the desired mineral coating. Solution pH, ionic concentration and temperature is maintained in a regime where the solution is supersaturated with respect to the desired mineral phase, thereby creating the driving force for nucleation and growth.« less

Surface functionalization of chitosan-coated magnetic nanoparticles for covalent immobilization of yeast alcohol dehydrogenase from Saccharomyces cerevisiae

NASA Astrophysics Data System (ADS)

Li, Gui-yin; Zhou, Zhi-de; Li, Yuan-jian; Huang, Ke-long; Zhong, Ming

2010-12-01

A novel and efficient immobilization of yeast alcohol dehydrogenase (YADH, EC1.1.1.1) from Saccharomyces cerevisiae has been developed by using the surface functionalization of chitosan-coated magnetic nanoparticles (Fe 3O 4/KCTS) as support. The magnetic Fe 3O 4/KCTS nanoparticles were prepared by binding chitosan alpha-ketoglutaric acid (KCTS) onto the surface of magnetic Fe 3O 4 nanoparticles. Later, covalent immobilization of YADH was attempted onto the Fe 3O 4/KCTS nanoparticles. The effect of various preparation conditions on the immobilized YADH process such as immobilization time, enzyme concentration and pH was investigated. The influence of pH and temperature on the activity of the free and immobilized YADH using phenylglyoxylic acid as substrate has also been studied. The optimum reaction temperature and pH value for the enzymatic conversion catalyzed by the immobilized YADH were 30 °C and 7.4, respectively. Compared to the free enzyme, the immobilized YADH retained 65% of its original activity and exhibited significant thermal stability and good durability.

A new amperometric enzyme electrode for alcohol determination.

PubMed

Gülce, H; Gülce, A; Kavanoz, M; Coşkun, H; Yildiz, A

2002-06-01

A new enzyme electrode for the determination of alcohols was developed by immobilizing alcohol oxidase in polvinylferrocenium matrix coated on a Pt electrode surface. The amperometric response due to the electrooxidation of enzymatically generated H(2)O(2) was measured at a constant potential of +0.70 V versus SCE. The effects of substrate, buffer and enzyme concentrations, pH and temperature on the response of the electrode were investigated. The optimum pH was found to be pH 8.0 at 30 degrees C. The steady-state current of this enzyme electrode was reproducible within +/-5.0% of the relative error. The sensitivity of the enzyme electrode decreased in the following order: methanol>ethanol>n-butanol>benzyl alcohol. The linear response was observed up to 3.7 mM for methanol, 3.0 mM for ethanol, 6.2 mM for n-butanol, and 5.2 mM for benzyl alcohol. The apparent Michaelis-Menten constant (K(Mapp)) value and the activation energy, E(a), of this immobilized enzyme system were found to be 5.78 mM and 38.07 kJ/mol for methanol, respectively.

Heat pretreatment eliminates spurious butyrylcholinesterase enhancement of endotoxin levels in the kinetic chromogenic assay.

PubMed

Brawner, Andrew; Hinrichs, Steven H; Larson, Marilynn A; Lockridge, Oksana

2016-04-05

The kinetic chromogenic endotoxin assay measures the release of p-nitroaniline from the chromogenic peptide substrate Ac-IEAR-pNA. As part of our project to purify large quantities of human butyrylcholinesterase (HuBChE), we evaluated pure HuBChE for endotoxin levels. We found that HuBChE contributed up to 90% of the yellow p-nitroaniline product in a standard endotoxin assay through the catalytic hydrolysis of Ac-IEAR-pNA with a rate constant of 0.016 min(-1) and a Km of 2.9 mM in potassium phosphate buffer pH 7.0 at 24 °C. Thus, endotoxin concentrations for native BChE are artificially high in the kinetic chromogenic assay. Destruction of HuBChE catalytic activity by boiling yields endotoxin concentrations that more accurately reflect the endotoxin concentration in purified HuBChE preparations. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

A novel shogaol analog suppresses cancer cell invasion and inflammation, and displays cytoprotective effects through modulation of NF-κB and Nrf2-Keap1 signaling pathways.

PubMed

Gan, Fei-Fei; Ling, Hui; Ang, Xiaohui; Reddy, Shridhivya A; Lee, Stephanie S-H; Yang, Hong; Tan, Sock-Hoon; Hayes, John D; Chui, Wai-Keung; Chew, Eng-Hui

2013-11-01

Natural compounds containing vanilloid and Michael acceptor moieties appear to possess anti-cancer and chemopreventive properties. The ginger constituent shogaol represents one such compound. In this study, the anti-cancer potential of a synthetic novel shogaol analog 3-phenyl-3-shogaol (3-Ph-3-SG) was assessed by evaluating its effects on signaling pathways. At non-toxic concentrations, 3-Ph-3-SG suppressed cancer cell invasion in MDA-MB-231 and MCF-7 breast carcinoma cells through inhibition of PMA-activated MMP-9 expression. At similar concentrations, 3-Ph-3-SG reduced expression of the inflammatory mediators nitric oxide (NO), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and prostanglandin-E2 (PGE2) in RAW 264.7 macrophage-like cells. Inhibition of cancer cell invasion and inflammation by 3-Ph-3-SG were mediated through suppression of the nuclear factor-kappaB (NF-κB) signaling pathway. The 3-Ph-3-SG also demonstrated cytoprotective effects by inducing the antioxidant response element (ARE)-driven genes NAD(P)H quinone oxidoreductase-1 (NQO1) and heme oxygenase-1 (HO-1). Cytoprotection by 3-Ph-3-SG was achieved at least partly through modification of cysteine residues in the E3 ubiquitin ligase substrate adaptor Kelch-like ECH-associated protein 1 (Keap1), which resulted in accumulation of transcription factor NF-E2 p45-related factor 2 (Nrf2). The activities of 3-Ph-3-SG were comparable to those of 6-shogaol, the most abundant naturally-occurring shogaol, and stronger than those of 4-hydroxyl-null deshydroxy-3-phenyl-3-shogaol, which attested the importance of the 4-hydroxy substituent in the vanilloid moiety for bioactivity. In summary, 3-Ph-3-SG is shown to possess activities that modulate stress-associated pathways relevant to multiple steps in carcinogenesis. Therefore, it warrants further investigation of this compound as a promising candidate for use in chemotherapeutic and chemopreventive strategies. © 2013.

Biotransformation of menadione to its prenylated derivative MK-3 using recombinant Pichia pastoris.

PubMed

Li, Zhemin; Zhao, Genhai; Liu, Hui; Guo, Yugang; Wu, Hefang; Sun, Xiaowen; Wu, Xihua; Zheng, Zhiming

2017-07-01

Prenylated quinones, especially menaquinones, have significant physiological activities, but are arduous to synthesize efficiently. Due to the relaxed aromatic substrate specificity and prenylation regiospecificity at the ortho- site of the phenolic hydroxyl group, the aromatic prenyltransferase NovQ from Streptomyces may be useful in menaquinone synthesis from menadione. In this study, NovQ was overexpressed in Pichia pastoris. After fermentation optimization, NovQ production increased by 1617%. Then the different effects of metal ions, detergents and pH on the activity of purified NovQ were investigated to optimize the prenylation reaction. Finally, purified NovQ and cells containing NovQ were used for menadione prenylation in vitro and in vivo, respectively. Menaquinone-1 (MK-1) was detected as the only product in vitro with γ,γ-dimethylallyl pyrophosphate and menadione hydroquinol substrates. MK-3 at a concentration of 90.53 mg/L was detected as the major product of whole cell catalysis with 3-methyl-2-buten-1-ol and menadione hydroquinol substrates. This study realized whole cell catalysis converting menadione to menaquinones.

Natronotalea proteinilytica gen. nov., sp. nov. and Longimonas haloalkaliphila sp. nov., extremely haloalkaliphilic members of the phylum Rhodothermaeota from hypersaline alkaline lakes.

PubMed

Sorokin, Dimitry Y; Khijniak, Tatiana V; Galinski, Erwin A; Kublanov, Ilya V

2017-10-01

Two proteolytic bacterial strains, BSker2 T and BSker3 T , were enriched from sediments of hypersaline alkaline lakes in Kulunda Steppe (Altai, Russia) with chicken feathers as substrate, followed by pure culture isolation on hypersaline alkaline media with casein. The cells were non-motile, filamentous, flexible rods. The isolates were obligately aerobic heterotrophs utilizing proteins and peptides as growth substrates. Both were obligate alkaliphiles, but differed in their pH optimum for growth: pH 9.5-9.8 for Bsker2 T and pH 8.5-8.8 for BSker3 T . The salt range for growth of both isolates was between 2 and 4.5 M total Na + with an optimum at 2.5-3 M. No organic osmolytes were detected in cells of BSker2 T , but they accumulated high intracellular concentrations of K + . The polar lipid fatty acids were dominated by unsaturated C16 and C18 species. The 16S rRNA gene phylogeny indicated that both strains belong to the recently proposed phylum Rhodothermaeota. BSker2 T forms a novel genus-level branch, while BSker3 T represents a novel species-level member in the genus Longimonas. On the basis of distinct phenotypic and genotypic properties, strain BSker2 T (=JCM 31342 T =UNIQEM U1009 T ) is proposed to be classified as a representative of a novel genus and species, Natronotalea proteinilyticagen. nov., sp. nov., and strain BSker3 T (=JCM 31343 T =UNIQEM U1010 T ) as a representative of a novel species, Longimonas haloalkaliphila sp. nov.

Agricultural effluent treatment in biobed systems using novel substrates from southeastern Mexico: the relationship with physicochemical parameters of biomixtures.

PubMed

Góngora-Echeverría, Virgilio René; Martin-Laurent, Fabrice; Quintal-Franco, Carlos; Giácoman-Vallejos, German; Ponce-Caballero, Carmen

2017-04-01

Misuse of pesticides in farming activities leads to contamination of drinking water sources and is responsible for animal and human health problems. The biobeds are practicable option to minimize contamination by pesticides during preparation, use and washing of equipment for pesticide treatments. This research aimed at testing substrate mixtures to optimize biobed efficiency to remove pesticides under the climate of the Yucatan (México). Agricultural soil and 11 mixtures adding vegetable compost, sisal pulp, corn stover and seaweed were tested under controlled conditions. Each biomixture was exposed to a mixture of five pesticides (2,4-diclorophenoxyacetic acid "2,4-D" [1.08 mg cm -3 ], atrazine [2.50 mg cm -3 ], carbofuran [0.23 mg cm -3 ], diazinon [0.34 mg cm -3 ], and glyphosate [0.36 mg cm -3 ]) in a period of 41 days. Monitoring of the dissipation of pesticide residues showed that pesticides were quickly dissipated in soil at microcosm level experiment, while at two critical times of 20 and 41 days, all mixtures of substrates (biomixtures) were efficient in dissipation of high concentrations of pesticide in a short time (>99%). Time, biomixture and type of pesticide were shown to be the main parameters influencing pesticide dissipation (P < 0.05). Several other physicochemical parameters of the biomixtures, such as organic matter (OM), lignin, water holding capacity (WHC), and pH, were also significant on pesticide dissipation (P < 0.05), being pH the most significant.

Surface-texture evolution of different chemical-vapor-deposited zinc sulfide flats polished with various magnetorheological fluids

DOE PAGES

Salzman, S.; Romanofsky, H. J.; Jacobs, S. D.; ...

2015-08-19

The macro-structure of chemical-vapor-deposited (CVD) zinc sulfide (ZnS) substrates is characterizedby cone-like structures that start growing at the early stages of deposition. As deposition progresses,these cones grow larger and reach centimeter size in height and millimeter size in width. It is challengingto polish out these features from the top layer, particularly for the magnetorheological finishing (MRF)process. A conventional MR fluid tends to leave submillimeter surface artifacts on the finished surface,which is a direct result of the cone-like structure. Here we describe the MRF process of polishing four CVD ZnS substrates, manufactured by four differentvendors, with conventional MR fluid at pHmore » 10 and zirconia-coated-CI (carbonyl iron) MR fluids at pH 4, 5,and 6. We report on the surface–texture evolution of the substrates as they were MRF polished with thedifferent fluids. We show that performances of the zirconia-coated-CI MR fluid at pH 4 are significantlyhigher than that of the same fluid at pH levels of 5 and 6 and moderately higher than that of a conventionalMR fluid at pH 10. An improvement in surface–texture variability from part to part was also observedwith the pH 4 MR fluid.« less

Molecular mechanism of pH-dependent substrate transport by an arginine-agmatine antiporter.

PubMed

Wang, Sheng; Yan, Renhong; Zhang, Xi; Chu, Qi; Shi, Yigong

2014-09-02

Enteropathogenic bacteria, exemplified by Escherichia coli, rely on acid-resistance systems (ARs) to survive the acidic environment of the stomach. AR3 consumes intracellular protons through decarboxylation of arginine (Arg) in the cytoplasm and exchange of the reaction product agmatine (Agm) with extracellular Arg. The latter process is mediated by the Arg:Agm antiporter AdiC, which is activated in response to acidic pH and remains fully active at pH 6.0 and below. Despite our knowledge of structural information, the molecular mechanism by which AdiC senses acidic pH remains completely unknown. Relying on alanine-scanning mutagenesis and an in vitro proteoliposome-based transport assay, we have identified Tyr74 as a critical pH sensor in AdiC. The AdiC variant Y74A exhibited robust transport activity at all pH values examined while maintaining stringent substrate specificity for Arg:Agm. Replacement of Tyr74 by Phe, but not by any other amino acid, led to the maintenance of pH-dependent substrate transport. These observations, in conjunction with structural information, identify a working model for pH-induced activation of AdiC in which a closed conformation is disrupted by cation-π interactions between proton and the aromatic side chain of Tyr74.

Growth rate characteristics of acidophilic heterotrophic organisms from mine waste rock piles

NASA Astrophysics Data System (ADS)

Yacob, T. W.; Silverstein, J.; Jenkins, J.; Andre, B. J.; Rajaram, H.

2010-12-01

Autotrophic iron oxidizing bacteria play a key role in pyrite oxidation and generation of acid mine drainage AMD. Scarcity of organic substrates in many disturbed sites insures that IOB have sufficient oxygen and other nutrients for growth. It is proposed that addition of organic carbon substrate to waste rock piles will result in enrichment of heterotrophic microorganisms limiting the role of IOB in AMD generation. Previous researchers have used the acidophilic heterotroph Acidiphilium cryptum as a model to study the effects of organic substrate addition on the pyrite oxidation/AMD cycle. In order to develop a quantitative model of effects such as competition for oxygen, it is necessary to use growth and substrate consumption rate expressions, and one approach is to choose a model strain such as A. cryptum for kinetic studies. However we have found that the growth rate characteristics of A. cryptum may not provide an accurate model of the remediation effects of organic addition to subsurface mined sites. Fluorescent in-situ hybridization (FISH) assays of extracts of mine waste rock enriched with glucose and yeast extract did not produce countable numbers of cells in the Acidiphilium genus, with a detection limit of3 x 104 cells/gram rock, despite evidence of the presence of well established heterotrophic organisms. However, an MPN enrichment produced heterotrophic population estimates of 1x107 and 1x109 cells/gram rock. Growth rate studies of A. cryptum showed that cultures took 120 hours to degrade 50% of an initial glucose concentration of 2,000 mg/L. However a mixed culture enriched from mine waste rock consumed 100% of the same amount of glucose in 24 hours. Substrate consumption data for the mixed culture were fit to a Monod growth model: {dS}/{dt} = μ_{max}S {( {X_0}/{Y} + S_0 -S )}/{(K_s +S)} Kinetic parameters were estimated utilizing a non linear regression method coupled with an ODE solver. The maximum specific growth rate of the mixed population with μ max was calculated to be 0.13 hr-1 and a yield of 0.52 g cells/g glucose and Ks of 0.2 g/L glucose. The effect of pH on growth was compared for A. cryptum and the mixed population. It was found that the mixed culture had a higher tolerance for extremely low pH conditions, with no growth at pH = 1; whereas no growth of A cryptum was observed at pH = 1.5. Both A. cryptum and the mixed cultures grew within a pH range of 2.5 - 6. A phospholipid fatty acid analysis (PLFA) of the mixed culture indicated that both eukaryotic and prokaryotic organisms are present at a ratio of approximately 1:1, indicating that organisms such as fungi may be important in carbon cycling in these acidic subsurface formations. The results from this research show that utilization of mixed wild cultures for environmental modeling may yield better results than selection of a single strain to represent populations in a quantitative model.

Initial steps of the peroxidase-catalyzed polymerization of coniferyl alcohol and/or sinapyl aldehyde: capillary zone electrophoresis study of pH effect.

PubMed

Fournand, David; Cathala, Bernard; Lapierre, Catherine

2003-01-01

Capillary zone electrophoresis has been used to monitor the first steps of the dehydrogenative polymerization of coniferyl alcohol, sinapyl aldehyde, or a mixture of both, catalyzed by the horseradish peroxidase (HRP)-H(2)O(2) system. When coniferyl alcohol was the unique HRP substrate, three major dimers were observed (beta-5, beta-beta, and beta-O-4 interunit linkages) and their initial formation velocity as well as their relative abundance varied with pH. The beta-O-4 interunit linkage was thus slightly favored at lower pH values. In contrast, sinapyl aldehyde turned out to be a very poor substrate for HRP except in basic conditions (pH 8). The major dimer observed was the beta,beta'-di-sinapyl aldehyde, a red-brown exhibiting compound which might partly participate in the red coloration usually observed in cinnamyl alcohol dehydrogenase-deficient angiosperms. Finally, when a mixture of coniferyl alcohol and sinapyl aldehyde was used, it looked as if sinapyl aldehyde became a very good substrate for HRP. Indeed, coniferyl alcohol turned out to serve as a redox mediator (i.e. "shuttle oxidant") for the sinapyl aldehyde incorporation in the lignin-like polymer. This means that in particular conditions the specificity of oxidative enzymes might not hinder the incorporation of poor substrates into the growing lignin polymer.

In vitro activity of minimised hammerhead ribozymes.

PubMed Central

Hendry, P; McCall, M J; Santiago, F S; Jennings, P A

1995-01-01

A number of minimised hammerhead ribozymes (minizymes) which lack stem II have been kinetically characterised. These minizymes display optimal cleavage activity at temperatures around 37 degrees C. The cleavage reactions of the minizymes are first order in hydroxide ion concentration up to around pH 9.3 above which the cleavage rate constants decline rapidly. The reactions show a biphasic dependence on magnesium-ion concentration; one of the interactions has an apparent dissociation constant of around 20 mM while the other appears to be very weak, showing no sign of saturation at 200 mM MgCl2. The minizymes are significantly less active than comparable, full-size ribozymes when cleaving short substrates. However, at a particular site in a transcribed TAT gene from HIV-1, minizymes are more effective than ribozymes. PMID:7479037

The production and growth characteristics of yeast and mycelial forms of Candida albicans in continuous culture.

PubMed

Shepherd, M G; Sullivan, P A

1976-04-01

The growth characteristics of Candida albicans CM145,348 have been examined under aerobic conditions in continuous culture. At different steady states the environment was controlled with respect to the concentrations of dissolved oxygen, carbon and nitrogen, the pH, and the temperature. Dry matter, substrate concentration, yield, specific oxygen uptake, specific carbon dioxide release and respiration quotient were examined as a function of the dilution rate. The morphology depended on the carbon source. Maltose produced a mycelial morphology, whereas with lactate a yeast culture was obtained. With fructose or glucose as a carbon source a mixed morphology of yeast, pseudo-mycelial and mycelial forms was produced. A larger number of different growth conditions were examined in batch culture but a mixed morphology was always obtained.

Phospholipase B activity of a purified phospholipase A from Vipera palestinae venom.

PubMed

Shiloah, J; Klibansky, C; de Vries, A; Berger, A

1973-05-01

Phospholipase was isolated (in two fractions) from Vipera palestinae venom and it was shown to possess phospholipase A activity (hydrolyzing diacyl-sn-glycerophosphorylcholines, e.g., lecithin, in the 2-position) as well as lysophospholipase (phospholipase B) activity (hydrolyzing 1-monoacyl-sn-glycerophosphorylcholines, e.g., lysolecithin, yielding free fatty acid and glycerophosphorylcholine). Each of the two purified enzyme fractions was homogeneous as judged by electrophoresis on acrylamide gel and by immunodiffusion and immunoelectrophoresis, and both had essentially equal activities. The ratio of the specific activity, at various purification stages, to the specific activity of the whole venom was the same for A activity (substrate lecithin) as for B activity (substrate lysolecithin). The enzyme has a molecular weight of 16,000, six S-S bridges, and no free thiol groups. At pH 7, dimerization was observed in the ultracentrifuge. A dissociation constant of about 10(-5) m was estimated. The amino acid composition for both fractions (140 amino acid residues) was found to be essentially the same. The A activity had a pH optimum at 9; B activity was low at this pH but increased steadily beyond pH 10.5. For the hydrolysis of lysolecithin the Lineweaver-Burk plot was found to be linear, giving K(m) = 1.1 mm and k(cat) = 0.55 sec(-1) at 37 degrees C and pH 10. 2-Deoxylysolecithin was also hydrolyzed by the enzyme at pH 10, with k(cat) = 0.01 sec(-1) (zero-order kinetics in the range 0.5-2.5 mm). For lecithin these constants could not be determined, but at 0.25 mm substrate the hydrolysis rate (at pH 9) of lecithin was about 1000 times the hydrolysis rate of lysolecithin (at pH 10).

An Optical Sensor with Polyaniline-Gold Hybrid Nanostructures for Monitoring pH in Saliva.

PubMed

Luo, Chongdai; Wang, Yangyang; Li, Xuemeng; Jiang, Xueqin; Gao, Panpan; Sun, Kang; Zhou, Jianhua; Zhang, Zhiguang; Jiang, Qing

2017-03-17

Saliva contains important personal physiological information that is related to some diseases, and it is a valuable source of biochemical information that can be collected rapidly, frequently, and without stress. In this article, we reported a new and simple localized surface plasmon resonance (LSPR) substrate composed of polyaniline (PANI)-gold hybrid nanostructures as an optical sensor for monitoring the pH of saliva samples. The overall appearance and topography of the substrates, the composition, and the wettability of the LSPR surfaces were characterized by optical and scanning electron microscope (SEM) images, infrared spectra, and contact angles measurement, respectively. The PANI-gold hybrid substrate readily responded to the pH. The response time was very short, which was 3.5 s when the pH switched from 2 to 7, and 4.5 s from 7 to 2. The changes of visible-near-infrared (NIR) spectra of this sensor upon varying pH in solution showed that-for the absorption at given wavelengths of 665 nm and 785 nm-the sensitivities were 0.0299 a.u./pH (a.u. = arbitrary unit) with a linear range of pH = 5-8 and 0.0234 a.u./pH with linear range of pH = 2-8, respectively. By using this new sensor, the pH of a real saliva sample was monitored and was consistent with the parallel measurements with a standard laboratory method. The results suggest that this novel LSPR sensor shows great potential in the field of mobile healthcare and home medical devices, and could also be modified by different sensitive materials to detect various molecules or ions in the future.

Variation in pH optima of hydrolytic enzyme activities in tropical rain forest soils.

PubMed

Turner, Benjamin L

2010-10-01

Extracellular enzymes synthesized by soil microbes play a central role in the biogeochemical cycling of nutrients in the environment. The pH optima of eight hydrolytic enzymes involved in the cycles of carbon, nitrogen, phosphorus, and sulfur, were assessed in a series of tropical forest soils of contrasting pH values from the Republic of Panama. Assays were conducted using 4-methylumbelliferone-linked fluorogenic substrates in modified universal buffer. Optimum pH values differed markedly among enzymes and soils. Enzymes were grouped into three classes based on their pH optima: (i) enzymes with acidic pH optima that were consistent among soils (cellobiohydrolase, β-xylanase, and arylsulfatase), (ii) enzymes with acidic pH optima that varied systematically with soil pH, with the most acidic pH optima in the most acidic soils (α-glucosidase, β-glucosidase, and N-acetyl-β-glucosaminidase), and (iii) enzymes with an optimum pH in either the acid range or the alkaline range depending on soil pH (phosphomonoesterase and phosphodiesterase). The optimum pH values of phosphomonoesterase were consistent among soils, being 4 to 5 for acid phosphomonoesterase and 10 to 11 for alkaline phosphomonoesterase. In contrast, the optimum pH for phosphodiesterase activity varied systematically with soil pH, with the most acidic pH optima (3.0) in the most acidic soils and the most alkaline pH optima (pH 10) in near-neutral soils. Arylsulfatase activity had a very acidic optimum pH in all soils (pH ≤3.0) irrespective of soil pH. The differences in pH optima may be linked to the origins of the enzymes and/or the degree of stabilization on solid surfaces. The results have important implications for the interpretation of hydrolytic enzyme assays using fluorogenic substrates.

Waste isolation safety assessment program. Task 4. Collection and generation of transport data theoretical and experimental evaluation of waste transport in selected rocks. Annual progress report, October 1, 1978-September 30, 1979

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silva, R.J.; Benson, L.V.; Yee, A.W.

1979-09-30

The objective of the program is to establish a basis for the prediction of radionuclide sorption in geologic environments. In FY 79, experimental and theoretical efforts were concentrated on a study of the sorption of cesium on the solid substrates Min-u-sil (quartz) and Belle Fourche clay (montmorillonite). Cesium sorption isotherms were obtained for the two substrates at 26/sup 0/C as a function of initial Cs concentration in solution (10/sup -3/M to 10/sup -9/M), pH (5 to 10) and supporting electrolyte concentration (0.002M, 0.01M, 0.1M, and 1M) NaCl and a simulated basalt groundwater in batch-type experiments using crushed material. Characterization ofmore » the solid phases included measurements of chemical compositions, particle sizes, surface areas, and cation-exchange capacities. In addition, potentiometric acid/base titrations of the solid phases were conducted in order to determine the acid dissociation and electrolyte exchange constants of the surfaces. Preliminary analysis of the sorption data indicate that while the clay data could be explained by simple mass-action expressions, the quartz data could not. Theoretical efforts were aimed at developing and testing an electrolyte binding electrical double-layer model to predict sorption isotherms. A computerized version of the model, MINEQL, which simultaneously considers surface and solution chemical equilibria, was brought to operational status. Input parameters required by MINEQL were determined and sorption isotherms for Cs on the Belle Fourche clay were calculated over the same range of parameters as the experimental measurements. Comparisons showed that the model was able to simulate the isotherms quite well except at the lowest pH values for the 0.002M and 0.01M NaCl solutions.« less

A Lipoxygenase from Red Alga Pyropia haitanensis, a Unique Enzyme Catalyzing the Free Radical Reactions of Polyunsaturated Fatty Acids with Triple Ethylenic Bonds

PubMed Central

Zhu, Zhujun; Qian, Feijian; Yang, Rui; Chen, Juanjuan; Luo, Qijun; Chen, Haimin; Yan, Xiaojun

2015-01-01

Lipoxygenases (LOXs) are key enzymes to regulate the production of hormones and defensive metabolites in plants, animals and algae. In this research, a full length LOX gene has been cloned and expressed from the red alga Pyropia haitanensis (Bangiales, Rhodophyta) gametophyte (PhLOX2). Subsequent phylogenetic analysis showed that such LOX enzymes are separated at the early stage of evolution, establishing an independent branch. The LOX activity was investigated at the optimal pH of 8.0. It appears that PhLOX2 is a multifunctional enzyme featuring both lipoxygenase and hydroperoxidase activities. Additionally, PhLOX2 exhibits remarkable substrate and position flexibility, and it can catalyze an array of chemical reactions involving various polyunsaturated fatty acids, ranging from C18 to C22. As a matter of fact, mono-hydroperoxy, di-hydroperoxy and hydroxyl products have been obtained from such transformations, and eicosapentaenoic acid seem to be the most preferred substrate. It was found that at least triple ethylenic bonds are required for PhLOX2 to function as a LOX, and the resulting hydroxy products should be originated from the PhLOX2 mediated reduction of mono-hydroperoxides, in which the hydrogen abstraction occurs on the carbon atom between the second and third double bond. Most of the di-hydroperoxides observed seem to be missing their mono-position precursors. The substrate and position flexibility, as well as the function versatility of PhLOXs represent the ancient enzymatic pathway for organisms to control intracellular oxylipins. PMID:25658744

Kinetics and yields of pesticide biodegradation at low substrate concentrations and under conditions restricting assimilable organic carbon.

PubMed

Helbling, Damian E; Hammes, Frederik; Egli, Thomas; Kohler, Hans-Peter E

2014-02-01

The fundamentals of growth-linked biodegradation occurring at low substrate concentrations are poorly understood. Substrate utilization kinetics and microbial growth yields are two critically important process parameters that can be influenced by low substrate concentrations. Standard biodegradation tests aimed at measuring these parameters generally ignore the ubiquitous occurrence of assimilable organic carbon (AOC) in experimental systems which can be present at concentrations exceeding the concentration of the target substrate. The occurrence of AOC effectively makes biodegradation assays conducted at low substrate concentrations mixed-substrate assays, which can have profound effects on observed substrate utilization kinetics and microbial growth yields. In this work, we introduce a novel methodology for investigating biodegradation at low concentrations by restricting AOC in our experiments. We modified an existing method designed to measure trace concentrations of AOC in water samples and applied it to systems in which pure bacterial strains were growing on pesticide substrates between 0.01 and 50 mg liter(-1). We simultaneously measured substrate concentrations by means of high-performance liquid chromatography with UV detection (HPLC-UV) or mass spectrometry (MS) and cell densities by means of flow cytometry. Our data demonstrate that substrate utilization kinetic parameters estimated from high-concentration experiments can be used to predict substrate utilization at low concentrations under AOC-restricted conditions. Further, restricting AOC in our experiments enabled accurate and direct measurement of microbial growth yields at environmentally relevant concentrations for the first time. These are critical measurements for evaluating the degradation potential of natural or engineered remediation systems. Our work provides novel insights into the kinetics of biodegradation processes and growth yields at low substrate concentrations.

A model to assess lactic acid bacteria aminopeptidase activities in Parmigiano Reggiano cheese during ripening.

PubMed

Gatti, M; De Dea Lindner, J; Gardini, F; Mucchetti, G; Bevacqua, D; Fornasari, M E; Neviani, E

2008-11-01

The aim of this work was to investigate in which phases of ripening of Parmigiano Reggiano cheese lactic acid bacteria aminopeptidases present in cheese extract could be involved in release of free amino acids and to better understand the behavior of these enzymes in physical-chemical conditions that are far from their optimum. In particular, we evaluated 6 different substrates to reproduce broad-specificity aminopeptidase N, broad-specificity aminopeptidase C, glutamyl aminopeptidase A, peptidase with high specificity for leucine and alanine, proline iminopeptidase, and X-prolyl dipeptidyl aminopeptidase activities releasing different N-terminal amino acids. The effects of pH, NaCl concentration, and temperature on the enzyme activities of amino acid beta-naphthylamide (betaNA)-substrates were determined by modulating the variables in 19 different runs of an experimental design, which allowed the building of mathematical models able to assess the effect on aminopeptidases activities over a range of values, obtained with bibliographic data, covering different environmental conditions in different zones of the cheese wheel at different aging times. The aminopeptidases tested in this work were present in cell-free Parmigiano Reggiano cheese extract after a 17-mo ripening and were active when tested in model system. The modeling approach shows that to highlight the individual and interactive effects of chemical-physical variables on enzyme activities, it is helpful to determine the true potential of an amino-peptidase in cheese. Our results evidenced that the 6 different lactic acid bacteria peptidases participate in cheese proteolysis and are induced or inhibited by the cheese production parameters that, in turn, depend on the cheese dimension. Generally, temperature and pH exerted the more relevant effects on the enzymatic activities, and in many cases, a relevant interactive effect of these variables was observed. Increasing salt concentration slowed down broad-specificity amino-peptidase C, glutamyl aminopeptidase A, proline iminopeptidase, and peptidase with high specificity for leucine and alanine. Interestingly, this variable did not affect broad-specificity aminopeptidase N and positively affected X-prolyl dipeptidyl aminopeptidase. The models elaborated varying pH, temperatures, and salt concentration and were a useful, low cost, and fast tool to understand the role of the main peptidases in the different phases of cheese ripening in relation to the major environmental factors influencing enzyme activity.

The Effects of ph on Structural and Optical Characterization of Iron Oxide Thin Films

NASA Astrophysics Data System (ADS)

Tezel, Fatma Meydaneri; Özdemir, Osman; Kariper, I. Afşin

In this study, the iron oxide thin films have been produced by chemical bath deposition (CBD) method as a function of pH onto amorphous glass substrates. The surface images of the films were investigated with scanning electron microscope (SEM). The crystal structures, orientation of crystallization, crystallite sizes, and dislocation density i.e. structural properties of the thin films were analyzed with X-ray diffraction (XRD). The optical band gap (Eg), optical transmission (T%), reflectivity (R%), absorption coefficient (α), refraction index (n), extinction coefficient (k) and dielectric constant (ɛ) of the thin films were investigated depending on pH, deposition time, solution temperature, substrate temperature, thickness of the films by UV-VIS spectrometer.

Optimization of the Production of 1-Phenylethanol Using Enzymes from Flowers of Tea (Camellia sinensis) Plants.

PubMed

Dong, Fang; Zhou, Ying; Zeng, Lanting; Watanabe, Naoharu; Su, Xinguo; Yang, Ziyin

2017-01-13

1-Phenylethanol (1PE) can be used as a fragrance in food flavoring and cosmetic industries and as an intermediate in the pharmaceutical industry. 1PE can be synthesized from acetophenone, and the cost of 1PE is higher than the cost of acetophenone. Therefore, it is important to establish an effective and low-cost approach for producing 1PE. Our previous studies found that tea ( Camellia sinensis ) flowers, which are an abundant and waste resource, contained enzymes that could transform acetophenone to 1PE. In the present study, we extracted crude enzymes from tea flowers and optimized the production conditions of 1PE using response surface methodology. The optimized conditions were an extraction pH of 7.0, a reaction pH of 5.3, a reaction temperature of 55 °C, a reaction time of 100 min, a coenzyme NADPH concentration of 3.75 μmol/mL in the reaction assay, and a substrate acetophenone concentration of 1.25 μmol/mL in the reaction assay. The results provide essential information for future industrial 1PE production using plant-derived enzymes.

Production of antioxidant compounds of grape seed skin by fermentation and its optimization using response surface method

NASA Astrophysics Data System (ADS)

Andayani, D. G. S.; Risdian, C.; Saraswati, V.; Primadona, I.; Mawarda, P. C.

2017-03-01

Skins and seeds of grape are waste generated from food industry. These wastes contain nutrients of which able to be utilized as an important source for antioxidant metabolite production. Through an environmentally friendly process, natural antioxidant material was produced. This study aimed to generate antioxidant compounds by liquid fermentation. Optimization was carried out by using Schizosaccharomyces cerevisiae in Katu leaf substrate. Optimization variables through response surface methodology (RSM) were of sucrose concentration, skins and seeds of grape concentration, and pH. Results showed that the optimum conditions for antioxidant production were of 5 g/L sucrose, 5 g/L skins and seed at pH 5, respectively. The resulted antioxidant activity was of 1.62 mg/mL. Mathematical model of variance analysis using a second order polynomial corresponding to the resulted data for the antioxidant was of 20.70124 - 3.86997 A - 0.65996 B - 1.88367 C + 0.19634 A2 - 0.016638 B2 + 0.28848 C2 + 0.26980 AB - 0.068333 AC - 0.12367 BC. From the gained equation, the optimum yield from all variables was significant. Chemical analysis of the antioxidant was carried out using 2,2-Diphenyl-1-picrylhydrazyl (DPPH).

Precise method for the measurement of catalase activity in honey.

PubMed

Huidobro, José F; Sánchez, M Pilar; Muniategui, Soledad; Sancho, M Teresa

2005-01-01

An improved method is reported for the determination of catalase activity in honey. We tested different dialysis membranes, dialysis fluid compositions and amounts, dialysis temperatures, sample amounts, and dialysis times. The best results were obtained by dialysis of 7.50 g sample in a cellulose dialysis sack, using two 3 L portions of 0.015 M sodium phosphate buffer (pH 7.0) as the dialysis fluid at 4 degrees C for 22 h. As in previous methods, catalase activity was determined on the basis of the rate of disappearance of the substrate, H202, with the H202 determined spectrophotometrically at 400 nm in an assay system containing o-dianisidine and peroxidase. Trials indicated that the best solvent for the o-dianisidine was 0.2 M sodium phosphate buffer, pH 6.1; the best starting H202 concentration was 3 mM; the best HCl concentration for stopping the reaction was 6 N; and the best sample volume for catalase measurement was 7.0 mL. Precision values (relative standard deviations for analyses of 10 subsamples of each of 3 samples) were high, ranging from 0.48% for samples with high catalase activity to 1.98% for samples with low catalase activity.

Carbon monoxide photoproduction: implications for photoreactivity of Arctic permafrost-derived soil dissolved organic matter.

PubMed

Hong, Jun; Xie, Huixiang; Guo, Laodong; Song, Guisheng

2014-08-19

Apparent quantum yields of carbon monoxide (CO) photoproduction (AQY(CO)) for permafrost-derived soil dissolved organic matter (SDOM) from the Yukon River Basin and Alaska coast were determined to examine the dependences of AQY(CO) on temperature, ionic strength, pH, and SDOM concentration. SDOM from different locations and soil depths all exhibited similar AQY(CO) spectra irrespective of soil age. AQY(CO) increased by 68% for a 20 °C warming, decreased by 25% from ionic strength 0 to 0.7 mol L(-1), and dropped by 25-38% from pH 4 to 8. These effects combined together could reduce AQY(CO) by up to 72% when SDOM transits from terrestrial environemnts to open-ocean conditions during summer in the Arctic. A Michaelis-Menten kinetics characterized the influence of SDOM dilution on AQY(CO) with a very low substrate half-saturation concentration. Generalized global-scale relationships between AQY(CO) and salinity and absorbance demostrate that the CO-based photoreactivity of ancient permaforst SDOM is comparable to that of modern riverine DOM and that the effects of the physicochemical variables revealed here alone could account for the seaward decline of AQY(CO) observed in diverse estuarine and coastal water bodies.

Distance-dependent varieties of microbial community structure and metabolic functions in the rhizosphere of Sedum alfredii Hance during phytoextraction of a cadmium-contaminated soil.

PubMed

Yang, Wenhao; Zhang, Taoxiang; Lin, Sen; Ni, Wuzhong

2017-06-01

The recovery of microbial community and activities is crucial to the remediation of contaminated soils. Distance-dependent variations of microbial community composition and metabolic characteristics in the rhizospheric soil of hyperaccumulator during phytoextraction are poorly understood. A 12-month phytoextraction experiment with Sedum alfredii in a Cd-contaminated soil was conducted. A pre-stratified rhizobox was used for separating sub-layer rhizospheric (0-2, 2-4, 4-6, 6-8, 8-10 mm from the root mat)/bulk soils. Soil microbial structure and function were analyzed by phospholipid fatty acid (PLFA) and MicroResp™ methods. The concentrations of total and specified PLFA biomarkers and the utilization rates for the 14 substrates (organic carbon) in the 0-2-mm sub-layer rhizospheric soil were significantly increased, as well as decreased with the increase in the distance from the root mat. Microbial structure measured by the ratios of different groups of PLFAs such as fungal/bacterial, monounsaturated/saturated, ratios of Gram-positive to Gram-negative (GP/GN) bacterial, and cyclopropyl/monoenoic precursors and 19:0 cyclo/18:1ω7c were significantly changed in the 0-2-mm soil. The PLFA contents and substrate utilization rates were negatively correlated with pH and total, acid-soluble, and reducible fractions of Cd, while positively correlated with labile carbon. The dynamics of microbial community were likely due to root exudates and Cd uptake by S. alfredii. This study revealed the stimulations and gradient changes of rhizosphere microbial community through phytoextraction, as reduced Cd concentration, pH, and increased labile carbons are due to the microbial community responses.

Synthesis of the Galactosyl Derivative of Gluconic Acid With the Transglycosylation Activity of β-Galactosidase

PubMed Central

2017-01-01

Summary Bionic acids are bioactive compounds demonstrating numerous interesting properties. They are widely produced by chemical or enzymatic oxidation of disaccharides. This paper focuses on the galactosyl derivative of gluconic acid as a result of a new method of bionic acid synthesis which utilises the transglycosylation properties of β-galactosidase and introduces lactose as a substrate. Products obtained in such a process are characterised by different structures (and, potentially, properties) than those resulting from traditional oxidation of disaccharides. The aim of this study is to determine the effect of selected parameters (concentration and ratio of substrates, dose of the enzyme, time, pH, presence of salts) on the course of the reaction carried out with the enzymatic preparation Lactozym, containing β-galactosidase from Kluyveromyces lactis. Research has shown that increased dry matter content in the baseline solution (up to 50%, by mass per volume) and an addition of NaCl contribute to higher yield. On the other hand, reduced content of the derivative is a result of increased pH from 7.0 to 9.0 and an addition of magnesium and manganese salts. Moreover, exceeding the β-galactosidase dose over approx. 35 000 U per 100 g of lactose also leads to reduced yield of the process. The most favourable molar ratio of sodium gluconate to lactose is 2.225:0.675. Depending on the conditions of the synthesis, the product concentration ranged between 17.3 and 118.3 g/L of the reaction mixture, which corresponded to the mass fraction of 6.64–23.7% of dry matter. The data obtained as a result of the present study may be useful for designing an industrial process. PMID:28867957

Bioremediation of Acidic and Metalliferous Drainage (AMD) through organic carbon amendment by municipal sewage and green waste.

PubMed

McCullough, Clint D; Lund, Mark A

2011-10-01

Pit lakes (abandoned flooded mine pits) represent a potentially valuable water resource in hot arid regions. However, pit lake water is often characterised by low pH with high dissolved metal concentrations resulting from Acidic and Metalliferous Drainage (AMD). Addition of organic matter to pit lakes to enhance microbial sulphate reduction is a potential cost effective remediation strategy. However, cost and availability of suitable organic substrates are often limiting. Nevertheless, large quantities of sewage and green waste (organic garden waste) are often available at mine sites from nearby service towns. We treated AMD pit lake water (pH 2.4) from tropical, North Queensland, Australia, with primary-treated sewage sludge, green waste, and a mixture of sewage and green waste (1:1) in a controlled microcosm experiment (4.5 L). Treatments were assessed at two different rates of organic loading of 16:1 and 32:1 pit water:organic matter by mass. Combined green waste and sewage treatment was the optimal treatment with water pH increased to 5.5 in only 145 days with decreases of dissolved metal concentrations. Results indicated that green waste was a key component in the pH increase and concomitant heavy metal removal. Water quality remediation was primarily due to microbially-mediated sulphate reduction. The net result of this process was removal of sulphate and metal solutes to sediment mainly as monosulfides. During the treatment process NH(3) and H(2)S gases were produced, albeit at below concentrations of concern. Total coliforms were abundant in all green waste-treatments, however, faecal coliforms were absent from all treatments. This study demonstrates addition of low-grade organic materials has promise for bioremediation of acidic waters and warrants further experimental investigation into feasibility at higher scales of application such as pit lakes. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

Enzymatic synthesis of 3-O-α-maltosyl-l-ascorbate using an engineered cyclodextrin glucanotransferase.

PubMed

Ahn, Hee-Jeong; Li, Chao; Cho, Hye-Bin; Park, Sunghoon; Chang, Pahn-Shick; Kim, Young-Wan

2015-02-15

A mutant derived from a cyclodextrin glucantransferase with an alanine residue as its acid/base catalyst residue (CGT-E284A) catalyzed regioselective glycosylation at 3-OH of l-ascorbic acid using α-maltosyl fluoride (αG2F) and l-ascorbic acid as the donor and acceptor, respectively, yielding 3-O-α-maltosyl-l-ascorbate (AA3αG2). The optimum conditions were determined by high-performance liquid chromatography analysis with 20mM αG2F and 40mM l-ascorbic acid as the substrates at pH 7.5 and 25°C with 1mg/ml of the enzyme for 24h. Calcium ions bound in CGT-E284A played an important role in the transglycosylation. CGT-E284A exhibited typical saturation kinetic behaviour for αG2F at a fixed acceptor concentration (40mM), and substrate inhibition by l-ascorbic acid was observed at high l-ascorbic acid concentrations (>60mM). AA3αG2 was isolated from a preparative scale reaction with a yield of 29%, and it showed extremely high stability under oxidative conditions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Tribology of steel/steel interaction in oil-in-water emulsion; a rationale for lubricity.

PubMed

Kumar, Deepak; Daniel, Jency; Biswas, S K

2010-05-15

Oil droplets are dispersed in water by an anionic surfactant to form an emulsion. The lubricity of this emulsion in steel/steel interaction is explored in a ball on flat nanotribometer. The droplet size and charge are measured using dynamic light scattering, while the substrate charge density is estimated using the pH titration method. These data are combined to calculate the DLVO forces for the droplets generated for a range of surfactant concentration and two oil to water volume ratios. The droplets have a clear bi-modal size distribution. The study shows that the smaller droplets which experience weak repulsion are situated (at the highest DLVO barrier) much closer to the substrate than the bigger droplets, which experience the same DLVO force, are. We suggest that the smaller droplets thus play a more important role in lubricity than what the bigger droplets do. The largest volume of such small droplets occurs in the 0.5 mM-1 mM range of surfactant concentration and 1% oil to water volume ratio, where the coefficient of friction is also observed to be the least. Copyright © 2010 Elsevier Inc. All rights reserved.

Highly enantioselective reduction of 4-(trimethylsilyl)-3-butyn-2-one to enantiopure (R)-4-(trimethylsilyl)-3-butyn-2-ol using a novel strain Acetobacter sp. CCTCC M209061.

PubMed

Xiao, Zi-Jun; Zong, Min-Hua; Lou, Wen-Yong

2009-12-01

The biocatalytic reduction of 4-(trimethylsilyl)-3-butyn-2-one to enantiopure (R)-4-(trimethylsilyl)-3-butyn-2-ol was successfully conducted with high enantioselectivity using immobilized whole cells of a novel strain Acetobacter sp. CCTCC M209061, newly isolated from kefir. Compared with other microorganisms that were investigated, Acetobacter sp. CCTCC M209061 was shown to be more effective for the bioreduction reaction, and afforded much higher yield and product enantiomeric excess (e.e.). The optimal buffer pH, co-substrate concentration, reaction temperature, substrate concentration and shaking rate were 5.0, 130.6 mM, 30 degrees C, 6.0 mM and 180 r/min, respectively. Under the optimized conditions, the maximum yield and the product e.e. were 71% and >99%, respectively, which are much higher than those reported previously. Additionally, the established biocatalytic system proved to be efficient for the bioreduction of acetyltrimethylsilane to (R)-1-trimethylsilylethanol with excellent yield and product e.e. The immobilized cells manifested a good operational stability under the above reaction conditions since they retained 70% of their catalytic activity after ten cycles of use.

Biogeochemical response of organic-rich freshwater marshes in the Louisiana delta plain to chronic river water influx

USGS Publications Warehouse

Swarzenski, C.M.; Doyle, T.W.; Fry, B.; Hargis, T.G.

2008-01-01

To help evaluate effects of Mississippi River inputs to sustainability of coastal Louisiana ecosystems, we compared porewater and substrate quality of organic-rich Panicum hemitomon freshwater marshes inundated by river water annually for more than 30 years (Penchant basin, PB) or not during the same time (Barataria basin, BB). In the marshes receiving river water the soil environment was more reduced, the organic substrate was more decomposed and accumulated more sulfur. The porewater dissolved ammonium and orthophosphate concentrations were an order of magnitude higher and sulfide and alkalinity concentrations were more than twice as high in PB compared with BB marshes. The pH was higher and dissolved iron concentrations were more than an order of magnitude lower in PB marshes than in BB marshes. The influx of nutrient-rich river water did not enhance end-of-year above-ground standing biomass or vertical accretion rates of the shallow substrate. The differences in porewater chemistry and substrate quality are reasonably linked to the long-term influx of river water through biogeochemical processes and transformations involving alkalinity, nitrate and sulfate. The key factor is the continual replenishment of alkalinity, nitrate and sulfate via overland flow during high river stage each year for several weeks to more than 6 months. This leads to a reducing soil environment, pooling of the phytotoxin sulfide and inorganic nutrients in porewater, and internally generated alkalinity. Organic matter decomposition is enhanced under these conditions and root mats degraded. The more decomposed root mat makes these marshes more susceptible to erosion during infrequent high-energy events (for example hurricanes) and regular low-energy events, such as tides and the passage of weather fronts. Our findings were unexpected and, if generally applicable, suggest that river diversions may not be the beneficial mitigating agent of wetland restoration and conservation that they are anticipated to be. ?? 2008 Springer Science+Business Media B.V.

Reactor performance of a 750 m(3) anaerobic digestion plant: varied substrate input conditions impacting methanogenic community.

PubMed

Wagner, Andreas Otto; Malin, Cornelia; Lins, Philipp; Gstraunthaler, Gudrun; Illmer, Paul

2014-10-01

A 750 m(3) anaerobic digester was studied over a half year period including a shift from good reactor performance to a reduced one. Various abiotic parameters like volatile fatty acids (VFA) (formic-, acetic-, propionic-, (iso-)butyric-, (iso-)valeric-, lactic acid), total C, total N, NH4 -N, and total proteins, as well as the organic matter content and dry mass were determined. In addition several process parameters such as temperature, pH, retention time and input of substrate and the concentrations of CH4, H2, CO2 and H2S within the reactor were monitored continuously. The present study aimed at the investigation of the abundance of acetogens and total cell numbers and the microbial methanogenic community as derived from PCR-dHPLC analysis in order to put it into context with the determined abiotic parameters. An influence of substrate quantity on the efficiency of the anaerobic digestion process was found as well as a shift from a hydrogenotrophic in times of good reactor performance towards an acetoclastic dominated methanogenic community in times of reduced reactor performance. After the change in substrate conditions it took the methano-archaeal community about 5-6 weeks to be affected but then changes occurred quickly. Copyright © 2014 Elsevier Ltd. All rights reserved.

Process parameter optimization for hydantoinase-mediated synthesis of optically pure carbamoyl amino acids of industrial value using Pseudomonas aeruginosa resting cells.

PubMed

Engineer, Anupama S; Dhakephalkar, Anita P; Gaikaiwari, Raghavendra P; Dhakephalkar, Prashant K

2013-12-01

Hydantoinase-mediated enzymatic synthesis of optically pure carbamoyl amino acids was investigated as an environmentally friendly, energy-efficient alternative to the otherwise energy-intensive, polluting chemical synthesis. Hydantoinase-producing bacterial strain was identified as Pseudomonas aeruginosa by 16S rRNA gene sequencing and biochemical profiling using the BIOLOG Microbial Identification System. Hydantoinase activity was assessed using hydantoin analogs and 5-monosubstituted hydantoins as substrates in a colorimetric assay. The hydantoinase gene was PCR amplified using gene-specific primers and sequenced on an automated gene analyzer. Hydantoinase gene sequence of P. aeruginosa MCM B-887 revealed maximum homology of only 87 % with proven hydantoinase gene sequences in GenBank. MCM B-887 resting cells converted >99 % of substrate into N-carbamoyl amino acids under optimized condition at 42 °C, pH 8.0, and 100 mM substrate concentration in <120 min. Hydantoin hydrolyzing activity was D-selective and included broad substrate profile of 5-methyl hydantoin, 5-phenyl hydantoin, 5-hydroxyphenyl hydantoin, o-chlorophenyl hydantoin, as well as hydantoin analogs such as allantoin, dihydrouracil, etc. MCM B-887 resting cells may thus be suitable for bio-transformations leading to the synthesis of optically pure, unnatural carbamoyl amino acids of industrial importance.

Influence of surface charge, binding site residues and glycosylation on Thielavia terrestris cutinase biochemical characteristics

PubMed Central

Shirke, Abhijit N.; Basore, Danielle; Holton, Samantha; Su, An; Baugh, Evan; Butterfoss, Glenn L.; Makhatadze, George

2016-01-01

Cutinases are esterases of industrial importance for applications in recycling and surface modification of polyesters. The cutinase from Thielavia terrestris (TtC) is distinct in terms of its ability to retain its stability and activity in acidic pH. Stability and activity in acidic pHs are desirable for esterases as the pH of the reaction tends to go down with the generation of acid. The pH stability and activity are governed by the charged state of the residues involved in catalysis or in substrate binding. In this study, we performed the detailed structural and biochemical characterization of TtC coupled with surface charge analysis to understand its acidic tolerance. The stability of TtC in acidic pH was rationalized by evaluating the contribution of charge interactions to the Gibbs free energy of unfolding at varying pHs. The activity of TtC was found to be limited by substrate binding affinity, which is a function of the surface charge. Additionally, the presence of glycosylation affects the biochemical characteristics of TtC owing to steric interactions with residues involved in substrate binding. PMID:26758295

Insights into the mechanism and catalysis of oxime coupling chemistry at physiological pH.

PubMed

Wang, Shujiang; Gurav, Deepanjali; Oommen, Oommen P; Varghese, Oommen P

2015-04-07

The dynamic covalent-coupling reaction involving α-effect nucleophiles has revolutionized bioconjugation approaches, due to its ease and high efficiency. Key to its success is the discovery of aniline as a nucleophilic catalyst, which made this reaction feasible under physiological conditions. Aniline however, is not so effective for keto substrates. Here, we investigate the mechanism of aniline activation in the oxime reaction with aldehyde and keto substrates. We also present carboxylates as activating agents that can promote the oxime reaction with both aldehyde and keto substrates at physiological pH. This rate enhancement circumvents the influence of α-effect by forming H-bonds with the rate-limiting intermediate, which drives the reaction to completion. The combination of aniline and carboxylates had a synergistic effect, resulting in a ∼14-31-fold increase in reaction rate at pD 7.4 with keto substrates. The biocompatibility and efficiency of carboxylate as an activating agent is demonstrated by performing cell-surface oxime labeling at physiological pH using acetate, which showed promising results that were comparable with aniline. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electroosmotic pump performance is affected by concentration polarizations of both electrodes and pump

PubMed Central

Suss, Matthew E.; Mani, Ali; Zangle, Thomas A.; Santiago, Juan G.

2010-01-01

Current methods of optimizing electroosmotic (EO) pump performance include reducing pore diameter and reducing ionic strength of the pumped electrolyte. However, these approaches each increase the fraction of total ionic current carried by diffuse electric double layer (EDL) counterions. When this fraction becomes significant, concentration polarization (CP) effects become important, and traditional EO pump models are no longer valid. We here report on the first simultaneous concentration field measurements, pH visualizations, flow rate, and voltage measurements on such systems. Together, these measurements elucidate key parameters affecting EO pump performance in the CP dominated regime. Concentration field visualizations show propagating CP enrichment and depletion fronts sourced by our pump substrate and traveling at order mm/min velocities through millimeter-scale channels connected serially to our pump. The observed propagation in millimeter-scale channels is not explained by current propagating CP models. Additionally, visualizations show that CP fronts are sourced by and propagate from the electrodes of our system, and then interact with the EO pump-generated CP zones. With pH visualizations, we directly detect that electrolyte properties vary sharply across the anode enrichment front interface. Our observations lead us to hypothesize possible mechanisms for the propagation of both pump- and electrode-sourced CP zones. Lastly, our experiments show the dynamics associated with the interaction of electrode and membrane CP fronts, and we describe the effect of these phenomena on EO pump flow rates and applied voltages under galvanostatic conditions. PMID:21516230

Removal of acetaminophen in water by laccase immobilized in barium alginate.

PubMed

Ratanapongleka, Karnika; Punbut, Supot

2018-02-01

This research has focused on the optimization of immobilized laccase condition and utilization in degradation of acetaminophen contaminated in aqueous solution. Laccase from Lentinus polychrous was immobilized in barium alginate. The effects of laccase immobilization such as sodium alginate concentration, barium chloride concentration and gelation time were studied. The optimal conditions for immobilization were sodium alginate 5% (w/v), barium chloride 5% (w/v) and gelation time of 60 min. Immobilized laccase was then used for acetaminophen removal. Acetaminophen was removed quickly in the first 50 min. The degradation rate and percentage of removal increased when the enzyme concentration increased. Immobilized laccase at 0.57 U/g-alginate showed the maximum removal at 94% in 240 min. The removal efficiency decreased with increasing initial acetaminophen concentration. The K m value for immobilized laccase (98.86 µM) was lower than that of free laccase (203.56 µM), indicating that substrate affinity was probably enhanced by immobilization. The immobilized enzyme exhibited high activity and good acetaminophen removal at pH 7 and temperature of 35°C. The activation energies of free and immobilized laccase for degradation of acetaminophen were 8.08 and 17.70 kJ/mol, respectively. It was also found that laccase stability to pH and temperature increased after immobilization. Furthermore, immobilized laccase could be reused for five cycles. The capability of removal and enzyme activity were retained above 70%.

Influence of pine bark particle size and pH on cation exchange capacity

USDA-ARS?s Scientific Manuscript database

Cation exchange capacity (CEC) describes the maximum quantity of cations a soil or substrate can hold while being exchangeable with the soil solution. While CEC has been studied for peat-based substrates, relatively little work has documented factors that affect CEC of pine bark substrates. The ob...

Control of Growth Rate by Initial Substrate Concentration at Values Below Maximum Rate

PubMed Central

Gaudy, Anthony F.; Obayashi, Alan; Gaudy, Elizabeth T.

1971-01-01

The hyperbolic relationship between specific growth rate, μ, and substrate concentration, proposed by Monod and used since as the basis for the theory of steady-state growth in continuous-flow systems, was tested experimentally in batch cultures. Use of a Flavobacterium sp. exhibiting a high saturation constant for growth in glucose minimal medium allowed direct measurement of growth rate and substrate concentration throughout the growth cycle in medium containing a rate-limiting initial concentration of glucose. Specific growth rates were also measured for a wide range of initial glucose concentrations. A plot of specific growth rate versus initial substrate concentration was found to fit the hyperbolic equation. However, the instantaneous relationship between specific growth rate and substrate concentration during growth, which is stated by the equation, was not observed. Well defined exponential growth phases were developed at initial substrate concentrations below that required for support of the maximum exponential growth rate and a constant doubling time was maintained until 50% of the substrate had been used. It is suggested that the external substrate concentration initially present “sets” the specific growth rate by establishing a steady-state internal concentration of substrate, possibly through control of the number of permeation sites. PMID:5137579

Kinetics and regulation of the myofibrillar adenosine triphosphatase.

PubMed Central

Goodno, C C; Wall, C M; Perry, S V

1978-01-01

1. The steady-state kinetic behaviour of the ATPase (adenosine triphosphatase) of intact myofibrils was studied in the presence of both high and low concentrations of Ca2+ (0.25 mM and less than 10 nM respectively). 2. Kinetic data were collected over the initial linear phase of the assay, which lasts for 20--60s. To obtain consistent data we found it necessary to use either fresh myofibril preparations or preparations that had been stored in the presence of thiol compounds. 3. When assayed in the presence of 0.25 mM-Ca2+, the myofibrillar ATPase obeyed Michaelis-Menten kinetics over the range 0.03--5.0 mM-MgATP (Km 16 +/- 6 micrometer, V 0.4 +/- 0.1 mumol/min per mg). 4. At low Ca2+ concentrations (less than 10 nM) the myofibrillar ATPase displayed pronounced substrate inhibition, which was not observed at high Ca2+ concentrations. Thus increasing the MgATP concentration had the net effect of decreasing the ATPase activity at low Ca2+ relative to that at high Ca2+. This preferential effect of MgATP on the low-Ca2+ ATPase may be important in Ca2+ control. 5. The substrate inhibition that was observed at low Ca2+ was lost on storage or thiol modification of the myofibrils. 6. Under physiological conditions (2 mM-MgATP, I 0.15, pH 7.0), the ATPase of fresh and thiol-protected myofibrils displayed approx. 100-fold activation by Ca2+. PMID:154323

Activity of Escherichia coli, Aspergillus niger, and Rye Phytase toward Partially Phosphorylated myo-Inositol Phosphates.

PubMed

Greiner, Ralf

2017-11-08

Kinetic parameters for the dephosphorylation of sodium phytate and a series of partially phosphorylated myo-inositol phosphates were determined at pH 3.0 and pH 5.0 for three phytase preparations (Aspergillus niger, Escherichia coli, rye). The enzymes showed lower affinity and turnover numbers at pH 3 compared to pH 5 toward all myo-inositol phosphates included in the study. The number and distribution of phosphate groups on the myo-inositol ring affected the kinetic parameters. Representatives of the individual phytate dephosphorylation pathways were identified as the best substrates of the phytases. Within the individual phytate dephosphorylation pathways, the pentakisphosphates were better substrates compared to the tetrakisphosphates or phytate itself. E. coli and rye phytase showed comparable activities at both pH values toward the tetrakis- and trisphosphate, whereas A. niger phytase exhibited a higher activity toward the tetrakisphosphate. A myo-inositol phosphate with alternate phosphate groups was shown to be not significantly dephosphorylated by the phytases.

Surface laser alloying of 17-4PH stainless steel steam turbine blades

NASA Astrophysics Data System (ADS)

Yao, Jianhua; Wang, Liang; Zhang, Qunli; Kong, Fanzhi; Lou, Chenghua; Chen, Zhijun

2008-09-01

As a known high-quality precipitation hardening stainless steel with high strength, high antifatigue, excellent corrosion resistance and good weldability, 17-4PH has been widely used to produce steam turbine blades. However, under the impact of high-speed steam and water droplets, the blades are prone to cavitation, which could lead to lower efficiency, shorter life time, and even accidents. In this article, the 17-4PH blade's surface was alloyed using a high power CO 2 laser. The microstructure and microhardness of hardened 17-4PH were tested by scanning electronic microscope (SEM), X-ray diffraction (XRD), energy disperse spectroscopy (EDS) and a microhardness tester. After laser alloying, the surface layer was denser and the grain refined, while the microhardness of the surface (average 610HV 0.2) was about one times higher than that of the substrate material (330HV 0.2). The friction coefficient of the laser-alloyed 17-4PH layer was much lower than that of the substrate.

Tripolyphosphate hydrolysis by bovine fast and slow myosin subfragment 1 isoforms

PubMed Central

Yamazaki, Marie; Shen, Qingwu W.; Swartz, Darl R.

2010-01-01

Polyphosphates are used in the meat industry to increase the water holding capacity of meat products. Tripolyphosphate (TPP) is a commonly used polyphosphate and it is metabolized into pyrophosphate and monophosphate in meat. The enzymes responsible for its metabolism have not been fully characterized. The motor domain of myosin (subfragment 1 or S1) is a likely candidate. The objectives of this study were to determine if bovine S1 hydrolyzes TPP, to characterize the TPPase activity of the fast (cutaneous trunci) and slow (masseter) isoforms, and to determine the influence of pH on S1 TPPase activity. S1 hydrolyzed TPP and in comparison with ATP as substrate, it hydrolyzed TPP 16 – 32% more slowly. Fast S1 hydrolyzed both substrates faster compared to slow S1 and the difference between the isoforms was greater with TPP as the substrate. The Vmax was 0.94 and 5.0 nmole Pi/mg S1 protein/min while the Km was 0.38 and 0.90 mM TPP for slow and fast S1, respectively. Pyrophosphate was a strong inhibitor of TPPase activity with a Ki of 88 and 8.3 μM PPi for fast and slow S1 isoforms, respectively. Both ATPase and TPPase activities were influenced by pH with the activity being higher at low pH for both fast and slow S1 isoforms. The activity at pH 5.4 was 1.5 to 4 fold higher than that at pH 7.6 for the different isoforms and substrates. These data show that myosin S1 readily hydrolyzes TPP and suggest that it is a major TPPase in meat. PMID:20416813

Effects of solution pH and electrical parameters on hydroxyapatite coatings deposited by a plasma-assisted electrophoresis technique.

PubMed

Nie, X; Leyland, A; Matthews, A; Jiang, J C; Meletis, E I

2001-12-15

Hydroxyapatite (HA) coatings can be deposited using a hybrid process of plasma electrolysis and electrophoresis, called plasma-assisted electrophoretic deposition (PEPD). HA aqueous suspensions with various pH values were prepared using a modified ultrasonic cleaning bath as an agitator/stirrer. Both DC and unbalanced AC power supplies were used to bias the titanium alloy substrate materials employed in this work. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and Fourier transform infrared spectroscopy (FTIR) were used to observe and analyze coating morphology and microstructure. It was shown that the morphology and composition of the calcium phosphate coatings were significantly influenced by solution pH values; the level of "pure" HA in the coatings' composition corresponded to both solution pH and the type of power supply employed. Loss of hydroxyl radials (i.e., dehydroxylation), which degrades the performance of the hydroxyapatite coating in terms of long-term chemical and mechanical stability, can be virtually eliminated by a combination of high pH and unbalanced AC plasma power. In addition, the underlying TiO2 coatings used to support the HA layer (preproduced by plasma electrolysis process) have a nanoscaled (10-20 nm) polycrystalline structure. TEM studies also revealed a dense, continuous amorphous titania layer (10 nm in thickness) at the interface between the Ti alloy substrate and the TiO2 layer, which may play a role in improving the corrosion resistance of the substrate. Such a nanophase TiO2 layer (if used as a coating alone) may also provide a further improvement in osteoinductive properties, compared to a conventional TiO2 coating on the Ti alloy substrate. Copyright 2001 John Wiley & Sons, Inc. J Biomed Mater Res 57: 612-618, 2001

Electrodeposition of titania and barium titanate thin films for high dielectric applications

NASA Astrophysics Data System (ADS)

Roy, Biplab Kumar

In order to address the requirement of a low-temperature low-cost cost processing for depositing high dielectric constant ceramic films for applications in embedded capacitor and flexible electronics technology, two different chemical bath processes, namely, thermohydrolytic deposition (TD) and cathodic electrodeposition (ED) have been exploited to generate titania thin films. In thermohydrolytic deposition technique, titania films were generated from acidic aqueous solution of titanium chloride on F: SnO2 coated glass and Si substrates by temperature assisted hydrolysis mechanism. On the other hand, in cathodic electrodeposition, in-situ electro-generation of hydroxyl ions triggered a fast deposition of titania on conductive substrates such as copper and F: SnO2 coated glass from peroxotitanium solution at low temperatures (˜0°C). In both techniques, solution compositions affected the morphology and crystallinity of the films. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques have been employed to perform such characterization. As both processes utilized water as solvent, the as-deposited films contained hydroxyl ligand or physically adsorbed water molecules in the titania layer. Besides that, electrodeposited films contained peroxotitanium bonds which were characterized by FTIR studies. Although as-electrodeposited titania films were X-ray amorphous, considerable crystallinity could be generated by heat treatment. The films obtained from both the processes showed v moderately high dielectric constant (ranging from 9-30 at 100 kHz) and high breakdown voltage (0.09-0.15 MV/cm) in electrical measurements. To further improve the dielectric constant, electrodeposited titania films were converted to barium titanate films in high pH barium ion containing solution at 80-90°C. The resultant film contained cubic crystalline barium titanate verified by XRD analysis. Simple low-temperature hydrothermal technique of conversion worked perfect for F:SnO2 coated glass substrates, but in this process, high pH precursor caused corrosion in copper substrates and deposition of copper oxide in the final films. To overcome this, an innovative technique, which incorporates an electrochemical protection of substrates by application of cathodic potential in addition to common hydrothermal conversion, has been adopted. Films generated by common hydrothermal technique on F:SnO 2/glass substrates and via electrochemical-hydrothermal technique on Cu substrates showed promising dielectric behavior. Apart from the experimental studies, this report also includes various thermodynamic studies related to hydrolysis and precipitation of titanium ion, protection of copper during titania deposition and barium titanate conversion. Gibbs free energy based model and speciation studies were used to understand supersaturation which is a controlling factor in thermohydrolytic deposition. Similar approaches were utilized to understand the possibilities of barium titanate formation at different Ba2+ concentrations with different pH conditions. Possibilities of atmospheric carbon dioxide incorporation to generate barium carbonate instead of barium titanate formation were also determined by mathematical calculations. Whenever relevant, results of such theoretical analysis were utilized to design the experiment or to explain the experimental observations.

pH pre-corrected liquid hot water pretreatment on corn stover with high hemicellulose recovery and low inhibitors formation.

PubMed

Li, Hong-Qiang; Jiang, Wei; Jia, Jing-Xia; Xu, Jian

2014-02-01

A challenge for lignocellulosic pretreatment is how to retain hemicellulose as much as possible. To reduce the degradation of hemicellulose and increase the recovery of sugars, an effective pH pre-corrected liquid hot water pretreatment (LHWP) was developed by employing a small amount of NaOH (⩽5/100g substrate) to accelerate the hemicellulose deacetylation and simultaneously pre-correct the acid hydrolyzate in situ. The results showed that the pH pre-correction can control the hydrolyzate pH. Under the pretreatment severity (PS) of 4.0, the pH pre-corrected LHWP reduced the hemicellulose degradation by 35.3-92.3%, decreased furfural formation by 90.5-99.8%. The highest hemicellulose recovery of 96.38% was obtained with pH pre-corrected by 2g NaOH/100g substrate. Enzymatic hydrolysis (EH) and simultaneous saccharification and fermentation (SSF) on the whole slurry from the pH pre-corrected LHWP showed that the hemicellulose retained in the solid residue did not bring significant resistance to cellulose EH (p=0.837). Copyright © 2013 Elsevier Ltd. All rights reserved.

Copper-Hydroperoxo Mediated N-Debenzylation Chemistry Mimicking Aspects of Copper Monoxygenases

PubMed Central

Maiti, Debabrata; Narducci Sarjeant, Amy A.; Karlin, Kenneth D.

2008-01-01

Substantial oxidative N-debenzylation reaction along with PhCH=O formation occurs from a hydroperoxo copper(II) complex which has a dibenzylamino substrate (-N(CH2Ph)2 appended as a substituent on one pyridyl group of its tripodal tetradentate TMPA {≡ TPA ≡ tris(2-pyridylmethyl)amine)} ligand framework. During the course of the (LN(CH2Ph)2)CuII(−OOH) reactivity, formation of a substrate and −OOH (an oxygen atom) derived alkoxo CuII(−OR) complex occurs. The observation that the same CuII(−OR) species occurs from CuI/PhIO chemistry suggests the possibility that a copper-oxo (cupryl) reactive intermediate forms during alkoxo species formation, and new ESI-MS data obtained provides some further support for this high-valent intermediate. Net H-atom abstraction chemistry is proposed, based on kinetic isotope effect studies provided here and that previously published for a closely related CuII(−OOH) species incorporating dimethylamine (-N(CH3)2) as the internal substrate (J. Am. Chem. Soc. 2007, 129, 6720-6721); the CuI/PhIO reactivity, with similar isotope effect results, provides further support. The reactivity of these chemical systems closely resembles proposed oxidative N-dealkylation mechanisms effected by the copper-monooxygenases dopamine β-monooxygenase (DβM) or peptidylglycine-α-hydroxylating monooxygenase (PHM). PMID:18783212

Vermiculite's strong buffer capacity renders it unsuitable for studies of acidity on soybean (Glycine max L.) nodulation and growth.

PubMed

Indrasumunar, Arief; Gresshoff, Peter M

2013-11-14

Vermiculite is the most common soil-free growing substrate used for plants in horticultural and scientific studies due to its high water holding capacity. However, some studies are not suitable to be conducted in it. The described experiments aimed to test the suitability of vermiculite to study the effect of acidity on nodulation and growth of soybean (Glycine max L.). Two different nutrient solutions (Broughton & Dilworth, and modified Herridge nutrient solutions) with or without MES buffer addition were used to irrigate soybean grown on vermiculite growth substrates. The pH of nutrient solutions was adjusted to either pH 4.0 or 7.0 prior its use. The nodulation and vegetative growth of soybean plants were assessed at 3 and 4 weeks after inoculation. The unsuitability of presumably inert vermiculite as a physical plant growth substrate for studying the effects of acidity on soybean nodulation and plant growth was illustrated. Nodulation and growth of soybean grown in vermiculite were not affected by irrigation with pH-adjusted nutrient solution either at pH 4.0 or 7.0. This was reasonably caused by the ability of vermiculite to neutralise (buffer) the pH of the supplied nutrient solution (pH 2.0-7.0). Due to its buffering capacity, vermiculite cannot be used as growth support to study the effect of acidity on nodulation and plant growth.

Electrostatic Assemblies of Well-Dispersed AgNPs on the Surface of Electrospun Nanofibers as Highly Active SERS Substrates for Wide-Range pH Sensing.

PubMed

Yang, Tong; Ma, Jun; Zhen, Shu Jun; Huang, Cheng Zhi

2016-06-15

Surface-enhanced Raman scattering (SERS) has shown high promise in analysis and bioanalysis, wherein noble metal nanoparticles (NMNPs) such as silver nanoparticles were employed as substrates because of their strong localized surface plasmon resonance (LSPR) properties. However, SERS-based pH sensing was restricted because of the aggregation of NMNPs in acidic medium or biosamples with high ionic strength. Herein, by using the electrostatic interaction as a driving force, AgNPs are assembled on the surface of ethylene imine polymer (PEI)/poly(vinyl alcohol) (PVA) electrospun nanofibers, which are then applied as highly sensitive and reproducible SERS substrate with an enhancement factor (EF) of 10(7)-10(8). When p-aminothiophenol (p-ATP) is used as an indicator with its b2 mode, a good and wide linear response to pH ranging from 2.56 to 11.20 could be available, and the as-prepared nanocomposite fibers then could be fabricated as excellent pH sensors in complicated biological samples such as urine, considering that the pH of urine could reflect the acid-base status of a person. This work not only emerges a cost-effective, direct, and convenient approach to homogeneously decorate AgNPs on the surface of polymer nanofibers but also supplies a route for preparing other noble metal nanofibrous sensing membranes.

A pH-responsive interface derived from resilin-mimetic protein Rec1-resilin.

PubMed

Truong, My Y; Dutta, Naba K; Choudhury, Namita R; Kim, Misook; Elvin, Christopher M; Hill, Anita J; Thierry, Benjamin; Vasilev, Krasimir

2010-05-01

In this investigation, for the first time we report the effects of pH on the molecular orientation, packing density, structural properties, adsorption characteristics and viscoelastic behaviour of resilin-mimetic protein rec1-resilin at the solid-liquid interface using quartz crystal microbalance with dissipation monitoring (QCM-D) and surface plasmon resonance (SPR) spectroscopy. QCM-D and SPR data confirm that the binding ability of rec1-resilin on a substrate is strongly pH-dependent the protein packing density on a gold surface is calculated to be 4.45 x 10(13) per cm(2) at the isoelectric point (IEP approximately 4.9), 8.79 x 10(11) per cm(2) at pH 2 and 9.90 x 10(11) per cm(2) at pH 12, respectively. Our findings based on the thickness, dissipation and viscoelasticity of the rec1-resilin adlayer also indicate that it is adsorbed onto the gold substrate with different orientation depending on pH, such as back-on adsorption at acidic pH of 2, compact end-on bilayer adsorption at the IEP and side-on at high alkaline pH of 12. When rec1-resilin is 'pinned' to the substrate at IEP and subsequently exposed to an electrolyte solution adjusted to different pH, it switches from a compact globular conformation of the bio-macromolecule at the IEP to a coil conformation at pH between IEP to IED (IED = pKa value of tyrosine amino acid residue) and an extended coil conformation at pH > IED. This transformation from globule to coil to extended coil conformation is kinetically fast, robust and completely reversible. Such responsive surfaces created using 'smart' biomimetic rec1-resilin have the potential to find applications in many areas including biotechnology, medicine, sensors, controlled drug delivery systems and engineering. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Cysteine Transport through Excitatory Amino Acid Transporter 3 (EAAT3)

PubMed Central

Watts, Spencer D.; Torres-Salazar, Delany; Divito, Christopher B.; Amara, Susan G.

2014-01-01

Excitatory amino acid transporters (EAATs) limit glutamatergic signaling and maintain extracellular glutamate concentrations below neurotoxic levels. Of the five known EAAT isoforms (EAATs 1–5), only the neuronal isoform, EAAT3 (EAAC1), can efficiently transport the uncharged amino acid L-cysteine. EAAT3-mediated cysteine transport has been proposed to be a primary mechanism used by neurons to obtain cysteine for the synthesis of glutathione, a key molecule in preventing oxidative stress and neuronal toxicity. The molecular mechanisms underlying the selective transport of cysteine by EAAT3 have not been elucidated. Here we propose that the transport of cysteine through EAAT3 requires formation of the thiolate form of cysteine in the binding site. Using Xenopus oocytes and HEK293 cells expressing EAAT2 and EAAT3, we assessed the transport kinetics of different substrates and measured transporter-associated currents electrophysiologically. Our results show that L-selenocysteine, a cysteine analog that forms a negatively-charged selenolate ion at physiological pH, is efficiently transported by EAATs 1–3 and has a much higher apparent affinity for transport when compared to cysteine. Using a membrane tethered GFP variant to monitor intracellular pH changes associated with transport activity, we observed that transport of either L-glutamate or L-selenocysteine by EAAT3 decreased intracellular pH, whereas transport of cysteine resulted in cytoplasmic alkalinization. No change in pH was observed when cysteine was applied to cells expressing EAAT2, which displays negligible transport of cysteine. Under conditions that favor release of intracellular substrates through EAAT3 we observed release of labeled intracellular glutamate but did not detect cysteine release. Our results support a model whereby cysteine transport through EAAT3 is facilitated through cysteine de-protonation and that once inside, the thiolate is rapidly re-protonated. Moreover, these findings suggest that cysteine transport is predominantly unidirectional and that reverse transport does not contribute to depletion of intracellular cysteine pools. PMID:25275463

Dry co-digestion of sewage sludge and rice straw under mesophilic and thermophilic anaerobic conditions.

PubMed

Chu, Xiangqian; Wu, Guangxue; Wang, Jiaquan; Hu, Zhen-Hu

2015-12-01

Dry anaerobic digestion of sewage sludge can recover biogas as energy; however, its low C/N ratio limits it as a single substrate in the anaerobic digestion. Rice straw is an abundant agricultural residue in China, which is rich in carbon and can be used as carbon source. In the present study, the performance of dry co-digestion of sewage sludge and rice straw was investigated under mesophilic (35 °C) and thermophilic (55 °C) conditions. The operational factors impacting dry co-digestion of sewage sludge and rice straw such as C/N ratio, moisture content, and initial pH were explored under mesophilic conditions. The results show that low C/N ratios resulted in a higher biogas production rate, but a lower specific biogas yield; low moisture content of 65 % resulted in the instability of the digestion system and a low specific biogas yield. Initial pH ranging 7.0-9.0 did not affect the performance of the anaerobic digestion. The C/N ratio of 26-29:1, moisture content of 70-80 %, and pH 7.0-9.0 resulted in good performance in the dry mesophilic co-digestion of sewage sludge and rice straw. As compared with mesophilic digestion, thermophilic co-digestion of sewage sludge and rice straw significantly enhanced the degradation efficiency of the substrates and the specific biogas yield (p < 0.05) at the conditions of C/N ratio 26:1, moisture content 80 %, and natural initial pH. Although high concentrations of ammonia-nitrogen (NH4-N, 1500 mg/kg wet weight) were formed during thermophilic digestion, there was no obvious inhibition occurred. The results indicated that rice straw can be used as carbon source for the dry co-digestion of sewage sludge under mesophilic and thermophilic conditions.

Combined "de novo" and "ex novo" lipid fermentation in a mix-medium of corncob acid hydrolysate and soybean oil by Trichosporon dermatis.

PubMed

Huang, Chao; Luo, Mu-Tan; Chen, Xue-Fang; Qi, Gao-Xiang; Xiong, Lian; Lin, Xiao-Qing; Wang, Can; Li, Hai-Long; Chen, Xin-De

2017-01-01

Microbial oil is one important bio-product for its important function in energy, chemical, and food industry. Finding suitable substrates is one key issue for its industrial application. Both hydrophilic and hydrophobic substrates can be utilized by oleaginous microorganisms with two different bio-pathways (" de novo " lipid fermentation and " ex novo " lipid fermentation). To date, most of the research on lipid fermentation has focused mainly on only one fermentation pathway and little work was carried out on both " de novo " and " ex novo " lipid fermentation simultaneously; thus, the advantages of both lipid fermentation cannot be fulfilled comprehensively. In this study, corncob acid hydrolysate with soybean oil was used as a mix-medium for combined " de novo " and " ex novo " lipid fermentation by oleaginous yeast Trichosporon dermatis . Both hydrophilic and hydrophobic substrates (sugars and soybean oil) in the medium can be utilized simultaneously and efficiently by T. dermatis . Different fermentation modes were compared and the batch mode was the most suitable for the combined fermentation. The influence of soybean oil concentration, inoculum size, and initial pH on the lipid fermentation was evaluated and 20 g/L soybean oil, 5% inoculum size, and initial pH 6.0 were suitable for this bioprocess. By this technology, the lipid composition of extracellular hydrophobic substrate (soybean oil) can be modified. Although adding emulsifier showed little beneficial effect on lipid production, it can modify the intracellular lipid composition of T. dermatis . The present study proves the potential and possibility of combined " de novo " and " ex novo " lipid fermentation. This technology can use hydrophilic and hydrophobic sustainable bio-resources to generate lipid feedstock for the production of biodiesel or other lipid-based chemical compounds and to treat some special wastes such as oil-containing wastewater.

Simultaneous production of 2,3-butanediol, ethanol and hydrogen with a Klebsiella sp. strain isolated from sewage sludge.

PubMed

Wu, Ken-Jer; Saratale, Ganesh D; Lo, Yung-Chung; Chen, Wen-Ming; Tseng, Ze-Jing; Chang, Ming-Ching; Tsai, Ben-Ching; Su, Ay; Chang, Jo-Shu

2008-11-01

A Klebsiella sp. HE1 strain isolated from hydrogen-producing sewage sludge was examined for its ability to produce H2 and other valuable soluble metabolites (e.g., ethanol and 2,3-butanediol) from sucrose-based medium. The effect of pH and carbon substrate concentration on the production of soluble and gaseous products was investigated. The major soluble metabolite produced from Klebsiella sp. HE1 was 2,3-butanediol, accounting for over 42-58% of soluble microbial products (SMP) and its production efficiency enhanced after increasing the initial culture pH to 7.3 (without pH control). The HE1 strain also produced ethanol (contributing to 29-42% of total SMP) and a small amount of lactic acid and acetic acid. The gaseous products consisted of H2 (25-36%) and CO2 (64-75%). The optimal cumulative hydrogen production (2.7 l) and hydrogen yield (0.92mol H2 mol sucrose(-1)) were obtained at an initial sucrose concentration of 30g CODl(-1) (i.e., 26.7gl(-1)), which also led to the highest production rate for H2 (3.26mmol h(-1)l(-1)), ethanol (6.75mmol h(-1)l(-1)) and 2,3-butanediol (7.14mmol h(-1)l(-1)). The highest yield for H2, ethanol and 2,3-butanediol was 0.92, 0.81 and 0.59molmol-sucrose(-1), respectively. As for the overall energy production performance, the highest energy generation rate was 27.7kJ h(-1)l(-1) and the best energy yield was 2.45kJmolsucrose(-1), which was obtained at a sucrose concentration of 30 and 20g CODl(-1), respectively.

Bioethanol production by a xylan fermenting thermophilic isolate Clostridium strain DBT-IOC-DC21.

PubMed

Singh, Nisha; Puri, Munish; Tuli, Deepak K; Gupta, Ravi P; Barrow, Colin J; Mathur, Anshu S

2018-06-01

To overcome the challenges associated with combined bioprocessing of lignocellulosic biomass to biofuel, finding good organisms is essential. An ethanol producing bacteria DBT-IOC-DC21 was isolated from a compost site via preliminary enrichment culture on a pure hemicellulosic substrate and identified as a Clostridium strain by 16S rRNA analysis. This strain presented broad substrate spectrum with ethanol, acetate, lactate, and hydrogen as the primary metabolic end products. The optimum conditions for ethanol production were found to be an initial pH of 7.0, a temperature of 70 °C and an L-G ratio of 0.67. Strain presented preferential hemicellulose fermentation when compared to various substrates and maximum ethanol concentration of 26.61 mM and 43.63 mM was produced from xylan and xylose, respectively. During the fermentation of varying concentration of xylan, a substantial amount of ethanol ranging from 25.27 mM to 67.29 mM was produced. An increased ethanol concentration of 40.22 mM was produced from a mixture of cellulose and xylan, with a significant effect observed on metabolic flux distribution. The optimum conditions were used to produce ethanol from 28 g L -1 rice straw biomass (RSB) (equivalent to 5.7 g L -1 of the xylose equivalents) in which 19.48 mM ethanol production was achieved. Thus, Clostridium strain DBT-IOC-DC21 has the potential to perform direct microbial conversion of untreated RSB to ethanol at a yield comparative to xylan fermentation. Copyright © 2018 Elsevier Ltd. All rights reserved.

Bioelectricity Generation and Bioremediation of an Azo-Dye in a Microbial Fuel Cell Coupled Activated Sludge Process

PubMed Central

Khan, Mohammad Danish; Abdulateif, Huda; Ismail, Iqbal M.; Sabir, Suhail; Khan, Mohammad Zain

2015-01-01

Simultaneous bioelectricity generation and dye degradation was achieved in the present study by using a combined anaerobic-aerobic process. The anaerobic system was a typical single chambered microbial fuel cell (SMFC) which utilizes acid navy blue r (ANB) dye along with glucose as growth substrate to generate electricity. Four different concentrations of ANB (50, 100, 200 and 400 ppm) were tested in the SMFC and the degradation products were further treated in an activated sludge post treatment process. The dye decolorization followed pseudo first order kinetics while the negative values of the thermodynamic parameter ∆G (change in Gibbs free energy) shows that the reaction proceeds with a net decrease in the free energy of the system. The coulombic efficiency (CE) and power density (PD) attained peak values at 10.36% and 2,236 mW/m2 respectively for 200 ppm of ANB. A further increase in ANB concentrations results in lowering of cell potential (and PD) values owing to microbial inhibition at higher concentrations of toxic substrates. Cyclic voltammetry studies revealed a perfect redox reaction was taking place in the SMFC. The pH, temperature and conductivity remain 7.5–8.0, 27(±2°C and 10.6–18.2 mS/cm throughout the operation. The biodegradation pathway was studied by the gas chromatography coupled with mass spectroscopy technique, suggested the preferential cleavage of the azo bond as the initial step resulting in to aromatic amines. Thus, a combined anaerobic-aerobic process using SMFC coupled with activated sludge process can be a viable option for effective degradation of complex dye substrates along with energy (bioelectricity) recovery. PMID:26496083

Bioelectricity Generation and Bioremediation of an Azo-Dye in a Microbial Fuel Cell Coupled Activated Sludge Process.

PubMed

Khan, Mohammad Danish; Abdulateif, Huda; Ismail, Iqbal M; Sabir, Suhail; Khan, Mohammad Zain

2015-01-01

Simultaneous bioelectricity generation and dye degradation was achieved in the present study by using a combined anaerobic-aerobic process. The anaerobic system was a typical single chambered microbial fuel cell (SMFC) which utilizes acid navy blue r (ANB) dye along with glucose as growth substrate to generate electricity. Four different concentrations of ANB (50, 100, 200 and 400 ppm) were tested in the SMFC and the degradation products were further treated in an activated sludge post treatment process. The dye decolorization followed pseudo first order kinetics while the negative values of the thermodynamic parameter ∆G (change in Gibbs free energy) shows that the reaction proceeds with a net decrease in the free energy of the system. The coulombic efficiency (CE) and power density (PD) attained peak values at 10.36% and 2,236 mW/m2 respectively for 200 ppm of ANB. A further increase in ANB concentrations results in lowering of cell potential (and PD) values owing to microbial inhibition at higher concentrations of toxic substrates. Cyclic voltammetry studies revealed a perfect redox reaction was taking place in the SMFC. The pH, temperature and conductivity remain 7.5-8.0, 27(±2°C and 10.6-18.2 mS/cm throughout the operation. The biodegradation pathway was studied by the gas chromatography coupled with mass spectroscopy technique, suggested the preferential cleavage of the azo bond as the initial step resulting in to aromatic amines. Thus, a combined anaerobic-aerobic process using SMFC coupled with activated sludge process can be a viable option for effective degradation of complex dye substrates along with energy (bioelectricity) recovery.

Sulphoxidation reaction catalysed by myeloperoxidase from human leucocytes.

PubMed Central

Capeillère-Blandin, C; Martin, C; Gaggero, N; Pasta, P; Carrea, G; Colonna, S

1998-01-01

The oxidation of alkyl aryl sulphides by myeloperoxidase (MPO) at the expense of hydrogen peroxide was investigated under steady-state conditions. The sulphide concentration effect was studied under saturating H2O2 concentrations at pH 5.0 and 20 degreesC. The kinetic constants, kcat and Km, of the different substrates were determined and the values were in the 1-10 s-1 range and around 43+/-26 microM respectively, whatever the sulphide considered. In the case of p-substituted thioanisoles, the oxidation rate was dependent upon the substituent effect. The correlation of log(kcat) with the substituent constants (sigma+ values) (Hammett equation) could be explained by a reaction mechanism involving the enzyme compound II and a sulphenium radical cation. This conclusion was also supported by spectrophotometric analysis of catalytic intermediates of the enzyme, showing the accumulation of compound II. Moreover, chiral HPLC analyses showed that MPO oxidation of alkyl aryl sulphides produced the corresponding (R)-sulphoxides with a low enantioselectivity (4-8%). Chloride ion effects on the MPO-catalysed oxygenation of sulphides were also studied. Chloride acted as a substrate for MPO and as an activator in MPO-catalysed sulphoxidation. Inhibition occurred at chloride concentrations above 120 mM, whereas below 120 mM, chloride increased the reaction rate when using p-tolyl methyl sulphide as the substrate. In the presence of 100 mM chloride the catalytic efficiency (kcat/Km) of MPO increased 3-4-fold, whatever the sulphide considered, but racemic products were obtained. These data have been interpreted in the light of known structural information on the accessibility of the distal haem cavity. PMID:9742209

Valorification of crude glycerol for pure fractions of docosahexaenoic acid and β-carotene production by using Schizochytrium limacinum and Blakeslea trispora.

PubMed

Bindea, Maria; Rusu, Bogdan; Rusu, Alexandru; Trif, Monica; Leopold, Loredana Florina; Dulf, Francisc; Vodnar, Dan Cristian

2018-06-16

The goal of this research is the investigation of a way to maximize the production of docosahexaenoic acid (DHA) and β-carotene by optimizing the culture conditions of their sources, microalgae Schizochytrium limacinum and fungus Blakeslea trispora respectively, in a fermentation medium. The influencing factors in the fermentation process for producing DHA and β-carotene have proven to be: the concentration of carbon source (different glycerol crude and pure concentrations) for both of them, and in particular temperature for DHA and pH for β-carotene. Testing the effect of these parameters was determined: biomass, DHA and β-carotene concentration. The highest production by S. limacinum was obtained at 25 °C, while using a quantity of 90 g/L of glycerol (crude or pure) as a carbon source. Temperature was the main factor that influenced the biosynthesis of DHA. The quantification of DHA was made by GC-MS chromatography, followed by a purification process, with the end result of DHA in pure phase. The maximum quantities for β-carotene production were obtained with pH 7 and 60 g/L of crude glycerol. The results highlight the possibility of using crude glycerol as a low-cost substrates for growth of microalgae S. limacinum and of fungus B. trispora in order to obtain the crucial molecules: docosahexaenoic acid and β-carotene.

Pseudomonas sp. BUP6, a novel isolate from Malabari goat produces an efficient rhamnolipid type biosurfactant.

PubMed

Priji, Prakasan; Sajith, Sreedharan; Unni, Kizhakkepowathial Nair; Anderson, Robin C; Benjamin, Sailas

2017-01-01

This study describes the characteristics of a biosurfactant produced by Pseudomonas sp. BUP6, a rumen bacterium, and optimization of parameters required for its production. Initial screening of five parameters (pH, temperature, agitation, incubation, and substrate concentration) was carried out employing Plackett-Burman design, which reduced the number of parameters to 3 (pH, temperature, and incubation) according to their significance on the yield of biosurfactant. A suitable statistical model for the production of biosurfactant by Pseudomonas sp. BUP6 was established according to Box-Behnken design, which resulted in 11% increase (at pH 7, 35 °C, incubation 75 h) in the yield (2070 mg L -1 ) of biosurfactant. The biosurfactant was found stable at a wide range of pH (3-9) with 48 mg L -1 critical micelle concentration; and maintained over 90% of its emulsification ability even after boiling and in presence of sodium chloride (0.5%). The highest cell hydrophobicity (37%) and emulsification (69%) indices were determined with groundnut oil and kerosene, respectively. The biosurfactant was found to inhibit the growth and adhesion of E. coli and S. aureus significantly. From the phytotoxicity studies, the biosurfactant did not show any adverse effect on the germinating seeds of rice and green gram. The structural characterization of biosurfactant employing orcinol method, thin layer chromatography and FT-IR indicated that it is a rhamnolipid (glycolipid). Thus, Pseudomonas sp. BUP6, a novel isolate from Malabari goat is demonstrated as a producer of an efficient rhamnolipid type biosurfactant suitable for application in various industries. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure of a microbial community in soil after prolonged addition of low levels of simulated acid rain

PubMed

Pennanen; Fritze; Vanhala; Kiikkila; Neuvonen; Baath

1998-06-01

Humus samples were collected 12 growing seasons after the start of a simulated acid rain experiment situated in the subarctic environment. The acid rain was simulated with H2SO4, a combination of H2SO4 and HNO3, and HNO3 at two levels of moderate acidic loads close to the natural anthropogenic pollution levels of southern Scandinavia. The higher levels of acid applications resulted in acidification, as defined by humus chemistry. The concentrations of base cations decreased, while the concentrations of exchangeable H+, Al, and Fe increased. Humus pH decreased from 3.83 to 3.65. Basal respiration decreased with decreasing humus pH, and total microbial biomass, measured by substrate-induced respiration and total amount of phospholipid fatty acids (PLFA), decreased slightly. An altered PLFA pattern indicated a change in the microbial community structure at the higher levels of acid applications. In general, branched fatty acids, typical of gram-positive bacteria, increased in the acid plots. PLFA analysis performed on the bacterial community growing on agar plates also showed that the relative amount of PLFA specific for gram-positive bacteria increased due to the acidification. The changed bacterial community was adapted to the more acidic environment in the acid-treated plots, even though bacterial growth rates, estimated by thymidine and leucine incorporation, decreased with pH. Fungal activity (measured as acetate incorporation into ergosterol) was not affected. This result indicates that bacteria were more affected than fungi by the acidification. The capacity of the bacterial community to utilize 95 different carbon sources was variable and only showed weak correlations to pH. Differences in the toxicities of H2SO4 and HNO3 for the microbial community were not found.

The position of an arginine residue influences substrate affinity and K+ coupling in the human glutamate transporter, EAAT1.

PubMed

Ryan, Renae M; Kortt, Nicholas C; Sirivanta, Tan; Vandenberg, Robert J

2010-07-01

Glutamate is the predominant excitatory neurotransmitter in the mammalian central nervous system and extracellular glutamate levels are controlled by a family of transporters known as excitatory amino acid transporters (EAATs). The EAATs transport glutamate and aspartate with similar micromolar affinities and this transport is coupled to the movement of Na(+), K(+), and H(+). The crystal structure of a prokaryotic homologue of the EAATs, aspartate transporter from Pyrococcus horokoshii (Glt(Ph)), has yielded important insights into the architecture of this transporter family. Glt(Ph) is a Na(+)-dependent transporter that has significantly higher affinity for aspartate over glutamate and is not coupled to H(+) or K(+). The highly conserved carboxy-terminal domains of the EAATs and Glt(Ph) contain the substrate and ion binding sites, however, there are a couple of striking differences in this region that we have investigated to better understand the transport mechanism. An arginine residue is in close proximity to the substrate binding site of both Glt(Ph) and the EAATs, but is located in transmembrane domain (TM) 8 in the EAATs and hairpin loop 1 (HP1) of Glt(Ph). Here we report that the position of this arginine residue can explain some of the functional differences observed between the EAATs and Glt(Ph). Moving the arginine residue from TM8 to HP1 in EAAT1 results in a transporter that has significantly increased affinity for both glutamate and aspartate and is K(+) independent. Conversely, moving the arginine residue from HP1 to TM8 in Glt(Ph) results in a transporter that has reduced affinity for aspartate.

Optimisation of α-terpineol production by limonene biotransformation using Penicillium digitatum DSM 62840.

PubMed

Tai, Ya-Nan; Xu, Min; Ren, Jing-Nan; Dong, Man; Yang, Zi-Yu; Pan, Si-Yi; Fan, Gang

2016-02-01

In this study, (R)-(+)-limonene biotransformation using three fungal strains was compared. Penicillium digitatum DSM 62840 was distinguished for its capacity to transform limonene into α-terpineol with high regioselectivity. Growth kinetics in submerged liquid culture and the effects of growth phase and contact time on biotransformation were studied using this strain. Substrate concentration, co-solvent selection, and cultivation conditions were subsequently optimised. The maximum concentration of α-terpineol (833.93 mg L(-1)) was obtained when the pre-culture medium was in medium log-phase by adding 840 mg L(-1) substrate dissolved in ethanol and cultivation was performed at 24 °C, 150 rpm, and pH 6.0 for 12 h. Addition of small amounts of (R)-(+)-limonene (84 mg L(-1)) at the start of fungal log-phase growth yielded a 1.5-fold yield of α-terpineol, indicating that the enzyme was inducible. Among these three strains tested, P. digitatum DSM 62840 was proved to be an efficient biocatalyst to transform (R)-(+)-limonene to α-terpineol. Further studies revealed that the optimal growth phase for biotransformation was in the medium log phase of this strain. The biotransformation represented a wide tolerance of temperature; α-terpineol concentration underwent no significant change at 8-32 °C. The biotransformation could also be performed using resting cells. © 2015 Society of Chemical Industry.

Novel phacB-encoded cytochrome P450 monooxygenase from Aspergillus nidulans with 3-hydroxyphenylacetate 6-hydroxylase and 3,4-dihydroxyphenylacetate 6-hydroxylase activities.

PubMed

Ferrer-Sevillano, Francisco; Fernández-Cañón, José M

2007-03-01

Aspergillus nidulans catabolizes phenylacetate (PhAc) and 3-hydroxy-, 4-hydroxy-, and 3,4-dihydroxyphenylacetate (3-OH-PhAc, 4-OH-PhAc, and 3,4-diOH-PhAc, respectively) through the 2,5-dihydroxyphenylacetate (homogentisic acid) catabolic pathway. Using cDNA subtraction techniques, we isolated a gene, denoted phacB, which is strongly induced by PhAc (and its hydroxyderivatives) and encodes a new cytochrome P450 (CYP450). A disrupted phacB strain (delta phacB) does not grow on 3-hydroxy-, 4-hydroxy-, or 3,4-dihydroxy-PhAc. High-performance liquid chromatography and gas chromatography-mass spectrum analyses of in vitro reactions using microsomes from wild-type and several A. nidulans mutant strains confirmed that the phacB-encoded CYP450 catalyzes 3-hydroxyphenylacetate and 3,4-dihydroxyphenylacetate 6-hydroxylations to generate 2,5-dihydroxyphenylacetate and 2,4,5-trihydroxyphenylacetate, respectively. Both of these compounds are used as substrates by homogentisate dioxygenase. This cytochrome P450 protein also uses PhAc as a substrate to generate 2-OH-PhAc with a very low efficiency. The phacB gene is the first member of a new CYP450 subfamily (CYP504B).

Novel phacB-Encoded Cytochrome P450 Monooxygenase from Aspergillus nidulans with 3-Hydroxyphenylacetate 6-Hydroxylase and 3,4-Dihydroxyphenylacetate 6-Hydroxylase Activities▿

PubMed Central

Ferrer-Sevillano, Francisco; Fernández-Cañón, José M.

2007-01-01

Aspergillus nidulans catabolizes phenylacetate (PhAc) and 3-hydroxy-, 4-hydroxy-, and 3,4-dihydroxyphenylacetate (3-OH-PhAc, 4-OH-PhAc, and 3,4-diOH-PhAc, respectively) through the 2,5-dihydroxyphenylacetate (homogentisic acid) catabolic pathway. Using cDNA subtraction techniques, we isolated a gene, denoted phacB, which is strongly induced by PhAc (and its hydroxyderivatives) and encodes a new cytochrome P450 (CYP450). A disrupted phacB strain (ΔphacB) does not grow on 3-hydroxy-, 4-hydroxy-, or 3,4-dihydroxy-PhAc. High-performance liquid chromatography and gas chromatography-mass spectrum analyses of in vitro reactions using microsomes from wild-type and several A. nidulans mutant strains confirmed that the phacB-encoded CYP450 catalyzes 3-hydroxyphenylacetate and 3,4-dihydroxyphenylacetate 6-hydroxylations to generate 2,5-dihydroxyphenylacetate and 2,4,5-trihydroxyphenylacetate, respectively. Both of these compounds are used as substrates by homogentisate dioxygenase. This cytochrome P450 protein also uses PhAc as a substrate to generate 2-OH-PhAc with a very low efficiency. The phacB gene is the first member of a new CYP450 subfamily (CYP504B). PMID:17189487

Photocatalytic water oxidation with iron oxide hydroxide (rust) nanoparticles

NASA Astrophysics Data System (ADS)

Shelton, Timothy L.; Bensema, Bronwyn L.; Brune, Nicholas K.; Wong, Christopher; Yeh, Max; Osterloh, Frank E.

2017-01-01

Hematite has attracted considerable interest as a photoanode material for water oxidation under visible illumination. Here, we explore the limits of photocatalytic water oxidation activity with iron (III) oxide hydroxide nanocrystals and NaIO4 as a sacrificial electron acceptor (E=1.63 V NHE at pH=0.5). The sol was prepared by hydrolysis of FeCl3 in boiling 0.002-M HCl solution and confirmed to mainly consist of ß-FeO(OH) (akaganéite) particles with 5 to 15 nm diameter. From a 0.01 M aqueous NaIO4 solution, the sol evolves between 4.5 and 35.2 μmol O2 h-1, depending on pH, light intensity (>400 nm, 290 to 700 mW cm-2), ß-FeO(OH), and NaIO4 concentration. The activity increases with pH, and depends linearly on light intensity and photocatalyst amount, and it varies with sacrificial electron donor concentration. Under optimized conditions, the apparent quantum efficiency is 0.19% (at 400 nm and 460 mW cm-2), and the turnover number is 2.58 based on total ß-FeO(OH). Overall, the efficiency of the ß-FeO(OH)/NaIO4 photocatalytic system is limited by electron hole recombination and by particle aggregation over longer irradiation times (24 h). Lastly, surface photovoltage measurements on ß-FeO(OH) films on fluorine doped tin oxide substrate confirm a 2.15 eV effective band gap for the material.

Characterization of a uronate dehydrogenase from Thermobispora bispora for production of glucaric acid from hemicellulose substrate.

PubMed

Li, Yaxian; Xue, Yemin; Cao, Zhigang; Zhou, Tao; Alnadari, Fawze

2018-06-23

A thermostable uronate dehydrogenase Tb-UDH from Thermobispora bispora was over-expressed in Escherichia coli using the T7 polymerase expression system. The Tb-UDH was purified by metal affinity chromatography, and gave a single band on SDS-PAGE. The maximum activity on glucuronic acid was found at 60 °C and pH 7.0. The purified enzyme retained over 58% of its activity after holding a pH ranging from 7.0 to 7.5 for 1 h at 60 °C. The K m and V max values of the purified Tb-UDH for Glucuronic acid (GluUA) were 0.165 mM and 117.7 U mg -1 , respectively, those for galacturonic acid (GalUA) were 0.115 mM and 104.2 U mg -1 , respectively, and those for NAD + were 0.120 mM and 133.3 U mg -1 , respectively; the turnover number (k cat ) with GluUA as a substrate was higher than that with GalUA; however, the Michaelis constant (K m ) for GalUA was lower than that for GluUA. After 60 min of incubation at 50 °C, Tb-UDH exhibited a conversion ratio for glucuronic acid to the glucaric acid of 84% on chemical reagent and 81.3% on hydrolysates from breech xylans formed by xylanase and α-glucuronidase. This work shows that biocatalytic routes have great potential for the conversion of hemicellulose substrate into value-added products derived from renewable biomass. TOC GRAPHIC: (A) The structure of the xylan is described and the site of action of the xylan degrading enzyme is indicated. (B) The effect of substrate concentration on recombinant Tb-UDH activity when galacturonic acid was used as substrate. (C) SDS-PAGE analysis of E. coli BL21 (DE3) harboring pET-20b(+) and pET-20b-Tb-UDH. (D) Oxidative conversion of glucuronic acid from a beechwood xylan to glucaric acid.

A wide range optical pH sensor for living cells using Au@Ag nanoparticles functionalized carbon nanotubes based on SERS signals.

PubMed

Chen, Peng; Wang, Zhuyuan; Zong, Shenfei; Chen, Hui; Zhu, Dan; Zhong, Yuan; Cui, Yiping

2014-10-01

p-Aminothiophenol (pATP) functionalized multi-walled carbon nanotubes (MWCNTs) have been demonstrated as an efficient pH sensor for living cells. The proposed sensor employs gold/silver core-shell nanoparticles (Au@Ag NPs) functionalized MWCNTs hybrid structure as the surface-enhanced Raman scattering (SERS) substrate and pATP molecules as the SERS reporters, which possess a pH-dependent SERS performance. By using MWCNTs as the substrate to be in a state of aggregation, the pH sensing range could be extended to pH 3.0∼14.0, which is much wider than that using unaggregated Au@Ag NPs without MWCNTs. Furthermore, the pH-sensitive performance was well retained in living cells with a low cytotoxicity. The developed SERS-active MWCNTs-based nanocomposite is expected to be an efficient intracellular pH sensor for bio-applications.

Pectate hydrolases of parsley (Petroselinum crispum) roots.

PubMed

Flodrová, Dana; Dzúrovä, Mária; Lisková, Desana; Mohand, Fairouz Ait; Mislovicová, Danica; Malovícová, Anna; Voburka, Zdenek; Omelková, Jirina; Stratilová, Eva

2007-01-01

The presence of various enzyme forms with terminal action pattern on pectate was evaluated in a protein mixture obtained from parsley roots. Enzymes found in the soluble fraction of roots (juice) were purified to homogeneity according to SDS-PAGE, partially separated by preparative isoelectric focusing and characterized. Three forms with pH optima 3.6, 4.2 and 4.6 clearly preferred substrates with a lower degree of polymerization (oligogalacturonates) while the form with pH optimum 5.2 was a typical exopolygalacturonase [EC 3. 2.1.67] with relatively fast cleavage of polymeric substrate. The forms with pH optima 3.6, 4.2 and 5.2 were released from the pulp, too. The form from the pulp with pH optimum 4.6 preferred higher oligogalacturonates and was not described in plants previously. The production of individual forms in roots was compared with that produced by root cells cultivated on solid medium and in liquid one.

Biohydrogen production from arabinose and glucose using extreme thermophilic anaerobic mixed cultures

PubMed Central

2012-01-01

Background Second generation hydrogen fermentation technologies using organic agricultural and forestry wastes are emerging. The efficient microbial fermentation of hexoses and pentoses resulting from the pretreatment of lingocellulosic materials is essential for the success of these processes. Results Conversion of arabinose and glucose to hydrogen, by extreme thermophilic, anaerobic, mixed cultures was studied in continuous (70°C, pH 5.5) and batch (70°C, pH 5.5 and pH 7) assays. Two expanded granular sludge bed (EGSB) reactors, Rarab and Rgluc, were continuously fed with arabinose and glucose, respectively. No significant differences in reactor performance were observed for arabinose and glucose organic loading rates (OLR) ranging from 4.3 to 7.1 kgCOD m-3 d-1. However, for an OLR of 14.2 kgCOD m-3 d-1, hydrogen production rate and hydrogen yield were higher in Rarab than in Rgluc (average hydrogen production rate of 3.2 and 2.0 LH2 L-1 d-1 and hydrogen yield of 1.10 and 0.75 molH2 mol-1substrate for Rarab and Rgluc, respectively). Lower hydrogen production in Rgluc was associated with higher lactate production. Denaturing gradient gel electrophoresis (DGGE) results revealed no significant difference on the bacterial community composition between operational periods and between the reactors. Increased hydrogen production was observed in batch experiments when hydrogen partial pressure was kept low, both with arabinose and glucose as substrate. Sugars were completely consumed and hydrogen production stimulated (62% higher) when pH 7 was used instead of pH 5.5. Conclusions Continuous hydrogen production rate from arabinose was significantly higher than from glucose, when higher organic loading rate was used. The effect of hydrogen partial pressure on hydrogen production from glucose in batch mode was related to the extent of sugar utilization and not to the efficiency of substrate conversion to hydrogen. Furthermore, at pH 7.0, sugars uptake, hydrogen production and yield were higher than at pH 5.5, with both arabinose and glucose as substrates. PMID:22330180

Bicarbonate alters cellular responses in respiration assays.

PubMed

Krycer, James R; Fisher-Wellman, Kelsey H; Fazakerley, Daniel J; Muoio, Deborah M; James, David E

2017-08-05

Metabolic assay buffers often omit bicarbonate, which is susceptible to alkalinisation in an open environment. Here, we assessed the effect of including bicarbonate in respirometry experiments. By supplementing HEPES-buffered media with low concentrations of bicarbonate, we found increased respiration in adipocytes and hepatocytes, but not myotubes. This was observed across multiple respirometry platforms and was independent of effects on enhanced insulin sensitivity, pH drift, or mitochondrial function. Permeabilised cell experiments suggest that bicarbonate increases substrate availability, likely by acting as a cofactor for carboxylase enzymes. This emphasises the importance of buffer choice in experimental biology. Copyright © 2017 Elsevier Inc. All rights reserved.

Optimization of process factors for self-healing vanadium-based conversion coating on AZ31 magnesium alloy

NASA Astrophysics Data System (ADS)

Li, Kun; Liu, Junyao; Lei, Ting; Xiao, Tao

2015-10-01

A self-healing vanadium-based conversion coating was prepared on AZ31 magnesium alloy. The optimum operating conditions including vanadia solution concentration, pH and treating temperature for obtaining the best corrosion protective vanadia coatings and improved localized corrosion resistance to the magnesium substrate were determined by an orthogonal experiment design. Surface morphology and composition of the resultant conversion coatings were investigated by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The self-healing behavior of the coating was investigated by cross-cut immersion test and electrochemical impedance spectroscopy (EIS) measurements in 3.5% NaCl solution.

Use of Response Surface Methodology to Optimize Culture Conditions for Hydrogen Production by an Anaerobic Bacterial Strain from Soluble Starch

NASA Astrophysics Data System (ADS)

Kieu, Hoa Thi Quynh; Nguyen, Yen Thi; Dang, Yen Thi; Nguyen, Binh Thanh

2016-05-01

Biohydrogen is a clean source of energy that produces no harmful byproducts during combustion, being a potential sustainable energy carrier for the future. Therefore, biohydrogen produced by anaerobic bacteria via dark fermentation has attracted attention worldwide as a renewable energy source. However, the hydrogen production capability of these bacteria depends on major factors such as substrate, iron-containing hydrogenase, reduction agent, pH, and temperature. In this study, the response surface methodology (RSM) with central composite design (CCD) was employed to improve the hydrogen production by an anaerobic bacterial strain isolated from animal waste in Phu Linh, Soc Son, Vietnam (PL strain). The hydrogen production process was investigated as a function of three critical factors: soluble starch concentration (8 g L-1 to 12 g L-1), ferrous iron concentration (100 mg L-1 to 200 mg L-1), and l-cysteine concentration (300 mg L-1 to 500 mg L-1). RSM analysis showed that all three factors significantly influenced hydrogen production. Among them, the ferrous iron concentration presented the greatest influence. The optimum hydrogen concentration of 1030 mL L-1 medium was obtained with 10 g L-1 soluble starch, 150 mg L-1 ferrous iron, and 400 mg L-1 l-cysteine after 48 h of anaerobic fermentation. The hydrogen concentration produced by the PL strain was doubled after using RSM. The obtained results indicate that RSM with CCD can be used as a technique to optimize culture conditions for enhancement of hydrogen production by the selected anaerobic bacterial strain. Hydrogen production from low-cost organic substrates such as soluble starch using anaerobic fermentation methods may be one of the most promising approaches.

Theoretical Study of the Oxidation Behavior of Precipitation Hardening Steel

NASA Astrophysics Data System (ADS)

Pistofidis, N.; Vourlias, G.; Psyllaki, P.; Chrissafis, K.

2010-01-01

The oxidation of precipitation hardening (PH) steels is a rather unexplored area. In the present work an attempt is made is made to estimate the kinetics of a PH steel. For this purpose specimens of the material under examination were isothermally heated at 850, 900 and 950° C for 15 hr. Kinetics was based on TGA results. During heating a thick scale is formed on the substrate surface, which is composed by different oxides. The layer close to the substrate is compact and as a result it impedes corrosion. The mathematical analysis of the collected data shows that the change of the mass of the substrate per unit area versus time is described by a parabolic law.

Characterization of two coleopteran α-amylases and molecular insights into their differential inhibition by synthetic α-amylase inhibitor, acarbose.

PubMed

Channale, Sonal M; Bhide, Amey J; Yadav, Yashpal; Kashyap, Garima; Pawar, Pankaj K; Maheshwari, V L; Ramasamy, Sureshkumar; Giri, Ashok P

2016-07-01

Post-harvest insect infestation of stored grains makes them unfit for human consumption and leads to severe economic loss. Here, we report functional and structural characterization of two coleopteran α-amylases viz. Callosobruchus chinensis α-amylase (CcAmy) and Tribolium castaneum α-amylase (TcAmy) along with their interactions with proteinaceous and non-proteinaceous α-amylase inhibitors. Secondary structural alignment of CcAmy and TcAmy with other coleopteran α-amylases revealed conserved motifs, active sites, di-sulfide bonds and two point mutations at spatially conserved substrate or inhibitor-binding sites. Homology modeling and molecular docking showed structural differences between these two enzymes. Both the enzymes had similar optimum pH values but differed in their optimum temperature. Overall, pattern of enzyme stabilities were similar under various temperature and pH conditions. Further, CcAmy and TcAmy differed in their substrate affinity and catalytic efficiency towards starch and amylopectin. HPLC analysis detected common amylolytic products like maltose and malto-triose while glucose and malto-tetrose were unique in CcAmy and TcAmy catalyzed reactions respectively. At very low concentrations, wheat α-amylase inhibitor was found to be superior over the acarbose as far as complete inhibition of amylolytic activities of CcAmy and TcAmy was concerned. Mechanism underlying differential amylolytic reaction inhibition by acarbose was discussed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Production and characterization of alpha-amylase from mango kernel by Fusarium solani NAIMCC-F-02956 using submerged fermentation.

PubMed

Kumar, Devendra; Yadav, Kaushlesh K; Muthukumar, M; Garg, Neelima

2013-11-01

Microbial production of enzymes using low valued agro industrial wastes is gaining importance globally. Mango is one of the major fruit processed into a variety of products. During processing 40-50% of solid waste is generated in form of peel and stones. After decortications of mango stone, kernel is obtained which is a rich source of starch (upto 60%). It was utilized as a substrate for alpha-amylase production using Fusarium soloni. Maximum alpha-amylase production (0.889 U g(-1)) was recorded using a substrate concentration of 5% (w/v), pH-4 and temperature 30 degrees C on 9th day of incubation. Supplementation of production medium with micronutrients viz., Ca2+, Fe2+ or Mg2+ improved the enzyme production while, Zn2+, B3+ or Mn2+ ions exhibited inhibitory effect. The extracellular protein was precipitated by ammonium sulphate up to 70% saturation, dialyzed and purified (27.84 fold) by gel-exclusion (Sephadex G-75) chromatography. Protein profiling on 12% SDS-PAGE revealed three bands corresponding to 26, 27 and 30 kDa molecular sizes. The optimum amylase activity was achieved at pH 5.0 at 40 degrees C. The Michaelis constant (KM), Vmax and activation energy (-Ea) were found to be 3.7 mg ml(-1), 0.24 U mg(-1) and 42.39 kJ mole(-1), respectively.

Bioethanol production involving recombinant C. thermocellum hydrolytic hemicellulase and fermentative microbes.

PubMed

Das, Saprativ P; Ravindran, Rajeev; Ahmed, Shadab; Das, Debasish; Goyal, Dinesh; Fontes, Carlos M G A; Goyal, Arun

2012-07-01

The enhancement of the biomass productivity of Escherichia coli cells harbouring the truncated 903 bp gene designated as glycoside hydrolase family 43 (GH43) from Clostridium thermocellum showing hemicellulase activity along with its further use in simultaneous saccharification and fermentation (SSF) process is described. (Phosphoric acid) H(3)PO(4)-acetone treatment and ammonia fibre expansion (AFEX) were the pretreatment strategies employed on the leafy biomass of mango, poplar, neem and asoka among various substrates owing to their high hemicellulose content. GH43 showed optimal activity at a temperature of 50 °C, pH 5.4 with stability over a pH range of 5.0-6.2. A 4-fold escalation in growth of the recombinant E. coli cells was observed when grown using repeated batch strategy in LB medium supplemented with glucose as co-substrate. Candida shehatae utilizing pentose sugars was employed for bioethanol production. AFEX pretreatment proved to be better over acid-acetone technique. The maximum ethanol concentration (1.44 g/L) was achieved for AFEX pretreated mango (1%, w/v) followed by poplar with an ethanol titre (1.32 g/L) in shake flask experiments. A 1.5-fold increase in ethanol titre (2.11 g/L) was achieved with mango (1%, w/v) in a SSF process using a table top 2-L bioreactor with 1 L working volume.

Kinetics of the hydrolysis of N-benzoyl-l-serine methyl ester catalysed by bromelain and by papain. Analysis of modifier mechanisms by lattice nomography, computational methods of parameter evaluation for substrate-activated catalyses and consequences of postulated non-productive binding in bromelain- and papain-catalysed hydrolyses

PubMed Central

Wharton, Christopher W.; Cornish-Bowden, Athel; Brocklehurst, Keith; Crook, Eric M.

1974-01-01

1. N-Benzoyl-l-serine methyl ester was synthesized and evaluated as a substrate for bromelain (EC 3.4.22.4) and for papain (EC 3.4.22.2). 2. For the bromelain-catalysed hydrolysis at pH7.0, plots of [S0]/vi (initial substrate concn./initial velocity) versus [S0] are markedly curved, concave downwards. 3. Analysis by lattice nomography of a modifier kinetic mechanism in which the modifier is substrate reveals that concave-down [S0]/vi versus [S0] plots can arise when the ratio of the rate constants that characterize the breakdown of the binary (ES) and ternary (SES) complexes is either less than or greater than 1. In the latter case, there are severe restrictions on the values that may be taken by the ratio of the dissociation constants of the productive and non-productive binary complexes. 4. Concave-down [S0]/vi versus [S0] plots cannot arise from compulsory substrate activation. 5. Computational methods, based on function minimization, for determination of the apparent parameters that characterize a non-compulsory substrate-activated catalysis are described. 6. In an attempt to interpret the catalysis by bromelain of the hydrolysis of N-benzoyl-l-serine methyl ester in terms of substrate activation, the general substrate-activation model was simplified to one in which only one binary ES complex (that which gives rise directly to products) can form. 7. In terms of this model, the bromelain-catalysed hydrolysis of N-benzoyl-l-serine methyl ester at pH7.0, I=0.1 and 25°C is characterized by Km1 (the dissociation constant of ES)=1.22±0.73mm, k (the rate constant for the breakdown of ES to E+products, P)=1.57×10−2±0.32×10−2s−1, Ka2 (the dissociation constant that characterizes the breakdown of SES to ES and S)=0.38±0.06m, and k′ (the rate constant for the breakdown of SES to E+P+S)=0.45±0.04s−1. 8. These parameters are compared with those in the literature that characterize the bromelain-catalysed hydrolysis of α-N-benzoyl-l-arginine ethyl ester and of α-N-benzoyl-l-arginine amide; Km1 and k for the serine ester hydrolysis are somewhat similar to Km and kcat. for the arginine amide hydrolysis and Kas and k′ for the serine ester hydrolysis are somewhat similar to Km and kcat. for the arginine ester hydrolysis. 9. A previous interpretation of the inter-relationships of the values of kcat. and Km for the bromelain-catalysed hydrolysis of the arginine ester and amide substrates is discussed critically and an alternative interpretation involving substantial non-productive binding of the arginine amide substrate to bromelain is suggested. 10. The parameters for the bromelain-catalysed hydrolysis of the serine ester substrate are tentatively interpreted in terms of non-productive binding in the binary complex and a decrease of this type of binding by ternary complex-formation. 11. The Michaelis parameters for the papain-catalysed hydrolysis of the serine ester substrate (Km=52±4mm, kcat.=2.80±0.1s−1 at pH7.0, I=0.1, 25.0°C) are similar to those for the papain-catalysed hydrolysis of methyl hippurate. 12. Urea and guanidine hydrochloride at concentrations of 1m have only small effects on the kinetic parameters for the hydrolysis of the serine ester substrate catalysed by bromelain and by papain. PMID:4455211

Sequencing biological acidification of waste-activated sludge aiming to optimize phosphorus dissolution and recovery.

PubMed

Guilayn, Felipe; Braak, Etienne; Piveteau, Simon; Daumer, Marie-Line

2017-06-01

Phosphorus (P) recovery in wastewater treatment plants (WWTP) as pure crystals such as struvite (MgNH 4 PO 4 .6H 2 O), potassium struvite (KMgPO 4 .6H 2 O) and calcium phosphates (e.g. Ca 3 (PO 4 ) 2 ) is an already feasible technique that permits the production of green and marketable fertilizers and the reduction of operational costs. Commercial crystallizers can recovery more than 90% of soluble P. However, most of the P in WWTP sludge is unavailable for the processes (not dissolved). P solubilization and separation are thus the limiting steps in P-crystallization. With an innovative two-step sequencing acidification strategy, the current study has aimed to improve biological P solubilization on waste-activated sludge (WAS) from a full-scale plant. In the first step (P-release), low charges of organic waste were used as co-substrates of WAS pre-fermentation, seeking to produce volatile fatty acids to feed the P-release by Polyphosphate-accumulating organisms, while keeping its optimal metabolic pH (6-7). In this phase, milk serum, WWTP grease, urban organic waste and collective restaurant waste were individually applied as co-substrates. In the second step (P-dissolution), pH 4 was aimed at as it allows the dissolution of the most common precipitated species of P. Biological acidification was performed by white sugar addition, as a carbohydrate-rich organic waste model, which was compared to chemical acidification by HCl (12M) addition. With short retention times (48-96 h) and without inoculum application, all experiences succeeded on P solubilization (37-55% of soluble P), principally when carbohydrate-rich co-substrates were applied. Concentrations from 270 to 450 mg [Formula: see text] were achieved. [Formula: see text].

Characterization of a newly synthesized carbonyl reductase and construction of a biocatalytic process for the synthesis of ethyl (S)-4-chloro-3-hydroxybutanoate with high space-time yield.

PubMed

You, Zhong-Yu; Liu, Zhi-Qiang; Zheng, Yu-Guo

2014-02-01

A carbonyl reductase (SCR2) gene was synthesized and expressed in Escherichia coli after codon optimization to investigate its biochemical properties and application in biosynthesis of ethyl (S)-4-chloro-3-hydroxybutanoate ((S)-CHBE), which is an important chiral synthon for the side chain of cholesterol-lowering drug. The recombinant SCR2 was purified and characterized using ethyl 4-chloro-3-oxobutanoate (COBE) as substrate. The specific activity of purified enzyme was 11.9 U mg(-1). The optimum temperature and pH for enzyme activity were 45 °C and pH 6.0, respectively. The half-lives of recombinant SCR2 were 16.5, 7.7, 2.2, 0.41, and 0.05 h at 30 °C, 35 °C, 40 °C, 45 °C, and 50 °C, respectively, and it was highly stable in acidic environment. This SCR2 displayed a relatively narrow substrate specificity. The apparent K m and V max values of purified enzyme for COBE are 6.4 mM and 63.3 μmol min(-1) mg(-1), respectively. The biocatalytic process for the synthesis of (S)-CHBE was constructed by this SCR2 in an aqueous-organic solvent system with a substrate fed-batch strategy. At the final COBE concentration of 1 M, (S)-CHBE with yield of 95.3% and e.e. of 99% was obtained after 6-h reaction. In this process, the space-time yield per gram of biomass (dry cell weight, DCW) and turnover number of NADP(+) to (S)-CHBE were 26.5 mmol L(-1) h(-1) g(-1) DCW and 40,000 mol/mol, respectively, which were the highest values as compared with other works.

The Crude Skin Secretion of the Pepper Frog Leptodactylus labyrinthicus Is Rich in Metallo and Serine Peptidases

PubMed Central

Libério, Michelle da Silva; Bastos, Izabela M. D.; Pires Júnior, Osmindo R.; Fontes, Wagner; Santana, Jaime M.; Castro, Mariana S.

2014-01-01

Peptidases are ubiquitous enzymes involved in diverse biological processes. Fragments from bioactive peptides have been found in skin secretions from frogs, and their presence suggests processing by peptidases. Thus, the aim of this work was to characterize the peptidase activity present in the skin secretion of Leptodactylus labyrinthicus. Zymography revealed the presence of three bands of gelatinase activity of approximately 60 kDa, 66 kDa, and 80 kDa, which the first two were calcium-dependent. These three bands were inhibited either by ethylenediaminetetraacetic acid (EDTA) and phenathroline; thus, they were characterized as metallopeptidases. Furthermore, the proteolytic enzymes identified were active only at pH 6.0–10.0, and their activity increased in the presence of CHAPS or NaCl. Experiments with fluorogenic substrates incubated with skin secretions identified aminopeptidase activity, with cleavage after leucine, proline, and alanine residues. This activity was directly proportional to the protein concentration, and it was inhibited in the presence of metallo and serine peptidase inhibitors. Besides, the optimal pH for substrate cleavage was determined to be 7.0–8.0. The results of the in gel activity assay showed that all substrates were hydrolyzed by a 45 kDa peptidase. Gly-Pro-AMC was also cleaved by a peptidase greater than 97 kDa. The data suggest the presence of dipeptidyl peptidases (DPPs) and metallopeptidases; however, further research is necessary. In conclusion, our work will help to elucidate the implication of these enzymatic activities in the processing of the bioactive peptides present in frog venom, expanding the knowledge of amphibian biology. PMID:24906116

Impact of pH on Urine Chemistry Assayed on Roche Analyzers.

PubMed

Cohen, R; Alkouri, R; Tostivint, I; Djiavoudine, S; Mestari, F; Dever, S; Atlan, G; Devilliers, C; Imbert-Bismut, F; Bonnefont-Rousselot, D; Monneret, D

2017-10-01

The pH may impact the concentration of certain urinary parameters, making urine pre-treatment questionable. 1) Determining the impact of pH in vitro on the urinary concentration of chemistry parameters assayed on Roche Modular analyzers. 2) Evaluating whether concentrations depended on pH in non-pretreated urines from patients. 1) The optimal urinary pH values for each measurement were: 6.3 ± 0.8 (amylase), < 5.5 (calcium and magnesium), < 6.5 (phosphorus), > 6.5 (uric acid). Urinary creatinine, sodium and urea concentrations were not pH-dependent. 2) In urines from patients, the pH was negatively associated with the concentration of some urinary parameters. However, concentrations of all the parameters were strongly and positively correlated with urinary creatinine, and relationships with pH were no longer evidenced after creatinine-normalization. The need for urine pH adjustment does not seem necessary when considering renal function. However, from an analytical and accreditation standpoint, the relationship between urine pH and several parameters justifies its measurement.

21 CFR 868.1170 - Indwelling blood hydrogen ion concentration (pH) analyzer.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Indwelling blood hydrogen ion concentration (pH... Indwelling blood hydrogen ion concentration (pH) analyzer. (a) Identification. An indwelling blood hydrogen... used to measure, in vivo, the hydrogen ion concentration (pH) in blood to aid in determining the...

21 CFR 868.1170 - Indwelling blood hydrogen ion concentration (pH) analyzer.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Indwelling blood hydrogen ion concentration (pH... Indwelling blood hydrogen ion concentration (pH) analyzer. (a) Identification. An indwelling blood hydrogen... used to measure, in vivo, the hydrogen ion concentration (pH) in blood to aid in determining the...

21 CFR 868.1170 - Indwelling blood hydrogen ion concentration (pH) analyzer.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Indwelling blood hydrogen ion concentration (pH... Indwelling blood hydrogen ion concentration (pH) analyzer. (a) Identification. An indwelling blood hydrogen... used to measure, in vivo, the hydrogen ion concentration (pH) in blood to aid in determining the...

21 CFR 868.1170 - Indwelling blood hydrogen ion concentration (pH) analyzer.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Indwelling blood hydrogen ion concentration (pH... Indwelling blood hydrogen ion concentration (pH) analyzer. (a) Identification. An indwelling blood hydrogen... used to measure, in vivo, the hydrogen ion concentration (pH) in blood to aid in determining the...

21 CFR 868.1170 - Indwelling blood hydrogen ion concentration (pH) analyzer.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Indwelling blood hydrogen ion concentration (pH... Indwelling blood hydrogen ion concentration (pH) analyzer. (a) Identification. An indwelling blood hydrogen... used to measure, in vivo, the hydrogen ion concentration (pH) in blood to aid in determining the...

Nucleation, growth, and repair of a cobalt-based oxygen evolving catalyst.

PubMed

Surendranath, Yogesh; Lutterman, Daniel A; Liu, Yi; Nocera, Daniel G

2012-04-11

The mechanism of nucleation, steady-state growth, and repair is investigated for an oxygen evolving catalyst prepared by electrodeposition from Co(2+) solutions in weakly basic electrolytes (Co-OEC). Potential step chronoamperometry and atomic force microscopy reveal that nucleation of Co-OEC is progressive and reaches a saturation surface coverage of ca. 70% on highly oriented pyrolytic graphite substrates. Steady-state electrodeposition of Co-OEC exhibits a Tafel slope approximately equal to 2.3 × RT/F. The electrochemical rate law exhibits a first order dependence on Co(2+) and inverse orders on proton (third order) and proton acceptor, methylphosphonate (first order for 1.8 mM ≤ [MeP(i)] ≤ 18 mM and second order dependence for 32 mM ≤ [MeP(i)] ≤ 180 mM). These electrokinetic studies, combined with recent XAS studies of catalyst structure, suggest a mechanism for steady state growth at intermediate MeP(i) concentration (1.8-18 mM) involving a rapid solution equilibrium between aquo Co(II) and Co(III) hydroxo species accompanied with a rapid surface equilibrium involving electrolyte dissociation and deprotonation of surface bound water. These equilibria are followed by a chemical rate-limiting step for incorporation of Co(III) into the growing cobaltate clusters comprising Co-OEC. At higher concentrations of MeP(i) ([MeP(i)] ≥ 32 mM), MePO(3)(2-) equilibrium binding to Co(II) in solution is suggested by the kinetic data. Consistent with the disparate pH profiles for oxygen evolution electrocatalysis and catalyst formation, NMR-based quantification of catalyst dissolution as a function of pH demonstrates functional stability and repair at pH values >6 whereas catalyst corrosion prevails at lower pH values. These kinetic insights provide a basis for developing and operating functional water oxidation (photo)anodes under benign pH conditions. © 2012 American Chemical Society

Phosphotyrosine as a substrate of acid and alkaline phosphatases.

PubMed

Apostoł, I; Kuciel, R; Wasylewska, E; Ostrowski, W S

1985-01-01

A new spectrophotometric method for following dephosphorylation of phosphotyrosine has been described. The absorption spectra of phosphotyrosine and tyrosine were plotted over the pH range from 3 to 9. The change in absorbance accompanying the conversion of phosphotyrosine to tyrosine was the greatest at 286 nm. The difference absorption coefficients were calculated for several pH values. Dephosphorylation of phosphotyrosine by acid phosphatases from human prostate gland, from wheat germ and potatoes obeys the Michaelis-Menten equation, whereas alkaline phosphatases calf intestine and E. coli are inhibited by excess of substrate.

The influence of human neutrophils on N-nitrosodimethylamine (NDMA) synthesis.

PubMed

Jabłoński, Jakub; Jabłońska, Ewa; Iwanowska, Jolanta; Marcińczyk, Magda; Moniuszko-Jakoniuk, Janina

2006-01-01

N-nitrozodimethyloamine (NDMA) is a carcinogenic compound that can be formed in vivo. NDMA is synthesized from precursors-amines and nitrosating agents. Nitrosating agents are formed through the reaction of oxide, reactive oxygen species and nitric oxide (NO). Human neutrophils (PMN) are an important source of the most reactive oxygen species as well as of the nitric oxide. The increase in oxygen metabolism of PMN can lead to the increase nitrosating agent and nitroso-forms. Inflammatory process is associated with locally decreased pH that may favor nitrosation reaction. In the present study, we estimated the NDMA synthesis by LPS-stimulated PMN in the presence of the iNOS inhibitor--N-nitro-L-arginine methyl ester (L-NAME). In the nitrosation reaction dimethylamine (DMA) was used as substrat. The viability of the cells was measured by cytometric method. NDMA concentrations the culture media was measured by GCMS method. NO production was estimated by Griess's method. Expression of iNOS was determined by western blotting. Results obtained showed that DMA nitrosation is most effective in pH between 3-4.5. Nonstimulated PMN produced lower concentrations of NO than LPS-stimulated cells (1.27 microg/cm3 and 1.57 microg/cm3, respectively). In the culture of nonstimulated PMN supplemented with DMA, there was NDMA (mean--0.99 ng/cm3). In the culture of LPS-stimulated PMN in the presence of DMA, the concentration of NDMA was higher than in the culture of nonstimulated PMN (median--1.45 ng/cm3). In the supernatants of cells incubated without DMA and with DMA, LPS and L-NAME, no NDMA was detected. These results indicate that PMN can be one of sources of nitrosating agents and can play a role in endogenous NDMA synthesis. Stimulation of PMN can lead to the increase of NDMA concentration following the increase of NO production. Different pathological conditions associated with PMN activation as well as the decreased pH may favor endogenous NDMA synthesis.

Comparative evaluation of the efficiency of low-cost adsorbents and ligninolytic fungi to remove a combination of xenoestrogens and pesticides from a landfill leachate and abate its phytotoxicity.

PubMed

Loffredo, Elisabetta; Castellana, Giancarlo

2015-01-01

In this study, two widely available low-cost adsorbents, almond shells and a green compost, and two ligninolytic fungi, Pleurotus ostreatus and Stereum hirsutum, were used to remove organic contaminants from a landfill leachate (LLe) and abate its phytotoxicity. The methodology adopted was based on the occurrence of two simultaneous processes, such as adsorption and bioremoval. The leachate was artificially contaminated with a mixture of the xenoestrogens bisphenol A (BPA), ethynilestadiol (EE2) and 4-n-nonylphenol (NP), the herbicide linuron and the insecticide dimethoate at concentrations of 10, 1, 1, 10 and 10 mg L(-1), respectively. Three adsorption substrates were prepared: potato dextrose agar alone or the same incorporating each adsorbent. The substrates were either not inoculated or inoculated with each fungus, separately, before to be superimposed on LLe. After 2 months, the residual amount of each contaminant, the electrical conductivity, the pH and the content of total phenols were measured in treated LLe. Germination assays using lettuce, ryegrass and radish were performed to evaluate LLe phytotoxicity. The combination substrate+P. ostreatus showed the best results with average removals of 88, 96, 99, 58 and 46% for BPA, EE2, NP, linuron and dimethoate, respectively. The same treatment considerably reduced the phenol content in LLe compared to no treatment. The combination substrate+S. hirsutum produced average removals of 39, 71, 100, 61 and 32% for BPA, EE2, NP, linuron and dimethoate, respectively. Also uninoculated substrates showed relevant adsorption capacities towards the five contaminants. Most treatments significantly reduced LLe phytotoxicity, especially on lettuce. The best results were obtained with the treatment compost+S. hirsutum, which produced root and shoot lengths and seedling biomass of lettuce, respectively, 2.3, 3.3, and 1.9 times those measured in untreated LLe. In general, germination results were negatively correlated with LLe properties like the residual amount of the contaminants, the electrical conductivity and the pH. These results show that the methodology adopted in the study, i.e., combined adsorption/biodegradation, is suitable not only to remove xenobiotic contaminants from the leachate but also to reduce considerably its inhibition on seed germination.

Kinetic behaviour of calf intestinal alkaline phosphatase with pNPP.

PubMed

Chaudhuri, Gouri; Chatterjee, Saswata; Venu-Babu, P; Ramasamy, K; Thilagaraj, W Richard

2013-02-01

The hydrolysis of p-nitrophenyl phosphate (pNPP) by calf intestinal alkaline phosphatase (CIAP) was investigated with respect to kinetic parameters such as V(max), K(m) and K(cat) under varying pH, buffers, substrate concentration, temperature and period of incubation. Highest activity was obtained with Tris-HCl at pH 11, while in the case of glycine-NaOH buffer the peak activity was recorded at pH 9.5. The enzyme showed the following kinetic characteristics with pNPP in 50 mM Tris-HCl at pH 11 and 100 mM glycine-NaOH at pH 9.5 at an incubation temperature of 37 degrees C: V(max), 3.12 and 1.6 micromoles min(-1) unit(-1); K(m), 7.6 x 10(-4) M and 4 x 10(-4) M; and K(cat), 82.98 s(-1) and 42.55 s(-1), respectively. CIAP displayed a high temperature optimum of 45 degrees C at pH 11. The kinetic behaviour of the enzyme under different parameters suggested that the enzyme might undergo subtle conformational changes in response to the buffers displaying unique characteristics. Bioprecipitation of Cu2+ from 50 ppm of CuCl2 solution was studied where 64.3% of precipitation was obtained. P(i) generated from CIAP-mediated hydrolysis of pNPP was found to bind with copper and precipitated as copper-phosphate. Thus, CIAP could be used as a test candidate in bioremediation of heavy metals from industrial wastes through generation of metal-phosphate complexes.

Immobilization of an enzyme from a Fusarium fungus WZ-I for chlorpyrifos degradation.

PubMed

Xie, Hui; Zhu, Lusheng; Ma, Tingting; Wang, Jun; Wang, Jinhua; Su, Jun; Shao, Bo

2010-01-01

The free enzyme extracted from WZ-I, which was identified as Fusarium LK. ex Fx, could effectively degrade chlorpyrifos, an organophosphate insecticide. The methods of immobilizing this free enzyme and determined its degradation-related characteristics were investigated. The properties of the immobilized enzyme were compared with those of the free enzyme. The optimal immobilization of the enzyme was achieved in a solution of 30 g/L sodium alginate at 4 degrees C for 4-12 hr. The immobilized enzyme showed the maximal activity at pH 8.0, 45 degrees C. The maximum initial rate and the substrate concentration of the immobilized enzyme were less than that of the free enzyme. The immobilized enzyme, therefore, had a higher capacity to withstand a broader range of temperatures and pH conditions than the free enzyme. With varying pH and temperatures, the immobilized enzyme was more active than the free enzyme in the degradation reaction. In addition, the immobilized enzyme exhibited only a slight loss in its initial activity, even after three repeated uses. The results showed that the immobilized enzyme was more resistant to different environmental conditions, suggesting that it was viable for future practical use.

An integrated field-effect microdevice for monitoring membrane transport in Xenopus laevis oocytes via lateral proton diffusion.

PubMed

Schaffhauser, Daniel Felix; Patti, Monica; Goda, Tatsuro; Miyahara, Yuji; Forster, Ian Cameron; Dittrich, Petra Stephanie

2012-01-01

An integrated microdevice for measuring proton-dependent membrane activity at the surface of Xenopus laevis oocytes is presented. By establishing a stable contact between the oocyte vitelline membrane and an ion-sensitive field-effect (ISFET) sensor inside a microperfusion channel, changes in surface pH that are hypothesized to result from facilitated proton lateral diffusion along the membrane were detected. The solute diffusion barrier created between the sensor and the active membrane area allowed detection of surface proton concentration free from interference of solutes in bulk solution. The proposed sensor mechanism was verified by heterologously expressing membrane transport proteins and recording changes in surface pH during application of the specific substrates. Experiments conducted on two families of phosphate-sodium cotransporters (SLC20 & SLC34) demonstrated that it is possible to detect phosphate transport for both electrogenic and electroneutral isoforms and distinguish between transport of different phosphate species. Furthermore, the transport activity of the proton/amino acid cotransporter PAT1 assayed using conventional whole cell electrophysiology correlated well with changes in surface pH, confirming the ability of the system to detect activity proportional to expression level.

The effects of buffers and pH on the thermal stability, unfolding and substrate binding of RecA.

PubMed

Metrick, Michael A; Temple, Joshua E; MacDonald, Gina

2013-12-31

The Escherichia coli protein RecA is responsible for catalysis of the strand transfer reaction used in DNA repair and recombination. Previous studies in our lab have shown that high concentrations of salts stabilize RecA in a reverse-anionic Hofmeister series. Here we investigate how changes in pH and buffer alter the thermal unfolding and cofactor binding. RecA in 20mM HEPES, MES, Tris and phosphate buffers was studied in the pH range from 6.5 to 8.5 using circular dichroism (CD), infrared (IR) and fluorescence spectroscopies. The results show all of the buffers studied stabilize RecA up to 50°C above the Tris melting temperature and influence RecA's ability to nucleate on double-stranded DNA. Infrared and CD spectra of RecA in the different buffers do not show that secondary structural changes are associated with increased stability or decreased ability to nucleate on dsDNA. These results suggest the differences in stability arise from decreasing positive charge and/or buffer interactions. © 2013. Published by Elsevier B.V. All rights reserved.

A Phytase Characterized by Relatively High pH Tolerance and Thermostability from the Shiitake Mushroom Lentinus edodes

PubMed Central

Zhang, Guo-Qing; Wu, Ying-Ying; Ng, Tzi-Bun; Chen, Qing-Jun; Wang, He-Xiang

2013-01-01

A monomeric phytase with a molecular mass of 14 kDa was acquired from fresh fruiting bodies of the shiitake mushroom Lentinus edodes. The isolation procedure involved chromatography on DEAE-cellulose, CM-cellulose, Q-Sepharose, Affi-gel blue gel, and a final fast protein liquid chromatography-gel filtration on Superdex 75. The purified phytase demonstrated the unique N-terminal amino acid sequence DPKRTDQVN, which exhibited no sequence similarity with those of other phytases previously reported. It expressed its maximal activity at pH 5.0 and 37°C. Phytase activity manifested less than 20% change in activity over the pH range of 3.0–9.0, considerable thermostability with more than 60% residual activity at 70°C, and about 40% residual activity at 95°C. It displayed a wide substrate specificity on a variety of phosphorylated compounds with the following ranking: ATP > fructose-6-phosphate > AMP > glucose-6-phosphate > ADP > sodium phytate > β-glycerophosphate. The phytase activity was moderately stimulated by Ca2+, but inhibited by Al3+, Mn2+, Zn2+, and Cu2+ at a tested concentration of 5 mM. PMID:23586045

Acetylcholinesterase and acetylcholine receptor. Final report, 1 April 1992-30 September 1995

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cohen, S.G.

1995-10-01

1 Bromo-214Cpinacolone (34CbrPin) inactivates AcChEs, from T. nobiliana labeling Cys 231, and E. electricus labeling His-440, and possibly Trp-435 and Asn-533. 14Cphenacyl bromide, (14CphABr) inactivates, labeling Cys-231 and His-550 in T. nobiliana, and His-550 in E. electricus. Five sequenced peptides in T. nobiliana, are identical with those from T. califomica. Four peptides from E. electricus show 77 - 96% homology. Inactivations by BrPin or PhABr exclude 3Hdfp; inactivation by DFP does not exclude 14CbrPin or 14CphABr. In studies with 14CbrPin, 5-trimethylammonio-2-pentanone was the preferred protecting agent; with 14CphABr, 3-trimethylammonioacetophenone was used with T. nobiliana, phenyltrimethylammonium ion with E. electricus. N-Methylacridiniummore » protects E. electricus against PhABr, but accelerates inactivation of T. nobiliana. Acetylcholine protects E. electricus against PhABr, indicating that His-550 marks the site at which the binding of high concentration of the substrate inhibits its own hydrolysis, possibly important in its action as a neurotransmitter. Photolysis of pivalophenone leading to benzoyl and tert-butyl radicals, inactivates the enzymes. Protection is offered by radical scavenging thiols.« less

Effects of Low Phytanic Acid-Concentrated DHA on Activated Microglial Cells: Comparison with a Standard Phytanic Acid-Concentrated DHA.

PubMed

Ruiz-Roso, María Belén; Olivares-Álvaro, Elena; Quintela, José Carlos; Ballesteros, Sandra; Espinosa-Parrilla, Juan F; Ruiz-Roso, Baltasar; Lahera, Vicente; de Las Heras, Natalia; Martín-Fernández, Beatriz

2018-05-30

Docosahexaenoic acid (DHA, 22:6 n-3) is an essential omega-3 (ω-3) long chain polyunsaturated fatty acid of neuronal membranes involved in normal growth, development, and function. DHA has been proposed to reduce deleterious effects in neurodegenerative processes. Even though, some inconsistencies in findings from clinical and pre-clinical studies with DHA could be attributed to the presence of phytanic acid (PhA) in standard DHA treatments. Thus, the aim of our study was to analyze and compare the effects of a low PhA-concentrated DHA with a standard PhA-concentrated DHA under different neurotoxic conditions in BV-2 activated microglial cells. To this end, mouse microglial BV-2 cells were stimulated with either lipopolysaccharide (LPS) or hydrogen peroxide (H 2 O 2 ) and co-incubated with DHA 50 ppm of PhA (DHA (PhA:50)) or DHA 500 ppm of PhA (DHA (PhA:500)). Cell viability, superoxide anion (O 2 - ) production, Interleukin 6 (L-6), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), glutathione peroxidase (GtPx), glutathione reductase (GtRd), Caspase-3, and the brain-derived neurotrophic factor (BDNF) protein expression were explored. Low PhA-concentrated DHA protected against LPS or H 2 O 2 -induced cell viability reduction in BV-2 activated cells and O 2 - production reduction compared to DHA (PhA:500). Low PhA-concentrated DHA also decreased COX-2, IL-6, iNOS, GtPx, GtRd, and SOD-1 protein expression when compared to DHA (PhA:500). Furthermore, low PhA-concentrated DHA increased BDNF protein expression in comparison to DHA (PhA:500). The study provides data supporting the beneficial effect of low PhA-concentrated DHA in neurotoxic injury when compared to a standard PhA-concentrated DHA in activated microglia.

Effects of acoustic wave resonance oscillation on immobilized enzyme

NASA Astrophysics Data System (ADS)

Nishiyama, Hiroshi; Watanabe, Tomoya; Inoue, Yasunobu

2014-03-01

In aiming at developing a new method to artificially activate enzyme catalysts immobilized on surface, the effects of resonance oscillation of bulk acoustic waves were studied. Glucose oxidase (GOD) was immobilized by a covalent coupling method on a ferroelectric lead zirconate titanate (PZT) device that was able to generate thickness-extensional resonance oscillation (TERO). Glucose oxidation by the GOD enzyme was studied in a microreactor. The generation of TERO immediately increased the catalytic activity of immobilized GOD by a factor of 2-3. With turn-off of TERO, no significant activity decrease occurred, and 80-90% of the enhanced activity was maintained while the reaction proceeded. The almost complete reversion of the activity to the original low level before TERO generation was observed when the immobilized GOD was exposed to a glucose substrate-free solution. These results indicated that the presence of glucose substrate was essential for TERO-induced GOD activation and preservation of the increased activity level. The influences of reaction temperature, glucose concentration, pH, and rf electric power on the TERO activation showed that TERO strengthened the interactions of the immobilized enzyme with glucose substrate and hence promoted the formation of an activation complex.

Hydrolytic pre-treatment methods for enhanced biobutanol production from agro-industrial wastes.

PubMed

Maiti, Sampa; Gallastegui, Gorka; Suresh, Gayatri; Sarma, Saurabh Jyoti; Brar, Satinder Kaur; Drogui, Patrick; LeBihan, Yann; Buelna, Gerardo; Verma, Mausam; Soccol, Carlos Ricardo

2018-02-01

Brewery industry liquid waste (BLW), brewery spent grain (BSG), apple pomace solid wastes (APS), apple pomace ultrafiltration sludge (APUS) and starch industry wastewater (SIW) have been considered as substrates to produce biobutanol. Efficiency of hydrolysis techniques tested to produce fermentable sugars depended on nature of agro-industrial wastes and process conditions. Acid-catalysed hydrolysis of BLW and BSG gave a total reducing sugar yield of 0.433 g/g and 0.468 g/g respectively. Reducing sugar yield from microwave assisted hydrothermal method was 0.404 g/g from APS and 0.631 g/g from APUS, and, 0.359 g/g from microwave assisted acid-catalysed SIW dry mass. Parameter optimization (time, pH and substrate concentration) for acid-catalysed BLW hydrolysate utilization using central composite model technique produced 307.9 g/kg glucose with generation of inhibitors (5-hydroxymethyl furfural (20 g/kg), furfural (1.6 g/kg), levulinic acid (9.3 g/kg) and total phenolic compound (0.567 g/kg)). 10.62 g/L of acetone-butanol-ethanol was produced by subsequent clostridial fermentation of the substrate. Copyright © 2017 Elsevier Ltd. All rights reserved.