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Sample records for acid degradation rate

  1. Decomposition of phenylarsonic acid by AOP processes: degradation rate constants and by-products.

    PubMed

    Jaworek, K; Czaplicka, M; Bratek, Ł

    2014-10-01

    The paper presents results of the studies photodegradation, photooxidation, and oxidation of phenylarsonic acid (PAA) in aquatic solution. The water solutions, which consist of 2.7 g dm(-3) phenylarsonic acid, were subjected to advance oxidation process (AOP) in UV, UV/H2O2, UV/O3, H2O2, and O3 systems under two pH conditions. Kinetic rate constants and half-life of phenylarsonic acid decomposition reaction are presented. The results from the study indicate that at pH 2 and 7, PAA degradation processes takes place in accordance with the pseudo first order kinetic reaction. The highest rate constants (10.45 × 10(-3) and 20.12 × 10(-3)) and degradation efficiencies at pH 2 and 7 were obtained at UV/O3 processes. In solution, after processes, benzene, phenol, acetophenone, o-hydroxybiphenyl, p-hydroxybiphenyl, benzoic acid, benzaldehyde, and biphenyl were identified.

  2. Effect of hydrion evolution by polylactic-co-glycolic acid coating on degradation rate of pure iron.

    PubMed

    Wu, Jingyao; Lu, Xi; Tan, Lili; Zhang, Bingchun; Yang, Ke

    2013-10-01

    For biodegradable iron coronary stents, the major problem is the low degradation rate in body environment. In this study, a new strategy was proposed to increase the degradation rate of iron in vitro. The hydrion evolution was intended to be introduced into the degradation system to increase the degradation rate. To realize this strategy, polylactic-co-glycolic acid (PLGA) was coated onto the surface of pure iron. The degradation process and mechanism of pure iron coated with PLGA were investigated. The results showed that iron coated with PLGA exhibited higher degradation rate in the static immersion test all along. With the degradation of PLGA, the oligomers of PLGA could release abundant H(+) which could dissolve the ferrous oxide to make the electrolyte and oxygen to reach the surface of iron again and simultaneity trigger the hydrion evolution at the middle stage of the degradation. The study also revealed that the solution ions failed to permeate the PLGA coating and the deposition of calcium and phosphorus in the degradation layer was inhibited which further enhanced the degradation.

  3. Rates of synthesis and degradation of ribosomal ribonucleic acid during differentiation of Dictyostelium discoideum.

    PubMed Central

    Mangiarotti, G; Altruda, F; Lodish, H F

    1981-01-01

    Synthesis of ribosomes and ribosomal ribonucleic acid (RNA) continued during differentiation of Dictyostelium discoideum concurrently with extensive turnover of ribosomes synthesized during both growth and developmental stages. We show here that the rate of synthesis of 26S and 17S ribosomal RNA during differentiation was less than 15% of that in growing cells, and by the time of sorocarp formation only about 25% of the cellular ribosomes had been synthesized during differentiation. Ribosomes synthesized during growth and differentiation were utilized in messenger RNA translation to the same extent; about 50% of each class were on polyribosomes. Ribosome degradation is apparently an all-or-nothing process, since virtually all 80S monosomes present in developing cells could be incorporated into polysomes when growth conditions were restored. By several criteria, ribosomes synthesized during growth and differentiation were functionally indistinguishable. Our data, together with previously published information on changes in the messenger RNA population during differentiation, indicate that synthesis of new ribosomes is not necessary for translation of developmentally regulated messenger RNA. We also establish that the overall rate of messenger RNA synthesis during differentiation is less than 15% of that in growing cells. PMID:6965093

  4. Rates of synthesis and degradation of ribosomal ribonucleic acid during differentiation of Dictyostelium discoideum.

    PubMed

    Mangiarotti, G; Altruda, F; Lodish, H F

    1981-01-01

    Synthesis of ribosomes and ribosomal ribonucleic acid (RNA) continued during differentiation of Dictyostelium discoideum concurrently with extensive turnover of ribosomes synthesized during both growth and developmental stages. We show here that the rate of synthesis of 26S and 17S ribosomal RNA during differentiation was less than 15% of that in growing cells, and by the time of sorocarp formation only about 25% of the cellular ribosomes had been synthesized during differentiation. Ribosomes synthesized during growth and differentiation were utilized in messenger RNA translation to the same extent; about 50% of each class were on polyribosomes. Ribosome degradation is apparently an all-or-nothing process, since virtually all 80S monosomes present in developing cells could be incorporated into polysomes when growth conditions were restored. By several criteria, ribosomes synthesized during growth and differentiation were functionally indistinguishable. Our data, together with previously published information on changes in the messenger RNA population during differentiation, indicate that synthesis of new ribosomes is not necessary for translation of developmentally regulated messenger RNA. We also establish that the overall rate of messenger RNA synthesis during differentiation is less than 15% of that in growing cells.

  5. Microbial naphthenic Acid degradation.

    PubMed

    Whitby, Corinne

    2010-01-01

    Naphthenic acids (NAs) are an important group of trace organic pollutants predominantly comprising saturated aliphatic and alicyclic carboxylic acids. NAs are ubiquitous; occurring naturally in hydrocarbon deposits (petroleum, oil sands, bitumen, and crude oils) and also have widespread industrial uses. Consequently, NAs can enter the environment from both natural and anthropogenic processes. NAs are highly toxic, recalcitrant compounds that persist in the environment for many years, and it is important to develop efficient bioremediation strategies to decrease both their abundance and toxicity in the environment. However, the diversity of microbial communities involved in NA-degradation, and the mechanisms by which NAs are biodegraded, are poorly understood. This lack of knowledge is mainly due to the difficulties in identifying and purifying individual carboxylic acid compounds from complex NA mixtures found in the environment, for microbial biodegradation studies. This paper will present an overview of NAs, their origin and fate in the environment, and their toxicity to the biota. The review describes the microbial degradation of both naturally occurring and chemically synthesized NAs. Proposed pathways for aerobic NA biodegradation, factors affecting NA biodegradation rates, and possible bioremediation strategies are also discussed.

  6. Compendium of photovoltaic degradation rates: Photovoltaic degradation rates

    SciTech Connect

    Jordan, Dirk C.; Kurtz, Sarah R.; VanSant, Kaitlyn; Newmiller, Jeff

    2016-02-07

    Published data on photovoltaic (PV) degradation measurements were aggregated and re-examined. The subject has seen an increased interest in recent years resulting in more than 11 000 degradation rates in almost 200 studies from 40 different countries. As studies have grown in number and size, we found an impact from sampling bias attributable to size and accuracy. Because of the correlational nature of this study we examined the data in several ways to minimize this bias. We found median degradation for x-Si technologies in the 0.5-0.6%/year range with the mean in the 0.8-0.9%/year range. Hetero-interface technology (HIT) and microcrystalline silicon (..mu..c-Si) technologies, although not as plentiful, exhibit degradation around 1%/year and resemble thin-film products more closely than x-Si. Several studies showing low degradation for copper indium gallium selenide (CIGS) have emerged. Higher degradation for cadmium telluride (CdTe) has been reported, but these findings could reflect a convolution of less accurate studies and longer stabilization periods for some products. Significant deviations for beginning-of-life measurements with respect to nameplate rating have been documented over the last 35 years. Therefore, degradation rates that use nameplate rating as reference may be significantly impacted. Studies that used nameplate rating as reference but used solar simulators showed less variation than similar studies using outdoor measurements, even when accounting for different climates. This could be associated with confounding effects of measurement uncertainty and soiling that take place outdoors. Hotter climates and mounting configurations that lead to sustained higher temperatures may lead to higher degradation in some, but not all, products. Wear-out non-linearities for the worst performing modules have been documented in a few select studies that took multiple measurements of an ensemble of modules during the lifetime of the system. However, the majority

  7. Tuning the degradation rate of calcium phosphate cements by incorporating mixtures of polylactic-co-glycolic acid microspheres and glucono-delta-lactone microparticles.

    PubMed

    Sariibrahimoglu, Kemal; An, Jie; van Oirschot, Bart A J A; Nijhuis, Arnold W G; Eman, Rhandy M; Alblas, Jacqueline; Wolke, Joop G C; van den Beucken, Jeroen J J P; Leeuwenburgh, Sander C G; Jansen, John A

    2014-11-01

    Calcium phosphate cements (CPCs) are frequently used as synthetic bone graft materials in view of their excellent osteocompatibility and clinical handling behavior. Hydroxyapatite-forming CPCs, however, degrade at very low rates, thereby limiting complete bone regeneration. The current study has investigated whether degradation of apatite-forming cements can be tuned by incorporating acid-producing slow-resorbing poly(D,L-lactic-co-glycolic) acid (PLGA) porogens, fast-resorbing glucono-delta-lactone (GDL) porogens, or mixtures thereof. The physicochemical, mechanical, and degradation characteristics of these CPC formulations were systematically analyzed upon soaking in phosphate-buffered saline (PBS). In parallel, various CPC formulations were implanted intramuscularly and orthotopically on top of the transverse process of goats followed by analysis of the soft tissue response and bone ingrowth after 12 weeks. In vitro degradation of GDL was almost completed after 2 weeks, as evidenced by characterization of the release of gluconic acid, while PLGA-containing CPCs released glycolic acid throughout the entire study (12 weeks), resulting in a decrease in compression strength of CPC. Extensive in vitro degradation of the CPC matrix was observed upon simultaneous incorporation of 30% PLGA-10% GDL. Histomorphometrical evaluation of the intramuscularly implanted samples revealed that all CPCs exhibited degradation, accompanied by an increase in capsule thickness. In the in vivo goat transverse process model, incorporation of 43% PLGA, 30% PLGA-5% GDL, and 30% PLGA-10% GDL in CPC significantly increased bone formation and resulted in higher bone height compared with both 10% GDL and 20% GDL-containing CPC samples.

  8. Applying Stable Isotope Labeled Amino Acids in Micropatterned Hepatocyte Co-Culture to Directly Determine the Degradation Rate Constant for CYP3A4.

    PubMed

    Takahashi, Ryan H; Shahidi-Latham, Sheerin; Wong, Susan; Chang, Jae H

    2017-03-13

    The rate of enzyme degradation (kdeg) is an important input parameter for the prediction of clinical drug-drug-interactions (DDI) that result from mechanism-based inactivation or induction of cytochrome P450s. Currently, a large range of reported estimates for CYP3A4 enzyme degradation exists, and consequently, large uncertainty exists in steady-state predictions for DDI. In the current investigations, stable isotope labeled amino acids in culture (SILAC) was applied to a long-lived primary human hepatocyte culture, HepatoPac, to directly monitor the degradation of CYP3A4. This approach allowed selective isotope labeling of a population of de novo synthesized CYP3A4, and specific quantification of proteins with mass spectrometry to determine the CYP3A4 degradation within the hepatocytes. The kdeg estimate was 0.026 ± 0.005 h- 1. This value was reproduced by cultures derived across four individual donors. For these cultures, data indicated that CYP3A4 mRNA and total protein expression (i.e. labeled and not labeled P450s), and activity were stable over the period where degradation had been determined. This kdeg value for CYP3A4 was in good agreement with recently reported values that used alternate analytical approaches, but also employed micropatterned primary human hepatocytes as the in vitro model.

  9. Photovoltaic Degradation Rates -- An Analytical Review

    SciTech Connect

    Jordan, D. C.; Kurtz, S. R.

    2012-06-01

    As photovoltaic penetration of the power grid increases, accurate predictions of return on investment require accurate prediction of decreased power output over time. Degradation rates must be known in order to predict power delivery. This article reviews degradation rates of flat-plate terrestrial modules and systems reported in published literature from field testing throughout the last 40 years. Nearly 2000 degradation rates, measured on individual modules or entire systems, have been assembled from the literature, showing a median value of 0.5%/year. The review consists of three parts: a brief historical outline, an analytical summary of degradation rates, and a detailed bibliography partitioned by technology.

  10. Uncertainty Analysis for Photovoltaic Degradation Rates (Poster)

    SciTech Connect

    Jordan, D.; Kurtz, S.; Hansen, C.

    2014-04-01

    Dependable and predictable energy production is the key to the long-term success of the PV industry. PV systems show over the lifetime of their exposure a gradual decline that depends on many different factors such as module technology, module type, mounting configuration, climate etc. When degradation rates are determined from continuous data the statistical uncertainty is easily calculated from the regression coefficients. However, total uncertainty that includes measurement uncertainty and instrumentation drift is far more difficult to determine. A Monte Carlo simulation approach was chosen to investigate a comprehensive uncertainty analysis. The most important effect for degradation rates is to avoid instrumentation that changes over time in the field. For instance, a drifting irradiance sensor, which can be achieved through regular calibration, can lead to a substantially erroneous degradation rates. However, the accuracy of the irradiance sensor has negligible impact on degradation rate uncertainty emphasizing that precision (relative accuracy) is more important than absolute accuracy.

  11. Aqueous thermal degradation of gallic acid

    SciTech Connect

    Boles, J.S.; Crerar, D.A.; Grissom, G.; Key, T.C.

    1988-02-01

    Aqueous thermal degradation experiments show gallic acid, a naturally occurring aromatic carboxylic compound, decomposes rapidly at temperatures between 105/sup 0/ and 150/sup 0/C, with an activation energy of 22.9 or 27.8 kcal/mole, depending on pH of the starting solution. Pyrogallol is the primary product identified, indicating degradation via decarboxylation and a carbanion transition state. Relatively rapid degradation of vanillic, phthalic, ellagic and tannic acids has also been observed,suggesting that these and perhaps other aromatic acids could be short-lived in deep formation waters.

  12. Aqueous thermal degradation of gallic acid

    NASA Astrophysics Data System (ADS)

    Snow Boles, Jennifer; Crerar, David A.; Grissom, Grady; Key, Tonalee C.

    1988-02-01

    Aqueous thermal degradation experiments show gallic acid, a naturally occurring aromatic carboxylic compound, decomposes rapidly at temperatures between 105° and 150°C, with an activation energy of 22.9 or 27.8 kcal/ mole, depending on pH of the starting solution. Pyrogallol is the primary product identified, indicating degradation via decarboxylation and a carbanion transition state. Relatively rapid degradation of vanillic, phthalic, ellagic and tannic acids has also been observed, suggesting that these and perhaps other aromatic acids could be short-lived in deep formation waters.

  13. Protein Degradation Rate in Arabidopsis thaliana Leaf Growth and Development.

    PubMed

    Li, Lei; Nelson, Clark J; Trösch, Josua; Castleden, Ian; Huang, Shaobai; Millar, A Harvey

    2017-02-01

    We applied (15)N labeling approaches to leaves of the Arabidopsis thaliana rosette to characterize their protein degradation rate and understand its determinants. The progressive labeling of new peptides with (15)N and measuring the decrease in the abundance of >60,000 existing peptides over time allowed us to define the degradation rate of 1228 proteins in vivo. We show that Arabidopsis protein half-lives vary from several hours to several months based on the exponential constant of the decay rate for each protein. This rate was calculated from the relative isotope abundance of each peptide and the fold change in protein abundance during growth. Protein complex membership and specific protein domains were found to be strong predictors of degradation rate, while N-end amino acid, hydrophobicity, or aggregation propensity of proteins were not. We discovered rapidly degrading subunits in a variety of protein complexes in plastids and identified the set of plant proteins whose degradation rate changed in different leaves of the rosette and correlated with leaf growth rate. From this information, we have calculated the protein turnover energy costs in different leaves and their key determinants within the proteome.

  14. Overview of Field Experience - Degradation Rates & Lifetimes

    SciTech Connect

    Jordan, Dirk; Kurtz, Sarah

    2015-09-14

    The way a PV module fails may depend not only on its design and the materials used in its construction, but also on the weather it experiences, the way it is mounted, and the quality control during its manufacture. This presentation gives an overview of Field Experience - what degradation rates and what lifetimes are being observed in various regions.

  15. Glycolic acid modulates the mechanical property and degradation of poly(glycerol, sebacate, glycolic acid).

    PubMed

    Sun, Zhi-Jie; Wu, Lan; Huang, Wei; Chen, Chang; Chen, Yan; Lu, Xi-Li; Zhang, Xiao-Lan; Yang, Bao-Feng; Dong, De-Li

    2010-01-01

    The development of biodegradable materials with controllable degradation properties is beneficial for a variety of applications. Poly(glycerol-sebacate) (PGS) is a promising candidate of biomaterials; so we synthesize a series of poly(glycerol, sebacate, glycolic acid) (PGSG) with 1:2:0, 1:2:0.2, 1:2:0.4, 1:2:0.6, 1:2:1 mole ratio of glycerol, sebacate, and glycolic acid to elucidate the relation of doped glycolic acid to the degradation rate and mechanical properties. The microstructures of the polymers with different doping of glycolic acid were dissimilar. PGSG with glycolic acid in the ratio of 0.2 displayed an integral degree of ordering, different to those with glycolic acid in the ratio of 0, 0.4, 0.6, and 1, which showed mild phase separation structure. The number, DeltaH(m), and temperature of the PGSG melting peaks tended to decrease with the increasing ratio of doped glycolic acid. In vitro and in vivo degradation tests showed that the degradation rate of PGSG with glycolic acid in the ratio of 0.2 was slowest, but in the ratio range of 0, 0.4, and 0.6, the degradation rate increased with the increase of glycolic acid. All PGSG samples displayed good tissue response and anticoagulant effects. Our data suggest that doping glycolic acid can modulate the microstructure and degree of crosslinking of PGS, thereby control the degradation rate of PGS.

  16. Acid and base degraded products of ketorolac.

    PubMed

    Salaris, Margherita; Nieddu, Maria; Rubattu, Nicola; Testa, Cecilia; Luongo, Elvira; Rimoli, Maria Grazia; Boatto, Gianpiero

    2010-06-05

    The stability of ketorolac tromethamine was investigated in acid (0.5M HCl) and alkaline conditions (0.5M NaOH), using the same procedure reported by Devarajan et al. [2]. The acid and base degradation products were identified by liquid chromatography-mass spectrometry (LC-MS).

  17. Degradation and compatibility behaviors of poly(glycolic acid) grafted chitosan.

    PubMed

    Zhang, Luzhong; Dou, Sufeng; Li, Yan; Yuan, Ying; Ji, Yawei; Wang, Yaling; Yang, Yumin

    2013-07-01

    The films of poly(glycolic acid) grafted chitosan were prepared without using a catalyst to improve the degradable property of chitosan. The films were characterized by Fourier transform-infrared spectroscopy and X-ray photoelectron spectroscopy (XPS). The degradation of the poly(glycolic acid) grafted chitosan films were investigated in the lysozyme solution. In vitro degradation tests revealed that the degradation rate of poly(glycolic acid) grafted chitosan films increased dramatically compared with chitosan. The degradation rate of poly(glycolic acid) grafted chitosan films gradually increased with the increasing of the molar ratio of glycolic acid to chitosan. Additionally, the poly(glycolic acid) grafted chitosan films have good biocompatibility, as demonstrated by in vitro cytotoxicity of the extraction fluids. The biocompatible and biodegradable poly(glycolic acid) grafted chitosan would be an effective material with controllable degradation rate to meet the diverse needs in biomedical fields.

  18. Water and UV degradable lactic acid polymers

    DOEpatents

    Bonsignore, P.V.; Coleman, R.D.

    1996-10-08

    A water and UV light degradable copolymer is described made from monomers of lactic acid and a modifying monomer selected from the class consisting of ethylene glycol, propylene glycol, P-dioxanone, 1,5 dioxepan-2-one, 1,4-oxathialan-2-one, 1,4-dioxide and mixtures thereof. These copolymers are useful for waste disposal and agricultural purposes. Also disclosed is a water degradable blend of polylactic acid or modified polylactic acid and high molecular weight polyethylene oxide wherein the high molecular weight polyethylene oxide is present in the range of from about 2 by weight to about 50% by weight, suitable for films. A method of applying an active material selected from the class of seeds, seedlings, pesticides, herbicides, fertilizers and mixtures thereof to an agricultural site is also disclosed.

  19. Water and UV degradable lactic acid polymers

    DOEpatents

    Bonsignore, Patrick V.; Coleman, Robert D.

    1996-01-01

    A water and UV light degradable copolymer of monomers of lactic acid and a modifying monomer selected from the class consisting of ethylene glycol, propylene glycol, P-dioxanone, 1,5 dioxepan-2-one, 1,4-oxathialan-2-one, 1,4-dioxide and mixtures thereof. These copolymers are useful for waste disposal and agricultural purposes. Also disclosed is a water degradable blend of polylactic acid or modified polylactic acid and high molecular weight polyethylene oxide wherein the high molecular weight polyethylene oxide is present in the range of from about 2 by weight to about 50% by weight, suitable for films. A method of applying an active material selected from the class of seeds, seedlings, pesticides, herbicides, fertilizers and mixtures thereof to an agricultural site is also disclosed.

  20. Water and UV degradable lactic acid polymers

    DOEpatents

    Bonsignore, Patrick V.; Coleman, Robert D.

    1994-01-01

    A water and UV light degradable copolymer of monomers of lactic acid and a modifying monomer selected from the class consisting of ethylene and polyethylene glycols, propylene and polypropylene glycols, P-dioxanone, 1,5 dioxepan-2-one, 1,4 -oxathialan-2-one, 1,4-dioxide and mixtures thereof. These copolymers are useful for waste disposal and agricultural purposes. Also disclosed is a water degradable blend of polylactic acid or modified polylactic acid and high molecular weight polyethylene oxide wherein the high molecular weight polyethylene oxide is present in the range of from about 2% by weight to about 50% by weight, suitable for films. A method of applying an active material selected from the class of seeds, seedlings, pesticides, herbicides, fertilizers and mixtures thereof to an agricultural site is also disclosed.

  1. Water and UV degradable lactic acid polymers

    DOEpatents

    Bonsignore, P.V.; Coleman, R.D.

    1994-11-01

    A water and UV light degradable copolymer of monomers of lactic acid and a modifying monomer were selected from the class consisting of ethylene and polyethylene glycols, propylene and polypropylene glycols, P-dioxanone, 1,5 dioxepan-2-one, 1,4 -oxathialan-2-one, 1,4-dioxide and mixtures. These copolymers are useful for waste disposal and agricultural purposes. Also disclosed is a water degradable blend of polylactic acid or modified polylactic acid and high molecular weight polyethylene oxide where the high molecular weight polyethylene oxide is present in the range of from about 2% by weight to about 50% by weight, suitable for films. A method of applying an active material selected from the class of seeds, seedlings, pesticides, herbicides, fertilizers and mixtures to an agricultural site is also disclosed.

  2. Water and UV degradable lactic acid polymers

    SciTech Connect

    Bonsignore, P.V.; Coleman, R.D.

    1990-06-26

    A water and UV light degradable copolymer of monomers of lactic acid and a modifying monomer selected from the class consisting of ethylene and polyethylane glycols (PVB 6/22/90), propylene and and polypropylene (PVB 6/22/90) glycols, P-dioxanone, 1, 5 dioxepan-2-one, 1,4 -oxathialan-2-one, 1,4-dioxide and mixtures thereof. These copolymers are useful for waste disposal and agricultural purposes. Also disclosed is a water degradable blend of polylactic acid or modified polylactic acid and high molecular weight polyethylene oxide wherein the high molecular weight polyethylene oxide is present in the range of from about 2% by weight to about 50% by weight, suitable for films. A method of applying an active material selected from the class of seeds, seedlings, pesticides, herbicides, fertilizers and mixtures thereof to an agricultural site is also disclosed.

  3. Anaerobic degradation of linoleic oleic acids

    SciTech Connect

    Lalman, J.A.; Bagley, D.M.

    1999-07-01

    The anaerobic degradation of linoleic (C18:2) and oleic (C18:1) acids was examined in batch experiments. By-product distribution depended on both the type of long chain fatty acid added and initial substrate concentration. Major by-products were palmitic (C16), myristic (C14) and acetic acids. Trace quantities of palmitoleic (C16:1) and lauric (C12) acids were observed together with larger amounts of palmitic (C16), myristic (C14) and hexanoic (C6) acids in cultures incubated with 100 mg/L linoleic (C18:2) acid. Bio-hydrogenation of C18 fatty acids was not necessary for the {beta}-oxidation mechanism to proceed. Aceticlastic methanogenic inhibition was observed in cultures inoculated with greater than 50 mg/L linoleic (C18:2) acid. In cultures incubated with greater than 50 mg/L oleic (C18:1) acid, aceticlastic methanogenic inhibition was observed for a short time period.

  4. Microbial degradation of poly(amino acid)s.

    PubMed

    Obst, Martin; Steinbüchel, Alexander

    2004-01-01

    Natural poly(amino acid)s are a group of poly(ionic) molecules (ionomers) with various biological functions and putative technical applications and play, therefore, an important role both in nature and in human life. Because of their biocompatibility and their synthesis from renewable resources, poly(amino acid)s may be employed for many different purposes covering a broad spectrum of medical, pharmaceutical, and personal care applications as well as the domains of agriculture and of environmental applications. Biodegradability is one important advantage of naturally occurring poly(amino acid)s over many synthetic polymers. The intention of this review is to give an overview about the enzyme systems catalyzing the initial steps in poly(amino acid) degradation. The focus is on the naturally occurring poly(amino acid)s cyanophycin, poly(epsilon-L-lysine) and poly(gamma-glutamic acid); but biodegradation of structurally related synthetic polyamides such as poly(aspartic acid) and nylons, which are known from various technical applications, is also included.

  5. Aerobic Microbial Degradation of Glucoisosaccharinic Acid

    PubMed Central

    Strand, S. E.; Dykes, J.; Chiang, V.

    1984-01-01

    α-Glucoisosaccharinic acid (GISA), a major by-product of kraft paper manufacture, was synthesized from lactose and used as the carbon source for microbial media. Ten strains of aerobic bacteria capable of growth on GISA were isolated from kraft pulp mill environments. The highest growth yields were obtained with Ancylobacter spp. at pH 7.2 to 9.5. GISA was completely degraded by cultures of an Ancylobacter isolate. Ancylobacter cell suspensions consumed oxygen and produced carbon dioxide in response to GISA addition. A total of 22 laboratory strains of bacteria were tested, and none was capable of growth on GISA. GISA-degrading isolates were not found in forest soils. Images PMID:16346467

  6. [Catalytic ozonation by ceramic honeycomb for the degradation of oxalic acid in aqueous solution].

    PubMed

    Zhao, Lei; Sun, Zhi-Zhong; Ma, Jun

    2007-11-01

    Comparative experiments for the degradation of oxalic acid in aqueous solution were carried out in the three processes of ozonation alone, ceramic honeycomb-catalyzed ozonation and ceramic honeycomb adsorption. The results show that the degradation rates of oxalic acid in the ceramic honeycomb-catalyzed ozonation, ozonation alone and ceramic honeycomb adsorption systems are 37.6%, 2.2% and 0.4%, and the presence of ceramic honeycomb catalyst significantly improves the degradation rate of oxalic acid compared to the results from non-catalytic ozonation and adsorption. With the addition of tert-butanol, the degradation rates of oxalic acid in catalytic ozonation system decrease by 24.1%, 29.0% and 30.1%, respectively, at the concentration of 5, 10 and 15 mg x L(-1). This phenomenon indicates that ceramic honeycomb-catalyzed ozonation for the degradation of oxalic acid in aqueous solution follows the mechanism of *OH oxidation, namely the heterogeneous surface of catalyst enhances the initiation of *OH. The results of TOC analysis demonstrate that the process of ceramic honeycomb-catalyzed ozonation can achieve the complete mineralization level without the formation of intermediary degradation products. The experimental results suggest that the reaction temperature has positive relationship with the degradation rate of oxalic acid. The degradation rates of oxalic acid in the ceramic honeycomb-catalyzed ozonation system are 16.4%, 37.6%, 61.3% and 68.2%, at the respective reaction temperature of 10, 20, 30 and 40 degrees C.

  7. Degradation of organic acids by dairy lactic acid bacteria.

    PubMed

    Hegazi, F Z; Abo-Elnaga, I G

    1980-01-01

    One hundred and twelve different strains of lactic acid bacteria, belonging to the genera Leuconostoc, Streptococcus, and Lactobacillus, were examined for the ability to degrade 10 organic acids by detecting gas production, using the conventional Durham tube method. All the strains did not break down succinate, glutarate, 2-oxo-glutarate, and mucate. Malate, citrate, pyruvate, fumarate, tartrate, and gluconate were variably attacked. Streptococcus cremoiris AM2, ML8, and SK11 required glucose to produce gas from citrate, whereas Leuconostoc citrovorum and Streptococcus faecalis did not. Streptococcus cremoris differed from the other streptococci in not producing gas from gluconate. From all lactic acid bacteria examined, only Lactobacillus plantarum formed gas from tartarate. Determination of acetoin and diacetyl proved to be a more reliable evidence for assessing the degradation of pyruvate, compared with detection of gas production. Homofermentative lactobacilli and Leuconostoc citrovorum produced acetoin and diacetyl from pyruvate, whereas beta-bacteria did not, a character that would be of taxonomic value. Streptobacteria degraded pyruvate in the presence of glucose with lactate as the major product together with a mean acetate of 4.1%, ethanol 7.9%, acetoin 1.7%, and diacetyl 2.6% yield on a molar basis after 60 days at 30 degrees C. L. brevis produced acetate and lactate. Formation of diacetyl from pyruvate by lactic acid bacteria may play an important role in flavour development in fermenting dairy products, especially in cheese, where lactic acid bacteria usually predominate, and pyruvate is probably excreted in the breaking down of lactose and in the oxidative deamination of alanine by the accompanying microflora.

  8. Effect of scrubbing operating conditions on adipic acid degradation. Final report February-August 1980

    SciTech Connect

    Chang, J.C.S.

    1981-02-01

    The report gives results of adipic acid degradation tests at EPA's IERL-RTP limestone SO2 scrubber, to investigate the effects of operating variables on unaccountable adipic acid loss. It was found that: (1) adipic acid degradation could not be totally quenched by only lowering the pH below 5.0; (2) pH change did significantly affect unaccountable adipic acid loss (other factors may increase the adipic acid degradation rate at both high and low pH); (3) an appreciable amount of adipic acid loss was caused by coprecipitation with calcium sulfite; and (4) forced oxidation could aggravate the adipic acid degradation loss even at pH below 5.0. Adipic acid loss could be reduced: at high sulfite concentrations (the adipic acid degradation rate could be decreased by lowering the destructive free radical concentrations by high total sulfite); in the presence of manganous ion at low pH (the metal ion might act as an inhibitor to the oxidative degradation reaction at low pH); and with high natural oxidation (the adipic acid coprecipitation loss might be reduced with the high natural oxidation). Adipic acid degradation (loss) data were compared from four different test facilities. Most of the data also support these conclusions.

  9. Bioenergetics and pathway of acid blue 113 degradation by Staphylococcus lentus.

    PubMed

    Sekar, Sudharshan; Mahadevan, Surianarayanan; Shanmugam, Bhuvanesh Kumar; Mandal, Asit Baran

    2012-01-01

    Bioreaction calorimetric studies of degradation of the dye acid blue 113 by Staphylococcus lentus are reported for the first time. The heat released during the dye degradation process can be successfully measured using reaction calorimeter. Power time and oxygen uptake rate (OUR) profile followed each other suggesting that heat profiles could monitor the progress of the dye degradation in biocalorimetry. The shifts observed in power-time profile indicated three distinct phases of the bioprocess indicating simultaneous utilization of glucose (primary) and dye (secondary carbon source). Secretion of azoreductase enzyme enhanced the degradation process. Optimization of aeration and agitation rates was observed to be vital to efficient dye degradation. The degradative pathway for acid blue 113 by S. lentus was delineated via high-performance liquid chromatography (HPLC), Fourier transform infrared spectroscopy (FT-IR), and gas chromatography coupled with mass spectrometry (GC-MS) analyses. Interestingly the products of degradation were found to have low toxicity, as per cytotoxicity measurements.

  10. Degradation and Isotope Source Tracking of Glyphosate and Aminomethylphosphonic Acid.

    PubMed

    Li, Hui; Joshi, Sunendra R; Jaisi, Deb P

    2016-01-27

    Glyphosate [N-(phosphonomethyl) glycine], an active ingredient of the herbicide Roundup, and its main metabolite, aminomethylphosphonic acid (AMPA), have been frequently reported to be present in soils and other environments and thus have heightened public concerns on their potential adverse effects. Understanding the fate of these compounds and differentiating them from other naturally occurring compounds require a toolbox of methods that can go beyond conventional methods. Here, we applied individual isotope labeling technique whereby each compound or mineral involved in the glyphosate and AMPA degradation reaction was either synthesized or chosen to have distinct (18)O/(16)O ratios so that the source of incorporated oxygen in the orthophosphate generated and corresponding isotope effect during C-P bond cleavage could be identified. Furthermore, we measured original isotope signatures of a few commercial glyphosate sources to identify their source-specific isotope signatures. Our degradation kinetics results showed that the rate of glyphosate degradation was higher than that of AMPA in all experimental conditions, and both the rate and extent of degradation were lowest under anoxic conditions. Oxygen isotope ratios (δ(18)OP) of orthophosphate generated from glyphosate and AMPA degradation suggested that one external oxygen atom from ambient water, not from dissolved oxygen or mineral, was incorporated into orthophosphate with the other three oxygen atoms inherited from the parent molecule. Interestingly, δ(18)OP values of all commercial glyphosate products studied were found to be the lightest among all orthophosphates known so far. Furthermore, isotope composition was found to be unaffected due to variable degradation kinetics, light/dark, and oxic/anoxic conditions. These results highlight the importance of phosphate oxygen isotope ratios as a nonconventional tool to potentially distinguish glyphosate sources and products from other organophosphorus compounds

  11. Prostatic acid phosphatase degrades lysophosphatidic acid in seminal plasma.

    PubMed

    Tanaka, Masayuki; Kishi, Yasuhiro; Takanezawa, Yasukazu; Kakehi, Yoshiyuki; Aoki, Junken; Arai, Hiroyuki

    2004-07-30

    Lysophosphatidic acid (LPA) is a lipid mediator with multiple biological activities and is detected in various biological fluids, including human seminal plasma. Due to its cell proliferation stimulatory and anti-apoptotic activities, LPA has been implicated in the progression of some cancers such as ovarian cancer and prostate cancer. Here, we show that prostatic acid phosphatase, which is a non-specific phosphatase and which has been implicated in the progression of prostate cancer, inactivates LPA in human seminal plasma. Human seminal plasma contains both an LPA-synthetic enzyme, lysoPLD, which converts lysophospholipids to LPA and is responsible for LPA production in serum, and its major substrate, lysophosphatidylcholine. In serum, LPA accumulated during incubation at 37 degrees C. However, in seminal plasma, LPA did not accumulate. This discrepancy is explained by the presence of a strong LPA-degrading activity. Incubation of LPA with seminal plasma resulted in the disappearance of LPA and an accompanying accumulation of monoglyceride showing that LPA is degraded by phosphatase activity present in the seminal plasma. When seminal plasma was incubated in the presence of a phosphatase inhibitor, sodium orthovanadate, LPA accumulated, indicating that LPA is produced and degraded in the fluid. Biochemical characterization of the LPA-phosphatase activity identified two phosphatase activities in human seminal plasma. By Western blotting analysis in combination with several column chromatographies, the major activity was revealed to be identical to prostatic acid phosphatase. The present study demonstrates active LPA metabolism in seminal plasma and indicates the possible role of LPA signaling in male sexual organs including prostate cancer.

  12. Effect of trace metals and sulfite oxidation of adipic acid degradation in FGD systems. Final report Dec 81-May 82

    SciTech Connect

    Jarvis, J.B.; Terry, J.C.; Schubert, S.A.; Utley, B.L.

    1982-12-01

    The report gives results of the measurement of the adipic acid degradation rate in a bench-scale flue gas desulfurization (FGD) system, designed to simulate many of the important aspects of full-scale FGD systems. Results show that the adipic acid degradation rate depends on the sulfite oxidation rate, the adipic acid concentration, the presence of manganese in solution, and temperature. The degradation rate is also affected by pH, but only when manganese is present. Adipic acid degradation products identified in the liquid phase include valeric, butyric, propionic, succinic, and glutaric acids. When manganese was present, the predominant degradation products were succinic and glutaric acids. Analysis of solids from the bench scale tests shows large concentrations of coprecipitated adipic acid in low oxidation sulfite solids. By contrast, low quantities of coprecipitated adipic acid were found in high oxidation gypsum solids.

  13. Evaluation of non-thermal effects of electricity on ascorbic acid and carotenoid degradation in acerola pulp during ohmic heating.

    PubMed

    Jaeschke, Débora Pez; Marczak, Ligia Damasceno Ferreira; Mercali, Giovana Domeneghini

    2016-05-15

    The effect of electric field on ascorbic acid and carotenoid degradation in acerola pulp during ohmic heating was evaluated. Ascorbic acid kinetic degradation was evaluated at 80, 85, 90 and 95°C during 60 min of thermal treatment by ohmic and conventional heating. Carotenoid degradation was evaluated at 90 and 95°C after 50 min of treatment. The different temperatures evaluated showed the same effect on degradation rates. To investigate the influence of oxygen concentration on the degradation process, ohmic heating was also carried out under rich and poor oxygen modified atmospheres at 90°C. Ascorbic acid and carotenoid degradation was higher under a rich oxygen atmosphere, indicating that oxygen is the limiting reagent of the degradation reaction. Ascorbic acid and carotenoid degradation was similar for both heating technologies, demonstrating that the presence of the oscillating electric field did not influence the mechanisms and rates of reactions associated with the degradation process.

  14. The abiotic degradation of soil organic matter to oxalic acid

    NASA Astrophysics Data System (ADS)

    Studenroth, Sabine; Huber, Stefan; Schöler, H. F.

    2010-05-01

    degradation of catechol to oxalic acid delivers a maximum yield of approximately 60 %, whereas the presence of chloride reduces the formation of oxalic acid to 30 %. Chloride possibly induces further competing reactions of catechol leading to a lower concentration of oxalic acid. Freeze-dried soil samples have been tested for production of oxalic acid, where the rate of organic matter seems to play an important role for the formation. By adding iron (III) and/or hydrogen peroxide oxalic acid yields increase, which demonstrates the reaction of soil organic matter with iron (III) and hydrogen peroxide as expected. Thus the natural abiotic formation of oxalic acid is confirmed. The results of the soil measurements are similar to those obtained with catechol. Therefore, the newly gained insights with model compounds appear to be applicable to soil conditions and these findings increase our understanding of the degradation pathways of soil organic matter. Furthermore an overview of the rates of oxalic acid formation of a variety of soil samples is shown and discussed in the light of different soil parameter.

  15. Degradation of 3-phenoxybenzoic acid by a Bacillus sp.

    PubMed

    Chen, Shaohua; Hu, Wei; Xiao, Ying; Deng, Yinyue; Jia, Jianwen; Hu, Meiying

    2012-01-01

    3-Phenoxybenzoic acid (3-PBA) is of great environmental concern with regards to endocrine disrupting activity and widespread occurrence in water and soil, yet little is known about microbial degradation in contaminated regions. We report here that a new bacterial strain isolated from soil, designated DG-02, was shown to degrade 95.6% of 50 mg·L(-1) 3-PBA within 72 h in mineral salt medium (MSM). Strain DG-02 was identified as Bacillus sp. based on the morphology, physio-biochemical tests and 16S rRNA sequence. The optimum conditions for 3-PBA degradation were determined to be 30.9°C and pH 7.7 using response surface methodology (RSM). The isolate converted 3-PBA to produce 3-(2-methoxyphenoxy) benzoic acid, protocatechuate, phenol, and 3,4-dihydroxy phenol, and subsequently transformed these compounds with a q(max), K(s) and K(i) of 0.8615 h(-1), 626.7842 mg·L(-1) and 6.7586 mg·L(-1), respectively. A novel microbial metabolic pathway for 3-PBA was proposed on the basis of these metabolites. Inoculation of strain DG-02 resulted in a higher degradation rate on 3-PBA than that observed in the non-inoculated soil. Moreover, the degradation process followed the first-order kinetics, and the half-life (t(1/2)) for 3-PBA was greatly reduced as compared to the non-inoculated control. This study highlights an important potential application of strain DG-02 for the in situ bioremediation of 3-PBA contaminated environments.

  16. Radiation-induced degradation of cyclohexanebutyric acid in aqueous solutions by gamma ray irradiation

    NASA Astrophysics Data System (ADS)

    Jia, Wenbao; He, Yanquan; Ling, Yongsheng; Hei, Daqian; Shan, Qing; Zhang, Yan; Li, Jiatong

    2015-04-01

    The radiation-induced degradation of cyclohexanebutyric acid under gamma ray irradiation was investigated. Degradation experiments were performed with 100 mL sealed Pyrex glass vessels loaded with 80 mL of cyclohexanebutyric acid solutions at various initial concentrations of 10, 20, and 40 mg L-1. The absorbed doses were controlled at 0, 0.65, 1.95, 3.25, 6.5, 9.75, and 13 kGy. The results showed that gamma ray irradiation could effectively degrade cyclohexanebutyric acid in aqueous solutions. The removal rate of cyclohexanebutyric acid increased significantly with the increase of absorbed dose and the decrease of its initial concentration. At the same time, the removal of chemical oxygen demand (COD) was as effective as that of cyclohexanebutyric acid. The kinetic studies showed that the degradation of cyclohexanebutyric acid followed pseudo first-order reaction. Above all, the proposed mechanism obtained when NaNO2, NaNO3 and tert-butanol were added showed that the •OH radical played a major role in the gamma degradation process of cyclohexanebutyric acid, while •H and eaq- played a minor role in the gamma degradation process. The degradation products were identified by Fourier transform infrared spectroscopy (FTIR) and gas chromatography/mass spectrometry (GC/MS) during cyclohexanebutyric acid degradation.

  17. SENSITIVITY ANALYSIS OF A TPB DEGRADATION RATE MODEL

    SciTech Connect

    Crawford, C; Tommy Edwards, T; Bill Wilmarth, B

    2006-08-01

    A tetraphenylborate (TPB) degradation model for use in aggregating Tank 48 material in Tank 50 is developed in this report. The influential factors for this model are listed as the headings in the table below. A sensitivity study of the predictions of the model over intervals of values for the influential factors affecting the model was conducted. These intervals bound the levels of these factors expected during Tank 50 aggregations. The results from the sensitivity analysis were used to identify settings for the influential factors that yielded the largest predicted TPB degradation rate. Thus, these factor settings are considered as those that yield the ''worst-case'' scenario for TPB degradation rate for Tank 50 aggregation, and, as such they would define the test conditions that should be studied in a waste qualification program whose dual purpose would be the investigation of the introduction of Tank 48 material for aggregation in Tank 50 and the bounding of TPB degradation rates for such aggregations.

  18. Rate-based degradation modeling of lithium-ion cells

    SciTech Connect

    E.V. Thomas; I. Bloom; J.P. Christophersen; V.S. Battaglia

    2012-05-01

    Accelerated degradation testing is commonly used as the basis to characterize battery cell performance over a range of stress conditions (e.g., temperatures). Performance is measured by some response that is assumed to be related to the state of health of the cell (e.g., discharge resistance). Often, the ultimate goal of such testing is to predict cell life at some reference stress condition, where cell life is defined to be the point in time where performance has degraded to some critical level. These predictions are based on a degradation model that expresses the expected performance level versus the time and conditions under which a cell has been aged. Usually, the degradation model relates the accumulated degradation to the time at a constant stress level. The purpose of this article is to present an alternative framework for constructing a degradation model that focuses on the degradation rate rather than the accumulated degradation. One benefit of this alternative approach is that prediction of cell life is greatly facilitated in situations where the temperature exposure is not isothermal. This alternative modeling framework is illustrated via a family of rate-based models and experimental data acquired during calendar-life testing of high-power lithium-ion cells.

  19. Fatty Acid Structure and Degradation Analysis in Fingerprint Residues.

    PubMed

    Pleik, Stefanie; Spengler, Bernhard; Schäfer, Thomas; Urbach, Dieter; Luhn, Steven; Kirsch, Dieter

    2016-09-01

    GC-MS investigations were carried out to elucidate the aging behavior of unsaturated fatty acids in fingerprint residues and to identify their degradation products in aged samples. For this purpose, a new sample preparation technique for fingerprint residues was developed that allows producing N-methyl-N-trimethylsilyl-trifluoroacetamide (MSTFA) derivatives of the analyzed unsaturated fatty acids and their degradation products. MSTFA derivatization catalyzed by iodotrimethylsilane enables the reliable identification of aldehydes and oxoacids as characteristic MSTFA derivatives in GCMS. The obtained results elucidate the degradation pathway of unsaturated fatty acids. Our study of aged fingerprint residues reveals that decanal is the main degradation product of the observed unsaturated fatty acids. Furthermore, oxoacids with different chain lengths are detected as specific degradation products of the unsaturated fatty acids. The detection of the degradation products and their chain length is a simple and effective method to determine the double bond position in unsaturated compounds. We can show that the hexadecenoic and octadecenoic acids found in fingerprint residues are not the pervasive fatty acids Δ9-hexadecenoic (palmitoleic acid) and Δ9-octadecenoic (oleic acid) acid but Δ6-hexadecenoic acid (sapienic acid) and Δ8-octadecenoic acid. The present study focuses on the structure identification of human sebum-specific unsaturated fatty acids in fingerprint residues based on the identification of their degradation products. These results are discussed for further investigations and method developments for age determination of fingerprints, which is still a tremendous challenge because of several factors affecting the aging behavior of individual compounds in fingerprints. Graphical Abstract ᅟ.

  20. Fatty Acid Structure and Degradation Analysis in Fingerprint Residues

    NASA Astrophysics Data System (ADS)

    Pleik, Stefanie; Spengler, Bernhard; Schäfer, Thomas; Urbach, Dieter; Luhn, Steven; Kirsch, Dieter

    2016-09-01

    GC-MS investigations were carried out to elucidate the aging behavior of unsaturated fatty acids in fingerprint residues and to identify their degradation products in aged samples. For this purpose, a new sample preparation technique for fingerprint residues was developed that allows producing N-methyl- N-trimethylsilyl-trifluoroacetamide (MSTFA) derivatives of the analyzed unsaturated fatty acids and their degradation products. MSTFA derivatization catalyzed by iodotrimethylsilane enables the reliable identification of aldehydes and oxoacids as characteristic MSTFA derivatives in GCMS. The obtained results elucidate the degradation pathway of unsaturated fatty acids. Our study of aged fingerprint residues reveals that decanal is the main degradation product of the observed unsaturated fatty acids. Furthermore, oxoacids with different chain lengths are detected as specific degradation products of the unsaturated fatty acids. The detection of the degradation products and their chain length is a simple and effective method to determine the double bond position in unsaturated compounds. We can show that the hexadecenoic and octadecenoic acids found in fingerprint residues are not the pervasive fatty acids Δ9-hexadecenoic (palmitoleic acid) and Δ9-octadecenoic (oleic acid) acid but Δ6-hexadecenoic acid (sapienic acid) and Δ8-octadecenoic acid. The present study focuses on the structure identification of human sebum-specific unsaturated fatty acids in fingerprint residues based on the identification of their degradation products. These results are discussed for further investigations and method developments for age determination of fingerprints, which is still a tremendous challenge because of several factors affecting the aging behavior of individual compounds in fingerprints.

  1. Oxidative degradation of organic acids conjugated with sulfite oxidation in flue gas desulfurization

    SciTech Connect

    Lee, Y.I.

    1986-01-01

    Organic acid degradation conjugated with sulfite oxidation has been studied under flue gas desulfurization (EGD) conditions. The oxidative degradation constant, k/sub 12/, is defined as the ratio of organic acid degradation rate and sulfite oxidation rate after being normalized by the concentrations of organic acid and dissolved S(IV). K/sub 12/, not significantly affected by pH or dissolved oxygen, is around 10/sup -3/ in the absence of manganese or iron. However, k/sub 12/ is increased by certain transition metals such as Co, Ni, and Fe and is decreased by Mn and halides. Lower dissolved S(IV) magnified these effects. No k/sub 12/ greater than 4 x 10/sup -3/ or smaller than 0.1 x 10/sup -3/ has been observed. A free radical mechanism was proposed to describe the kinetics: (1) sulfate free radical is the major radical responsible to the degradation of organic acid; (2) ferrous generates sulfate radical by reacting with monoxypersulfate to enhance k/sub 12/; (3) manganous consumes sulfate radical to decrease k/sub 12/; (4) dissolved S(IV) competes with ferrous for monoxypersulfate and with manganous for sulfate radical to demonstrate the effects of dissolved S(IV) on k/sub 12/. Hydroxy and sulfonated carboxylic acids degrade approximately three times slower than saturated dicarboxylic acids; while maleic acid, an unsaturated dicarboxylic acid, degraded an order of magnitude faster. A wide spectrum of degradation products of adipic acid were found, including carbon dioxide - the major product, glutaric semialdehyde - the major retained product with low manganese, glutaric acid and valeric acids - the major retained product with high manganese, lower molecular weight mono- and dicarboxylic acids, other carbonyl compounds, and hydrocarbons.

  2. Accelerating degradation rate of pure iron by zinc ion implantation

    PubMed Central

    Huang, Tao; Zheng, Yufeng; Han, Yong

    2016-01-01

    Pure iron has been considered as a promising candidate for biodegradable implant applications. However, a faster degradation rate of pure iron is needed to meet the clinical requirement. In this work, metal vapor vacuum arc technology was adopted to implant zinc ions into the surface of pure iron. Results showed that the implantation depth of zinc ions was about 60 nm. The degradation rate of pure iron was found to be accelerated after zinc ion implantation. The cytotoxicity tests revealed that the implanted zinc ions brought a slight increase on cytotoxicity of the tested cells. In terms of hemocompatibility, the hemolysis of zinc ion implanted pure iron was lower than 2%. However, zinc ions might induce more adhered and activated platelets on the surface of pure iron. Overall, zinc ion implantation can be a feasible way to accelerate the degradation rate of pure iron for biodegradable applications. PMID:27482462

  3. Accelerating degradation rate of pure iron by zinc ion implantation.

    PubMed

    Huang, Tao; Zheng, Yufeng; Han, Yong

    2016-12-01

    Pure iron has been considered as a promising candidate for biodegradable implant applications. However, a faster degradation rate of pure iron is needed to meet the clinical requirement. In this work, metal vapor vacuum arc technology was adopted to implant zinc ions into the surface of pure iron. Results showed that the implantation depth of zinc ions was about 60 nm. The degradation rate of pure iron was found to be accelerated after zinc ion implantation. The cytotoxicity tests revealed that the implanted zinc ions brought a slight increase on cytotoxicity of the tested cells. In terms of hemocompatibility, the hemolysis of zinc ion implanted pure iron was lower than 2%. However, zinc ions might induce more adhered and activated platelets on the surface of pure iron. Overall, zinc ion implantation can be a feasible way to accelerate the degradation rate of pure iron for biodegradable applications.

  4. Degradation of hop bitter acids by fungi.

    PubMed

    Huszcza, Ewa; Bartmańska, Agnieszka; Anioł, Mirosław; Maczka, Wanda; Zołnierczyk, Anna; Wawrzeńczyk, Czesław

    2008-01-01

    Nine fungal strains related to: Trametes versicolor, Nigrospora oryzae, Inonotus radiatus, Crumenulopsis sororia, Coryneum betulinum, Cryptosporiopsis radicicola, Fusarium equiseti, Rhodotorula glutinis and Candida parapsilosis were tested for their ability to degrade humulones and lupulones. The best results were obtained for T. versicolor culture, in which humulones and lupulones were fully degraded after 4days of incubation in the dark or after 36h in the light. The experiments were performed on a commercial hop extract and on sterilized spent hops.

  5. Acid catalysed degradation of some spiramycin derivatives found in the antibiotic bitespiramycin.

    PubMed

    Shi, Xiangguo; Zhang, Shuqiu; Fawcett, J Paul; Zhong, Dafang

    2004-11-15

    Bitespiramycin is a novel antibiotic containing a number of 4''-acylated spiramycin derivatives (isovalerylspiramycins I-III, butanoylspiramycin III, propanoylspiramycin III and acetylspiramycin III) as major components. These spiramycin derivatives are susceptible to degradation in acid solution. Liquid chromatography-ion trap mass spectrometry (LC/MS(n)) was used to study the degradation of these spiramycin derivatives in simulated gastric fluid at 37 degrees C. All derivatives degraded by first-order reactions for which rate constants (k) and half-lives (t(1/2)) were calculated. Acyl groups at position 3 had less effect on acid-stability of spiramycin derivatives than acyl groups at position 4''. The introduction of 4''-acyl groups enhanced the acid-stability of spiramycin derivatives and altered the degradation pathway in simulated gastric fluid such that loss of forosamine rather than loss of mycarose becomes the major degradation pathway.

  6. Aerobic degradation of sulfanilic acid using activated sludge.

    PubMed

    Chen, Gang; Cheng, Ka Yu; Ginige, Maneesha P; Kaksonen, Anna H

    2012-01-01

    This paper evaluates the aerobic degradation of sulfanilic acid (SA) by an acclimatized activated sludge. The sludge was enriched for over three months with SA (>500 mg/L) as the sole carbon and energy source and dissolved oxygen (DO, >5mg/L) as the primary electron acceptor. Effects of aeration rate (0-1.74 L/min), DO concentration (0-7 mg/L) and initial SA concentration (104-1085 mg/L) on SA biodegradation were quantified. A modified Haldane substrate inhibition model was used to obtain kinetic parameters of SA biodegradation and oxygen uptake rate (OUR). Positive linear correlations were obtained between OUR and SA degradation rate (R(2)≥ 0.91). Over time, the culture consumed more oxygen per SA degraded, signifying a gradual improvement in SA mineralization (mass ratio of O(2): SA at day 30, 60 and 120 were 0.44, 0.51 and 0.78, respectively). The concomitant release of near stoichiometric quantity of sulphate (3.2 mmol SO(4)(2-) released from 3.3 mmol SA) and the high chemical oxygen demand (COD) removal efficacy (97.1%) indicated that the enriched microbial consortia could drive the overall SA oxidation close to a complete mineralization. In contrast to other pure-culture systems, the ammonium released from the SA oxidation was predominately converted into nitrate, revealing the presence of ammonium-oxidizing bacteria (AOB) in the mixed culture. No apparent inhibitory effect of SA on the nitrification was noted. This work also indicates that aerobic SA biodegradation could be monitored by real-time DO measurement.

  7. Protein Degradation Rate in Arabidopsis thaliana Leaf Growth and Development[OPEN

    PubMed Central

    Nelson, Clark J.; Castleden, Ian

    2017-01-01

    We applied 15N labeling approaches to leaves of the Arabidopsis thaliana rosette to characterize their protein degradation rate and understand its determinants. The progressive labeling of new peptides with 15N and measuring the decrease in the abundance of >60,000 existing peptides over time allowed us to define the degradation rate of 1228 proteins in vivo. We show that Arabidopsis protein half-lives vary from several hours to several months based on the exponential constant of the decay rate for each protein. This rate was calculated from the relative isotope abundance of each peptide and the fold change in protein abundance during growth. Protein complex membership and specific protein domains were found to be strong predictors of degradation rate, while N-end amino acid, hydrophobicity, or aggregation propensity of proteins were not. We discovered rapidly degrading subunits in a variety of protein complexes in plastids and identified the set of plant proteins whose degradation rate changed in different leaves of the rosette and correlated with leaf growth rate. From this information, we have calculated the protein turnover energy costs in different leaves and their key determinants within the proteome. PMID:28138016

  8. Acid attack on hydrated cement — Effect of mineral acids on the degradation process

    SciTech Connect

    Gutberlet, T.; Hilbig, H.; Beddoe, R.E.

    2015-08-15

    During acid attack on concrete structural components, a degraded layer develops whose properties as a protective barrier are decisive for durability. {sup 29}Si NMR spectroscopy and {sup 27}Al NMR spectroscopy were used with XRD to investigate the degraded layer on hardened cement paste exposed to HCl and H{sub 2}SO{sub 4}. The layer comprises an amorphous silica gel with framework silicates, geminate and single silanol groups in which Si is substituted by Al. Amorphous Al(OH){sub 3} and Fe(OH){sub 3} are present. The gel forms by polycondensation and cross-linking of C-A-S-H chains at AlO{sub 4} bridging tetrahedra. In the transition zone between the degraded layer and the undamaged material, portlandite dissolves and Ca is removed from the C-A-S-H phases maintaining their polymer structure at first. With HCl, monosulphate in the transition zone is converted into Friedel's salt and ettringite. With H{sub 2}SO{sub 4}, gypsum precipitates near the degradation front reducing the thickness of the transition zone and the rate of degradation.

  9. EVALUATING DEGRADATION RATES OF CHLORINATED ORGANICS IN GROUNDWATER USING ANALYTICAL MODELS

    EPA Science Inventory

    The persistence and fate of organic contaminants in the environment largely depends on their rate of degradation. Most studies of degradation rate are performed in the lab where chemical conditions can be controlled precisely. Unfortunately, literature values for lab degradation ...

  10. Amino Acid Degradation after Meteoritic Impact Simulation

    NASA Technical Reports Server (NTRS)

    Bertrand, M.; Westall, F.; vanderGaast, S.; Vilas, F.; Hoerz, F.; Barnes, G.; Chabin, A.; Brack, A.

    2008-01-01

    Amino acids are among the most important prebiotic molecules as it is from these precursors that the building blocks of life were formed [1]. Although organic molecules were among the components of the planetesimals making up the terrestrial planets, large amounts of primitive organic precursor molecules are believed to be exogenous in origin and to have been imported to the Earth via micrometeorites, carbonaceous meteorites and comets, especially during the early stages of the formation of the Solar System [1,2]. Our study concerns the hypothesis that prebiotic organic matter, present on Earth, was synthesized in the interstellar environment, and then imported to Earth by meteorites or micrometeorites. We are particularly concerned with the formation and fate of amino acids. We have already shown that amino acid synthesis is possible inside cometary grains under interstellar environment conditions [3]. We are now interested in the effects of space conditions and meteoritic impact on these amino acids [4-6]. Most of the extraterrestrial organic molecules known today have been identified in carbonaceous chondrite meteorites [7]. One of the components of these meteorites is a clay with a composition close to that of saponite, used in our experiments. Two American teams have studied the effects of impact on various amino acids [8,9]. [8] investigated amino acids in saturated solution in water with pressure ranges between 5.1 and 21 GPa and temperature ranges between 412 and 870 K. [9] studied amino acids in solid form associated with and without minerals (Murchison and Allende meteorite extracts) and pressure ranges between 3 and 30 GPa. In these two experiments, the amino acids survived up to 15 GPa. At higher pressure, the quantity of preserved amino acids decreases quickly. Some secondary products such as dipeptides and diketopiperazins were identified in the [8] experiment.

  11. Eigen model with general fitness functions and degradation rates

    NASA Astrophysics Data System (ADS)

    Hu, Chin-Kun; Saakian, David B.

    2006-03-01

    We present an exact solution of Eigen's quasispecies model with a general degradation rate and fitness functions, including a square root decrease of fitness with increasing Hamming distance from the wild type. The found behavior of the model with a degradation rate is analogous to a viral quasi-species under attack by the immune system of the host. Our exact solutions also revise the known results of neutral networks in quasispecies theory. To explain the existence of mutants with large Hamming distances from the wild type, we propose three different modifications of the Eigen model: mutation landscape, multiple adjacent mutations, and frequency-dependent fitness in which the steady state solution shows a multi-center behavior.

  12. [Degradation of Acid Orange 7 with Persulfate Activated by Silver Loaded Granular Activated Carbon].

    PubMed

    Wang, Zhong-ming; Huang, Tian-yin; Chen, Jia-bin; Li, Wen-wei; Zhang, Li-ming

    2015-11-01

    Granular activated carbon with silver loaded as activator (Ag/GAC) was prepared using impregnation method. N2 adsorption, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) were adopted to characterize the Ag/GAC, showing that silver was successfully loaded on granular activated carbon. The oxidation degradation of acid orange 7 (AO7) by the Ag/GAC activated by persulfate (PS) was investigated at ambient temperature. The influences of factors such as Ag loading, PS or Ag/GAC dosages and initial pH on the degradation of AO7 were evaluated. The results demonstrated that the degradation rate of AO7 could reach more than 95.0% after 180 min when the Ag loading content, PS/AO7 molar ratio, the Ag/GAC dosage were 12.7 mg x g(-1), 120: 1, 1.0 g x L(-1), respectively. The initial pH had significant effect on the AO7 degradation, with pH 5.0 as the optimal pH for the degradation of AO7. The possible degradation pathway was proposed for the AO7 degradation by using UV-visible spectroscopy and gas chromatography-mass spectrometry (GG/MS). The azo bond and naphthalene ring in the AO7 were destroyed during the degradation, with phthalic acid and acetophenone as the main degradation products.

  13. Bacterial degradation of m-nitrobenzoic acid.

    PubMed Central

    Nadeau, L J; Spain, J C

    1995-01-01

    Pseudomonas sp. strain JS51 grows on m-nitrobenzoate (m-NBA) with stoichiometric release of nitrite. m-NBA-grown cells oxidized m-NBA and protocatechuate but not 3-hydroxybenzoate, 4-hydroxy-3-nitrobenzoate, 4-nitrocatechol, and 1,2,4-benzenetriol. Protocatechuate accumulated transiently when succinate-grown cells were transferred to media containing m-NBA. Respirometric experiments indicated that the conversion of m-NBA to protocatechuate required 1 mol of oxygen per mol of substrate. Conversions conducted in the presence of 18O2 showed the incorporation of both atoms of molecular oxygen into protocatechuate. Extracts of m-NBA-grown cells cleaved protocatechuate to 2-hydroxy-4-carboxymuconic semialdehyde. These results provide rigorous proof that m-NBA is initially oxidized by a dioxygenase to produce protocatechuate which is further degraded by a 4,5-dioxygenase. PMID:7574625

  14. Chemical Degradation Studies on a Series of Dithiophosphinic Acids

    SciTech Connect

    Melissa E. Freiderich; Dean R. Peterman; John R. Klaehn; Philippe Marc; Laetitia H. Delmau

    2014-04-01

    A significant increase in the stability of a series of dithiophosphinic acids (DPAHs) under oxidizing acidic conditions was achieved. The degradation behavior of a series of DPAHs, designed for lanthanide/actinide separation, was examined. The stability of the DPAHs, when contacted with varying nitric acid concentrations, was tested and monitored using 31P {1H} NMR. Changes in the functional groups of the DPAHs resulted in substantial increases in the stability. However, when placed in contact with 2 M HNO3 all the DPAHs eventually showed signs of degradation. The addition of a radical scavenger, hydrazine, inhibited the degradation of the DPAHs. In the presence of a small concentration of hydrazine, five of the DPAHs remained stable for over a month in direct contact with 2 M HNO3.

  15. Degradation by acetic acid for crystalline Si photovoltaic modules

    NASA Astrophysics Data System (ADS)

    Masuda, Atsushi; Uchiyama, Naomi; Hara, Yukiko

    2015-04-01

    The degradation of crystalline Si photovoltaic modules during damp-heat test was studied using some test modules with and without polymer film insertion by observing electrical and electroluminescence properties and by chemical analyses. Acetic acid generated by the hydrolysis decomposition of ethylene vinyl acetate used as an encapsulant is the main origin of degradation. The change in electroluminescence images is explained on the basis of the corrosion of electrodes by acetic acid. On the other hand, little change was observed at the pn junction even after damp-heat test for a long time. Therefore, carrier generation occurs even after degradation; however, such generated carriers cannot be collected owing to corrosion of electrodes. The guiding principle that module structure and module materials without saving acetic acid into the modules was obtained.

  16. Chemical Degradation Studies on a Series of Dithiophosphinic Acids

    SciTech Connect

    Freiderich, Melissa E; Delmau, Laetitia Helene; Peterman, D. R.; Marc, Philippe L; Klaehn, John D.

    2014-01-01

    In this study a significant increase in the stability of a series of dithiophosphinic acids (DPAHs) under oxidizing acidic conditions was achieved. The degradation behavior of a series of DPAHs, designed for lanthanide/actinide separation, was examined. The stability of the DPAHs, when contacted with varying nitric acid concentrations, was tested and monitored using 31P {1H} NMR. Changes in the functional groups of the DPAHs resulted in substantial increases in the stability. However, all the DPAHs eventually showed signs of degradation when placed in contact with 2 M HNO3. The addition of a radical scavenger, hydrazine, inhibited the degradation of the DPAHs. With small amounts of hydrazine, five of the DPAHs remained stable for over a month in direct contact with 2 M HNO3.

  17. Microbial Degradation of Chlorogenic Acid by a Sphingomonas sp. Strain.

    PubMed

    Ma, Yuping; Wang, Xiaoyu; Nie, Xueling; Zhang, Zhan; Yang, Zongcan; Nie, Cong; Tang, Hongzhi

    2016-08-01

    In order to elucidate the metabolism of chlorogenic acid by environmental microbes, a strain of Sphingomonas sp. isolated from tobacco leaves was cultured under various conditions, and chlorogenic acid degradation and its metabolites were investigated. The strain converting chlorogenic acid was newly isolated and identified as a Sphingomonas sp. strain by 16S rRNA sequencing. The optimal conditions for growth and chlorogenic acid degradation were 37 °C and pH 7.0 with supplementation of 1.5 g/l (NH4)2SO4 as the nitrogen source and 2 g/l chlorogenic acid as the sole carbon source. The maximum chlorogenic acid tolerating capability for the strain was 5 g/l. The main metabolites were identified as caffeic acid, shikimic acid, and 3,4-dihydroxybenzoic acid based on gas chromatography-mass spectrometry analysis. The analysis reveals the biotransformation mechanism of chlorogenic acid in microbial cells isolated from the environment.

  18. A study on degradation kinetics of ascorbic acid in amla (Phyllanthus emblica L.) during cooking.

    PubMed

    Nisha, P; Singhal, Rekha S; Pandit, Aniruddha B

    2004-08-01

    The kinetics of ascorbic acid degradation in amla (Phyllanthus emblica L.) as well as in pure ascorbic acid solutions at initial concentrations present in amla over a temperature range of 50-120 degrees C (steady-state temperature) has been studied. The ascorbic acid degradation followed first-order reaction kinetics where the rate constant increased with an increase in temperature. The temperature dependence of degradation was adequately modeled by the Arrhenius equation. The activation energies were found to be 4.09 kcal/mole for amla and 4.49 kcal/mole for pure vitamin solution. The degradation kinetics of ascorbic acid was also evaluated in normal open pan cooking, pressure-cooking and a newly developed and patented fuel-efficient EcoCooker (unsteady state heating process). A mathematical model was developed using the steady-state kinetic parameters obtained to predict the losses of ascorbic acid from the time-temperature data of the unsteady state heating processing method. The results obtained indicate the ascorbic acid degradation is of a similar order of magnitude in all the methods of cooking.

  19. Microbial degradation of usnic acid in the reindeer rumen

    NASA Astrophysics Data System (ADS)

    Sundset, Monica A.; Barboza, Perry S.; Green, Thomas K.; Folkow, Lars P.; Blix, Arnoldus Schytte; Mathiesen, Svein D.

    2010-03-01

    Reindeer ( Rangifer tarandus) eat and utilize lichens as an important source of energy and nutrients in winter. Lichens synthesize and accumulate a wide variety of phenolic secondary compounds, such as usnic acid, as a defense against herbivores and to protect against damage by UV-light in solar radiation. We have examined where and to what extent these phenolic compounds are degraded in the digestive tract of the reindeer, with particular focus on usnic acid. Three male reindeer were given ad libitum access to a control diet containing no usnic acid for three weeks and then fed lichens ad libitum (primarily Cladonia stellaris) containing 9.1 mg/g DM usnic acid for 4 weeks. Usnic acid intake in reindeer on the lichen diet was 91-117 mg/kg BM/day. In spite of this, no trace of usnic acid or conjugates of usnic acid was found either in fresh rumen fluid, urine, or feces. This suggests that usnic acid is rapidly degraded by rumen microbes, and that it consequently is not absorbed by the animal. This apparent ability to detoxify lichen phenolic compounds may gain increased importance with future enhanced UV-B radiation expected to cause increased protective usnic acid/phenol production in lichens.

  20. Thermal degradation kinetics of sucrose palmitate reinforced poly(lactic acid) biocomposites.

    PubMed

    Valapa, Ravibabu; Pugazhenthi, Gopal; Katiyar, Vimal

    2014-04-01

    The current work is focused on investigating the influence of novel bio-filler, "sucrose palmitate (SP)" on the thermal degradation behavior of poly(lactic acid) (PLA) biocomposites in order to render its suitability for food packaging application. Thermal degradation behavior of the PLA biocomposites was investigated by thermo-gravimetric analysis (TGA) using dynamic heating regime. The differential TG analysis revealed that there is no change in the Tmax value (357 °C) for PLA and its composites up to 5 wt% of bio-filler loading. This reveals that the sucrose palmitate acts as a protective barrier by decelerating the thermal degradation rate of PLA. In the case of 10 wt% of the filler incorporated in the PLA matrix, Tmax rapidly shifted to lower temperature (324 °C). This downturn in Tmax at higher loading of the filler is due to the increase in acidic sites and enhancement in the rate of degradation is observed. Differential scanning calorimetry (DSC) analysis revealed unimodal melting peak indicating the α-crystalline form of PLA. Based on the thermal degradation profile of sucrose palmitate, possible mechanism for degradation of PLA composites is proposed. The activation energies (Ea) of thermal degradation of PLA and PLA composites were evaluated by Flynn-Wall-Ozawa and Kissinger methods.

  1. Varying Conditions for Hexanoic Acid Degradation with BioTiger™

    SciTech Connect

    Foreman, Koji; Milliken, Charles; Brigmon, Robin

    2016-07-27

    BioTiger™ (BT) is a consortium of 12 bacteria designed for petroleum waste biodegradation. BT is currently being studied and could be considered for bioremediation of the Athabasca oil sands refineries in Canada and elsewhere. The run-off ponds from the petroleum extraction processes, called tailings ponds, are a mixture of polycyclic aromatic hydrocarbons, naphthenic acids, hydrocarbons, toxic chemicals like heavy metals, water, and sand. Due to environmental regulations the oil industry would like to separate and degrade the hazardous chemical species from the tailings ponds while recycling the water. It has been shown that BT at 30 C° is able to completely degrade 10 mM hexanoic acid (HA) co-metabolically with 0.2% yeast extract (w/v) in 48 hours when starting at 0.4 OD 600nm. After establishing this stable degradation capability, variations were tested to explore the wider parameters of BT activity in temperature, pH, intermediate degradation, co-metabolic dependence, and transfer stability. Due to the vast differences in temperature at various points in the refineries, a wide range of temperatures were assessed. The results indicate that BT retains the ability to degrade HA, a model surrogate for tailings pond contaminants, at temperatures ranging from 15°C to 35°C. Hexanamide (HAM) was shown to be an intermediate generated during the degradation of HA in an earlier work and HAM is completely degraded after 48 hours, indicating that HAM is not the final product of HA degradation. Various replacements for yeast extract were attempted. Glucose, a carbon source; casein amino acids, a protein source; additional ammonia, mimicking known media; and additional phosphate with Wolffe’s vitamins and minerals all showed no significant degradation of HA compared to control. Decreasing the yeast extract concentration (0.05%) demonstrated limited but significant degradation. Finally, serial inoculations of BT were performed to determine the stability of degradation

  2. Regulation of protein degradation pathways by amino acids and insulin in skeletal muscle of neonatal pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The rapid gain in lean mass in neonates requires greater rates of protein synthesis than degradation. We previously delineated the molecular mechanisms by which insulin and amino acids, especially leucine, modulate skeletal muscle protein synthesis and how this changes with development. In the curre...

  3. Heterogeneous photocatalytic degradation of gallic acid under different experimental conditions.

    PubMed

    Quici, Natalia; Litter, Marta I

    2009-07-01

    UV/TiO(2)-heterogeneous photocatalysis was tested as a process to degrade gallic acid (Gal) in oxygenated solutions at pH 3. In the absence of oxidants other than oxygen, decay followed a zero order rate at different concentrations and was slow at concentrations higher than 0.5 mM. Addition of Fe(3+), H(2)O(2) and the combination Fe(3+)/H(2)O(2) improved Gal degradation. In the absence of H(2)O(2), an optimal Fe : Gal molar ratio of 0.33 : 1 was found for the photocatalytic decay, beyond which addition of Fe(3+) was detrimental and even worse in comparison with the system in the absence of Fe(3+). TiO(2) addition was beneficial compared with the same system in the absence of the photocatalyst if Fe(3+) was added at low concentration (0.33 : 1 Fe : Gal molar ratio), while at high concentration (1 : 1 Fe : Gal molar ratio) TiO(2) did not exert any significant effect. H(2)O(2) addition (1 : 0.33 Gal : H(2)O(2) molar ratio, absence of Fe(iii)) also enhanced the heterogeneous photocatalytic reaction. Simultaneous addition of Fe(3+) and H(2)O(2) was more effective than the addition of the separate oxidants. This system was compared with Fenton and photo-Fenton systems. At low H(2)O(2) concentration (0.33 : 1 : 0.2 Fe : Gal : H(2)O(2) molar ratio), the presence of TiO(2) also enhanced the reaction. The influence of the thermal charge transfer reaction between Gal and Fe(iii), which leads to an important Gal depletion in the dark with formation of quinones, was analysed. The mechanisms taking place in these complex systems are proposed, paying particular attention to the important charge transfer reaction of the Fe(iii)-Gal complex operative in dark conditions.

  4. Oxidative degradation of organic acids conjugated with sulfite oxidation in flue-gas desulfurization. Final report, June 1984-June 1986

    SciTech Connect

    Lee, Y.J.; Rochelle, G.T.

    1988-02-01

    This report gives results of a study of organic acid-degradation conjugated with sulfite oxidation under flue-gas desulfurization (FGD) conditions. The oxidative degradation constant, k12, is defined as the ratio of organic-acid degradation rate and sulfite oxidation-rate times the ratio of the concentrations of dissolved S(IV) and organic acid. It is not significantly affected by pH or dissolved oxygen in the absence of Mn or Fe. However, k12 is increased by certain transition metals such as Fe, Co, and Ni and is decreased by Mn and halides. Lower dissolved S(IV) magnifies these effects. A free-radical mechanism was proposed to describe the kinetics. Hydroxy and sulfonated carboxylic acids degrade approximately three times slower than saturated dicarboxylic acids; while maleic acid, an unsaturated dicarboxylic acid, degraded an order of magnitude faster. A wide spectrum of degradation products of adipic acid were found, including carbon dioxide (the major product), smaller dicarboxylic acids, monocarboxylic acids, other carbonyl compounds, and hydrocarbons.

  5. Oxidative degradation of organic acid conjugated with sulfite oxidation in flue gas desulfurization: products, kinetics and mechanism

    SciTech Connect

    Lee, Y.J.; Rochelle, G.T.

    1987-03-01

    Organic acid degradation conjugated with sulfite oxidation has been studied under flue gas desulfurization (FGD) conditions. The oxidative degradation constant k/sub 12/ is defined as the ratio of organic acid degradation rate and sulfite oxidation rate times the ratio of the concentration of dissolved S(IV) and organic acid. It is not significantly affected by pH or dissolved oxygen in the absence of manganese or iron. However, k/sub 12/ is increased by certain transition metals such as Fe, Co, and Ni and is decreased by Mn and halides. Lower dissolved S(IV) magnifies these effects. A free radical mechanism was proposed to describe the kinetics. Hydroxy and sulfonated carboxylic acids degrade approximately 3 times slower than saturated dicarboxylic acids, while maleic acid, an unsaturated dicarboxylic acid, degraded an order of magnitude factor. A wide spectrum of degradation products of adipic acid were found, including carbon dioxide - the major product - smaller dicarboxylic acids, monocarboxylic acids, other carbonyl compounds, and hydrocarbons. 30 references, 7 figures, 7 tables.

  6. Pinocytosis and intracellular degradation of exogenous protein: modulation by amino acids

    PubMed Central

    1983-01-01

    Intracellular degradation of exogenous (serum) proteins provides a source of amino acids for cellular protein synthesis. Pinocytosis serves as the mechanism for delivering exogenous protein to the lysosomes, the major site of intracellular degradation of exogenous protein. To determine whether the availability of extracellular free amino acids altered pinocytic function, we incubated monolayers of pulmonary alveolar macrophages with the fluid-phase marker, [14C]sucrose, and we dissected the pinocytic process by kinetic analysis. Additionally, intracellular degradation of endogenous and exogenous protein was monitored by measuring phenylalanine released from the cell monolayers in the presence of cycloheximide. Results revealed that in response to a subphysiological level of essential amino acids or to amino acid deprivation, (a) the rate of fluid-phase pinocytosis increased in such a manner as to preferentially increase both delivery to and size of an intracellular compartment believed to be the lysosomes, (b) the degradation of exogenously supplied albumin increased, and (c) the fraction of phenylalanine derived from degradation of exogenous albumin and reutilized for de novo protein synthesis increased. Thus, modulation of the pinosome-lysosome pathway may represent a homeostatic mechanism sensitive to the availability of extracellular free amino acids. PMID:6853596

  7. Heterogeneous photocatalytic degradation of p-toluenesulfonic acid using concentrated solar radiation in slurry photoreactor.

    PubMed

    Kamble, Sanjay P; Sawant, Sudhir B; Pangarkar, Vishwas G

    2007-02-09

    In this work, the photocatalytic degradation (PCD) of p-toluenesulfonic acid (p-TSA) in batch reactor using concentrated solar radiation was investigated. The effect of the various operating parameters such as initial concentration of substrate, catalyst loading, solution pH and types of ions on photocatalytic degradation has been studied in a batch reactor to derive the optimum conditions. The rate of photocatalytic degradation was found to be maximum at the self pH (pH 3.34) of p-TSA. It was also observed that in the presence of anions and cations, the rate of PCD decreases drastically. The kinetics of photocatalytic degradation of p-TSA was studied. The PCD of p-TSA was also carried at these optimized conditions in a bench scale slurry bubble column reactor using concentrated solar radiation.

  8. Molecular screening of wine lactic acid bacteria degrading hydroxycinnamic acids.

    PubMed

    de las Rivas, Blanca; Rodríguez, Héctor; Curiel, José Antonio; Landete, José María; Muñoz, Rosario

    2009-01-28

    The potential to produce volatile phenols from hydroxycinnamic acids was investigated for lactic acid bacteria (LAB) isolated from Spanish grape must and wine. A PCR assay was developed for the detection of LAB that potentially produce volatile phenols. Synthetic degenerate oligonucleotides for the specific detection of the pdc gene encoding a phenolic acid decarboxylase were designed. The pdc PCR assay amplifies a 321 bp DNA fragment from phenolic acid decarboxylase. The pdc PCR method was applied to 85 strains belonging to the 6 main wine LAB species. Lactobacillus plantarum, Lactobacillus brevis, and Pediococcus pentosaceus strains produce a positive response in the pdc PCR assay, whereas Oenococcus oeni, Lactobacillus hilgardii, and Leuconostoc mesenteroides strains did not produce the expected PCR product. The production of vinyl and ethyl derivatives from hydroxycinnamic acids in culture media was determined by high-performance liquid chromatography. A relationship was found between pdc PCR amplification and volatile phenol production, so that the LAB strains that gave a positive pdc PCR response produce volatile phenols, whereas strains that did not produce a PCR amplicon did not produce volatile phenols. The proposed method could be useful for a preliminary identification of LAB strains able to produce volatile phenols in wine.

  9. Degradation of CYANEX 301 in Contact with Nitric Acid Media

    SciTech Connect

    Philippe Marc; Radu Custelcean; Gary S. Groenewold; John R. Klaehn; Dean R. Peterman; Laetitia H. Delmau

    2012-10-01

    The nature of the degradation product obtained upon contacting CYANEX 301 (bis(2,4,4-trimethylpentyl)dithiophosphinic acid) with nitric acid has been elucidated and found to be a disulfide derivative. The first step to the degradation of CYANEX 301 in toluene has been studied using 31P{1H} NMR after being contacted with nitric acid media. The spectrum of the degradation product exhibits a complex multiplet around dP = 80 ppm. A succession of purifications of CYANEX 301 has resulted in single crystals of the acidic form and the corresponding ammonium salt. Unlike the original CYANEX 301, which consists of a complex diastereomeric mixture displaying all possible combinations of chiral orientations at the 2-methyl positions, the purified crystals were shown by single-crystal X-ray diffraction to be racemates, containing 50:50 mixtures of the [R;R] and [S;S] diastereomers. The comparison between the 31P {1H} NMR spectra of the degradation products resulting from the diastereomerically pure CYANEX 301 and the original diastereomeric mixture has elucidated the influence of the isomeric composition on the multiplicity of the 31P {1H} NMR peak. These NMR data indicate the initial degradation leads to a disulfide-bridged condensation product displaying multiple resonances due to phosphorus–phosphorus coupling, which is caused by the inequivalence of the two P atoms as a result of their different chirality. A total of nine different NMR resonances, six of which display phosphorus–phosphorus coupling, could be assigned, and the identity of the peaks corresponding to phosphorus atoms coupled to each other was confirmed by 31P {1H} homodecoupled NMR analysis.

  10. Influence of Root Exudates on the Bacterial Degradation of Chlorobenzoic Acids

    PubMed Central

    Lovecká, Petra; Dražková, Milena; Macková, Martina; Macek, Tomas

    2013-01-01

    Degradation of chlorobenzoic acids (e.g., products of microbial degradation of PCB) by strains of microorganisms isolated from PCB contaminated soils was assessed. From seven bulk-soil isolates two strains unique in ability to degrade a wider range of chlorobenzoic acids than others were selected, individually and even in a complex mixture of 11 different chlorobenzoic acids. Such a feature is lacking in most tested degraders. To investigate the influence of vegetation on chlorobenzoic acids degraders, root exudates of two plant species known for supporting PCB degradation in soil were tested. While with individual chlorobenzoic acids the presence of plant exudates leads to a decrease of degradation yield, in case of a mixture of chlorobenzoic acids either a change in bacterial degradation specificity, associated with 3- and 4-chlorobenzoic acid, or an extension of the spectrum of degraded chlorobenzoic acids was observed. PMID:24222753

  11. Energetics and kinetics of anaerobic aromatic and fatty acid degradation. Progress report, March 1992--June 1995

    SciTech Connect

    McInerney M.J.

    1995-06-23

    Factors affecting the rate and extent of benzoate degradation by anaerobic syntrophic consortia were studied. Cocultures of a syntrophic benzoate degrader, strain SB, with a hydrogen/formate-using sulfate reducer degraded benzoate to a threshold that depended on the amount of substrate and acetate present. The benzoate threshold was not a function of the inhibition of benzoate degradation capacity by acetate or the toxicity of the undissociated form of acetate. Rather, a critical or minimal Gibb`s free energy value may exist where thermodynamic constraints preclude further benzoate degradation. A sensitive assay to detect low formate concentrations was developed to measure the formate levels when the benzoate threshold was reached. We showed that increased acetate concentrations, even when hydrogen and formate levels are low, affects the extent of benzoate degradation, implicating the importance of interspecies acetate transfer. In addition to benzoate, various saturated and unsaturated fatty acids, 2-methylbutyrate, and methyl esters of fatty acids supported growth in coculture with a hydrogen-using partner. SB is the only syntrophic bacterium known to use both benzoate and fatty acids. Phylogenetic analysis showed that SB clustered with sulfate reducers in the delta subclass of the Proteobacteria. SB grew well in coculture with Desulfoarculus baarsii, a sulfate reducer that uses formate but not hydrogen. This unequivocally shows that SB can grow by interspecies formate transfer.

  12. Adsorption and degradation of phenoxyalkanoic acid herbicides in soils: A review.

    PubMed

    Paszko, Tadeusz; Muszyński, Paweł; Materska, Małgorzata; Bojanowska, Monika; Kostecka, Małgorzata; Jackowska, Izabella

    2016-02-01

    The primary aim of the present review on phenoxyalkanoic acid herbicides-2-(2,4-dichlorophenoxy) acetic acid (2,4-D), 2-(4-chloro-2-methylphenoxy) acetic acid (MCPA), (2R)-2-(2,4-dichlorophenoxy) propanoic acid (dichlorprop-P), (2R)-2-(4-chloro-2-methylphenoxy) propanoic acid (mecoprop-P), 4-(2,4-dichlorophenoxy) butanoic acid (2,4-DB), and 4-(4-chloro-2-methylphenoxy) butanoic acid (MCPB)-was to compare the extent of their adsorption in soils and degradation rates to assess their potential for groundwater contamination. The authors found that adsorption decreased in the sequence of 2,4-DB > 2,4-D > MCPA > dichlorprop-P > mecoprop-P. Herbicides are predominantly adsorbed as anions-on organic matter and through a water-bridging mechanism with adsorbed Fe cations-and their neutral forms are adsorbed mainly on organic matter. Adsorption of anions of 2,4-D, MCPA, dichlorprop-P, and mecoprop-P is inversely correlated with their lipophilicity values, and modeling of adsorption of the compounds based on this relationship is possible. The predominant dissipation mechanism of herbicides in soils is bacterial degradation. The contribution of other mechanisms, such as degradation by fungi, photodegradation, or volatilization from soils, is much smaller. The rate of bacterial degradation decreased in the following order: 2,4-D > MCPA > mecoprop-P > dichlorprop-P. It was found that 2,4-D and MCPA have the lowest potential for leaching into groundwater and that mecoprop-P and dichlorprop-P have slightly higher potential. Because of limited data on adsorption and degradation of 2,4-DB and MCPB, estimation of their leaching potential was not possible.

  13. Correlation of hydrolytic degradation with structure for copolyesters produced from glycolic and adipic acids.

    PubMed

    Simitzis, J; Triantou, D; Soulis, S; Triantou, K; Simitzis, Ch; Zoumpoulakis, L

    2010-04-01

    Copolyesters based on glycolic acid (G) combined with adipic acid (A) and ethylene glycol (E) were synthesized in different percentage of molar ratios (A: 100-50% and G: 100%) and their hydrolytic degradation was studied and correlated with their structures. According to the DSC, the production of polyesters leads to the formation of copolyesters and not to mixtures of homopolyesters. The crystallites in the copolyesters mainly consist of continuous sequences of ethylene adipate structural units. The hydrolytic degradation of the polyesters was followed by their weight loss during hydrolysis and by the FTIR spectra of the initial polyesters compared with that of the degraded polyesters at equilibrium. The region between 1142 and 800 cm(-1) can be utilized to evaluate the extent of degradation of polyesters after their hydrolysis. The absorption bands at 1142, 1077 and 850 cm(-1) due to the amorphous region decrease after hydrolysis, whereas those at 972, 901 and 806 cm(-1) due to the crystalline region increase. The experimental data of the hydrolytic degradation were fitted with exponential rise to maximum type functions using two-parameter model, which describes very well mainly the initial part of the degradation, and four-parameter model (containing two exponential terms), which is appropriate for fitting the hydrolytic degradation on the entire time period (including the equilibrium). Furthermore, the kinetics of the hydrolytic degradation of the polyesters for the initial time period based on both models results to similar values of the rate constant, k. The synthesized copolyesters of glycolic acid combined with adipic acid and ethylene glycol are soluble in many common organic solvents opposite to PGA, leading to modified biodegradable polyesters and therefore they can be easily processed.

  14. Poly(amido-amine)-based hydrogels with tailored mechanical properties and degradation rates for tissue engineering.

    PubMed

    Martello, Federico; Tocchio, Alessandro; Tamplenizza, Margherita; Gerges, Irini; Pistis, Valentina; Recenti, Rossella; Bortolin, Monica; Del Fabbro, Massimo; Argentiere, Simona; Milani, Paolo; Lenardi, Cristina

    2014-03-01

    Poly(amido-amine) (PAA) hydrogels containing the 2,2-bisacrylamidoacetic acid-4-amminobutyl guanidine monomeric unit have a known ability to enhance cellular adhesion by interacting with the arginin-glycin-aspartic acid (RGD)-binding αVβ3 integrin, expressed by a wide number of cell types. Scientific interest in this class of materials has traditionally been hampered by their poor mechanical properties and restricted range of degradation rate. Here we present the design of novel biocompatible, RGD-mimic PAA-based hydrogels with wide and tunable degradation rates as well as improved mechanical and biological properties for biomedical applications. This is achieved by radical polymerization of acrylamide-terminated PAA oligomers in both the presence and absence of 2-hydroxyethylmethacrylate. The degradation rate is found to be precisely tunable by adjusting the PAA oligomer molecular weight and acrylic co-monomer concentration in the starting reaction mixture. Cell adhesion and proliferation tests on Madin-Darby canine kidney epithelial cells show that PAA-based hydrogels have the capacity to promote cell adhesion up to 200% compared to the control. Mechanical tests show higher compressive strength of acrylic chain containing hydrogels compared to traditional PAA hydrogels.

  15. Poly(lactic acid) degradable plastics, coatings, and binders

    SciTech Connect

    Bonsignore, P.V.; Coleman, R.D.; Mudde, J.P.

    1992-05-01

    Biochemical processes to derive value from the management of high carbohydrate food wastes, such as potato starch, corn starch, and cheese whey permeate, have typically been limited to the production of either ethanol or methane. Argonne National Laboratory (ANL) believes that lactic acid presents an attractive option for an alternate fermentation end product, especially in light of lactic acids` being a viable candidate for conversion to environmentally safe poly(lactic acid) (PLA) degradable plastics, coatings, and binders. Technology is being developed at ANL to permit a more cost effective route to modified high molecular weight PLA. Preliminary data on the degradation behavior of these modified PLAs shows the retention to the inherent hydrolytic degradability of the PLA modified, however, by introduced compositional variables. A limited study was done on the hydrolytic stability of soluble oligomers of poly(L-lactic acid). Over a 34 day hold period, water-methanol solutions of Pl-LA oligomers in the 2-10 DP range retained some 75% of their original molecular weight.

  16. Poly(lactic acid) degradable plastics, coatings, and binders

    SciTech Connect

    Bonsignore, P.V.; Coleman, R.D.; Mudde, J.P.

    1992-01-01

    Biochemical processes to derive value from the management of high carbohydrate food wastes, such as potato starch, corn starch, and cheese whey permeate, have typically been limited to the production of either ethanol or methane. Argonne National Laboratory (ANL) believes that lactic acid presents an attractive option for an alternate fermentation end product, especially in light of lactic acids' being a viable candidate for conversion to environmentally safe poly(lactic acid) (PLA) degradable plastics, coatings, and binders. Technology is being developed at ANL to permit a more cost effective route to modified high molecular weight PLA. Preliminary data on the degradation behavior of these modified PLAs shows the retention to the inherent hydrolytic degradability of the PLA modified, however, by introduced compositional variables. A limited study was done on the hydrolytic stability of soluble oligomers of poly(L-lactic acid). Over a 34 day hold period, water-methanol solutions of Pl-LA oligomers in the 2-10 DP range retained some 75% of their original molecular weight.

  17. Efficient degradation of tannic acid by black Aspergillus species.

    PubMed

    Van Diepeningen, Anne D; Debets, Alfons J M; Varga, Janos; van der Gaag, Marijn; Swart, Klaas; Hoekstra, Rolf F

    2004-08-01

    A set of aspergillus strains from culture collections and wild-type black aspergilli isolated on non-selective media were used to validate the use of media with 20% tannic acid for exclusive and complete selection of the black aspergilli. The 20% tannic acid medium proved useful for both quantitative and qualitative selection of all different black aspergilli, including all recognized species: A. carbonarius, A. japonicus, A. aculeatus, A foetidus, A. heteromorphus, A. niger, A. tubingensis and A. brasiliensis haplotypes. Even higher concentrations of tannic acid can be utilized by the black aspergilli suggesting a very efficient tannic acid-degrading system. Colour mutants show that the characteristic ability to grow on high tannic acid concentrations is not causally linked to the other typical feature of these aspergilli, i.e. the formation of brown-black pigments. Sequence analysis of the A. niger genome using the A. oryzae tannase gene yielded eleven tannase-like genes, far more than in related species. Therefore, a unique ecological niche in the degradation of tannic acid and connected nitrogen release seems to be reserved for these black-spored cosmopolitans.

  18. DNA Profiling Success Rates from Degraded Skeletal Remains in Guatemala.

    PubMed

    Johnston, Emma; Stephenson, Mishel

    2016-07-01

    No data are available regarding the success of DNA Short Tandem Repeat (STR) profiling from degraded skeletal remains in Guatemala. Therefore, DNA profiling success rates relating to 2595 skeletons from eleven cases at the Forensic Anthropology Foundation of Guatemala (FAFG) are presented. The typical postmortem interval was 30 years. DNA was extracted from bone powder and amplified using Identifiler and Minifler. DNA profiling success rates differed between cases, ranging from 50.8% to 7.0%, the overall success rate for samples was 36.3%. The best DNA profiling success rates were obtained from femur (36.2%) and tooth (33.7%) samples. DNA profiles were significantly better from lower body bones than upper body bones (p = <0.0001). Bone samples from males gave significantly better profiles than samples from females (p = <0.0001). These results are believed to be related to bone density. The findings are important for designing forensic DNA sampling strategies in future victim recovery investigations.

  19. Study on degradation kinetics of 2-(2-hydroxypropanamido) benzoic acid in aqueous solutions and identification of its major degradation product by UHPLC/TOF-MS/MS.

    PubMed

    Zhang, Qili; Guan, Jiao; Rong, Rong; Zhao, Yunli; Yu, Zhiguo

    2015-08-10

    A RP-HPLC method was developed and validated for the degradation kinetic study of 2-(2-hydroxypropanamido) benzoic acid (HPABA), a promising anti-inflammatory drug, which would provide a basis for further studies on HPABA. The effects of pH, temperature, buffer concentration and ionic strength on the degradation kinetics of HPABA were discussed. Experimental parameters such as degradation rate constants (k), activation energy (Ea), acid and alkali catalytic constants (k(ac), k(al)), shelf life (t1/2) and temperature coefficient (Q10) were calculated. The results indicated that degradation kinetics of HPABA followed zero-order reaction kinetics; degradation rate constants (k) of HPABA at different pH values demonstrated that HPABA was more stable in neutral and near-neutral conditions; the function of temperature on k obeyed the Arrhenius equation (r = 0.9933) and HPABA was more stable at lower temperature; with the increase of ionic strength and buffer concentration, the stability of HPABA was decreased. The major unknown degradation product of HPABA was identified by UHPLC/TOF-MS/MS with positive electrospray ionization. Results demonstrated that the hydrolysis product was the primary degradation product of HPABA and it was deduced as anthranilic acid.

  20. Degradation of Fe/N/C catalysts upon high polarization in acid medium.

    PubMed

    Goellner, Vincent; Baldizzone, Claudio; Schuppert, Anna; Sougrati, Moulay Tahar; Mayrhofer, Karl; Jaouen, Frédéric

    2014-09-14

    A comprehensive study of the degradation of a highly active Fe/N/C catalyst in acid medium is reported. An accelerated aging protocol was applied in the temperature range of 20 to 80 °C. From fundamental rotating-disc electrode studies and polymer electrolyte membrane fuel cell investigations combined with identical-location electron microscopy and Mößbauer spectroscopy at various stages of degradation, important insights into the structural and chemical changes of the catalyst were obtained. Most importantly, the degradation is strongly enhanced at elevated temperature, which is correlated to (i) increased carbon-corrosion rate and (ii) parallel non-preferential dissolution of the FeNx-based active sites. The degradation not only leads to a decreased ORR kinetics over time but also induces significant charge- and mass-transport resistances due to the collapse of the electrode structure.

  1. Nitrogen incorporation into lignite humic acids during microbial degradation

    SciTech Connect

    Dong, L.H.; Yuan, H.L.

    2009-07-01

    Previous study showed that nitrogen content in lignite humic acids (HA) increased significantly during lignite biodegradation. In this paper we evaluated the factors responsible for the increased level of N in HA and the formation of new nitrogen compound following microbial degradation. When the ammonium sulfate concentration in lignite medium was 0.5%, the N-content in HA was higher than that in the crude lignite humic acid (cHA); when the ammonium sulfate concentration was epsilon 0.5%, both the biodegraded humic acid (bHA) N-content and the content of bHA in lignite increased significantly, but at 2.0% no increase was observed. This indicated that HA incorporated N existing in the lignite medium, and more HA can incorporate more N with the increase of bHA amount in lignite during microbial degradation. CP/MAS {sup 15}N NMR analysis showed that the N incorporated into HA during biotransformation was in the form of free or ionized NH{sub 2}-groups in amino acids and sugars, as well as NH{sub 4}{sup +}. We propose nitrogen can be incorporated into HA biotically and abiotically. The high N content bHA has a potential application in agriculture since N is essential for plant growth.

  2. Isolation and characterization of monochloroacetic acid-degrading bacteria.

    PubMed

    Horisaki, Tadafumi; Yoshida, Eiko; Sumiya, Kaori; Takemura, Tetsuo; Yamane, Hisakazu; Nojiri, Hideaki

    2011-01-01

    Five Burkholderia strains (CL-1, CL-2, CL-3, CL-4, and CL-5) capable of degrading monochloroacetic acid (MCA) were isolated from activated sludge or soil samples gathered from several parts of Japan. All five isolates were able to grow on MCA as the sole source of carbon and energy, and argentometry and gas chromatography-mass spectroscopy analyses showed that these five strains consumed MCA completely and released chloride ions stoichiometrically within 25 h. The five isolates also grew on monobromoacetic acid, monoiodoacetic acid, and L-2-monochloropropionic acid as sole sources of carbon and energy. In addition, the five isolates could not grow with DCA but dehalogenate single chlorine from DCA. Because PCR analyses revealed that all five isolates have an identical group II dehalogenase gene fragment and no group I deh gene, only strain CL-1 was analyzed further. The partial amino acid sequence of the group II dehalogenase of strain CL-1, named DehCL1, showed 74.6% and 65.2% identities to corresponding regions of the two MCA dehalogenases, DehCI from Pseudomonas sp. strain CBS-3 and Hdl IVa from Burkholderia cepacia strain MBA4, respectively. The secondary-structure motifs of the haloacid dehalogenase (HAD) superfamily and the amino acid residues involved in substrate binding, catalysis, and hydrophobic pocket formation were conserved in the partial amino acid sequence of DehCL1.

  3. Degradation of 3-chloro-4-hydroxybenzoic acid in biological treated effluent by gamma irradiation

    NASA Astrophysics Data System (ADS)

    Chu, Libing; Wang, Jianlong

    2016-02-01

    Gamma irradiation-induced degradation of a chlorinated aromatic compound, 3-chloro-4-hydroxybenzoic acid (CHBA) in biological treated effluent was studied and the results were compared with those obtained in deionized water. Gamma irradiation led to a complete decomposition of CHBA and a partial mineralization in the treated effluent. The removal of CHBA followed the pseudo first-order reaction kinetic model and the rate constant in the treated effluent was 1.7-3.5 times lower than that in deionized water. The CHBA degradation rate was higher at acidic condition than at neutral and alkaline conditions. The radiolytic yield, G-value for CHBA degradation was lower in the treated effluent, which decreased with increase in absorbed doses and increased with increase in initial concentrations of CHBA. The degradation mechanism of CHBA using gamma irradiation was proposed through the oxidation by -OH and reduction by eaq- and H- radicals. As exposed to gamma irradiation, dechlorination takes place rapidly and combines with the oxidation and cleavage of the aromatic ring, producing chloride ions, small carboxylic acids, acetaldehyde and other intermediates into the solution.

  4. Degradation Kinetics and Mechanism of Lithospermic Acid under Low Oxygen Condition Using Quantitative 1H NMR with HPLC-MS

    PubMed Central

    Pan, Jianyang; Gong, Xingchu; Qu, Haibin

    2016-01-01

    A novel quantitative 1H NMR (Q-NMR) combined with HPLC-MS method has been proposed for investigating the degradation process of traditional Chinese medicine (TCM) components. Through this method, in-situ monitoring of dynamics degradation process of lithospermic acid (LA), one of the popular polyphenolic acids in TCM, was realized under low oxygen condition. Additionally, this methodology was proved to be simple, rapid and specific. Degradation kinetic runs have been carried out to systematically investigate the effects of two key environmental factors, initial pH values and temperatures. Eight main degradation products of LA were detected, seven of which were tentatively structural elucidated with the help of both NMR and LC-MS in this work and salvianolic acid A (Sal A) was the primary degradation product of LA. A possible degradation pathway of LA was proposed, subsequently. The results showed that the degradation of LA followed pseudo-first-order kinetics. The apparent degradation kinetic constants increased as the initial pH value of the phosphate buffer increased. Under the given conditions, the rate constants of overall degradation as a function of temperature obeyed the Arrhenius equation. Our results proved that the Q-NMR combined with HPLC-MS method can be one of the most promising techniques for investigating degradation process of active components in TCM. PMID:27776128

  5. Study of kinetics of degradation of cyclohexane carboxylic acid by acclimated activated sludge.

    PubMed

    Wang, Chunhua; Shi, Shuian; Chen, Hongyan

    2016-01-01

    Activated sludge contains complex microorganisms, which are highly effective biodegrading agents. In this study, the kinetics of biodegradation of cyclohexane carboxylic acid (CHCA) by an acclimated aerobic activated sludge were investigated. The results showed that after 180 days of acclimation, the activated sludge could steadily degrade >90% of the CHCA in 120 h. The degradation of CHCA by the acclimated activated sludge could be modeled using a first-order kinetics equation. The equations for the degradation kinetics for different initial CHCA concentrations were also obtained. The kinetics constant, kd, decreased with an increase in the CHCA concentration, indicating that, at high concentrations, CHCA had an inhibiting effect on the microorganisms in the activated sludge. The effects of pH on the degradation kinetics of CHCA were also investigated. The results showed that a pH of 10 afforded the highest degradation rate, indicating that basic conditions significantly promoted the degradation of CHCA. Moreover, it was found that the degradation efficiency for CHCA increased with an increase in temperature and concentration of dissolved oxygen under the experimental conditions.

  6. Kinetics and Quantitative Structure—Activity Relationship Study on the Degradation Reaction from Perfluorooctanoic Acid to Trifluoroacetic Acid

    PubMed Central

    Gong, Chen; Sun, Xiaomin; Zhang, Chenxi; Zhang, Xue; Niu, Junfeng

    2014-01-01

    Investigation of the degradation kinetics of perfluorooctanoic acid (PFOA) has been carried out to calculate rate constants of the main elementary reactions using the multichannel Rice-Ramsperger-Kassel-Marcus theory and canonical variational transition state theory with small-curvature tunneling correction over a temperature range of 200~500 K. The Arrhenius equations of rate constants of elementary reactions are fitted. The decarboxylation is role step in the degradation mechanism of PFOA. For the perfluorinated carboxylic acids from perfluorooctanoic acid to trifluoroacetic acid, the quantitative structure–activity relationship of the decarboxylation was analyzed with the genetic function approximation method and the structure–activity model was constructed. The main parameters governing rate constants of the decarboxylation reaction from the eight-carbon chain to the two-carbon chain were obtained. As the structure–activity model shows, the bond length and energy of C1–C2 (RC1–C2 and EC1–C2) are positively correlated to rate constants, while the volume (V), the energy difference between EHOMO and ELUMO (ΔE), and the net atomic charges on atom C2 (QC2) are negatively correlated. PMID:25196516

  7. Perfluorooctanoic Acid Degradation Using UV-Persulfate Process: Modeling of the Degradation and Chlorate Formation.

    PubMed

    Qian, Yajie; Guo, Xin; Zhang, Yalei; Peng, Yue; Sun, Peizhe; Huang, Ching-Hua; Niu, Junfeng; Zhou, Xuefei; Crittenden, John C

    2016-01-19

    In this study, we investigated the destruction and by-product formation of perfluorooctanoic acid (PFOA) using ultraviolet light and persulfate (UV-PS). Additionally, we developed a first-principles kinetic model to simulate both PFOA destruction and by-product and chlorate (ClO3(-)) formation in ultrapure water (UW), surface water (SW), and wastewater (WW). PFOA degradation was significantly suppressed in the presence of chloride and carbonate species and did not occur until all the chloride was converted to ClO3(-) in UW and for low DOC concentrations in SW. The model was able to simulate the PS decay, pH changes, radical concentrations, and ClO3(-) formation for UW and SW. However, our model was unable to simulate PFOA degradation well in WW, possibly from PS activation by NOM, which in turn produced sulfate radicals.

  8. Influence of volatile fatty acid concentration stability on anaerobic degradation of linear alkylbenzene sulfonate.

    PubMed

    Okada, Dagoberto Y; Delforno, Tiago P; Esteves, Andressa S; Polizel, Juliana; Hirasawa, Julia S; Duarte, Iolanda C S; Varesche, Maria B A

    2013-10-15

    Linear alkylbenzene sulfonate (LAS) is an anionic surfactant used in cleaning products, which is usually found in wastewaters. Despite the greater LAS removal rate related to a lower concentrations of volatile fatty acids (VFA), the influence of different ranges of VFA on LAS degradation is not known. LAS degradation was evaluated in upflow anaerobic sludge blanket (UASB) and expanded granular sludge bed (EGSB) reactors at different ranges of VFA concentrations. The reactors were fed with a synthetic wastewater containing LAS (14 mg/L). A greater LAS removal rate (40-80%) was related to the lower and narrower range of acetic acid concentration (1-22 mg/L) in the EGSB reactor. In the UASB reactor, the acetic acid concentrations presented a wider range (2-45 mg/L), and some low LAS removal rates (around 20-25%) were observed even at low acetic acid concentrations (<10 mg/L). The high recirculation rate in the EGSB reactor improved substrate-biomass contact, which resulted in a narrower range of VFA and greater LAS removal rate.

  9. Phenolic acid degradation potential and growth behavior of lactic acid bacteria in sunflower substrates.

    PubMed

    Fritsch, Caroline; Heinrich, Veronika; Vogel, Rudi F; Toelstede, Simone

    2016-08-01

    Sunflower flour provides a high content of protein with a well-balanced amino acid composition and is therefore regarded as an attractive source for protein. The use for human nutrition is hindered by phenolic compounds, mainly chlorogenic acid, which can lead under specific circumstances to undesirable discolorations. In this study, growth behavior and degradation ability of chlorogenic acid of four lactic acid bacteria were explored. Data suggested that significant higher fermentation performances on sunflower flour as compared to sunflower protein concentrate were reached by Lactobacillus plantarum, Pediococcus pentosaceus, Lactobacillus gasseri and Bifidobacterium animalis subsp. lactis. In fermentation with the latter two strains reduced amounts of chlorogenic acid were observed in sunflower flour (-11.4% and -19.8%, respectively), which were more pronounced in the protein concentrate (-50.7% and -95.6%, respectively). High tolerances against chlorogenic acid and the cleavage product quinic acid with a minimum inhibitory concentration (MIC) of ≥20.48 mg/ml after 48 h were recorded for all strains except Bifidobacterium animalis subsp. lactis, which was more sensitive. The second cleavage compound, caffeic acid revealed a higher antimicrobial potential with MIC values of 0.64-5.12 mg/ml. In this proof of concept study, degradation versus inhibitory effect suggest the existence of basic mechanisms of interaction between phenolic acids in sunflower and lactic acid bacteria and a feasible way to reduce the chlorogenic acid content, which may help to avoid undesired color changes.

  10. The effect of sorption on the degradation of aromatic acids and bases

    SciTech Connect

    Ainsworth, C.C.; Fredrickson, J.K.; Smith, S.C.

    1992-10-01

    The availability and degradation of selected ionizable organic compounds sorbed to pure mineral phases are discussed. Substrates sorbed to mineral surfaces may or may not be protected from microbial attack; the degree of protection appears to be dependent on the type and cell density of the microorganism involved. The currently available data, however, demonstrate that there is little, if any, consensus on the types of reactions or interactions that facilitate sorbed substrate utilization. Rates of degradation of organic bases and cations that sorb to clay minerals via an exchange reaction are suggested to be directly related to substrate binding intensity and conformation on the clay surface. Similarly, rates of degradation of organic acids sorbed to the surface of oxides are suggested to be related to their interaction with the surface and the type of oxide sorbent. Although the rate-limiting step in microbial utilization of sorbed acids and bases is apparently a desorption process, the rate of desorption is itself linked to the compound`s binding intensities on a given sorbent. Thus, as the binding intensities of compounds increase, chemical kinetic reactions, rather than mass-transfer processes, appear to limit the rate of desorption.

  11. The effect of sorption on the degradation of aromatic acids and bases

    SciTech Connect

    Ainsworth, C.C.; Fredrickson, J.K.; Smith, S.C.

    1992-10-01

    The availability and degradation of selected ionizable organic compounds sorbed to pure mineral phases are discussed. Substrates sorbed to mineral surfaces may or may not be protected from microbial attack; the degree of protection appears to be dependent on the type and cell density of the microorganism involved. The currently available data, however, demonstrate that there is little, if any, consensus on the types of reactions or interactions that facilitate sorbed substrate utilization. Rates of degradation of organic bases and cations that sorb to clay minerals via an exchange reaction are suggested to be directly related to substrate binding intensity and conformation on the clay surface. Similarly, rates of degradation of organic acids sorbed to the surface of oxides are suggested to be related to their interaction with the surface and the type of oxide sorbent. Although the rate-limiting step in microbial utilization of sorbed acids and bases is apparently a desorption process, the rate of desorption is itself linked to the compound's binding intensities on a given sorbent. Thus, as the binding intensities of compounds increase, chemical kinetic reactions, rather than mass-transfer processes, appear to limit the rate of desorption.

  12. Screening, selection and characterization of phytic acid degrading lactic acid bacteria from chicken intestine.

    PubMed

    Raghavendra, Ponnala; Halami, Prakash M

    2009-07-31

    This study was undertaken to screen and select potent phytate degrading lactic acid bacteria and to evaluate their additional characteristic features. Forty lactic acid bacterial strains were isolated from different sources and screened for their ability to degrade myo-inositol hexaphosphate or IP(6) by cobalt chloride staining (plate assay) method, using calcium or sodium salt of phytic acid as substrate. All the forty isolates were able to degrade calcium phytate. However, only two Pediococcus pentosaceus strains (CFR R38 and CFR R35) were found to degrade sodium phytate. These strains showed phytase activity of 213 and 89 U at 50 degrees C, respectively and poor acid phosphatase activity. These strains were further evaluated for additional characteristic features. At pH 2, P. pentosaceus strains CFR R38 and CFR R35 showed 50.7 and 48.5 percentage survivability after 2 h of incubation respectively and they could also withstand 0.3% ox-bile. These cultures exhibited 54.6 and 44.8% of hydrophobicity to xylene, antibacterial activity against food borne pathogens and possessed beta-galactosidase activity. The resistance pattern to several antibiotics was also analyzed. The present study indicates that these strains, having phytate degrading ability and other characteristic features can be exploited as starter cultures in fermented foods to improve the mineral bioavailability.

  13. Hydrothermal synthesis spherical TiO2 and its photo-degradation property on salicylic acid

    NASA Astrophysics Data System (ADS)

    Guo, Wenlu; Liu, Xiaolin; Huo, Pengwei; Gao, Xun; Wu, Di; Lu, Ziyang; Yan, Yongsheng

    2012-07-01

    Anatase TiO2 spheres have been prepared using hydrothermal synthesis. The prepared spheres were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and UV-vis diffuse reflectance spectra (UV-vis DRS). The TiO2 consisted of well-defined spheres with size of 3-5 μm. The photocatalytic activity of spherical TiO2 was determined by degradation of salicylic acid under visible light irradiation. It was revealed that the degradation rate of the spherical TiO2 which was processed at 150 °C for 48 h could reach 81.758%. And the kinetics of photocatalytic degradation obeyed first-order kinetic, which the rate constant value was 0.01716 S-1 of the salicylic acid onto TiO2 (temperature: 150, time: 48 h). The kinetics of adsorption followed the pseudo-second-order model and the rate constant was 1.2695 g mg-1 of the salicylic acid onto TiO2 (temperature: 150, time: 48 h).

  14. Pyrazinoic acid decreases peritoneal transfer rates.

    PubMed

    Grzegorzewska, A E; Czyzewska, K; Szary, B

    1995-01-01

    It was shown elsewhere that in a peritoneally dialyzed woman with pulmonary tuberculosis, oral treatment with rifampicin and pyrazinamide (11 and 25 mg/kg/day, respectively) caused a decrease in the peritoneal transport of sodium, potassium, urea, uric acid, protein, and ultrafiltration rate by 48% to 75% compared to the pretreatment values. Pyrazinoic acid (PA), a metabolite of pyrazinamide, may account for these changes, because rifampicin was also previously used in this patient without peritoneal function impairment. Thus in the present study the influence of PA on the human peritoneum is examined using the modified Ussing-type chamber. PA (1 mg/dL) was introduced into the medium on the interstitial side of the membrane. After the introduction of PA, uric acid transfer from the interstitial to the mesothelial side decreased by about 50%. There were no significant changes in the urea and albumin transfer rates. In conclusion, PA induces changes in uric acid transfer acting directly on mesothelial cells, whereas a decrease in the peritoneal transfer of other solutes may be caused by a decrease in convective transfer rates due to impaired ultrafiltration.

  15. Degradation of reactive, acid and basic textile dyes in the presence of ultrasound and rare earths [Lanthanum and Praseodymium].

    PubMed

    Srivastava, Pankaj; Goyal, Shikha; Patnala, Prem Kishore

    2014-11-01

    Degradation of five textile dyes, namely Reactive Red 141 (RR 141), Reactive Blue 21 (RB 21), Acid Red 114 (AR 114), Acid Blue 113 (AB 113) and Basic Violet 16 (BV 16) in aqueous solution has been carried out with ultrasound (US) and in combination with rare earth ions (La(3+) and Pr(3+)). Kinetic analysis of the data showed a pseudo-first order degradation reaction for all the dyes. The rate constant (k), half life (t1/2) and the process efficiency (φ) for various processes in degradation of dyes under different experimental conditions have been calculated. The influence of concentrations of dyes (16-40mg/L), pH (5, 7 and 9) and rare earth ion concentration (4, 12 and 20mg/L) on the degradation of dyes have also been studied. The degradation percentage increased with increasing rare earth amount and decreased with increasing concentration of dyes. Both horn and bath type sonicators were used at 20kHz and 250W for degradation. The sonochemical degradation rate of dyes in the presence of rare earths was related to the type of chromophoric groups in the dye molecule. Degradation sequence of dyes was further examined through LCMS and Raman spectroscopic techniques, which confirmed the sonochemical degradation of dyes to non-toxic end products.

  16. α-Amino acid containing degradable polymers as functional biomaterials: rational design, synthetic pathway, and biomedical applications.

    PubMed

    Sun, Huanli; Meng, Fenghua; Dias, Aylvin A; Hendriks, Marc; Feijen, Jan; Zhong, Zhiyuan

    2011-06-13

    Currently, biomedical engineering is rapidly expanding, especially in the areas of drug delivery, gene transfer, tissue engineering, and regenerative medicine. A prerequisite for further development is the design and synthesis of novel multifunctional biomaterials that are biocompatible and biologically active, are biodegradable with a controlled degradation rate, and have tunable mechanical properties. In the past decades, different types of α-amino acid-containing degradable polymers have been actively developed with the aim to obtain biomimicking functional biomaterials. The use of α-amino acids as building units for degradable polymers may offer several advantages: (i) imparting chemical functionality, such as hydroxyl, amine, carboxyl, and thiol groups, which not only results in improved hydrophilicity and possible interactions with proteins and genes, but also facilitates further modification with bioactive molecules (e.g., drugs or biological cues); (ii) possibly improving materials biological properties, including cell-materials interactions (e.g., cell adhesion, migration) and degradability; (iii) enhancing thermal and mechanical properties; and (iv) providing metabolizable building units/blocks. In this paper, recent developments in the field of α-amino acid-containing degradable polymers are reviewed. First, synthetic approaches to prepare α-amino acid-containing degradable polymers will be discussed. Subsequently, the biomedical applications of these polymers in areas such as drug delivery, gene delivery and tissue engineering will be reviewed. Finally, the future perspectives of α-amino acid-containing degradable polymers will be evaluated.

  17. Coordinated Regulation of Species-Specific Hydroxycinnamic Acid Degradation and Siderophore Biosynthesis Pathways in Agrobacterium fabrum

    PubMed Central

    Baude, Jessica; Vial, Ludovic; Villard, Camille; Campillo, Tony; Lavire, Céline; Nesme, Xavier

    2016-01-01

    ABSTRACT The rhizosphere-inhabiting species Agrobacterium fabrum (genomospecies G8 of the Agrobacterium tumefaciens species complex) is known to degrade hydroxycinnamic acids (HCAs), especially ferulic acid and p-coumaric acid, via the novel A. fabrum HCA degradation pathway. Gene expression profiles of A. fabrum strain C58 were investigated in the presence of HCAs, using a C58 whole-genome oligoarray. Both ferulic acid and p-coumaric acid caused variations in the expression of more than 10% of the C58 genes. Genes of the A. fabrum HCA degradation pathway, together with the genes involved in iron acquisition, were among the most highly induced in the presence of HCAs. Two operons coding for the biosynthesis of a particular siderophore, as well as genes of the A. fabrum HCA degradation pathway, have been described as being specific to the species. We demonstrate here their coordinated expression, emphasizing the interdependence between the iron concentration in the growth medium and the rate at which ferulic acid is degraded by cells. The coordinated expression of these functions may be advantageous in HCA-rich but iron-starved environments in which microorganisms have to compete for both iron and carbon sources, such as in plant roots. The present results confirm that there is cooperation between the A. fabrum-specific genes, defining a particular ecological niche. IMPORTANCE We previously identified seven genomic regions in Agrobacterium fabrum that were specifically present in all of the members of this species only. Here we demonstrated that two of these regions, encoding the hydroxycinnamic acid degradation pathway and the iron acquisition pathway, were regulated in a coordinated manner. The coexpression of these functions may be advantageous in hydroxycinnamic acid-rich but iron-starved environments in which microorganisms have to compete for both iron and carbon sources, such as in plant roots. These data support the view that bacterial genomic species

  18. Degradation of Acid Orange 7 in an Atmospheric-Pressure Plasma-Solution System (Gliding Discharge)

    NASA Astrophysics Data System (ADS)

    NI, Mingjiang; YANG, Huan; CHEN, Tong; ZHANG, Hao; WU, Angjian; DU, Changming; LI, Xiaodong

    2015-03-01

    In this work, a plasma-solution system was applied to the degradation of Acid Orange 7 (AO7). The effects of initial concentration and type of feed gases (air, oxygen, nitrogen or argon) were studied. As the initial concentration increased from 100 mg/L to 160 mg/L, the discolouration rate of AO7 decreased from 99.3% to 95.9%, whereas the COD removal rate decreased from 37.9% to 22.6%. Air provided the best discolouration and COD removal rates (99.3% and 37.9%, respectively). In the presence of a zero-valent iron (ZVI) catalyst, the AO7 COD removal rate increased to 76.4%. The degradation products were analysed by a GC-MS, revealing that the degradation of the dye molecule was initiated through the cleavage of the -N=N- bond before finally being converted to organic acids. supported by National Natural Science Foundation of China (Nos. 50908237, 51076142) and the Open Foundation of the State Key Laboratory of Clean Energy Utilization of China (No. ZJUCEU2009008)

  19. Mechanism of Calcium Lactate Facilitating Phytic Acid Degradation in Soybean during Germination.

    PubMed

    Hui, Qianru; Yang, Runqiang; Shen, Chang; Zhou, Yulin; Gu, Zhenxin

    2016-07-13

    Calcium lactate facilitates the growth and phytic acid degradation of soybean sprouts, but the mechanism is unclear. In this study, calcium lactate (Ca) and calcium lactate with lanthanum chloride (Ca+La) were used to treat soybean sprouts to reveal the relevant mechanism. Results showed that the phytic acid content decreased and the availability of phosphorus increased under Ca treatment. This must be due to the enhancement of enzyme activity related to phytic acid degradation. In addition, the energy metabolism was accelerated by Ca treatment. The energy status and energy metabolism-associated enzyme activity also increased. However, the transmembrane transport of calcium was inhibited by La(3+) and concentrated in intercellular space or between the cell wall and cell membrane; thus, Ca+La treatment showed reverse results compared with those of Ca treatment. Interestingly, gene expression did not vary in accordance with their enzyme activity. These results demonstrated that calcium lactate increased the rate of phytic acid degradation by enhancing growth, phosphorus metabolism, and energy metabolism.

  20. Degradation Kinetics and Mechanism of a β-Lactam Antibiotic Intermediate, 6-Aminopenicillanic Acid, in a New Integrated Production Process.

    PubMed

    Su, Min; Sun, Hua; Zhao, Yingying; Lu, Aidang; Cao, Xiaohui; Wang, Jingkang

    2016-01-01

    In an effort to promote sustainability and to reduce manufacturing costs, the traditional production process for 6-aminopenicillanic acid (6-APA) has been modified to include less processing units. The objectives of this study are to investigate the degradation kinetics of 6-APA, to propose a reasonable degradation mechanism, and to optimize the manufacturing conditions within this new process. A series of degradation kinetic studies were conducted in the presence of impurities, as well as at various chemical and physical conditions. The concentrations of 6-APA were determined by high-performance liquid chromatography. An Arrhenius-type kinetic model was established to give a more accurate prediction on the degradation rates of 6-APA. A hydrolysis degradation mechanism is shown to be the major pathway for 6-APA. The degradation mechanisms and the kinetic models for 6-APA in the new system enable the design of a good manufacturing process with optimized parameters.

  1. CHLORINATION OF AMINO ACIDS: REACTION PATHWAYS AND REACTION RATES.

    PubMed

    How, Zuo Tong; Linge, Kathryn; Busetti, Francesco; Joll, Cynthia A

    2017-03-15

    Chlorination of amino acids can result in the formation of organic monochloramines or organic dichloramines, depending on the chlorine to amino acid ratio (Cl:AA). After formation, organic chloramines degrade into aldehydes, nitriles and N-chloraldimines. In this paper, the formation of organic chloramines from chlorination of lysine, tyrosine and valine were investigated. Chlorination of tyrosine and lysine demonstrated that the presence of a reactive secondary group can increase the Cl:AA ratio required for the formation of N,N-dichloramines, and potentially alter the reaction pathways between chlorine and amino acids, resulting in the formation of unexpected by-products. In a detailed investigation, we report rate constants for all reactions in the chlorination of valine, for the first time, using experimental results and modelling. At Cl:AA = 2.8, the chlorine was found to first react quickly with valine (5.4x104 M-1 s-1) to form N-monochlorovaline, with a slower subsequent reaction with N-monochlorovaline to form N,N-dichlorovaline (4.9x102 M-1 s-1), although some N-monochlorovaline degraded into isobutyraldehyde (1.0x10-4 s-1). The N,N-dichlorovaline then competitively degraded into isobutyronitrile (1.3x10-4 s-1) and N-chloroisobutyraldimine (1.2x10-4 s-1). In conventional drinking water disinfection, N-chloroisobutyraldimine can potentially be formed in concentrations higher than its odour threshold concentration, resulting in aesthetic challenges and an unknown health risk.

  2. Production and Degradation of Oxalic Acid by Brown Rot Fungi

    PubMed Central

    Espejo, Eduardo; Agosin, Eduardo

    1991-01-01

    Our results show that all of the brown rot fungi tested produce oxalic acid in liquid as well as in semisolid cultures. Gloeophyllum trabeum, which accumulates the lowest amount of oxalic acid during decay of pine holocellulose, showed the highest polysaccharide-depolymerizing activity. Semisolid cultures inoculated with this fungus rapidly converted 14C-labeled oxalic acid to CO2 during cellulose depolymerization. The other brown rot fungi also oxidized 14C-labeled oxalic acid, although less rapidly. In contrast, semisolid cultures inoculated with the white rot fungus Coriolus versicolor did not significantly catabolize the acid and did not depolymerize the holocellulose during decay. Semisolid cultures of G. trabeum amended with desferrioxamine, a specific iron-chelating agent, were unable to lower the degree of polymerization of cellulose or to oxidize 14C-labeled oxalic acid to the extent or at the rate that control cultures did. These results suggest that both iron and oxalic acid are involved in cellulose depolymerization by brown rot fungi. PMID:16348522

  3. Energetics and kinetics of anaerobic aromatic and fatty acid degradation

    SciTech Connect

    McInerney, M.J.

    1992-11-16

    The kinetics of benzoate degradation by the anaerobic syntrophic bacterium, Syntrophus buswellii, was studied in coculture with Desulfovibrio strain G11. The threshold value for benzoate degradation was dependent on the acetate concentration with benzoate threshold values ranging from 2.4 [mu]M at 20 mM acetate to 30.0 [mu]M at 65 mM acetate. Increasing acetate concentrations also inhibited the rate of benzoate degradation with a apparent K[sub i] for acetate inhibition of 7.0 mM. Lower threshold values were obtained when nitrate rather than sulfate was the terminal electron acceptor. These data are consistent with a thermodynamic explanation for the threshold, and suggest that there is a minimum Gibbs free energy value required for the degradation of benzoate. An acetoacetyl-CoA thiolase has been isolated from Syntrophomonas wolfei; it is apparently a key enzyme controlling the synthesis of poly-B-hydroxyalkanoate from acetyl-CoA in this organism. Kinetic characterization of the acetoacetyl-CoA thiolase from S. wolfei showed that it is similar in its structural, kinetic, and apparent regulatory properties to other biosynthetic acetoacetyl-CoA thiolases from phylogenetically distinct bacteria that synthesize PHA. Intracellular concentrations of CoA and acetyl-CoA are believed to be critical factors regulating the activity of the acetoacetyl-CoA thiolase in S. wolfei. We have also isolated and characterized several new halophilic anaerobic fermentative anaerobes. Phylogenetic analysis indicates that one of these bacteria is a new species in the genus, Haloanaerobium. Two other species appear to be members of the genus, Halobacteroides. Several halophilic acetoclastic methanogenic bacteria have also been isolated and their physiological properties are currently under investigation. We have also isolated an acetate-using dissimilatory iron-reducing bacterium.

  4. Proteins iodinated by the chloramine-T method appear to be degraded at an abnormally rapid rate after endocytosis

    SciTech Connect

    Opresko, L.; Wiley, H.S.; Wallace, R.A.

    1980-03-01

    Proteins labeled with either /sup 3/H by reductive methylation or /sup 125/I by the chloramine-T method were incubated with Xenopus laevis oocytes; the incorporation and acid precipitability of the proteins were then studied. The uptake rates of both specifically incorporated (vitellogenin) and nonspecifically incorporated proteins (bovine serum albumin and X. laevis serum proteins lacking albumins) were not influenced by the method of labeling. However, /sup 125/I-labeled proteins were apparently degraded at rates far exceeding their /sup 3/H-labeled counterparts, based on the generation of acid-soluble radioactivity. Apparent degradation rates observed for endocytotically incorporated proteins may vary depending on the method used to label the protein and caution should be exercised when interpreting results obtained with labeled, particularly chloramine-T labeled, proteins.

  5. Molecular products from the thermal degradation of glutamic acid.

    PubMed

    Kibet, Joshua K; Khachatryan, Lavrent; Dellinger, Barry

    2013-08-14

    The thermal behavior of glutamic acid was investigated in N2 and 4% O2 in N2 under flow reactor conditions at a constant residence time of 0.2 s, within a total pyrolysis time of 3 min at 1 atm. The identification of the main pyrolysis products has been reported. Accordingly, the principal products for pyrolysis in order of decreasing abundance were succinimide, pyrrole, acetonitrile, and 2-pyrrolidone. For oxidative pyrolysis, the main products were succinimide, propiolactone, ethanol, and hydrogen cyanide. Whereas benzene, toluene, and a few low molecular weight hydrocarbons (propene, propane, 1-butene, and 2-butene) were detected during pyrolysis, no polycyclic aromatic hydrocarbons (PAHs) were detected. Oxidative pyrolysis yielded low molecular weight hydrocarbon products in trace amounts. The mechanistic channels describing the formation of the major product succinimide have been explored. The detection of succinimide (major product) and maleimide (minor product) from the thermal decomposition of glutamic acid has been reported for the first time in this study. Toxicological implications of some reaction products (HCN, acetonitrile, and acyrolnitrile), which are believed to form during heat treatment of food, tobacco burning, and drug processing, have been discussed in relation to the thermal degradation of glutamic acid.

  6. Docosahexaenoic acid ester degradation measured by FTIR-ATR with correlation spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Highly unsaturated fatty acids such as docosahexaenoic acid and linolenic acid are prone to oxidation with a resulting loss of bioactivity and generation of malodorous degradation compounds. Degradation proceeds by formation of the corresponding hydroperoxyl free radical with subsequent oxidative cl...

  7. Photocatalytic degradation of commercially sourced naphthenic acids by TiO2-graphene composite nanomaterial.

    PubMed

    Liu, Juncheng; Wang, Lin; Tang, Jingchun; Ma, Jianli

    2016-04-01

    Naphthenic acids (NAs) are a major contributor to the toxicity in oil sands process-affected water (OSPW), which is produced by hot water extraction of bitumen. NAs are extremely difficult to be degraded due to its complex ring and side chain structure. Photocatalysis is recognized as a promising technology in the removal of refractory organic pollutants. In this work, TiO2-graphene (P25-GR) composites were synthesized by means of solvothermal method. The results showed that P25-GR composite exhibited better photocatalytic activity than pure P25. The removal efficiency of naphthenic acids in acid solution was higher than that in neutral and alkaline solutions. It was the first report ever known on the photodegradation of NAs based on graphene, and this process achieved a higher removal rate than other photocatalysis degradation of NAs in a shorter reaction time. LC/MS analysis showed that macromolecular NAs (carbon number 17-22, z value -2) were easy to be degraded than the micromolecular ones (carbon number 11-16, z value -2). Furthermore, the reactive oxygen species that play the main role in the photocatalysis system were studied. It was found that holes and ·OH were the main reactive species in the UV/P25-GR photocatalysis system. Given the high removal efficiency of refractory organic pollutants and the short degradation time, photodegradation based on composite catalysts has a broad and practical prospect. The study on the photodegradation of commercially sourced NAs may provide a guidance for the degradation of OSPW NAs by this method.

  8. Effects of material thickness and processing method on poly(lactic-co-glycolic acid) degradation and mechanical performance.

    PubMed

    Shirazi, Reyhaneh Neghabat; Aldabbagh, Fawaz; Ronan, William; Erxleben, Andrea; Rochev, Yury; McHugh, Peter

    2016-10-01

    In this study, the effects of material thickness and processing method on the degradation rate and the changes in the mechanical properties of poly(lactic-co-glycolic acid) material during simulated physiological degradation were investigated. Two types of poly(lactic-co-glycolic acid) materials were considered: 0.12 mm solvent-cast films and 1 mm compression-moulded plates. The experimental results presented in this study were compared to the experimental results of Shirazi et al. (Acta Biomaterialia 10(11):4695-703, 2014) for 0.25 mm solvent-cast films. These experimental observations were used to validate the computational modelling predictions of Shirazi et al. (J Mech Behav Biomed Mater 54: 48-59, 2016) on critical diffusion length scale and also to refine the model parameters. The specific material processing methods considered here did not have a significant effect on the degradation rate and the changes in mechanical properties during degradation; however, they influenced the initial molecular weight and they determined the stiffness and hardness of the poly(lactic-co-glycolic acid) material. The experimental observations strongly supported the computational modelling predictions that showed no significant difference in the degradation rate and the changes in the elastic modulus of poly(lactic-co-glycolic acid) films for thicknesses larger than 100 μm.

  9. Use of Pyranometers to Estimate PV Module Degradation Rates in the Field

    SciTech Connect

    Vignola, Frank; Peterson, Josh; Kessler, Rich; Mavromatakis, Fotis; Dooraghi, Mike; Sengupta, Manajit

    2016-11-21

    Methodology is described that uses relative measurements to estimate the degradation rates of PV modules in the field. The importance of calibration and cleaning is discussed. The number of years of field measurements needed to measure degradation rates with data from the field is cut in half using relative comparisons.

  10. Use of Pyranometers to Estimate PV Module Degradation Rates in the Field: Preprint

    SciTech Connect

    Vignola, Frank; Peterson, Josh; Kessler, Rich; Mavromatakis, Fotis; Dooraghi, Mike; Sengupta, Manajit

    2016-08-01

    This paper describes a methodology that uses relative measurements to estimate the degradation rates of PV modules in the field. The importance of calibration and cleaning is illustrated. The number of years of field measurements needed to measure degradation rates with data from the field is cut in half using relative comparisons.

  11. Use of Pyranometers to Estimate PV Module Degradation Rates in the Field

    SciTech Connect

    Vignola, Frank; Peterson, Josh; Kessler, Rich; Mavromatakis, Fotis; Dooraghi, Mike; Sengupta, Manajit

    2016-06-05

    This poster provides an overview of a methodology that uses relative measurements to estimate the degradation rates of PV modules in the field. The importance of calibration and cleaning is illustrated. The number of years of field measurements needed to measure degradation rates with data from the field is cut in half using relative comparisons.

  12. Free fatty acids degradation in grease trap purification using ozone bubbling and sonication

    NASA Astrophysics Data System (ADS)

    Piotr Kwiatkowski, Michal; Satoh, Saburoh; Fukuda, Shogo; Yamabe, Chobei; Ihara, Satoshi; Nieda, Masanori

    2013-02-01

    The oil and fat were treated at first by only ozone bubbling and it was confirmed that the collection efficiency of them became 98.4% when the aeration was used. It showed that the aeration method in a grease trap cleared the standard value of 90% and there was no worry on the oil and fat outflow from a grease trap. The characteristics of sonication process were studied for free fatty acids degradation. The free saturated fatty acids are the most hard-degradable compounds of the fats, oils and greases (FOGs) in the grease trap. The influence of various parameters such as immersion level of an ultrasound probe in the liquid and bubbling of various gases (Ar, O2, air, O3) on the sonochemical and energy efficiency of the sonication process was investigated. The most effective degradation treatment method for saturated free fatty acids was the combination of sonication and low flow rate argon bubbling. Contribution to the Topical Issue "13th International Symposium on High Pressure Low Temperature Plasma Chemistry (Hakone XIII)", Edited by Nicolas Gherardi, Henryca Danuta Stryczewska and Yvan Ségui.

  13. Gradual surface degradation of restorative materials by acidic agents.

    PubMed

    Hengtrakool, Chanothai; Kukiattrakoon, Boonlert; Kedjarune-Leggat, Ureporn

    2011-01-01

    The aim of this study was to investigate the effect of acidic agents on surface roughness and characteristics of four restorative materials. Fifty-two discs were created from each restorative material: metal-reinforced glass ionomer cement (Ketac-S), resin-modified glass ionomer cement (Fuji II LC), resin composite (Filtek Z250), and amalgam (Valiant-PhD); each disc was 12 mm in diameter and 2.5 mm thick. The specimens were divided into four subgroups (n=13) and immersed for 168 hours in four storage media: deionized water (control); citrate buffer solution; green mango juice; and pineapple juice. Surface roughness measurements were performed with a profilometer, both before and after storage media immersion. Surface characteristics were examined using scanning electron microscopy (SEM). Statistical significance among each group was analyzed using two-way repeated ANOVA and Tukey's tests. Ketac-S demonstrated the highest roughness changes after immersion in acidic agents (p<0.05), followed by Fuji II LC. Valiant-PhD and Filtek Z250 illustrated some minor changes over 168 hours. The mango juice produced the greatest degradation effect of all materials tested (p<0.05). SEM photographs demonstrated gradual surface changes of all materials tested after immersions. Of the materials evaluated, amalgam and resin composite may be the most suitable for restorations for patients with tooth surface loss.

  14. Assessment of chloroethene degradation rates based on ratios of daughter/parent compounds in groundwater plumes

    NASA Astrophysics Data System (ADS)

    Höhener, Patrick

    2014-05-01

    Chlorinated solvent spills at industrial and urban sites create groundwater plumes where tetrachloro- and trichloroethene may degrade to their daughter compounds, dichloroethenes, vinyl chloride and ethane. The assessment of degradation and natural attenuation at such sites may be based on the analysis and inverse modelling of concentration data, on the calculation of mass fluxes in transsects, and/or on the analysis of stable isotope ratios in the ethenes. Relatively few work has investigated the possibility of using ratio of concentrations for gaining information on degradation rates. The use of ratios bears the advantage that dilution of a single sample with contaminant-free water does not matter. It will be shown that molar ratios of daughter to parent compounds measured along a plume streamline are a rapid and robust mean of determining whether degradation rates increase or decrease along the degradation chain, and allow furthermore a quantitation of the relative magnitude of degradation rates compared to the rate of the parent compound. Furthermore, ratios of concentration will become constant in zones where degradation is absent, and this allows to sketching the extension of actively degrading zones. The assessment is possible for pure sources and also for mixed sources. A quantification method is proposed in order to estimate first-order degradation rates in zones of constant degradation activity. This quantification method includes corrections that are needed due to longitudinal and transversal dispersivity. The method was tested on a number of real field sites from literature. At the majority of these sites, the first-order degradation rates were decreasing along the degradation chain from tetrachloroethene to vinyl chloride, meaning that the latter was often reaching important concentrations. This is bad news for site owners due to the increased toxicity of vinyl chloride compared to its parent compounds.

  15. [Photocatalytic degradation kinetics of perfluorooctanoic acid (PFOA) in TiO2 dispersion and its mechanism].

    PubMed

    Li, Ming-Jie; Yu, Ze-Bin; Chen, Ying; Wang, Li; Liu, Qing; Liu, Yu-Xin; He, Li-Li

    2014-07-01

    Decomposition of perfluorooctanoic acid (PFOA) is of prime importance since it is recognized as a persistent organic pollutant and is widespread in the environment. Heterogeneous photocatalytic decomposition of PFOA by TiO2 (P25) was investigated under 254 nm UV light. Experimental conditions including initial pH, TiO2 content and PFOA concentration, were varied to demonstrate their effects on the decomposition of PFOA. It was observed that the photocatalytic degradation kinetics of PFOA could be fitted to the quasi-first-order equation. The pH played a determinant role in the decomposition of PFOA and the presence of O2 increased the degradation rate. Optimal conditions for a complete removal were obtained using 1.5 g x L(-1) TiO2 at pH 3 in air atmosphere, with a rate constant of 0.420 6 h(-1). The contribution experiments of various reactive species produced during the photocatalysis were also investigated with the addition of different scavengers and it was found that photogenerated holes (h+) was the major reactive species which was responsible for 66.1% of the degradation rate, and the *OH was involved in PFOA degradation as well. In addition, the photocatalytic experiment with the addition of NaF indicated that the adsorption of PFOA was of primary importance for the photocatalytic decomposition. Perfluorocarboxylic acids (PFCAs) with shorter carbon chain length as intermediates and products were identified with UPLC-QTOF/MS, and a possible mechanism for PFOA decomposition was proposed.

  16. Malic acid or orthophosphoric acid-heat treatments for protecting sunflower (Helianthus annuus) meal proteins against ruminal degradation and increasing intestinal amino acid supply.

    PubMed

    Arroyo, J M; González, J; Ouarti, M; Silván, J M; Ruiz del Castillo, M L; de la Peña Moreno, F

    2013-02-01

    The protection of sunflower meal (SFM) proteins by treatments with solutions of malic acid (1 M) or orthophosphoric acid (0.67 M) and heat was studied in a 3 × 3 Latin-square design using three diets and three rumen and duodenum cannulated wethers. Acid solutions were applied to SFM at a rate of 400 ml/kg under continuous mixing. Subsequently, treated meals were dried in an oven at 150°C for 6 h. Diets (ingested at 75 g/kg BW0.75) were isoproteic and included 40% Italian ryegrass hay and 60% concentrate. The ratio of untreated to treated SFM in the concentrate was 100 : 0 in the control diet and around 40 : 60 in diets including acid-treated meals. The use of acid-treated meals did not alter either ruminal fermentation or composition of rumen contents and led to moderate reductions of the rumen outflow rates of untreated SFM particles, whereas it did not affect their comminution and mixing rate. In situ effective estimates of by-pass (BP) and its intestinal effective digestibility (IED) of dry matter (DM), CP and amino acids (AAs) were obtained considering both rates and correcting the particle microbial contamination in the rumen using 15N infusion techniques. Estimates of BP and IED decreased applying microbial correction, but these variations were low in agreement with the small contamination level. Protective treatments increased on average the BP of DM (48.5%) and CP (267%), mainly decreasing both the soluble fraction and the degradation rate but also increasing the undegradable fraction, which was higher using orthophosphoric acid. Protective treatments increased the IED of DM (108%) and CP, but this increase was lower using orthophosphoric acid (11.8%) than malic acid (20.7%). Concentrations of AA were similar among all meals, except for a reduction in lysine concentrations using malic acid (16.3%) or orthophosphoric acid (20.5%). Protective treatments also increased on average the BP of all AA, as well as the IED of most of them. Evidence of higher

  17. Variation of in situ rumen degradation of crude protein and amino acids and in vitro digestibility of undegraded feed protein in rapeseed meals.

    PubMed

    Steingass, H; Kneer, G; Wischer, G; Rodehutscord, M

    2013-07-01

    In this study, 10 samples of rapeseed meal (RSM) from 10 different oil plants in Germany were examined. In situ rumen degradation of CP was determined by incubation over 1, 2, 4, 8, 16, 32 and 72 h in duplicate per time point using three rumen fistulated dry cows. Degradation kinetics were estimated by an exponential model and effective CP degradation was calculated. Degradation was corrected for small particle loss as the difference between washing loss and water-soluble fraction. Amino acid analysis was carried out in the samples and in the residues after 8 and 16 h of incubation in situ and degradation of individual amino acids was calculated for these incubation times. In vitro pepsin-pancreatin digestibility of CP (IPD) was determined in the samples as well as in the 8 and 16 h residues. Effective CP degradation for a rumen outflow rate of 8%/h (ED8) averaged 54.3% with a considerable variation among samples ranging from 44.3% to 62.7%. A multiple regression equation containing acid detergent insoluble N, total glucosinolates and petroleum ether extract as independent variables predicted ED8 with satisfying accuracy (R 2 = 0.74; RSD = 6.4%). Degradation of amino acids was different from that of CP for most amino acids studied, especially after 8 h of incubation. Compared with CP, degradation of essential amino acids was predominantly lower while degradation of non-essential amino acids was higher in most cases. However, for lysine and methionine no distinct difference with CP degradation was found. Degradation of individual amino acids was predicted from CP degradation with high accuracy using linear regression equations. Average IPD of RSM was 79.8 ± 2.6%. IPD was lower in the incubation residues and decreased with longer incubation time and increasing rumen degradation, respectively.

  18. Bacterial populations and environmental factors controlling cellulose degradation in an acidic Sphagnum peat.

    PubMed

    Pankratov, Timofey A; Ivanova, Anastasia O; Dedysh, Svetlana N; Liesack, Werner

    2011-07-01

    Northern peatlands represent a major global carbon store harbouring approximately one-third of the global reserves of soil organic carbon. A large proportion of these peatlands consists of acidic Sphagnum-dominated ombrotrophic bogs, which are characterized by extremely low rates of plant debris decomposition. The degradation of cellulose, the major component of Sphagnum-derived litter, was monitored in long-term incubation experiments with acidic (pH 4.0) peat extracts. This process was almost undetectable at 10°C and occurred at low rates at 20°C, while it was significantly accelerated at both temperature regimes by the addition of available nitrogen. Cellulose breakdown was only partially inhibited in the presence of cycloheximide, suggesting that bacteria participated in this process. We aimed to identify these bacteria by a combination of molecular and cultivation approaches and to determine the factors that limit their activity in situ. The indigenous bacterial community in peat was dominated by Alphaproteobacteria and Acidobacteria. The addition of cellulose induced a clear shift in the community structure towards an increase in the relative abundance of the Bacteroidetes. Increasing temperature and nitrogen availability resulted in a selective development of bacteria phylogenetically related to Cytophaga hutchinsonii (94-95% 16S rRNA gene sequence similarity), which densely colonized microfibrils of cellulose. Among isolates obtained from this community only some subdivision 1 Acidobacteria were capable of degrading cellulose, albeit at a very slow rate. These Acidobacteria represent indigenous cellulolytic members of the microbial community in acidic peat and are easily out-competed by Cytophaga-like bacteria under conditions of increased nitrogen availability. Members of the phylum Firmicutes, known to be key players in cellulose degradation in neutral habitats, were not detected in the cellulolytic community enriched at low pH.

  19. Phytic acid degrading lactic acid bacteria in tef-injera fermentation.

    PubMed

    Fischer, Maren M; Egli, Ines M; Aeberli, Isabelle; Hurrell, Richard F; Meile, Leo

    2014-11-03

    Ethiopian injera, a soft pancake, baked from fermented batter, is preferentially prepared from tef (Eragrostis tef) flour. The phytic acid (PA) content of tef is high and is only partly degraded during the fermentation step. PA chelates with iron and zinc in the human digestive tract and strongly inhibits their absorption. With the aim to formulate a starter culture that would substantially degrade PA during injera preparation, we assessed the potential of microorganisms isolated from Ethiopian household-tef fermentations to degrade PA. Lactic acid bacteria (LAB) were found to be among the dominating microorganisms. Seventy-six isolates from thirteen different tef fermentations were analyzed for phytase activity and thirteen different isolates of seven different species were detected to be positive in a phytase screening assay. In 20-mL model tef fermentations, out of these thirteen isolates, the use of Lactobacillus (L.) buchneri strain MF58 and Pediococcus pentosaceus strain MF35 resulted in lowest PA contents in the fermented tef of 41% and 42%, respectively of its initial content. In comparison 59% of PA remained when spontaneously fermented. Full scale tef fermentation (0.6L) and injera production using L. buchneri MF58 as culture additive decreased PA in cooked injera from 1.05 to 0.34±0.02 g/100 g, representing a degradation of 68% compared to 42% in injera from non-inoculated traditional fermentation. The visual appearance of the pancakes was similar. The final molar ratios of PA to iron of 4 and to zinc of 12 achieved with L. buchneri MF58 were decreased by ca. 50% compared to the traditional fermentation. In conclusion, selected LAB strains in tef fermentations can degrade PA, with L. buchneri MF58 displaying the highest PA degrading potential. The 68% PA degradation achieved by the application of L. buchneri MF58 would be expected to improve human zinc absorption from tef-injera, but further PA degradation is probably necessary if iron absorption has to

  20. Microwave activated electrochemical degradation of 2,4-dichlorophenoxyacetic acid at boron-doped diamond electrode.

    PubMed

    Gao, Junxia; Zhao, Guohua; Shi, Wei; Li, Dongming

    2009-04-01

    A method for improving the oxidation ability of the electrode is proposed by using microwave activation in electrochemical oxidation. The electrochemical degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) with microwave radiation (MW-EC) was carried out in a continuous flow system under atmospheric pressure. In 3 h the removal of COD, ACE (average current efficiency) and Cl(-) concentration was 1.63, 2.25 and 1.67 times as that without microwave radiation, respectively. The high degradation ability was resulted from the more active centers at the electrode surface due to the microwave radiation. The decay kinetics of 2,4-D followed a pseudo first-order reaction. The rate constant was increased to 2.16x10(-4) s(-1) with the microwave radiation, while it was 8.52x10(-5) s(-1) with electrochemical treatment only (EC). Under both conditions, the main intermediates were identified and quantified by High Performance Liquid Chromatography (HPLC). The formation rate of intermediate products and further degradation rate were increased by about 50-120% with the microwave radiation. The activation of electrochemical oxidation by microwave was discussed from the diffusion process, adsorption and the temperature at boron-doped diamond (BDD) electrode.

  1. Degradation of herbicide 4-chlorophenoxyacetic acid by advanced electrochemical oxidation methods.

    PubMed

    Boye, Birame; Dieng, Momar M; Brillas, Enric

    2002-07-01

    The herbicide 4-chlorophenoxyacetic acid (4-CPA) has been degraded in aqueous medium by advanced electrochemical oxidation processes such as electro-Fenton and photoelectro-Fenton with UV light, using an undivided cell containing a Pt anode. In these environmentally clean methods, the main oxidant is the hydroxyl radical produced from Fenton's reaction between Fe2+ added to the medium and H2O2 electrogenerated from an 02-diffusion cathode. Solutions of a 4-CPA concentration <400 ppm within the pH range of 2.0-6.0 at 35 degrees C can be completely mineralized at low current by photoelectro-Fenton, while electro-Fenton leads to ca. 80% of mineralization. 4-CPA is much more slowly degraded by anodic oxidation in the absence and presence of electrogenerated H2O2. 4-Chlorophenol, 4-chlorocatechol, and hydroquinone are identified as aromatic intermediates by CG-MS and quantified by reverse-phase chromatography. Further oxidation of these chloroderivatives yields stable chloride ions. Generated carboxylic acids such as glycolic, glyoxylic, formic, malic, maleic, fumaric, and oxalic are followed by ion exclusion chromatography. The highest mineralization rate found for photoelectro-Fenton is accounted for by the fast photodecomposition of complexes of Fe3+ with such short-chain acids, mainly oxalic acid, under the action of UV light.

  2. Rates of assembly and degradation of bacterial ice nuclei.

    PubMed

    Watanabe, N M; Southworth, M W; Warren, G J; Wolber, P K

    1990-11-01

    The kinetics of ice-nucleus assembly from newly synthesized nucleation protein were observed following induction of nucleation gene expression in the heterologous host Escherichia coli. Assembly was significantly slower for the small proportion of ice nuclei active above -4.4 degrees C; this was consistent with the belief that these nuclei comprise the largest aggregates of nucleation protein. The kinetics of nucleus degradation were followed after inhibiting protein synthesis. Nucleation activity and protein showed a concerted decay, indicating that most of the functional ice nuclei are in equilibrium with a single cellular pool of nucleation protein. A minority of the ice nuclei decayed much more slowly than the majority; presumably their nucleation protein was distinct either by virtue of different structure or different subcellular compartmentalization, or because of its presence in a metabolically distinct subpopulation of cells.

  3. Polymer Film-Based Screening and Isolation of Polylactic Acid (PLA)-Degrading Microorganisms.

    PubMed

    Kim, Mi Yeon; Kim, Changman; Moon, Jungheun; Heo, Jinhee; Jung, Sokhee P; Kim, Jung Rae

    2017-02-28

    Polylactic acid (PLA) has been highlighted as an alternative renewable polymer for the replacement of petroleum-based plastic materials, and is considered to be biodegradable. On the other hand, the biodegradation of PLA by terminal degraders, such as microorganisms, requires a lengthy period in the natural environment, and its mechanism is not completely understood. PLA biodegradation studies have been conducted using mainly undefined mixed cultures, but only a few bacterial strains have been isolated and examined. For further characterization of PLA biodegradation, in this study, the PLA-degrading bacteria from digester sludge were isolated and identified using a polymer film-based screening method. The enrichment of sludge on PLA granules was conducted with the serial transference of a subculture into fresh media for 40 days, and the attached biofilm was inoculated on a PLA film on an agar plate. 3D optical microscopy showed that the isolates physically degraded the PLA film due to bacterial degradation. 16S rRNA gene sequencing identified the microbial colonies to be Pseudomonas sp. MYK1 and Bacillus sp. MYK2. The two isolates exhibited significantly higher specific gas production rates from PLA biodegradation compared with that of the initial sludge inoculum.

  4. Glycolic acid-catalyzed deamidation of asparagine residues in degrading PLGA matrices: a computational study.

    PubMed

    Manabe, Noriyoshi; Kirikoshi, Ryota; Takahashi, Ohgi

    2015-03-31

    Poly(lactic-co-glycolic acid) (PLGA) is a strong candidate for being a drug carrier in drug delivery systems because of its biocompatibility and biodegradability. However, in degrading PLGA matrices, the encapsulated peptide and protein drugs can undergo various degradation reactions, including deamidation at asparagine (Asn) residues to give a succinimide species, which may affect their potency and/or safety. Here, we show computationally that glycolic acid (GA) in its undissociated form, which can exist in high concentration in degrading PLGA matrices, can catalyze the succinimide formation from Asn residues by acting as a proton-transfer mediator. A two-step mechanism was studied by quantum-chemical calculations using Ace-Asn-Nme (Ace = acetyl, Nme = NHCH3) as a model compound. The first step is cyclization (intramolecular addition) to form a tetrahedral intermediate, and the second step is elimination of ammonia from the intermediate. Both steps involve an extensive bond reorganization mediated by a GA molecule, and the first step was predicted to be rate-determining. The present findings are expected to be useful in the design of more effective and safe PLGA devices.

  5. Suppression of muscle protein turnover and amino acid degradation by dietary protein deficiency

    NASA Technical Reports Server (NTRS)

    Tawa, N. E. Jr; Goldberg, A. L.

    1992-01-01

    To define the adaptations that conserve amino acids and muscle protein when dietary protein intake is inadequate, rats (60-70 g final wt) were fed a normal or protein-deficient (PD) diet (18 or 1% lactalbumin), and their muscles were studied in vitro. After 7 days on the PD diet, both protein degradation and synthesis fell 30-40% in skeletal muscles and atria. This fall in proteolysis did not result from reduced amino acid supply to the muscle and preceded any clear decrease in plasma amino acids. Oxidation of branched-chain amino acids, glutamine and alanine synthesis, and uptake of alpha-aminoisobutyrate also fell by 30-50% in muscles and adipose tissue of PD rats. After 1 day on the PD diet, muscle protein synthesis and amino acid uptake decreased by 25-40%, and after 3 days proteolysis and leucine oxidation fell 30-45%. Upon refeeding with the normal diet, protein synthesis also rose more rapidly (+30% by 1 day) than proteolysis, which increased significantly after 3 days (+60%). These different time courses suggest distinct endocrine signals for these responses. The high rate of protein synthesis and low rate of proteolysis during the first 3 days of refeeding a normal diet to PD rats contributes to the rapid weight gain ("catch-up growth") of such animals.

  6. Degradation of Amino Acids and Structure in Model Proteins and Bacteriophage MS2 by Chlorine, Bromine, and Ozone.

    PubMed

    Choe, Jong Kwon; Richards, David H; Wilson, Corey J; Mitch, William A

    2015-11-17

    Proteins are important targets of chemical disinfectants. To improve the understanding of disinfectant-protein reactions, this study characterized the disinfectant:protein molar ratios at which 50% degradation of oxidizable amino acids (i.e., Met, Tyr, Trp, His, Lys) and structure were observed during HOCl, HOBr, and O3 treatment of three well-characterized model proteins and bacteriophage MS2. A critical question is the extent to which the targeting of amino acids is driven by their disinfectant rate constants rather than their geometrical arrangement. Across the model proteins and bacteriophage MS2 (coat protein), differing widely in structure, methionine was preferentially targeted, forming predominantly methionine sulfoxide. This targeting concurs with its high disinfectant rate constants and supports its hypothesized role as a sacrificial antioxidant. Despite higher HOCl and HOBr rate constants with histidine and lysine than for tyrosine, tyrosine generally was degraded in preference to histidine, and to a lesser extent, lysine. These results concur with the prevalence of geometrical motifs featuring histidines or lysines near tyrosines, facilitating histidine and lysine regeneration upon Cl[+1] transfer from their chloramines to tyrosines. Lysine nitrile formation occurred at or above oxidant doses where 3,5-dihalotyrosine products began to degrade. For O3, which lacks a similar oxidant transfer pathway, histidine, tyrosine, and lysine degradation followed their relative O3 rate constants. Except for its low reactivity with lysine, the O3 doses required to degrade amino acids were as low as or lower than for HOCl or HOBr, indicating its oxidative efficiency. Loss of structure did not correlate with loss of particular amino acids, suggesting the need to characterize the oxidation of specific geometric motifs to understand structural degradation.

  7. Nicotinic acid inhibits glioma invasion by facilitating Snail1 degradation

    PubMed Central

    Li, Jiejing; Qu, Jiagui; Shi, Yu; Perfetto, Mark; Ping, Zhuxian; Christian, Laura; Niu, Hua; Mei, Shuting; Zhang, Qin; Yang, Xiangcai; Wei, Shuo

    2017-01-01

    Malignant glioma is a formidable disease that commonly leads to death, mainly due to the invasion of tumor cells into neighboring tissues. Therefore, inhibition of tumor cell invasion may provide an effective therapy for malignant glioma. Here we report that nicotinic acid (NA), an essential vitamin, inhibits glioma cell invasion in vitro and in vivo. Treatment of the U251 glioma cells with NA in vitro results in reduced invasion, which is accompanied by a loss of mesenchymal phenotype and an increase in cell-cell adhesion. At the molecular level, transcription of the adherens junction protein E-cadherin is upregulated, leading to accumulation of E-cadherin protein at the cell-cell boundary. This can be attributed to NA’s ability to facilitate the ubiquitination and degradation of Snail1, a transcription factor that represses E-cadherin expression. Similarly, NA transiently inhibits neural crest migration in Xenopus embryos in a Snail1-dependent manner, indicating that the mechanism of action for NA in cell migration is evolutionarily conserved. We further show that NA injection blocks the infiltration of tumor cells into the adjacent brain tissues and improves animal survival in a rat model of glioma. These results suggest that NA treatment may be developed into a potential therapy for malignant glioma. PMID:28256591

  8. Degradation of 2-methylbenzoic acid by Pseudomonas cepacia MB2

    SciTech Connect

    Higson, F.K.; Focht, D.D. )

    1992-01-01

    The authors report the isolation of Pseudomonas cepacia MB2, believed to be the first microorganism to utilize 2-methylbenzoic acid as the sole carbon source. Its growth range included all mono- and dimethylbenzoates (with the exception of 2,5- and 2,6-dimethylbenzoates) and 3-chloro-2-methylbenzoate (but not 4- or 5-chloro-2-methylbenzoate) but not chlorobenzoates lacking a methyl group. 2-Chlorobenzoate, 3-chlorobenzoate, and 2,3-, 2,4-, and 3,4-dichlorobenzoates inhibited growth of MB2 on 2-methylbenzoate as a result of cometabolism to the corresponding chlorinated catechols which blocked the key enzyme catechol 2,3-dioxygenase. A metapyrocatechase-negative mutant, MB2-G5, showed accumulation of dimethylcatechols from 2,3- and 3,4-dimethylbenzoates, and phenols were detected in resting-cell transformation extracts bearing the same substitution pattern as the original substrate, presumably following thermal degradation of the intermediate dihydrodiol. 2-Methylphenol was also found in extracts of the mutant cells with 2-methylbenzoate. These observations suggested a major route of methylbenzoate metabolism to be dioxygenation to a carboxy-hydrodiol which then forms a catechol derivative. In addition, the methyl group of 2-methylbenzoate was oxidized to isobenzofuranone (by cells of MB2-G5) and to phthalate (by cells of a separate mutant that could not utilize phthalate, MB2-D2). This pathway also generated a chlorinated isobenzofuranone from 3-chloro-2-methylbenzoate.

  9. Testing the ecotoxicology of vegetable versus mineral based lubricating oils: 1. Degradation rates using tropical marine microbes.

    PubMed

    Mercurio, Philip; Burns, Kathryn A; Negri, Andrew

    2004-05-01

    Vegetable-derived lubricants (VDL) might be more biodegradable than mineral-derived lubricants (MDL) due to the absence of high molecular weight aromatics, but this remains largely untested in tropical conditions. In this laboratory study, the degradation rates of 2-stroke, 4-stroke and hydraulic VDLs were compared with their MDL counterparts in the presence of mangrove and coral reef microbial communities. While MDLs were comprised largely of unresolved saturated and some aromatic hydrocarbons, their VDL counterparts contained, potentially more degradable, fatty acid methyl esters. Degradation of some VDL was observed by day 7, with the 2-stroke VDL markedly consumed by mangrove microorganisms and the hydraulic VDL degraded by both microorganism communities after this short period. All of the VDL groups were significantly more degraded than the comparable MDLs mineral oil lubricants over 14 days in the presence of either mangrove or coral reef microbial communities. In general the mangrove-sourced microorganisms more efficiently degraded the lubricants than reef-sourced microorganisms.

  10. Polysorbate 20 Degradation in Biopharmaceutical Formulations: Quantification of Free Fatty Acids, Characterization of Particulates, and Insights into the Degradation Mechanism.

    PubMed

    Tomlinson, Anthony; Demeule, Barthélemy; Lin, Baiwei; Yadav, Sandeep

    2015-11-02

    Polysorbate 20 (PS20), a commonly used surfactant in biopharmaceuticals, showed degradation upon long-term (∼18-36 months) storage of two monoclonal antibody (mAb, mAb-A, and mAb-B) drug products at 2-8 °C. The PS20 degradation resulted in the accumulation of free fatty acids (FFA), which ultimately precipitated to form particles upon long-term storage. This study documents the development, qualification, and application of a method for FFA quantification in soluble and insoluble fraction of protein formulation. The method was applied to the quantification of capric acid, lauric acid, myristic acid, palmitic/oleic acid, and stearic acid in placebo as well as active protein formulations on stability. Quantification of FFA in both the soluble and insoluble fraction of mAb-A and mAb-B provided a better mechanistic understanding of PS20 degradation and the dynamics of subsequent fatty acid particle formation. Additionally, the use of this method for monitoring and quantitation of the FFA on real time storage stability appears to aid in identifying batches with higher probability for particulate formation upon extended storage at 5 °C.

  11. Hydroxide based Benzyltrimethylammonium degradation: Quantification of rates and degradation technique development

    SciTech Connect

    Sturgeon, Matthew R.; Macomber, Clay S.; Engtrakul, Chaiwat; Long, Hai; Pivovar, Bryan S.

    2015-01-21

    Anion exchange membranes (AEMs) are of interest as hydroxide conducting polymer electrolytes in electrochemical devices like fuel cells and electrolyzers. AEMs require hydroxide stable covalently tetherable cations to ensure required conductivity. Benzyltrimethylammonium (BTMA) has been the covalently tetherable cation that has been most often employed in anion exchange membranes because it is reasonably basic, compact (limited number of atoms per charge), and easily/cheaply synthesized. Several reports exist that have investigated hydroxide stability of BTMA under specific conditions, but consistency within these reports and comparisons between them have not yet been made. While the hydroxide stability of BTMA has been believed to be a limitation for AEMs, this stability has not been thoroughly reported. In this paper, we have found that several methods reported have inherent flaws in their findings due to the difficulty of performing degradation experiments at high temperature and high pH. In order to address these shortcomings, we have developed a reliable, standardized method of determining cation degradation under conditions similar/relevant to those expected in electrochemical devices. The experimental method has been employed to determine BTMA stabilities at varying cation concentrations and elevated temperatures, and has resulted in improved experimental accuracy and reproducibility. Finally and most notably, these results have shown that BTMA is quite stable at 80°C (half-life of ~4 years), a significant increase in stability over what had been reported previously.

  12. Hydroxide based Benzyltrimethylammonium degradation: Quantification of rates and degradation technique development

    DOE PAGES

    Sturgeon, Matthew R.; Macomber, Clay S.; Engtrakul, Chaiwat; ...

    2015-01-21

    Anion exchange membranes (AEMs) are of interest as hydroxide conducting polymer electrolytes in electrochemical devices like fuel cells and electrolyzers. AEMs require hydroxide stable covalently tetherable cations to ensure required conductivity. Benzyltrimethylammonium (BTMA) has been the covalently tetherable cation that has been most often employed in anion exchange membranes because it is reasonably basic, compact (limited number of atoms per charge), and easily/cheaply synthesized. Several reports exist that have investigated hydroxide stability of BTMA under specific conditions, but consistency within these reports and comparisons between them have not yet been made. While the hydroxide stability of BTMA has been believedmore » to be a limitation for AEMs, this stability has not been thoroughly reported. In this paper, we have found that several methods reported have inherent flaws in their findings due to the difficulty of performing degradation experiments at high temperature and high pH. In order to address these shortcomings, we have developed a reliable, standardized method of determining cation degradation under conditions similar/relevant to those expected in electrochemical devices. The experimental method has been employed to determine BTMA stabilities at varying cation concentrations and elevated temperatures, and has resulted in improved experimental accuracy and reproducibility. Finally and most notably, these results have shown that BTMA is quite stable at 80°C (half-life of ~4 years), a significant increase in stability over what had been reported previously.« less

  13. Differential malic acid degradation by selected strains of Saccharomyces during alcoholic fermentation.

    PubMed

    Redzepovic, S; Orlic, S; Majdak, A; Kozina, B; Volschenk, H; Viljoen-Bloom, M

    2003-05-25

    To produce a high-quality wine, it is important to obtain a fine balance between the various chemical constituents, especially between the sugar and acid content. The latter is more difficult to achieve in wines that have high acidity due to excess malic acid, since wine yeast in general cannot effectively degrade malic acid during alcoholic fermentation. An indigenous Saccharomyces paradoxus strain RO88 was able to degrade 38% of the malic acid in Chardonnay must and produced a wine of good quality. In comparison, Schizosaccharomyces pombe strain F effectively removed 90% of the malic acid, but did not produce a good-quality wine. Although commercially promoted as a malic-acid-degrading wine yeast strain, only 18% of the malic acid was degraded by Saccharomyces cerevisiae Lalvin strain 71B. Preliminary studies on the transcriptional regulation of the malic enzyme gene from three Saccharomyces strains, i.e. S. paradoxus RO88, S. cerevisiae 71B and Saccharomyces bayanus EC1118, were undertaken to elucidate the differences in their ability to degrade malic acid. Expression of the malic enzyme gene from S. paradoxus RO88 and S. cerevisiae 71B increased towards the end of fermentation once glucose was depleted, whereas no increase in transcription was observed for S. bayanus EC1118 which was also unable to effectively degrade malic acid.

  14. Separation and recovery of nucleic acids with improved biological activity by acid-degradable polyacrylamide gel electrophoresis.

    PubMed

    Kim, Yoon Kyung; Kwon, Young Jik

    2010-05-01

    One of the fundamental challenges in studying biomacromolecules (e.g. nucleic acids and proteins) and their complexes in a biological system is isolating them in their structurally and functionally intact forms. Electrophoresis offers convenient and efficient separation and analysis of biomacromolecules but recovery of separated biomacromolecules is a significant challenge. In this study, DNAs of various sizes were separated by electrophoresis in an acid-degradable polyacrylamide gel. Almost 100% of the nucleic acids were recovered after the identified gel bands were hydrolyzed under a mildly acidic condition and purified using anion exchange resin. Further concentration by centrifugal filtration and a second purification using ion exchange column chromatography yielded 44-84% of DNA. The second conventional (non-degradable) gel electrophoresis confirmed that the nucleic acids recovered from acid-degradable gel bands preserved their electrophoretic properties through acidic gel hydrolysis, purification, and concentration processes. The plasmid DNA recovered from acid-degradable gel transfected cells significantly more efficiently than the starting plasmid DNA (i.e. improved biological activity via acid-degradable PAGE). Separation of other types of nucleic acids such as small interfering RNA using this convenient and efficient technique was also demonstrated.

  15. Experimental study on effect of anion surfactant on degradation rate of aldicarb in soil.

    PubMed

    Liu, Guangliang; Dai, Shugui; Qian, Yun; Gan, Quan

    2003-07-01

    Degradation kinetics of aldicarb [2-methyl-2-(methylthio) propionaldehyde O-(methyl carbamoyl) oxime] in surface and subsurface soil containing different levels of sodium dodecylbenzenesulfonate (SDBS) were determined to understand complex effect of SDBS on aldicarb degradation process. The results showed that degradation curves of aldicarb in soil can be described with first order kinetics formula and the degradation rate constant. k (d(-1)), in surface soil was larger than that in subsurface soil. SDBS can accelerate the degradation of aldicarb in soil and there was a good linear relationship between degradation rate constant and the logarithm of SDBS concentration. The possible reasons were that SDBS could change pH value of soil, have solubilization effect on aldicarb, and be used as carbon source of microorganisms. But SDBS had a larger promotion to the degradation of aldicarb in surface than in subsurface soil. When SDBS concentration was 1000 mg/kg of dried soil the first order degradation rate constant of aldicarb could be increased by 56.6 percent in surface soil and by 27.6 percent in subsurface soil, respectively.

  16. Effect of application rate on fumigant degradation in five agricultural soils.

    PubMed

    Qin, Ruijun; Gao, Suduan; Ajwa, Husein; Hanson, Bradley D

    2016-01-15

    Soil fumigation is an important pest management tool for many high value crops. To address the knowledge gap of how fumigant concentration in soil impacts dissipation, and thereby efficacy, this research determined the degradation characteristics of four fumigants as affected by application rate. Laboratory incubation experiments were conducted to determine degradation rates of 1,3-dichloropropene (both cis- and trans isomers), chloropicrin (CP), dimethyl disulfide (DMDS), and methyl iodide (MeI) in five agricultural soils. Fitted to pseudo first-order kinetics, the degradation rate constant (k) of CP, DMDS, and MeI decreased significantly as application rate increased while the 1,3-D isomers were the least affected by rate. Half-lives increased 12, 17, and 6-fold for CP, DMDS, and MeI, respectively, from the lowest to the highest application rate. At low application rates, the degradation rate of all fumigants in the Hueneme sandy loam soil was reduced by 50-95% in sterilized soil compared to the biologically active controls. However, this difference became much smaller or disappeared at high application rates indicating that biodegradation dominates at low concentrations but chemical degradation is more important at high concentrations. When co-applied, CP degradation was enhanced with biodegradation remained above 50%, while 1,3-D degradation was either reduced or not changed. Among the fumigants tested, the relative importance of biodegradation was DMDS>CP>MeI>1,3-D. These results are useful for determining effective fumigation rates and for informing regulatory decisions on emission controls under different fumigation scenarios.

  17. Investigation of sorbic acid volatile degradation products in pharmaceutical formulations using static headspace gas chromatography.

    PubMed

    Yarramraju, Sitaramaraju; Akurathi, Vamsidhar; Wolfs, Kris; Van Schepdael, Ann; Hoogmartens, Jos; Adams, Erwin

    2007-06-28

    An analytical method that allows simultaneous analysis of sorbic acid and its degradation products was developed using static headspace gas chromatography (HS-GC). AT-Aquawax-DA, the capillary column used, showed good selectivity and separation towards sorbic acid and its degradation products. Sorbic acid degradation was investigated in both acidic and aqueous media at room and elevated temperatures. In total 12 sorbic acid degradation products were found, 8 of which could be characterized. The method was investigated for its accuracy towards estimation of degradation products. Using the HS-GC method different batches of pharmaceutical preparations such as cold cream, cetomacrogol cream and vaseline were investigated for sorbic acid degradation products which were estimated by applying the standard addition method. Acetaldehyde was found to be the major degradation product. The other identified degradation products were: acetone; 2-methylfuran; crotonaldehyde; alfa-angelicalactone; 2-acetyl, 5-methylfuran; toluene and 2,5-dimethylfuran. Both mass spectrometeric (MS) and flame ionization detection (FID) were used. The qualitative investigation was done on HS-GC-MS and the quantitative work on HS-GC-FID.

  18. Ultraviolet-induced oxidation of ascorbic acid in a model juice system: identification of degradation products.

    PubMed

    Tikekar, Rohan V; Anantheswaran, Ramaswamy C; Elias, Ryan J; LaBorde, Luke F

    2011-08-10

    Degradation products of ultraviolet (UV-C, 254 nm) treated ascorbic acid (AA) are reported. Analysis by high-performance liquid chromatography-mass spectroscopy (HPLC-MS) conducted in a 0.5% malic acid model juice system (pH 3.3) demonstrated increased degradation of AA above untreated controls with concomitant increases in dehydroascorbic acid (DHA) and 2,3-diketogulonic acid (DKGA) levels. Electron spin resonance (ESR) spectroscopy studies, conducted in phosphate buffer (pH 7.0) to increase detection sensitivity, demonstrated that ascorbyl radical (AA•) formation occurs simultaneously with AA degradation. Consistent with a previous study in which UV treatments were shown to accelerate dark storage degradation, AA• radicals continued to form for up to 200 min after an initial UV treatment. Results from this study suggest that the mechanism for UV-induced degradation is the same as the general mechanism for metal-catalyzed oxidation of AA in juice.

  19. Electrochemical destruction of trans-cinnamic acid by advanced oxidation processes: kinetics, mineralization, and degradation route.

    PubMed

    Flores, Nelly; Thiam, Abdoulaye; Rodríguez, Rosa María; Centellas, Francesc; Cabot, Pere Lluís; Garrido, José Antonio; Brillas, Enric; Sirés, Ignasi

    2016-01-14

    Acidic solutions of trans-cinnamic acid at pH 3.0 have been comparatively treated by anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), and photoelectro-Fenton (PEF). The electrolytic experiments were carried out with a boron-doped diamond (BDD)/air-diffusion cell. The substrate was very slowly abated by AO-H2O2 because of its low reaction rate with oxidizing (•)OH produced from water discharge at the BDD anode. In contrast, its removal was very rapid and at similar rate by EF and PEF due to the additional oxidation by (•)OH in the bulk, formed from Fenton's reaction between cathodically generated H2O2 and added Fe(2+). The AO-H2O2 treatment yielded the lowest mineralization. The EF process led to persistent final products like Fe(III) complexes, which were quickly photolyzed upon UVA irradiation in PEF to give an almost total mineralization with 98 % total organic carbon removal. The effect of current density and substrate concentration on all the mineralization processes was examined. Gas chromatography-mass spectrometry (GC-MS) analysis of electrolyzed solutions allowed identifying five primary aromatics and one heteroaromatic molecule, whereas final carboxylic acids like fumaric, acetic, and oxalic were quantified by ion exclusion high-performance liquid chromatography (HPLC). From all the products detected, a degradation route for trans-cinnamic acid is proposed.

  20. Microbiological degradation of bile acids. Nitrogenous hexahydroindane derivatives formed from cholic acid by Streptomyces rubescens.

    PubMed Central

    Hayakawa, S; Hashimoto, S; Onaka, T

    1976-01-01

    The metabolism of cholic acid (I) by Streptomyces rubescens was investigated. This organism effected ring A cleavage, side-chain shortening and amide bond formation and gave the following metabolites: (4R)-4-[4alpha-(2-carboxyethyl)-3aalpha-hexahydro-7abeta-methyl-5-oxoindan-1 beta-yl]valeric acid (IIa) and its mono-amide (valeramide) (IIb); and 2,3,4,6, 6abeta,7,8,9,9aalpha,9bbeta-decahydro-6abeta-methyl-1H-cyclopenta[f]quinoline-3,7-dione(IIIe)and its homologues with the beta-oriented side chains, valeric acid, valeramide, butanone and propionic acid, in the place of the oxo group at C-7, i.e.compounds (IIIa), (IIIb), (IIIc) and (IIId) respectively. All the nitrogenous metabolites were new compounds, and their structures were established by partial synthesis except for the metabolite (IIIc). The mechanism of formation of these metabolites is considered. A degradative pathway of cholic acid (I) into the metabolites is also tentatively proposed. PMID:1016253

  1. Effects of dry method esterification of starch on the degradation characteristics of starch/polylactic acid composites.

    PubMed

    Zuo, Ying Feng; Gu, Jiyou; Qiao, Zhibang; Tan, Haiyan; Cao, Jun; Zhang, Yanhua

    2015-01-01

    Maleic anhydride esterified corn starch was prepared by dry method. Esterified starch/polylactic acid (PLA) biodegradable composite was produced via melt extrusion method with blending maleic anhydride esterified corn starch and PLA. The influence of the dry method esterification of starch on the degradation characteristics of starch/PLA composites was investigated by the natural aging degradation which was soil burial method. Test results of mass loss rate showed that the first 30 days of degradation was mainly starch degradation, and the degradation rate of esterified starch/PLA (ES/PLA) was slower than that of native starch/PLA (NS/PLA). Therefore, the damage degree of ES/PLA on the surface and inside was smaller than that of NS/PLA, and the infrared absorption peak intensities of C-O, C=O and C-H were stronger than that of NS/PLA. With the increasing time of soil burial degradation, the damage degree of NS/PLA and ES/PLA on the exterior and interior were gradually increased, whereas the infrared absorption peak intensities of C-O, C=O and C-H were gradually decreased. The XRD diffraction peak intensity of PLA in composites showed an increased trend at first which was then followed by a decreased one along with the increasing time of soil burial degradation, indicating that the degradation of amorphous regions of PLA was earlier than its crystalline regions. When the soil burial time was the same, the diffraction peak intensity of PLA in ES/PLA was stronger than that of NS/PLA. If the degradation time was the same, T0, Ti and residual rate of thermal decomposition of NS/PLA were larger than those of ES/PLA. The tensile strength and bending strength of composites were decreased gradually with soil burial time increasing. Both the tensile strength and bending strength of ES/PLA were stronger than those of NS/PLA.

  2. Mechanism and kinetics of electrochemical degradation of uric acid using conductive-diamond anodes.

    PubMed

    Dbira, Sondos; Bensalah, Nasr; Bedoui, Ahmed

    2016-12-01

    Uric acid (UA) is one of the principal effluents of urine wastewaters, widely used in agriculture as fertilizer, which is potentially dangerous and biorefractory. Hence, the degradation of UA (2,6,8-trihydroxy purine) in aqueous solution of pH 3.0 has been studied by conductive-diamond electrochemical oxidation. Hydroxyl radicals formed from water oxidation at the surface of boron-doped diamond anodes were the main oxidizing agents. Effects of current density and supporting electrolyte on the degradation rate and process efficiency are assessed. Results show that the increase of current density from 20 to 60 mA cm(-2) leads to a decrease in the efficiency of the electrochemical process. In addition, the best degradation occurred in the presence of NaCl as conductive electrolyte. Interestingly, an almost total mineralization of 50 ppm UA was obtained when anodic oxidation was performed at low current densities (20 mA cm(-2)) and in the presence of NaCl. This result confirmed that the electrolysis using diamond anodes is a very interesting technology for the treatment of UA. The identification of UA transformation products was performed by high-performance liquid chromatography (HPLC). HPLC analysis of treated solutions revealed that oxalic acid and urea were the two intermediates found. Oxalic acid was the most persistent product. Based on detected intermediates and bibliographic research, a mechanism of UA mineralization by anodic oxidation has been proposed. Ionic chromatography analysis confirmed the release of [Formula: see text] and [Formula: see text] ions during UA mineralization.

  3. Abiotic degradation rates for carbon tetrachloride and chloroform: Final report.

    SciTech Connect

    Amonette, James E.; Jeffers, Peter M.; Qafoku, Odeta; Russell, Colleen K.; Humphrys, Daniel R.; Wietsma, Thomas W.; Truex, Michael J.

    2012-12-01

    This report documents the objectives, technical approach, and progress made through FY 2012 on a project initiated in FY 2006 to help address uncertainties related to the rates of hydrolysis in groundwater for carbon tetrachloride (CT) and chloroform (CF). The project also sought to explore the possible effects of contact with minerals and sediment (i.e., heterogeneous hydrolysis) on these rates. We conducted 114 hydrolysis rate experiments in sealed vessels across a temperature range of 20-93 °C for periods as long as 6 years, and used the Arrhenius equation to estimate activation energies and calculate half-lives for typical Hanford groundwater conditions (temperature of 16 °C and pH of 7.75). We calculated a half-life of 630 years for hydrolysis for CT under these conditions and found that CT hydrolysis was unaffected by contact with sterilized, oxidized minerals or Hanford sediment within the sensitivity of our experiments. In contrast to CT, hydrolysis of CF was generally slower and very sensitive to pH due to the presence of both neutral and base-catalyzed hydrolysis pathways. We calculated a half-life of 3400 years for hydrolysis of CF in homogeneous solution at 16 °C and pH 7.75. Experiments in suspensions of Hanford sediment or smectite, the dominant clay mineral in Hanford sediment, equilibrated to an initial pH of 7.2, yielded calculated half-lives of 1700 years and 190 years, respectively, at 16 °C. Experiments with three other mineral phases at the same pH (muscovite mica, albite feldspar, and kaolinite) showed no change from the homogeneous solution results (i.e., a half-life of 3400 years). The strong influence of Hanford sediment on CF hydrolysis was attributed to the presence of smectite and its ability to adsorb protons, thereby buffering the solution pH at a higher level than would otherwise occur. The project also determined liquid-vapor partition coefficients for CT under the temperatures and pressures encountered in the sealed vessels that

  4. Effects of ultraviolet light (315 nm), temperature and relative humidity on the degradation of polylactic acid plastic films.

    PubMed

    Copinet, Alain; Bertrand, Celine; Govindin, Stephanie; Coma, Veronique; Couturier, Yves

    2004-05-01

    The influence of temperature (30, 45 and 60 degrees C) and relative humidity (RH) (30%, 50% and 100%) on the degradation of poly(l-lactic acid) (PLA) films were studied. In addition, the effects of ultraviolet (UV) light (315 nm) on the degradation of PLA films were also analyzed. Various analytical techniques were applied to observe changes in the properties of PLA polymer films. FTIR spectroscopy was used as semi-quantitative method to get information about the chemistry of the degradative process. The degradation rate of PLA was enhanced by increasing temperature and RH, factors responsible for a faster reduction of the weight-average molecular weight (M(W)), of the glass transition temperature (Tg) and of the percentage of elongation at break. Moreover, UV treatment accelerated these phenomena.

  5. Main chain acid-degradable polymers for the delivery of bioactive materials

    DOEpatents

    Frechet, Jean M. J. [Oakland, CA; Standley, Stephany M [Evanston, IL; Jain, Rachna [Milpitas, CA; Lee, Cameron C [Cambridge, MA

    2012-03-20

    Novel main chain acid degradable polymer backbones and drug delivery systems comprised of materials capable of delivering bioactive materials to cells for use as vaccines or other therapeutic agents are described. The polymers are synthesized using monomers that contain acid-degradable linkages cleavable under mild acidic conditions. The main chain of the resulting polymers readily degrade into many small molecules at low pH, but remain relatively stable and intact at physiological pH. The new materials have the common characteristic of being able to degrade by acid hydrolysis under conditions commonly found within the endosomal or lysosomal compartments of cells thereby releasing their payload within the cell. The materials can also be used for the delivery of therapeutics to the acidic regions of tumors and other sites of inflammation.

  6. Introducing saccharic acid as an efficient iron chelate to enhance photo-Fenton degradation of organic contaminants.

    PubMed

    Subramanian, Gokulakrishnan; Madras, Giridhar

    2016-11-01

    The identification of iron chelates that can enhance photo-Fenton degradation is of great interest in the field of advanced oxidation process. Saccharic acid (SA) is a polyhydroxy carboxylic acid and completely non-toxic. Importantly, it can effectively bind Fe(III) as well as induce photoreduction of Fe(III). Despite having these interesting properties, the effect of SA on photo-Fenton degradation has not been studied. Herein, we demonstrate the first assessment of SA as an iron chelate in photo-Fenton process using methylene blue (MB) as a model organic contaminant. Our results demonstrate that SA has the ability to (i) enhance the photo-Fenton degradation of MB by about 11 times at pH 4.5 (ii) intensify photochemical reduction of Fe(III) to Fe(II) by about 17 times and (iii) accelerate the rate of consumption of H2O2 in photo-Fenton process by about 5 times (iv) increase the TOC reduction by about 2 times and (v) improve the photo-Fenton degradation of MB in the presence of a variety of common inorganic ions and organic matter. The influential properties of SA on photo-Fenton degradation is attributed to the efficient photochemical reduction of Fe(III) via LMCT (ligand to metal charge transfer reaction) to Fe(II), which then activated H2O2 to generate OH and accelerated photo-Fenton degradation efficiency. Moreover, the effect of operational parameters such as oxidant: contaminant (H2O2: MB) ratio, catalyst: contaminant (Fe(III)SA: MB) ratio, Fe(III): SA stoichiometry and pH on the degradation of MB by photo-Fenton in the presence of SA is demonstrated. Importantly, SA assisted photo-Fenton caused effective degradation of MB and 4-Chlorophenol under natural sunlight irradiation in natural water matrix. The findings strongly support SA as a deserving iron chelate to enhance photo-Fenton degradation.

  7. Inherently antioxidant and antimicrobial tannic acid release from poly(tannic acid) nanoparticles with controllable degradability.

    PubMed

    Sahiner, Nurettin; Sagbas, Selin; Aktas, Nahit; Silan, Coskun

    2016-06-01

    From a natural polyphenol, Tannic acid (TA), poly(TA) nanoparticles were readily prepared using a single step approach with three different biocompatible crosslinkers; trimethylolpropane triglycidyl ether (TMPGDE), poly(ethylene glycol) diglycidyl ether (PEGGE), and trisodium trimetaphosphate (STMP). P(TA) particles were obtained with controllable diameters between 400 to 800nm with -25mV surface charge. The effect of synthesis conditions, such as the emulsion medium, pH values of TA solution, and the type of crosslinker, on the shape, size, dispersity, yield, and degradability of poly(Tannic Acid) (p(TA)) nanoparticles was systematically investigated. The hydrolytic degradation amount in physiological pH conditions of 5.4, 7.4, and 9.0 at 37.5°C were found to be in the order TMPGDEdegradation amounts of TA from p(TA) nanoparticles can be controlled by the appropriate choice of crosslinker, and the pH of releasing media. The highest TA release, 600mg/g, was obtained for TMPGDE-crosslinked p(TA) particles in intestinal pH conditions (pH 9) over 3 days; whereas, a slow and linear TA release profile over almost 30 days was obtained by using PEGGE-crosslinked p(TA) in body fluid pH conditions (pH 7.4). The total phenol content of p(TA) particles was calculated as 70±1μgmL(-1) for 170μgmL(-1) p(TA), and the trolox equivalent antioxidant capacity was found to be 2027±104mM trolox equivalent g(-1). Moreover, p(TA) nanoparticles demonstrated strong antimicrobial effects against common bacterial strains. More interestingly, with a higher concentration of p(TA) particles, higher blood clotting indices were obtained.

  8. Calcite crystal growth rate inhibition by polycarboxylic acids

    USGS Publications Warehouse

    Reddy, M.M.; Hoch, A.R.

    2001-01-01

    Calcite crystal growth rates measured in the presence of several polycarboxyclic acids show that tetrahydrofurantetracarboxylic acid (THFTCA) and cyclopentanetetracarboxylic acid (CPTCA) are effective growth rate inhibitors at low solution concentrations (0.01 to 1 mg/L). In contrast, linear polycarbocylic acids (citric acid and tricarballylic acid) had no inhibiting effect on calcite growth rates at concentrations up to 10 mg/L. Calcite crystal growth rate inhibition by cyclic polycarboxyclic acids appears to involve blockage of crystal growth sites on the mineral surface by several carboxylate groups. Growth morphology varied for growth in the absence and in the presence of both THFTCA and CPTCA. More effective growth rate reduction by CPTCA relative to THFTCA suggests that inhibitor carboxylate stereochemical orientation controls calcite surface interaction with carboxylate inhibitors. ?? 20O1 Academic Press.

  9. Studies on the sonic degradation of deoxyribonucleic acid.

    PubMed

    FREIFELDER, D; DAVISON, P F

    1962-05-01

    T7 DNA was partially degraded by x-rays, DNAase, and sonic irradiation. The molecular weight distributions were calculated from sedimentation velocity studies on the resulting preparations. Comparison with the theoretical curve derived by Montroll and Simha showed that the first two degradative methods act grossly at random, whereas sonication is a non-random process resulting in the preferential halving of the DNA molecules in solution.

  10. Studies on the Sonic Degradation of Deoxyribonucleic Acid

    PubMed Central

    Freifelder, David; Davison, Peter F.

    1962-01-01

    T7 DNA was partially degraded by x-rays, DNAase, and sonic irradiation. The molecular weight distributions were calculated from sedimentation velocity studies on the resulting preparations. Comparison with the theoretical curve derived by Montroll and Simha showed that the first two degradative methods act grossly at random, whereas sonication is a non-random process resulting in the preferential halving of the DNA molecules in solution. PMID:13894963

  11. Disentangling the interactions between photochemical and bacterial degradation of dissolved organic matter: amino acids play a central role.

    PubMed

    Amado, André M; Cotner, James B; Cory, Rose M; Edhlund, Betsy L; McNeill, Kristopher

    2015-04-01

    Photochemical and bacterial degradation are important pathways to carbon mineralization and can be coupled in dissolved organic matter (DOM) decomposition. However, details of several mechanisms of the coupled photochemical and biological processing of DOM remain too poorly understood to achieve accurate predictions of the impact of these processes on DOM fate and reactivity. The aim of this study was to evaluate how photochemical degradation of amino acids affects bacterial metabolism and whether or not photochemical degradation of DOM competes for amino acids with biological processes. We examined the interactions between photochemical and bacterial degradation dynamics using a mixture of 18 amino acids and examined their dynamics and turnover rates within a larger pool of allochthonous or autochthonous DOM. We observed that photochemical exposure of DOM containing amino acids led to delayed biomass production (even though the final biomass did not differ), most likely due to a need for upregulation of biosynthetic pathways for amino acids that were damaged by photochemically produced reactive oxygen species (ROS). This response was most pronounced in bacterial communities where the abundance of photosensitive amino acids was highest (amended treatments and autochthonous DOM) and least pronounced when the abundance of these amino acids was low (unamended and allochthonous DOM), likely because these bacteria already had these biosynthetic pathways functioning. We observed both a cost and benefit associated with photochemical exposure of DOM. We observed a cost associated with photochemically produced ROS that partially degrade key amino acids and a benefit associated with an increase in the availability of other compounds in the DOM. Bacteria growing on DOM sources that are low in labile amino acids, such as those in terrestrially influenced environments, experience more of the benefits associated with photochemical exposure, whereas bacteria growing in more amino

  12. Removal of nalidixic acid and its degradation products by an integrated MBR-ozonation system.

    PubMed

    Pollice, A; Laera, G; Cassano, D; Diomede, S; Pinto, A; Lopez, A; Mascolo, G

    2012-02-15

    Chemical-biological degradation of a widely spread antibacterial (nalidixic acid) was successfully obtained by an integrated membrane bioreactor (MBR)-ozonation process. The composition of the treated solution simulated the wastewater from the production of the target pharmaceutical, featuring high salinity and a relevant concentration of sodium acetate. Aim of treatment integration was to exploit the synergistic effects of chemical oxidation and bioprocesses, by adopting the latter to remove most of the COD and the ozonation biodegradable products. Integration was achieved by placing ozonation in the recirculation stream of the bioreactor effluent. The recirculation flow rate was three-fold the MBR feed, and the performance of the integrated system was compared to the standard polishing configuration (single ozonation step after the MBR). Results showed that the introduction of the ozonation step did not cause relevant drawbacks to both biological and filtration processes. nalidixic acid passed undegraded through the MBR and was completely removed in the ozonation step. Complete degradation of most of the detected ozonation products was better achieved with the integrated MBR-ozonation process than using the sequential treatment configuration, i.e. ozone polishing after MBR, given the same ozone dosage.

  13. LC/MS/MS identification of some folic acid degradation products after E-beam irradiation

    NASA Astrophysics Data System (ADS)

    Araújo, M. M.; Marchioni, E.; Zhao, M.; Kuntz, F.; Di Pascoli, T.; Villavicencio, A. L. C. H.; Bergaentzle, M.

    2012-08-01

    Folates belong to the B vitamin group based on the parental compound folic acid (FA). They are involved in important biochemical processes like DNA synthesis and repair. FA is composed of a pteridine ring, p-aminobenzoic acid and glutamate moieties. The human metabolism is not able to synthesize folates and therefore obtain them from diet. FA, a synthetic vitamin, is used as a food fortificant because of its low price, relative stability and increased bioavailability compared to natural folate forms. FA is known to be a sensitive compound easily degradable in aqueous solution by ultraviolet and visible light towards various by-products. Irradiation is a process for preservation of foods that uses accelerated electrons, gamma rays or X-rays. Irradiation is proposed for the treatment of various food products, eliminating or reducing pathogens and insects, increasing the storage time and replacing chemical fumigants. This study concerns the identification of degradation products of FA after E-beam irradiation. FA aqueous solutions were irradiated with a Van de Graaff electrons beam accelerator (2 MeV, 100 μA current, 20 cm scan width, dose rate about 2 kGy/s). Applied doses were between 0 (control) and 10.0 kGy. Absorbed doses were monitored with FWT 60.00 radiochromic dosimeters.

  14. Interfacial regulation of acid ceramidase activity. Stimulation of ceramide degradation by lysosomal lipids and sphingolipid activator proteins.

    PubMed

    Linke, T; Wilkening, G; Sadeghlar, F; Mozcall, H; Bernardo, K; Schuchman, E; Sandhoff, K

    2001-02-23

    The lysosomal degradation of ceramide is catalyzed by acid ceramidase and requires sphingolipid activator proteins (SAP) as cofactors in vivo. The aim of this study was to investigate how ceramide is hydrolyzed by acid ceramidase at the water-membrane interface in the presence of sphingolipid activator proteins in a liposomal assay system. The degradation of membrane-bound ceramide was significantly increased both in the absence and presence of SAP-D when anionic lysosomal phospholipids such as bis(monoacylglycero)phosphate, phosphatidylinositol, and dolichol phosphate were incorporated into substrate-bearing liposomes. Higher ceramide degradation rates were observed in vesicles with increased membrane curvature. Dilution assays indicated that acid ceramidase remained bound to the liposomal surface during catalysis. Not only SAP-D, but also SAP-C and SAP-A, were found to be stimulators of ceramide hydrolysis in the presence of anionic phospholipids. This finding was confirmed by cell culture studies, in which SAP-A, -C, and -D reduced the amount of ceramide storage observed in fibroblasts of a patient suffering from prosaposin deficiency. Strong protein-lipid interactions were observed for both SAP-D and acid ceramidase in surface plasmon resonance experiments. Maximum binding of SAP-D and acid ceramidase to lipid bilayers occurred at pH 4.0. Our results demonstrate that anionic, lysosomal lipids are required for efficient hydrolysis of ceramide by acid ceramidase.

  15. Malonic acid suppresses mucin-type O-glycan degradation during hydrazine treatment of glycoproteins.

    PubMed

    Goso, Yukinobu

    2016-03-01

    Hydrazine treatment is frequently used for releasing mucin-type O-glycans (O-glycans) from glycoproteins because the method provides O-glycans that retain a reducible GalNAc at their reducing end, which is available for fluorescent labeling. However, many O-glycans are degraded by "peeling" during this treatment. In the current study, it was found that malonic acid suppressed O-glycan degradation during hydrazine treatment of bovine fetuin or porcine gastric mucin in both the gas and liquid phases. This is paradoxical because the release of O-glycans from glycoproteins occurs under alkaline conditions. However, malonic acid seems to prevent the degradation through its acidic property given that other weak acids also prevented the degradation. Accordingly, disodium malonate did not suppress O-glycan degradation. Application of this method to rat gastric mucin demonstrated that the majority of the major O-glycans obtained in the presence of malonic acid were intact, whereas those obtained in the absence of malonic acid were degraded. These results suggest that hydrazine treatment in the presence of malonic acid would allow glycomic analysis of native mucin glycoproteins.

  16. Preparation of salvianolic acid A by the degradation reaction of salvianolic acid B in subcritical water integrated with pH-zone-refining counter-current chromatography.

    PubMed

    Li, Huaizhi; Cheng, Yan; Dong, Hongjing; Wang, Xiao; Li, Jia; Gao, Qianshan

    2016-10-14

    Salvianolic acid A is the major bioactive compound in Danshen, however, due to the chemical instability and low content in Danshen, it is difficult to extract amount of salvianolic acid A. Therefore, this study was to establish an effective strategy for obtaining adequate amount of salvianolic acid A, subcritical water extraction was used to degrade salvianolic acid B and prepare salvianolic acid A. Different reaction conditions including temperature, time, concentration and pH value in subcritical water were investigated. Under 40mg/mL of reactant concentration, 180°C of temperature, 4.0 of pH value and 60min of reaction time, the highest yield rate of salvianolic acid A reached 34.86%. Then, the degradation products were successfully separated by pH-zone-refining counter-current chromatography with the solvent system Pet-EtAc-n-BuOH-H2O (2:3:1:9, v/v), where 10mM TFA was added in stationary phase and 10mM NH3·H2O in mobile phase. As a result, a total of 227.3mg of salvianolic acid A at 98.2% purity, 38.9mg of danshensu at 99.3% purity, 9.5mg of salvianolic acid D at 92.7% purity, and 32.8mg of protocatechuic aldehyde at 93.1% purity were obtained from 1.2g degradation products of salvianolic acid B by one-step purification. The results demonstrated that the combinative application of subcritical water and pH-zone-refining counter-current chromatography is a potential technique for the preparative separation of salvianolic acid A from salvianolic acid B.

  17. Mechanisms of photocatalytical degradation of monomethylarsonic and dimethylarsinic acids using nanocrystalline titanium dioxide.

    PubMed

    Xu, Zhonghou; Jing, Chuanyong; Li, Fasheng; Meng, Xiaoguang

    2008-04-01

    Photodegradation mechanisms of monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) with nanocrystalline titanium dioxide under UV irradiation were investigated. In the presence of UV irradiation and 0.02 g/L TiO2, 93% MMA (initial concentration is 10 mg-As/L) was transformed into inorganic arsenate, [As(V)], after 72 h of a batch reaction. The mineralization of DMA to As(V) occurred in two steps with MMA as an intermediate product. The photodegradation rate of MMA and DMA could be described using first-order kinetics, where the apparent rate constant is 0.033/h and 0.013/h for MMA and DMA, respectively. Radical scavengers, including superoxide dimutase (SOD), sodium bicarbonate, tert-butanol, and sodium azide, were used to study the photodegradation mechanisms of MMA and DMA. The results showed that hydroxyl radicals (HO*) was the primary reactive oxygen species for the photodegradation of MMA and DMA. The methyl groups in MMA and DMAweretransformed into organic carbon, including formic acid and possibly methanol, also through photochemical reactions. The results showed that nanocrystalline TiO2 can be used for the photocatalytical degradation of MMA and DMA and subsequent removal of the converted As(V), since the high adsorption capacity of the material for inorganic arsenic species has been demonstrated in previous studies.

  18. Degradation of substituted naphthalenesulfonic acids by Sphingomonas xenophaga BN6.

    PubMed

    Stolz, A

    1999-10-01

    Sphingomonas xenophaga BN6 was isolated from the river Elbe as a member of a multispecies bacterial culture which mineralized 6-aminonaphthalene-2-sulfonate. Pure cultures of strain BN6 converted a wide range of amino- and hydroxynaphthalene-2-sulfonates via a catabolic pathway similar to that described for the metabolism of naphthalene to salicylate by Pseudomonas putida NAH7 or Pseudomonas sp NCIB 9816. In contrast to the naphthalene-degrading pseudomonads, S. xenophaga BN6 only partially degraded the naphthalenesulfonates and excreted the resulting amino- and hydroxysalicylates in almost stoichiometric amounts. Enzymes that take part in the degradative pathway of the naphthalenesulfonates by strain BN6 were purified, characterized and compared with the isofunctional enzymes from the naphthalene-degrading pseudomonads. According to the enzyme structures and the catalytic constants, no fundamental differences were found between the 1,2-dihydroxynaphthalene dioxygenase or the 2'-hydroxybenzalpyruvate aldolase from strain BN6 and the isofunctional enzymes from the naphthalene-degrading pseudomonads. The limited available sequence information about the enzymes from strain BN6 suggests that they show about 40-60% sequence identity to the isofunctional enzymes from the pseudomonads. In addition to the gene for the 1,2-dihydroxynaphthalene dioxygenase, the genes for two other extradiol dioxygenases were cloned and sequenced from strain BN6 and the corresponding gene products were studied. S. xenophaga BN6 has also been used as a model organism to study the mechanism of the non-specific reduction of azo dyes under anaerobic conditions and to establish combined anaerobic/aerobic treatment systems for the degradation of sulfonated azo dyes. Furthermore, the degradation of substituted naphthalenesulfonates by mixed cultures containing strain BN6 was studied in continuous cultures and was described by mathematical models.

  19. From labdanes to drimanes. Degradation of the side chain of dihydrozamoranic acid.

    PubMed

    Rodilla, Jesús M L; Díez, D; Urones, J G; Rocha, Pedro M

    2004-04-30

    A new route for the degradation of the saturated side chain of dihydrozamoranic acid has been devised, giving an advanced intermediate, compound 14, useful for the synthesis of insect antifeedants such as warburganal and polygodial.

  20. Evaluation of the performance degradation at PAFC effect of operating conditions on acid loss

    SciTech Connect

    Miyoshi, Hideaki; Uchida, Hiroyuki; Watanabe, Masahiro

    1996-12-31

    As a complimentary research project to the demonstration project of 5MW and 1 MW PAFC plants, the mechanism and rate of deterioration of the cells and stacks have been studied from 1995 FY conducted by NEDO, with the objective of establishing an estimation method for the service life-time of the cell stacks. As part of this project, this work has been performed to clarify basic phenomena of the performance degradation at PAFCs jointly by Yamanashi University, PAFC-TRA and PAFC manufacturers. The acid loss into exhaust gases is one of life limiting factors in PAFCs. To design the cells of long-life, it is important to estimate the phosphoric acid loss and to contrive ideas eliminating it. With the objective of obtaining basic data for simulating the acid loss in the large size cells, the effect of the operating conditions on the acid loss into exhaust gases has been studied experimentally by using a single cell with an active electrode area of 100 cm{sup 2}.

  1. Mechanistic QSAR models for interpreting degradation rates of sulfonamides in UV-photocatalysis systems.

    PubMed

    Huang, Xiangfeng; Feng, Yi; Hu, Cui; Xiao, Xiaoyu; Yu, Daliang; Zou, Xiaoming

    2015-11-01

    Photocatalysis is one of the most effective methods for treating antibiotic wastewater. Thus, it is of great significance to determine the relationship between degradation rates and structural characteristics of antibiotics in photocatalysis processes. In the present study, the photocatalytic degradation characteristics of 10 sulfonamides (SAs) were studied using two photocatalytic systems composed of nanophase titanium dioxide (nTiO2) plus ultraviolet (UV) and nTiO2/activated carbon fiber (ACF) plus UV. The results indicated that the largest apparent SA degradation rate constant (Kapp) is approximately 5 times as large as that of the smallest one. Based on the degradation mechanism and the partial least squares regression (PLS) method, optimum Quantitative Structure Activity Relationship (QSAR) models were developed for the two systems. Mechanistic models indicated that the degradation rule of SAs in the TiO2 systems strongly relates to their highest occupied molecular orbital (Ehomo), the maximum values of nucleophilic attack (f(+)x), and the minimum values of the most negative partial charge on a main-chain atom (q(C)min), whereas the maximum values of OH radical attack (f(0)x) and the apparent adsorption rate constant values (kad) are key factors affecting the degradation rule of SAs in the TiO2/ACF system.

  2. The importance of lactic acid bacteria for phytate degradation during cereal dough fermentation.

    PubMed

    Reale, Anna; Konietzny, Ursula; Coppola, Raffaele; Sorrentino, Elena; Greiner, Ralf

    2007-04-18

    Lactic acid fermentation of cereal flours resulted in a 100 (rye), 95-100 (wheat), and 39-47% (oat) reduction in phytate content within 24 h. The extent of phytate degradation was shown to be independent from the lactic acid bacteria strain used for fermentation. However, phytate degradation during cereal dough fermentation was positively correlated with endogenous plant phytase activity (rye, 6750 mU g(-1); wheat, 2930 mU g(-1); and oat, 23 mU g(-1)), and heat inactivation of the endogenous cereal phytases prior to lactic acid fermentation resulted in a complete loss of phytate degradation. Phytate degradation was restored after addition of a purified phytase to the liquid dough. Incubation of the cereal flours in buffered solutions resulted in a pH-dependent phytate degradation. The optimum of phytate degradation was shown to be around pH 5.5. Studies on phytase production of 50 lactic acid bacteria strains, previously isolated from sourdoughs, did not result in a significant production of intra- as well as extracellular phytase activity. Therefore, lactic acid bacteria do not participate directly in phytate degradation but provide favorable conditions for the endogenous cereal phytase activity by lowering the pH value.

  3. Laboratory study on OH-initiated degradation kinetics of dehydroabietic acid.

    PubMed

    Lai, Chengyue; Liu, Yongchun; Ma, Jinzhu; Ma, Qingxin; He, Hong

    2015-04-28

    Dehydroabietic acid (DHAA) is a specific organic tracer for the pyrolysis of conifer resin. To understand its atmospheric stability, the degradation behavior of particulate DHAA in the presence of hydroxyl radicals (OH) was investigated under different environmental conditions using a stainless steel reactor with volume of 30 cm(3), in the dark. At 25 °C and 40% relative humidity (RH), the second-order rate constant (k2) of pure DHAA with OH was measured to be 5.72 ± 0.87 × 10(-12) cm(3) molecule(-1) s(-1). The influence of temperature, RH and mixing state on the degradation kinetics of DHAA were also investigated. At 40% RH, k2 of pure DHAA increases with increasing temperature and follows the Arrhenius equation k2 = (8.9 ± 1.9) × 10(-10) exp[-(1508.2 ± 64.2)/T], while RH does not have significant impact on k2 at 25 °C. At 25 °C and 40% RH, compared with pure DHAA, the corresponding k2 for DHAA mixed with (NH4)2SO4 decreased to 4.58 ± 0.95 × 10(-12) cm(3) molecule(-1) s(-1), while the value was 3.30 ± 0.79 × 10(-12) cm(3) molecule(-1) s(-1) when mixed with soot. The atmospheric lifetime of DHAA varied from 2.3 ± 0.2 to 4.4 ± 0.8 days under different environmental conditions. This study indicates that degradation of DHAA by OH radicals is appreciable, and a significant error in source apportionment should be introduced if the contribution of degradation to DHAA concentration is not considered during air mass aging.

  4. Kinetics analysis for development of a rate constant estimation model for ultrasonic degradation reaction of methylene blue.

    PubMed

    Kobayashi, Daisuke; Honma, Chiemi; Matsumoto, Hideyuki; Takahashi, Tomoki; Kuroda, Chiaki; Otake, Katsuto; Shono, Atsushi

    2014-07-01

    Ultrasound has been used as an advanced oxidation method for wastewater treatment. Sonochemical degradation of organic compounds in aqueous solution occurs by pyrolysis and/or reaction with hydroxyl radicals. Moreover, kinetics of sonochemical degradation has been proposed. However, the effect of ultrasonic frequency on degradation rate has not been investigated. In our previous study, a simple model for estimating the apparent degradation rate of methylene blue was proposed. In this study, sonochemical degradation of methylene blue was performed at various frequencies. Apparent degradation rate constant was evaluated assuming that sonochemical degradation of methylene blue was a first-order reaction. Specifically, we focused on effects of ultrasonic frequency and power on rate constant, and the applicability of our proposed model was demonstrated. Using this approach, maximum sonochemical degradation rate was observed at 490 kHz, which agrees with a previous investigation into the effect of frequency on the sonochemical efficiency value evaluated by KI oxidation dosimetry. Degradation rate increased with ultrasonic power at every frequency. It was also observed that threshold power must be reached for the degradation reaction to progress. The initial methylene blue concentration and the apparent degradation rate constant have a relation of an inverse proportion. Our proposed model for estimating the apparent degradation rate constant using ultrasonic power and sonochemical efficiency value can apply to this study which extended the frequency and initial concentration range.

  5. Enhanced degradation of five organophosphorus pesticides in skimmed milk by lactic acid bacteria and its potential relationship with phosphatase production.

    PubMed

    Zhang, Ying-Hua; Xu, Di; Liu, Jia-Qi; Zhao, Xin-Huai

    2014-12-01

    Skimmed milk spiked with five organophosphorus pesticides (OPPs), chlorpyrifos, diazinon, fenitrothion, malathion and methyl parathion, was fermented by ten lactic acid bacteria (LAB) and four strain combinations at 42°C for 24h. OPPs left in the samples at different times were extracted, purified, detected by gas chromatography and calculated for degradation rate constants, based on a first-order reaction model. OPPs degradation was enhanced by the inoculated LAB, resulting in 0.8-225.4% increase in the rate constants. Diazinon and methyl parathion were more stable whereas chlorpyrifos, fenitrothion and malathion were more labile. Lactobacillus brevis 1.0209 showed the strongest acceleration on OPPs degradation while strain combination could bring about a synergy between the strains of lower ability. Phosphatase production of the strains might be one of the key factors responsible for the enhanced OPPs degradation, as the detected phosphatase activities were positively correlated to the measured degradation rate constants of OPPs (r=0.636-0.970, P<0.05).

  6. Degradation rates of low molecular weight PAH correlate with sediment TOC in marine subtidal sediments.

    PubMed

    Hinga, K R

    2003-04-01

    The degradation rate of low molecular weight (LMW) polycyclic aromatic hydrocarbons (PAH) in subtidal marine sediments was found to correlate with sediment total organic carbon (TOC) in stations sampled two or more times after the North Cape No. 2 fuel oil spill. With 2.5-5 months between samplings, stations with lower sediment TOC had lower fractions of LMW PAH remaining at the time of the second sampling. Apparent first-order degradation rate constants calculated for each station varied by nearly an order of magnitude between stations with a range of TOC from 0.4% to 7.3%. The correlation of degradation rate with sediment TOC can be used to provide improved and site-specific predictions of the initial time-course of LMW PAH concentrations in sediments after oil spills.

  7. Quantification of ascorbic acid and acetylsalicylic acid in effervescent tablets by CZE-UV and identification of related degradation products by heart-cut CZE-CZE-MS.

    PubMed

    Neuberger, Sabine; Jooß, Kevin; Ressel, Christian; Neusüß, Christian

    2016-12-01

    Capillary electrophoresis is commonly applied for the analysis of pharmaceutical products due to its high separation efficiency and selectivity. For this purpose, electrospray-ionization-(ESI)-interfering additives or electrolytes are often required, which complicates the identification of impurities and degradation products by mass spectrometry (MS). Here, a capillary zone electrophoresis (CZE) method with ultraviolet (UV) absorption detection for the simultaneous determination and quantification of ascorbic acid and acetylsalicylic acid in effervescent tablets was developed. Related degradation products were identified via CZE-CZE-MS. Systematic optimization yielded 100 mM tricine (pH = 8.8) as appropriate background electrolyte, resulting in baseline separation of ascorbic acid, acetylsalicylic acid, and related anionic UV-active degradation products. The CZE-UV method was successfully validated regarding the guidelines of the Food and Drug Administration. The validated method was applied to trace the degradation rate of the active pharmaceutical ingredients at defined ambient conditions. A heart-cut CZE-CZE-MS approach, including a 4-port-nL-valve, was performed for the identification of the observed degradation products. This 2D setup enables a precise cutting of accurate sample volumes (20 nL) and the independent operation of two physically separated CZE dimensions, which is especially beneficial regarding MS detection. Hence, the ESI-interfering tricine electrolyte components were separated from the analytes in a second electrophoretic dimension prior to ESI-MS detection. The degradation products were identified as salicylic acid and mono- and diacetylated ascorbic acid. This setup is expected to be generally applicable for the mass spectrometric characterization of CZE separated analytes in highly ESI-interfering electrolyte systems. Graphical Abstract A CZE-UV method for the quantification of effervescent tablet ingredients and degradation products

  8. Influence of oxalic acid formed on the degradation of phenol by Fenton reagent.

    PubMed

    Nakagawa, Hiroyuki; Yamaguchi, Emi

    2012-06-01

    The objective of this work is to examine the influence of oxalic acid formed on the degradation of phenol by Fenton reagent. Oxalic acid formed at initial stage within 30 min significantly suppresses the reduction of ferric ion, thus terminating degradation reaction. The yield of oxalic acid is dependent on the amount of ferrous ion dosed since the minimal amount of oxalic acid is formed after the degradation reaction terminates. Mineralization of phenol by Fenton reagent stagnates after 120 min under the conditions used in this study. The reason why the mineralization stagnated can be assumed to be following two mechanisms other than the depletion of H(2)O(2). In the case where a small amount of ferrous ions is dosed, the reduction of ferric ions is minimal by oxalic acid formed. In the case where a large amount of ferrous ions is dosed, the amount of degradable organic compounds is insufficient owing to preferential conversion to oxalic acid. The mineralization can be enhanced by the intermittent dosing of ferrous ions, which facilitates the suppression of oxalic acid formation during the degradation by Fenton reagent.

  9. Antioxidant activities of fucoidan degraded by gamma irradiation and acidic hydrolysis

    NASA Astrophysics Data System (ADS)

    Lim, Sangyong; Choi, Jong-il; Park, Hyun

    2015-04-01

    Low molecular weight fucoidan, prepared by radical degradation using gamma ray was investigated for its antioxidant activities with different assay methods. As the molecular weight of fucoidan decreased with a higher absorbed dose, ferric-reducing antioxidant power values increased, but β-carotene bleaching inhibition did not change significantly. The antioxidant activity of acid-degraded fucoidan was also examined to investigate the effect of different degradation methods. At the same molecular weight, fucoidan degraded by gamma irradiation showed higher 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity than that observed with the acidic method. This result reveals that in addition to molecular weight, the degradation method affects the antioxidant activity of fucoidan.

  10. Stress degradation studies and stability-indicating TLC-densitometric method of glycyrrhetic acid

    PubMed Central

    2013-01-01

    Background Glycyrrhetic acid, a pentacyclic triterpenoid, possesses a broad range of pharmacological activities and serves as template to synthesize many bioactive drugs. This paper describes a simple, accurate, and sensitive stability-indicating TLC densitometric method for the determination of glycyrrhetic acid and its degradation product as per the ICH guidelines. Results Separation was carried out on TLC aluminium sheet pre-coated with silica gel 60F254 using chloroform, methanol and formic acid (9:0.9:0.1, v/v). Compact spot for glycyrrhetic acid was found at Rf value of 0.42 ± 0.03. Densitometric analysis was carried out in the absorbance mode at λmax 254 nm. Glycyrrhetic acid was found to be stable to the exposure of base, neutral, oxidation, dry heating treatment and wet heating treatment, but showed degradation under acidic and photochemical conditions. Moreover, fragmentation pattern of glycyrrhetic acid was developed by using a positive ion electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QqTOF-MS/MS) hybrid instrument. A photo-degraded product was characterized through comparison of mass spectrometric studies with glycyrrhetic acid. Conclusion The developed stability-indicating TLC-densitometric method can be applied for routine analysis of glycyrrhetic acid in the presence of its degradation products. PMID:23327365

  11. Strategies to reduce short-chain organic acids and synchronously establish high-rate composting in acidic household waste.

    PubMed

    Bergersen, Ove; Bøen, Anne S; Sørheim, Roald

    2009-01-01

    The aim of this study was to document whether addition of lime or increased amount of bulking agent would ensure, efficiently, a predictable composting process in acidic SSOW applicable in full scale plants. The results show that both lime addition and increasing the amount of bulking agent relative to waste support the development of high-rate respiration in composting. Both strategies are considered efficient in establishing desired microbial composting processes of acid household waste. Reduction in the content of different organic acids and loss on ignition were higher when more bulking agent was used compared with adding 5% lime to the acidic SSOW. Respiration was completely repressed in samples with 10% lime, where pH remained high. In addition fat and protein seem to degrade faster with increasing amount of bulking agent.

  12. Proteins iodinated by the chloramine-T method appear to be degraded at an abnormally rapid rate after endocytosis

    SciTech Connect

    Opresko, L.; Wiley, H.S.; Wallace, R.A.

    1980-03-01

    Proteins labeled with either /sup 3/H by reductive methylation or /sup 125/I by the chloramine-T method were incubated with Xenopus laevis oocytes; the incorporation and acid precipitability of the proteins were then studied. The uptake rates of both specifically incorporated (vitellogenin) and nonspecifically incorporated proteins (bovine serum albumin and X. laevis serum proteins lacking albumin) were not influenced by the method of labeling. However, /sup 125/I-labeled proteins were apparently degraded at rates far exceeding their /sup 3/H-labeled counterparts, based on the generation of acid-soluble radioactivity. Thus, after a 3-hr incubation, 3 to 5 times more /sup 125/I-labeled bovine serum albumin and X. laevis serum proteins lacking albumin were degraded than the corresponding /sup 3/H-labeled proteins (95% compared to 30% and 75% compared to 15%, respectively), whereas after a 24-hr incubation, the degradation of /sup 125/I-labeled vitellogenin was 15 times greater than that of (/sup 3/H)vitellogenin labeled in vivo (60% compared to 4%). Moreover, examination of the relative amounts of /sup 3/H-compared to /sup 125/I-labeled bovine serum albumin deposited into the exogenously derived yolk platelet compartment of the oocyte revealed 7 times more acid-precipitable /sup 3/H-labeled protein, indicating that the observed discrepancies were not due to reincorporation of the /sup 3/H-labeled ligands. Passage of dissolved oocytes previously exposed to /sup 125/I-labeled bovine serum albumin (chloramine-T method) over a column of Bio-Gel P-10 revealed some breakdown of bovine serum albumin to intermediate molecular weight components and the presence of a large amount (approx. = 90%) of labeled low molecular weight compounds, which analysis showed to be 72% free iodine.

  13. Selective microbial degradation of saturated methyl branched chain fatty acid isomers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Three strains of Pseudomonas bacteria were screened for their capabilities of degrading chemically synthesized saturated branched-chain fatty acids (sbc-FAs). Mixtures of sbc-FAs with the methyl-branch located at various locales along the fatty acid were used as a carbon feedstock in shake-flask cu...

  14. Liquid chromatographic assay of diatrizoic acid and its diiodo degradation products in radio-opaque solutions

    SciTech Connect

    Farag, S.A.

    1995-03-01

    A liquid chromatographic method is described for the analysis of diatrizoic acid (2,4,6-triiodo-3,5-diacetamidobenzoic acid) and its 2,4- and 2,6-diiodo degradation products in radio-opaque injection solutions. The method is accurate, precise, and linear at a concentration range of 5-50 ppm. 12 refs., 6 figs., 5 tabs.

  15. In vitro degradation and erosion of degradable, segmented polyurethanes containing an amino acid-based chain extender.

    PubMed

    Skarja, G A; Woodhouse, K A

    2001-01-01

    In vitro degradation and erosion of novel, degradable segmented polyurethanes containing a phenylalanine diester chain extender were investigated by exposing the polymers to buffer. chymotrypsin, and trypsin solutions for up to 28 days. Polyurethane degradation and erosion were monitored by gravimetry, scanning electron microscopy (SEM), and gel permeation chromatography (GPC) and compared to a control polyurethane. Polyurethanes were synthesized using two different soft segments (polycaprolactone diol and polyethylene oxide) of variable molecular weight. Inclusion of the phenylalanine-based chain extender resulted in an increased susceptibility to enzyme-mediated, but not buffer-mediated, erosion in comparison to the control polyurethane. SEM analysis indicated that enzyme-mediated erosion proceeded via a surface-limited mechanism resulting in a progressive removal of material from the surface inwards with time. The magnitude of degradation and erosion was highly variable and was dependent on soft segment type and molecular weight. The range of degradation rates, as well as physicochemical properties, makes these polyurethanes potentially useful for a wide range of biomedical applications.

  16. Kinetic analysis of acid orange 7 degradation by pulsed discharge plasma combined with activated carbon and the synergistic mechanism exploration.

    PubMed

    Guo, He; Wang, Huijuan; Wu, Qiangshun; Zhou, Guangshun; Yi, Chengwu

    2016-09-01

    The synergistic technique of pulsed discharge plasma (PDP) and activated carbon (AC) was built to investigate the kinetics of acid orange 7 (AO7) degradation under different conditions of AC addition, electrode gap, initial pH value of solution, gas variety and gas flow rate. Emission spectra of OH and O, UV-vis absorption spectra of the AO7 solution and TOC removal were measured to illustrate the synergistic mechanism of the PDP and the AC. The obtained results indicated that the kinetic constant of AO7 degradation increased from 0.00947 min(-1) to 0.01419 min(-1) when 4 g AC was added into the PDP system; AO7 degradation was higher in the case of alkaline solution when oxygen was used as the flow gas in the PDP/AC system, 2 L/min oxygen flow was more favorable for the degradation. Results of the relative emission intensities of OH and O indicated the catalytic effect of the AC on the active species formation as well as the important role of the two radicals for the AO7 degradation. There was no new peaks appeared by the UV-vis analysis of the AO7 solution after 60 min treatment. The highest TOC removal in the PDP/AC system was 30.3%, which was achieved under the condition of 4 L/min air flow rate and 3 initial pH value.

  17. Electrochemical assisted photocatalytic degradation of salicylic acid with highly ordered TiO2 nanotube electrodes

    NASA Astrophysics Data System (ADS)

    Zhang, Qian; Zhu, Jinwei; Wang, Ying; Feng, Jiangtao; Yan, Wei; Xu, Hao

    2014-07-01

    To explore the kinetics of photoelectrocatalytic degradation of salicylic acid, one of the important PPCPs, highly ordered TiO2 nanotube arrays (NTs) were prepared by the electrochemical anodization and characterized with scanning electron microscopy and X-ray diffraction techniques. The effect of TiO2 NTs properties, bias potential, initial salicylic acid concentration and solution pH on the degradation efficiency was studied and carefully analyzed. The results revealed that the salicylic acid degradation follows quasi-first order kinetics in the photoelectrocatalytic process, and the fastest decay kinetics was achieved in acidic environment (pH 2). The result was further interpreted through the electrochemical impedance spectroscopy. It is confirmed that the electrochemical assisted photocatalysis is a synergetic approach to combat stable organic substances with improved efficiency.

  18. Determination of the Acid-Base Dissociation Constant of Acid-Degradable Hexamethylenetetramine by Capillary Zone Electrophoresis.

    PubMed

    Takayanagi, Toshio; Shimakami, Natsumi; Kurashina, Masashi; Mizuguchi, Hitoshi; Yabutani, Tomoki

    2016-01-01

    The acid-base equilibrium of hexamethylenetetramine (hexamine) was analyzed with its effective electrophoretic mobility by capillary zone electrophoresis. Although hexamine is degradable in a weakly acidic aqueous solution, and the degraded products of ammonia and formaldehyde can be formed, the effective electrophoretic mobility of hexamine was measured in the pH range between 2.8 and 6.9. An acid-base dissociation equilibrium of the protonated hexamine was analyzed based on the mobility change, and an acid dissociation constant of pKa = 4.93 ± 0.01 (mean ± standard error, ionic strength: 0.020 mol dm(-3)) was determined. The monoprotic acid-base equilibrium of hexamine was confirmed through comparisons of its electrophoretic mobility with the N-ethylquinolinium ion and with the monocationic N-ethyl derivative of hexamine, as well as a slope analysis of the dissociation equilibrium.

  19. Photo-degradation of clofibric acid by ultraviolet light irradiation at 185 nm.

    PubMed

    Li, Wenzhen; Lu, Shuguang; Chen, Nuo; Gu, Xiaogang; Qiu, Zhaofu; Fan, Ji; Lin, Kuangfei

    2009-01-01

    As a metabolite of lipid regulators, clofibric acid (CA) was investigated in this study for its ultraviolet (UV) degradation at monochromatic wavelength of 185 nm using Milli-Q water and sewage treatment plant (STP) effluent. The effects of CA initial concentration, solution pH, humic acid (HA), nitrate and bicarbonate anions on CA degradation performances were evaluated. All CA degradation patterns well fitted the pseudo-first-order kinetic model. The results showed that OH generated from water photolysis by UV185 irradiation was involved, resulting in indirect CA photolysis but contributed less to the whole CA removal when compared to the main direct photolysis process. Acid condition favored slightly to CA degradation and other constituents in solution, such as HA (5.0-100.0 mg L(-1)), nitrate and bicarbonate anions (1.0x10(-3) mol L(-1) and 0.1 mol L(-1)), had negative effects on CA degradation. When using real STP effluent CA degradation could reach 97.4% (without filtration) and 99.3% (with filtration) after 1 hr irradiation, showing its potential mean in pharmaceuticals removal in UV disinfection unit. Mineralization tests showed that rapid chloride ion release happened, resulting in no chlorinated intermediates accumulation, and those non-chlorinated intermediate products could further be nearly completely degraded to CO2 and H2O after 6 hrs.

  20. Tannin content and rate of ruminal protein degradation of legume hays

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This work evaluated ruminal protein degradation rates of legume hays that varied in tannin content. Two cuttings of 5 varieties of birdsfoot trefoil, (Lotus corniculatus), selected for different tannin contents but similar NDF and CP contents, and Spredor 4 alfalfa (control) were conserved as hay. S...

  1. Spatial Moment Equations for a Groundwater Plume with Degradation and Rate-Limited Sorption

    EPA Science Inventory

    In this note, we analytically derive the solution for the spatial moments of groundwater solute concentration distributions simulated by a one-dimensional model that assumes advective-dispersive transport with first-order degradation and rate-limited sorption. Sorption kinetics...

  2. Effect of application rate on fumigant degradation in five agricultural soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fumigants continue to be used in soil disinfestation for many high value crops. There is a significant knowledge gap on how fumigant concentration in soil impacts fumigant dissipation and determination of the most efficient rate. The aim of this study was to determine the degradation characteristics...

  3. LEACHING AND DEGRADATION OF 2,4-DICHLOROPHENOXIACETIC ACID, IN COLOMBIA RICE FLOODED SOIL.

    PubMed

    Huertas, J; Guerrero, J A; Martinez-Cordon, M J

    2015-01-01

    Rice is mostly cultivated on soil held under flooded conditions. Under these conditions pesticides undergo reductive transformations which are characteristic to rice fields and other anaerobic systems. The present study was undertaken to evaluate the mobility and persistence of 2,4-dichlorophenoxy acetic acid (2,4-D) under laboratory conditions for the rice crop in Espinal, Colombia. A displacement study was performed on a hand packed soil column 30 cm length. After leaching experiment, the soil from column was sliced into six successive sections (5 cm). Methanol acidified (H3PO4 0.25%) extraction was used to determine the herbicide residues in each section. 2,4-D experimental breakthrough curve was analyzed using Stanmod program (inverse problem) to obtain transport parameters. The non-equilibrium physical model fitted well the experimental breakthrough curve. The recovery percent of 2,4-D in leachates was 36.44% after 3.4 pore volumes, and retardation factor was 2.1, indicating low adsorption in that conditions. 2,4-D was rapidly degraded, with DT50 = 11.4 days. The results suggest that 2,4-D under flooded conditions have a high potential for leaching through the soil profile, although the elevated rate of degradation reduced the ground water contamination risk.

  4. Non-UV light influences the degradation rate of crop protection products.

    PubMed

    Davies, Lawrence O; Bramke, Irene; France, Emma; Marshall, Samantha; Oliver, Robin; Nichols, Carol; Schäfer, Hendrik; Bending, Gary D

    2013-08-06

    Crop protection products (CPPs) are subject to strict regulatory evaluation, including laboratory and field trials, prior to approval for commercial use. Laboratory tests lack environmental realism, while field trials are difficult to control. Addition of environmental complexity to laboratory systems is therefore desirable to mimic a field environment more effectively. We investigated the effect of non-UV light on the degradation of eight CPPs (chlorotoluron, prometryn, cinosulfuron, imidacloprid, lufenuron, propiconazole, fludioxonil, and benzovindiflupyr) by addition of non-UV light to standard OECD 307 guidelines. Time taken for 50% degradation of benzovindiflupyr was halved from 373 to 183 days with the inclusion of light. Similarly, time taken for 90% degradation of chlorotoluron decreased from 79 to 35 days under light conditions. Significant reductions in extractable parent compound occurred under light conditions for prometryn (4%), imidacloprid (8%), and fludioxonil (24%) compared to dark controls. However, a significantly slower rate of cinosulfuron (14%) transformation was observed under light compared to dark conditions. Under light conditions, nonextractable residues were significantly higher for seven of the CPPs. Soil biological and chemical analyses suggest that light stimulates phototroph growth, which may directly and/or indirectly impact CPP degradation rates. The results of this study strongly suggest that light is an important parameter affecting CPP degradation, and inclusion of light into regulatory studies may enhance their environmental realism.

  5. Characterization of bacterial diversity in an atrazine degrading enrichment culture and degradation of atrazine, cyanuric acid and biuret in industrial wastewater.

    PubMed

    Dutta, Anirban; Vasudevan, Venugopal; Nain, Lata; Singh, Neera

    2016-01-01

    An enrichment culture was used to study atrazine degradation in mineral salt medium (MSM) (T1), MSM+soil extract (1:1, v/v) (T2) and soil extract (T3). Results suggested that enrichment culture required soil extract to degrade atrazine, as after second sequential transfer only partial atrazine degradation was observed in T1 treatment while atrazine was completely degraded in T2 and T3 treatments even after fourth transfer. Culture independent polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) technique confirmed selective enrichment of genus Bacillus along with Pseudomonas and Burkholderia. Degradation of atrazine/metabolites in the industrial wastewater was studied at different initial concentrations of the contaminants [wastewater-water (v/v) ratio: T1, 1:9; T2, 2:8; T3, 3:7; T4, 5:5 and T5, undiluted effluent]. The initial concentrations of atrazine, cyanuric acid and biuret ranged between 5.32 and 53.92 µg mL(-1), 265.6 and 1805.2 µg mL(-1) and 1.85 and 16.12 µg mL(-1), respectively. The enrichment culture was able to completely degrade atrazine, cyanuric acid and biuret up to T4 treatment, while no appreciable degradation of contaminants was observed in the undiluted effluent (T5). Inability of enrichment culture to degrade atrazine/metabolites might be due to high concentrations of cyanuric acid. Therefore, a separate study on cyanuric acid degradation suggested: (i) no appreciable cyanuric acid degradation with accumulation of an unidentified metabolite in the medium where cyanuric acid was supplemented as the sole source of carbon and nitrogen; (ii) partial cyanuric acid degradation with accumulation of unidentified metabolite in the medium containing additional nitrogen source; and (iii) complete cyanuric acid degradation in the medium supplemented with an additional carbon source. This unidentified metabolite observed during cyanuric acid degradation and also detected in the enrichment culture inoculated wastewater samples

  6. Rapid estimation of glucosinolate thermal degradation rate constants in leaves of Chinese kale and broccoli (Brassica oleracea) in two seasons.

    PubMed

    Hennig, Kristin; Verkerk, Ruud; Bonnema, Guusje; Dekker, Matthijs

    2012-08-15

    Kinetic modeling was used as a tool to quantitatively estimate glucosinolate thermal degradation rate constants. Literature shows that thermal degradation rates differ in different vegetables. Well-characterized plant material, leaves of broccoli and Chinese kale plants grown in two seasons, was used in the study. It was shown that a first-order reaction is appropriate to model glucosinolate degradation independent from the season. No difference in degradation rate constants of structurally identical glucosinolates was found between broccoli and Chinese kale leaves when grown in the same season. However, glucosinolate degradation rate constants were highly affected by the season (20-80% increase in spring compared to autumn). These results suggest that differences in glucosinolate degradation rate constants can be due to variation in environmental as well as genetic factors. Furthermore, a methodology to estimate rate constants rapidly is provided to enable the analysis of high sample numbers for future studies.

  7. [Degradation of urea and ethyl carbamate in Chinese Rice wine by recombinant acid urease].

    PubMed

    Zhou, Jianli; Kang, Zhen; Liu, Qingtao; Du, Guocheng; Chen, Jian

    2016-01-01

    Ethyl carbamate (EC) as a potential carcinogen commonly exists in traditional fermented foods. It is important eliminate urea that is the precursors of EC in many fermented foods, including Chinese Rice wine. On the basis of achieving high-level overexpression of food-grade ethanol-resistant acid urease, we studied the hydrolysis of urea and EC with the recombinant acid urease. Recombinant acid urease showed degraded urea in both the simulated system with ethanol and Chinese Rice wine (60 mg/L of urea was completely degraded within 25 h), indicating that the recombinant enzyme is suitable for the elimination of urea in Chinese Rice wine. Although recombinant acid urease also has degradation catalytic activity on EC, no obvious degradation of EC was observed. Further investigation results showed that the Km value for urea and EC of the recombinant acid urease was 0.7147 mmol/L and 41.32 mmol/L, respectively. The results provided theoretical foundation for realizing simultaneous degradation of urea and EC.

  8. Energetics and kinetics of anaerobic aromatic and fatty acid degradation. Final report

    SciTech Connect

    Michael J. McInerney

    1996-06-24

    The factors that affect the rate and extent of a model aromatic compound, benzoate, in methanogenic environments was studied. Benzoate is degraded to a threshold concentration below which no further substrate degradation occurs. The threshold concentration depended on the substrate concentration and the amount of acetate present. The threshold value was not a function of the kinetic ability of the organism or toxicity of the end products. Rather a minimal Gibb's free energy value may exist where thermodynamic constraints preclude further benzoate degradation. In addition, new bacterial species were isolated and described, that degrade benzoate or reduce iron, cobalt and other metals.

  9. Degradability of fluorapatite-leucite ceramics in naturally acidic agents.

    PubMed

    Kukiattrakoon, Boonlert; Hengtrakool, Chanothai; Kedjarune-Leggat, Ureporn

    2010-10-01

    This study was conducted to evaluate the titratable acidity and effect of naturally acidic agents on the surface microhardness, elemental composition, and surface morphology of fluorapatite-leucite ceramics. One hundred and ten ceramic disks (IPS d.SIGN), 12.0 mm in diameter and 2.0 mm in thickness, were fabricated. Before immersion, the baseline data of Vickers microhardness and elemental composition were recorded. Four groups were immersed in acidic agents (citrate buffer solution, green mango juice, and pineapple juice) and deionized water (control) at 37ºC for 168 hours, whereas one group was immersed in 4% acetic acid at 80ºC for 168 hours. After immersion, specimens were evaluated and data were analyzed using one-way repeated ANOVA and Tukey's test (α=0.05). Microhardness values significantly decreased after immersion (p<0.05). In terms of elemental composition, the weight percentages of silicon, potassium, aluminum, and sodium also decreased after immersion (p<0.05). Results of this study showed that fluorapatite-leucite ceramics were affected by long-term immersion in acidic agents.

  10. Modeling the degradation of Portland cement pastes by biogenic organic acids

    SciTech Connect

    De Windt, Laurent; Devillers, Philippe

    2010-08-15

    Reactive transport models can be used to assess the long-term performance of cement-based materials subjected to biodegradation. A bioleaching test (with Aspergillus niger fungi) applied to ordinary Portland cement pastes during 15 months is modeled with HYTEC. Modeling indicates that the biogenic organic acids (acetic, butyric, lactic and oxalic) strongly accelerate hydrate dissolution by acidic hydrolysis whilst their complexation of aluminum has an effect on the secondary gel stability only. The deepest degradation front corresponds to portlandite dissolution and decalcification of calcium silicate hydrates. A complex pattern of sulfate phases dissolution and precipitation takes place in an intermediate zone. The outermost degraded zone consists of alumina and silica gels. The modeling accurateness of calcium leaching, pH evolution and degradation thickness is consistently enhanced whilst considering increase of diffusivity in the degraded zones. Precipitation of calcium oxalate is predicted by modeling but was hindered in the bioleaching reactor.

  11. Synthesis and characterization of hydrolytically degradable copolyester biomaterials based on glycolic acid, sebacic acid and ethylene glycol.

    PubMed

    Simitzis, J; Soulis, S; Triantou, D; Zoumpoulakis, L; Zotali, P

    2011-12-01

    Copolyesters of glycolic acid (G) combined with sebacic acid (S) and ethylene glycol were synthesized in different molar ratios (G: 0-100% and S: 100-0%) and their hydrolytic degradation was studied and correlated with their structures. Based on the FTIR spectra of the homopolyesters and copolyesters and the normalized peak intensity of the I(2918), I(2848) and I(1087) for the corresponding wavenumbers, it is concluded that the I(2918) and the I(2848) are in accordance with the mean number degree of polymerization of ethylene sebacate units and the I(1087) is in accordance with the mean number degree of polymerization of glycolate units. Based on the XRD diffractograms, poly(ethylene sebacate) and poly(glycolic acid) belong to the monoclinic and the orthorhombic crystal system, respectively and both have higher crystallinity than the copolyesters. The experimental data of the hydrolytic degradation were fitted with exponential rise to maximum type functions using two-parameter model and four-parameter model. Three regions can been distinguished for the hydrolytic degradation by decreasing the molar feed ratio of sebacic acid, which are correlated with the changes of crystallinity. Two copolyesters are proposed: first the copolyester with high amount of glycolate units (S10G90) having higher hydrolytic degradation than G100 and second the copolyester with equal amount of glycolate and ethylene sebacate units (S50G50), having lower hydrolytic degradation than G100. These hydrolytically degradable copolyesters are soluble in common organic solvents, opposite to poly(glycolic acid) and could have perspectives for biomedical applications.

  12. The earthworm Aporrectodea caliginosa stimulates abundance and activity of phenoxyalkanoic acid herbicide degraders

    PubMed Central

    Liu, Ya-Jun; Zaprasis, Adrienne; Liu, Shuang-Jiang; Drake, Harold L; Horn, Marcus A

    2011-01-01

    2-Methyl-4-chlorophenoxyacetic acid (MCPA) is a widely used phenoxyalkanoic acid (PAA) herbicide. Earthworms represent the dominant macrofauna and enhance microbial activities in many soils. Thus, the effect of the model earthworm Aporrectodea caliginosa (Oligochaeta, Lumbricidae) on microbial MCPA degradation was assessed in soil columns with agricultural soil. MCPA degradation was quicker in soil with earthworms than without earthworms. Quantitative PCR was inhibition-corrected per nucleic acid extract and indicated that copy numbers of tfdA-like and cadA genes (both encoding oxygenases initiating aerobic PAA degradation) in soil with earthworms were up to three and four times higher than without earthworms, respectively. tfdA-like and 16S rRNA gene transcript copy numbers in soil with earthworms were two and six times higher than without earthworms, respectively. Most probable numbers (MPNs) of MCPA degraders approximated 4 × 105 gdw−1 in soil before incubation and in soil treated without earthworms, whereas MPNs of earthworm-treated soils were approximately 150 × higher. The aerobic capacity of soil to degrade MCPA was higher in earthworm-treated soils than in earthworm-untreated soils. Burrow walls and 0–5 cm depth bulk soil displayed higher capacities to degrade MCPA than did soil from 5–10 cm depth bulk soil, expression of tfdA-like genes in burrow walls was five times higher than in bulk soil and MCPA degraders were abundant in burrow walls (MPNs of 5 × 107 gdw−1). The collective data indicate that earthworms stimulate abundance and activity of MCPA degraders endogenous to soil by their burrowing activities and might thus be advantageous for enhancing PAA degradation in soil. PMID:20740027

  13. Elucidating PID Degradation Mechanisms and In Situ Dark I–V Monitoring for Modeling Degradation Rate in CdTe Thin-Film Modules

    SciTech Connect

    Hacke, Peter; Spataru, Sergiu; Johnston, Steve; Terwilliger, Kent; VanSant, Kaitlyn; Kempe, Michael; Wohlgemuth, John; Kurtz, Sarah; Olsson, Anders; Propst, Michelle

    2016-11-01

    A progression of potential-induced degradation (PID) mechanisms are observed in CdTe modules, including shunting/junction degradation and two different manifestations of series resistance depending on the stress level and water ingress. The dark I-V method for in-situ characterization of Pmax based on superposition was adapted for the thin-film modules undergoing PID in view of the degradation mechanisms observed. An exponential model based on module temperature and relative humidity was fit to the PID rate for multiple stress levels in chamber tests and validated by predicting the observed degradation of the module type in the field.

  14. Dose rate effects in radiation degradation of polymer-based cable materials

    NASA Astrophysics Data System (ADS)

    Plaček, V.; Bartoníček, B.; Hnát, V.; Otáhal, B.

    2003-08-01

    Cable ageing under the nuclear power plant (NPP) conditions must be effectively managed to ensure that the required plant safety and reliability are maintained throughout the plant service life. Ionizing radiation is one of the main stressors causing age-related degradation of polymer-based cable materials in air. For a given absorbed dose, radiation-induced damage to a polymer in air environment usually depends on the dose rate of the exposure. In this work, the effect of dose rate on the degradation rate has been studied. Three types of NPP cables (with jacket/insulation combinations PVC/PVC, PVC/PE, XPE/XPE) were irradiated at room temperature using 60Co gamma ray source at average dose rates of 7, 30 and 100 Gy/h with the doses up to 590 kGy. The irradiated samples have been tested for their mechanical properties, thermo-oxidative stability (using differential scanning calorimetry, DSC), and density. In the case of PVC and PE samples, the tested properties have shown evident dose rate effects, while the XPE material has shown no noticeable ones. The values of elongation at break and the thermo-oxidative stability decrease with the advanced degradation, density tends to increase with the absorbed dose. For XPE samples this effect can be partially explained by the increase of crystallinity. It was tested by the DSC determination of the crystalline phase amount.

  15. Effects of ultrasonic processing on degradation of salvianolic acid B in aqueous solution.

    PubMed

    Guo, Y X; Zhang, L; Lu, L; Liu, E H; Shi, C Z

    2016-09-10

    To evaluate the stability of salvianolic acid B (Sal B) under ultrasound-assisted extraction in the pharmaceutical industry, degradation of Sal B under ultrasonic irradiation was investigated as the function of buffer concentration, pH, and temperature. With regard to Sal-B concentration, a first-order degradation process was determined, with 10% change in assay from its initial concentration as t90=4.81h, under maximum stability acidic conditions (pH 2.0) and at 25°C. The logkpH-pH profile described by specific acid-base catalysis and water molecules supported the experimental results. Liquid chromatography-mass spectrometry (LC-MS) analyses revealed 7 major degradation products whose structures were characterized by electrospray ionization/mass spectrometry. A primary degradation pathway involved cleavage of the ester bond and ring-opening of benzofuran in Sal B was proposed. The complete degradation pathway of Sal B was also proposed. Results showed that ultrasonic irradiation leads to degradation of Sal B in aqueous solution.

  16. Screening of indigenous oxalate degrading lactic acid bacteria from human faeces and South Indian fermented foods: assessment of probiotic potential.

    PubMed

    Gomathi, Sivasamy; Sasikumar, Ponnusamy; Anbazhagan, Kolandaswamy; Sasikumar, Sundaresan; Kavitha, Murugan; Selvi, M S; Selvam, Govindan Sadasivam

    2014-01-01

    Lactic acid bacteria (LAB) have the potential to degrade intestinal oxalate and this is increasingly being studied as a promising probiotic solution to manage kidney stone disease. In this study, oxalate degrading LAB were isolated from human faeces and south Indian fermented foods, subsequently assessed for potential probiotic property in vitro and in vivo. Based on preliminary characteristics, 251 out of 673 bacterial isolates were identified as LAB. A total of 17 strains were found to degrade oxalate significantly between 40.38% and 62.90% and were subjected to acid and bile tolerance test. Among them, nine strains exhibited considerable tolerance up to pH 3.0 and at 0.3% bile. These were identified as Lactobacillus fermentum and Lactobacillus salivarius using 16S rDNA sequencing. Three strains, Lactobacillus fermentum TY5, Lactobacillus fermentum AB1, and Lactobacillus salivarius AB11, exhibited good adhesion to HT-29 cells and strong antimicrobial activity. They also conferred resistance to kanamycin, rifampicin, and ampicillin, but were sensitive to chloramphenicol and erythromycin. The faecal recovery rate of these strains was observed as 15.16% (TY5), 6.71% (AB1), and 9.3% (AB11) which indicates the colonization ability. In conclusion, three efficient oxalate degrading LAB were identified and their safety assessments suggest that they may serve as good probiotic candidates for preventing hyperoxaluria.

  17. [Analysis of alkaline CuO degradation products of acid detergent fiber from tobacco leaves by using liquid chromatography].

    PubMed

    Hao, Weiqiang; Wang, Leijun; Wu, Shun; Yue, Bangyi; Chen, Qiang; Zhang, Peipei

    2015-07-01

    The acid detergent fiber (ADF) from tobacco leaves was obtained by treating the sample with petroleum ether-ethanol (6:4, v/v), 30 g/L sodium dodecylsulfate and 0.5 mol/L sulphuric acid containing 20 g/L hexadecyl trimethyl ammonium bromide successively. The ADF was degraded by the alkaline CuO oxidation procedure. In this work, six samples of ADF degradation products from tobacco leaves were prepared. The samples were analyzed by using gradient liquid chromatography (LC) where an Ultimate XB C18 column was used as stationary phase, with a mixture of methanol and water as mobile phase, at a column temperature of 35 °C and a flow rate of 0.8 mL/min. Dual wavelengths of 280 nm and 320 nm were chosen for the detection. It was found that there were four characteristic peaks for the ADF degradation products. By taking these peaks as research object, the optimum time for the degradation was found to be 5 h and the sample solution could be kept stable within 7 days. The established method may provide a new approach for the studies of the differences between lignin composition in different tobacco leaves and the relationship between lignin content and the smoking quality of tobacco leaves.

  18. Screening of Indigenous Oxalate Degrading Lactic Acid Bacteria from Human Faeces and South Indian Fermented Foods: Assessment of Probiotic Potential

    PubMed Central

    Kavitha, Murugan; Selvi, M. S.; Selvam, Govindan Sadasivam

    2014-01-01

    Lactic acid bacteria (LAB) have the potential to degrade intestinal oxalate and this is increasingly being studied as a promising probiotic solution to manage kidney stone disease. In this study, oxalate degrading LAB were isolated from human faeces and south Indian fermented foods, subsequently assessed for potential probiotic property in vitro and in vivo. Based on preliminary characteristics, 251 out of 673 bacterial isolates were identified as LAB. A total of 17 strains were found to degrade oxalate significantly between 40.38% and 62.90% and were subjected to acid and bile tolerance test. Among them, nine strains exhibited considerable tolerance up to pH 3.0 and at 0.3% bile. These were identified as Lactobacillus fermentum and Lactobacillus salivarius using 16S rDNA sequencing. Three strains, Lactobacillus fermentum TY5, Lactobacillus fermentum AB1, and Lactobacillus salivarius AB11, exhibited good adhesion to HT-29 cells and strong antimicrobial activity. They also conferred resistance to kanamycin, rifampicin, and ampicillin, but were sensitive to chloramphenicol and erythromycin. The faecal recovery rate of these strains was observed as 15.16% (TY5), 6.71% (AB1), and 9.3% (AB11) which indicates the colonization ability. In conclusion, three efficient oxalate degrading LAB were identified and their safety assessments suggest that they may serve as good probiotic candidates for preventing hyperoxaluria. PMID:24723820

  19. Bioaugmentation of bromoamine acid degradation with Sphingomonas xenophaga QYY and DNA fingerprint analysis of augmented systems.

    PubMed

    Qu, Yuanyuan; Zhou, Jiti; Wang, Jing; Song, Zhiyong; Xing, Linlin; Fu, Xiang

    2006-02-01

    One high-effective bromoamine acid (1-amino-4-bromoanthraquinone-2-sulfonic acid, BAA) degrading strain was isolated previously with the ability to use BAA as sole source of carbon and nitrogen. It was identified as Sphingomonas xenophaga QYY by 16S rDNA sequence analysis and physio-biochemical tests. In this study, bioaugmentation of BAA degradation with suspended and immobilized cells of strain QYY was investigated. The optimal degradation conditions were as follows: temperature 30 degrees C, pH 6.0-7.0, 150 rev min(-1) and the immobilized cells maintained degradation activity to BAA after 60 days storage at 4 degrees C. The structure of BAA was evidently changed according to the analysis of total organic carbon removal of BAA (about 50%) and the UV-VIS spectra changes during the biodegradation. Bioaugmented systems exhibited stronger abilities degrading BAA than the non-bioaugmented control ones. And microbial community dynamics of augmented systems was revealed by amplified ribosomal DNA restriction analysis (ARDRA), a modern DNA fingerprint technique. The results indicated that the microbial community dynamics was substantially changed throughout the augmentation process. This study suggests that it is feasible and potentially useful to enhance BAA degradation using bioaugmentation with the immobilized cells of BAA-degrading bacterium.

  20. Heart Rate Response and Lactic Acid Concentration in Squash Players.

    ERIC Educational Resources Information Center

    Beaudin, Paula; And Others

    1978-01-01

    It was concluded that playing squash is an activity that results in heart rate responses of sufficient intensity to elicit aerobic training effects without producing high lactic acid concentration in the blood. (MM)

  1. ESTIMATION OF CARBOXYLIC ACID ESTER HYDROLYSIS RATE CONSTANTS

    EPA Science Inventory

    SPARC chemical reactivity models were extended to calculate hydrolysis rate constants for carboxylic acid esters from molecular structure. The energy differences between the initial state and the transition state for a molecule of interest are factored into internal and external...

  2. Competitive kinetics versus stopped flow method for determining the degradation rate constants of steroids by ozonation.

    PubMed

    López-López, Alberto; Flores-Payán, Valentín; León-Becerril, Elizabeth; Hernández-Mena, Leonel; Vallejo-Rodríguez, Ramiro

    2016-01-01

    Steroids are classified as endocrine disrupting chemicals; they are persistent with low biodegradability and are hardly degraded by conventional methods. Ozonation process has been effective for steroids degradation and the determination of the kinetics is a fundamental aspect for the design and operation of the reactor. This study assessed two methods: competitive kinetics and stopped flow, for determining the degradation kinetics of two steroids, estradiol (E2) and ethinylestradiol (EE2) in spiked water. Experiments were performed at pH 6, 21 °C, and using tertbutyl alcohol as scavenger of hydroxyl radicals; competitive kinetics method used sodium phenolate as reference compound. For the stopped flow, the experiments were performed in a BioLogic SFM-3000/S equipment. For both methods, the second order rate constants were in the order of 10(6) and 10(5) M(-1) s(-1) for E2 and EE2 respectively. The competitive kinetics can be applied with assurance and reliability but needing an additional analysis method to measure the residual concentrations. Stopped flow method allows the evaluation of the degradation kinetics in milliseconds and avoids the use of additional analytical methodologies; this method allows determining the reaction times on line. The methods are applicable for degradation of other emerging contaminants or other steroids and could be applied in water treatment at industrial level. Finally, it is important to consider the resources available to implement the most appropriate method, either competitive kinetics or the stopped-flow method.

  3. Quantifying protein synthesis and degradation in Arabidopsis by dynamic 13CO2 labeling and analysis of enrichment in individual amino acids in their free pools and in protein.

    PubMed

    Ishihara, Hirofumi; Obata, Toshihiro; Sulpice, Ronan; Fernie, Alisdair R; Stitt, Mark

    2015-05-01

    Protein synthesis and degradation represent substantial costs during plant growth. To obtain a quantitative measure of the rate of protein synthesis and degradation, we supplied (13)CO2 to intact Arabidopsis (Arabidopsis thaliana) Columbia-0 plants and analyzed enrichment in free amino acids and in amino acid residues in protein during a 24-h pulse and 4-d chase. While many free amino acids labeled slowly and incompletely, alanine showed a rapid rise in enrichment in the pulse and a decrease in the chase. Enrichment in free alanine was used to correct enrichment in alanine residues in protein and calculate the rate of protein synthesis. The latter was compared with the relative growth rate to estimate the rate of protein degradation. The relative growth rate was estimated from sequential determination of fresh weight, sequential images of rosette area, and labeling of glucose in the cell wall. In an 8-h photoperiod, protein synthesis and cell wall synthesis were 3-fold faster in the day than at night, protein degradation was slow (3%-4% d(-1)), and flux to growth and degradation resulted in a protein half-life of 3.5 d. In the starchless phosphoglucomutase mutant at night, protein synthesis was further decreased and protein degradation increased, while cell wall synthesis was totally inhibited, quantitatively accounting for the inhibition of growth in this mutant. We also investigated the rates of protein synthesis and degradation during leaf development, during growth at high temperature, and compared synthesis rates of Rubisco large and small subunits of in the light and dark.

  4. Degradation of hydroxycinnamic acid mixtures in aqueous sucrose solutions by the Fenton process.

    PubMed

    Nguyen, Danny M T; Zhang, Zhanying; Doherty, William O S

    2015-02-11

    The degradation efficiencies and behaviors of caffeic acid (CaA), p-coumaric acid (pCoA), and ferulic acid (FeA) in aqueous sucrose solutions containing the mixture of these hydroxycinnamic acids (HCAs) were studied by the Fenton oxidation process. Central composite design and multiresponse surface methodology were used to evaluate and optimize the interactive effects of process parameters. Four quadratic polynomial models were developed for the degradation of each individual acid in the mixture and the total HCAs degraded. Sucrose was the most influential parameter that significantly affected the total amount of HCA degraded. Under the conditions studied there was a <0.01% loss of sucrose in all reactions. The optimal values of the process parameters for a 200 mg/L HCA mixture in water (pH 4.73, 25.15 °C) and sucrose solution (13 mass %, pH 5.39, 35.98 °C) were 77% and 57%, respectively. Regression analysis showed goodness of fit between the experimental results and the predicted values. The degradation behavior of CaA differed from those of pCoA and FeA, where further CaA degradation is observed at increasing sucrose and decreasing solution pH. The differences (established using UV/vis and ATR-FTIR spectroscopy) were because, unlike the other acids, CaA formed a complex with Fe(III) or with Fe(III) hydrogen-bonded to sucrose and coprecipitated with lepidocrocite, an iron oxyhydroxide.

  5. [Degradation of L-phenylalanine and of aromatic carboxylic acids by chloridazon-degrading bacteria. Combination of side chain degradation and dioxygenase pathway].

    PubMed

    Wegst, W; Lingens, F

    1981-09-01

    Strain N of Chloridazon-degrading bacteria degrades phenylalanine via cis-2,3-dihydro-2,3-dihydroxyphenylalanine,2,3-dihydroxyphenylalanine aspartate and 4-hydroxy-2-oxovalerate [Hoppe-Seyler's Z. Physiol. Chem. 360, 957--969, (1979); Biochem. J. 194, 679--684 (1981)]. cis-2,3-Dihydro-2,3-dihydroxyphenylalanine and 2,3-dihydroxyphenylalanine as well as phenylpyruvate, cis-2,3-dihydro-2,3-dihydroxyphenylpyruvate, 2,3-dihydroxyphenylpyruvate, cis-2,3-dihydro-2,3-dihydroxyphenylacetate, 2,3-dihydroxyphenylacetate and 2,3-dihydroxybenzaldehyde are detectable in the medium of strain E during growth on phenylalanine. Incubation with phenylacetate, 3-phenylpropionate or 4-phenylbutyrate leads to the accumulation of the corresponding cis-2,3-dihydro-2,3-dihydroxyphenyl derivatives. These compounds are transformed with dihydrodiol dehydrogenase to 2,3-dihydroxyphenylacetate, 3-(2,3-dihydroxyphenyl)propionate and 4-(2,3-dihydroxyphenyl)-butyrate, 3-(2,3-dihydroxyphenyl)propionate is attacked by a catechol 2,3-dioxygenase and the meta-cleavage product is again cleaved by a hydrolase yielding succinate. In a similar reaction sequence the degradation of 4-phenylbutyrate leads to the formation of glutarate. From the growth medium of strain E on phenylacetate also small amounts of 2-, 3- and 4-hydroxyphenylacetate were isolated. Resting cells were shown to metabolize 3- and 4-hydroxyphenylacetate via homogentisate and 3,4-dihydroxyphenylacetate. In the culture medium of strain K2AP benzoate could be detected. Pathways for the degradation of phenylalanine and aromatic carboxylic acids in chloridazon degrading bacteria are proposed.

  6. Combining chemical and isotopic measurements to estimate pesticide degradation rates in a fractured-rock aquifer

    NASA Astrophysics Data System (ADS)

    Farlin, Julien; Gallé, Tom; Bayerle, Michael; Pittois, Denis; El-Khabbaz, Hassanya; Schreglmann, Kathrin; Höche, Martina; Elsner, Martin

    2013-04-01

    Encouraged by new regulatory requirements for pesticide registration and authorization, the transport and environmental fate of these compounds in the different environmental compartments has been studied extensively. Degradation rates vary widely depending on hydraulic and chemical characteristics, with the strongest degradation usually occuring in the topsoil. Nonetheless, significant pesticide attenuation may still take place during transport in the aquifer, since residence times are generally much longer than in the soil. Ideally, pesticide transformation in the aquifer needs to be determined under real field conditions. Mass balance calculations however are complicated by the fact that the initial pesticide mass leached from the soil is often not known precisely enough. In this study, isotopic and classical pesticide concentration measurements were combined with groundwater dating techniques to assess the degradation rate of atrazine and its metabolite desethylatrazine in a fractured sandstone. The mass balance problem was solved by introducing the desethylatrazine to atrazine ratio, a relative measure which was used to quantify the advancement of atrazine degradation with increasing transport time in the subsurface. The extent of transformation of the parent compound was finally estimated from the shift in the isotopic signal between soil application and the outlet of the groundwater system.

  7. Model of radiation-induced gain degradation of NPN bipolar junction transistor at different dose rates

    NASA Astrophysics Data System (ADS)

    Qifeng, Zhao; Yiqi, Zhuang; Junlin, Bao; Wei, Hu

    2015-06-01

    Ionizing-radiation-induced current gain degradation in NPN bipolar junction transistors is due to an increase in base current as a result of recombination at the surface of the device. A model is presented which identifies the physical mechanism responsible for current gain degradation. The increase in surface recombination velocity due to interface states results in an increase in base current. Besides, changing the surface potential along the base surface induced by the oxide-trapped charges can also lead to an increased base current. By combining the production mechanisms of oxide-trapped charges and interface states, this model can explain the fact that the current gain degradation is more severe at a low dose rate than at a high dose rate. The radiations were performed in a Co60 source up to a total dose of 70 krad(Si). The low dose rate was 0.1 rad(Si)/s and the high dose rate was 10 rad(Si)/s. The model accords well with the experimental results. Project supported by the National Natural Science Foundation of China (Nos. 61076101, 61204092).

  8. Radiation-induced 1/f noise degradation of PNP bipolar junction transistors at different dose rates

    NASA Astrophysics Data System (ADS)

    Qi-Feng, Zhao; Yi-Qi, Zhuang; Jun-Lin, Bao; Wei, Hu

    2016-04-01

    It is found that ionizing-radiation can lead to the base current and the 1/f noise degradations in PNP bipolar junction transistors. In this paper, it is suggested that the surface of the space charge region of the emitter-base junction is the main source of the base surface 1/f noise. A model is developed which identifies the parameters and describes their interactive contributions to the recombination current at the surface of the space charge region. Based on the theory of carrier number fluctuation and the model of surface recombination current, a 1/f noise model is developed. This model suggests that 1/f noise degradations are the result of the accumulation of oxide-trapped charges and interface states. Combining models of ELDRS, this model can explain the reason why the 1/f noise degradation is more severe at a low dose rate than at a high dose rate. The radiations were performed in a Co60 source up to a total dose of 700 Gy(Si). The low dose rate was 0.001 Gy(Si)/s and the high dose rate was 0.1 Gy(Si)/s. The model accords well with the experimental results. Project supported by the National Natural Science Foundation of China (Grant Nos. 61076101 and 61204092).

  9. Efficient treatment of perfluorohexanoic acid by nanofiltration followed by electrochemical degradation of the NF concentrate.

    PubMed

    Soriano, Álvaro; Gorri, Daniel; Urtiaga, Ane

    2017-04-01

    The present study was aimed at the development of a strategy for removing and degrading perfluorohexanoic acid (PFHxA) from industrial process waters at concentrations in the range 60-200 mg L(-1). The treatment train consisted of nanofiltration (NF) separation followed by electrochemical degradation of the NF concentrate. Using a laboratory-scale system and working in the total recirculation mode, the DowFilm NF270 membrane provided PFHxA rejections that varied in the range 96.6-99.4% as the operating pressure was increased from 2.5 to 20 bar. The NF operation in concentration mode enabled a volume reduction factor of 5 and increased the PFHxA concentration in the retentate to 870 mg L(-1). Results showed that the increase in PFHxA concentration and the presence of calcium sulfate salts did not induce irreversible membrane fouling. The NF retentate was treated in a commercial undivided electrochemical cell provided with two parallel flow-by compartments separated by bipolar boron doped diamond (BDD) electrode, BDD counter anode, and counter cathode. Current densities ranging from 20 to 100 A m(-2) were examined. The electrochemical degradation rate of PFHxA reached 98% and was accompanied by its efficient mineralization, as the reduction of total organic carbon was higher than 95%. Energy consumption, which was 15.2 kWh m(-3) of treated NF concentrate, was minimized by selecting operation at 50 A m(-2). While most of the previous research on the treatment of perfluoroalkyl substances (PFASs) focused on the removal of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), these compounds have been phased out by chemical manufacturers. Our findings are relevant for the treatment of PFHxA, which appears to be one of the present alternatives to long-chain PFASs thanks to its lower bioaccumulative potential than PFOA and PFOS. However, PFHxA also behaves as a persistent pollutant. Moreover, our results highlight the potential of combining

  10. Comparative Genomics of Syntrophic Branched-Chain Fatty Acid Degrading Bacteria

    PubMed Central

    Narihiro, Takashi; Nobu, Masaru K.; Tamaki, Hideyuki; Kamagata, Yoichi; Sekiguchi, Yuji; Liu, Wen-Tso

    2016-01-01

    The syntrophic degradation of branched-chain fatty acids (BCFAs) such as 2-methylbutyrate and isobutyrate is an essential step in the production of methane from proteins/amino acids in anaerobic ecosystems. While a few syntrophic BCFA-degrading bacteria have been isolated, their metabolic pathways in BCFA and short-chain fatty acid (SCFA) degradation as well as energy conservation systems remain unclear. In an attempt to identify these pathways, we herein performed comparative genomics of three syntrophic bacteria: 2-methylbutyrate-degrading “Syntrophomonas wolfei subsp. methylbutyratica” strain JCM 14075T (=4J5T), isobutyrate-degrading Syntrophothermus lipocalidus strain TGB-C1T, and non-BCFA-metabolizing S. wolfei subsp. wolfei strain GöttingenT. We demonstrated that 4J5 and TGB-C1 both encode multiple genes/gene clusters involved in β-oxidation, as observed in the Göttingen genome, which has multiple copies of genes associated with butyrate degradation. The 4J5 genome possesses phylogenetically distinct β-oxidation genes, which may be involved in 2-methylbutyrate degradation. In addition, these Syntrophomonadaceae strains harbor various hydrogen/formate generation systems (i.e., electron-bifurcating hydrogenase, formate dehydrogenase, and membrane-bound hydrogenase) and energy-conserving electron transport systems, including electron transfer flavoprotein (ETF)-linked acyl-CoA dehydrogenase, ETF-linked iron-sulfur binding reductase, ETF dehydrogenase (FixABCX), and flavin oxidoreductase-heterodisulfide reductase (Flox-Hdr). Unexpectedly, the TGB-C1 genome encodes a nitrogenase complex, which may function as an alternative H2 generation mechanism. These results suggest that the BCFA-degrading syntrophic strains 4J5 and TGB-C1 possess specific β-oxidation-related enzymes for BCFA oxidation as well as appropriate energy conservation systems to perform thermodynamically unfavorable syntrophic metabolism. PMID:27431485

  11. Epoxy ceriporic acid produced by selective lignin-degrading fungus Ceriporiopsis subvermispora.

    PubMed

    Nishimura, Hiroshi; Setogawa, Yuichi; Watanabe, Takahito; Honda, Yoichi; Watanabe, Takashi

    2011-11-01

    Ceriporiopsis subvermispora is a selective white rot basidiomycete which degrades lignin in wood at a distance far from enzymes. Low molecular mass metabolites play a central role in the oxidative degradation of lignin. To understand the unique wood-decaying mechanism, we surveyed the oxidized derivatives of ceriporic acids (alk(en)ylitaconic acids) produced by C. subvermispora using high-resolution liquid chromatography multiple-stage mass spectrometry (HR-LC/MS(n)). The analysis of the precursor and product ions from the extract suggested that an epoxidized derivative of ceriporic acid is produced by the fungus. To identify the new metabolite, an authentic compound of ceriporic acid epoxide was synthesized in vitro by reacting (R)-3-[(Z)-hexadec-7-enyl]-itaconic acid (ceriporic acid C) with m-chloroperbenzoic acid. The precursor and product ions from the natural metabolite and authentic epoxide were identical and distinguishable from those of hydroxy and hydroperoxy derivatives after reduction with NaBD(4). Feeding experiments with [U-(13)C]-glucose, 99% and the subsequent analyses of the first and second generation product ions demonstrated that the oxidized ceriporic acid was (R)-3-(7,8-epoxy-hexadecyl)-itaconic acid. To our knowledge, this study is the first to report that natural alkylitaconic acid bears an epoxy group on its side chain.

  12. Genome Sequence Analysis of the Naphthenic Acid Degrading and Metal Resistant Bacterium Cupriavidus gilardii CR3

    PubMed Central

    Xiao, Jingfa; Hao, Lirui; Crowley, David E.; Zhang, Zhewen; Yu, Jun; Huang, Ning; Huo, Mingxin; Wu, Jiayan

    2015-01-01

    Cupriavidus sp. are generally heavy metal tolerant bacteria with the ability to degrade a variety of aromatic hydrocarbon compounds, although the degradation pathways and substrate versatilities remain largely unknown. Here we studied the bacterium Cupriavidus gilardii strain CR3, which was isolated from a natural asphalt deposit, and which was shown to utilize naphthenic acids as a sole carbon source. Genome sequencing of C. gilardii CR3 was carried out to elucidate possible mechanisms for the naphthenic acid biodegradation. The genome of C. gilardii CR3 was composed of two circular chromosomes chr1 and chr2 of respectively 3,539,530 bp and 2,039,213 bp in size. The genome for strain CR3 encoded 4,502 putative protein-coding genes, 59 tRNA genes, and many other non-coding genes. Many genes were associated with xenobiotic biodegradation and metal resistance functions. Pathway prediction for degradation of cyclohexanecarboxylic acid, a representative naphthenic acid, suggested that naphthenic acid undergoes initial ring-cleavage, after which the ring fission products can be degraded via several plausible degradation pathways including a mechanism similar to that used for fatty acid oxidation. The final metabolic products of these pathways are unstable or volatile compounds that were not toxic to CR3. Strain CR3 was also shown to have tolerance to at least 10 heavy metals, which was mainly achieved by self-detoxification through ion efflux, metal-complexation and metal-reduction, and a powerful DNA self-repair mechanism. Our genomic analysis suggests that CR3 is well adapted to survive the harsh environment in natural asphalts containing naphthenic acids and high concentrations of heavy metals. PMID:26301592

  13. Genome Sequence Analysis of the Naphthenic Acid Degrading and Metal Resistant Bacterium Cupriavidus gilardii CR3.

    PubMed

    Wang, Xiaoyu; Chen, Meili; Xiao, Jingfa; Hao, Lirui; Crowley, David E; Zhang, Zhewen; Yu, Jun; Huang, Ning; Huo, Mingxin; Wu, Jiayan

    2015-01-01

    Cupriavidus sp. are generally heavy metal tolerant bacteria with the ability to degrade a variety of aromatic hydrocarbon compounds, although the degradation pathways and substrate versatilities remain largely unknown. Here we studied the bacterium Cupriavidus gilardii strain CR3, which was isolated from a natural asphalt deposit, and which was shown to utilize naphthenic acids as a sole carbon source. Genome sequencing of C. gilardii CR3 was carried out to elucidate possible mechanisms for the naphthenic acid biodegradation. The genome of C. gilardii CR3 was composed of two circular chromosomes chr1 and chr2 of respectively 3,539,530 bp and 2,039,213 bp in size. The genome for strain CR3 encoded 4,502 putative protein-coding genes, 59 tRNA genes, and many other non-coding genes. Many genes were associated with xenobiotic biodegradation and metal resistance functions. Pathway prediction for degradation of cyclohexanecarboxylic acid, a representative naphthenic acid, suggested that naphthenic acid undergoes initial ring-cleavage, after which the ring fission products can be degraded via several plausible degradation pathways including a mechanism similar to that used for fatty acid oxidation. The final metabolic products of these pathways are unstable or volatile compounds that were not toxic to CR3. Strain CR3 was also shown to have tolerance to at least 10 heavy metals, which was mainly achieved by self-detoxification through ion efflux, metal-complexation and metal-reduction, and a powerful DNA self-repair mechanism. Our genomic analysis suggests that CR3 is well adapted to survive the harsh environment in natural asphalts containing naphthenic acids and high concentrations of heavy metals.

  14. Photocatalytic degradation of L-acid by TiO2 supported on the activated carbon.

    PubMed

    Wang, Yu-Ping; Wang, Lian-Jun; Peng, Pan-Ying

    2006-01-01

    TiO2 sol was prepared by sol-gel technique with tetrabutyl titanate as precursor. Supported TiO2 catalysts on activated carbon were prepared by soak and sintering method. The aggregation of nano-TiO2 particles can be effectively suppressed by added polyethylene glycol (PEG) as a surface modifier. The average particle diameter of TiO2, specific surface area and absorbability of catalyst can be modified. Based on characteristics of the TiO2 photocatalyst with XRD, specific surface area, adsorption valves of methylene blue and the amount of TiO2 supported on the activated carbon, the photocatalytic degradation of L-acid was studied. The effect of the factors, such as pH of the solution, the initial concentration of L-acid on the photocatalytic degradation of L-acid, were studied also. It was found that when the pH of the solution is 1.95, the amount of photocatalyst is 0.5 g, the concentration of the L-acid solution is 1.34 x 10(-3) mol/L and the illumination time is 7 h, the photocatalytic degradation efficiency of L-acid can reach 89.88%. The catalyst was reused 6 times and its degradation efficiency hardly changed.

  15. [Photocatalytic Degradation of Perfluorooctanoic Acid by Pd-TiO2 Photocatalyst].

    PubMed

    Liu, Qing; Yu, Ze-bin; Zhang, Rui-han; Li, Ming-jie; Chen, Ying; Wang, Li; Kuang, Yu; Zhang, Bo; Zhu, You-hui

    2015-06-01

    Perfluorooctanoic acid (PFOA) is a new persistent organic pollutant which has got global concern for its wide distribution, high bioaccumulation and strong biological toxicity. In present study, the photocatalytic degradation of PFOA using palladium doped TiO2 (Pd-TiO2) prepared by chemical reduction method was investigated. The photocatalysts were characterized by XRD, FESEM and UV-vis DRS and were used for PFOA degradation under 365 nm UV irradiation. The results indicated that the grain size of TiO2 was smaller while the specific surface area increased and the absorption of ultraviolet light also enhanced after using chemical reduction method, but all these changes had no influence on PFOA degradation. However, the degradation was significantly enhanced because of the deposition of Pd, the fluoride concentration of PFOA was 6.62 mg x L(-1) after 7 h irradiation which was 7.3 times higher than that of TiO2 (P25). Experiments with the addition of trapping agent and nitrogen indicated that *OH played an important role in PFOA degradation while the presence of O2 accelerated the degradation. The main intermediate products of photocatalytic degradation of PFOA were authenticated by an ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry systems (UPLC-QTOF-MS). The probable photocatalytic degradation mechanism involves h+ attacking the carboxyl of PFOA and resulting in decarboxylation. The produced *CnF(2n +1) was oxidized by *OH underwent defluorinetion to form shorter-chain perfluorinated carboxylic acids. The significant enhancement of PFOA degradation can be ascribed to the palladium deposits, acting as electron traps on the Pd-TiO2 surface, which facilitated the transfer of photogenerated electrons and retarded the accumulation of electrons.

  16. OH-radical induced degradation of hydroxybenzoic- and hydroxycinnamic acids and formation of aromatic products—A gamma radiolysis study

    NASA Astrophysics Data System (ADS)

    Krimmel, Birgit; Swoboda, Friederike; Solar, Sonja; Reznicek, Gottfried

    2010-12-01

    The OH-radical induced degradation of hydroxybenzoic acids (HBA), hydroxycinnamic acids (HCiA) and methoxylated derivatives, as well as of chlorogenic acid and rosmarinic acid was studied by gamma radiolysis in aerated aqueous solutions. Primary aromatic products resulting from an OH-radical attachment to the ring (hydroxylation), to the position occupied by the methoxyl group (replacement -OCH 3 by -OH) as well as to the propenoic acid side chain of the cinnamic acids (benzaldehyde formations) were analysed by HPLC-UV and LC-ESI-MS. A comparison of the extent of these processes is given for 3,4-dihydroxybenzoic acid, vanillic acid, isovanillic acid, syringic acid, cinnamic acid, 4-hydroxycinnamic acid, caffeic acid, ferulic acid, isoferulic acid, chlorogenic acid, and rosmarinic acid. For all cinnamic acids and derivatives benzaldehydes were significant oxidation products. With the release of caffeic acid from chlorogenic acid the cleavage of a phenolic glycoside could be demonstrated. Reaction mechanisms are discussed.

  17. Biostimulation of PAH degradation with plants containing high concentrations of linoleic acid.

    PubMed

    Yi, Haakrho; Crowley, David E

    2007-06-15

    Many plant species enhance the biodegradation of polycyclic aromatic hydrocarbons (PAHs), but there is little understanding of the mechanisms by which this occurs. This research identified phytochemicals that stimulate pyrene degradation using crushed roottissues from 43 plants that were screened in soil spiked with 100 ppm pyrene. Among the plants tested, root tissues from Apium graveolens (celery), Raphanus sativus (radish), Solanum tuberosum (potato), and Daucus carota (carrot) were most effective for promoting disappearance of pyrene within 40 days. Experiments with A. graveolens showed that plant culture in soil contaminated with pyrene or benzo[a]pyrene was as effective as addition of crushed root tissues. Comparison of the chemical compositions of the effective plants suggested that linoleic acid was the major substance that stimulated PAH degradation. This hypothesis was supported in experiments examining degradation of pyrene and benzo[a]pyrene in soil amended with linoleate, whereas linolenic and palmitic acids did not stimulate degradation within a 20 day period. Antibiotic inhibitor studies implicated gram positive bacteria as a predominant group responding to linoleic acid. These findings provide insight into the mechanisms by which plants enhance degradation of PAHs, and have practical application for remediation of PAH contaminated soils.

  18. Relationship of Bacterial Richness to Organic Degradation Rate and Sediment Age in Subseafloor Sediment

    PubMed Central

    Walsh, Emily A.; Kirkpatrick, John B.; Pockalny, Robert; Sauvage, Justine; Spivack, Arthur J.; Murray, Richard W.; Sogin, Mitchell L.

    2016-01-01

    ABSTRACT Subseafloor sediment hosts a large, taxonomically rich, and metabolically diverse microbial ecosystem. However, the factors that control microbial diversity in subseafloor sediment have rarely been explored. Here, we show that bacterial richness varies with organic degradation rate and sediment age. At three open-ocean sites (in the Bering Sea and equatorial Pacific) and one continental margin site (Indian Ocean), richness decreases exponentially with increasing sediment depth. The rate of decrease in richness with increasing depth varies from site to site. The vertical succession of predominant terminal electron acceptors correlates with abundance-weighted community composition but does not drive the vertical decrease in richness. Vertical patterns of richness at the open-ocean sites closely match organic degradation rates; both properties are highest near the seafloor and decline together as sediment depth increases. This relationship suggests that (i) total catabolic activity and/or electron donor diversity exerts a primary influence on bacterial richness in marine sediment and (ii) many bacterial taxa that are poorly adapted for subseafloor sedimentary conditions are degraded in the geologically young sediment, where respiration rates are high. Richness consistently takes a few hundred thousand years to decline from near-seafloor values to much lower values in deep anoxic subseafloor sediment, regardless of sedimentation rate, predominant terminal electron acceptor, or oceanographic context. IMPORTANCE Subseafloor sediment provides a wonderful opportunity to investigate the drivers of microbial diversity in communities that may have been isolated for millions of years. Our paper shows the impact of in situ conditions on bacterial community structure in subseafloor sediment. Specifically, it shows that bacterial richness in subseafloor sediment declines exponentially with sediment age, and in parallel with organic-fueled oxidation rate. This result

  19. Degradation kinetic modelling of ascorbic acid and colour intensity in pasteurised blood orange juice during storage.

    PubMed

    Remini, Hocine; Mertz, Christian; Belbahi, Amine; Achir, Nawel; Dornier, Manuel; Madani, Khodir

    2015-04-15

    The stability of ascorbic acid and colour intensity in pasteurised blood orange juice (Citrus sinensis [L.] Osbeck) during one month of storage was investigated at 4-37 °C. The effects of ascorbic acid fortification (at 100, 200 mg L(-1)) and deaeration, temperature/time storage on the kinetic behaviour were determined. Ascorbic acid was monitored by HPLC-DAD and colour intensity by spectrophotometric measurements. Degradation kinetics were best fitted by first-order reaction models for both ascorbic acid and colour intensity. Three models (Arrhenius, Eyring and Ball) were used to assess the temperature-dependent degradation. Following the Arrhenius model, activation energies were ranged from 51 to 135 kJ mol(-1) for ascorbic acid and from 49 to 99 kJ mol(-1) for colour intensity. The effect of storage temperature and deaeration are the most influent factors on kinetics degradation, while the fortification revealed no significant effect on ascorbic acid content and colour intensity.

  20. Effects of acid extrusion on the degradability of maize distillers dried grain with solubles in pigs.

    PubMed

    de Vries, S; Pustjens, A M; van Rooijen, C; Kabel, M A; Hendriks, W H; Gerrits, W J J

    2014-12-01

    Commonly used feed processing technologies are not sufficient to affect recalcitrant nonstarch polysaccharides (NSP) such as arabinoxylans present in maize distillers dried grain with solubles (DDGS). Instead, hydrothermal treatments combined with acid catalysts might be more effective to modify these NSP. The objective of this experiment was to investigate the effects of hydrothermal maleic acid treatment (acid extrusion) on the degradability of maize DDGS in growing pigs. It was hypothesized that acid extrusion modifies DDGS cell wall architecture and thereby increases fermentability of NSP. Two diets, containing either 40% (wt/wt) unprocessed or acid-extruded DDGS, were restrictedly fed to groups of gilts (n=11, with 4 pigs per group; initial mean BW: 20.8±0.2 kg) for 18 d and performance and digestibility were analyzed. Acid extrusion tended to decrease apparent ileal digestibility (AID) of CP (approximately 3 percentage units [% units]); P=0.063) and starch (approximately 1% unit; P=0.096). Apparent digestibility of CP and starch measured at the mid colon (2% units, P=0.030, for CP and 0.3% units, P<0.01, for starch) and apparent total tract digestibility (ATTD; 3% units, P<0.01, for CP and 0.2% units, P=0.024, for starch) were lower for the acid-extruded diet compared with the control diet. Hindgut disappearance was, however, not different between diets, indicating that reduced CP and starch digestibility were mainly due to decreased AID. Acid extrusion tended to increase AID of NSP (6% units; P=0.092) and increased digestibility of NSP measured at the mid colon (6% units; P<0.01), whereas hindgut disappearance and ATTD of NSP did not differ between diets. Greater NSP digestibility was mainly due to greater digestibility of arabinosyl, xylosyl, and glucosyl residues, indicating that both arabinoxylan and cellulose degradability were affected by acid extrusion. In conclusion, these results show that acid extrusion did not improve degradation of DDGS for

  1. Mechanistic Study of the Acid Degradation of Lignin Model Compounds

    SciTech Connect

    Sturgeon, M.; Kim, S.; Chmely, S. C.; Foust, T. D.; Beckham, G. T.

    2012-01-01

    Lignin is a major constituent of biomass, which remains underutilized in selective biomass conversion strategies to renewable fuels and chemicals. Here we are interested in understanding the mechanisms related to the acid deconstruction of lignin with a combined theoretical and experimental approach. Two model dimers with a b-O-4 aryl ether linkage (2-phenoxy-1-phenethanol and 2-phenoxy-1-phenyl-1,3 propanediol) and model dimmers with an a-O-4 aryl ether linkage were synthesized and deconstructed in H2SO4. The major products of the acidolysis of the b-O-4 compounds consisted of phenol and two aldehydes, phenylacetaldehyde and benzaldehyde. Quantum mechanical calculations were employed to elucidate possible deconstruction mechanisms with transition state theory. To confirm proposed mechanisms several possible intermediates were studied under similar acidolysis conditions. Although the resonance time for cleavage was on the order several hours, we have shown that the cleavage of the aryl ether linkage affords phenol and aldehydes. We would next like to utilize our mechanism of aryl ether cleavage in actual lignin.

  2. Cathepsin B-sensitive polymers for compartment-specific degradation and nucleic acid release

    PubMed Central

    Chu, David S.H.; Johnson, Russell N.; Pun, Suzie H.

    2011-01-01

    Degradable cationic polymers are desirable for in vivo nucleic acid delivery because they offer significantly decreased toxicity over non-degradable counterparts. Peptide linkers provide chemical stability and high specificity for particular endopeptidases but have not been extensively studied for nucleic acid delivery applications. In this work, enzymatically degradable peptide-HPMA copolymers were synthesized by RAFT polymerization of HPMA with methacrylated peptide macromonomers, resulting in polymers with low polydispersity and near quantitative incorporation of peptides. Three peptide-HPMA copolymers were evaluated: (i) pHCathK10, containing peptides composed of the linker phe-lys-phe-leu (FKFL), a substrate of the endosomal/lysosomal endopeptidase cathepsin B, connected to oligo-(l)-lysine for nucleic acid binding, (ii) pHCath(d)K10, containing the FKFL linker with oligo-(d)-lysine, and (iii) pH(d)Cath(d)K10, containing all (d) amino acids. Cathepsin B degraded copolymers pHCathK10 and pHCath(d)K10 within one hour while no degradation of pH(d)Cath(d)K10 was observed. Polyplexes formed with pHCathK10 copolymers show DNA release by 4 hrs of treatment with cathepsin B; comparatively, polyplexes formed with pHCath(d)K10 and pH(d)Cath(d)K10 show no DNA release within 8 hrs. Transfection efficiency in HeLa and NIH/3T3 cells were comparable between the copolymers but pHCathK10 was less toxic. This work demonstrates the successful application of peptide linkers for degradable cationic polymers and DNA release. PMID:22036879

  3. Humic acid degradation by the synthesized flower-like Ag/ZnO nanostructure as an efficient photocatalyst.

    PubMed

    Ghaneian, Mohammad Taghi; Morovati, Pouran; Ehrampoush, Mohammad Hassan; Tabatabaee, Masoumeh

    2014-01-01

    Nano-sized flower-like Ag/ZnO was synthesized by a simple method using zinc acetate and silver acetate under hydrothermal condition. Powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM) were used to characterize the structure and morphology of the synthesized powder. Nano flower-like Ag/ZnO was used as a photocatalyst for degradation of humic acid in aqueous solution. The disappearance of HA was analyzed by measuring the absorbance of sample at special wavelength (254 nm). The effects of various parameters such as amount of photocatalyst, pH, initial humic acid concentration and irradiation time on degradation rate were systematically investigated. Photodegradation efficiency was small when the photolysis was carried out in the absence of Ag/ZnO and it was also negligible in the absence of light. Approximately 70% of humic acid (50 mg/L) has been eliminated after 40 minutes in the presences of catalyst (catalyst dose o.6 g/L and pH =7) and UVA irradiation. While, 100% of humic acid has been eliminated with solar irradiation.

  4. Penetration of hydrogen peroxide and degradation rate of different bleaching products.

    PubMed

    Marson, F C; Gonçalves, R S; Silva, C O; Cintra, L T Â; Pascotto, R C; Santos, P H Dos; Briso, A L F

    2015-01-01

    This study's aim was to evaluate the degradation rate of hydrogen peroxide (H2O2) and to quantify its penetration in tooth structure, considering the residence time of bleaching products on the dental enamel. For this study, bovine teeth were randomly divided according to the bleaching product received: Opalescence Xtra Boost 38%, White Gold Office 35%, Whiteness HP Blue 35%, Whiteness HP Maxx 35%, and Lase Peroxide Sensy 35%. To analyze the degradation of H2O2, the titration of bleaching agents with potassium permanganate was used, while the penetration of H2O2 was measured via spectrophotometric analysis of the acetate buffer solution, collected from the artificial pulp chamber. The analyses were performed immediately as well as 15 minutes, 30 minutes, and 45 minutes after product application. The data of degradation rate of H2O2 were submitted to analysis of variance (ANOVA) and Tukey tests, while ANOVA and Fisher tests were used for the quantification of H2O2, at the 5% level. The results showed that all products significantly reduced the concentration of H2O2 activates at the end of 45 minutes. It was also verified that the penetration of H2O2 was enhanced by increasing the residence time of the product on the tooth surface. It was concluded that the bleaching gels retained substantial concentrations of H2O2 after 45 minutes of application, and penetration of H2O2 in the dental structure is time-dependent.

  5. Degradation Network Reconstruction in Uric Acid and Ammonium Amendments in Oil-Degrading Marine Microcosms Guided by Metagenomic Data.

    PubMed

    Bargiela, Rafael; Gertler, Christoph; Magagnini, Mirko; Mapelli, Francesca; Chen, Jianwei; Daffonchio, Daniele; Golyshin, Peter N; Ferrer, Manuel

    2015-01-01

    Biostimulation with different nitrogen sources is often regarded as a strategy of choice in combating oil spills in marine environments. Such environments are typically depleted in nitrogen, therefore limiting the balanced microbial utilization of carbon-rich petroleum constituents. It is fundamental, yet only scarcely accounted for, to analyze the catabolic consequences of application of biostimulants. Here, we examined such alterations in enrichment microcosms using sediments from chronically crude oil-contaminated marine sediment at Ancona harbor (Italy) amended with natural fertilizer, uric acid (UA), or ammonium (AMM). We applied the web-based AromaDeg resource using as query Illumina HiSeq meta-sequences (UA: 27,893 open reading frames; AMM: 32,180) to identify potential catabolic differences. A total of 45 (for UA) and 65 (AMM) gene sequences encoding key catabolic enzymes matched AromaDeg, and their participation in aromatic degradation reactions could be unambiguously suggested. Genomic signatures for the degradation of aromatics such as 2-chlorobenzoate, indole-3-acetate, biphenyl, gentisate, quinoline and phenanthrene were common for both microcosms. However, those for the degradation of orcinol, ibuprofen, phenylpropionate, homoprotocatechuate and benzene (in UA) and 4-aminobenzene-sulfonate, p-cumate, dibenzofuran and phthalate (in AMM), were selectively enriched. Experimental validation was conducted and good agreement with predictions was observed. This suggests certain discrepancies in action of these biostimulants on the genomic content of the initial microbial community for the catabolism of petroleum constituents or aromatics pollutants. In both cases, the emerging microbial communities were phylogenetically highly similar and were composed by very same proteobacterial families. However, examination of taxonomic assignments further revealed different catabolic pathway organization at the organismal level, which should be considered for designing

  6. Degradation Network Reconstruction in Uric Acid and Ammonium Amendments in Oil-Degrading Marine Microcosms Guided by Metagenomic Data

    PubMed Central

    Bargiela, Rafael; Gertler, Christoph; Magagnini, Mirko; Mapelli, Francesca; Chen, Jianwei; Daffonchio, Daniele; Golyshin, Peter N.; Ferrer, Manuel

    2015-01-01

    Biostimulation with different nitrogen sources is often regarded as a strategy of choice in combating oil spills in marine environments. Such environments are typically depleted in nitrogen, therefore limiting the balanced microbial utilization of carbon-rich petroleum constituents. It is fundamental, yet only scarcely accounted for, to analyze the catabolic consequences of application of biostimulants. Here, we examined such alterations in enrichment microcosms using sediments from chronically crude oil-contaminated marine sediment at Ancona harbor (Italy) amended with natural fertilizer, uric acid (UA), or ammonium (AMM). We applied the web-based AromaDeg resource using as query Illumina HiSeq meta-sequences (UA: 27,893 open reading frames; AMM: 32,180) to identify potential catabolic differences. A total of 45 (for UA) and 65 (AMM) gene sequences encoding key catabolic enzymes matched AromaDeg, and their participation in aromatic degradation reactions could be unambiguously suggested. Genomic signatures for the degradation of aromatics such as 2-chlorobenzoate, indole-3-acetate, biphenyl, gentisate, quinoline and phenanthrene were common for both microcosms. However, those for the degradation of orcinol, ibuprofen, phenylpropionate, homoprotocatechuate and benzene (in UA) and 4-aminobenzene-sulfonate, p-cumate, dibenzofuran and phthalate (in AMM), were selectively enriched. Experimental validation was conducted and good agreement with predictions was observed. This suggests certain discrepancies in action of these biostimulants on the genomic content of the initial microbial community for the catabolism of petroleum constituents or aromatics pollutants. In both cases, the emerging microbial communities were phylogenetically highly similar and were composed by very same proteobacterial families. However, examination of taxonomic assignments further revealed different catabolic pathway organization at the organismal level, which should be considered for designing

  7. 1,3-Dinitrobenzene reductive degradation by alkaline ascorbic acid - Reaction mechanisms, degradation pathways and reagent optimization.

    PubMed

    Ciou, Chiya; Liang, Chenju

    2017-01-01

    Nitro-aromatic compounds (NACs) such as 1,3-dinitrobenzene (1,3-DNB) contain the nitrogroup (-NO2), in which the N with a +III oxidation state accepts electrons. Water soluble ascorbic acid (AsA) at elevated pH produces electron transfer and governs the electron-donating pathway. The influence of the NaOH/AsA molar ratio on the degradation of 1,3-DNB was investigated. Using 0.21-2 M NaOH and 20-100 mM AsA, nearly complete 1,3-DNB removals (90-100%) were achieved within 0.5 h. On the basis of intermediates identified using GC/MS, the reduction pathways of 1,3-DNB can be categorized into step-by-step electron transfer, and condensation routes. A higher NaOH/AsA molar ratio would result in relatively higher AsA decomposition, promote the condensation route into the formation of azo- and azoxy-compounds, and ultimately reduce 1,3-DNB to 1,3-phenylenediamine. Contaminated soil flushing using 500 mM NaOH/100 mM AsA revealed that 1,3-DNB was completely degraded within 2 h. Based on these test results, the alkaline AsA treatment method is a potential remediation process for NACs contaminated soils.

  8. Rate limiting factors in trichloroethylene co-metabolic degradation by phenol-grown aerobic granules.

    PubMed

    Zhang, Yi; Tay, Joo Hwa

    2014-04-01

    The potential of aerobic granular sludge in co-metabolic removal of recalcitrant substances was evaluated using trichloroethylene (TCE) as the model compound. Aerobic granules cultivated in a sequencing batch reactor with phenol as the growth substrate exhibited TCE and phenol degradation activities lower than previously reported values. Depletion of reducing energy and diffusion limitation within the granules were investigated as the possible rate limiting factors. Sodium formate and citrate were supplied to the granules in batch studies as external electron sources. No significant enhancing effect was observed on the instant TCE transformation rates, but 10 mM formate could improve the ultimate transformation capacity by 26 %. Possible diffusion barrier was studied by sieving the biomass into five size fractions, and determining their specific TCE and phenol degradation rates and capacities. Biomass in the larger size fractions generally showed lower activities. Large granules of >700 μm diameter exhibited only 22 % of the flocs' TCE transformation capacity and 35 % of its phenol dependent SOUR, indicating the possible occurrence of diffusion limitation in larger biomass. However, the highest specific TCE transformation rate was observed with the fraction that mostly consisted of small granules (150-300 μm), suggesting an optimal size range while applying aerobic granules in TCE co-metabolic removal.

  9. Cellular Site in Bacillus subtilis of a Nuclease Which Preferentially Degrades Single-Stranded Nucleic Acids

    PubMed Central

    Birnboim, H. C.

    1966-01-01

    Birnboim, H. C. (Albert Einstein College of Medicine, New York, N.Y.). Cellular site in Bacillus subtilis of a nuclease which preferentially degrades single-stranded nucleic acids. J. Bacteriol. 91:1004–1011. 1966.—A nuclease, identified by a marked preference for single-stranded nucleic acids, has been demonstrated in extracts of Bacillus subtilis. The enzyme was associated with the cell wall-membrane fraction of mechanically disrupted cells and was released from cells which had been converted to protoplasts by lysozyme. The nuclease activity prepared by the latter procedure was found to be activated and solubilized by treatment with trypsin. The enzyme had about 2% activity on native deoxyribonucleic acid (DNA) as compared with denatured DNA. By use of CsCl analytical density gradient ultracentrifugation, this preparation was shown to degrade denatured DNA selectively in mixtures of native and denatured DNA. PMID:4956329

  10. Sulfate radical-induced degradation of Acid Orange 7 by a new magnetic composite catalyzed peroxymonosulfate oxidation process.

    PubMed

    Chen, Dan; Ma, Xiaolong; Zhou, Jizhi; Chen, Xi; Qian, Guangren

    2014-08-30

    We synthesized a novel magnetic composite, Fe3O4/Cu(Ni)Cr-LDH, as a heterogeneous catalyst for the degradation of organic dyes in the solution using sulfate radical-based advanced oxidation processes. The physicochemical properties of the composite synthesized via two-step microwave hydrothermal method were characterized by several techniques, such as X-ray diffraction (XRD), inductively coupled plasma (ICP), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The degradation tests were performed at 25°C with Acid Orange 7 (AO7) initial concentration of 25mg/L and AO7/peroxymonosulfate (PMS) molar ratio of 1:10, which showed that the complete degradation by Fe3O4/Cu1.5Ni0.5Cr-LDH could be achieved and the mineralization rate could reach 46%. PMS was activated by Cu (II) and Fe (II/III) of Fe3O4/Cu(Ni)Cr-LDH to generate sulfate radicals (SO4(-)). Subsequently, the organic functional groups of AO7 molecules were destroyed by sulfate radicals (SO4(-)), inducing the degradation of AO7. Moreover, the catalytic behavior of the catalysts could be reused five times. Therefore, our work suggested that the Fe3O4/Cu(Ni)Cr-LDH composite could be applied widely for the treatment of organic dyes in wastewater.

  11. Determination of first-order degradation rate constants from monitoring networks.

    PubMed

    Beyer, Christof; Chen, Cui; Gronewold, Jan; Kolditz, Olaf; Bauer, Sebastian

    2007-01-01

    In this article, different strategies for estimating first-order degradation rate constants from measured field data are compared by application to multiple, synthetic, contaminant plumes. The plumes were generated by numerical simulation of contaminant transport and degradation in virtual heterogeneous aquifers. These sites were then individually and independently investigated on the computer by installation of extensive networks of observation wells. From the data measured at the wells, that is, contaminant concentrations, hydraulic conductivities, and heads, first-order degradation rates were estimated by three 1D centerline methods, which use only measurements located on the plume axis, and a two-dimensional method, which uses all concentration measurements available downgradient from the contaminant source. Results for both strategies show that the true rate constant used for the numerical simulation of the plumes in general tends to be overestimated. Overestimation is stronger for narrow plumes from small source zones, with an average overestimation factor of about 5 and single values ranging from 0.5 to 20, decreasing for wider plumes, with an average overestimation factor of about 2 and similar spread. Reasons for this overestimation are identified in the velocity calculation, the dispersivity parameterization, and off-centerline measurements. For narrow plumes, the one- and the two-dimensional strategies show approximately the same amount of overestimation. For wider plumes, however, incorporation of all measurements in the two-dimensional approach reduces the estimation error. No significant relation between the number of observation wells in the monitoring network and the quality of the estimated rate constant is found for the two-dimensional approach.

  12. Balancing sample accumulation and DNA degradation rates to optimize noninvasive genetic sampling of sympatric carnivores.

    PubMed

    Lonsinger, Robert C; Gese, Eric M; Dempsey, Steven J; Kluever, Bryan M; Johnson, Timothy R; Waits, Lisette P

    2015-07-01

    Noninvasive genetic sampling, or noninvasive DNA sampling (NDS), can be an effective monitoring approach for elusive, wide-ranging species at low densities. However, few studies have attempted to maximize sampling efficiency. We present a model for combining sample accumulation and DNA degradation to identify the most efficient (i.e. minimal cost per successful sample) NDS temporal design for capture-recapture analyses. We use scat accumulation and faecal DNA degradation rates for two sympatric carnivores, kit fox (Vulpes macrotis) and coyote (Canis latrans) across two seasons (summer and winter) in Utah, USA, to demonstrate implementation of this approach. We estimated scat accumulation rates by clearing and surveying transects for scats. We evaluated mitochondrial (mtDNA) and nuclear (nDNA) DNA amplification success for faecal DNA samples under natural field conditions for 20 fresh scats/species/season from <1-112 days. Mean accumulation rates were nearly three times greater for coyotes (0.076 scats/km/day) than foxes (0.029 scats/km/day) across seasons. Across species and seasons, mtDNA amplification success was ≥95% through day 21. Fox nDNA amplification success was ≥70% through day 21 across seasons. Coyote nDNA success was ≥70% through day 21 in winter, but declined to <50% by day 7 in summer. We identified a common temporal sampling frame of approximately 14 days that allowed species to be monitored simultaneously, further reducing time, survey effort and costs. Our results suggest that when conducting repeated surveys for capture-recapture analyses, overall cost-efficiency for NDS may be improved with a temporal design that balances field and laboratory costs along with deposition and degradation rates.

  13. Efficiency of uronic acid uptake in marine alginate-degrading fungi

    NASA Astrophysics Data System (ADS)

    Schaumann, K.; Weide, G.

    1995-03-01

    Despite the fact that many marine fungi, including phycomycetes, yeasts, ascomycetes and hyphomycetes, have been recorded from living and/or dead phaeophytes, only a few of these have been shown to be capable of degrading alginic acid or alginates. The degradation is achieved by the action of an exoenzyme complex, comprising alginate lyase, as well as alginate hydrolase activities. The latter was detected only recently by the authors. In this study, the growth of two marine sodiumalginate-degrading deuteromycetes, Asteromyces cruciatus and Dendryphiella salina, was investigated, and the assimilation efficiency of sodiumalginate and its uronic acid degradation products, respectively, was estimated from the economic coefficient (E). E is calculated from the mycelial dry weight, divided by the weight of substrate consumed for this production. The economic coefficient for A. cruciatus was 48.6%, and that of D. salina 38.9%. This indicates that the former species uses the alginate degradation products more efficiently than the latter. The observed E-values for the marine deuteromycetes agree with those from other fungi, e.g. terrestrial species. In general, it is concluded that the marine fungi appear to play a more important role in kelp-based ecosystems than was realized previously.

  14. Degradation of triclosan in the presence of p-aminobenzoic acid under simulated sunlight irradiation.

    PubMed

    Zhai, Pingping; Chen, Xuan; Dong, Wenbo; Li, Hongjing; Chovelon, Jean-Marc

    2017-01-01

    This study aimed to investigate the degradation of triclosan (TCS) in the presence of p-aminobenzoic acid (PABA) under simulated sunlight irradiation (λ ≥ 290 nm). The effect of PABA concentration, pH, dissolved organic matter (DOM), and DOM-hydrolytic Fe(III) species complexes on the photodegradation of TCS in the presence of PABA (TCS-PABA) was also studied. The photolysis of TCS-PABA obeyed pseudo-first-order kinetics well, and the degradation of TCS-PABA enhanced with increasing solution pH (from 3.0 to 11.0). The presence of PABA inhibited the degradation of TCS-PABA, and the weakest inhibitory effect was observed while the concentration of PABA was 5 mg L(-1). The addition of DOM (Suwannee River fulvic acid standard I [SRFA], Suwannee River HA standard II [SRHA], and Suwannee River natural organic matter [SRNOM]) showed different inhibition effects on TCS-PABA degradation. However, higher Fe(III) concentration at the DOM concentration of 5 mg L(-1) could favor the formation of DOM-hydrolytic Fe(III) species complexes, further accelerating the degradation of TCS-PABA. In comparison with deionized water (DI water), TCS-PABA could be better photodegraded in river water nearby the effluent of a wastewater treatment plant. This study provides useful information for understanding the natural behavior of TCS in the presence of other organic contaminants.

  15. Sequence dependent N-terminal rearrangement and degradation of peptide nucleic acid (PNA) in aqueous solution

    NASA Technical Reports Server (NTRS)

    Eriksson, M.; Christensen, L.; Schmidt, J.; Haaima, G.; Orgel, L.; Nielsen, P. E.

    1998-01-01

    The stability of the PNA (peptide nucleic acid) thymine monomer inverted question markN-[2-(thymin-1-ylacetyl)]-N-(2-aminoaminoethyl)glycine inverted question mark and those of various PNA oligomers (5-8-mers) have been measured at room temperature (20 degrees C) as a function of pH. The thymine monomer undergoes N-acyl transfer rearrangement with a half-life of 34 days at pH 11 as analyzed by 1H NMR; and two reactions, the N-acyl transfer and a sequential degradation, are found by HPLC analysis to occur at measurable rates for the oligomers at pH 9 or above. Dependent on the amino-terminal sequence, half-lives of 350 h to 163 days were found at pH 9. At pH 12 the half-lives ranged from 1.5 h to 21 days. The results are discussed in terms of PNA as a gene therapeutic drug as well as a possible prebiotic genetic material.

  16. Phytosphingosine degradation pathway includes fatty acid α-oxidation reactions in the endoplasmic reticulum.

    PubMed

    Kitamura, Takuya; Seki, Naoya; Kihara, Akio

    2017-03-28

    Although normal fatty acids (FAs) are degraded via β-oxidation, unusual FAs such as 2-hydroxy (2-OH) FAs and 3-methyl-branched FAs are degraded via α-oxidation. Phytosphingosine (PHS) is one of the long-chain bases (the sphingolipid components) and exists in specific tissues, including the epidermis and small intestine in mammals. In the degradation pathway, PHS is converted to 2-OH palmitic acid and then to pentadecanoic acid (C15:0-COOH) via FA α-oxidation. However, the detailed reactions and genes involved in the α-oxidation reactions of the PHS degradation pathway have yet to be determined. In the present study, we reveal the entire PHS degradation pathway: PHS is converted to C15:0-COOH via six reactions [phosphorylation, cleavage, oxidation, CoA addition, cleavage (C1 removal), and oxidation], in which the last three reactions correspond to the α-oxidation. The aldehyde dehydrogenase ALDH3A2 catalyzes both the first and second oxidation reactions (fatty aldehydes to FAs). In Aldh3a2-deficient cells, the unmetabolized fatty aldehydes are reduced to fatty alcohols and are incorporated into ether-linked glycerolipids. We also identify HACL2 (2-hydroxyacyl-CoA lyase 2) [previous name, ILVBL; ilvB (bacterial acetolactate synthase)-like] as the major 2-OH acyl-CoA lyase involved in the cleavage (C1 removal) reaction in the FA α-oxidation of the PHS degradation pathway. HACL2 is localized in the endoplasmic reticulum. Thus, in addition to the already-known FA α-oxidation in the peroxisomes, we have revealed the existence of FA α-oxidation in the endoplasmic reticulum in mammals.

  17. Mild MPP(+) exposure impairs autophagic degradation through a novel lysosomal acidity-independent mechanism.

    PubMed

    Miyara, Masatsugu; Kotake, Yaichiro; Tokunaga, Wataru; Sanoh, Seigo; Ohta, Shigeru

    2016-10-01

    Parkinson's disease (PD) is the second most common neurodegenerative disorder, but its underlying cause remains unknown. Although recent studies using PD-related neurotoxin MPP(+) suggest autophagy involvement in the pathogenesis of PD, the effect of MPP(+) on autophagic processes under mild exposure, which mimics the slow progressive nature of PD, remains largely unclear. We examined the effect of mild MPP(+) exposure (10 and 200 μM for 48 h), which induces a more slowly developing cell death, on autophagic processes and the mechanistic differences with acute MPP(+) toxicity (2.5 and 5 mM for 24 h). In SH-SY5Y cells, mild MPP(+) exposure predominantly inhibited autophagosome degradation, whereas acute MPP(+) exposure inhibited both autophagosome degradation and basal autophagy. Mild MPP(+) exposure reduced lysosomal hydrolase cathepsin D activity without changing lysosomal acidity, whereas acute exposure decreased lysosomal density. Lysosome biogenesis enhancers trehalose and rapamycin partially alleviated mild MPP(+) exposure induced impaired autophagosome degradation and cell death, but did not prevent the pathogenic response to acute MPP(+) exposure, suggesting irreversible lysosomal damage. We demonstrated impaired autophagic degradation by MPP(+) exposure and mechanistic differences between mild and acute MPP(+) toxicities. Mild MPP(+) toxicity impaired autophagosome degradation through novel lysosomal acidity-independent mechanisms. Sustained mild lysosomal damage may contribute to PD. We examined the effects of MPP(+) on autophagic processes under mild exposure, which mimics the slow progressive nature of Parkinson's disease, in SH-SY5Y cells. This study demonstrated impaired autophagic degradation through a reduction in lysosomal cathepsin D activity without altering lysosomal acidity by mild MPP(+) exposure. Mechanistic differences between acute and mild MPP(+) toxicity were also observed. Sustained mild damage of lysosome may be an underlying cause

  18. Nanomechanical properties of poly(lactic-co-glycolic) acid film during degradation.

    PubMed

    Shirazi, Reyhaneh Neghabat; Aldabbagh, Fawaz; Erxleben, Andrea; Rochev, Yury; McHugh, Peter

    2014-11-01

    Despite the potential applications of poly(lactic-co-glycolic) acid (PLGA) coatings in medical devices, the mechanical properties of this material during degradation are poorly understood. In the present work, the nanomechanical properties and degradation of PLGA film were investigated. Hydrolysis of solvent-cast PLGA film was studied in buffer solution at 37 °C. The mass loss, water uptake, molecular weight, crystallinity and surface morphology of the film were tracked during degradation over 20 days. Characterization of the surface hardness and Young's modulus was performed using the nanoindentation technique for different indentation loads. The initially amorphous films were found to remain amorphous during degradation. The molecular weight of the film decreased quickly during the initial days of degradation. Diffusion of water into the film resulted in a reduction in surface hardness during the first few days, followed by an increase that was due to the surface roughness. There was a significant delay between the decrease in the mechanical properties of the film and the decrease in the molecular weight. A sudden decline in mechanical properties indicated that significant bulk degradation had occurred.

  19. Degradation behavior of hydroxyapatite/poly(lactic-co-glycolic) acid nanocomposite in simulated body fluid

    SciTech Connect

    Liuyun, Jiang; Chengdong, Xiong; Lixin, Jiang; Lijuan, Xu

    2013-10-15

    Graphical abstract: In this manuscript, we initiated a systematic study to investigate the effect of HA on thermal properties, inner structure, reduction of mechanical strength, surface morphology and the surface deposit of n-HA/PLGA composite with respect to the soaking time. The results showed that n-HA played an important role in improving the degradation behavior of n-HA/PLGA composite, which can accelerate the degradation of n-HA/PLGA composite and endow it with bioactivity, after n-HA was detached from PLGA during the degradation, so that n-HA/PLGA composite may have a more promising prospect of the clinical application than pure PLGA as bone fracture internal fixation materials, and the results would be of reference significance to predict the in vivo degradation and biological properties. - Highlights: • Effect of n-HA on degradation behavior of n-HA/PLGA composite was investigated. • Degradation behaviors of n-HA/PLGA and PLGA were carried out in SBF for 6 months. • Viscosity, thermal properties, inner structure and bending strength were tested. • n-HA can accelerate the degradation and endows it with bioactivity. - Abstract: To investigate the effect of hydroxyapatite(HA) on the degradation behavior of hydroxyapatite/poly(lactic-co-glycolic) acid (HA/PLGA) nanocomposite, the degradation experiment of n-HA/PLGA composite and pure PLGA were carried out by soaking in simulated body fluid(SBF) at 37 °C for 1, 2, 4 and 6 months. The change of intrinsic viscosity, thermal properties, inner structure, bending strength reduction, surface morphology and the surface deposit of n-HA/PLGA composite and pure PLGA with respect to the soaking time were investigated by means of UbbeloHde Viscometer, differential scanning calorimeter (DSC), scanning electron microscope(SEM), electromechanical universal tester, a conventional camera and X-ray diffraction (XRD). The results showed that n-HA played an important role in improving the degradation behavior of n

  20. Phytate degrading activities of lactic acid bacteria isolated from traditional fermented food

    NASA Astrophysics Data System (ADS)

    Damayanti, Ema; Ratisiwi, Febiyani Ndaru; Istiqomah, Lusty; Sembiring, Langkah; Febrisiantosa, Andi

    2017-03-01

    The objective of this study was to determine the potential of LAB with phytate degrading activity from fermented traditional food grain-based and legume-based. Lactic acid bacteria were isolated from different sources of traditional fermented food from Gunungkidul Yogyakarta Indonesia such as gembus tempeh (tofu waste), soybean tempeh, lamtoro tempeh (Leucaena bean) and kara tempeh. Isolation of LAB was performed using Total Plate Count (TPC) on de Man Rogosa Sharpe Agar (MRSA) medium supplemented with CaCO3. They were screened for their ability to degrade myo-inositol hexaphosphate or IP6 by using qualitative streak platemethod with modified de Man Rogosa-MorpholinoPropanesulfonic Acid Sharpe (MRS-MOPS) medium contained sodium salt of phytic acid as substrate and cobalt chloride staining (plate assay) method. The selected isolates were further assayed for phytase activities using quantitative method with spectrophotometer and the two selected isolates growth were optimized. Furthermore, thhe isolates that shown the highest phytase activity was characterized and identified using API 50 CH kitand 16S rRNA gene sequencing. The results showed that there were 18 LAB isolates obtained from samplesand 13 isolates were able to degrade sodium phytate based on qualitative screening. According to quantitative assay, the highest phytate degrading activities were found in TG-2(23.562 U/mL) and TG-1 (19.641 U/mL) isolated from gembus tempeh. The phytate activity of TG-2 was optimum at 37 °C with agitation, while the phytate activity of TG-1 was optimum at 45 °C without agitation. Characterization and identification of TG-2 isolate with the highest phytate degrading activity using API 50 CH and 16S rRNA showed that TG-2had homology with Lactobacillus fermentum. It could be concluded that LAB from from fermented traditional food grain-based and legume-based produced the extracellular phytase. Keywords: lactic acid bacteria, tempeh, phytatedegrading activity

  1. Environmental photochemistry on semiconductor surfaces: Photosensitized degradation of a textile azo dye, Acid Orange 7, on TiO{sub 2} particles using visible light

    SciTech Connect

    Vinodgopal, K.; Wynkoop, D.E.; Kamat, P.V.

    1996-05-01

    Photosensitized degradation of a textile azo dye, Acid Orange 7, has been carried out on TiO{sub 2} particles using visible light. Mechanistic details of the dye degradation have been elucidated using diffuse reflectance absorption and FTIR techniques. Degradation does not occur on Al{sub 2}O{sub 3} surface or in the absence of oxygen. The dependence of the dye degradation rate on the surface coverage shows the participation of excited dye and TiO{sub 2} semiconductor in the surface photochemical process. Diffuse reflectance laser flash photolysis confirms the charge injection from the excited dye molecule into the conduction band of the semiconductor as the primary mechanism for producing oxidized dye radical. The surface-adsorbed oxygen plays an important role in scavenging photogenerated electrons, thus preventing the recombination between the oxidized dye radical and the photoinjected electrons. Diffuse reflectance FTIR was used to make a tentative identification of reaction intermediates and end products of dye degradation. The intermediates, 1,2-naphthoquinone and phthalic acid, have been identified during the course of degradation. Though less explored in photocatalysis, the photosensitization approach could be an excellent choice for the degradation of colored pollutants using visible light. 51 refs., 10 figs.

  2. Screening and Characterization of Purine Nucleoside Degrading Lactic Acid Bacteria Isolated from Chinese Sauerkraut and Evaluation of the Serum Uric Acid Lowering Effect in Hyperuricemic Rats

    PubMed Central

    Mei, Lu; Yuan, Lin; Xie, Ao; Yuan, Jieli

    2014-01-01

    Hyperuricemia is well known as the cause of gout. In recent years, it has also been recognized as a risk factor for arteriosclerosis, cerebrovascular and cardiovascular diseases, and nephropathy in diabetic patients. Foods high in purine compounds are more potent in exacerbating hyperuricemia. Therefore, the development of probiotics that efficiently degrade purine compounds is a promising potential therapy for the prevention of hyperuricemia. In this study, fifty-five lactic acid bacteria isolated from Chinese sauerkraut were evaluated for the ability to degrade inosine and guanosine, the two key intermediates in purine metabolism. After a preliminary screening based on HPLC, three candidate strains with the highest nucleoside degrading rates were selected for further characterization. The tested biological characteristics of candidate strains included acid tolerance, bile tolerance, anti-pathogenic bacteria activity, cell adhesion ability, resistance to antibiotics and the ability to produce hydrogen peroxide. Among the selected strains, DM9218 showed the best probiotic potential compared with other strains despite its poor bile resistance. Analysis of 16S rRNA sequences showed that DM9218 has the highest similarity (99%) to Lactobacillus plantarum WCFS1. The acclimated strain DM9218-A showed better resistance to 0.3% bile salt, and its survival in gastrointestinal tract of rats was proven by PCR-DGGE. Furthermore, the effects of DM9218-A in a hyperuricemia rat model were evaluated. The level of serum uric acid in hyperuricemic rat can be efficiently reduced by the intragastric administration of DM9218-A (P<0.05). The preventive treatment of DM9218-A caused a greater reduction in serum uric acid concentration in hyperuricemic rats than the later treatment (P<0.05). Our results suggest that DM9218-A may be a promising candidate as an adjunctive treatment in patients with hyperuricemia during the onset period of disease. DM9218-A also has potential as a probiotic

  3. Screening and characterization of purine nucleoside degrading lactic acid bacteria isolated from Chinese sauerkraut and evaluation of the serum uric acid lowering effect in hyperuricemic rats.

    PubMed

    Li, Ming; Yang, Dianbin; Mei, Lu; Yuan, Lin; Xie, Ao; Yuan, Jieli

    2014-01-01

    Hyperuricemia is well known as the cause of gout. In recent years, it has also been recognized as a risk factor for arteriosclerosis, cerebrovascular and cardiovascular diseases, and nephropathy in diabetic patients. Foods high in purine compounds are more potent in exacerbating hyperuricemia. Therefore, the development of probiotics that efficiently degrade purine compounds is a promising potential therapy for the prevention of hyperuricemia. In this study, fifty-five lactic acid bacteria isolated from Chinese sauerkraut were evaluated for the ability to degrade inosine and guanosine, the two key intermediates in purine metabolism. After a preliminary screening based on HPLC, three candidate strains with the highest nucleoside degrading rates were selected for further characterization. The tested biological characteristics of candidate strains included acid tolerance, bile tolerance, anti-pathogenic bacteria activity, cell adhesion ability, resistance to antibiotics and the ability to produce hydrogen peroxide. Among the selected strains, DM9218 showed the best probiotic potential compared with other strains despite its poor bile resistance. Analysis of 16S rRNA sequences showed that DM9218 has the highest similarity (99%) to Lactobacillus plantarum WCFS1. The acclimated strain DM9218-A showed better resistance to 0.3% bile salt, and its survival in gastrointestinal tract of rats was proven by PCR-DGGE. Furthermore, the effects of DM9218-A in a hyperuricemia rat model were evaluated. The level of serum uric acid in hyperuricemic rat can be efficiently reduced by the intragastric administration of DM9218-A (P<0.05). The preventive treatment of DM9218-A caused a greater reduction in serum uric acid concentration in hyperuricemic rats than the later treatment (P<0.05). Our results suggest that DM9218-A may be a promising candidate as an adjunctive treatment in patients with hyperuricemia during the onset period of disease. DM9218-A also has potential as a probiotic

  4. Degradation of Fructans and Production of Propionic Acid by Bacteroides thetaiotaomicron are Enhanced by the Shortage of Amino Acids

    PubMed Central

    Adamberg, Signe; Tomson, Katrin; Vija, Heiki; Puurand, Marju; Kabanova, Natalja; Visnapuu, Triinu; Jõgi, Eerik; Alamäe, Tiina; Adamberg, Kaarel

    2014-01-01

    Bacteroides thetaiotaomicron is commonly found in the human colon and stabilizes its ecosystem by catabolism of various polysaccharides. A model of cross-talk between the metabolism of amino acids and fructans in B. thetaiotaomicron was proposed. The growth of B. thetaiotaomicron DSM 2079 in two defined media containing mineral salts and vitamins, and supplemented with either 20 or 2 amino acids, was studied in an isothermal microcalorimeter. The polyfructans inulin (from chicory) and levan (synthesized using levansucrase from Pseudomonas syringae), two fructooligosaccharide preparations with different composition, sucrose and fructose were tested as substrates. The calorimetric power-time curves were substrate specific and typically multiauxic. A surplus of amino acids reduced the consumption of longer oligosaccharides (degree of polymerization > 3). Bacterial growth was not detected either in the carbohydrate free medium containing amino acids or in the medium with inulin as a sole carbohydrate. In amino acid-restricted medium, fermentation leading to acetic acid formation was dominant at the beginning of growth (up to 24 h), followed by increased lactic acid production, and mainly propionic and succinic acids were produced at the end of fermentation. In the medium supplemented with 20 amino acids, the highest production of d-lactate (82 ± 33 mmol/gDW) occurred in parallel with extensive consumption (up to 17 mmol/gDW) of amino acids, especially Ser, Thr, and Asp. The production of Ala and Glu was observed at growth on all substrates, and the production was enhanced under amino acid deficiency. The study revealed the influence of amino acids on fructan metabolism in B. thetaiotaomicron and showed that defined growth media are invaluable in elucidating quantitative metabolic profiles of the bacteria. Levan was shown to act as an easily degradable substrate for B. thetaiotaomicron. The effect of levan on balancing or modifying colon microbiota will

  5. The role of nanoparticulate agglomerates in TiO2 photocatalysis: degradation of oxalic acid

    NASA Astrophysics Data System (ADS)

    Ivanova, Irina; Mendive, Cecilia B.; Bahnemann, Detlef

    2016-07-01

    The simultaneous bimodal study of the photocatalytic oxalic acid degradation by aqueous TiO2 suspensions revealed that particular systems possess the capacity to protect a certain amount of oxalic acid from oxidation, thus hindering, to some extent, the photocatalytic reaction. While measurements of the oxalic acid concentration in the bulk liquid phase indicated full photocatalytic degradation; in situ pH-stat measurements allowed the quantification of the amount of oxalic acid remaining in the part of the nanoparticulate agglomerates where light could apparently not access. An explanation for this phenomenon takes into account the possibility of the formation of TiO2 agglomerates in which these molecules are hidden from the effect of the light, thus being protected from photocatalytic degradation. Studies of different TiO2 materials with different particle sizes allowed a deeper exploration of this phenomenon. In addition, because this property of encapsulating pollutant molecules by photocatalytic systems is found to be a reversible phenomenon, P25 appears to be more convenient and advantageous as compared to the use of large surface area photocatalysts.

  6. Effects of zinc and sodium monensin on ruminal degradation of lysine-HCl and liquid 2-hydroxy-4-methylthiobutanoic acid.

    PubMed

    Bateman, H G; Williams, C C; Gantt, D T; Chung, Y H; Beem, A E; Stanley, C C; Goodier, G E; Hoyt, P G; Ward, J D; Bunting, L D

    2004-08-01

    Four nonlactating, mature, Holstein cows were fitted with ruminal cannula and used in a 4 x 4 Latin square-designed experiment to evaluate the impact of supplemental Zn and monensin on ruminal degradation of Lys and liquid 2-hydroxy-4-methylthiobutanoic acid (HMB). Cows were fed 4.54 kg (as fed) of alfalfa hay top-dressed with 4.54 kg (as fed) concentrate once daily. Concentrates were formulated to provide 0 or 500 mg/kg of Zn as ZnSO4 and 0 or 40 mg/kg of monensin in the total diet. Zinc supplementation provided approximately 22-fold greater dietary Zn than estimated by NRC requirements. On d 14 of each period, cows were dosed via the rumen cannula with 50 g of HMB and 100 g of Lys-HCl, and the concentrations of Lys and HMB were monitored every 0.5 h for 8 h. Supplemental Zn tended to decrease the proportion of acetate in ruminal fluid postfeeding and increased the proportion of propionate in ruminal fluid postfeeding. Supplemental Zn increased mean fluid passage rate from the rumen. Monensin decreased the proportion of acetate and increased the mean proportion of propionate in ruminal fluid, resulting in a decrease in the ratio of acetate to propionate. Monensin also increased the mean fluid passage rate from the rumen. Neither Zn nor monensin affected the apparent rate of ruminal disappearance of HMB or Lys. However, Zn and monensin interacted to alter the ruminal degradability of free Lys but not HMB. These data indicate that Zn and monensin may interact to alter ruminal degradability of free amino acids.

  7. Enhanced rates of photocatalytic degradation of an azo dye using SnO{sub 2}/TiO{sub 2} coupled semiconductor thin films

    SciTech Connect

    Vinodgopal, K.; Kamat, P.V.

    1995-03-01

    We present here for the first time the results from electrochemically assisted photocatalytic experiments using coupled TiO{sub 2}/SnO{sub 2} semiconductor thin films in the degradation of textile dye effluent. We show that by using such a system the oxidative efficiency of photocatalytic semiconductor systems in degrading a commercial azo dye such as Acid Orange 7 (AO7) can be improved. The results presented here on the decolorization of the azo dye AO7 represents a major step forward in the development of new advanced oxidation processes for the treatment of such industrial waste. The improved charge separation as a result of coupling two semiconductor systems with different energy levels and the applied anodic bias is responsible for the enhancement in the rate of photocatalytic degradation. 20 refs., 6 figs.

  8. Potential of wine-associated lactic acid bacteria to degrade biogenic amines.

    PubMed

    García-Ruiz, Almudena; González-Rompinelli, Eva M; Bartolomé, Begoña; Moreno-Arribas, M Victoria

    2011-08-02

    Some lactic acid bacteria (LAB) isolated from fermented foods have been proven to degrade biogenic amines through the production of amine oxidase enzymes. Since little is known about this in relation to wine micro-organisms, this work examined the ability of LAB strains (n=85) isolated from wines and other related enological sources, as well as commercial malolactic starter cultures (n=3) and type strains (n=2), to degrade histamine, tyramine and putrescine. The biogenic amine-degrading ability of the strains was evaluated by RP-HPLC in culture media and wine malolactic fermentation laboratory experiments. Although at different extent, 25% of the LAB isolates were able to degrade histamine, 18% tyramine and 18% putrescine, whereas none of the commercial malolactic starter cultures or type strains were able to degrade any of the tested amines. The greatest biogenic amine-degrading ability was exhibited by 9 strains belonging to the Lactobacillus and Pediococcus groups, and most of them were able to simultaneously degrade at least two of the three studied biogenic amines. Further experiments with one of the strains that showed high biogenic amine-degrading ability (L. casei IFI-CA 52) revealed that cell-free extracts maintained this ability in comparison to the cell suspensions at pH 4.6, indicating that amine-degrading enzymes were effectively extracted from the cells and their action was optimal in the degradation of biogenic amines. In addition, it was confirmed that wine components such as ethanol (12%) and polyphenols (75 mg/L), and wine additives such as SO(2) (30 mg/L), reduced the histamine-degrading ability of L. casei IFI-CA 52 at pH 4.6 by 80%, 85% and 11%, respectively, in cell suspensions, whereas the reduction was 91%, 67% and 50%, respectively, in cell-free extracts. In spite of this adverse influence of the wine matrix, our results proved the potential of wine-associated LAB as a promising strategy to reduce biogenic amines in wine.

  9. Photocatalytic degradation kinetics of naphthenic acids in oil sands process-affected water: Multifactorial determination of significant factors.

    PubMed

    Leshuk, Tim; de Oliveira Livera, Diogo; Peru, Kerry M; Headley, John V; Vijayaraghavan, Sucharita; Wong, Timothy; Gu, Frank

    2016-12-01

    Oil sands process-affected water (OSPW) is generated as a byproduct of bitumen extraction in Canada's oil sands. Due to the water's toxicity, associated with dissolved acid extractable organics (AEO), especially naphthenic acids (NAs), along with base-neutral organics, OSPW may require treatment to enable safe discharge to the environment. Heterogeneous photocatalysis is a promising advanced oxidation process (AOP) for OSPW remediation, however, predicting treatment efficacy can be challenging due to the unique water chemistry of OSPW from different tailings ponds. The objective of this work was to study various factors affecting the kinetics of photocatalytic AEO degradation in OSPW. The rate of photocatalytic treatment varied significantly in two different OSPW sources, which could not be accounted for by differences in AEO composition, as studied by high resolution mass spectrometry (HRMS). The effects of inorganic water constituents were investigated using factorial and response surface experiments, which revealed that hydroxyl (HO) radical scavenging by iron (Fe(3+)) and bicarbonate (HCO3(-)) inhibited the NA degradation rate. The effects of NA concentration and temperature on the treatment kinetics were also evaluated in terms of Langmuir-Hinshelwood and Arrhenius models; pH and temperature were identified as weak factors, while dissolved oxygen (DO) was critical to the photo-oxidation reaction. Accounting for all of these variables, a general empirical kinetic expression is proposed, enabling prediction of photocatalytic treatment performance in diverse sources of OSPW.

  10. Enhanced Photocatalytic Degradation of Salicylic Acid in Water-ethanol Mixtures from Titanium Dioxide Grafted with Hexadecyltrichlorosilane

    NASA Astrophysics Data System (ADS)

    Kassir, Mounir; Roques-Carmes, Thibault; Assaker, Karine; Hamieh, Tayssir; Razafitianamaharavo, Angelina; Toufaily, Joumana; Villiéras, Frédéric

    The aim of this paper is to study the effect of the chemical modification on the photocatalytic properties of TiO2. The TiO2 Degussa-P25 nanoparticles are chemically modified using the hydrophobic organosilane hexadecyltrichlorosilane (HTS). The samples are employed as catalysts for salicylic acid photocatalytic oxidation in water-ethanol mixtures. The kinetics of salicylic acid photodegradation is investigated as a function of ethanol content in water-ethanol mixtures and initial HTS concentrations. The results indicate that the HTS groups are not degraded during the photocatalytic process. The TiO2 grafted by HTS is more efficient than bare TiO2 for the photodegradation process in presence of ethanol. The photodegradation process follows first order kinetics and the apparent rate constant increases linearly with the initial HTS concentration (amount of HTS grafted).

  11. Culturing oil sands microbes as mixed species communities enhances ex situ model naphthenic acid degradation

    PubMed Central

    Demeter, Marc A.; Lemire, Joseph A.; Yue, Gordon; Ceri, Howard; Turner, Raymond J.

    2015-01-01

    Oil sands surface mining for bitumen results in the formation of oil sands process water (OSPW), containing acutely toxic naphthenic acids (NAs). Potential exists for OSPW toxicity to be mitigated by aerobic degradation of the NAs by microorganisms indigenous to the oil sands tailings ponds, the success of which is dependent on the methods used to exploit the metabolisms of the environmental microbial community. Having hypothesized that the xenobiotic tolerant biofilm mode-of-life may represent a feasible way to harness environmental microbes for ex situ treatment of OSPW NAs, we aerobically grew OSPW microbes as single and mixed species biofilm and planktonic cultures under various conditions for the purpose of assaying their ability to tolerate and degrade NAs. The NAs evaluated were a diverse mixture of eight commercially available model compounds. Confocal microscopy confirmed the ability of mixed and single species OSPW cultures to grow as biofilms in the presence of the NAs evaluated. qPCR enumeration demonstrated that the addition of supplemental nutrients at concentrations of 1 g L-1 resulted in a more numerous population than 0.001 g L-1 supplementation by approximately 1 order of magnitude. GC-FID analysis revealed that mixed species cultures (regardless of the mode of growth) are the most effective at degrading the NAs tested. All constituent NAs evaluated were degraded below detectable limits with the exception of 1-adamantane carboxylic acid (ACA); subsequent experimentation with ACA as the sole NA also failed to exhibit degradation of this compound. Single species cultures degraded select few NA compounds. The degradation trends highlighted many structure-persistence relationships among the eight NAs tested, demonstrating the effect of side chain configuration and alkyl branching on compound recalcitrance. Of all the isolates, the Rhodococcus spp. degraded the greatest number of NA compounds, although still less than the mixed species cultures

  12. Rumen Degradability and Post-ruminal Digestion of Dry Matter, Nitrogen and Amino Acids of Three Protein Supplements.

    PubMed

    Gao, Wei; Chen, Aodong; Zhang, Bowen; Kong, Ping; Liu, Chenli; Zhao, Jie

    2015-04-01

    This study evaluated the in situ ruminal degradability, and subsequent small intestinal digestibility (SID) of dry matter, crude protein (CP), and amino acids (AA) of cottonseed meal (CSM), sunflower seed meal (SFSM) and distillers dried grains with solubles (DDGS) by using the modified three-step in vitro procedure. The ruminal degradability and subsequent SID of AA in rumen-undegradable protein (RUP-AA) varied among three protein supplements. The result show that the effective degradability of DM for SFSM, CSM, and DDGS was 60.8%, 56.4%, and 41.0% and their ruminal fermentable organic matter was 60.0%, 55.9%, and 39.9%, respectively. The ruminal degradable protein (RDP) content in CP for SFSM, CSM, and DDGS was 68.3%, 39.0%, and 32.9%, respectively, at the ruminal solid passage rate of 1.84%/h. The SFSM is a good source of RDP for rumen micro-organisms; however, the SID of RUP of SFSM was lower. The DDGS and CSM are good sources of RUP for lambs to digest in the small intestine to complement ruminal microbial AA of growing lambs. Individual RUP-AA from each protein source was selectively removed by the rumen micro-organisms, especially for Trp, Arg, His, and Lys (p<0.01). The SID of individual RUP-AA was different within specific RUP origin (p<0.01). Limiting amino acid was Leu for RUP of CSM and Lys for both RUP of SFSM and DDGS, respectively. Therefore, different protein supplements with specific limitations should be selected and combined carefully in growing lambs ration to optimize AA balance.

  13. Mechanistic studies on the degradation and protein release characteristics of poly(lactic-co-glycolic-co-hydroxymethylglycolic acid) nanospheres.

    PubMed

    Samadi, N; van Nostrum, C F; Vermonden, T; Amidi, M; Hennink, W E

    2013-04-08

    The purpose of this study was to gain mechanistic insights into the effect of different formulation parameters on the degradation and release behavior of protein-loaded nanoparticulate carrier systems based on an aliphatic polyester with pendant hydroxyl groups, poly(lactic-co-glycolic-hydroxymethyl glycolic acid) (pLGHMGA). Bovine serum albumin (BSA) was used as a model protein. BSA-loaded pLGHMGA nanospheres of 400-700 nm were prepared using a solvent evaporation method using pLGHMGA of different molecular weights and different compositions. Also, the concentration of pLGHMGA in the organic phase was varied. The nanospheres showed a continuous mass loss accompanied by continuous decrease in number average molecular weight, which indicates that the degradation of the nanospheres is by bulk degradation with a rapid release of water-soluble low molecular weight fragments. On the basis of NMR analysis, it is concluded that intramolecular transesterification precedes extensive hydrolysis of the polymer and degradation of the nanospheres. BSA-loaded freeze-dried nanospheres showed a significant burst release of 40-50% of the BSA loading. In contrast, nonfreeze-dried samples showed a small burst of around 10-20%, indicating that freeze-drying induced pore formation. Nonlyophilized nanospheres prepared from pLGHMGA with 64/18/18 lactic/glycolic/hydroxymethylglycolic acid (L/G/HMG) ratio showed a relatively fast release of BSA for the next 30 days. Nanospheres prepared from a more hydrophobic pLGHMGA (74/13/13, L/G/HMG) showed a two-phase release. Circular dichroism analysis showed that the secondary structure of the released protein was preserved. This study shows a correlation between release behavior and particle erosion rate, which can be modulated by the copolymer composition.

  14. Innovative use of a bacterial enzyme involved in sialic acid degradation to initiate sialic acid biosynthesis in glycoengineered insect cells

    PubMed Central

    Geisler, Christoph; Jarvis, Donald L.

    2012-01-01

    The baculovirus/insect cell system is widely used for recombinant protein production, but it is suboptimal for recombinant glycoprotein production because it does not provide sialylation, which is an essential feature of many glycoprotein biologics. This problem has been addressed by metabolic engineering, which has extended endogenous insect cell N-glycosylation pathways and enabled glycoprotein sialylation by baculovirus/insect cell systems. However, further improvement is needed because even the most extensively engineered baculovirus/insect cell systems require media supplementation with N-acetylmannosamine, an expensive sialic acid precursor, for efficient recombinant glycoprotein sialylation. Our solution to this problem focused on E. coli N-acetylglucosamine-6-phosphate 2′-epimerase (GNPE), which normally functions in bacterial sialic acid degradation. Considering that insect cells have the product, but not the substrate for this enzyme, we hypothesized that GNPE might drive the reverse reaction in these cells, thereby initiating sialic acid biosynthesis in the absence of media supplementation. We tested this hypothesis by isolating transgenic insect cells expressing E. coli GNPE together with a suite of mammalian genes needed for N-glycoprotein sialylation. Various assays showed that these cells efficiently produced sialic acid, CMP-sialic acid, and sialylated recombinant N-glycoproteins even in growth media without N-acetylmannosamine. Thus, this study demonstrated that a eukaryotic recombinant protein production platform can be glycoengineered with a bacterial gene, that a bacterial enzyme which normally functions in sialic acid degradation can be used to initiate sialic acid biosynthesis, and that insect cells expressing this enzyme can produce sialylated N-glycoproteins without N-acetylmannosamine supplementation, which will reduce production costs in glycoengineered baculovirus/insect cell systems. PMID:23022569

  15. Varying relative degradation rates of oil in different forms and environments revealed by ramped pyrolysis.

    PubMed

    Pendergraft, Matthew A; Rosenheim, Brad E

    2014-09-16

    Degradation of oil contamination yields stabilized products by removing and transforming reactive and volatile compounds. In contaminated coastal environments, the processes of degradation are influenced by shoreline energy, which increases the surface area of the oil as well as exchange between oil, water, sediments, microbes, oxygen, and nutrients. Here, a ramped pyrolysis carbon isotope technique is employed to investigate thermochemical and isotopic changes in organic material from coastal environments contaminated with oil from the 2010 BP Deepwater Horizon oil spill. Oiled beach sediment, tar ball, and marsh samples were collected from a barrier island and a brackish marsh in southeast Louisiana over a period of 881 days. Stable carbon ((13)C) and radiocarbon ((14)C) isotopic data demonstrate a predominance of oil-derived carbon in the organic material. Ramped pyrolysis profiles indicate that the organic material was transformed into more stable forms. Our data indicate relative rates of stabilization in the following order, from fastest to slowest: high energy beach sediments > low energy beach sediments > marsh > tar balls. Oil was transformed most rapidly where shoreline energy and the rates of oil dispersion and exchange with water, sediments, microbes, oxygen, and nutrients were greatest. Still, isotope data reveal persistence of oil.

  16. Rate of degradation of lambda-cyhalothrin and methomyl in grapes (Vitis vinifera L.).

    PubMed

    Banerjee, Kaushik; Upadhyay, Ajay Kumar; Adsule, Pandurang G; Patil, Sangram H; Oulkar, Dasharath P; Jadhav, Deepak R

    2006-10-01

    Rates of degradation of lambda-cyhalothrin and methomyl residues in grape are reported. The dissipation behavior of both insecticides followed first-order rate kinetics with similar patterns at standard and double-dose applications. Residues of lambda-cyhalothrin were lost with pre-harvest intervals (PHI) of 12.0-12.5 and 15.0-15.5 days, corresponding to the applications at 25 and 50 g a.i. ha-1, respectively. In the case of methomyl, residues were lost with PHI of 55.0 and 61.0 days, following applications at 1 and 2 kg a.i. ha-1, respectively. The PHI, recommended on the basis of the experimental results, was shown to be effective in minimizing residue load of these insecticides below their maximum residue limits (MRLs) in vineyard samples.

  17. Competition for transport of amino acids into rat heart: effect of competitors on protein synthesis and degradation.

    PubMed

    Tovar, A R; Tews, J K; Torres, N; Madsen, D C; Harper, A E

    1992-09-01

    Transport of the neutral amino acids, 2-(methylamino)isobutyrate (MeAIB) and Phe, was examined in isolated rat hearts perfused by the Langendorff method. Hearts were perfused by recirculating for various time periods buffer containing [14C]-MeAIB or [14C]-Phe plus desired additions. Uptake of MeAIB was linear for approximately 30 minutes; Phe uptake was linear for a maximum of 5 minutes, and reached a steady state after 15 minutes. Km and Vmax for MeAIB were 1.1 +/- 0.03 mmol/L and 37.7 +/- 0.4 pmol/microL intracellular fluid (ICF)/min; values for Phe were 1.8 +/- 0.02 mmol/L and 364 +/- 5 pmol/microL ICF/minute. Uptake of MeAIB (0.2 mmol/L) was reduced 95% in the presence of Ser (10 mmol/L), and less severely by large neutral amino acids ([LNAA], 10 mmol/L) such as Phe and Leu (by 46% and 54%, respectively). Uptake of Phe (0.2 mmol/L) was reduced by LNAA such as Val, Leu, and Ile (by 51%, 78%, and 81%, respectively), or by commercial preparations used in parenteral nutrition, eg, Travasol or Travasol plus extra branched-chain amino acids (BCAA) (Branchamin); Ser had little effect (8% reduction). Insulin in the perfusion medium increased the fractional rate of protein synthesis. Individual BCAA at physiological concentrations (0.2 mmol/L) did not alter the rate of protein synthesis. Branchamin or Travasol plus Branchamin also had no effect on the rate of protein synthesis in heart, but did depress the rate of degradation. These studies suggest that amino acid transport into heart may be affected by normal levels of plasma amino acids, whereas protein synthesis is not.

  18. From ether to acid: A plausible degradation pathway of glycerol dialkyl glycerol tetraethers

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-Lei; Birgel, Daniel; Elling, Felix J.; Sutton, Paul A.; Lipp, Julius S.; Zhu, Rong; Zhang, Chuanlun; Könneke, Martin; Peckmann, Jörn; Rowland, Steven J.; Summons, Roger E.; Hinrichs, Kai-Uwe

    2016-06-01

    Glycerol dialkyl glycerol tetraethers (GDGTs) are ubiquitous microbial lipids with extensive demonstrated and potential roles as paleoenvironmental proxies. Despite the great attention they receive, comparatively little is known regarding their diagenetic fate. Putative degradation products of GDGTs, identified as hydroxyl and carboxyl derivatives, were detected in lipid extracts of marine sediment, seep carbonate, hot spring sediment and cells of the marine thaumarchaeon Nitrosopumilus maritimus. The distribution of GDGT degradation products in environmental samples suggests that both biotic and abiotic processes act as sinks for GDGTs. More than a hundred newly recognized degradation products afford a view of the stepwise degradation of GDGT via (1) ether bond hydrolysis yielding hydroxyl isoprenoids, namely, GDGTol (glycerol dialkyl glycerol triether alcohol), GMGD (glycerol monobiphytanyl glycerol diether), GDD (glycerol dibiphytanol diether), GMM (glycerol monobiphytanol monoether) and bpdiol (biphytanic diol); (2) oxidation of isoprenoidal alcohols into corresponding carboxyl derivatives and (3) chain shortening to yield C39 and smaller isoprenoids. This plausible GDGT degradation pathway from glycerol ethers to isoprenoidal fatty acids provides the link to commonly detected head-to-head linked long chain isoprenoidal hydrocarbons in petroleum and sediment samples. The problematic C80 to C82 tetraacids that cause naphthenate deposits in some oil production facilities can be generated from H-shaped glycerol monoalkyl glycerol tetraethers (GMGTs) following the same process, as indicated by the distribution of related derivatives in hydrothermally influenced sediments.

  19. Impairment of cellulose- and cellobiose-degrading soil Bacteria by two acidic herbicides.

    PubMed

    Schellenberger, Stefanie; Drake, Harold L; Kolb, Steffen

    2012-02-01

    Herbicides have the potential to impair the metabolism of soil microorganisms. The current study addressed the toxic effect of bentazon and 4-chloro-2-methylphenoxyacetic acid on aerobic and anaerobic Bacteria that are involved in cellulose and cellobiose degradation in an agricultural soil. Aerobic saccharide degradation was reduced at concentrations of herbicides above environmental values. Microbial processes (e.g. fermentations, ferric iron reduction) that were linked to anaerobic cellulose and cellobiose degradation were reduced in the presence of both herbicides at concentrations above and at those that occur in crop field soil. 16S rRNA gene transcript numbers of total Bacteria, and selected bacterial taxa (Clostridia [Group I], Planctomycetaceae, and two uncultivated taxa of Bacteroidetes) decreased more in anoxic than in oxic cellulose-supplemented soil microcosms in the presence of both herbicides. Collectively, the results suggested that the metabolism of anaerobic cellulose-degrading Bacteria was impaired by typical in situ herbicide concentrations, whereas in situ concentrations did not impair metabolism of aerobic cellulose- and cellobiose-degrading soil Bacteria.

  20. Chemical nature and immunotoxicological properties of arachidonic acid degradation products formed by exposure to ozone.

    PubMed Central

    Madden, M C; Friedman, M; Hanley, N; Siegler, E; Quay, J; Becker, S; Devlin, R; Koren, H S

    1993-01-01

    Ozone (O3) exposure in vivo has been reported to degrade arachidonic acid (AA) in the lungs of rodents. The O3-degraded AA products may play a role in the responses to this toxicant. To study the chemical nature and biological activity of O3-exposed AA, we exposed AA in a cell-free, aqueous environment to air, 0.1 ppm O3, or 1.0 ppm O3 for 30-120 min. AA exposed to air was not degraded. All O3 exposures degraded > 98% of the AA to more polar products, which were predominantly aldehydic substances (as determined by reactivity with 2,4-dinitrophenylhydrazine and subsequent separation by HPLC) and hydrogen peroxide. The type and amount of aldehydic substances formed depended on the O3 concentration and exposure duration. A human bronchial epithelial cell line (BEAS-2B, S6 subclone) exposed in vitro to either 0.1 ppm or 1.0 ppm O3 for 1 hr produced AA-derived aldehydic substances, some of which eluted with similar retention times as the aldehydic substances derived from O3 degradation of AA in the cell-free system. In vitro, O3-degraded AA induced an increase in human peripheral blood polymorphonuclear leukocyte (PMN) polarization, decreased human peripheral blood T-lymphocyte proliferation in response to mitogens, and decreased human peripheral blood natural killer cell lysis of K562 target cells. The aldehydic substances, but not hydrogen peroxide, appeared to be the principal active agents responsible for the observed effects. O3-degraded AA may play a role in the PMN influx into lungs and in decreased T-lymphocyte mitogenesis and natural killer cell activity observed in humans and rodents exposed to O3. PMID:8354202

  1. Chemical nature and immunotoxicological properties of arachidonic acid degradation products formed by exposure to ozone

    SciTech Connect

    Madden, M.C.; Friedman, M.; Hanley, N.; Siegler, E.; Quay, J.; Becker, S.; Devlin, R.; Koren, H.S. )

    1993-06-01

    Ozone (O3) exposure in vivo has been reported to degrade arachidonic acid (AA) in the lungs of rodents. The O3-degraded AA products may play a role in the responses to this toxicant. To study the chemical nature and biological activity of O3-exposed AA, we exposed AA in a cell-free, aqueous environment to air, 0.1 ppm O3, or 1.0 ppm O3 for 30-120 min. AA exposed to air was not degraded. All O3 exposures degraded > 98% of the AA to more polar products, which were predominantly aldehydic substances (as determined by reactivity with 2,4-dinitrophenylhydrazine and subsequent separation by HPLC) and hydrogen peroxide. The type and amount of aldehydic substances formed depended on the O3 concentration and exposure duration. A human bronchial epithelial cell line (BEAS-2B, S6 subclone) exposed in vitro to either 0.1 ppm or 1.0 ppm O3 for 1 hr produced AA-derived aldehydic substances, some of which eluted with similar retention times as the aldehydic substances derived from O3 degradation of AA in the cell-free system. In vitro, O3-degraded AA induced an increase in human peripheral blood polymorphonuclear leukocyte (PMN) polarization, decreased human peripheral blood T-lymphocyte proliferation in response to mitogens, and decreased human peripheral blood natural killer cell lysis of K562 target cells. The aldehydic substances, but not hydrogen peroxide, appeared to be the principal active agents responsible for the observed effects. O3-degraded AA may play a role in the PMN influx into lungs and in decreased T-lymphocyte mitogenesis and natural killer cell activity observed in humans and rodents exposed to O3.

  2. Degradation of 2,4-dichlorophenoxyacetic acid by a halotolerant strain of Penicillium chrysogenum: antibiotic production.

    PubMed

    Ferreira-Guedes, Sumaya; Mendes, Benilde; Leitão, Ana Lúcia

    2012-01-01

    The extensive use of pesticides in agriculture has prompted intensive research on chemical and biological methods in order to protect contamination of water and soil resources. In this paper the degradation of the pesticide 2,4-dichlorophenoxyacetic acid by a Penicillium chrysogenum strain previously isolated from a salt mine was studied in batch cultures. Co-degradation of 2,4-dichlorophenoxyacetic acid with additives such as sugar and intermediates of pesticide metabolism was also investigated. Penicillium chrysogenum in solid medium was able to grow at concentrations up to 1000 mg/L of 2,4-dichlorophenoxyacetic acid (2,4-D) with sucrose. Meanwhile, supplementation of the solid medium with glucose and lactose led to fungal growth at concentrations up to 500 mg/L of herbicide. Batch cultures of 2,4-D at 100 mg/L were developed under aerobic conditions with the addition of glucose, lactose and sucrose, showing sucrose as the best additional carbon source. The 2,4-D removal was quantified by liquid chromatography. The fungus was able to use 2,4-D as the sole carbon and energy source under 0%, 2% and 5.9% NaCl. The greatest 2,4-D degradation efficiency was found using alpha-ketoglutarate and ascorbic acid as co-substrates under 2% NaCl at pH 7. Penicillin production was evaluated in submerged cultures by bioassay, and higher amounts of beta-lactam antibiotic were produced when the herbicide was alone. Taking into account the ability of P. chrysogenum CLONA2 to degrade aromatic compounds, this strain could be an interesting tool for 2,4-D herbicide remediation in saline environments.

  3. Root exudates modify bacterial diversity of phenanthrene degraders in PAH-polluted soil but not phenanthrene degradation rates.

    PubMed

    Cébron, Aurélie; Louvel, Brice; Faure, Pierre; France-Lanord, Christian; Chen, Yin; Murrell, J Colin; Leyval, Corinne

    2011-03-01

    To determine whether the diversity of phenanthrene-degrading bacteria in an aged polycyclic aromatic hydrocarbon (PAH) contaminated soil is affected by the addition of plant root exudates, DNA stable isotope probing (SIP) was used. Microcosms of soil with and without addition of ryegrass exudates and with ¹³C-labelled phenanthrene (PHE) were monitored over 12 days. PHE degradation was slightly delayed in the presence of added exudate after 4 days of incubation. After 12 days, 68% of added PHE disappeared both with and without exudate. Carbon balance using isotopic analyses indicated that a part of the ¹³C-PHE was not totally mineralized as ¹³CO₂ but unidentified ¹³C-compounds (i.e. ¹³C-PHE or ¹³C-labelled metabolites) were trapped into the soil matrix. Temporal thermal gradient gel electrophoresis (TTGE) analyses of 16S rRNA genes were performed on recovered ¹³C-enriched DNA fractions. 16S rRNA gene banding showed the impact of root exudates on diversity of PHE-degrading bacteria. With PHE as a fresh sole carbon source, Pseudoxanthomonas sp. and Microbacterium sp. were the major PHE degraders, while in the presence of exudates, Pseudomonas sp. and Arthrobacter sp. were favoured. These two different PHE-degrading bacterial populations were also distinguished through detection of PAH-ring hydroxylating dioxygenase (PAH-RHD(α)) genes by real-time PCR. Root exudates favoured the development of a higher diversity of bacteria and increased the abundance of bacteria containing known PAH-RHD(α) genes.

  4. Abiotic Degradation Rates for Carbon Tetrachloride and Chloroform: Progress in FY 2010

    SciTech Connect

    Amonette, James E.; Jeffers, Peter M.; Qafoku, Odeta; Russell, Colleen K.; Humphrys, Daniel R.; Wietsma, Thomas W.; Truex, Michael J.

    2010-12-08

    This report documents the progress made through FY 2010 on a project initiated in FY 2006 to help address uncertainties related to the rates of hydrolysis in groundwater at the Hanford Site for carbon tetrachloride (CT) and chloroform (CF). The study also explores the possible effects of contact with minerals and sediment (i.e., heterogeneous hydrolysis) on these rates. The research was initiated to decrease the uncertainties in abiotic degradation rates of CT and chloroform CF associated with temperature and possible heterogeneous effects. After 2 years of data collection, the first evidence for heterogeneous effects was identified for hydrolysis of CT, and preliminary evidence for the effects of different mineral types on CF hydrolysis rates also was reported. The CT data showed no difference among mineral types, whereas significant differences were seen in the CF results, perhaps due to the fact that CF hydrolyzes by both neutral and base-catalyzed mechanisms whereas CT follows only the neutral hydrolysis path. In this report, we review the project objectives, organization, and technical approaches taken, update the status and results of the hydrolysis-rate experiments after 4 years of experimentation (i.e., through FY 2010), and provide a brief discussion of how these results add to scientific understanding of the behavior of the CT/CF plume at the Hanford Site.

  5. 2('),3(')-didehydro-2('),3(')-dideoxynucleosides are degraded to furfuryl alcohol under acidic conditions.

    PubMed

    Shi, Junxing; Ray, Adrian S; Mathew, Judy S; Anderson, Karen S; Chu, Chung K; Schinazi, Raymond F

    2004-05-03

    2('),3(')-Didehydro-2('),3(')-dideoxynucleosides are clinically relevant antiviral agents. These nucleosides could be degraded under acidic conditions. Acidic stability studies showed the D4N had the following increasing stability order: D4Gacidic cleavage of D4-nucleosides. The cleavage products were characterized as furfuryl alcohol and the corresponding nucleobase. Furfuryl alcohol is an agent found in many everyday food products. The biological results demonstrated that furfuryl alcohol had neither anti-HIV activity nor cytotoxicity in vitro, suggesting the acid instability of D4-nucleosides is unlikely to have an impact on the toxicity of these nucleoside analogs in humans.

  6. Enhanced degradation of Herbicide Isoproturon in wheat rhizosphere by salicylic acid.

    PubMed

    Lu, Yi Chen; Zhang, Shuang; Miao, Shan Shan; Jiang, Chen; Huang, Meng Tian; Liu, Ying; Yang, Hong

    2015-01-14

    This study investigated the herbicide isoproturon (IPU) residues in soil, where wheat was cultivated and sprayed with salicylic acid (SA). Provision of SA led to a lower level of IPU residues in rhizosphere soil compared to IPU treatment alone. Root exudation of tartaric acid, malic acid, and oxalic acids was enhanced in rhizosphere soil with SA-treated wheat. We examined the microbial population (e.g., biomass and phospholipid fatty acid), microbial structure, and soil enzyme (catalase, phenol oxidase, and dehydrogenase) activities, all of which are associated with soil activity and were activated in rhizosphere soil of SA-treated wheat roots. We further assessed the correlation matrix and principal component to figure out the association between the IPU degradation and soil activity. Finally, six IPU degraded products (derivatives) in rhizosphere soil were characterized using ultraperformance liquid chromatography with a quadrupole-time-of-flight tandem mass spectrometer (UPLC/Q-TOF-MS/MS). A relatively higher level of IPU derivatives was identified in soil with SA-treated wheat than in soil without SA-treated wheat plants.

  7. Degradation of vanillic acid and production of guaiacol by microorganisms isolated from cork samples.

    PubMed

    Alvarez-Rodríguez, María Luisa; Belloch, Carmela; Villa, Mercedes; Uruburu, Federico; Larriba, Germán; Coque, Juan José R

    2003-03-14

    The presence of guaiacol in cork stoppers is responsible for some cases of cork taint causing unpleasant alterations to wine. We have performed a characterization of the cork-associated microbiota by isolating 55 different microorganisms: eight yeast, 14 filamentous fungi or molds, 13 actinomycetes and 20 non-filamentous bacteria. A screening for degradation of vanillic acid and guaiacol production showed that none of the filamentous fungi could achieve any of these processes. By contrast, five of the eight yeast strains isolated were able to degrade vanillic acid, although it was not converted to guaiacol. Guaiacol production was only detected in four bacterial strains: one isolate of Bacillus subtilis and three actinomycetes, Streptomyces sp. A3, Streptomyces sp. A5 and Streptomyces sp. A13, were able to accumulate this compound in both liquid media and cultures over cork. These results suggest that guaiacol-mediated cork taint should be attributed to the degradative action of vanillic acid by bacterial strains growing on cork.

  8. Optimized photocatalytic degradation of caffeic acid by sol-gel TiO₂.

    PubMed

    García-Montelongo, Xiomara L; Martínez-de la Cruz, Azael; Contreras, David; Mansilla, Héctor D

    2015-01-01

    TiO₂anatase powder was prepared by means of the sol-gel method with titanium(IV) butoxide as precursor. The formation of a tetragonal crystal structure of TiO₂anatase at 500 °C was confirmed by X-ray powder diffraction. The characterization of the samples synthesized was complemented by scanning electron microscopy, diffuse reflectance infrared Fourier transform spectroscopy, nitrogen adsorption-desorption isotherms (Brunauer-Emmett-Teller) and diffuse reflectance spectroscopy. The photocatalytic activity of the TiO₂anatase powder was evaluated in the degradation of caffeic acid in aqueous solution under ultraviolet radiation. A central composite circumscribed design was used to assess the weight of the experimental variables, pH and amount of catalyst in the percentage of caffeic acid degraded and the optimal conditions. The optimized conditions were found to be pH = 5.2 and a load of TiO₂of 1.1 g L⁻¹. Under these conditions more than 90% of caffeic acid degradation was achieved after 30 min of lamp irradiation. At this time the mineralization reached was almost 60%.

  9. The Degradation of 14C-Glutamic Acid by L-Glutamic Acid Decarboxylase.

    ERIC Educational Resources Information Center

    Dougherty, Charles M; Dayan, Jean

    1982-01-01

    Describes procedures and semi-micro reaction apparatus (carbon dioxide trap) to demonstrate how a particular enzyme (L-Glutamic acid decarboxylase) may be used to determine the site or sites of labeling in its substrate (carbon-14 labeled glutamic acid). Includes calculations, solutions, and reagents used. (Author/SK)

  10. Aspartic Acid Racemization and Collagen Degradation Markers Reveal an Accumulation of Damage in Tendon Collagen That Is Enhanced with Aging*

    PubMed Central

    Thorpe, Chavaunne T.; Streeter, Ian; Pinchbeck, Gina L.; Goodship, Allen E.; Clegg, Peter D.; Birch, Helen L.

    2010-01-01

    Little is known about the rate at which protein turnover occurs in living tendon and whether the rate differs between tendons with different physiological roles. In this study, we have quantified the racemization of aspartic acid to calculate the age of the collagenous and non-collagenous components of the high strain injury-prone superficial digital flexor tendon (SDFT) and low strain rarely injured common digital extensor tendon (CDET) in a group of horses with a wide age range. In addition, the turnover of collagen was assessed indirectly by measuring the levels of collagen degradation markers (collagenase-generated neoepitope and cross-linked telopeptide of type I collagen). The fractional increase in d-Asp was similar (p = 0.7) in the SDFT (5.87 × 10−4/year) and CDET (5.82 × 10−4/year) tissue, and d/l-Asp ratios showed a good correlation with pentosidine levels. We calculated a mean (±S.E.) collagen half-life of 197.53 (±18.23) years for the SDFT, which increased significantly with horse age (p = 0.03) and was significantly (p < 0.001) higher than that for the CDET (34.03 (±3.39) years). Using similar calculations, the half-life of non-collagenous protein was 2.18 (±0.41) years in the SDFT and was significantly (p = 0.04) lower than the value of 3.51 (±0.51) years for the CDET. Collagen degradation markers were higher in the CDET and suggested an accumulation of partially degraded collagen within the matrix with aging in the SDFT. We propose that increased susceptibility to injury in older individuals results from an inability to remove partially degraded collagen from the matrix leading to reduced mechanical competence. PMID:20308077

  11. Trifluoroacetic Acid from Degradation of HCFCs and HFCs: A Three-dimensional Modeling Study

    NASA Technical Reports Server (NTRS)

    Kotamarthi, V. R.; Rodriguez, J. M.; Ko, M. K. W.; Tromp, T. K.; Sze, N. D.

    1998-01-01

    Trifluoroacetic acid (TFA; CF3 COOH) is produced by the degradation of the halocarbon replacements HFC-134a, HCFC-124, and HCFC-123. The formation of TFA occurs by HFC/HCFC reacting with OH to yield CF3COX (X = F or CI), followed by in-cloud hydrolysis of CF3COX to form TFA. The TFA formed in the clouds may be reevaporated but is finally deposited onto the surface by washout or dry deposition. Concern has been expressed about the possible long-term accumulation of TFA in certain aquatic environments, pointing to the need to obtain information on the concentrations of TFA in rainwater over scales ranging from local to continental. Based on projected concentrations for HFC-134a, HCFC-124, and HCFC-123 of 80, 10, and 1 pptv in the year 2010, mass conservation arguments imply an annually averaged global concentration of 0.16 microg/L if washout were the only removal mechanism for TFA. We present 3-D simulations of the HFC/HCFC precursors of TFA that include the rates of formation and deposition of TFA based on assumed future emissions. An established (GISS/Harvard/ UCI) but coarse-resolution (8 deg latitude by 10 deg longitude) chemical transport model was used. The anually averaged rainwater concentration of 0.12 gg/L (global) was calculated for the year 2010, when both washout and dry deposition are included as the loss mechanism for TFA from the atmosphere. For some large regions in midnorthern latitudes, values are larger, 0.15-0.20 microg/L. The highest monthly averaged rainwater concentrations of TFA for northern midlatitudes were calculated for the month of July, corresponding to 0.3-0.45 microg/L in parts of North America and Europe. Recent laboratory experiments have suggested that a substantial amount of vibrationally excited CF3CHFO is produced in the degradation of HFC-134a, decreasing the yield of TFA from this compound by 60%. This decrease would reduce the calculated amounts of TFA in rainwater in the year 2010 by 26%, for the same projected

  12. Trifluoroacetic Acid from Degradation of HCFCs and HFCs: A Three-Dimensional Modeling Study. Appendix P

    NASA Technical Reports Server (NTRS)

    Kotamarthi, V. R.; Rodriquez, J. M.; Ko, M. K. W.; Tromp, T. K.; Sze, N. D.; Prather, Michael J.

    1998-01-01

    Trifluoroacetic acid (TFA; CF3 COOH) is produced by the degradation of the halocarbon replacements HFC-134a, HCFC-124, and HCFC-123. The formation of TFA occurs by HFC/HCFC reacting with OH to yield CF3COX (X = F or CI), followed by in-cloud hydrolysis of CF to form TFA. The TFA formed in the clouds may be reevaporated but is finally deposited onto the surface by washout or dry deposition. Concern has been expressed about the possible long-term accumulation of TFA in certain aquatic environments, pointing to the need to obtain information on the concentrations of TFA in rainwater over scales ranging from local to continental. Based on projected concentrations for HFC-134a, HCFC-124, and HCFC-123 of 80, 10, and 1 pptv in the year 2010, mass conservation arguments imply an annually averaged global concentration of 0.16 micro g/L if washout were the only removal mechanism for TFA. We present 3-D simulations of the HFC/HCFC precursors of TFA that include the rates of formation and deposition of TFA based on assumed future emissions. An established (GISS[Harvard/ UCI) but coarse-resolution (8 deg latitude by 10 deg longitude) chemical transport model was used. The annually averaged rainwater concentration of 0.12 micro g/L (global) was calculated for the year 2010, when both washout and dry deposition are included as the loss mechanism for TFA from the atmosphere. For some large regions in midnorthern latitudes, values are larger. 0.15-0.20 micro g/L. The highest monthly averaged rainwater concentrations of TFA for northern midlatitudes were calculated for the month of July, corresponding to 0.3 - 0.45 micro g/L in parts of North America and Europe. Recent laboratory experiments have suggested that a substantial amount of vibrationally excited CF3CHFO is produced in the degradation of HFC-134a, decreasing the yield of TFA from this compound by 60%. This decrease would reduce the calculated amounts of TFA in rainwater in the year 2010 by 26%, for the same projected

  13. Trifluoroacetic Acid from Degradation of HCFCs and HFCs: A Three-Dimensional Modeling Study

    NASA Technical Reports Server (NTRS)

    Kotamarthi, V. R.; Rodriquez, J. M.; Ko, M. K. W.; Tromp, T. K.; Sze, N. D.

    1998-01-01

    Trifluoroacetic acid (TFA; CF3COOH) is produced by the degradation of the halocarbon replacements HFC-134a, HCFC-124, and HCFC-123. The formation of TFA occurs by HFC/HCFC reacting with OH to yield CF3COX (X = F or CI), followed by in-cloud hydrolysis of CF3COX to form TFA. The TFA formed in the clouds may be reevaporated but is finally deposited onto the surface by washout or dry deposition. Concern has been expressed about the possible long-term accumulation of TFA in certain aquatic environments, pointing to the need to obtain information on the concentrations of TFA in rainwater over scales ranging from local to continental. Based on projected concentrations for HFC-134a, HCFC-124, and HCFC-123 of 80, 10, and 1 pptv in the year 2010, mass conservation arguments imply an annually averaged global concentration of 0.16 micro g/L if washout were the only removal mechanism for TFA. We present 3-D simulations of the HFC/HCFC precursors of TFA that include the rates of formation and deposition of TFA based on assumed future emissions. An established (GISS/Harvard/ UCI) but coarse-resolution (8 deg latitude by 10 deg longitude) chemical transport model was used. The annually averaged rainwater concentration of 0.12 micro g/L (global) was calculated for the year 2010, when both washout and dry deposition are included as the loss mechanism for TFA from the atmosphere. For some large regions in midnorthern latitudes, values are larger, 0.15-0.20 micro g/L. The highest monthly averaged rainwater concentrations of TFA for northern midlatitudes were calculated for the month of July, corresponding to 0.3-0.45 micro g/L in parts of North America and Europe. Recent laboratory experiments have suggested that a substantial amount of vibrationally excited CF3CHFO is produced in the degradation of HFC-134a, decreasing the yield of TFA from this compound by 60%. This decrease would reduce the calculated amounts of TFA in rainwater in the year 2010 by 26%, for the same projected

  14. Impact of folic acid supplementation on single- and double-stranded RNA degradation in human colostrum and mature milk.

    PubMed

    Kocic, Gordana; Bjelakovic, Ljiljana; Bjelakovic, Bojko; Jevtoci-Stoimenov, Tatjana; Sokolovic, Dusan; Cvetkovic, Tatjana; Kocic, Hristina; Stojanovic, Svetlana; Langerholc, Tomaz; Jonovic, Marina

    2014-07-01

    Sufficient intake of folic acid is necessary for normal embryogenesis, fetal, and neonatal development. Folic acid facilitates nucleic acid internalization, and protects cellular DNA from nuclease degradation. Human milk contains enzymes, antimicrobial proteins, and antibodies, along with macrophages, that protect against infections and allergies. However, little to no information is available on the effects of folic acid supplementation on degradation of nucleic acids in human milk. In the present study, we aimed to determine the RNase activity (free and inhibitor-bound) in colostrum and mature milk, following folic acid supplementation. The study design included a total of 59 women, 27 of whom received 400 μg of folic acid daily periconceptionally and after. Folic acid supplementation increased the free RNase and polyadenylase activity following lactation. However, the increased RNase activity was not due to de novo enzyme synthesis, as the inhibitor-bound (latent) RNase activity was significantly lower and disappeared after one month. Folic acid reduced RNase activity by using double-stranded RNA as substrate. Data suggests that folic acid supplementation may improve viral RNAs degradation and mRNA degradation, but not dsRNA degradation, preserving in this way the antiviral defense.

  15. Biodegradation of 5-chloro-2-picolinic acid by novel identified co-metabolizing degrader Achromobacter sp. f1.

    PubMed

    Wu, Zhi-Guo; Wang, Fang; Ning, Li-Qun; Stedtfeld, Robert D; Yang, Zong-Zheng; Cao, Jing-Guo; Sheng, Hong-Jie; Jiang, Xin

    2017-02-02

    Several bacteria have been isolated to degrade 4-chloronitrobenzene. Degradation of 4-chloronitrobenzene by Cupriavidus sp. D4 produces 5-chloro-2-picolinic acid as a dead-end by-product, a potential pollutant. To date, no bacterium that degrades 5-chloro-2-picolinic acid has been reported. Strain f1, isolated from a soil polluted by 4-chloronitrobenzene, was able to co-metabolize 5-chloro-2-picolinic acid in the presence of ethanol or other appropriate carbon sources. The strain was identified as Achromobacter sp. based on its physiological, biochemical characteristics, and 16S rRNA gene sequence analysis. The organism completely degraded 50, 100 and 200 mg L(-1) of 5-chloro-2-picolinic acid within 48, 60, and 72 h, respectively. During the degradation of 5-chloro-2-picolinic acid, Cl(-) was released. The initial metabolic product of 5-chloro-2-picolinic acid was identified as 6-hydroxy-5-chloro-2-picolinic acid by LC-MS and NMR. Using a mixed culture of Achromobacter sp. f1 and Cupriavidus sp. D4 for degradation of 4-chloronitrobenzen, 5-chloro-2-picolinic acid did not accumulate. Results infer that Achromobacter sp. f1 can be used for complete biodegradation of 4-chloronitrobenzene in remedial applications.

  16. Regulation of Leaf Starch Degradation by Abscisic Acid Is Important for Osmotic Stress Tolerance in Plants[OPEN

    PubMed Central

    Thalmann, Matthias; Pazmino, Diana; Seung, David; Horrer, Daniel; Nigro, Arianna; Meier, Tiago; Zeeman, Samuel C.; Santelia, Diana

    2016-01-01

    Starch serves functions that range over a timescale of minutes to years, according to the cell type from which it is derived. In guard cells, starch is rapidly mobilized by the synergistic action of β-AMYLASE1 (BAM1) and α-AMYLASE3 (AMY3) to promote stomatal opening. In the leaves, starch typically accumulates gradually during the day and is degraded at night by BAM3 to support heterotrophic metabolism. During osmotic stress, starch is degraded in the light by stress-activated BAM1 to release sugar and sugar-derived osmolytes. Here, we report that AMY3 is also involved in stress-induced starch degradation. Recently isolated Arabidopsis thaliana amy3 bam1 double mutants are hypersensitive to osmotic stress, showing impaired root growth. amy3 bam1 plants close their stomata under osmotic stress at similar rates as the wild type but fail to mobilize starch in the leaves. 14C labeling showed that amy3 bam1 plants have reduced carbon export to the root, affecting osmolyte accumulation and root growth during stress. Using genetic approaches, we further demonstrate that abscisic acid controls the activity of BAM1 and AMY3 in leaves under osmotic stress through the AREB/ABF-SnRK2 kinase-signaling pathway. We propose that differential regulation and isoform subfunctionalization define starch-adaptive plasticity, ensuring an optimal carbon supply for continued growth under an ever-changing environment. PMID:27436713

  17. Changes in fatty acid composition of Stenotrophomonas maltophilia KB2 during co-metabolic degradation of monochlorophenols.

    PubMed

    Nowak, Agnieszka; Greń, Izabela; Mrozik, Agnieszka

    2016-12-01

    The changes in the cellular fatty acid composition of Stenotrophomonas maltophilia KB2 during co-metabolic degradation of monochlorophenols in the presence of phenol as well as its adaptive mechanisms to these compounds were studied. It was found that bacteria were capable of degrading 4-chlorophenol (4-CP) completely in the presence of phenol, while 2-chlorophenol (2-CP) and 3-chlorophenol (3-CP) they degraded partially. The analysis of the fatty acid profiles indicated that adaptive mechanisms of bacteria depended on earlier exposure to phenol, which isomer they degraded, and on incubation time. In bacteria unexposed to phenol the permeability and structure of their membranes could be modified through the increase of hydroxylated and cyclopropane fatty acids, and straight-chain and hydroxylated fatty acids under 2-CP, 3-CP and 4-CP exposure, respectively. In the exposed cells, regardless of the isomer they degraded, the most important changes were connected with the increase of the contribution of branched fatty acid on day 4 and the content of hydroxylated fatty acids on day 7. The changes, particularly in the proportion of branched fatty acids, could be a good indicator for assessing the progress of the degradation of monochlorophenols by S. maltophilia KB2. In comparison, in phenol-degrading cells the increase of cyclopropane and straight-chain fatty acid content was established. These findings indicated the degradative potential of the tested strain towards the co-metabolic degradation of persistent chlorophenols, and extended the current knowledge about the adaptive mechanisms of these bacteria to such chemicals.

  18. Microbial degradation of 2,4-dichlorophenoxyacetic acid on the Greenland ice sheet.

    PubMed

    Stibal, Marek; Bælum, Jacob; Holben, William E; Sørensen, Sebastian R; Jensen, Anders; Jacobsen, Carsten S

    2012-08-01

    The Greenland ice sheet (GrIS) receives organic carbon (OC) of anthropogenic origin, including pesticides, from the atmosphere and/or local sources, and the fate of these compounds in the ice is currently unknown. The ability of supraglacial heterotrophic microbes to mineralize different types of OC is likely a significant factor determining the fate of anthropogenic OC on the ice sheet. Here we determine the potential of the microbial community from the surface of the GrIS to mineralize the widely used herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Surface ice cores were collected and incubated for up to 529 days in microcosms simulating in situ conditions. Mineralization of side chain- and ring-labeled [(14)C]2,4-D was measured in the samples, and quantitative PCR targeting the tfdA genes in total DNA extracted from the ice after the experiment was performed. We show that the supraglacial microbial community on the GrIS contains microbes that are capable of degrading 2,4-D and that they are likely present in very low numbers. They can mineralize 2,4-D at a rate of up to 1 nmol per m(2) per day, equivalent to ∼26 ng C m(-2) day(-1). Thus, the GrIS should not be considered a mere reservoir of all atmospheric contaminants, as it is likely that some deposited compounds will be removed from the system via biodegradation processes before their potential release due to the accelerated melting of the ice sheet.

  19. Microbial Degradation of 2,4-Dichlorophenoxyacetic Acid on the Greenland Ice Sheet

    PubMed Central

    Stibal, Marek; Bælum, Jacob; Holben, William E.; Sørensen, Sebastian R.; Jensen, Anders

    2012-01-01

    The Greenland ice sheet (GrIS) receives organic carbon (OC) of anthropogenic origin, including pesticides, from the atmosphere and/or local sources, and the fate of these compounds in the ice is currently unknown. The ability of supraglacial heterotrophic microbes to mineralize different types of OC is likely a significant factor determining the fate of anthropogenic OC on the ice sheet. Here we determine the potential of the microbial community from the surface of the GrIS to mineralize the widely used herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Surface ice cores were collected and incubated for up to 529 days in microcosms simulating in situ conditions. Mineralization of side chain- and ring-labeled [14C]2,4-D was measured in the samples, and quantitative PCR targeting the tfdA genes in total DNA extracted from the ice after the experiment was performed. We show that the supraglacial microbial community on the GrIS contains microbes that are capable of degrading 2,4-D and that they are likely present in very low numbers. They can mineralize 2,4-D at a rate of up to 1 nmol per m2 per day, equivalent to ∼26 ng C m−2 day−1. Thus, the GrIS should not be considered a mere reservoir of all atmospheric contaminants, as it is likely that some deposited compounds will be removed from the system via biodegradation processes before their potential release due to the accelerated melting of the ice sheet. PMID:22582066

  20. Degradation of dichloroacetic acid in homogeneous aqueous media employing ozone and UVC radiation.

    PubMed

    Lovato, María Eugenia; Martín, Carlos A; Cassano, Alberto E

    2011-03-02

    A tentative workable mechanism for dichloroacetic acid decomposition (DCA) in aqueous media employing ozone and UVC radiation has been developed. All experiments were made in a homogeneous medium under assured kinetic control regime. Under no circumstances did a headspace exist in the reactor volume. The starting point of the reaction with UVC radiation was always under the prerequisite of a confirmed state of initial equilibrium conditions for the mixture water-ozone-oxygen at 20 °C. The explored variables were: (i) DCA initial concentration, (ii) ozone concentration and (iii) fluence rate at the reactor window. The model comprises three parallel reactions: (1) direct photolysis, (2) direct ozonation and (3) ozone + UVC degradation. Complete DCA removal was achieved, and the mass balance, considering DCA disappearance and chloride ion formation, closed within very small error. The combination of ozone and UVC radiation produces a significant amount of hydrogen peroxide as an important reaction by-product. The direct photolysis can be well represented with a six step reaction sequence. The direct ozonation mechanism comprises 22 steps and, with the entire set of kinetic constants completed in this work, it is independent of the reaction pH in the range from 3 to 6.3. Lastly, the associated use of ozone and UVC radiation becomes necessary to consider the existence of radiation absorption by three species, namely DCA, ozone and hydrogen peroxide. The developed system, including the three parallel reactions, led to the proposal of a 37 step reaction mechanism. Finally the reaction kinetics, the mass balances and the radiation field corresponding to this complex system were rigorously modeled and the most significant features of the mathematical representation are briefly described. The simulation results rendered from this model agree very well with the measured experimental data. This outcome will be essential for deriving a complete reactor model that must be

  1. Raman spectroscopy and capillary zone electrophoresis for the analysis of degradation processes in commercial effervescent tablets containing acetylsalicylic acid and ascorbic acid.

    PubMed

    Neuberger, Sabine; Jooß, Kevin; Flottmann, Dirk; Scriba, Gerhard; Neusüß, Christian

    2017-02-05

    In order to ensure the stability of pharmaceutical products appropriate manufacturing and storage conditions are required. In general, the degradation of active pharmaceutical ingredients (APIs) and subsequent formation of degradation products affect the pharmaceutical quality. Thus, a fast and effective detection and characterization of these substances is mandatory. Here, the applicability of Raman spectroscopy and CZE for the characterization of the degradation of effervescent tablets containing acetylsalicylic acid (ASA) and ascorbic acid (AA) was evaluated. Therefore, a degradation study was performed analyzing tablets from two different manufacturers at varying conditions (relative humidity (RH) 33%, 52% and 75% at 30°C). Raman spectroscopy combined with principal component analysis could be successfully applied for the fast and easy discrimination of non-degraded and degraded effervescent tablets after a storage period of approximately 24h (RH 52%). Nevertheless, a clear identification or quantification of APIs and degradation products within the analyzed tablets was not possible, i.a. due to missing reference materials. CZE-UV enabled the quantification of the APIs (ASA, AA) and related degradation products (salicylic acid (SA); semi-quantitative also mono- and diacetylated AA) within the complex tablet mixtures. The higher the RH, the faster the degradation of ASA and AA as well as the formation of the degradation products. Mono- and diacetylated AA are major primary degradation products of AA for the applied effervescent tablets. A significant degradation of the APIs was detected earlier by CZE (6-12h, RH 52%) than by Raman spectroscopy. Summarized, Raman spectroscopy is well-suited as quick test to detect degradation of these tablets and CZE can be utilized for further detailed characterization and quantification of specific APIs and related degradation products.

  2. Degradation of emerging contaminants from water under natural sunlight: The effect of season, pH, humic acids and nitrate and identification of photodegradation by-products.

    PubMed

    Koumaki, Elena; Mamais, Daniel; Noutsopoulos, Constantinos; Nika, Maria-Christina; Bletsou, Anna A; Thomaidis, Nikolaos S; Eftaxias, Alexander; Stratogianni, Georgia

    2015-11-01

    Both photodegradation and hydrolysis of non-steroidal anti-inflammatory drugs (NSAIDs) and endocrine disrupting chemicals (EDCs) were investigated in order to evaluate their photochemical fate in aquatic environment and to assess the effect of season and specific characteristics of water (pH, humic acids and nitrate concentration) on the removal of target EDCs and NSAIDs through photodegradation. An additional objective was the identification of the photodegradation by-products of specific NSAIDs and their dependence on irradiation time. Selected compounds' transformation was investigated under natural sunlight radiation while control experiments were conducted in the dark. As expected, most of compounds' degradation rate decreased with decreasing light intensity between two different experimental periods. Most of the tested compounds exhibited different rates of degradation during direct and indirect photolysis. The degradation rate of the selected compounds increased in the presence of NO3(-) and the photodegradation rate was higher for some compounds in alkaline than in acidic solution. The effect of humic acids' presence in the water depends on the absorbance spectrum of the compound and the produced photosensitizers. More specifically, humic acids act as inner filter toward most of the selected NSAIDs and as photosensitizers toward most of the EDCs. The results of the irradiation experiments in the presence of both humic acids and NO3(-), indicate that the direct photolysis is much more efficient than indirect photochemical processes. Finally, several degradation by-products of ketoprofen and diclofenac were identified in the samples, exposed to sunlight. The dependence of these by-products on radiation time is also demonstrated.

  3. Evaluation of reversible and irreversible degradation rates of polymer electrolyte membrane fuel cells tested in automotive conditions

    NASA Astrophysics Data System (ADS)

    Gazdzick, Pawel; Mitzel, Jens; Garcia Sanchez, Daniel; Schulze, Mathias; Friedrich, K. Andreas

    2016-09-01

    This work provides single cell durability tests of membrane electrode assemblies in dynamic operation regularly interrupted by recovery procedures for the removal of reversible voltage losses. Degradation rates at different loads in one single test can be determined from these tests. Hence, it is possible to report degradation rates versus current density instead of a single degradation rate value. A clear discrimination between reversible and irreversible voltage loss rates is provided. The irreversible degradation rate can be described by a linear regression of voltage values after the recovery steps. Using voltage values before refresh is less adequate due to possible impacts of reversible effects. The reversible contribution to the voltage decay is dominated by an exponential decay after restart, eventually turning into a linear one. A linear-exponential function is proposed to fit the reversible voltage degradation. Due to this function, the degradation behavior of an automotive fuel cell can be described correctly during the first hours after restart. The fit parameters decay constant, exponential amplitude and linear slope are evaluated. Eventually, the reasons for the voltage recovery during shutdown are analyzed showing that ionomer effects in the catalyst layer and/or membrane seem to be the key factor in this process.

  4. Novel Extracellular PHB Depolymerase from Streptomyces ascomycinicus: PHB Copolymers Degradation in Acidic Conditions

    PubMed Central

    García-Hidalgo, Javier; Hormigo, Daniel; Arroyo, Miguel; de la Mata, Isabel

    2013-01-01

    The ascomycin-producer strain Streptomyces ascomycinicus has been proven to be an extracellular poly(R)-3-hydroxybutyrate (PHB) degrader. The fkbU gene, encoding a PHB depolymerase (PhaZSa), has been cloned in E. coli and Rhodococcus sp. T104 strains for gene expression. Gram-positive host Rhodococcus sp. T104 was able to produce and secrete to the extracellular medium an active protein form. PhaZSa was purified by two hydrophobic interaction chromatographic steps, and afterwards was biochemically as well as structurally characterized. The enzyme was found to be a monomer with a molecular mass of 48.4 kDa, and displayed highest activity at 45°C and pH 6, thus being the first PHB depolymerase from a gram-positive bacterium presenting an acidic pH optimum. The PHB depolymerase activity of PhaZSa was increased in the presence of divalent cations due to non-essential activation, and also in the presence of methyl-β-cyclodextrin and PEG 3350. Protein structure was analyzed, revealing a globular shape with an alpha-beta hydrolase fold. The amino acids comprising the catalytic triad, Ser131-Asp209-His269, were identified by multiple sequence alignment, chemical modification of amino acids and site-directed mutagenesis. These structural results supported the proposal of a three-dimensional model for this depolymerase. PhaZSa was able to degrade PHB, but also demonstrated its ability to degrade films made of PHB, PHBV copolymers and a blend of PHB and starch (7∶3 proportion wt/wt). The features shown by PhaZSa make it an interesting candidate for industrial applications involving PHB degradation. PMID:23951224

  5. Novel extracellular PHB depolymerase from Streptomyces ascomycinicus: PHB copolymers degradation in acidic conditions.

    PubMed

    García-Hidalgo, Javier; Hormigo, Daniel; Arroyo, Miguel; de la Mata, Isabel

    2013-01-01

    The ascomycin-producer strain Streptomyces ascomycinicus has been proven to be an extracellular poly(R)-3-hydroxybutyrate (PHB) degrader. The fkbU gene, encoding a PHB depolymerase (PhaZ Sa ), has been cloned in E. coli and Rhodococcus sp. T104 strains for gene expression. Gram-positive host Rhodococcus sp. T104 was able to produce and secrete to the extracellular medium an active protein form. PhaZ Sa was purified by two hydrophobic interaction chromatographic steps, and afterwards was biochemically as well as structurally characterized. The enzyme was found to be a monomer with a molecular mass of 48.4 kDa, and displayed highest activity at 45°C and pH 6, thus being the first PHB depolymerase from a gram-positive bacterium presenting an acidic pH optimum. The PHB depolymerase activity of PhaZ Sa was increased in the presence of divalent cations due to non-essential activation, and also in the presence of methyl-β-cyclodextrin and PEG 3350. Protein structure was analyzed, revealing a globular shape with an alpha-beta hydrolase fold. The amino acids comprising the catalytic triad, Ser(131)-Asp(209)-His(269), were identified by multiple sequence alignment, chemical modification of amino acids and site-directed mutagenesis. These structural results supported the proposal of a three-dimensional model for this depolymerase. PhaZ Sa was able to degrade PHB, but also demonstrated its ability to degrade films made of PHB, PHBV copolymers and a blend of PHB and starch (7∶3 proportion wt/wt). The features shown by PhaZ Sa make it an interesting candidate for industrial applications involving PHB degradation.

  6. Micro-mechanism and rate constants for OH-initiated degradation of methomyl in atmosphere.

    PubMed

    Wu, Xiuchao; Sun, Xiaomin; Zhang, Chenxi; Gong, Chen; Hu, Jingtian

    2014-07-01

    The atmospheric degradation reactions of the two isomers of methomyl (MTL) initiated by OH radical in the presence of O2, NO and H2O have been investigated by density functional theory (DFT). The calculations were all carried out at MPWB1K level. The geometrical parameters and vibrational frequencies of stationary points were calculated with 6-31+G (d, p) basis sets. Single-point energy calculations were performed with 6-311+G (3df, 2p) basis sets. Profiles of the potential energy surface were constructed and all possible channels involved in the reactions were discussed. The rate constants of main elementary reactions were calculated over a temperature range of 200-400 K and mostly fitted to Arrhenius formulas. The atmospheric lifetimes of reaction species were discussed for the first time, which can be applied to the study on model simulation and management of hazardous materials.

  7. Effect of acidic solutions on the surface degradation of a micro-hybrid composite resin.

    PubMed

    Münchow, Eliseu A; Ferreira, Ana Cláudia A; Machado, Raissa M M; Ramos, Tatiana S; Rodrigues-Junior, Sinval A; Zanchi, Cesar H

    2014-01-01

    Composite resins may undergo wear by the action of chemical substances (e.g., saliva, alcohol, bacterial acids) of the oral environment, which may affect the material's structure and surface properties. This study evaluated the effect of acidic substances on the surface properties of a micro-hybrid composite resin (Filtek Z-250). Eighty specimens were prepared, and baseline hardness and surface roughness (KMN0 and Ra0, respectively) were measured. The specimens were subjected to sorption (SO) and solubility (SL) tests according to ISO 4049:2009, but using different storage solutions: deionized water; 75/25 vol% ethanol/water solution; lactic acid; propionic acid; and acetic acid. The acids were used in two concentrations: PA and 0.02 N. pH was measured for all solutions and final hardness (KMN1) and surface roughness (Ra1) were measured. Data were analyzed with paired t-tests and one-way ANOVA and Tukey's test (a=5%). All solutions decreased hardness and increased the Ra values, except for the specimens stored in water and 0.02 N lactic acid, which maintained the hardness. All solutions produced similar SO and SL phenomena, except for the 0.02 N lactic acid, which caused lower solubility than the other solutions. Ethanol showed the highest pH (6.6) and the 0.02 N lactic acid the lowest one (2.5). The solutions affected negatively the surface properties of the composite resin; in addition, an acidic pH did not seem to be a significant factor that intensifies the surface degradation phenomena.

  8. Potential effects of rainwater-borne H2O2 on competitive degradation of herbicides and in the presence of humic acid.

    PubMed

    Qin, Junhao; Li, Yongjun; Li, Shengan; Li, Huashou; Lin, Chuxia

    2017-03-01

    In a previous piece of work, we reported some preliminary experimental results showing that hydrogen peroxide at a concentration range frequently encountered in rainwater could lead to degradation of three common herbicides (diuron, butachlor and glyphosate). However, the work was limited to the observation on the effects of Fenton process on the individual herbicides. In field conditions, different types of herbicides along with other organic molecules may occur concurrently. It is unclear how different herbicides and various organic molecules compete for the available hydroxyl radical. In this study, further laboratory experiments were conducted to observe the changes in the herbicides in the scenarios where multiple herbicides or humic acid are present. The results show that humic acid impeded hydroxyl radical-driven degradation of the diuron and butachlor. However, humic acid had no significant effects on reducing glyphosate removal rate. Glyphosate could compete strongly with the humic acid for the available hydroxyl radical in the reaction systems. The reactivity of glyphosate with hydroxyl radical was much higher than those of diuron and butachlor due possibly to its relatively simpler chemical structure, as compared to either diuron or butachlor, which are aromatic compounds that have higher chemical stability. Butachlor degradation was much weaker in the combined diuron and butachlor system than in the combined glyphosate and butachlor system. In the glyphosate-butachlor system, the opposite was observed. The findings have moved another step forward to understanding the potential role of rainwater-borne H2O2 in degrading herbicides in open water environments.

  9. Acceleration of the herbicide isoproturon degradation in wheat by glycosyltransferases and salicylic acid.

    PubMed

    Lu, Yi Chen; Zhang, Shuang; Yang, Hong

    2015-01-01

    Isoproturon (IPU) is a herbicide widely used to prevent weeds in cereal production. Due to its extensive use in agriculture, residues of IPU are often detected in soils and crops. Overload of IPU to crops is associated with human health risks. Hence, there is an urgent need to develop an approach to mitigate its accumulation in crops. In this study, the IPU residues and its degradation products in wheat were characterized using ultra performance liquid chromatography-time of fight tandem-mass spectrometer/mass spectrometer (UPLC-TOF-MS/MS). Most detected IPU-derivatives were sugar-conjugated. Degradation and glycosylation of IPU-derivatives could be enhanced by applying salicylic acid (SA). While more sugar-conjugated IPU-derivatives were identified in wheat with SA application, lower levels of IPU were detected, indicating that SA is able to accelerate intracellular IPU catabolism. All structures of IPU-derivatives and sugar-conjugated products were characterized. Comparative data were provided with specific activities and gene expression of certain glucosyltransferases. A pathway with IPU degradation and glucosylation was discussed. Our work indicates that SA-accelerated degradation is practically useful for wheat crops growing in IPU-contaminated soils because such crops with SA application can potentially lower or minimize IPU accumulation in levels below the threshold for adverse effects.

  10. Amyloid Plaque-Associated Oxidative Degradation of Uniformly Radiolabeled Arachidonic Acid.

    PubMed

    Furman, Ran; Murray, Ian V J; Schall, Hayley E; Liu, Qiwei; Ghiwot, Yonatan; Axelsen, Paul H

    2016-03-16

    Oxidative stress is a frequently observed feature of Alzheimer's disease, but its pathological significance is not understood. To explore the relationship between oxidative stress and amyloid plaques, uniformly radiolabeled arachidonate was introduced into transgenic mouse models of Alzheimer's disease via intracerebroventricular injection. Uniform labeling with carbon-14 is used here for the first time, and made possible meaningful quantification of arachidonate oxidative degradation products. The injected arachidonate entered a fatty acid pool that was subject to oxidative degradation in both transgenic and wild-type animals. However, the extent of its degradation was markedly greater in the hippocampus of transgenic animals where amyloid plaques were abundant. In human Alzheimer's brain, plaque-associated proteins were post-translationally modified by hydroxynonenal, a well-known oxidative degradation product of arachidonate. These results suggest that several recurring themes in Alzheimer's pathogenesis, amyloid β proteins, transition metal ions, oxidative stress, and apolipoprotein isoforms, may be involved in a common mechanism that has the potential to explain both neuronal loss and fibril formation in this disease.

  11. [Enzymatic formation of a cis,cis-muconic acid derivative using pyrazon-degrading bacteria (author's transl)].

    PubMed

    Blobel, F; Eberspächer, J; Haug, S; Lingens, F

    1976-01-01

    The cis,cis-muconic acid derivative of pyrazon, which was formerly isolated from the medium of pyrazon-degrading bacteria, was formed enzymatically by incubation of the catechol derivative of pyrazon with partially purified ortho pyrocatechase from pyrazon-degrading bacteria.

  12. Effect of Boric Acid on Volatile Products of Thermooxidative Degradation of Epoxy Polymers

    NASA Astrophysics Data System (ADS)

    Nazarenko, O. B.; Bukhareva, P. B.; Melnikova, T. V.; Visakh, P. M.

    2016-01-01

    The polymeric materials are characterized by high flammability. The use of flame retardants in order to reduce the flammability of polymers can lead to the formation of toxic gaseous products under fire conditions. In this work we studied the effect of boric acid on the volatile products of thermooxidative degradation of epoxy polymers. The comparative investigations were carried out on the samples of the unfilled epoxy resin and epoxy resin filled with a boric acid at percentage 10 wt. %. The analysis of the volatile decomposition products and thermal stability of the samples under heating in an oxidizing medium was performed using a thermal mass-spectrometric analysis. It is found that the incorporation of boric acid into the polymer matrix increases the thermal stability of epoxy composites and leads to a reduction in the 2-2.7 times of toxic gaseous products

  13. Influence of phytic acid and its metal complexes on the activity of pectin degrading polygalacturonase.

    PubMed

    Asghar, Uzma; Rehman, Haneef Ur; Qader, Shah Ali Ul; Maqsood, Zahida Tasneem

    2013-06-05

    Polygalacturonase is one of the important requirements of different microorganism to cause pathogenicity and spoilage of fruits and vegetables that involved in degradation of pectin during plant tissue infections. In current study, 20 mM phytic acid inhibited 70% activity of polygalacturonase. The effect of different concentration of metal ions such as Cu(+2), Al(+3) and V(+4) were studied separately and it was found that the 20 mM of these metal ions inhibited 37.2%, 79%, and 53% activity of polygalacturonase, respectively. Finally, the complexes of phytic acid and these metals ions were prepared and 1:1 ratio of phytic acid and metal ions complexes showed maximum inhibitory activity of enzyme as compared to complexes having 1:2 and 1:3 ratio except phytate-copper complexes which showed no inhibitory effect on the activity of polygalacturonase.

  14. Reduction Rates for Higher Americium Oxidation States in Nitric Acid

    SciTech Connect

    Grimes, Travis Shane; Mincher, Bruce Jay; Schmitt, Nicholas C

    2015-09-30

    The stability of hexavalent americium was measured using multiple americium concentrations and nitric acid concentrations after contact with the strong oxidant sodium bismuthate. Contrary to our hypotheses Am(VI) was not reduced faster at higher americium concentrations, and the reduction was only zero-order at short time scales. Attempts to model the reduction kinetics using zero order kinetic models showed Am(VI) reduction in nitric acid is more complex than the autoreduction processes reported by others in perchloric acid. The classical zero-order reduction of Am(VI) was found here only for short times on the order of a few hours. We did show that the rate of Am(V) production was less than the rate of Am(VI) reduction, indicating that some Am(VI) undergoes two electron-reduction to Am(IV). We also monitored the Am(VI) reduction in contact with the organic diluent dodecane. A direct comparison of these results with those in the absence of the organic diluent showed the reduction rates for Am(VI) were not statistically different for both systems. Additional americium oxidations conducted in the presence of Ce(IV)/Ce(III) ions showed that Am(VI) is reduced without the typical growth of Am(V) observed in the systems sans Ce ion. This was an interesting result which suggests a potential new reduction/oxidation pathway for Am in the presence of Ce; however, these results were very preliminary, and will require additional experiments to understand the mechanism by which this occurs. Overall, these studies have shown that hexavalent americium is fundamentally stable enough in nitric acid to run a separations process. However, the complicated nature of the reduction pathways based on the system components is far from being rigorously understood.

  15. On the probability of exceeding allowable leak rates through degraded steam generator tubes

    SciTech Connect

    Cizelj, L.; Sorsek, I.; Riesch-Oppermann, H.

    1997-02-01

    This paper discusses some possible ways of predicting the behavior of the total leak rate through the damaged steam generator tubes. This failure mode is of special concern in cases where most through-wall defects may remain In operation. A particular example is the application of alternate (bobbin coil voltage) plugging criterion to Outside Diameter Stress Corrosion Cracking at the tube support plate intersections. It is the authors aim to discuss some possible modeling options that could be applied to solve the problem formulated as: Estimate the probability that the sum of all individual leak rates through degraded tubes exceeds the predefined acceptable value. The probabilistic approach is of course aiming at reliable and computationaly bearable estimate of the failure probability. A closed form solution is given for a special case of exponentially distributed individual leak rates. Also, some possibilities for the use of computationaly efficient First and Second Order Reliability Methods (FORM and SORM) are discussed. The first numerical example compares the results of approximate methods with closed form results. SORM in particular shows acceptable agreement. The second numerical example considers a realistic case of NPP in Krsko, Slovenia.

  16. Formic acid enhanced effective degradation of methyl orange dye in aqueous solutions under UV-Vis irradiation.

    PubMed

    Wang, Jingjing; Bai, Renbi

    2016-09-15

    Developing efficient technologies to treat recalcitrant organic dye wastewater has long been of great research and practical interest. In this study, a small molecule, formic acid (FA), was applied as a process enhancer for the degradation of methyl orange (MO) dye as a model recalcitrant organic pollutant in aqueous solutions under the condition of UV-Vis light irradiation and air aeration at the ambient temperature of 25 °C. It was found that the decolouration of the dye solutions can be rapidly achieved, reducing the time, for example, from around 17.6 h without FA to mostly about less than 2 h with the presence of FA. The mineralization rate of MO dye reached as high as 81.8% in 1.5 h in the case of initial MO dye concentration at 25 mg L(-1), which is in contrast to nearly no mineralization of the MO dye for a similar system without the FA added. The study revealed that the generation of the H2O2 species in the system was enhanced and the produced OH radicals effectively contributed to the degradation of the MO dye. Process parameters such as the initial concentration of MO dye, FA dosage and solution pH were all found to have some effect on the degradation efficiency under the same condition of UV-Vis light irradiation and air aeration. The MO dye degradation performance was found to follow a first-order reaction rate to the MO dye concentration in most cases and there existed a positive correlation between the reaction rate constant and the initial FA concentration. Compared to the traditional H2O2/UV-Vis oxidation system, the use of FA as a process-enhancing agent can have the advantages of low cost, easy availability, and safe to use. The study hence demonstrates a promising approach to use a readily available small molecule of FA to enhance the degradation of recalcitrant organic pollutants, such as MO dye, especially for their pre-treatment.

  17. Isolation and characterization of haloacetic acid-degrading Afipia spp. from drinking water.

    PubMed

    Zhang, Ping; Hozalski, Raymond M; Leach, Lynne H; Camper, Anne K; Goslan, Emma H; Parsons, Simon A; Xie, Yuefeng F; LaPara, Timothy M

    2009-08-01

    Haloacetic acids are a class of disinfection byproducts formed during the chlorination and chloramination of drinking water that have been linked to several human health risks. In this study, we isolated numerous strains of haloacetic acid-degrading Afipia spp. from tap water, the wall of a water distribution pipe, and a granular activated carbon filter treating prechlorinated water. These Afipia spp. harbored two phylogenetically distinct groups of alpha-halocarboxylic acid dehalogenase genes that clustered with genes previously detected only by cultivation-independent methods or were novel and did not conclusively cluster with the previously defined phylogenetic subdivisions of these genes. Four of these Afipia spp. simultaneously harbored both the known classes of alpha-halocarboxylic acid dehalogenase genes (dehI and dehII), which is potentially of importance because these bacteria were also capable of biodegrading the greatest number of different haloacetic acids. Our results suggest that Afipia spp. have a beneficial role in suppressing the concentrations of haloacetic acids in tap water, which contrasts the historical (albeit erroneous) association of Afipia sp. (specifically Afipia felis) as the causative agent of cat scratch disease.

  18. Application of microchip-CE electrophoresis to follow the degradation of phenolic acids by aquatic plants.

    PubMed

    Ding, Yongsheng; Garcia, Carlos D

    2006-12-01

    In this paper, we describe the separation and detection of six phenolic acids using an electrophoretic microchip with pulsed amperometric detection (PAD). The selected phenolic acids are particularly important because of their biological activity. The analysis of these compounds is typically performed by chromatography or standard CE coupled with a wide variety of detection modes. However, these methods are slow, labor intensive, involve a multistep solvent extraction, require skilled personnel, or use bulky and expensive instrumentation. In contrast, microchip CE offers the possibility of performing simpler, less expensive, and faster analysis. In addition, integrated devices can be custom-fabricated and incorporated with portable computers to perform on-site analysis. In the present report, the effect of the separation potential, buffer pH and composition, injection time and PAD parameters were studied in an effort to optimize both the separation and detection of these phenolic acids. Using the optimized conditions, the analysis can be performed in less than 3 min, with detection limits ranging from 0.73 microM (0.10 microg/mL) for 4-hydroxyphenylacetic acid to 2.12 microM (0.29 microg/mL) for salicylic acid. In order to demonstrate the capabilities of the device, the degradation of a mixture of these acids by two aquatic plants was followed using the optimized conditions.

  19. Anaerobic Degradation of Cyanuric Acid, Cysteine, and Atrazine by a Facultative Anaerobic Bacterium

    PubMed Central

    Jessee, J. A.; Benoit, R. E.; Hendricks, A. C.; Allen, G. C.; Neal, J. L.

    1983-01-01

    A facultative anaerobic bacterium that rapidly degrades cyanuric acid (CA) was isolated from the sediment of a stream that received industrial wastewater effluent. CA decomposition was measured throughout the growth cycle by using a high-performance liquid chromatography assay, and the concomitant production of ammonia was also measured. The bacterium used CA or cysteine as a major, if not the sole, carbon and energy source under anaerobic, but not aerobic, conditions in a defined medium. The cell yield was greatly enhanced by the simultaneous presence of cysteine and CA in the medium. Cysteine was preferentially used rather than CA early in the growth cycle, but all of the CA was used without an apparent lag after the cysteine was metabolized. Atrazine was also degraded by this bacterium under anaerobic conditions in a defined medium. PMID:16346187

  20. Laboratory photochemical processing of aqueous aerosols: formation and degradation of dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls

    NASA Astrophysics Data System (ADS)

    Pavuluri, C. M.; Kawamura, K.; Mihalopoulos, N.; Swaminathan, T.

    2015-01-01

    To better understand the photochemical processing of dicarboxylic acids and related polar compounds, we conducted batch UV irradiation experiments on two types of aerosol samples collected from India, which represent anthropogenic (AA) and biogenic aerosols (BA), for time periods of 0.5 to 120 h. The irradiated samples were analyzed for molecular compositions of diacids, oxoacids and α-dicarbonyls. The results show that photochemical degradation of oxalic (C2) and malonic (C3) and other C8-C12 diacids overwhelmed their production in aqueous aerosols whereas succinic acid (C4) and C5-C7 diacids showed a significant increase (ca. 10 times) during the course of irradiation experiments. The photochemical formation of oxoacids and α-dicarbonyls overwhelmed their degradation during the early stages of experiment, except for ω-oxooctanoic acid (ωC8) that showed a similar pattern to that of C4. We also found a gradual decrease in the relative abundance of C2 to total diacids and an increase in the relative abundance of C4 during prolonged experiment. Based on the changes in concentrations and mass ratios of selected species with the irradiation time, we hypothesize that iron-catalyzed photolysis of C2 and C3 diacids dominates their concentrations in Fe-rich atmospheric waters, whereas photochemical formation of C4 diacid (via ωC8) is enhanced with photochemical processing of aqueous aerosols in the atmosphere. This study demonstrates that the ambient aerosols contain abundant precursors that produce diacids, oxoacids and α-dicarbonyls, although some species such as oxalic acid decompose extensively during an early stage of photochemical processing.

  1. Laboratory photochemical processing of aqueous aerosols: formation and degradation of dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls

    NASA Astrophysics Data System (ADS)

    Pavuluri, C. M.; Kawamura, K.; Mihalopoulos, N.; Swaminathan, T.

    2015-07-01

    To better understand the photochemical processing of dicarboxylic acids and related polar compounds, we conducted batch UV irradiation experiments on two types of aerosol samples collected from India, which represent anthropogenic (AA) and biogenic (BA) aerosols, for time periods of 0.5 to 120 h. The irradiated samples were analyzed for molecular compositions of diacids, oxoacids and α-dicarbonyls. The results show that photochemical degradation of oxalic (C2), malonic (C3) and other C8-C12 diacids overwhelmed their production in aqueous aerosols, whereas succinic acid (C4) and C5-C7 diacids showed a significant increase (ca. 10 times) during the course of irradiation experiments. The photochemical formation of oxoacids and α-dicarbonyls overwhelmed their degradation during the early stages of experiment except for ω-oxooctanoic acid (ωC8), which showed a similar pattern to that of C4. We also found a gradual decrease in the relative abundance of C2 to total diacids and an increase in the relative abundance of C4 during prolonged experiment. Based on the changes in concentrations and mass ratios of selected species with the irradiation time, we hypothesize that iron-catalyzed photolysis of C2 and C3 diacids controls their concentrations in Fe-rich atmospheric waters, whereas photochemical formation of C4 diacid (via ωC8) is enhanced with photochemical processing of aqueous aerosols in the atmosphere. This study demonstrates that the ambient aerosols contain abundant precursors that produce diacids, oxoacids and α-dicarbonyls, although some species such as oxalic acid decompose extensively during an early stage of photochemical processing.

  2. Pseudomonas aeruginosa Directly Shunts β-Oxidation Degradation Intermediates into De Novo Fatty Acid Biosynthesis

    PubMed Central

    Yuan, Yanqiu; Leeds, Jennifer A.

    2012-01-01

    We identified the fatty acid synthesis (FAS) initiation enzyme in Pseudomonas aeruginosa as FabY, a β-ketoacyl synthase KASI/II domain-containing enzyme that condenses acetyl coenzyme A (acetyl-CoA) with malonyl-acyl carrier protein (ACP) to make the FAS primer β-acetoacetyl-ACP in the accompanying article (Y. Yuan, M. Sachdeva, J. A. Leeds, and T. C. Meredith, J. Bacteriol. 194:5171-5184, 2012). Herein, we show that growth defects stemming from deletion of fabY can be suppressed by supplementation of the growth media with exogenous decanoate fatty acid, suggesting a compensatory mechanism. Fatty acids eight carbons or longer rescue growth by generating acyl coenzyme A (acyl-CoA) thioester β-oxidation degradation intermediates that are shunted into FAS downstream of FabY. Using a set of perdeuterated fatty acid feeding experiments, we show that the open reading frame PA3286 in P. aeruginosa PAO1 intercepts C8-CoA by condensation with malonyl-ACP to make the FAS intermediate β-keto decanoyl-ACP. This key intermediate can then be extended to supply all of the cellular fatty acid needs, including both unsaturated and saturated fatty acids, along with the 3-hydroxyl fatty acid acyl groups of lipopolysaccharide. Heterologous PA3286 expression in Escherichia coli likewise established the fatty acid shunt, and characterization of recombinant β-keto acyl synthase enzyme activity confirmed in vitro substrate specificity for medium-chain-length acyl CoA thioester acceptors. The potential for the PA3286 shunt in P. aeruginosa to curtail the efficacy of inhibitors targeting FabY, an enzyme required for FAS initiation in the absence of exogenous fatty acids, is discussed. PMID:22753057

  3. Optimization of acidic fibroblast growth factor (FGF-1) and its delivery through a modified degradable fibrin scaffold

    NASA Astrophysics Data System (ADS)

    Pandit, Abhay Smashikant

    The aim of this investigation was to develop a degradable fibrin wound dressing that can deliver an optimized dose of acidic fibroblast growth factor (FGF-1). This aim led to three distinct phases of study. In the first phase, a structurally modified fibrin degradable scaffold was developed and tested in a rabbit ear ulcer model. A significant increase in the angiogenic and fibroblastic response with a corresponding decrease in healing time was seen in the modified fibrin-treated ulcers as compared with untreated ulcers and ulcers treated with non-modified fibrin systems. In the second phase of the study, a biochemical factor, FGF-1, was added to this scaffold. An optimal dose of 8 mug of FGF-1 was determined to be required to initiate a desired wound-healing response in a rabbit ear ulcer model, based on an enhanced angiogenic and fibroblastic response and an increased epithelialization rate. The objective of the last phase was to investigate the efficacy of a modified scaffold as a vehicle for FGF-1. In vivo testing was conducted in a full-thickness defect model in a rabbit. Improvements were seen in the angiogenic and fibroblastic responses in the FGF-1/modified fibrin treatment group and, hence, FGF-1/modified fibrin was the preferred treatment. In conclusion, the modified fibrin/FGF-1 matrix served as a suitable vehicle for the growth factor, providing a desired healing response and a desirable release rate and, thus, was determined to be an effective scaffold.

  4. Impact of trace element addition on degradation efficiency of volatile fatty acids, oleic acid and phenyl acetate and on microbial populations in a biogas digester.

    PubMed

    Karlsson, Anna; Einarsson, Peter; Schnürer, Anna; Sundberg, Carina; Ejlertsson, Jörgen; Svensson, Bo H

    2012-10-01

    The effect of trace element addition on anaerobic digestion of food industry- and household waste was studied using two semi-continuous lab-scale reactors, one (R30+) was supplied with Fe, Co and Ni, while the other (R30) acted as a control. Tracer analysis illustrated that methane production from acetate proceeded through syntrophic acetate oxidation (SAO) in both digesters. The effect of the trace elements was also evaluated in batch assays to determine the capacity of the microorganisms of the two digesters to degrade acetate, phenyl acetate, oleic acid or propionate, butyrate and valerate provided as a cocktail. The trace elements addition improved the performance of the process giving higher methane yields during start-up and early operation and lower levels of mainly acetate and propionate in the R30+ reactor. The batch assay showed that material from R30+ gave effects on methane production from all substrates tested. Phenyl acetate was observed to inhibit methane formation in the R30 but not in the R30+ assay. A real-time PCR analysis targeting methanogens on the order level as well as three SAO bacteria showed an increase in Methanosarcinales in the R30+ reactor over time, even though SAO continuously was the dominating pathway for methane production. Possibly, this increase explains the low VFA-levels and higher degradation rates observed in the R30+ batch incubations. These results show that the added trace elements affected the ability of the microflora to degrade VFAs as well as oleic acid and phenyl acetate in a community, where acetate utilization is dominated by SAO.

  5. Growth suppression by ursodeoxycholic acid involves caveolin-1 enhanced degradation of EGFR

    PubMed Central

    Feldman, Rebecca; Martinez, Jesse D.

    2009-01-01

    Summary Ursodeoxycholic acid (UDCA) has been shown to prevent colon tumorigenesis in animal models and in humans. In vitro work indicates that this bile acid can suppress cell growth and mitogenic signaling suggesting that UDCA may be an anti-proliferative agent. However, the mechanism by which UDCA functions is unclear. Previously we showed that bile acids may alter cellular signaling by acting at the plasma membrane. Here we utilized EGFR as a model membrane receptor and examined the effects that UDCA has on its functioning. We found that UDCA promoted an interaction between EGFR and caveolin-1 and this interaction enhanced UDCA-mediated suppression of MAP kinase activity and cell growth . Importantly, UDCA treatment led to recruitment of the ubiquitin ligase, c-Cbl, to the membrane, ubiquitination of EGFR, and increased receptor degradation. Moreover, suppression of c-Cbl activity abrogated UDCA's growth suppression activities suggesting that receptor ubiquitination plays an important role in UDCA's biological activities. Taken together these results suggest that UDCA may act to suppress cell growth by inhibiting the mitogenic activity of receptor tyrosine kinases such as EGFR through increased receptor degradation. PMID:19446582

  6. Effects of common inorganic anions on the rates of photocatalytic degradation of sodium dodecylbenzenesulfonate over illuminated titanium dioxide.

    PubMed

    Xia, Xing-hui; Xu, Jia-lin; Yun, Ying

    2002-04-01

    Experiments were carried out to study the effects of several anions on the photocatalytic degradation rates of sodium dodecylbenzene sulphonate (DBS) with TiO2 as catalyst. The anions were added as Na2SO4, NaNO3, NaCl, NaHCO3, NaH2PO4 and Na3PO4, and two levels of anion content, i.e. 12 mmol/L and 36 mmol/L in terms of Na+, were studied. The results revealed that: Cl-, SO4(2-), NO3- and HCO3- retarded the rates of DBS degradation to different degrees; PO4(3-) increased the DBS degradation rate at low concentration and decreased the rate at high concentration; H2PO4- accelerated the rate of DBS degradation. The mechanism of the effects of anions on DBS degradation was concluded as the following three aspects: anions compete for the radicals; anions are absorbed on the surface of catalyst and block the active site of catalyst; anions added to the solution change the pH value and influence the formation of .OH radicals and the adsorption of DBS on catalyst.

  7. Oxidative degradation of acid orange 7 using Ag-doped zinc oxide thin films.

    PubMed

    Shinde, S S; Bhosale, C H; Rajpure, K Y

    2012-12-05

    Ag-doped ZnO thin films with preferred c-axis orientation along (002) have been prepared by spray pyrolysis technique in aqueous medium on to the corning glass substrates. The effect of Ag-doping on to the photoelectrochemical, structural, morphological, optical, luminescence, electrical and thermal properties has been investigated. XRD and Raman study indicates that the films have hexagonal (wurtzite) crystal structure. The effect of Ag loading on the photocatalytic activity of Ag-doped ZnO in the degradation of azo dye is studied and results are compared with pure ZnO. The results show that the rate of degradation of azo dye over Ag-doped ZnO is much higher as compared to pure ZnO. Ag doping in ZnO is highly effective and can significantly enhance the photocatalytic degradation and mineralization of azo dye. The enhancement of photocatalytic activity of Ag-doped ZnO thin films is mainly due to their smaller crystallite size and capability for reducing the electron-hole pair recombination. Kinetic parameters have been investigated in terms of a first order rate equation. The rate constant (-k) for this heterogeneous photocatalysis is evaluated as a function of the initial concentration of original species. Substantial reduction in azo dye is achieved as analyzed from COD and TOC studies.

  8. TiO2 photocatalysis of naproxen: effect of the water matrix, anions and diclofenac on degradation rates.

    PubMed

    Kanakaraju, Devagi; Motti, Cherie A; Glass, Beverley D; Oelgemöller, Michael

    2015-11-01

    The TiO2 photocatalytic degradation of the active pharmaceutical ingredient (API) naproxen (NPX) has been studied using a laboratory-scale photoreactor equipped with a medium pressure mercury lamp. UV/TiO2 photocatalysis proved highly efficient in the elimination of NPX from a variety of water matrices, including distilled water, unfiltered river water and drinking water, although the rate of reaction was not always proportional to TiO2 concentration. However, the NPX degradation rate, which follows first-order kinetics, was appreciably reduced in river water spiked with phosphate and chloride ions, a dual anion system. Addition of chloride into drinking water enhanced the TiO2-photocatalysed degradation rate. Competitive degradation studies also revealed that the NPX degradation was greatly reduced in the presence of increased concentrations of another API, diclofenac (DCF). This was established by (i) the extent of mineralization, as determined by dissolved organic carbon (DOC) content, and (ii) the formation of intermediate NPX by-products, identified using liquid chromatography and electrospray ionization (positive and negative mode) mass spectrometry techniques. This study demonstrates that competition for active sites (anions or DCF) and formation of multiple photoproducts resulting from synergistic interactions (between both APIs) are key to the TiO2-photocatalysed NPX degradation.

  9. Determination of the thermal, oxidative and photochemical degradation rates of scintillator liquid by fluorescence EEM spectroscopy.

    PubMed

    Andrews, N L P; Fan, J Z; Forward, R L; Chen, M C; Loock, H-P

    2016-12-21

    The thermal, oxidative and photochemical stability of the scintillator liquid proposed for the SNO+ experiment has been tested experimentally using accelerated aging methods. The stability of the scintillator constituents was determined through fluorescence excitation emission matrix (EEM) spectroscopy and absorption spectroscopy, using parallel factor analysis (PARAFAC) as an multivariate analysis tool. By exposing the scintillator liquid to a well-known photon flux at 365 nm and by measuring the decay rate of the fluorescence shifters and the formation rate of their photochemical degradation products, we can place an upper limit on the acceptable photon flux as 1.38 ± 0.09 × 10(-11) photon mol L(-1). Similarly, the oxidative stability of the scintillator liquid was determined by exposure to air at several elevated temperatures. Through measurement of the corresponding activation energy it was determined that the average oxygen concentration would have to be kept below 4.3-7.1 ppbw (headspace partial pressure below 24 ppmv). On the other hand, the thermal stability of the scintillator cocktail in the absence of light and oxygen was remarkable and poses no concern to the SNO+ experiment.

  10. Green stabilization of microscale iron particles using guar gum: bulk rheology, sedimentation rate and enzymatic degradation.

    PubMed

    Gastone, Francesca; Tosco, Tiziana; Sethi, Rajandrea

    2014-05-01

    Guar gum can be used to effectively improve stability and mobility of microscale zerovalent iron particles (MZVI) used in groundwater remediation. Guar gum is a food-grade, environment friendly natural polysaccharide, which is often used as thickening agent in a broad range of food, pharmaceutical and industrial applications. Guar gum solutions are non-Newtonian, shear thinning fluids, characterized by high viscosity in static conditions and low viscosity in dynamic conditions. In particular, the high zero shear viscosity guarantees the MZVI dispersion stability, reducing the sedimentation rate of the particles thus enabling its storage and field operations. In this work, a comprehensive rheological characterization of guar gum-based slurries of MZVI particles is provided. First, we derived a model to link the bulk shear viscosity to the concentration of guar gum and then we applied it for the derivation of a modified Stokes law for the prediction of the sedimentation rate of the iron particles. The influence of the preparation procedure (cold or hot dissolution and high shear processing) on the viscosity and on the stability of the suspensions was then assessed. Finally, the dosage and concentration of enzymes - an environment friendly breaker--were studied for enhancing and controlling the degradation kinetics of the suspensions. The derived empirical relationships can be used for the implementation of an iron slurry flow and transport model and for the design of full scale injection interventions.

  11. Attenuation of kainic acid-induced status epilepticus by inhibition of endocannabinoid transport and degradation in guinea pigs.

    PubMed

    Shubina, Liubov; Aliev, Rubin; Kitchigina, Valentina

    2015-03-01

    Status epilepticus (SE) is a medical emergency associated with a high rate of mortality if not treated promptly. Exogenous and endogenous cannabinoids have been shown to possess anticonvulsant properties both in vivo and in vitro. Here we study the influence of endocannabinoid metabolism on the development of kainic acid-induced SE in guinea pigs. For this purpose, the inhibitors of endocannabinoid transport, AM404, and enzymatic (fatty acid amide hydrolase) degradation, URB597, were applied. Cannabinoid CB1 receptor antagonist, AM251, was also tested. Animal behavior as well as local electric field potentials in four structures: medial septum, hippocampus, entorhinal cortex and amygdala were analyzed when AM404 (120nmol), URB597 (4.8nmol) or AM251 (20nmol) were administrated alone or together with 0.4μg of kainic acid. All substances were injected i.c.v. AM404, URB597 or AM251 administered alone did not alter markedly local field potentials of all four studied structures in the long-term compared with their basal activity. AM404 and URB597 significantly alleviated kainic acid-induced SE, decreasing behavioral manifestations, duration of seizure events and SE in general without changing the amplitude of local field potentials. AM251 did not produce distinct effects on SE in terms of our experimental paradigm. There was no apparent change of the seizure initiation pattern when kainic acid was coadministrated with AM404, URB597 or AM251. The present study provides electrophysiologic and behavioral evidences that inhibition of endocannabinoid metabolism plays a protective role against kainic acid-induced SE and may be employed for therapeutic purposes. Further investigations of the influences of cannabinoid-related compounds on SE genesis and especially epileptogenesis are required.

  12. Polycyclic aromatic hydrocarbon reaction rates with peroxy-acid treatment: prediction of reactivity using local ionization potential.

    PubMed

    Shoulder, J M; Alderman, N S; Breneman, C M; Nyman, M C

    2013-08-01

    Property-Encoded Surface Translator (PEST) descriptors were found to be correlated with the degradation rates of polycyclic aromatic hydrocarbons (PAHs) by the peroxy-acid process. Reaction rate constants (k) in hr(-1) for nine PAHs (acenaphthene, anthracene, benzo[a]pyrene, benzo[k]fluoranthene, fluoranthene, fluorene, naphthalene, phenanthrene, and pyrene) were determined by a peroxy-acid treatment method that utilized acetic acid, hydrogen peroxide, and a sulphuric acid catalyst to degrade the polyaromatic structures. Molecular properties of the selected nine PAHs were derived from structures optimized at B3LYP/6-31G(d) and HF/6-31G(d) levels of theory. Properties of adiabatic and vertical ionization potential (IP), highest occupied molecular orbitals (HOMO), HOMO/lowest unoccupied molecular orbital (LUMO) gap energies and HOMO/singly occupied molecular orbital (SOMO) gap energies were not correlated with rates of peroxy-acid reaction. PEST descriptors were calculated from B3LYP/6-31G(d) optimized structures and found to have significant levels of correlation with k. PIP Min described the minimum local IP on the surface of the molecule and was found to be related to k. PEST technology appears to be an accurate method in predicting reactivity and could prove to be a valuable asset in building treatment models and in remediation design for PAHs and other organic contaminants in the environment.

  13. Flow injection analysis of organic peroxide explosives using acid degradation and chemiluminescent detection of released hydrogen peroxide.

    PubMed

    Mahbub, Parvez; Zakaria, Philip; Guijt, Rosanne; Macka, Mirek; Dicinoski, Greg; Breadmore, Michael; Nesterenko, Pavel N

    2015-10-01

    The applicability of acid degradation of organic peroxides into hydrogen peroxide in a pneumatically driven flow injection system with chemiluminescence reaction with luminol and Cu(2+) as a catalyst (FIA-CL) was investigated for the fast and sensitive detection of organic peroxide explosives (OPEs). The target OPEs included hexamethylene triperoxide diamine (HMTD), triacetone triperoxide (TATP) and methylethyl ketone peroxide (MEKP). Under optimised conditions maximum degradations of 70% and 54% for TATP and HMTD, respectively were achieved at 162 µL min(-1), and 9% degradation for MEKP at 180 µL min(-1). Flow rates were precisely controlled in this single source pneumatic pressure driven multi-channel FIA system by model experiments on mixing of easily detectable component solutions. The linear range for detection of TATP, HMTD and H2O2 was 1-200 µM (r(2)=0.98-0.99) at both flow rates, while that for MEKP was 20-200 µM (r(2)=0.97) at 180 µL min(-1). The detection limits (LODs) obtained were 0.5 µM for TATP, HMTD and H2O2 and 10 µM for MEKP. The detection times varied from 1.5 to 3 min in this FIA-CL system. Whilst the LOD for H2O2 was comparable with those reported by other investigators, the LODs and analysis times for TATP and HMTD were superior, and significantly, this is the first time the detection of MEKP has been reported by FIA-CL.

  14. Composition, assimilation and degradation of Phaeocystis globosa-derived fatty acids in the North Sea

    NASA Astrophysics Data System (ADS)

    Hamm, Christian E.; Rousseau, Veronique

    2003-12-01

    The fate of a Phaeocystis globosa bloom in the southern North Sea off Belgium, the Netherlands and Germany in May 1995 was investigated during a cruise with RV 'Belgica'. We used fatty acids as biomarkers to follow the fate of Phaeocystis-derived biomass of a Phaeocystis-dominated spring bloom. The bloom, in which up to >99% of the biomass was contributed by Phaeocystis, showed a fatty acid composition with a characteristically high abundance of polyunsaturated C 18-fatty acids, which increased in concentration with number of double bonds up to 18:5 (n-3), and high concentrations of 20:5 (n-3) and 22:6 (n-3). In contrast to most previous studies, fatty acid analysis of the mesozooplankton community (mainly calanoid copepods) and meroplankton ( Carcinus maenas megalope) indicated that P. globosa was a major component (ca. 70% and 50%, respectively) in the diet of these organisms. Massive accumulations of amorphous grey aggregates, in which Phaeocystis colonies were major components, were dominated by saturated fatty acids and contained only few of the polyunsaturated C 18-fatty acids. A hydrophobic surface slick that covered the water surface during the bloom showed very similar patterns. Foam patches contained few Phaeocystis-typical fatty acids, but increased amounts of diatom-typical compounds such as 16:1 (n-7) and 20:5 (n-3), and 38% fatty alcohols, indicating that wax esters dominated the lipid fraction in the foam with ca. 76% (w/w). The fatty acid compositions of surface sediment showed that no sedimentation of fresh Phaeocystis occurred during the study. The results indicate that Phaeocystis-derived organic matter degraded while floating or in suspension, and had not reached the sediment in substantial amounts.

  15. Microbiological degradation of organic components in oil shale retort water: organic acids.

    PubMed

    Rogers, J E; Riley, R G; Li, S W; Mann, D C; Wildung, R E

    1981-11-01

    The losses of benzoic acid and a homologous series of both mono- and dibasic aliphatic acids in oil shale retort water were monitored with time (21 days) in liquid culture (4% retort water, vol/vol) inoculated with soil. The organic acids constituted approximately 12% of the dissolved organic carbon in retort water, which served as the sole source of carbon and energy in these studies. The levels of the acids in solution were reduced by 80 to 90% within 9 days of incubation. From mass balance calculations, the decrease in dissolved organic carbon with time of incubation was equal to the formation of CO(2) and bacterial cell carbon. The decrease in the level of the acid components, either from degradation to CO(2) or incorporation into bacteria, would account for approximately 70% of the loss in dissolved organic carbon within the first 9 days of incubation and would account for approximately 50% of the loss over the entire 21-day incubation period.

  16. Role of degradation products of chlorogenic acid in the antioxidant activity of roasted coffee.

    PubMed

    Kamiyama, Masumi; Moon, Joon-Kwan; Jang, Hae Won; Shibamoto, Takayuki

    2015-02-25

    Antioxidant activities of brewed coffees prepared from six commercial brands ranged from 63.13 ± 1.01 to 96.80 ± 1.68% at the highest levels tested. Generally, the degree of antioxidant activity of the brewed coffee was inversely proportional to the total chlorogenic acid concentration. A sample obtained from the major chlorogenic acid, 5-caffeoylquinic acid (5-CQA), heated at 250 °C exhibited potent antioxidant activity (79.12 ± 2.49%) at the level of 10 μg/mL, whereas unheated 5-CQA showed only moderate antioxidant activity (44.41 ± 0.27%) at the level of 100 μg/mL. Heat produced relatively high levels of pyrocatechol (2,809.3 μg/g) and 2-methoxy-4-vinylphenol (46.4 μg/g) from 5-CQA, and their antioxidant activity levels were 76.57 ± 3.00 and 98.63 ± 0.01%, respectively. The results of the present study suggest that roasting degrades chlorogenic acids to form potent antioxidants and thus plays an important role in the preparation of high-antioxidant low-acid coffee.

  17. The adsorption and photo-degradation of oxalic acid at the TiO2 surface.

    NASA Astrophysics Data System (ADS)

    Mendive, Cecilia; Blesa, Miguel; Bahnemann, Detlef

    2006-03-01

    Oxalic acid is the simplest model compound to study the heterogeneous photocatalytic oxidation of pollutants on TiO2 containing more than one carboxylate group. We have carried out a study of a system of an oxalic acid solution in contact with a thin film of TiO2 particles employing ATR - FTIR in combination with quantum chemical calculations. Thus, possible adsorption structures have been identified and molecular dynamic simulations have been used to compare their predictions with the experimental data. It was found that the adsorption of oxalic acid on TiO2 in the dark can be explained in terms of two surface complexation modes for the anatase phase and only one surface complexation mode for the rutile phase. We have found that under illumination one of the complexes on the anatase phase preferably undergoes photo-degradation. At the same time water molecules are desorbed from the TiO2 surface by a thermal mechanism induced by the absorption of photons. Both processes favor the adsorption of more molecules of oxalic acid at the TiO2 surface which is thus enriched in the second complexation mode. A similar mechanism was found to occur on the rutile phase. The only complexation mode appears not to be photo-sensitive but the TiO2 surface is enriched in oxalic acid under illumination due to the replacement of photo-desorbed water molecules.

  18. Electrochemical degradation of trichloroacetic acid in aqueous media: influence of the electrode material.

    PubMed

    Esclapez, M D; Díez-García, M I; Sàez, V; Bonete, P; González-García, José

    2013-01-01

    The electrochemical degradation of trichloroacetic acid (TCAA) in water has been analysed through voltammetric studies with a rotating disc electrode and controlled-potential bulk electrolyses. The influence of the mass-transport conditions and initial concentration of TCAA for titanium, stainless steel and carbon electrodes has been studied. It is shown that the electrochemical reduction of TCAA takes place prior to the massive hydrogen evolution in the potential window for all electrode materials studied. The current efficiency is high (> 18%) compared with those normally reported in the literature, and the fractional conversion is above 50% for all the electrodes studied. Only dichloroacetic acid (DCAA) and chloride anions were routinely detected as reduction products for any of the electrodes, and reasonable values of mass balance error were obtained. Of the three materials studied, the titanium cathode gave the best results.

  19. Kinetic modeling of the photocatalytic degradation of clofibric acid in a slurry reactor.

    PubMed

    Manassero, Agustina; Satuf, María Lucila; Alfano, Orlando Mario

    2015-01-01

    A kinetic study of the photocatalytic degradation of the pharmaceutical clofibric acid is presented. Experiments were carried out under UV radiation employing titanium dioxide in water suspension. The main reaction intermediates were identified and quantified. Intrinsic expressions to represent the kinetics of clofibric acid and the main intermediates were derived. The modeling of the radiation field in the reactor was carried out by Monte Carlo simulation. Experimental runs were performed by varying the catalyst concentration and the incident radiation. Kinetic parameters were estimated from the experiments by applying a non-linear regression procedure. Good agreement was obtained between model predictions and experimental data, with an error of 5.9 % in the estimations of the primary pollutant concentration.

  20. Preparation, cell compatibility and degradability of collagen-modified poly(lactic acid).

    PubMed

    Cui, Miaomiao; Liu, Leili; Guo, Ning; Su, Ruixia; Ma, Feng

    2015-01-05

    Poly(lactic acid) (PLA) was modified using collagen through a grafting method to improve its biocompatibility and degradability. The carboxylic group at the open end of PLA was transferred into the reactive acylchlorided group by a reaction with phosphorus pentachloride. Then, collagen-modified PLA (collagen-PLA) was prepared by the reaction between the reactive acylchlorided group and amino/hydroxyl groups on collagen. Subsequently, the structure of collagen-PLA was confirmed by Fourier transform infrared spectroscopy, fluorescein isothiocyanate-labeled fluorescence spectroscopy, X-ray photoelectron spectroscopy, and DSC analyses. Finally, some properties of collagen-PLA, such as hydrophilicity, cell compatibility and degradability were characterized. Results showed that collagen had been grafted onto the PLA with 5% graft ratio. Water contact angle and water absorption behavior tests indicated that the hydrophilicity of collagen-PLA was significantly higher than that of PLA. The cell compatibility of collagen-PLA with mouse embryonic fibroblasts (3T3) was also significantly better than PLA in terms of cell morphology and cell proliferation, and the degradability of PLA was also improved after introducing collagen. Results suggested that collagen-PLA was a promising candidate for biomedical applications.

  1. Photoelectrocatalytic degradation of benzoic acid using Au doped TiO2 thin films.

    PubMed

    Mohite, V S; Mahadik, M A; Kumbhar, S S; Hunge, Y M; Kim, J H; Moholkar, A V; Rajpure, K Y; Bhosale, C H

    2015-01-01

    Highly transparent pure and Au doped TiO2 thin films are successfully deposited by using simple chemical spray pyrolysis technique. The effect of Au doping onto the structural and physicochemical properties has been investigated. The PEC study shows that, both short circuit current (Isc) and open circuit voltage (Voc) are (Isc=1.81mA and Voc=890mV) relatively higher at 3at.% Au doping percentage. XRD study shows that the films are nanocrystalline in nature with tetragonal crystal structure. FESEM images show that the film surface covered with a smooth, uniform, compact and rice shaped nanoparticles. The Au doped thin films exhibit indirect band gap, decreases from 3.23 to 3.09eV with increase in Au doping. The chemical composition and valence states of pure and Au doped TiO2 films are studied by using X-ray photoelectron spectroscopy. The photocatalytic degradation effect is 49% higher in case 3at.% Au doped TiO2 than the pure TiO2 thin film photoelectrodes in the degradation of benzoic acid. It is revealed that Au doped TiO2 can be reused for five cycles of experiments without a requirement of post-treatment while the degradation efficiency was retained.

  2. Effect of dietary starch level and its rumen degradability on lamb meat fatty acid composition.

    PubMed

    Oliveira, Maria A; Alves, Susana P; Santos-Silva, José; Bessa, Rui J B

    2017-01-01

    Forty lambs were fed one of four diets supplemented with a linseed and sunflower oil blend but differing in starch level (mid, ≈35 vs. high, ≈50%) and starch rumen degradability (mid, ≈70 vs. high, ≈80%). The effects of diet on growth, carcass traits and meat fatty acid (FA) composition, with emphasis on biohydrogenation intermediates were evaluated. Lambs stayed on trial for 5weeks until slaughter. Treatment had no effect on animal performance and carcass traits. High-degradability diets decreased (P=0.04) meat shear force compared with mid-degradability diets. Lipid content of meat was unaffected by the diet. Mid-starch diets increased (P<0.05) the saturated FA and cis-MUFA but decreased (P<0.05) the trans-MUFA, particularly the t10-18:1, when compared with high-starch diets. The t11-18:1 (0.7% of total FA) and c9,t11-18:2 (<0.3%) remained low and the 18:3n-3 remained high (1.74%) and unaffected by diet.

  3. Solar photoelectro-Fenton degradation of the herbicide 4-chloro-2-methylphenoxyacetic acid optimized by response surface methodology.

    PubMed

    Garcia-Segura, Sergi; Almeida, Lucio Cesar; Bocchi, Nerilso; Brillas, Enric

    2011-10-30

    A central composite rotatable design and response surface methodology (RSM) were used to optimize the experimental variables of the solar photoelectro-Fenton (SPEF) treatment of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA). The experiments were made with a flow plant containing a Pt/air-diffusion reactor coupled to a solar compound parabolic collector (CPC) under recirculation of 10 L of 186 mg L(-1) MCPA solutions in 0.05 M Na(2)SO(4) at a liquid flow rate of 180 L h(-1) with an average UV irradiation intensity of about 32 Wm(-2). The optimum variables found for the SPEF process were 5.0 A, 1.0mM Fe(2+) and pH 3.0 after 120 min of electrolysis. Under these conditions, 75% of mineralization with 71% of current efficiency and 87.7 k Wh kg(-1) TOC of energy consumption were obtained. MCPA decayed under the attack of generated hydroxyl radicals following a pseudo-first-order kinetics. Hydroxyl radicals also destroyed 4-chloro-2-methylphenol, methylhydroquinone and methyl-p-benzoquinone detected as aromatic by-products. Glycolic, maleic, fumaric, malic, succinic, tartronic, oxalic and formic acids were identified as generated carboxylic acids, which form Fe(III) complexes that are quickly photodecarboxylated by the UV irradiation of sunlight at the CPC photoreactor. A reaction sequence for the SPEF degradation of MCPA was proposed.

  4. Functional characterization of normal and degraded bovine meniscus: rate-dependent indentation and friction studies.

    PubMed

    Baro, Vincent J; Bonnevie, Edward D; Lai, Xiaohan; Price, Christopher; Burris, David L; Wang, Liyun

    2012-08-01

    The menisci are known to play important roles in normal joint function and the development of diseases such as osteoarthritis. However, our understanding of meniscus' load bearing and lubrication properties at the tissue level remains limited. The objective of this investigation was to characterize the site- and rate-dependency of the compressive and frictional responses of the meniscus under a spherical contact load. Using a custom testing device, indentation tests with rates of 1, 10, 25, 50, and 100μm/s were performed on bovine medial meniscus explants, which were harvested from five locations including the femoral apposing surface at the anterior, central, and posterior locations and the central portion at the deep layer and at the tibial apposing surface (n=5 per location). Sliding tests with rates of 0.05, 0.25, 1, and 5mm/s were performed on the central femoral aspect and central tibial aspect superficial samples (n=6 per location). A separate set of superficial samples were subjected to papain digestion and tested prior to and post treatment. Our findings are: i) the Hertz contact model can be used to fit the force responses of meniscus under the conditions tested; ii) the anterior region is significantly stiffer than the posterior region and tissue modulus does not vary with tissue depth at the central region; iii) the friction coefficient of the meniscus is on the order of 0.02 under migratory contacts and the femoral apposing surface tends to show lower friction than the tibial apposing surface; iv) the meniscus exhibits increased modulus and lubrication with increased indentation and sliding rates; v) matrix degradation impedes the functional load support and lubrication properties of the tissue. The site- and rate-dependent properties of the meniscus may be attributed to spatial variations of the tissue's biphasic structure. These properties substantiate the role of the meniscus as one of the important bearing surfaces of the knee. These data

  5. Controlling the degradation kinetics of porous iron by poly(lactic-co-glycolic acid) infiltration for use as temporary medical implants

    NASA Astrophysics Data System (ADS)

    Yusop, Abdul Hakim Md; Daud, Nurizzati Mohd; Nur, Hadi; Kadir, Mohammed Rafiq Abdul; Hermawan, Hendra

    2015-06-01

    Iron and its alloy have been proposed as biodegradable metals for temporary medical implants. However, the formation of iron oxide and iron phosphate on their surface slows down their degradation kinetics in both in vitro and in vivo scenarios. This work presents new approach to tailor degradation behavior of iron by incorporating biodegradable polymers into the metal. Porous pure iron (PPI) was vacuum infiltrated by poly(lactic-co-glycolic acid) (PLGA) to form fully dense PLGA-infiltrated porous iron (PIPI) and dip coated into the PLGA to form partially dense PLGA-coated porous iron (PCPI). Results showed that compressive strength and toughness of the PIPI and PCPI were higher compared to PPI. A strong interfacial interaction was developed between the PLGA layer and the iron surface. Degradation rate of PIPI and PCPI was higher than that of PPI due to the effect of PLGA hydrolysis. The fast degradation of PIPI did not affect the viability of human fibroblast cells. Finally, this work discusses a degradation mechanism for PIPI and the effect of PLGA incorporation in accelerating the degradation of iron.

  6. Controlling the degradation kinetics of porous iron by poly(lactic-co-glycolic acid) infiltration for use as temporary medical implants.

    PubMed

    Yusop, Abdul Hakim Md; Daud, Nurizzati Mohd; Nur, Hadi; Kadir, Mohammed Rafiq Abdul; Hermawan, Hendra

    2015-06-09

    Iron and its alloy have been proposed as biodegradable metals for temporary medical implants. However, the formation of iron oxide and iron phosphate on their surface slows down their degradation kinetics in both in vitro and in vivo scenarios. This work presents new approach to tailor degradation behavior of iron by incorporating biodegradable polymers into the metal. Porous pure iron (PPI) was vacuum infiltrated by poly(lactic-co-glycolic acid) (PLGA) to form fully dense PLGA-infiltrated porous iron (PIPI) and dip coated into the PLGA to form partially dense PLGA-coated porous iron (PCPI). Results showed that compressive strength and toughness of the PIPI and PCPI were higher compared to PPI. A strong interfacial interaction was developed between the PLGA layer and the iron surface. Degradation rate of PIPI and PCPI was higher than that of PPI due to the effect of PLGA hydrolysis. The fast degradation of PIPI did not affect the viability of human fibroblast cells. Finally, this work discusses a degradation mechanism for PIPI and the effect of PLGA incorporation in accelerating the degradation of iron.

  7. Controlling the degradation kinetics of porous iron by poly(lactic-co-glycolic acid) infiltration for use as temporary medical implants

    PubMed Central

    Yusop, Abdul Hakim Md; Daud, Nurizzati Mohd; Nur, Hadi; Kadir, Mohammed Rafiq Abdul; Hermawan, Hendra

    2015-01-01

    Iron and its alloy have been proposed as biodegradable metals for temporary medical implants. However, the formation of iron oxide and iron phosphate on their surface slows down their degradation kinetics in both in vitro and in vivo scenarios. This work presents new approach to tailor degradation behavior of iron by incorporating biodegradable polymers into the metal. Porous pure iron (PPI) was vacuum infiltrated by poly(lactic-co-glycolic acid) (PLGA) to form fully dense PLGA-infiltrated porous iron (PIPI) and dip coated into the PLGA to form partially dense PLGA-coated porous iron (PCPI). Results showed that compressive strength and toughness of the PIPI and PCPI were higher compared to PPI. A strong interfacial interaction was developed between the PLGA layer and the iron surface. Degradation rate of PIPI and PCPI was higher than that of PPI due to the effect of PLGA hydrolysis. The fast degradation of PIPI did not affect the viability of human fibroblast cells. Finally, this work discusses a degradation mechanism for PIPI and the effect of PLGA incorporation in accelerating the degradation of iron. PMID:26057073

  8. The geochemical evolution of low-molecular-weight organic acids derived from the degradation of petroleum contaminants in groundwater

    USGS Publications Warehouse

    Cozzarelli, I.M.; Baedecker, M.J.; Eganhouse, R.P.; Goerlitz, D.F.

    1994-01-01

    The geochemical evolution of low-molecular-weight organic acids in groundwater downgradient from a crude-oil spill near Bemidji, Minnesota, was studied over a five year period (1986-1990). The organic acids are metabolic intermediates of the degradation of components of the crude oil and are structurally related to hydrocarbon precursors. The concentrations of organic acids, particularly aliphatic acids, increase as the microbial alteration of hydrocarbons progresses. The organic-acid pool changes in composition and concentration over time and in space as the degradation processes shift from Fe(III) reduction to methanogenesis. Over time, the aquifer system evolves into one in which the groundwater contains more oxidized products of hydrocarbon degradation and the reduced forms of iron, manganese, and nitrogen. Laboratory microcosm experiments with aquifer material support the hypothesis that organic acids observed in the groundwater originate from the microbial degradation of aromatic hydrocarbons under anoxic conditions. The geochemistry of two other shallow aquifers in coastal plain sediments, one contaminated with creosote waste and the other with gasoline, were compared to the Bemidji site. The geochemical evolution of the low-molecular-weight organic acid pool in these systems is controlled, in part, by the presence of electron acceptors available for microbially mediated electron-transfer reactions. The depletion of electron acceptors in aquifers leads to the accumulation of aliphatic organic acids in anoxic groundwater. ?? 1994.

  9. Analysis of hydroxycinnamic acid degradation in Agrobacterium fabrum reveals a coenzyme A-dependent, beta-oxidative deacetylation pathway.

    PubMed

    Campillo, Tony; Renoud, Sébastien; Kerzaon, Isabelle; Vial, Ludovic; Baude, Jessica; Gaillard, Vincent; Bellvert, Floriant; Chamignon, Cécile; Comte, Gilles; Nesme, Xavier; Lavire, Céline; Hommais, Florence

    2014-06-01

    The soil- and rhizosphere-inhabiting bacterium Agrobacterium fabrum (genomospecies G8 of the Agrobacterium tumefaciens species complex) is known to have species-specific genes involved in ferulic acid degradation. Here, we characterized, by genetic and analytical means, intermediates of degradation as feruloyl coenzyme A (feruloyl-CoA), 4-hydroxy-3-methoxyphenyl-β-hydroxypropionyl-CoA, 4-hydroxy-3-methoxyphenyl-β-ketopropionyl-CoA, vanillic acid, and protocatechuic acid. The genes atu1416, atu1417, and atu1420 have been experimentally shown to be necessary for the degradation of ferulic acid. Moreover, the genes atu1415 and atu1421 have been experimentally demonstrated to be essential for this degradation and are proposed to encode a phenylhydroxypropionyl-CoA dehydrogenase and a 4-hydroxy-3-methoxyphenyl-β-ketopropionic acid (HMPKP)-CoA β-keto-thiolase, respectively. We thus demonstrated that the A. fabrum hydroxycinnamic degradation pathway is an original coenzyme A-dependent β-oxidative deacetylation that could also transform p-coumaric and caffeic acids. Finally, we showed that this pathway enables the metabolism of toxic compounds from plants and their use for growth, likely providing the species an ecological advantage in hydroxycinnamic-rich environments, such as plant roots or decaying plant materials.

  10. Degradation of Acid Orange 7 Dye in Two Hybrid Plasma Discharge Reactors

    NASA Astrophysics Data System (ADS)

    Shen, Yongjun; Lei, Lecheng; Zhang, Xingwang; Ding, Jiandong

    2014-11-01

    To get an optimized pulsed electrical plasma discharge reactor and to increase the energy utilization efficiency in the removal of pollutants, two hybrid plasma discharge reactors were designed and optimized. The reactors were compared via the discharge characteristics, energy transfer efficiency, the yields of the active species and the energy utilization in dye wastewater degradation. The results showed that under the same AC input power, the characteristics of the discharge waveform of the point-to-plate reactor were better. Under the same AC input power, the two reactors both had almost the same peak voltage of 22 kV. The peak current of the point-to-plate reactor was 146 A, while that of the wire-to-cylinder reactor was only 48.8 A. The peak powers of the point-to-plate reactor and the wire-to-cylinder reactor were 1.38 MW and 1.01 MW, respectively. The energy per pulse of the point-to-plate reactor was 0.2221 J, which was about 29.4% higher than that of the wire-to-cylinder reactor (0.1716 J). To remove 50% Acid Orange 7 (AO7), the energy utilizations of the point-to-plate reactor and the wire-to-cylinder reactor were 1.02 × 10-9 mol/L and 0.61 × 10-9 mol/L, respectively. In the point-to-plate reactor, the concentration of hydrogen peroxide in pure water was 3.6 mmol/L after 40 min of discharge, which was higher than that of the wire-to-cylinder reactor (2.5 mmol/L). The concentration of liquid phase ozone in the point-to-plate reactor (5.7 × 10-2 mmol/L) was about 26.7% higher than that in the wire-to-cylinder reactor (4.5 × 10-2 mmol/L). The analysis results of the variance showed that the type of reactor and reaction time had significant impacts on the yields of the hydrogen peroxide and ozone. The main degradation intermediates of AO7 identified by gas chromatography and mass spectrometry (GCMS) were acetic acid, maleic anhydride, p-benzoquinone, phenol, benzoic acid, phthalic anhydride, coumarin and 2-naphthol. Proposed degradation pathways were

  11. Experimental particle formation rates spanning tropospheric sulfuric acid and ammonia abundances, ion production rates, and temperatures

    NASA Astrophysics Data System (ADS)

    Kürten, Andreas; Bianchi, Federico; Almeida, Joao; Kupiainen-Määttä, Oona; Dunne, Eimear M.; Duplissy, Jonathan; Williamson, Christina; Barmet, Peter; Breitenlechner, Martin; Dommen, Josef; Donahue, Neil M.; Flagan, Richard C.; Franchin, Alessandro; Gordon, Hamish; Hakala, Jani; Hansel, Armin; Heinritzi, Martin; Ickes, Luisa; Jokinen, Tuija; Kangasluoma, Juha; Kim, Jaeseok; Kirkby, Jasper; Kupc, Agnieszka; Lehtipalo, Katrianne; Leiminger, Markus; Makhmutov, Vladimir; Onnela, Antti; Ortega, Ismael K.; Petäjä, Tuukka; Praplan, Arnaud P.; Riccobono, Francesco; Rissanen, Matti P.; Rondo, Linda; Schnitzhofer, Ralf; Schobesberger, Siegfried; Smith, James N.; Steiner, Gerhard; Stozhkov, Yuri; Tomé, António; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Wagner, Paul E.; Wimmer, Daniela; Ye, Penglin; Baltensperger, Urs; Carslaw, Ken; Kulmala, Markku; Curtius, Joachim

    2016-10-01

    Binary nucleation of sulfuric acid and water as well as ternary nucleation involving ammonia are thought to be the dominant processes responsible for new particle formation (NPF) in the cold temperatures of the middle and upper troposphere. Ions are also thought to be important for particle nucleation in these regions. However, global models presently lack experimentally measured NPF rates under controlled laboratory conditions and so at present must rely on theoretical or empirical parameterizations. Here with data obtained in the European Organization for Nuclear Research CLOUD (Cosmics Leaving OUtdoor Droplets) chamber, we present the first experimental survey of NPF rates spanning free tropospheric conditions. The conditions during nucleation cover a temperature range from 208 to 298 K, sulfuric acid concentrations between 5 × 105 and 1 × 109 cm-3, and ammonia mixing ratios from zero added ammonia, i.e., nominally pure binary, to a maximum of 1400 parts per trillion by volume (pptv). We performed nucleation studies under pure neutral conditions with zero ions being present in the chamber and at ionization rates of up to 75 ion pairs cm-3 s-1 to study neutral and ion-induced nucleation. We found that the contribution from ion-induced nucleation is small at temperatures between 208 and 248 K when ammonia is present at several pptv or higher. However, the presence of charges significantly enhances the nucleation rates, especially at 248 K with zero added ammonia, and for higher temperatures independent of NH3 levels. We compare these experimental data with calculated cluster formation rates from the Atmospheric Cluster Dynamics Code with cluster evaporation rates obtained from quantum chemistry.

  12. Energetics and kinetics of anaerobic aromatic and fatty acid degradation. Progress report, November 1993--November 1994

    SciTech Connect

    McInerney, M.J.

    1994-12-06

    Factors influencing the rate and extent of benzoate degradation by the anaerobic syntrophic consortia were studied. Nonlinear regression analysis showed that the cause of the benzoate threshold was not a diminished benzoate degradation capacity. Analysis of cocultures with hydrogen users that differed in their hydrogen utilization capacities showed that the threshold did not depend on the kinetic properties of the syntrophic partner. These data support a thermodynamic explanation for the threshold, and exclude the possibility that a change in the affinity of the enzyme system due to acetate inhibition caused the threshold. Modeling studies showed that the threshold value could be predicted from the concentrations of the end products, assuming a critical Gibb`s free energy value. This work shows that interspecies acetate transfer is important in controlling the extent of metabolism by syntrophic organisms.

  13. A C-Terminal Acidic Domain Regulates Degradation of the Transcriptional Coactivator Bob1

    PubMed Central

    Wong, Christina S. F.; Möller, Andreas

    2013-01-01

    Bob1 (Obf-1 or OCA-B) is a 34-kDa transcriptional coactivator encoded by the Pou2af1 gene that is essential for normal B-cell development and immune responses in mice. During lymphocyte activation, Bob1 protein levels dramatically increase independently of mRNA levels, suggesting that the stability of Bob1 is regulated. We used a fluorescent protein-based reporter system to analyze protein stability in response to genetic and physiological perturbations and show that, while Bob1 degradation is proteasome mediated, it does not require ubiquitination of Bob1. Furthermore, degradation of Bob1 in B cells appears to be largely independent of the E3 ubiquitin ligase Siah. We propose a novel mechanism of Bob1 turnover in B cells, whereby an acidic region in the C terminus of Bob1 regulates the activity of degron signals elsewhere in the protein. Changes that make the C terminus more acidic, including tyrosine phosphorylation-mimetic mutations, stabilize the instable murine Bob1 protein, indicating that B cells may regulate Bob1 stability and activity via signaling pathways. Finally, we show that expressing a stable Bob1 mutant in B cells suppresses cell proliferation and induces changes in surface marker expression commonly seen during B-cell differentiation. PMID:24061476

  14. Enhanced propionic acid degradation (EPAD) system: proof of principle and feasibility.

    PubMed

    Ma, Jingxing; Carballa, Marta; Van De Caveye, Pieter; Verstraete, Willy

    2009-07-01

    Full-scale anaerobic single-phase digesters can be confronted with process instabilities, which often result in the accumulation of propionic acid (HPr). As a solution, an enhanced propionic acid degradation (EPAD) system has been conceptually designed and experimentally tested at lab-scale. The system consisted of two components: a liquid/solid separator containing a microfiltration membrane and an up-flow anaerobic sludge bed (UASB) reactor specialized in HPr degradation. Two lab-scale continuous stirred tank reactors (CSTR) were used, i.e. the CSTR(control) and the CSTR(treatment). Firstly, the CSTRs were stressed by organic overloading to obtain high HPr levels. During the recovery period, besides stop feeding, no actions were taken to decrease the residual HPr concentration in the CSTR(control), while the CSTR(treatment) was connected to EPAD system in order to accelerate its recovery. By the end of the experiment, the CSTR(treatment) completely recovered from HPr accumulation, while no significant decrease of the HPr level in the CSTR(control) was observed. Based on the experimental results, the up-scaling of EPAD system was evaluated and it would only account for about 2% of the volume of the full-scale digester, thus suggesting that the implementation of a mobile EPAD system in full-scale practice should be feasible.

  15. Pristine environments harbor a new group of oligotrophic 2,4-dichlorophenoxyacetic acid-degrading bacteria.

    PubMed Central

    Kamagata, Y; Fulthorpe, R R; Tamura, K; Takami, H; Forney, L J; Tiedje, J M

    1997-01-01

    2,4-Dichlorophenoxyacetic acid (2,4-D)-degrading bacteria were isolated from pristine environments which had no history of 2,4-D exposure. By using 2,4-D dye indicator medium or 14C-labeled 2,4-D medium, six strains were isolated from eight enrichment cultures capable of degrading 2,4-D. Phylogenetic analyses based on 16S ribosomal DNA (rDNA) sequencing and physiological properties revealed that one isolate from Hawaiian volcanic soil could be classified in the genus Variovorax (a member of the beta subdivision of the class Proteobacteria) and that the other five isolates from Hawaiian volcanic soils, Saskatchewan forest soil, and Chilean forest soil have 16S rDNAs with high degrees of similarity to those of the Bradyrhizobium group (a member of the alpha subdivision of the class Proteobacteria). All the isolates grow slowly on either nutrient media (0.1 x Bacto Peptone-tryptone-yeast extract-glucose [PTYG] or 0.1 x Luria broth [LB] medium) or 2,4-D medium, with mean generation times of 16 to 30 h, which are significantly slower than previously known 2,4-D degraders. Nutrient-rich media such as full-strength PTYG and LB medium did not allow their growth. PCR amplification using internal consensus sequences of tfdA (a gene encoding an enzyme for the first step of 2,4-D mineralization, found in pJP4 of Alcaligenes eutrophus JMP134 and some other 2,4-D-degrading bacteria) as primers and Southern hybridization with pJP4-tfdA as a probe revealed that the isolate belonging to the genus Variovorax carried the tfdA gene. This gene was transmissible to A. eutrophus JMP228 carrying a plasmid with a mutant tfdA gene. The other five isolates did not appear to carry tfdA, and 2,4-D-specific alpha-ketoglutarate-dependent dioxygenase activity could not be detected in cell lysates. These results indicate that 2,4-D-degrading bacteria in pristine environments are slow-growing bacteria and that most of their phylogenies and catabolic genes differ from those of 2,4-D degraders

  16. Multilayer Capsules of Bovine Serum Albumin and Tannic Acid for Controlled Release by Enzymatic Degradation.

    PubMed

    Lomova, Maria V; Brichkina, Anna I; Kiryukhin, Maxim V; Vasina, Elena N; Pavlov, Anton M; Gorin, Dmitry A; Sukhorukov, Gleb B; Antipina, Maria N

    2015-06-10

    With the purpose to replace expensive and significantly cytotoxic positively charged polypeptides in biodegradable capsules formed via Layer-by-Layer (LbL) assembly, multilayers of bovine serum albumin (BSA) and tannic acid (TA) are obtained and employed for encapsulation and release of model drugs with different solubility in water: hydrophilic-tetramethylrhodamine-isothiocyanate-labeled BSA (TRITC-BSA) and hydrophobic 3,4,9,10-tetra-(hectoxy-carbonyl)-perylene (THCP). Hydrogen bonding is proposed to be predominant within thus formed BSA/TA films. The TRITC-BSA-loaded capsules comprising 6 bilayers of the protein and polyphenol are benchmarked against the shells composed of dextran sulfate (DS) and poly-l-arginine (PARG) on degradability by two proteolytic enzymes with different cleavage site specificity (i.e., α-chymotrypsin and trypsin) and toxicity for murine RAW264.7 macrophage cells. Capsules of both types possess low cytotoxicity taken at concentrations equal or below 50 capsules per cell, and evident susceptibility to α-chymotrypsin resulted in release of TRITC-BSA. While the BSA/TA-based capsules clearly display resistance to treatment with trypsin, the assemblies of DS/PARG extensively degrade. Successful encapsulation of THCP in the TRITC-BSA/TA/BSA multilayer is confirmed, and the release of the model drug is observed in response to treatment with α-chymotrypsin. The thickness, surface morphology, and enzyme-catalyzed degradation process of the BSA/TA-based films are investigated on a planar multilayer comprising 40 bilayers of the protein and polyphenol deposited on a silicon wafer. The developed BSA/TA-based capsules with a protease-specific degradation mechanism are proposed to find applications in personal care, pharmacology, and the development of drug delivery systems including those intravenous injectable and having site-specific release capability.

  17. Quantitative TOF-SIMS analysis of oligomeric degradation products at the surface of biodegradable poly(alpha-hydroxy acid)s.

    PubMed

    Lee, Joo-Woon; Gardella, Joseph A

    2002-09-01

    This paper reports the development of a new method for quantification of the hydrolytic surface degradation kinetics of biodegradable poly(alpha-hydroxy acid)s using time-of-flight secondary ion mass spectrometry (TOF-SIMS). We report results from static SIMS spectra of a series of poly(alpha-hydroxy acid)s including poly(glycolic acid), poly(L-lactic acid), and random poly(D,L-lactic acid-co-glycolic acid) hydrolyzed in various buffer systems. The distribution of the most intense peak intensities of ions generated in high mass range of the spectrum reflects the intact degradation products (oligomeric hydrolysis products) of each biodegradable polymer. First, a detailed analysis of the oligomeric ions is given based on rearrangement of the intact hydrolysis products. The pattern of ions can distinguish both degradation-generated intact oligomers and their fragment ion peaks with a variety of combinations of each repeat unit. Then, the integration and summation of the area of all ion peaks with the same number of repeat units is proposed as a measurement that provides a more accurate MW average than the typically used method which counts only the most intense peak. The multiple ion summation method described in this paper would be practical in the improvement of quantitative TOF-SIMS studies as a better data reduction method, especially in the surface degradation kinetics of biodegradable polymers.

  18. Ligand-functionalized degradable polyplexes formed by cationic poly(aspartic acid)-grafted chitosan-cyclodextrin conjugates

    NASA Astrophysics Data System (ADS)

    Song, Hai-Qing; Li, Rui-Quan; Duan, Shun; Yu, Bingran; Zhao, Hong; Chen, Da-Fu; Xu, Fu-Jian

    2015-03-01

    Polypeptide-based degradable polyplexes attracted considerable attention in drug delivery systems. Polysaccharides including cyclodextrin (CD), dextran, and chitosan (CS) were readily grafted with cationic poly(aspartic acid)s (PAsps). To further enhance the transfection performances of PAsp-based polyplexes, herein, different types of ligand (folic acid, FA)-functionalized degradable polyplexes were proposed based on the PAsp-grafted chitosan-cyclodextrin conjugate (CCPE), where multiple β-CDs were tied on a CS chain. The FA-functionalized CCPE (i.e., CCPE-FA) was obtained via a host-guest interaction between the CD units of CCPE and the adamantane (Ad) species of Ad-modified FA (Ad-FA). The resulting CCPE/pDNA, CCPE-FA/pDNA, and ternary CCPE-FA/CCPE/pDNA (prepared by layer-by-layer assembly) polyplexes were investigated in detail using different cell lines. The CCPE-based polyplexes displayed much higher transfection efficiencies than the CS-based polyplexes reported earlier by us. The ternary polyplexes of CCPE-FA/CCPE/pDNA produced excellent gene transfection abilities in the folate receptor (FR)-positive tumor cells. This work would provide a promising means to produce highly efficient polyplexes for future gene therapy applications.Polypeptide-based degradable polyplexes attracted considerable attention in drug delivery systems. Polysaccharides including cyclodextrin (CD), dextran, and chitosan (CS) were readily grafted with cationic poly(aspartic acid)s (PAsps). To further enhance the transfection performances of PAsp-based polyplexes, herein, different types of ligand (folic acid, FA)-functionalized degradable polyplexes were proposed based on the PAsp-grafted chitosan-cyclodextrin conjugate (CCPE), where multiple β-CDs were tied on a CS chain. The FA-functionalized CCPE (i.e., CCPE-FA) was obtained via a host-guest interaction between the CD units of CCPE and the adamantane (Ad) species of Ad-modified FA (Ad-FA). The resulting CCPE/pDNA, CCPE

  19. Degradation Rate of 5-Fluorouracil in Metastatic Colorectal Cancer: A New Predictive Outcome Biomarker?

    PubMed Central

    Botticelli, Andrea; Borro, Marina; Onesti, Concetta Elisa; Strigari, Lidia; Gentile, Giovanna; Cerbelli, Bruna; Romiti, Adriana; Occhipinti, Mario; Sebastiani, Claudia; Lionetto, Luana; Marchetti, Luca; Simmaco, Maurizio; Marchetti, Paolo; Mazzuca, Federica

    2016-01-01

    Background 5-FU based chemotherapy is the most common first line regimen used for metastatic colorectal cancer (mCRC). Identification of predictive markers of response to chemotherapy is a challenging approach for drug selection. The present study analyzes the predictive role of 5-FU degradation rate (5-FUDR) and genetic polymorphisms (MTHFR, TSER, DPYD) on survival. Materials and Methods Genetic polymorphisms of MTHFR, TSER and DPYD, and the 5-FUDR of homogenous patients with mCRC were retrospectively studied. Genetic markers and the 5-FUDR were correlated with clinical outcome. Results 133 patients affected by mCRC, treated with fluoropyrimidine-based chemotherapy from 2009 to 2014, were evaluated. Patients were classified into three metabolic classes, according to normal distribution of 5-FUDR in more than 1000 patients, as previously published: poor-metabolizer (PM) with 5-FU-DR ≤ 0,85 ng/ml/106 cells/min (8 pts); normal metabolizer with 0,85 < 5-FU-DR < 2,2 ng/ml/106 cells/min (119 pts); ultra-rapid metabolizer (UM) with 5-FU-DR ≥ 2,2 ng/ml/106 cells/min (6 pts). PM and UM groups showed a longer PFS respect to normal metabolizer group (14.5 and 11 months respectively vs 8 months; p = 0.029). A higher G3-4 toxicity rate was observed in PM and UM, respect to normal metabolizer (50% in both PM and UM vs 18%; p = 0.019). No significant associations between genes polymorphisms and outcomes or toxicities were observed. Conclusion 5-FUDR seems to be significantly involved in predicting survival of patients who underwent 5-FU based CHT for mCRC. Although our findings require confirmation in large prospective studies, they reinforce the concept that individual genetic variation may allow personalized selection of chemotherapy to optimize clinical outcomes. PMID:27656891

  20. Degradation and Mineralization of Benzohydroxamic Acid by Synthesized Mesoporous La/TiO2

    PubMed Central

    Luo, Xianping; Wang, Junyu; Wang, Chunying; Zhu, Sipin; Li, Zhihui; Tang, Xuekun; Wu, Min

    2016-01-01

    Rare earth element La-doped TiO2 (La/TiO2) was synthesized by the sol-gel method. Benzohydroxamic acid was used as the objective pollutant to investigate the photocatalytic activity of La/TiO2. The physicochemical properties of the prepared materials were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, specific surface area and porosity, scanning electron microscopy and transmission electron microscopy. As a result, the doping of La could inhibit the crystal growth of TiO2, increase its specific surface area and expand its response to visible light, thus improving its photocatalytic activity. La/TiO2 with the doping ratio of 0.75% calcined at 500 °C, showing the highest photocatalytic activity to degrade benzohydroxamic acid under the irradiation of 300 W mercury lamp. About 94.1% of benzohydroxamic acid with the original concentration at 30 mg·L−1 was removed after 120 min in a solution of pH 4.4 with an La/TiO2 amount of 0.5 g·L−1. Furthermore, 88.5% of the total organic carbon was eliminated after 120 min irradiation. In addition, after four recycling runs, La/TiO2 still kept high photocatalytic activity on the photodegradation of benzohydroxamic acid. The interfacial charge transfer processes were also hypothesized. PMID:27735877

  1. Degradation and Mineralization of Benzohydroxamic Acid by Synthesized Mesoporous La/TiO₂.

    PubMed

    Luo, Xianping; Wang, Junyu; Wang, Chunying; Zhu, Sipin; Li, Zhihui; Tang, Xuekun; Wu, Min

    2016-10-10

    Rare earth element La-doped TiO₂ (La/TiO₂) was synthesized by the sol-gel method. Benzohydroxamic acid was used as the objective pollutant to investigate the photocatalytic activity of La/TiO₂. The physicochemical properties of the prepared materials were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, specific surface area and porosity, scanning electron microscopy and transmission electron microscopy. As a result, the doping of La could inhibit the crystal growth of TiO₂, increase its specific surface area and expand its response to visible light, thus improving its photocatalytic activity. La/TiO₂ with the doping ratio of 0.75% calcined at 500 °C, showing the highest photocatalytic activity to degrade benzohydroxamic acid under the irradiation of 300 W mercury lamp. About 94.1% of benzohydroxamic acid with the original concentration at 30 mg·L(-1) was removed after 120 min in a solution of pH 4.4 with an La/TiO₂ amount of 0.5 g·L(-1). Furthermore, 88.5% of the total organic carbon was eliminated after 120 min irradiation. In addition, after four recycling runs, La/TiO₂ still kept high photocatalytic activity on the photodegradation of benzohydroxamic acid. The interfacial charge transfer processes were also hypothesized.

  2. Concentrating versus non-concentrating reactors for solar photocatalytic degradation of p-nitrotoluene-o-sulfonic acid.

    PubMed

    Parra, S; Malato, S; Blanco, J; Péringer, P; Pulgari, C

    2001-01-01

    The photocatalytic oxidation of the non-biodegradable p-nitrotoluene-o-sulfonic acid (p-NTS) in homogeneous (photo-Fenton reactions) and heterogeneous (with TiO2) solutions has been studied at a pilot-scale under solar irradiation at the Plataforma Solar de Almeria (PSA). In this study two different reactors were tested: a medium concentrating radiation system (Heliomans, HM) and a non-concentrating radiation system (CPC). Their advantages and disadvantages for p-NTS degradation have been compared and discussed. The degradation rates obtained in the CPC collector are around three times more efficient than in the HM collectors. However, in both systems, 100% of the initial concentration of p-NTS was removed. Kinetic experiments were performed in both systems using TiO2 suspensions. During the photodegradation, the disappearance of p-NTS was followed by HPLC, the mineralization of the solution by the TOC technique, the evolution of NO3-, NO2-, and SO4(2-) concentration by ionic chromatography, the toxicity by the standard Microtox test, and the biodegradability by BOD5 and COD measurements. The obtained results demonstrated the utility of the heterogeneous catalysis (using TiO2 as catalyst) as a pretreatment method that can be followed by a biological process.

  3. Synergy between surface adsorption and photocatalysis during degradation of humic acid on TiO2/activated carbon composites.

    PubMed

    Xue, Gang; Liu, Huanhuan; Chen, Quanyuan; Hills, Colin; Tyrer, Mark; Innocent, Francis

    2011-02-15

    A photocatalyst comprising nano-sized TiO(2) particles on granular activated carbon (GAC) was prepared by a sol-dipping-gel process. The TiO(2)/GAC composite was characterized by scanning electron microscopy (SEM), X-ray diffractiometry (XRD) and nitrogen sorptometry, and its photocatalytic activity was studied through the degradation of humic acid (HA) in a quartz glass reactor. The factors influencing photocatalysis were investigated and the GAC was found to be an ideal substrate for nano-sized TiO(2) immobilization. A 99.5% removal efficiency for HA from solution was achieved at an initial concentration of 15 mg/L in a period of 3h. It was found that degradation of HA on the TiO(2)/GAC composite was facilitated by the synergistic relationship between surface adsorption characteristics and photocatalytic potential. The fitting of experimental results with the Langmuir-Hinshelwood (L-H) model showed that the reaction rate constant and the adsorption constant values were 0.1124 mg/(L min) and 0.3402 L/mg. The latter is 1.7 times of the calculated value by fitting the adsorption equilibrium data into the Langmuir equation.

  4. Catalytic antibody degradation of ghrelin increases whole-body metabolic rate and reduces refeeding in fasting mice.

    PubMed

    Mayorov, Alexander V; Amara, Neri; Chang, Jason Y; Moss, Jason A; Hixon, Mark S; Ruiz, Diana I; Meijler, Michael M; Zorrilla, Eric P; Janda, Kim D

    2008-11-11

    Obesity is a chronic, costly, and globally prevalent condition, with excess caloric intake a suspected etiologic factor. Nonsurgical treatments are modestly efficacious, and weight loss maintenance is hampered by anti-famine homeostatic mechanisms. Ghrelin, a gastric hormone linked to meal initiation, energy expenditure, and fuel partitioning, is hypothesized to facilitate weight gain and impede weight loss. Unique among known animal peptides, the serine-3 residue of ghrelin is posttranslationally acylated with an n-octanoic acid, a modification important for the peptide's active blood-brain transport and growth hormone secretagogue receptor-1 agonist activity. Pharmacological degradation of ghrelin would be hypothesized to reduce ghrelin's biological effects. To study endogenous ghrelin's role in appetite and energy expenditure, we generated antibodies that hydrolyze the octanoyl moiety of ghrelin to form des-acyl ghrelin. The most proficient antibody catalyst, GHR-11E11, was found to display a second-order rate constant of 18 M(-1) x s(-1) for the hydrolysis of ghrelin to des-acyl ghrelin. I.v. administration of GHR-11E11 (50 mg/kg) maintained a greater metabolic rate in fasting C57BL/6J mice as compared with mice receiving a control antibody and suppressed 6-h refeeding after 24 h of food deprivation. Indirect respiratory measures of metabolism after refeeding and relative fuel substrate utilization were unaffected. The results support the hypothesis that acylated ghrelin stimulates appetite and curbs energy expenditure during deficient energy intake, whereas des-acyl ghrelin does not potently share these functions. Catalytic anti-ghrelin antibodies might thereby adjunctively aid consolidation of caloric restriction-induced weight loss and might also be therapeutically relevant to Prader-Willi syndrome, characterized after infancy by hyperghrelinemia, hyperphagia, and obesity.

  5. Degradation of 3-phenoxybenzoic acid by a filamentous fungus Aspergillus oryzae M-4 strain with self-protection transformation.

    PubMed

    Zhu, Yuanting; Li, Jianlong; Yao, Kai; Zhao, Nan; Zhou, Kang; Hu, Xinjie; Zou, Likou; Han, Xinfeng; Liu, Aiping; Liu, Shuliang

    2016-11-01

    A novel filamentous fungus M-4 strain was isolated from soy sauce koji and identified as Aspergillus oryzae (Collection number: CGMCC 11645) on the basis of morphological characteristics and internal transcribed spacer sequence. M-4 could degrade 80.62 % of 3-phenoxybenzoic acid (3-PBA; 100 mg L(-1)) within 5 days. 3-PBA degradation occurred in accordance with first-order kinetics. The degradation metabolites of 3-PBA were identified through high-performance liquid chromatography-mass spectrometry (HPLC-MS). Relevant enzymatic activities and substrate utilization were also investigated, which indicated that M-4 could effectively degrade the intermediates of 3-PBA. Base on analysis of these metabolites, a novel biochemical pathway for the degradation of 3-PBA was proposed. There exists a mutual transformation between 3-phenoxy-benzyl alcohol and 3-PBA, which was firstly reported about the degradation of 3-PBA and may be attributed to self-protection transformation of M-4; subsequently, 3-PBA was gradually transformed into phenol, 3-hydroxy-5-phenoxy benzoic acid, protocatechuic acid and gallic acid. The safety of M-4 was evaluated via an acute toxicity test in vivo. The biodegradation ability of M-4 without toxic effects reveals that this fungus may be likely to be used for eliminating 3-PBA from contaminated environment or fermented foods.

  6. Characterization of Wall Teichoic Acid Degradation by the Bacteriophage ϕ29 Appendage Protein GP12 Using Synthetic Substrate Analogs.

    PubMed

    Myers, Cullen L; Ireland, Ronald G; Garrett, Teresa A; Brown, Eric D

    2015-07-31

    The genetics and enzymology of the biosynthesis of wall teichoic acid have been the extensively studied, however, comparatively little is known regarding the enzymatic degradation of this biological polymer. The GP12 protein from the Bacillus subtilis bacteriophage ϕ29 has been implicated as a wall teichoic acid hydrolase. We have studied the wall teichoic acid hydrolase activity of pure, recombinant GP12 using chemically defined wall teichoic acid analogs. The GP12 protein had potent wall teichoic acid hydrolytic activity in vitro and demonstrated ∼13-fold kinetic preference for glycosylated poly(glycerol phosphate) teichoic acid compared with non-glycosylated. Product distribution patterns suggested that the degradation of glycosylated polymers proceeded from the hydroxyl terminus of the polymer, whereas hydrolysis occurred at random sites in the non-glycosylated polymer. In addition, we present evidence that the GP12 protein possesses both phosphodiesterase and phosphomonoesterase activities.

  7. Degradation of acid blue 40 dye solution and dye house wastewater from textile industry by photo-assisted electrochemical process.

    PubMed

    Moraes, Peterson B; Pelegrino, Rosangela R L; Bertazzoli, Rodnei

    2007-12-01

    In this paper, electrochemical and photo-assisted electrochemical processes are used for color, total organic carbon (TOC) and chemical oxygen demand (COD) degradation of one of the most abundant and strongly colored industrial wastewaters, which results from the dyeing of fibers and fabrics in the textile industry. The experiments were carried out in an 18 L pilot-scale tubular flow reactor with 70%TiO(2)/30%RuO(2) DSA. A synthetic acid blue 40 solution and real dye house wastewater, containing the same dye, were used for the experiments. By using current density of 80 mA cm(-2) electrochemical process has the capability to remove 80% of color, 46% of TOC and 69% of COD. When used the photochemical process with 4.6 mW cm(-2) of 254 nm UV-C radiation to assist the electrolysis, has been obtained 90% of color, 64% of TOC and 60% of COD removal in 90 minutes of processing; furthermore, 70% of initial color was degraded within the first 15 minutes. Experimental runs using dye house wastewater resulted in 78% of color, 26% of TOC and 49% of COD in electrolysis at 80 mA cm(-2) and 90 min; additionally, when photo-assisted, electrolysis resulted in removals of 85% of color, 42% of TOC and 58% of COD. For the operational conditions used in this study, color, TOC and COD showed pseudo-first-order decaying profiles. Apparent rate constants for degradation of TOC and COD were improved by one order of magnitude when the photo-electrochemical process was used.

  8. Comparison of H2O2/UV and heterogeneous photocatalytic processes for the degradation of dichloroacetic acid in water.

    PubMed

    Zalazar, C S; Satuf, M L; Alfano, O M; Cassano, A E

    2008-08-15

    A comparative study between two advanced oxidation technologies for pollutant degradation has been made. With the use of dichloroacetic acid (DCA) as the model pollutant, the reactions with hydrogen peroxide and UV radiation (H2O2/UV, 253.7 nm) and photocatalysis with titanium dioxide (TiO2/UV, 300-400 nm) are analyzed. Three criteria have been selected to compare the performances of both processes: (i) the percentage conversion of DCA and TOC (total organic carbon) at a fixed reaction time; (ii) the quantum efficiency, employing the true radiation absorption rates for both activated species (H2O2 and TiO2); (iii) the specific energy consumption to degrade 50% of the initial TOC. The optimal molar concentration ratio of H2O2/DCA and the optimal catalyst concentration have been employed in the experiments. The results indicate that, under the optimal operating conditions, the H2O2/UV process exhibits, by a large difference, the best performance taking into account the above-mentioned criteria. Nevertheless, both systems show similar values of specific energy consumption when a thinner reactor is employed. These results cannot be safely extrapolated to other contexts if (i) other compounds of different structure are degraded and (ii) a different catalyst is used. Moreover, they were obtained under optimized conditions, and typical, real-life situations may render quite different results due to the robustness of the titanium dioxide operation. They should serve as an indication that, under the studied conditions, a much-improved catalyst performance must be achieved to parallel, with a heterogeneous process, a yield similar to the one obtained with the homogeneous system.

  9. Wood source and pyrolysis temperature interact to control PyOM degradation rates

    NASA Astrophysics Data System (ADS)

    Bird, J. A.; Hatton, P. J.; Filley, T. R.; Chatterjee, S.; Auclerc, A.; Gormley, M.; Dastmalchi, K.; Stark, R. E.; Nadelhoffer, K. J.

    2015-12-01

    Surprisingly little is known about how shifts in tree species composition and increased forest fire frequency and intensity will affect one of the most stable pools of soil organic matter, i.e. the pyrogenic organic matter (PyOM or char). In a previous study, we showed that wood source and pyrolysis temperature interact to control PyOM structure and potential reactivity for two tree species common in high-latitude forests, jack pine (JP) and red maple (RM). Here, we investigate whether these differences affect PyOM turnover by examining the fates of 13C/15N-enriched JP wood and PyOM pyrolyzed at 300 (JP300) and 450 °C (JP450) and RM pyrolyzed at 450 °C (RM450). The substrates were applied 1-3 cm below the O/A interface of a well-drained Spodosol in a long-term forest fire study located at the University of Michigan Biological Station (Pellston, MI, USA). 13C-CO2effluxes from the first 996 days of decay showed a significant wood source by pyrolysis temperature interaction on PyOM field mineralisation rates, with RM450 mineralising twice faster than JP450 during the first 90 days. Increasing pyrolysis temperature substantially decreased field mineralization rates during the first 996 days, with mineralisation rates 24 and 80 times slower for JP300 and JP450 compared with JP wood. After 1 year, (i) bacterial groups were large sinks for PyOM-derived C as pyrolysis temperature increased and as substrate use efficiency decreased; (ii) potential phenol oxidase and net peroxidase activities were unaffected by the PyOM addition, although net peroxidase activities measured tended to lesser for soils amended with JP450 and RM450; and (iii) Collembola detritivores appeared less likely to be found for soils amended with JP450 and RM450. PyOM-derived C and N recoveries did not differ after 1 year; we will present 3-y recovery data. Our results suggest that the composition of angiosperms (e.g. RM) and gymnosperms (e.g. JP) in high-latitude forests is an underappreciated but

  10. Nitrogen mineralization rates of the acidic, xeric soils of the New Jersey Pinelands: field rates

    SciTech Connect

    Poovarodom, S.; Tate, R.L. III; Bloom, R.A.

    1988-04-01

    Using the buried-bag procedure, the authors quantified nitrogen mineralization rates in the xeric, acidic Lakehurst, and Atsion sands of the New Jersey Pine Barrens. Average annual nitrogen yields in the upper 15 cm for the Lakehurst and the Atsion sands were 38.4 and 53.0 kg N/ha, corresponding to 4.5 and 2.5% of the total nitrogen, respectively. Net nitrogen mineralization in both soils exhibited distinct seasonal patterns with maxima in summer and minimum rates in the winter. Nitrification accounted for only 5% of the total N mineralized in both soils. This is consistent with the finding of low populations of autotrophic nitrifiers in these soils.

  11. Quantify Degradation Rates and Mechanisms of PV Modules and Systems Installed in Florida Through Comprehensive Experimental and Theoretical Analysis (Poster)

    SciTech Connect

    Sorloaica-Hickman, N.; Davis, K.; Kurtz, S.; Jordan, D.

    2011-02-01

    The economic viability of photovoltaic (PV) technologies is inextricably tied to both the electrical performance and degradation rate of the PV systems, which are the generators of electrical power in PV systems. Over the past 15 years, performance data have been collected on numerous PV systems installed throughout the state of Florida and will be presented.

  12. Degradation of sunscreen agent p-aminobenzoic acid using a combination system of UV irradiation, persulphate and iron(II).

    PubMed

    Xue, Yicen; Dong, Wenbo; Wang, Xiaoning; Bi, Wenlong; Zhai, Pingping; Li, Hongjing; Nie, Minghua

    2016-03-01

    Increased usage and discharge of sunscreens have led to ecological safety crisis, and people are developing the advanced oxidation processes (AOPs) to treat them. The present study aimed to determine the degradation efficiency and mechanism of the sunscreen agent p-aminobenzoic acid (PABA) using the UV/Fe(2+)/persulphate (PS) method. A series of irradiation experiments were conducted to optimise the system conditions and to study the impacts of the natural anion. Free radicals and degradation products were identified in order to clarify the degradation mechanism. Initial PS and Fe(2+) concentrations showed significant impacts on PABA degradation. Natural anions, such as Cl(-), NO3 (-), H2PO4 (-) and HCO3 (-), impeded PABA degradation because of ion (Fe(2+)) capture, radical scavenging or pH effects. Hydroxyl (HO·) and sulphate (SO4 (·-)) radicals were two main radicals observed in the UV/Fe(2+)/PS system; of these, SO4 (·-) showed greater effects on PABA degradation. Over 99 % of the available PABA was completely degraded into carbon dioxide (CO2) and water (H2O) by the UV/Fe(2+)/PS system, and the remaining PABA participated in complex radical reactions. By-products were identified by total ion chromatography and mass spectrometry. Our research provides a treatment process for PABA with high degradation efficiency and environmental safety and introduces a new strategy for sunscreen degradation.

  13. Biodegradation of geosmin by a novel Gram-negative bacterium; isolation, phylogenetic characterisation and degradation rate determination.

    PubMed

    Hoefel, Daniel; Ho, Lionel; Monis, Paul T; Newcombe, Gayle; Saint, Christopher P

    2009-06-01

    Biologically active sand filters within water treatment plants (WTPs) are now recognised as an effective barrier for the removal of geosmin. However, little is known regarding the actual microbiological processes occurring or the bacteria capable of degrading geosmin. This study reports the enrichment and isolation of a Gram-negative bacterium, Geo48, from the biofilm of a WTP sand filter where the isolate was shown to effectively degrade geosmin individually. Experiments revealed that Geo48 degraded geosmin in a planktonic state by a pseudo-first-order mechanism. Initial geosmin concentrations ranging from 100 to 1000ng/l were shown to directly influence geosmin degradation in reservoir water by Geo48, with rate constants increasing from 0.010h(-1) (R(2)=0.93) to 0.029h(-1) (R(2)=0.97) respectively. Water temperature also influenced degradation of geosmin by Geo48 where temperatures of 11, 22 and 30 degrees C resulted in rate constants of 0.017h(-1) (R(2)=0.98), 0.023h(-1) (R(2)=0.91) and 0.019h(-1) (R(2)=0.85) respectively. Phylogenetic analysis using the 16S rRNA gene of Geo48 revealed it was a member of the Alphaproteobacteria and clustered with 99% bootstrap support with an isolate designated Geo24, a Sphingopyxis sp. previously described as degrading geosmin but only as a member of a bacterial consortium. Of the previously described bacteria, Geo48 was most similar to Sphingopyxis alaskensis (97.2% sequence similarity to a 1454bp fragment of the 16S rRNA gene). To date, this is the only study to report the isolation and characterisation of a Gram-negative bacterium from a biologically active sand filter capable of the sole degradation of geosmin.

  14. Protein degradation in preimplantation mouse embryos and the lethality of tritiated amino acids

    SciTech Connect

    Wielbold, J.L.

    1982-01-01

    The role of protein degradation in preimplantation development in the mouse was studied. Proteins of morulae and blastocysts (M and B) cultured in vitro after labeling for 1 hour (h) in /sup 3/H-leucine exhibit a mean half-life (t/sub 1///sub 2/) of 8.1 h. The t/sub 1///sub 2/ tends to increase (9.5 h) when 10% fetal calf serum is added to the chase medium. This decrease in protein degradation in the presence of serum is associated with an increase in the percentage of B that are hatching (P<0.02). This rate of protein degradation in vivo was affected by the stage of pseudopregnancy (PSP) of the recipient. Day 4 embryos in a Day 4 uterus (Day 1=vaginal plug) retained more of the /sup 3/H-leucine in their proteins than did Day 4 embryos remaining in culture (P<0.02), while Day 4 embryos in a Day 3 uterus retained the same amount of radioactivity as did Day 4 embryos in culture. This differential effect of uterine environment was also seen when Day 4 embryos were transferred to recipients. More fetuses developed to term when the recipient was in Day 3 of PSP (50.8%) than when the recipient was in Day 4 PSP (25.9%, P<0.001), regardless of the age of the recipient. Age of the recipient does affect the percentage of transferred embryos developing to term. Thus, protein degradation may vary with the stage of embryo development and the conditions to which the embryos are exposed. However, even low levels of incorporated tritiated leucine can have lethal effects on the embryos and compromise the validity of the protein half-lives determined.

  15. Energetics and kinetics of anaerobic aromatic and fatty acid degradation. Progress report, June 1991--November 1992

    SciTech Connect

    McInerney, M.J.

    1992-11-16

    The kinetics of benzoate degradation by the anaerobic syntrophic bacterium, Syntrophus buswellii, was studied in coculture with Desulfovibrio strain G11. The threshold value for benzoate degradation was dependent on the acetate concentration with benzoate threshold values ranging from 2.4 {mu}M at 20 mM acetate to 30.0 {mu}M at 65 mM acetate. Increasing acetate concentrations also inhibited the rate of benzoate degradation with a apparent K{sub i} for acetate inhibition of 7.0 mM. Lower threshold values were obtained when nitrate rather than sulfate was the terminal electron acceptor. These data are consistent with a thermodynamic explanation for the threshold, and suggest that there is a minimum Gibbs free energy value required for the degradation of benzoate. An acetoacetyl-CoA thiolase has been isolated from Syntrophomonas wolfei; it is apparently a key enzyme controlling the synthesis of poly-B-hydroxyalkanoate from acetyl-CoA in this organism. Kinetic characterization of the acetoacetyl-CoA thiolase from S. wolfei showed that it is similar in its structural, kinetic, and apparent regulatory properties to other biosynthetic acetoacetyl-CoA thiolases from phylogenetically distinct bacteria that synthesize PHA. Intracellular concentrations of CoA and acetyl-CoA are believed to be critical factors regulating the activity of the acetoacetyl-CoA thiolase in S. wolfei. We have also isolated and characterized several new halophilic anaerobic fermentative anaerobes. Phylogenetic analysis indicates that one of these bacteria is a new species in the genus, Haloanaerobium. Two other species appear to be members of the genus, Halobacteroides. Several halophilic acetoclastic methanogenic bacteria have also been isolated and their physiological properties are currently under investigation. We have also isolated an acetate-using dissimilatory iron-reducing bacterium.

  16. Degradation Kinetics of VX

    SciTech Connect

    Gary S. Groenewold

    2010-12-01

    O-ethyl S-(2-diisopropylaminoethyl)phosphonothiolate (VX) is the most toxic of the conventional chemical warfare agents. It is a persistent compound, an attribute derived from its relative involatility and slow rates of hydrolysis. These properties suggest that VX can linger in an exposed environment for extended periods of time long after the air has cleared. Concern over prolonged risk from VX exposure is exacerbated by the fact that it poses a dermal contact hazard. Hence a detailed understanding of volatilization rates, and degradation pathways and rates occurring in various environments is needed. Historically, volatilization has not been considered to be an important mechanism for VX depletion, but recent studies have shown that a significant fraction of VX may volatilize, depending on the matrix. A significant body of research has been conducted over the years to unravel VX degradation reaction pathways and to quantify the rates at which they proceed. Rigorous measurement of degradation rates is frequently difficult, and thus in many cases the degradation of VX has been described in terms of half lives, while in fewer instances rate constants have been measured. This variable approach to describing degradation kinetics reflects uncertainty regarding the exact nature of the degradation mechanisms. In this review, rates of VX degradation are compared on the basis of pseudo-first order rate constants, in order to provide a basis for assessing likelihood of VX persistence in a given environment. An issue of specific concern is that one VX degradation pathway produces S-2-(diisopropylaminoethyl) methylphosphonothioic acid (known as EA2192), which is a degradation product that retains much of the original toxicity of VX. Consequently degradation pathways and rates for EA2192 are also discussed.

  17. Cathepsin D-mediated yolk protein degradation is blocked by acid phosphatase inhibitors.

    PubMed

    Fialho, Eliane; Nakamura, Angelica; Juliano, Luiz; Masuda, Hatisaburo; Silva-Neto, Mário A C

    2005-04-15

    Vitellin (VT) is a lipoglycophosphoprotein stored inside the eggs of every oviparous organism during oogenesis. In the blood-sucking bug Rhodnius prolixus, VT is deposited inside growing oocytes together with two acid hydrolases: acid phosphatase (AP) and cathepsin D (CD). Egg fertilization triggers AP activity and VT proteolysis in vivo [Insect Biochem. Mol. Biol. 2002 (32) 847]. Here, we show that CD is the main protease targeting VT proteolysis during egg development. CD activity in total egg homogenates is blocked by the classical aspartyl protease inhibitor, pepstatin A. Surprisingly, AP inhibitors such as NaF, Na+/K+ tartrate, and inorganic phosphate also block VT proteolysis, whereas this effect is not observed when tyrosine phosphatase inhibitors such as vanadate and phenylarsine oxide or an inhibitor of alkaline phosphatases such as levamisole are used in a VT proteolysis assay. NaF concentrations that block isolated AP activity do not affect the activity of partially purified CD. Therefore, a specific repressor of VT proteolysis must be dephosphorylated by AP in vivo. In conclusion, these results demonstrate for the first time that acid hydrolases act cooperatively to promote yolk degradation during egg development in arthropods.

  18. Thermal degradation behaviour of nanoamphiphilic chitosan dispersed poly (lactic acid) bionanocomposite films.

    PubMed

    Pal, Akhilesh Kumar; Katiyar, Vimal

    2017-02-01

    In the present study, nano-amphiphilic chitosan termed as chitosan-grafted-oligo l-lactic acid (CH-g-OLLA), is synthesized by microwave initiated insitu condensation polymerization. The synthesized CH-g-OLLA becomes hydrophobic in nature due to chemical bond formation between chitosan backbone and OLLA chains. Further, CH-g-OLLA (30%) bionanocomposite is used as a nanofiller in poly (lactic acid)/chitosan-grafted-oligo l-lactic acid (PLA/CH-g-OLLA) bionanocomposite films. Surface morphology shows a homogeneous dispersion of CH-g-OLLA in the form of spherical aggregates, which vary in the range of ∼20 to 150nm. Non-isothermal degradation kinetics, proposed by Kissinger, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa and Augis & Bennett models, are utilized to estimate the activation energies (Ea) for PLA, which are 254.1, 260.2, 257.0 and 259.1kJmol(-1) respectively. The reduction in Ea values of bionanocomposite films may be elucidated by intermolecular distance and enrichment in chain mobility. The evolved gaseous products like hydrocarbons, carbon dioxide, carbon monoxide and cyclic oligomers are successfully identified with TG-FTIR analysis.

  19. Anaerobic degradation of oleic acid by suspended and granular sludge: identification of palmitic acid as a key intermediate.

    PubMed

    Pereira, M A; Pires, O C; Mota, M; Alves, M M

    2002-01-01

    The aim of the present work was to study the maximum potential methane production in batch assays of sludge samples taken along the operation of two EGSB reactors (RI inoculated with granular sludge and RII inoculated with suspended sludge) fed with increasing oleic acid concentrations between 2 and 8 gCOD/l (HRT = 1 day). After removing the residual substrate, the sludge was incubated in batch vials without any added carbon source. A maximum methane production rate of 152+/-21 mlCH4(STP)/gVS.day was obtained for the suspended sludge taken on day 70, when oleate at a concentration of 2 g COD/l was fed with a co-substrate (50% COD). The maximum plateau achieved in the methane production curve was 1145+/-307 mlCH4(STP)/gVS, obtained for the suspended sludge taken on day 162, when oleate was fed as the sole carbon source at 6 g COD/I. The methanization rate of the adsorbed substrate was enhanced under stirring conditions and was inhibited by adding oleic acid. Extraction and GC analysis confirmed that the main adsorbed substrate was palmitate, and not oleate. Accumulated palmitate adsorbed onto the sludge and further beta-oxidation was inhibited when in the presence of oleic acid. If oleic acid was removed from the medium beta-oxidation proceeded with methane production. Suspended sludge was more efficient than granular sludge.

  20. The effect of microbubbles on gas-liquid mass transfer coefficient and degradation rate of COD in wastewater treatment.

    PubMed

    Yao, Kangning; Chi, Yong; Wang, Fei; Yan, Jianhua; Ni, Mingjiang; Cen, Kefa

    2016-01-01

    A commonly used aeration device at present has the disadvantages of low mass transfer rate because the generated bubbles are several millimeters in diameter which are much bigger than microbubbles. Therefore, the effect of a microbubble on gas-liquid mass transfer and wastewater treatment process was investigated. To evaluate the effect of each bubble type, the volumetric mass transfer coefficients for microbubbles and conventional bubbles were determined. The volumetric mass transfer coefficient was 0.02905 s(-1) and 0.02191 s(-1) at a gas flow rate of 0.67 L min(-1) in tap water for microbubbles and conventional bubbles, respectively. The degradation rate of simulated municipal wastewater was also investigated, using aerobic activated sludge and ozone. Compared with the conventional bubble generator, the chemical oxygen demand (COD) removal rate was 2.04, 5.9, 3.26 times higher than those of the conventional bubble contactor at the same initial COD concentration of COD 200 mg L(-1), 400 mg L(-1), and 600 mg L(-1), while aerobic activated sludge was used. For the ozonation process, the rate of COD removal using microbubble generator was 2.38, 2.51, 2.89 times of those of the conventional bubble generator. Based on the results, the effect of initial COD concentration on the specific COD degradation rate were discussed in different systems. Thus, the results revealed that microbubbles could enhance mass transfer in wastewater treatment and be an effective method to improve the degradation of wastewater.

  1. Identification of microbial populations driving biopolymer degradation in acidic peatlands by metatranscriptomic analysis.

    PubMed

    Ivanova, Anastasia A; Wegner, Carl-Eric; Kim, Yongkyu; Liesack, Werner; Dedysh, Svetlana N

    2016-10-01

    Northern peatlands play a crucial role in the global carbon balance, serving as a persistent sink for atmospheric CO2 and a global carbon store. Their most extensive type, Sphagnum-dominated acidic peatlands, is inhabited by microorganisms with poorly understood degradation capabilities. Here, we applied a combination of barcoded pyrosequencing of SSU rRNA genes and Illumina RNA-Seq of total RNA (metatranscriptomics) to identify microbial populations and enzymes involved in degrading the major components of Sphagnum-derived litter and exoskeletons of peat-inhabiting arthropods: cellulose, xylan, pectin and chitin. Biopolymer addition to peat induced a threefold to fivefold increase in bacterial cell numbers. Functional community profiles of assembled mRNA differed between experimental treatments. In particular, pectin and xylan triggered increased transcript abundance of genes involved in energy metabolism and central carbon metabolism, such as glycolysis and TCA cycle. Concurrently, the substrate-induced activity of bacteria on these two biopolymers stimulated grazing of peat-inhabiting protozoa. Alveolata (ciliates) was the most responsive protozoa group as confirmed by analysis of both SSU rRNA genes and SSU rRNA. A stimulation of alphaproteobacterial methanotrophs on pectin was consistently shown by rRNA and mRNA data. Most likely, their significant enrichment was due to the utilization of methanol released during the degradation of pectin. Analysis of SSU rRNA and total mRNA revealed a specific response of Acidobacteria and Actinobacteria to chitin and pectin, respectively. Relatives of Telmatobacter bradus were most responsive among the Acidobacteria, while the actinobacterial response was primarily affiliated with Frankiales and Propionibacteriales. The expression of a wide repertoire of carbohydrate-active enzymes (CAZymes) corresponded well to the detection of a highly diverse peat-inhabiting microbial community, which is dominated by yet uncultivated

  2. D-Galacturonic Acid: A Highly Reactive Compound in Nonenzymatic Browning. 2. Formation of Amino-Specific Degradation Products.

    PubMed

    Wegener, Steffen; Bornik, Maria-Anna; Kroh, Lothar W

    2015-07-22

    Thermal treatment of aqueous solutions of D-galacturonic acid and L-alanine at pH 3, 5, and 8 led to rapid and more intensive nonenzymatic browning reactions compared to similar solutions of other uronic acids and to Maillard reactions of reducing sugars. The hemiacetal ring structures of uronic acids had a high impact on browning behavior and reaction pathways. Besides reductic acid (1,2-dihydroxy-2-cyclopenten-1-one), 4,5-dihydroxy-2-cyclopenten-1-one (DHCP), furan-2-carboxaldehyde, and norfuraneol (4-hydroxy-5-methyl-3-(2H)-furanone) could be detected as typical products of nonenzymatic uronic acid browning reactions. 2-(2-Formyl-1H-pyrrole-1-yl)propanoic acid (FPA) and 1-(1-carboxyethyl)-3-hydroxypyridin-1-ium (HPA) were identified as specific reaction products of uronic acids with amine participation like l-alanine. In contrast, the structurally related D-galacturonic acid methyl ester showed less browning activity and degradation under equal reaction conditions. Pectin-specific degradation products such as 5-formyl-2-furanoic acid and 2-furanoic acid were found but could not be verified for d-galacturonic acid monomers alone.

  3. Poly(ethylene glycol) (PEG)-lactic acid nanocarrier-based degradable hydrogels for restoring the vaginal microenvironment.

    PubMed

    Sundara Rajan, Sujata; Turovskiy, Yevgeniy; Singh, Yashveer; Chikindas, Michael L; Sinko, Patrick J

    2014-11-28

    Women with bacterial vaginosis (BV) display reduced vaginal acidity, which make them susceptible to associated infections such as HIV. In the current study, poly(ethylene glycol) (PEG) nanocarrier-based degradable hydrogels were developed for the controlled release of lactic acid in the vagina of BV-infected women. PEG-lactic acid (PEG-LA) nanocarriers were prepared by covalently attaching lactic acid to 8-arm PEG-SH via cleavable thioester bonds. PEG-LA nanocarriers with 4 copies of lactic acid per molecule provided controlled release of lactic acid with a maximum release of 23% and 47% bound lactic acid in phosphate buffered saline (PBS, pH7.4) and acetate buffer (AB, pH4.3), respectively. The PEG nanocarrier-based hydrogels were formed by cross-linking the PEG-LA nanocarriers with 4-arm PEG-NHS via degradable thioester bonds. The nanocarrier-based hydrogels formed within 20 min under ambient conditions and exhibited an elastic modulus that was 100-fold higher than the viscous modulus. The nanocarrier-based degradable hydrogels provided controlled release of lactic acid for several hours; however, a maximum release of only 10%-14% bound lactic acid was observed possibly due to steric hindrance of the polymer chains in the cross-linked hydrogel. In contrast, hydrogels with passively entrapped lactic acid showed burst release with complete release within 30 min. Lactic acid showed antimicrobial activity against the primary BV pathogen Gardnerella vaginalis with a minimum inhibitory concentration (MIC) of 3.6 mg/ml. In addition, the hydrogels with passively entrapped lactic acid showed retained antimicrobial activity with complete inhibition G. vaginalis growth within 48 h. The results of the current study collectively demonstrate the potential of PEG nanocarrier-based hydrogels for vaginal administration of lactic acid for preventing and treating BV.

  4. Bioactivity and cytocompatibility of dicalcium phosphate/poly (amino acid) biocomposite with degradability

    NASA Astrophysics Data System (ADS)

    Zhang, Yunfei; Shan, Wenpeng; Li, Xiangde; Wei, Jie; Li, Hong; Ma, Jian; Yan, Yonggang

    2012-01-01

    A bioactive composite of dicalcium phosphate (DCP) and poly (amino acid) (PAA) was fabricated, and the in vitro bioactivity, degradability, and cellular responses to the DCP/PAA composite (DPC) were investigated as compared to PAA. Apatite formation on DPC surfaces occurred after immersion into simulated body fluid (SBF) for 7 days, but not on the surface of PAA. The weight loss ratio of DPC could reach 18.6 ± 0.3 wt% after soaking into phosphate buffered saline (PBS) for 2 months, which was higher than PAA (11.0 ± 0.2 wt%). Cell attachment and proliferation of MG-63 cells on DPC was obviously higher than on PAA. Moreover, the cells spread and formed confluent layer on the DPC surfaces. The alkaline phosphatase activity (ALP) of the cells on DPC was significantly greater than PAA at day 5 and day 7. The results suggested that introducing DCP into PAA makes the composite bioactive and more degradable, and meanwhile enhances osteoblast-like cells attach, proliferation and osteogenic differentiation.

  5. Hyaluronic acid binding, endocytosis and degradation by sinusoidal liver endothelial cells

    SciTech Connect

    McGary, C.T.

    1988-01-01

    The binding, endocytosis, and degradation of {sup 125}I-hyaluronic acid ({sup 125}I-HA) by liver endothelial cells (LEC) was studied under several conditions. The dissociation of receptor-bound {sup 125}I-HA was rapid, with a half time of {approx}31 min and a K{sub off} of 6.3 {times} 10{sup {minus}4}/sec. A large reversible increase in {sup 125}I-HA binding to LEC at pH 5.0 was due to an increase in the observed affinity of the binding interaction. Pronase digestion suggested the protein nature of the receptor and the intracellular location of the digitonin exposed binding activity. Binding and endocytosis occur in the presence of 10 mM EGTA indicating that divalent cations are not required for receptor function. To study the degradation of {sup 125}I-HA by LEC, a cetylpyridinium chloride (CPC) precipitation assay was characterized. The minimum HA length required for precipitation was elucidated. The fate of the LEC HA receptor after endocytosis was examined.

  6. Quantifying Protein Synthesis and Degradation in Arabidopsis by Dynamic 13CO2 Labeling and Analysis of Enrichment in Individual Amino Acids in Their Free Pools and in Protein1[OPEN

    PubMed Central

    Fernie, Alisdair R.; Stitt, Mark

    2015-01-01

    Protein synthesis and degradation represent substantial costs during plant growth. To obtain a quantitative measure of the rate of protein synthesis and degradation, we supplied 13CO2 to intact Arabidopsis (Arabidopsis thaliana) Columbia-0 plants and analyzed enrichment in free amino acids and in amino acid residues in protein during a 24-h pulse and 4-d chase. While many free amino acids labeled slowly and incompletely, alanine showed a rapid rise in enrichment in the pulse and a decrease in the chase. Enrichment in free alanine was used to correct enrichment in alanine residues in protein and calculate the rate of protein synthesis. The latter was compared with the relative growth rate to estimate the rate of protein degradation. The relative growth rate was estimated from sequential determination of fresh weight, sequential images of rosette area, and labeling of glucose in the cell wall. In an 8-h photoperiod, protein synthesis and cell wall synthesis were 3-fold faster in the day than at night, protein degradation was slow (3%–4% d−1), and flux to growth and degradation resulted in a protein half-life of 3.5 d. In the starchless phosphoglucomutase mutant at night, protein synthesis was further decreased and protein degradation increased, while cell wall synthesis was totally inhibited, quantitatively accounting for the inhibition of growth in this mutant. We also investigated the rates of protein synthesis and degradation during leaf development, during growth at high temperature, and compared synthesis rates of Rubisco large and small subunits of in the light and dark. PMID:25810096

  7. Edible fungus degrade bisphenol A with no harmful effect on its fatty acid composition.

    PubMed

    Zhang, Chengdong; Li, Mingzhu; Chen, Xiaoyan; Li, Mingchun

    2015-08-01

    Bisphenol A (BPA) is an endocrine-disrupting chemical that is ubiquitous in the environment because of its broad industrial use. The authors report that the most widely cultivated mushroom in the world (i.e., white-rot fungus, Pleurotus ostreatus) efficiently degraded 10mg/L of BPA in 7 days. Extracellular laccase was identified as the enzyme responsible for this activity. LC-MS analysis of the metabolites revealed the presence of both low- and high-molecular-weight products obtained via oxidative cleavage and coupling reactions, respectively. In particular, an analysis of the fatty acid composition and chemical structure of the fungal mycelium demonstrated that exposure to BPA resulted in no harmful effects on this edible fungus. The results provide a better understanding of the environmental fate of BPA and its potential impact on food crops.

  8. Application of ethylene diamine tetra acetic acid degrading bacterium Burkholderia cepacia on biotreatment process.

    PubMed

    Chen, Wei-Ting; Shen, Shu-Min; Shu, Chi-Min

    2015-10-01

    Ethylene diamine tetra acetic acid (EDTA), the effluent of secondary biotreatment units, can be properly biodegraded by Burkholderia cepacia. Through batch degradation of EDTA, the raw wastewater of EDTA was controlled at 50 mg/L, and then nutrients was added in diluted wastewater to cultivate activated sludge, which the ratio of composition is depicted as "COD:N:P:Fe = 100:5:1:0.5". After 27 days, the removal efficiency of Fe-EDTA and COD was 100% and 92.0%, correspondingly. At the continuous process, the raw wastewater of EDTA was dictated at 166 mg/L before adding nutrients to cultivate activated sludge, in which the ratio of composition did also follow with batch process. After 22 days, the removal efficiency of Fe-EDTA and COD for experimental group was 71.46% and 62.58%, correspondingly. The results showed that the batch process was more suited for EDTA biodegradation.

  9. Strains of lactic acid bacteria isolated from sour doughs degrade phytic acid and improve calcium and magnesium solubility from whole wheat flour.

    PubMed

    Lopez, H W; Ouvry, A; Bervas, E; Guy, C; Messager, A; Demigne, C; Remesy, C

    2000-06-01

    Five strains of lactic bacteria have been isolated from sour doughs and examined for their ability to degrade phytic acid. In white flour medium in which phytic acid was the only source of phosphorus, the disappearance of phytate and an elevation of inorganic phosphate were observed after only 2 h of incubation in all strains tested (-30 and +60%, respectively). Both phenomena correspond to phytate breakdown. No difference was observed in the levels of phytic acid hydrolysis among strains, suggesting that phytase enzymes are similar among these bacteria. Using whole wheat flour medium naturally rich in phytic acid in the presence of Leuconostoc mesenteroides strain 38, a 9 h fermentation established that the degradation of PA and the production of lactic acid lead to greater Ca and Mg solubility than in control medium.

  10. Relative rates of repair of single-strand breaks and postirradiation DNA degradation in normal and induced cells of Escherichia coli.

    PubMed Central

    Pollard, E C; Fugate, J K

    1978-01-01

    Labeled DNA from irradiated Excherichia coli cells has been studied on an alkaline sucrose gradient without acid precipitation of the DNA. This enables the observation of both DNA repair and DNA degradation. The use of a predose of ultraviolet light (UV) causes induction of an inhibitor of postirradiation DNA degradation in lex+ strains. The effect of this induction on both the repair of single-strand breaks and DNA degradation has been followed in strains WU3610 (uvr+) and WU3610-89 (uvr-). The repair process is more rapid than the degradation, and when degradation is inhibited more repair is apparent. Cells that are lex- (Bs-1 and AB2474) cannot be induced for inhibition of degradation. Nevertheless, by observation at short times repair can be seen clearly. This repaired DNA is degraded, suggesting that the signal for DNA degradation is not a single-strand break. PMID:365253

  11. Comparison of ultrasonic degradation rates constants of methylene blue at 22.8 kHz, 127 kHz, and 490 kHz.

    PubMed

    Kobayashi, Daisuke; Honma, Chiemi; Suzuki, Atsushi; Takahashi, Tomoki; Matsumoto, Hideyuki; Kuroda, Chiaki; Otake, Katsuto; Shono, Atsushi

    2012-07-01

    Techniques such as solvent extraction, incineration, chemical dehalogenation, and biodegradation have been investigated for the degradation of hazardous organic compounds. We found ultrasound to be an attractive technology for the degradation of hazardous organic compounds in water. However, the effects of ultrasonic frequency on degradation rate constants were not investigated quantitatively. In this study, the degradation process of a model for hazardous organic compound methylene blue was investigated using ultrasonic irradiation. The study focused on the effects of ultrasonic frequency and ultrasonic power on the degradation rate constant. The apparent degradation rate constants were estimated based on time dependence of methylene blue concentration assuming pseudo-first-order kinetics for the decomposition. A linear relationship between the apparent degradation rate constant and ultrasonic power was identified. In addition, the apparent degradation rate constants at frequencies of 127 and 490 kHz were much larger than those at 22.8 kHz. A relationship between the apparent degradation rate constant and the sonochemical efficiency value (SE value) was also found. Based on these results, a simple model for estimating the apparent degradation rate constant of methylene blue based on the ultrasonic power and the SE value is proposed in this study.

  12. Clostridium sticklandii, a specialist in amino acid degradation:revisiting its metabolism through its genome sequence

    PubMed Central

    2010-01-01

    Background Clostridium sticklandii belongs to a cluster of non-pathogenic proteolytic clostridia which utilize amino acids as carbon and energy sources. Isolated by T.C. Stadtman in 1954, it has been generally regarded as a "gold mine" for novel biochemical reactions and is used as a model organism for studying metabolic aspects such as the Stickland reaction, coenzyme-B12- and selenium-dependent reactions of amino acids. With the goal of revisiting its carbon, nitrogen, and energy metabolism, and comparing studies with other clostridia, its genome has been sequenced and analyzed. Results C. sticklandii is one of the best biochemically studied proteolytic clostridial species. Useful additional information has been obtained from the sequencing and annotation of its genome, which is presented in this paper. Besides, experimental procedures reveal that C. sticklandii degrades amino acids in a preferential and sequential way. The organism prefers threonine, arginine, serine, cysteine, proline, and glycine, whereas glutamate, aspartate and alanine are excreted. Energy conservation is primarily obtained by substrate-level phosphorylation in fermentative pathways. The reactions catalyzed by different ferredoxin oxidoreductases and the exergonic NADH-dependent reduction of crotonyl-CoA point to a possible chemiosmotic energy conservation via the Rnf complex. C. sticklandii possesses both the F-type and V-type ATPases. The discovery of an as yet unrecognized selenoprotein in the D-proline reductase operon suggests a more detailed mechanism for NADH-dependent D-proline reduction. A rather unusual metabolic feature is the presence of genes for all the enzymes involved in two different CO2-fixation pathways: C. sticklandii harbours both the glycine synthase/glycine reductase and the Wood-Ljungdahl pathways. This unusual pathway combination has retrospectively been observed in only four other sequenced microorganisms. Conclusions Analysis of the C. sticklandii genome and

  13. Degradation in the fatigue crack growth resistance of human dentin by lactic acid.

    PubMed

    Orrego, Santiago; Xu, Huakun; Arola, Dwayne

    2017-04-01

    The oral cavity frequently undergoes localized changes in chemistry and level of acidity, which threatens the integrity of the restorative material and supporting hard tissue. The focus of this study was to evaluate the changes in fatigue crack growth resistance of dentin and toughening mechanisms caused by lactic acid exposure. Compact tension specimens of human dentin were prepared from unrestored molars and subjected to Mode I opening mode cyclic loads. Fatigue crack growth was achieved in samples from mid- and outer-coronal dentin immersed in either a lactic acid solution or neutral conditions. An additional evaluation of the influence of sealing the lumens by dental adhesive was also conducted. A hybrid analysis combining experimental results and finite element modeling quantified the contribution of the toughening mechanisms for both environments. The fatigue crack growth responses showed that exposure to lactic acid caused a significant reduction (p≤0.05) of the stress intensity threshold for cyclic crack extension, and a significant increase (p≤0.05) in the incremental fatigue crack growth rate for both regions of coronal dentin. Sealing the lumens had negligible influence on the fatigue resistance. The hybrid analysis showed that the acidic solution was most detrimental to the extrinsic toughening mechanisms, and the magnitude of crack closure stresses operating in the crack wake. Exposing dentin to acidic environments contributes to the development of caries, but it also increases the chance of tooth fractures via fatigue-related failure and at lower mastication forces.

  14. Effects of aeration rate on degradation process of oil palm empty fruit bunch with kinetic-dynamic modeling.

    PubMed

    Talib, Ahmad Tarmezee; Mokhtar, Mohd Noriznan; Baharuddin, Azhari Samsu; Sulaiman, Alawi

    2014-10-01

    The effect of different aeration rates on the organic matter (OM) degradation during the active phase of oil palm empty fruit bunch (EFB)-rabbit manure co-composting process under constant forced-aeration system has been studied. Four different aeration rates, 0.13 L min(-1) kg(DM)(-1),0.26 L min(-1) kg(DM)(-1),0.49 L min(-1) kg(DM)(-1) and 0.74 L min(-1) kg(DM)(-1) were applied. 0.26 L min(-1) kg(DM)(-1) provided enough oxygen level (10%) for the rest of composting period, showing 40.5% of OM reduction that is better than other aeration rates. A dynamic mathematical model describing OM degradation, based on the ratio between OM content and initial OM content with correction functions of moisture content, free air space, oxygen and temperature has been proposed.

  15. Structural Characterization of the Degradation Products of a Minor Natural Sweet Diterpene Glycoside Rebaudioside M under Acidic Conditions

    PubMed Central

    Prakash, Indra; Chaturvedula, Venkata Sai Prakash; Markosyan, Avetik

    2014-01-01

    Degradation of rebaudioside M, a minor sweet component of Stevia rebaudiana Bertoni, under conditions that simulated extreme pH and temperature conditions has been studied. Thus, rebaudioside M was treated with 0.1 M phosphoric acid solution (pH 2.0) and 80 °C temperature for 24 h. Experimental results indicated that rebaudioside M under low pH and higher temperature yielded three minor degradation compounds, whose structural characterization was performed on the basis of 1D (1H-, 13C-) & 2D (COSY, HSQC, HMBC) NMR, HRMS, MS/MS spectral data as well as enzymatic and acid hydrolysis studies. PMID:24424316

  16. Structural characterization of the degradation products of a minor natural sweet diterpene glycoside Rebaudioside M under acidic conditions.

    PubMed

    Prakash, Indra; Chaturvedula, Venkata Sai Prakash; Markosyan, Avetik

    2014-01-14

    Degradation of rebaudioside M, a minor sweet component of Stevia rebaudiana Bertoni, under conditions that simulated extreme pH and temperature conditions has been studied. Thus, rebaudioside M was treated with 0.1 M phosphoric acid solution (pH 2.0) and 80 °C temperature for 24 h. Experimental results indicated that rebaudioside M under low pH and higher temperature yielded three minor degradation compounds, whose structural characterization was performed on the basis of 1D (1H-, 13C-) & 2D (COSY, HSQC, HMBC) NMR, HRMS, MS/MS spectral data as well as enzymatic and acid hydrolysis studies.

  17. Photoelectrocatalytic degradation of formic acid using a porous TiO[sub 2] thin-film electrode

    SciTech Connect

    Kim, D.H.; Anderson, M.A. )

    1994-03-01

    The degradation of formic acid (HCOOH) using titanium dioxide (TiO[sub 2]) in photocatalytic and photoelectrocatalytic reactions was investigated in order to determine whether electrical biasing could improve the efficiency of photocatalytic reactions. This study addressed the effects of film thickness, biasing potential, presence of oxygen, and added inorganic electrolytes on the photocatalytic degradation of HCOOH. The results of these experiments showed that the degradation of HCOOH in this system was due only to the photocatalytic as opposed to homogeneous photolysis reactions. Degradation efficiency of the photocatalytic reaction was roughly proportional to the TiO[sub 2] film thickness. In the photoelectrocatalytic reaction, positive potentials (vs saturated calomel electrode, SCE) improved the degradation efficiency and +0.0 V (vs SCE) was enough to obtain a maximum efficiency. The supply of oxygen was essential in the photocatalytic reaction, while the photoelectrocatalytic reaction was not significantly affected by the removal of oxygen. The presence of inorganic electrolytes lowered the efficiency of the photocatalytic degradation of HCOOH. However, the efficiency of photoelectrocatalytic degradation was not affected by inorganic electrolytes. Overall, when used with the bias, the system showed efficient degradation over a wide range of conditions. 21 refs., 9 figs.

  18. Degradation of the Plant Defense Signal Salicylic Acid Protects Ralstonia solanacearum from Toxicity and Enhances Virulence on Tobacco

    PubMed Central

    Lowe-Power, Tiffany M.; Jacobs, Jonathan M.; Ailloud, Florent; Fochs, Brianna; Prior, Philippe

    2016-01-01

    ABSTRACT Plants use the signaling molecule salicylic acid (SA) to trigger defenses against diverse pathogens, including the bacterial wilt pathogen Ralstonia solanacearum. SA can also inhibit microbial growth. Most sequenced strains of the heterogeneous R. solanacearum species complex can degrade SA via gentisic acid to pyruvate and fumarate. R. solanacearum strain GMI1000 expresses this SA degradation pathway during tomato pathogenesis. Transcriptional analysis revealed that subinhibitory SA levels induced expression of the SA degradation pathway, toxin efflux pumps, and some general stress responses. Interestingly, SA treatment repressed expression of virulence factors, including the type III secretion system, suggesting that this pathogen may suppress virulence functions when stressed. A GMI1000 mutant lacking SA degradation activity was much more susceptible to SA toxicity but retained the wild-type colonization ability and virulence on tomato. This may be because SA is less important than gentisic acid in tomato defense signaling. However, another host, tobacco, responds strongly to SA. To test the hypothesis that SA degradation contributes to virulence on tobacco, we measured the effect of adding this pathway to the tobacco-pathogenic R. solanacearum strain K60, which lacks SA degradation genes. Ectopic addition of the GMI1000 SA degradation locus, including adjacent genes encoding two porins and a LysR-type transcriptional regulator, significantly increased the virulence of strain K60 on tobacco. Together, these results suggest that R. solanacearum degrades plant SA to protect itself from inhibitory levels of this compound and also to enhance its virulence on plant hosts like tobacco that use SA as a defense signal molecule. PMID:27329752

  19. Degradation of dissolved organic monomers and short-chain fatty acids in sandy marine sediment by fermentation and sulfate reduction

    NASA Astrophysics Data System (ADS)

    Valdemarsen, Thomas; Kristensen, Erik

    2010-03-01

    The decay of a wide range of organic monomers (short-chain volatile fatty acids (VFA's), amino acids, glucose and a pyrimidine) was studied in marine sediments using experimental plug flow-through reactors. The reactions were followed in the presence and absence of 10 mM SO 42-. Degradation stoichiometry of individual monomers (inflow concentration of 6 mM organic C) was traced by measuring organic (VFA's, amino acids) and inorganic (CO 2, NH 4+, SO 42-) compounds in the outflow. Fermentation of amino acids was efficient and complete during passage through anoxic sediment reactors. Aliphatic amino acids (alanine, serine and glutamate) were primarily recovered as CO 2 (24-34%), formate (3-22%) and acetate (41-83%), whereas only ˜1/3 of the aromatic amino acid (tyrosine) was recovered as CO 2 (13%) and acetate (20%). Fermentation of glucose and cytosine was also efficient (78-86%) with CO 2 (30-35%), formate (3%) and acetate (28-33%) as the primary products. Fermentation of VFA's (acetate, propionate and butyrate), on the other hand, appeared to be product inhibited. The presence of SO 42- markedly stimulated VFA degradation (29-45% efficiency), and these compounds were recovered as CO 2 (17% for butyrate to 100% for acetate) and acetate (51% and 82% for propionate and butyrate, respectively). When reaction stoichiometry during fermentation is compared with compound depletion during sulfate reduction, the higher proportion CO 2 recovery is consistent with lower acetate and formate accumulation. Our results therefore suggest that fermentation reactions mediate the initial degradation of added organic compounds, even during active sulfate reduction. Fermentative degradation stoichiometry also suggested significant H 2 production, and >50% of sulfate reduction appeared to be fuelled by H 2. Furthermore, our results suggest that fermentation was the primary deamination step during degradation of the amino acids and cytosine.

  20. Chemical evolution of RNA under hydrothermal conditions and the role of thermal copolymers of amino acids for the prebiotic degradation and formation of RNA

    NASA Technical Reports Server (NTRS)

    Kawamura, K.; Nagahama, M.; Kuranoue, K.

    2005-01-01

    The roles of thermal copolymers of amino acids (TCAA) were studied for the prebiotic degradation of RNA. A weak catalytic ability of TCAA consisted of Glu, L-Ala, L-Val, L-Glu, L-Asp, and optionally L-His was detected for the cleavage of the ribose phosphodiester bond of a tetranucleotide (5'-dCrCdGdG) in aqueous solution at 80 degees C. The rate constants of the disappearance of 5'-dCrCdGdG were determined in aqueous solutions using different pH buffer and TCAA. The degradation rates were enhanced 1.3-3.0 times in the presence of TCAA at pH 7.5 and 8.0 at 80 degrees C, while the hydrolysis of oligoguanylate (oligo(G)) was accelerated about 1.6 times at pH 8.0. A weak inhibitory activity for the cleavage of oligo(G) was detected in the presence of 0.055 M TCAA-Std. On the other hand, our recent study on the influences of TCAA for the template-directed reaction of oligo(G) on a polycytidylic acid template showed that TCAA has an acceleration activity for the degradation of the activated nucleotide monomer and an acceleration activity for the formation of G5' ppG capped oligo(G). This series of studies suggest that efficient and selective catalytic or inhibitory activities for either the degradation or formation of RNA under hydrothermal conditions could have hardly emerged from the simple thermal condensation products of amino acids. A scenario is going to be deduced on the chemical evolution of enzymatic activities and RNA molecules concerning hydrothermal earth conditions. c2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

  1. Optimal Cultivation Time for Yeast and Lactic Acid Bacteria in Fermented Milk and Effects of Fermented Soybean Meal on Rumen Degradability Using Nylon Bag Technique

    PubMed Central

    Polyorach, S.; Poungchompu, O.; Wanapat, M.; Kang, S.; Cherdthong, A.

    2016-01-01

    The objectives of this study were to determine an optimal cultivation time for populations of yeast and lactic acid bacteria (LAB) co-cultured in fermented milk and effects of soybean meal fermented milk (SBMFM) supplementation on rumen degradability in beef cattle using nylon bag technique. The study on an optimal cultivation time for yeast and LAB growth in fermented milk was determined at 0, 4, 8, 24, 48, 72, and 96 h post-cultivation. After fermenting for 4 days, an optimal cultivation time of yeast and LAB in fermented milk was selected and used for making the SBMFM product to study nylon bag technique. Two ruminal fistulated beef cattle (410±10 kg) were used to study on the effect of SBMFM supplementation (0%, 3%, and 5% of total concentrate substrate) on rumen degradability using in situ method at incubation times of 0, 2, 4, 6, 12, 24, 48, and 72 h according to a Completely randomized design. The results revealed that the highest yeast and LAB population culture in fermented milk was found at 72 h-post cultivation. From in situ study, the soluble fractions at time zero (a), potential degradability (a+b) and effective degradability of dry matter (EDDM) linearly (p<0.01) increased with the increasing supplemental levels and the highest was in the 5% SBMFM supplemented group. However, there was no effect of SBMFM supplement on insoluble degradability fractions (b) and rate of degradation (c). In conclusion, the optimal fermented time for fermented milk with yeast and LAB was at 72 h-post cultivation and supplementation of SBMFM at 5% of total concentrate substrate could improve rumen degradability of beef cattle. However, further research on effect of SBMFM on rumen ecology and production performance in meat and milk should be conducted using in vivo both digestion and feeding trials. PMID:26954119

  2. Fatty acid degradation plays an essential role in proliferation of mouse female primordial germ cells via the p53-dependent cell cycle regulation

    PubMed Central

    Teng, Hui; Sui, Xuesong; Zhou, Cheng; Shen, Cong; Yang, Ye; Zhang, Pang; Guo, Xuejiang; Huo, Ran

    2016-01-01

    ABSTRACT Primordial germ cells (PGCs) are embryonic founders of germ cells that ultimately differentiate into oocytes and spermatogonia. Embryonic proliferation of PGCs starting from E11.5 ensures the presence of germ cells in adulthood, especially in female mammals whose total number of oocytes declines after this initial proliferation period. To better understand mechanisms underlying PGC proliferation in female mice, we constructed a proteome profile of female mouse gonads at E11.5. Subsequent KEGG pathway analysis of the 3,662 proteins profiled showed significant enrichment of pathways involved in fatty acid degradation. Further, the number of PGCs found in in vitro cultured fetal gonads significantly decreased with application of etomoxir, an inhibitor of the key rate-limiting enzyme of fatty acid degradation carnitine acyltransferase I (CPT1). Decrease in PGCs was further determined to be the result of reduced proliferation rather than apoptosis. The inhibition of fatty acid degradation by etomoxir has the potential to activate the Ca2+/CamKII/5′-adenosine monophosphate-activated protein kinase (AMPK) pathway; while as an upstream activator, activated AMPK can function as activator of p53 to induce cell cycle arrest. Thus, we detected the expressional level of AMPK, phosphorylated AMPK (P-AMPK), phosphorylated p53 (P-p53) and cyclin-dependent kinase inhibitor 1 (p21) by Western blots, the results showed increased expression of them after treatment with etomoxir, suggested the activation of p53 pathway was the reason for reduced proliferation of PGCs. Finally, the involvement of p53-dependent G1 cell cycle arrest in defective proliferation of PGCs was verified by rescue experiments. Our results demonstrate that fatty acid degradation plays an important role in proliferation of female PGCs via the p53-dependent cell cycle regulation. PMID:26716399

  3. Omega-3 Polyunsaturated Fatty Acids and Heart Rate Variability

    PubMed Central

    Christensen, Jeppe Hagstrup

    2011-01-01

    Omega-3 polyunsaturated fatty acids (PUFA) may modulate autonomic control of the heart because omega-3 PUFA is abundant in the brain and other nervous tissue as well as in cardiac tissue. This might partly explain why omega-3 PUFA offer some protection against sudden cardiac death (SCD). The autonomic nervous system is involved in the pathogenesis of SCD. Heart rate variability (HRV) can be used as a non-invasive marker of cardiac autonomic control and a low HRV is a predictor for SCD and arrhythmic events. Studies on HRV and omega-3 PUFA have been performed in several populations such as patients with ischemic heart disease, patients with diabetes mellitus, patients with chronic renal failure, and in healthy subjects as well as in children. The studies have demonstrated a positive association between cellular content of omega-3 PUFA and HRV and supplementation with omega-3 PUFA seems to increase HRV which could be a possible explanation for decreased risk of arrhythmic events and SCD sometimes observed after omega-3 PUFA supplementation. However, the results are not consistent and further research is needed. PMID:22110443

  4. Nitrogen utilization in growing lambs: effects of grain (starch) and protein sources with various rates of ruminal degradation.

    PubMed

    Matras, J; Bartle, S J; Preston, R L

    1991-01-01

    The potential interaction between grain (starch) and protein sources with varying ruminal degradation rates on N utilization in growing lambs was evaluated. Three grain sources with varying ruminal degradation rates, (barley greater than steam-flaked sorghum [SFSG] greater than dry-rolled sorghum [DRSG]) and three protein sources (urea greater than a 50:25:25 mixture of urea: blood meal:corn gluten meal [N basis, U/BC] greater than 50:50 mixture of meal:corn gluten meal [N basis, BC]), were evaluated in a 3 x 3 factorial arrangement. Supplemental protein sources provided 33% of dietary N (CP = 11.0%). For each grain-protein combination, a 3 x 3 Latin square metabolism trial was conducted using two sets of three lambs and three periods. Within-square treatments were 1.4, 1.7 and 2.0 times maintenance intake levels. No interactions were observed (P greater than .2) between dietary treatments and intake level. Grain sources did not differ (P greater than .2) in N balance or the proportion of N retained. Lambs fed urea diets retained less N (3.6 vs 4.2 and 4.1 g/d for urea vs U/BC and BC, respectively; linear, P = .07; quadratic, P = .12) and utilized N less efficiently (43.1 vs 51.9 and 52.5%, respectively; linear, P less than .001; quadratic, P = .10) than lambs fed BC diets. The grain x protein interaction was significant for most variables. Nitrogen utilization was most efficient (24 to 27% of N intake retained) when rapidly degraded sources (barley and urea) and slowly degraded sources (sorghum and BC) were fed together or when U/BC was the supplemental protein source (interaction P less than .08). An advantage was found for selection of starch and protein sources with similar ruminal degradation rates.

  5. Contact Sensitizers Induce Skin Inflammation via ROS Production and Hyaluronic Acid Degradation

    PubMed Central

    Esser, Philipp R.; Wölfle, Ute; Dürr, Christoph; von Loewenich, Friederike D.; Schempp, Christoph M.; Freudenberg, Marina A.; Jakob, Thilo; Martin, Stefan F.

    2012-01-01

    Background Allergic contact dermatitis (ACD) represents a severe health problem with increasing worldwide prevalence. It is a T cell-mediated skin disease induced by protein-reactive organic and inorganic chemicals. A key feature of contact allergens is their ability to trigger an innate immune response that leads to skin inflammation. Previous evidence from the mouse contact hypersensitivity (CHS) model suggests a role for endogenous activators of innate immune signaling. Here, we analyzed the role of contact sensitizer induced ROS production and concomitant changes in hyaluronic acid metabolism on CHS responses. Methodology/Principal Findings We analyzed in vitro and in vivo ROS production using fluorescent ROS detection reagents. HA fragmentation was determined by gel electrophoresis. The influence of blocking ROS production and HA degradation by antioxidants, hyaluronidase-inhibitor or p38 MAPK inhibitor was analyzed in the murine CHS model. Here, we demonstrate that organic contact sensitizers induce production of reactive oxygen species (ROS) and a concomitant breakdown of the extracellular matrix (ECM) component hyaluronic acid (HA) to pro-inflammatory low molecular weight fragments in the skin. Importantly, inhibition of either ROS-mediated or enzymatic HA breakdown prevents sensitization as well as elicitation of CHS. Conclusions/Significance These data identify an indirect mechanism of contact sensitizer induced innate inflammatory signaling involving the breakdown of the ECM and generation of endogenous danger signals. Our findings suggest a beneficial role for anti-oxidants and hyaluronidase inhibitors in prevention and treatment of ACD. PMID:22848468

  6. Chemometric study on the TiO2-photocatalytic degradation of nitrilotriacetic acid.

    PubMed

    Emilio, Carina A; Magallanes, Jorge F; Litter, Marta I

    2007-07-09

    A chemometric study on the TiO2-photocatalytic degradation of nitrilotriacetic acid (NTA) in aqueous media under UV radiation has been carried out taking into account the multiple variables that take part in the system. To save redundant number of experiments, the system has been managed under chemometric techniques for several variables as NTA and TiO2 concentrations, pH and irradiation time. Multiple-way analysis of the variance (MANOVA) has been applied to find the statistically significant variables. An artificial neural network (ANN) has been used to build an empirical model of the system. All measurements have been driven under experimental designs: a full-factorial design (FFD) was used to analyze significant factors through MANOVA, and a Doehlert design, which was modified by spatial rotation, was applied in order to have a satisfactory number of levels for the factor time to be able to train the ANN. The study allows the knowledge and prediction of the behavior of the system as well as to work out kinetic parameters and to optimize their variables. The results of kinetic parameters obtained with the neural network agreed with independent experimental results, confirming a Langmuir-Hinshelwood kinetic regime. The difference between NTA and ethylenediaminetetraacetic acid (EDTA), which has been previously studied, is also established.

  7. The effects of cutting or of stretching skeletal muscle in vitro on the rates of protein synthesis and degradation

    NASA Technical Reports Server (NTRS)

    Seider, M. J.; Kapp, R.; Chen, C.-P.; Booth, F. W.

    1980-01-01

    Skeletal muscle preparations using cut muscle fibers have often been used in studies of protein metabolism. The present paper reports an investigation of the effect of muscle cutting or stretching in vitro on the rates of protein synthesis and/or degradation. Protein synthesis and content, and ATP and phosphocreatine levels were monitored in soleus and extensor digitorum longus muscles from the rat with various extents of muscle fiber cuts and following stretching to about 120% the resting length. Rates of protein synthesis are found to be significantly lower and protein degradation higher in the cut muscles than in uncut controls, while ATP and phosphocreatine concentrations decreased. Stretched intact muscles, on the other hand, are observed to have higher concentrations of high-energy phosphates than unstretched muscles, while rates of protein degradation were not affected. Results thus demonstrate that the cutting of skeletal muscle fibers alters many aspects of muscle metabolism, and that moderate decreases in ATP concentration do not alter rates of protein concentration in intact muscles in vitro.

  8. Exploring the mechanical behavior of degrading swine neural tissue at low strain rates via the fractional Zener constitutive model.

    PubMed

    Bentil, Sarah A; Dupaix, Rebecca B

    2014-02-01

    The ability of the fractional Zener constitutive model to predict the behavior of postmortem swine brain tissue was examined in this work. Understanding tissue behavior attributed to degradation is invaluable in many fields such as the forensic sciences or cases where only cadaveric tissue is available. To understand how material properties change with postmortem age, the fractional Zener model was considered as it includes parameters to describe brain stiffness and also the parameter α, which quantifies the viscoelasticity of a material. The relationship between the viscoelasticity described by α and tissue degradation was examined by fitting the model to data collected in a previous study (Bentil, 2013). This previous study subjected swine neural tissue to in vitro unconfined compression tests using four postmortem age groups (<6h, 24h, 3 days, and 1 week). All samples were compressed to a strain level of 10% using two compressive rates: 1mm/min and 5mm/min. Statistical analysis was used as a tool to study the influence of the fractional Zener constants on factors such as tissue degradation and compressive rate. Application of the fractional Zener constitutive model to the experimental data showed that swine neural tissue becomes less stiff with increased postmortem age. The fractional Zener model was also able to capture the nonlinear viscoelastic features of the brain tissue at low strain rates. The results showed that the parameter α was better correlated with compressive rate than with postmortem age.

  9. Clostridium thermocellum releases coumaric acid during degradation of untreated grasses by the action of an unknown enzyme.

    PubMed

    Herring, Christopher D; Thorne, Philip G; Lynd, Lee R

    2016-03-01

    Clostridium thermocellum is an anaerobic thermophile with the ability to digest lignocellulosic biomass that has not been pretreated with high temperatures. Thermophilic anaerobes have previously been shown to more readily degrade grasses than wood. Part of the explanation for this may be the presence of relatively large amounts of coumaric acid in grasses, with linkages to both hemicellulose and lignin. We found that C. thermocellum and cell-free cellulase preparations both release coumaric acid from bagasse and switchgrass. Cellulase preparations from a mutant strain lacking the scaffoldin cipA still showed activity, though diminished. Deletion of all three proteins in C. thermocellum with ferulic acid esterase domains, either singly or in combination, did not eliminate the activity. Further work will be needed to identify the novel enzyme(s) responsible for the release of coumaric acid from grasses and to determine whether these enzymes are important factors of microbial biomass degradation.

  10. Sequential photochemical and microbial degradation of organic molecules bound to humic acid

    SciTech Connect

    Amador, J.A.; Zika, R.G. ); Alexander, M. )

    1989-11-01

    We studied the effects of photochemical processes on the mineralization by soil microorganisms of (2-{sup 14}C)glycine bound to soil humic acid. Microbial mineralization of these complexes in the dark increased inversely with the molecular weight of the complex molecules. Sunlight irradiation of glycine-humic acid complexes resulted in loss of absorbance in the UV range and an increase in the amount of {sup 14}C-labeled low-molecular-weight photoproducts and the rate and extent of mineralization. More than half of the radioactivity in the low-molecular-weight photoproducts appears to be associated with carboxylic acids. Microbial mineralization of the organic carbon increased with solar flux and was proportional to the loss of A{sub 330}. Mineralization was proportional to the percentage of the original complex that was converted to low-molecular-weight photoproducts. Only light at wavelengths below 380 nm had an effect on the molecular weight distribution of the products formed from the glycine-humic acid complexes and on the subsequent microbial mineralization. Our results indicate that photochemical processes generate low-molecular-weight, readily biodegradable molecules from high-molecular-weight complexes of glycine with humic acid.

  11. Developing an in vitro method for determining feed soluble protein degradation rate by mixed ruminal microorganisms

    Technology Transfer Automated Retrieval System (TEKTRAN)

    For the purposes of ration balancing using predictive computer models, more accurate content and rumen soluble protein degradability values are needed, especially for highly processed feeds. Consequently, a standardized method of determination is needed. Hence, a novel ruminal in vitro method is d...

  12. Metabolic rates associated with membrane fatty acids in mice selected for increased maximal metabolic rate

    PubMed Central

    Wone, Bernard W. M.; Donovan, Edward R.; Cushman, John C.; Hayes, Jack P.

    2014-01-01

    Aerobic metabolism of vertebrates is linked to membrane fatty acid (FA) composition. Although the membrane pacemaker hypothesis posits that desaturation of FAs accounts for variation in resting or basal metabolic rate (BMR), little is known about the FA profiles that underpin variation in maximal metabolic rate (MMR). We examined membrane FA composition of liver and skeletal muscle in mice after seven generations of selection for increased MMR. In both liver and skeletal muscle, unsaturation index did not differ between control and high-MMR mice. We also examined membrane FA composition at the individual-level of variation. In liver, 18:0, 20:3 n-6, 20:4 n-6, and 22:6 n-3 FAs were significant predictors of MMR. In gastrocnemius muscle, 18:2 n-6, 20:4 n-6, and 22:6 n-3 FAs were significant predictors of MMR. In addition, muscle 16:1 n-7, 18:1 n-9, and 22:5 n-3 FAs were significant predictors of BMR, whereas no liver FAs were significant predictors of BMR. Our findings indicate that (i) individual variation in MMR and BMR appear to be linked to membrane FA composition in the skeletal muscle and liver, and (ii) FAs that differ between selected and control lines are involved in pathways that can affect MMR or BMR. PMID:23422919

  13. Production and partial characterization of uric acid degrading enzyme from new source Saccharopolyspora sp. PNR11.

    PubMed

    Khucharoenphaisan, K; Sinma, K

    2011-02-01

    The strain PNR11 was isolated from gut of termite during the screening for uric acid degrading actinomyces. This strain was able to produce an intracellular uricase when cultured in fermentation medium containing uric acid as nitrogen source. Base on its morphological characters and 16S rDNA sequence analysis, this strain belong to the genus Saccharopolyspora. This is the first report ofuricase produced from the genus Saccharopolyspora. The aim of this study was to investigate the effects of different factors on uricase production by new source of Saccharopolyspora. Saccharopolyspora sp. PNR11 was cultured in production medium in order to determine the best cultivation period. The result showed that the time period required for maximum enzyme production was 24 h on a rotary shaker operating at 180 rpm. Optimized composition of the production medium consisted of 1% yeast extract, 1% maltose, 0.1% K2HPO4, 0.05% MgSO4 7H2O, 0.05% NaCl and 1% uric acid. The optimum pH and temperature for uricase production in the optimized medium were pH 7.0 and 30 degrees C, respectively. When the strain was cultured at optimized condition, the uricase activity reached to 216 mU mL(-1) in confidential level of 95%. The crude enzyme had an optimum temperature of uricase was 37 degrees C and it was stable up to 30 degrees C at pH 8.5. The optimum pH ofuricase was 8.5 and was stable in range of pH 7.0-10.0 at 4 degrees C. This strain might be considered as a candidate source for uricase production in the further studies. Present finding could be fulfill the information ofuricase produce from actinomycetes.

  14. Degradation of acid red 97 dye in aqueous medium using wet oxidation and electro-Fenton techniques.

    PubMed

    Kayan, Berkant; Gözmen, Belgin; Demirel, Muhammet; Gizir, A Murat

    2010-05-15

    Degradation of the acid red 97 dye using wet oxidation, by different oxidants, and electro-Fenton systems was investigated in this study. The oxidation effect of different oxidants such as molecular oxygen, periodate, persulfate, bromate, and hydrogen peroxide in wet oxidation system was compared. Mineralization of AR97 with periodate appeared more effective when compared with that of the other oxidants at equal initial concentration. When 5 mM of periodate was used, at the first minute of the oxidative treatment, the decolorization percentage of AR97 solution at 150 and 200 degrees C reached 88 and 98%, respectively. The total organic carbon removal efficiency at these temperatures also reached 60 and 80%. The degradation of AR97 was also studied by electro-Fenton process. The optimal current value and Fe(2+) concentration were found to be 300 mA and 0.2 mM, respectively. The results showed that electro-Fenton process can lead to 70 and 95% mineralization of the dye solution after 3 and 5h giving carboxylic acids and inorganic ions as final end-products before mineralization. The products obtained from degradation were identified by GC/MS as 1,2-naphthalenediol, 1,1'-biphenyl-4-amino-4-ol, 2-naphthalenol diazonium, 2-naphthalenol, 2,3-dihydroxy-1,4-naphthalenedion, phthalic anhydride, 1,2-benzenedicarboxylic acid, phthaldehyde, 3-hydroxy-1,2-benzenedicarboxylic acid, 4-amino-benzoic acid, and 2-formyl-benzoic acid.

  15. The oxidative degradation of barley β-glucan in the presence of ascorbic acid or hydrogen peroxide.

    PubMed

    Mäkelä, Noora; Sontag-Strohm, Tuula; Maina, Ndegwa Henry

    2015-06-05

    Cereal β-glucans are polysaccharides with health benefits that have been linked to their ability to increase luminal viscosity. However, the functional properties of cereal β-glucans may be diminished by the susceptibility of this polysaccharide to oxidative degradation. In this study, barley β-glucan was oxidised with hydrogen peroxide or ascorbic acid and the oxidative degradation of β-glucan was investigated using both asymmetrical flow field-flow fractionation (AsFlFFF) with aqueous solvent and high performance size exclusion chromatography (HPSEC) with LiBr in DMSO as the solvent. Oxidation was shown to cause degradation of β-glucan, the reaction being faster when oxidised with hydrogen peroxide compared with ascorbic acid. Both HPSEC and AsFlFFF showed comparable results as long as aggregates (only observed in AsFlFFF) were not included in the integration. The compact aggregates observed in oxidised samples suggest oxidation driven interactions between β-glucan molecules.

  16. The effect of degradation on κ-carrageenan/locust bean gum/konjac glucomannan gels at acidic pH.

    PubMed

    Yang, Kun; Wang, Zheng; Nakajima, Tetsuya; Nishinari, Katsuyoshi; Brenner, Tom

    2013-10-15

    The feasibility of textural and rheological modification of gels containing κ-carrageenan (KC) and locust bean gum (LBG) by addition of konjac glucomannan (KGM) was investigated. Special attention was paid to the effect of polysaccharide degradation during heating at acidic pH. The general effect of polysaccharide degradation was to decrease the Young's modulus, while the fracture strain in extension was scarcely affected unless the degradation was very severe. Differential scanning calorimetry showed that the melting peak corresponding to dissociation of KC-KGM bonds decreased faster than the melting peak of KC-only bonds with increasing degree of polysaccharide degradation. The implication is that as degradation proceeds, fewer KGM molecules can interact with KC to form elastic bonds, and the excess of KGM which reinforces the existing elastic network and increases the fracture strain actually increases. For this reason, the fracture strain remains nearly unchanged with increasing degradation levels. A decrease in fracture strain is thus observed only at very severe degradations, where KC no longer forms a self-supporting gel by itself.

  17. Characterization of lignocellulosic compositions' degradation during chicken manure composting with added biochar by phospholipid fatty acid (PLFA) and correlation analysis.

    PubMed

    Liu, Ning; Zhou, Jialiang; Han, Lujia; Huang, Guangqun

    2017-05-15

    Biorefractory high polymer lignocellulosic compositions may limit rapid composting and stable decomposition. Because their degradation during composting is not well understood, the correlation with microbial community profiles was assessed to reveal degradation mechanism of lignocellulosic compositions. Testing of chicken manure aerobic composting with added biochar was performed using phospholipid fatty acid (PLFA) and correlation analysis. Results demonstrated a good composting effect with good dynamic correlation between microbial characteristic (PLFA) and lignocellulosic compositions' degradation ratio. The prediction model for hemicellulose degradation ratio (R(2)=0.97, SEP=3.24) and the prediction model for cellulose degradation ratio (R(3)=0.94, SEP=3.09), built using PLFA 16:0-18:2ω6c and PLFA 18:2ω6c-18:3ω3 as the arguments had good predictive ability. Based on microbial analysis and quantitative characterization of the degradation ratio, the prediction models provided methodological support for delineating the mechanism of lignocellulosic compositions' degradation during chicken manure aerobic composting with added biochar.

  18. In-vitro degradation characteristics of poly(e-caprolactone)/poly(glycolic acid) scaffolds fabricated via solid-state cryomilling.

    PubMed

    Jonnalagadda, John B; Rivero, Iris V; Warzywoda, Juliusz

    2015-10-01

    Poly(e-caprolactone) (PCL)/poly(glycolic acid) (PGA) scaffolds were fabricated via solid-state cryomilling along with compression molding and porogen leaching techniques. Four types of scaffolds were produced using four distinct cryomilling times. These scaffolds were evaluated for their in-vitro degradation behavior hydrolytically in phosphate buffer saline (PBS). The degradation profiles were investigated over a period of 60 days. The percentage of weight loss, percentage of water absorption, morphology, compressive, thermal, and material properties were studied as a function of degradation time. Weight loss and water absorption demonstrated a high correlation, which showed an increasing behavior with increase in cryomilling time and degradation time. Morphology of the scaffolds analyzed through scanning electron microscopy (SEM) revealed micro-cracks on the surface of the cylindrical struts due to hydrolytic attack and dissolution of hydrophilic PGA. Changes in compressive modulus and crystallinity over the degradation period and material properties were analyzed using X-ray powder diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy. DSC and XRD results indicated that hydrolytic attack had taken place during degradation, resulting in moments of increased and decreased percent crystallinity. This study successfully brought forth the differences in resultant properties of the PCL/PGA scaffolds as a function of degradation time.

  19. Role of nickel in high rate methanol degradation in anaerobic granular sludge bioreactors

    PubMed Central

    Fermoso, Fernando G.; Collins, Gavin; Bartacek, Jan; O’Flaherty, Vincent

    2008-01-01

    The effect of nickel deprivation from the influent of a mesophilic (30°C) methanol fed upflow anaerobic sludge bed (UASB) reactor was investigated by coupling the reactor performance to the evolution of the Methanosarcina population of the bioreactor sludge. The reactor was operated at pH 7.0 and an organic loading rate (OLR) of 5–15 g COD l−1 day−1 for 191 days. A clear limitation of the specific methanogenic activity (SMA) on methanol due to the absence of nickel was observed after 129 days of bioreactor operation: the SMA of the sludge in medium with the complete trace metal solution except nickel amounted to 1.164 (±0.167) g CH4-COD g VSS−1 day−1 compared to 2.027 (±0.111) g CH4-COD g VSS−1 day−1 in a medium with the complete (including nickel) trace metal solution. The methanol removal efficiency during these 129 days was 99%, no volatile fatty acid (VFA) accumulation was observed and the size of the Methanosarcina population increased compared to the seed sludge. Continuation of the UASB reactor operation with the nickel limited sludge lead to incomplete methanol removal, and thus methanol accumulation in the reactor effluent from day 142 onwards. This methanol accumulation subsequently induced an increase of the acetogenic activity in the UASB reactor on day 160. On day 165, 77% of the methanol fed to the system was converted to acetate and the Methanosarcina population size had substantially decreased. Inclusion of 0.5 μM Ni (dosed as NiCl2) to the influent from day 165 onwards lead to the recovery of the methanol removal efficiency to 99% without VFA accumulation within 2 days of bioreactor operation. PMID:18247139

  20. Degradation of Poly(L-Lactic Acid) and Bio-Composites by Alkaline Medium under Various Temperatures

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ribbons of poly(lactic acid) (PLA) and PLA containing 10 or 25 % Osage orange (OO) biocomposites of various sized heartwood particles were exposed to non-composting soil conditions either outdoors or in a greenhouse. No appreciable degradation was evident even after 208 day treatments. An artifici...

  1. Thermal properties of extruded injection-molded poly (lactic acid) and milkweed composites: degradation kinetics and enthalpic relaxation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Currently, most polymer composites utilize petroleum-based materials that are non-degradable and difficult to recycle or incur substantial cost for disposal. Green composites can be used in nondurable limited applications. In order to determine the degree of compatibility between Poly (lactic Acid...

  2. Interactions among triphenyltin degradation, phospholipid synthesis and membrane characteristics of Bacillus thuringiensis in the presence of d-malic acid.

    PubMed

    Wang, Linlin; Yi, Wenying; Ye, Jinshao; Qin, Huaming; Long, Yan; Yang, Meng; Li, Qusheng

    2017-02-01

    Degradation pathway and surface biosorption of triphenyltin (TPT) by effective microbes have been investigated in the past. However, unclear interactions among membrane components and TPT binding and transport are still obstacles to understanding TPT biotransformation. To reveal the mechanism involved, the phospholipid expression, membrane potential, cellular mechanism and molecular dynamics between TPT and fatty acids (FAs) during the TPT degradation process in the presence of d-malic acid (DMA) were studied. The results show that the degradation efficiency of 1 mg L(-1) TPT by Bacillus thuringiensis (1 g L(-1)) with 0.5 or 1 mg L(-1) DMA reached values up to approximately 90% due to the promotion of element metabolism and cellular activity, and the depression of FA synthesis induced by DMA. The addition of DMA caused conversion of more linoleic acid into 10-oxo-12(Z)-octadecenoic acid, increased the membrane permeability, and alleviated the decrease in membrane potential, resulting in TPT transport and degradation. Fluorescence analysis reveals that the endospore of B. thuringiensis could act as an indicator for membrane potential and cellular activities. The current findings are advantageous for acceleration of biosorption, transport and removal of pollutants from natural environments.

  3. Characterisation of hexane-degrading microorganisms in a biofilter by stable isotope-based fatty acid analysis, FISH and cultivation.

    PubMed

    Friedrich, Michèle M; Lipski, André

    2010-01-01

    The hexane-degrading bacterial community of a biofilter was characterised by a combination of stable isotope-based phospholipid fatty acid analyses, fluorescence in situ hybridisation and cultivation. About 70 bacterial strains were isolated from a full-scale biofilter used for treatment of hexane containing waste gas of an oil mill. The isolation approach led to 16 bacterial groups, which were identified as members of the Alpha-, Beta- and Gammaproteobacteria, Actinobacteria and Firmicutes. Three groups showed good growth on hexane as the sole source of carbon. These groups were allocated to the genera Gordonia and Sphingomonas and to the Nevskia-branch of the Gammaproteobacteria. Actively degrading populations in the filter material were characterised by incubation of filter material samples with deuterated hexane and subsequent phospholipid fatty acid analysis. Significant labelling of the fatty acids 16:1 cis10, 18:1 cis9 and 18:0 10methyl affiliated the hexane-degrading activity of the biofilter with the isolates of the genus Gordonia. In vitro growth on hexane and in situ labelling of characteristic fatty acids confirmed the central role of these organisms in the hexane degradation within the full-scale biofilter.

  4. Degradation of oxalic acid by the mycoparasite Coniothyrium minitans plays an important role in interacting with Sclerotinia sclerotiorum

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Coniothyrium minitans is a mycoparasite of the phytopathogenic fungus Sclerotinia sclerotiorum. Sclerotinia sclerotiorum produces a virulence factor oxalic acid (OA) which is toxic to plants and also to C. minitans, and C. minitans detoxifies OA by degradation. In this study, two oxalate decarboxyla...

  5. Naphthenic acids degradation and toxicity mitigation in tailings wastewater systems and aquatic environments: a review.

    PubMed

    Kannel, Prakash R; Gan, Thian Y

    2012-01-01

    Naphthenic acids, NAs (classical formula C(n)H(2n+z)O(2), where n is the carbon numbers, z represents zero or negative even integers), found in oil sands process waters (OSPWs), are toxic to aquatic environments depending upon several factors such as pH, salinity, molecular size and chemical structure of NAs. Among various available methods, biodegradation seems to be generally the most cost-effective method for decreasing concentrations of NAs (n ≤ 21) and reducing their associated toxicity in OSPW, however the mechanism by which the biodegradation of NAs occurs are poorly understood. Ozonation is superior over biodegradation in decreasing higher molecular weight alkyl branched NAs (preferentially, n ≥ 22, -6 ≥ z ≥ -12) as well as enabling accelerated biodegradation and reducing toxicity. Photolysis (UV at 254 nm) is effective in cleaving higher molecular weight NAs into smaller fragments that will be easier for microorganisms to degrade, whereas photocatalysis can metabolize selective NAs (0 ≥ z ≥ -6) efficiently and minimize their associated toxicity. Phytoremediation is applicable for metabolizing specific NAs (O(2), O(3), O(4), and O(5) species) and minimizing their associated toxicities. Petroleum coke (PC) adsorption is effective in reducing the more structurally complex NAs (preferentially 12 ≥ n ≥ 18 and z = -10, -12) and their toxicity in OSPWs, depending upon the PC content, pH and temperature. Several factors have influence on the degradation of NAs in OSPWs and aquatic environments, which include molecular mass and chemical structure of NAs, sediment structure, temperature, pH, dissolved oxygen, nutrients, and bacteria types.

  6. Excretion pathways and ruminal disappearance of glyphosate and its degradation product aminomethylphosphonic acid in dairy cows.

    PubMed

    von Soosten, D; Meyer, U; Hüther, L; Dänicke, S; Lahrssen-Wiederholt, M; Schafft, H; Spolders, M; Breves, G

    2016-07-01

    From 6 balance experiments with total collection of feces and urine, samples were obtained to investigate the excretion pathways of glyphosate (GLY) in lactating dairy cows. Each experiment lasted for 26d. The first 21d served for adaptation to the diet, and during the remaining 5d collection of total feces and urine was conducted. Dry matter intake and milk yield were recorded daily and milk and feed samples were taken during the sampling periods. In 2 of the 6 experiments, at the sampling period for feces and urine, duodenal contents were collected for 5d. Cows were equipped with cannulas at the dorsal sac of the rumen and the proximal duodenum. Duodenal contents were collected every 2h over 5 consecutive days. The daily duodenal dry matter flow was measured by using chromium oxide as a volume marker. All samples (feed, feces, urine, milk and duodenal contents were analyzed for GLY and aminomethylphosphonic acid (AMPA). Overall, across the 6 experiments (n=32) the range of GLY intake was 0.08 to 6.67mg/d. The main proportion (61±11%; ±SD) of consumed GLY was excreted with feces; whereas excretion by urine was 8±3% of GLY intake. Elimination via milk was negligible. The GLY concentrations above the limit of quantification were not detected in any of the milk samples. A potential ruminal degradation of GLY to AMPA was derived from daily duodenal GLY flow. The apparent ruminal disappearance of GLY intake was 36 and 6%. In conclusion, the results of the present study indicate that the gastrointestinal absorption of GLY is of minor importance and fecal excretion represents the major excretion pathway. A degradation of GLY to AMPA by rumen microbes or a possible retention in the body has to be taken into account.

  7. Degradation of atrazine and 2, 4-dichlorophenoxyacetic acid by mycorrhizal fungi at three nitrogen concentrations in vitro

    SciTech Connect

    Donnelly, P.K.; Crawford, D.L. ); Entry, J.A. )

    1993-08-01

    Atrazine is a chlorinated aromatic hydrocarbon with an extremely low rated of degradation, especially in cold, dry climates. Biodegradation of the herbicide 2,4-D is known to occur in warm, moist soil, but it is dependent on environmental conditions and soil characteristics. This study examines the biodegradation of Atrazine and 2,4-D under various physiological conditions. Both mycorrhizal and nonmycorrhizal fungi were used. Phanerochaete chrysosporium was the best 2,4-D-degrading organism, but it was not able to mineralize atrazine. The ericoid mycorrhizal fungi degraded atrazine most effectively. 28 refs., 4 tabs.

  8. Earthworms (Eisenia fetida) demonstrate potential for use in soil bioremediation by increasing the degradation rates of heavy crude oil hydrocarbons.

    PubMed

    Martinkosky, Luke; Barkley, Jaimie; Sabadell, Gabriel; Gough, Heidi; Davidson, Seana

    2017-02-15

    Crude oil contamination widely impacts soil as a result of release during oil and gas exploration and production activities. The success of bioremediation methods to meet remediation goals often depends on the composition of the crude oil, the soil, and microbial community. Earthworms may enhance bioremediation by mixing and aerating the soil, and exposing soil microorganisms to conditions in the earthworm gut that lead to increased activity. In this study, the common composting earthworm Eisenia fetida was tested for utility to improve remediation of oil-impacted soil. E. fetida survival in soil contaminated with two distinct crude oils was tested in an artificial (lab-mixed) sandy loam soil, and survival compared to that in the clean soil. Crude oil with a high fraction of light-weight hydrocarbons was more toxic to earthworms than the crude oil with a high proportion of heavy polyaromatic and aliphatic hydrocarbons. The heavier crude oil was added to soil to create a 30,000mg/kg crude oil impacted soil, and degradation in the presence of added earthworms and feed, feed alone, or no additions was monitored over time and compared. Earthworm feed was spread on top to test effectiveness of no mixing. TPH degradation rate for the earthworm treatments was ~90mg/day slowing by 200days to ~20mg/day, producing two phases of degradation. With feed alone, the rate was ~40mg/day, with signs of slowing after 500days. Both treatments reached the same end point concentrations, and exhibited faster degradation of aliphatic hydrocarbons C21, decreased. During these experiments, soils were moderately toxic during the first three months, then earthworms survived well, were active and reproduced with petroleum hydrocarbons present. This study demonstrated that earthworms accelerate bioremediation of crude oil in soils, including the degradation of the heaviest polyaromatic fractions.

  9. Τhe effect of silica nanoparticles on the thermomechanical properties and degradation behavior of polylactic acid.

    PubMed

    Georgiopoulos, P; Kontou, E; Meristoudi, A; Pispas, S; Chatzinikolaidou, M

    2014-11-01

    In this work a series of polylactic acid/SiO2 nanocomposites have been prepared by a melt mixing procedure. The dispersion quality was examined by scanning electron microscopy. To study the degradation behavior of the polylactic acid/nanocomposites prepared, the samples were immersed in a buffer solution at a temperature of 37℃ with a pH of 7.4 for a time period of up to 23 weeks. These conditions simulate those in the human body, appropriate in medical applications. In order to assess their suitability in biomedical applications, we investigated the biocompatibility of these materials in terms of cell viability, growth, and morphology. A good initial cell adhesion has been detected, supporting their potential use in bone tissue engineering applications. The hydrolytic degradation of polylactic acid, under the prescribed conditions, was studied by the molecular weight reduction in terms of size exclusion chromatography, whereas the progress of thermal stability of polylactic acid and polylactic acid/nanocomposites during aging was tested by thermogravimetric analysis. The evolution of the materials' thermomechanical properties during aging was studied by differential scanning calorimetry, dynamic mechanical analysis, and tensile testing. The crystallization behavior in polylactic acid and the way it is affected by the presence of nanofillers during degradation procedure has been studied and values of 44% crystallinity increment have been found. At the specific aging conditions studied, silica nanoparticles accelerate the degradability of polylactic acid, having a higher impact on Young's modulus, under the specified aging conditions, for 7 weeks and hereafter this acceleration is retarded, due to the crystallinity increment, as a result of the molecular weight reduction.

  10. Low Phytic Acid Barley Responses to Phosphorus Rates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Low phytic acid (LPA) barley (Hordeum vulgare L.) cultivars partition phosphorus in seed tissue differently than conventional barley cultivars through a reduction in seed phytic acid (myo-inositol-1,2,3,4,5,6-hexkisphosphate) coupled with an increase in inorganic phosphorus. The response of the LPA...

  11. Silicate, borosilicate, and borate bioactive glass scaffolds with controllable degradation rate for bone tissue engineering applications. I. Preparation and in vitro degradation.

    PubMed

    Fu, Qiang; Rahaman, Mohamed N; Fu, Hailuo; Liu, Xin

    2010-10-01

    Bioactive glass scaffolds with a microstructure similar to that of dry human trabecular bone but with three different compositions were evaluated for potential applications in bone repair. The preparation of the scaffolds and the effect of the glass composition on the degradation and conversion of the scaffolds to a hydroxyapatite (HA)-type material in a simulated body fluid (SBF) are reported here (Part I). The in vitro response of osteogenic cells to the scaffolds and the in vivo evaluation of the scaffolds in a rat subcutaneous implantation model are described in Part II. Scaffolds (porosity = 78-82%; pore size = 100-500 microm) were prepared using a polymer foam replication technique. The glasses consisted of a silicate (13-93) composition, a borosilicate composition (designated 13-93B1), and a borate composition (13-93B3), in which one-third or all of the SiO2 content of 13-93 was replaced by B2O3, respectively. The conversion rate of the scaffolds to HA in the SBF increased markedly with the B2O3 content of the glass. Concurrently, the pH of the SBF also increased with the B2O3 content of the scaffolds. The compressive strengths of the as-prepared scaffolds (5-11 MPa) were in the upper range of values reported for trabecular bone, but they decreased markedly with immersion time in the SBF and with increasing B2O3 content of the glass. The results show that scaffolds with a wide range of bioactivity and degradation rate can be achieved by replacing varying amounts of SiO(2) in silicate bioactive glass with B2O3.

  12. Carbofuran removal in continuous-photocatalytic reactor: Reactor optimization, rate-constant determination and carbofuran degradation pathway analysis.

    PubMed

    Vishnuganth, M A; Remya, Neelancherry; Kumar, Mathava; Selvaraju, N

    2017-02-22

    Carbofuran (CBF) removal in a continuous-flow photocatalytic reactor with granular activated carbon supported titanium dioxide (GAC-TiO2) catalyst was investigated. The effects of feed flow rate, TiO2 concentration and addition of supplementary oxidants on CBF removal were investigated. The central composite design (CCD) was used to design the experiments and to estimate the effects of feed flow rate and TiO2 concentration on CBF removal. The outcome of CCD experiments demonstrated that reactor performance was influenced mainly by feed flow rate compared to TiO2 concentration. A second-order polynomial model developed based on CCD experiments fitted the experimental data with good correlation (R(2) ∼ 0.964). The addition of 1 mL min(-1) hydrogen peroxide has shown complete CBF degradation and 76% chemical oxygen demand removal under the following operating conditions of CBF ∼50 mg L(-1), TiO2 ∼5 mg L(-1) and feed flow rate ∼82.5 mL min(-1). Rate constant of the photodegradation process was also calculated by applying the kinetic data in pseudo-first-order kinetics. Four major degradation intermediates of CBF were identified using GC-MS analysis. As a whole, the reactor system and GAC-TiO2 catalyst used could be constructive in cost-effective CBF removal with no impact to receiving environment through getaway of photocatalyst.

  13. Degradation of oxalic acid by the mycoparasite Coniothyrium minitans plays an important role in interacting with Sclerotinia sclerotiorum.

    PubMed

    Zeng, Li-Mei; Zhang, Jing; Han, Yong-Chao; Yang, Long; Wu, Ming-de; Jiang, Dao-Hong; Chen, Weidong; Li, Guo-Qing

    2014-08-01

    Coniothyrium minitans (Cm) is a mycoparasite of the phytopathogenic fungus Sclerotinia sclerotiorum (Ss). Ss produces a virulence factor oxalic acid (OA) which is toxic to plants and also to Cm, and Cm detoxifies OA by degradation. In this study, two oxalate decarboxylase genes, Cmoxdc1 and Cmoxdc2, were cloned from Cm strain Chy-1. OA and low pH induced expression of Cmoxdc1, but not Cmoxdc2. Cmoxdc1 was partially responsible for OA degradation, whereas Cmoxdc2 had no effect on OA degradation. Disruption of Cmoxdc1 in Cm reduced its ability to infect Ss in dual cultures where OA accumulated. Compared with Chy-1, the Cmoxdc1-disrupted mutants had reduced expression levels of two mycoparasitism-related genes chitinase (Cmch1) and β-1,3-glucanase (Cmg1), and had no detectable activity of extracellular proteases in the presence of OA. On the other hand, the cultural filtrates of the Cmoxdc1-disrupted mutants in OA-amended media showed enhanced antifungal activity, possibly because of increased production of antifungal substances under acidic pH condition resulted from reduced Cmoxdc1-mediated OA degradation. This study provides direct genetic evidence of OA degradation regulating mycoparasitism and antibiosis of Cm against Ss, and sheds light on the sophisticated strategies of Cm in interacting with metabolically active mycelia and dormant sclerotia of Ss.

  14. Structural insights into 2,2'-azino-Bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)-mediated degradation of reactive blue 21 by engineered Cyathus bulleri Laccase and characterization of degradation products.

    PubMed

    Kenzom, T; Srivastava, P; Mishra, S

    2014-12-01

    Advanced oxidation processes are currently used for the treatment of different reactive dyes which involve use of toxic catalysts. Peroxidases are reported to be effective on such dyes and require hydrogen peroxide and/or metal ions. Cyathus bulleri laccase, expressed in Pichia pastoris, catalyzes efficient degradation (78 to 85%) of reactive azo dyes (reactive black 5, reactive orange 16, and reactive red 198) in the presence of synthetic mediator ABTS [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)]. This laccase was engineered to degrade effectively reactive blue 21 (RB21), a phthalocyanine dye reported to be decolorized only by peroxidases. The 816-bp segment (toward the C terminus) of the lcc gene was subjected to random mutagenesis and enzyme variants (Lcc35, Lcc61, and Lcc62) were selected based on increased ABTS oxidizing ability. Around 78 to 95% decolorization of RB21 was observed with the ABTS-supplemented Lcc variants in 30 min. Analysis of the degradation products by mass spectrometry indicated the formation of several low-molecular-weight compounds. Mapping the mutations on the modeled structure implicated residues both near and far from the T1 Cu site that affected the catalytic efficiency of the mutant enzymes on ABTS and, in turn, the rate of oxidation of RB21. Several inactive clones were also mapped. The importance of geometry as well as electronic changes on the reactivity of laccases was indicated.

  15. Structural Insights into 2,2′-Azino-Bis(3-Ethylbenzothiazoline-6-Sulfonic Acid) (ABTS)-Mediated Degradation of Reactive Blue 21 by Engineered Cyathus bulleri Laccase and Characterization of Degradation Products

    PubMed Central

    Kenzom, T.; Srivastava, P.

    2014-01-01

    Advanced oxidation processes are currently used for the treatment of different reactive dyes which involve use of toxic catalysts. Peroxidases are reported to be effective on such dyes and require hydrogen peroxide and/or metal ions. Cyathus bulleri laccase, expressed in Pichia pastoris, catalyzes efficient degradation (78 to 85%) of reactive azo dyes (reactive black 5, reactive orange 16, and reactive red 198) in the presence of synthetic mediator ABTS [2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)]. This laccase was engineered to degrade effectively reactive blue 21 (RB21), a phthalocyanine dye reported to be decolorized only by peroxidases. The 816-bp segment (toward the C terminus) of the lcc gene was subjected to random mutagenesis and enzyme variants (Lcc35, Lcc61, and Lcc62) were selected based on increased ABTS oxidizing ability. Around 78 to 95% decolorization of RB21 was observed with the ABTS-supplemented Lcc variants in 30 min. Analysis of the degradation products by mass spectrometry indicated the formation of several low-molecular-weight compounds. Mapping the mutations on the modeled structure implicated residues both near and far from the T1 Cu site that affected the catalytic efficiency of the mutant enzymes on ABTS and, in turn, the rate of oxidation of RB21. Several inactive clones were also mapped. The importance of geometry as well as electronic changes on the reactivity of laccases was indicated. PMID:25261507

  16. In vitro degradation behavior and biocompatibility of Mg-Nd-Zn-Zr alloy by hydrofluoric acid treatment.

    PubMed

    Mao, Lin; Yuan, Guangyin; Niu, Jialin; Zong, Yang; Ding, Wenjiang

    2013-01-01

    In this paper, Mg-Nd-Zn-Zr alloy (denoted as JDBM) coated with hydrofluoric acid (HF) chemical conversion film (MgF2) was researched as a potential biodegradable cardiovascular stent material. The microstructures, in vitro degradation and biocompatibility were investigated. The field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) showed that a compact MgF2 film was formed on the surface of JDBM. The corrosion rate decreased in artificial plasma from 0.337 to 0.253 mm·y(-1) and the electrochemical measurement demonstrated that the corrosion resistance of JDBM alloy could be obviously improved due to the protective MgF2 film on the surface of the substrate. Meanwhile, the hemolysis ratio of JDBM decreased from 52.0% to 10.1% and the cytotoxicity met the requirement of cellular application after HF treatment. In addition, JDBM and MgF2 film showed good anti-platelet adhesion, which is a very favorable property for implant material in contact with blood directly.

  17. Determination of deoxycholic acid pool size and input rate using (24-/sup 13/C)deoxycholic acid and serum sampling

    SciTech Connect

    Stellard, F.; Paumgartner, G.; van Berge Henegouwen, G.P.; van der Werf, S.D.

    1986-11-01

    We have developed an isotope dilution method for determination of deoxycholic acid pool size and input rate which employs oral administration of 50 mg of (24-/sup 13/C)deoxycholic acid and serum sampling. The method has been validated by classical isotope dilution technique using (24-/sup 14/C)deoxycholic acid and bile sampling in five patients with colonic adenomas. Excellent agreement between pool sizes and input rates determined with /sup 13/C/12C isotope ratio measurements in serum and /sup 14/C measurements in bile was obtained when isotope ratios were measured in the conjugated fraction of deoxycholic acid in serum. We conclude that pool size and input rate of deoxycholic acid can accurately be determined by blood sampling after oral administration of (24-/sup 13/C)deoxycholic acid, therewith eliminating the use of radioactive tracers and the need for bile sampling.

  18. Occurrence and fate of the herbicide glyphosate and its degradate aminomethylphosphonic acid in the atmosphere

    USGS Publications Warehouse

    Chang, Feng-Chih; Simcik, M.F.; Capel, P.D.

    2011-01-01

    This is the first report on the ambient levels of glyphosate, the most widely used herbicide in the United States, and its major degradation product, aminomethylphosphonic acid (AMPA), in air and rain. Concurrent, weekly integrated air particle and rain samples were collected during two growing seasons in agricultural areas in Mississippi and Iowa. Rain was also collected in Indiana in a preliminary phase of the study. The frequency of glyphosate detection ranged from 60 to 100% in both air and rain. The concentrations of glyphosate ranged from 3 and from <0.1 to 2.5 µg/L in air and rain samples, respectively. The frequency of detection and median and maximum concentrations of glyphosate in air were similar or greater to those of the other high-use herbicides observed in the Mississippi River basin, whereas its concentration in rain was greater than the other herbicides. It is not known what percentage of the applied glyphosate is introduced into the air, but it was estimated that up to 0.7% of application is removed from the air in rainfall. Glyphosate is efficiently removed from the air; it is estimated that an average of 97% of the glyphosate in the air is removed by a weekly rainfall ≥30 mm.

  19. Degradable biocomposite of nano calcium-deficient hydroxyapatite-multi(amino acid) copolymer

    PubMed Central

    Li, Hong; Gong, Min; Yang, Aiping; Ma, Jian; Li, Xiangde; Yan, Yonggang

    2012-01-01

    Background and methods A nano calcium-deficient hydroxyapatite (n-CDHA)-multi(amino acid) copolymer (MAC) composite bone substitute biomaterial was prepared using an in situ polymerization method. The composition, structure, and compressive strength of the composite was characterized, and the in vitro degradability in phosphate-buffered solution and preliminary cell responses to the composite were investigated. Results The composite comprised n-CDHA and an amide linkage copolymer. The compressive strength of the composite was in the range of 88–129 MPa, varying with the amount of n-CDHA in the MAC (ranging from 10 wt% to 50 wt%). Weight loss from the composite increased (from 32.2 wt% to 44.3 wt%) with increasing n-CDHA content (from 10 wt% to 40 wt%) in the MAC after the composite was soaked in phosphate-buffered solution for 12 weeks. The pH of the soaking medium varied from 6.9 to 7.5. MG-63 cells with an osteogenic phenotype were well adhered and spread on the composite surface. Viability and differentiation increased with time, indicating that the composite had no negative effects on MG-63 cells. Conclusion The n-CDHA-MAC composite had good cytocompatibility and has potential to be used as a bone substitute. PMID:22457591

  20. Amycolatopsis thailandensis sp. nov., a poly(L-lactic acid)-degrading actinomycete, isolated from soil.

    PubMed

    Chomchoei, Atchareeya; Pathom-Aree, Wasu; Yokota, Akira; Kanongnuch, Chartchai; Lumyong, Saisamorn

    2011-04-01

    A novel actinomycete that was capable of degrading poly(l-lactic acid), strain CMU-PLA07(T), was isolated from soil in northern Thailand. Strain CMU-PLA07(T) had biochemical, chemotaxonomic, morphological and physiological properties that were consistent with its classification in the genus Amycolatopsis. 16S rRNA gene sequence analysis showed that the isolate formed a phyletic line within the genus Amycolatopsis. Strain CMU-PLA07(T) was most similar to Amycolatopsis coloradensis IMSNU 22096(T) (99.5 % 16S rRNA gene sequence similarity) and Amycolatopsis alba DSM 44262(T) (99.4 %). However, strain CMU-PLA07(T) was distinguishable from the type strains of species of the genus Amycolatopsis on the basis of DNA-DNA relatedness and phenotypic data. Therefore, strain CMU-PLA07(T) is considered to represent a novel species of the genus Amycolatopsis, for which the name Amycolatopsis thailandensis sp. nov. is proposed. The type strain is CMU-PLA07(T) ( = JCM 16380(T) = BCC 38279(T)).

  1. Acid-degradable hyperbranched polymer and its application in bottom anti-reflective coatings

    NASA Astrophysics Data System (ADS)

    Mercado, Ramil-Marcelo L.; Xu, Hao; Lowes, Joyce A.; Meador, Jim D.; Guerrero, Douglas J.

    2008-11-01

    A photosensitive developer-soluble bottom anti-reflective coating (DBARC) system is described for KrF and ArF lithographic applications. The system contains an acid-degradable branched polymer that is self-crosslinked into a polymeric film after spin coating and baking at high temperature, rendering a solvent-insoluble coating. The DBARC coating is tunable in terms having the appropriate light absorption (k value) and thickness for desirable reflection control. After the exposure of the resist, the DBARC layer decrosslinks into developer-soluble small molecules in the presence of photoacid generator (PAG). Thus the DBARC layer is removed simultaneously with the photoresist in the development process, instead of being etched away in a plasma-etching chamber in the case of traditional BARC layers. The etch budget is significantly improved so that a thin resist can be used for better resolution. Alternatively, the etch step can be omitted in the case of the formation of layers that may be damaged by exposure to plasma.

  2. Occurrence and fate of the herbicide glyphosate and its degradate aminomethylphosphonic acid in the atmosphere.

    PubMed

    Chang, Feng-chih; Simcik, Matt F; Capel, Paul D

    2011-03-01

    This is the first report on the ambient levels of glyphosate, the most widely used herbicide in the United States, and its major degradation product, aminomethylphosphonic acid (AMPA), in air and rain. Concurrent, weekly integrated air particle and rain samples were collected during two growing seasons in agricultural areas in Mississippi and Iowa. Rain was also collected in Indiana in a preliminary phase of the study. The frequency of glyphosate detection ranged from 60 to 100% in both air and rain. The concentrations of glyphosate ranged from <0.01 to 9.1 ng/m(3) and from <0.1 to 2.5 µg/L in air and rain samples, respectively. The frequency of detection and median and maximum concentrations of glyphosate in air were similar or greater to those of the other high-use herbicides observed in the Mississippi River basin, whereas its concentration in rain was greater than the other herbicides. It is not known what percentage of the applied glyphosate is introduced into the air, but it was estimated that up to 0.7% of application is removed from the air in rainfall. Glyphosate is efficiently removed from the air; it is estimated that an average of 97% of the glyphosate in the air is removed by a weekly rainfall ≥ 30 mm.

  3. The effect of natural iron oxide and oxalic acid on the photocatalytic degradation of isoproturon: a kinetics and analytical study.

    PubMed

    Boucheloukh, H; Remache, W; Parrino, F; Sehili, T; Mechakra, H

    2017-03-27

    The photocatalytic degradation of isoproturon, a persistent toxic herbicide, was investigated in the presence of natural iron oxide and oxalic acid and under UV irradiation. The influence of the relevant parameters such as the pH and the iron oxide and oxalic acid concentrations has been studied. The presence of natural iron oxide and oxalic acid in the system effectively allow the degradation of isoproturon, whereas the presence of t-butyl alcohol adversely affects the phototransformation of the target pollutant, thus indicating that an OH radical initiated the degradation mechanism. The degradation mechanism of isoproturon was investigated by means of GC-MS analysis. Oxidation of both the terminal N-(CH3)2 and isopropyl groups is the initial process leading to N-monodemethylated (NHCH3), N-formyl (N(CH3)CHO), and CHCH3OH as the main intermediates. The substitution of the isopropyl group by an OH group is also observed as a side process.

  4. Separation and detection of VX and its methylphosphonic acid degradation products on a microchip using indirect laser-induced fluorescence.

    PubMed

    Heleg-Shabtai, Vered; Gratziany, Natzach; Liron, Zvi

    2006-05-01

    The application of indirect LIF (IDLIF) technique for on-chip electrophoretic separation and detection of the nerve agent O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) and its major phosphonic degradation products, ethyl methylphosphonic acid (EMPA) and methylphosphonic acid (MPA) was demonstrated. Separation and detection of MPA degradation products of VX and the nerve agent isopropyl methylphosphonofluoridate (GB) are presented. The negatively charged dye eosin was found to be a good fluorescent marker for both the negatively charged phosphonic acids and the positively charged VX, and was chosen as the IDLIF visualization fluorescent dye. Separation and detection of VX, EMPA, and MPA in a simple-cross microchip were completed within less than a minute, and consumed only a 50 pL sample volume. A characteristic system peak that appeared in all IDLIF electropherograms served as an internal standard that increased the reliability of peak identification. The negative peak of both VX and the MPAs is in agreement with indirect detection theory and with previous reports in the literature. The LOD of VX and EMPA by IDLIF was 30 and 37 microM, respectively. Despite the fact that the detection sensitivity is relatively low, the rapid simultaneous on-chip analysis of both VX and its degradation products as well as the separation and detection of the MPA degradation products of both VX and GB, increases detection reliability and may present a choice when sensitivity is not critical compared with speed and simplicity of the assay.

  5. Pretreatment of lignocellulosic material with fungi capable of higher lignin degradation and lower carbohydrate degradation improves substrate acid hydrolysis and the eventual conversion to ethanol.

    PubMed

    Kuhar, Sarika; Nair, Lavanya M; Kuhad, Ramesh Chander

    2008-04-01

    Phanerochaete chrysosporium, Pycnoporus cinnabarinus,and fungal isolates RCK-1 and RCK-3 were tested for their lignin degradation abilities when grown on wheat straw (WS) and Prosopis juliflora (PJ) under solid-state cultivation conditions. Fungal isolate RCK-1 degraded more lignin in WS (12.26% and 22.64%) and PJ (19.30% and 21.97%) and less holocellulose in WS (6.27% and 9.39%) and PJ (3.01% and 4.58%) after 10 and 20 days, respectively, than other fungi tested. Phanerochaete chrysosporium caused higher substrate mass loss and degraded more of holocellulosic content (WS: 55.67%; PJ: 48.89%) than lignin (WS: 18.89%; PJ: 20.20%) after 20 days. The fungal pretreatment of WS and PJ with a high-lignin-degrading and low-holocellulose-degrading fungus (fungal isolate RCK-1) for 10 days resulted in (i) reduction in acid load for hydrolysis of structural polysaccharides (from 3.5% to 2.5% in WS and from 4.5% to 2.5% in PJ), (ii) an increase in the release of fermentable sugars (from 30.27 to 40.82 g L(-1) in WS and from 18.18 to 26.00 g L(-1) in PJ), and (iii) a reduction in fermentation inhibitors (total phenolics) in acid hydrolysate of WS (from 1.31 to 0.63 g L(-1)) and PJ (from 2.05 to 0.80 g L(-1)). Ethanol yield and volumetric productivity from RCK-1-treated WS (0.48 g g(-1) and 0.54 g L(-1) h(-1), respectively) and PJ (0.46 g g(-1) and 0.33 g L(-1) h(-1), respectively) were higher than untreated WS (0.36 g g(-1) and 0.30 g L(-1) h(-1), respectively) and untreated PJ (0.42 g g(-1) and 0.21 g L(-1) h(-1), respectively).

  6. Analysis and detection of the herbicides dimethenamid and flufenacet and their sulfonic and oxanilic acid degradates in natural water

    USGS Publications Warehouse

    Zimmerman, L.R.; Schneider, R.J.; Thurman, E.M.

    2002-01-01

    Dimethenamid [2-chloro-N-(2,4-dimethyl-3-thienyl)-N-(2-methoxy-1-methylethyl)acetamide] and flufenacet [N-(4-fluorophenyl)-N-(1-methylethyl)-2-(5-(trifluoromethyl)-1,3,4- thiadiazol-2-yl)oxy] were isolated by C-18 solid-phase extraction and separated from their ethanesulfonic acid (ESA) and oxanilic acid (OXA) degradates during their elution using ethyl acetate for the parent compound, followed by methanol for the polar degradates. The parent compounds were detected using gas chromatography-mass spectrometry in selected-ion mode. The ESA and OXA degradates were detected using high-performance liquid chromatography-electrospray mass spectrometry (HPLC-ESPMS) in negative-ion mode. The method detection limits for a 123-mL sample ranged from 0.01 to 0.07 μg/L. These methods are compatible with existing methods and thus allow for analysis of 17 commonly used herbicides and 18 of their degradation compounds with one extraction. In a study of herbicide transport near the mouth of the Mississippi River during 1999 and 2000, dimethenamid and its ESA and OXA degradates were detected in surface water samples during the annual spring flushes. For flufenacet, the only detections at the study site were for the ESA degradates in samples collected at the peak of the herbicide spring flush in 2000. The low frequency of detections in surface water likely is due to dimethenamid and flufenacet being relatively new herbicides. In addition, detectable amounts of the stable degradates have not been detected in ground water.

  7. Sonochemical synthesis of Pr-doped ZnO nanoparticles for sonocatalytic degradation of Acid Red 17.

    PubMed

    Khataee, Alireza; Karimi, Atefeh; Arefi-Oskoui, Samira; Darvishi Cheshmeh Soltani, Reza; Hanifehpour, Younes; Soltani, Behzad; Joo, Sang Woo

    2015-01-01

    Undoped and Pr-doped ZnO nanoparticles were prepared using a simple sonochemical method, and their sonocatalytic activity was investigated toward degradation of Acid Red 17 (AR17) under ultrasonic (US) irradiation. Synthesized nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques. The extent of sonocatalytic degradation was higher compared with sonolysis alone. The decolorization efficiency of sonolysis alone, sonocatalysis with undoped ZnO and 5% Pr-doped ZnO was 24%, 46% and 100% within reaction time of 70min, respectively. Sonocatalytic degradation of AR17 increased with increasing the amount of dopant and catalyst dosage and decreasing initial dye concentration. Natural pH was favored the sonocatalytic degradation of AR17. With the addition of chloride, carbonate and sulfate as radical scavengers, the decolorization efficiency was decreased from 100% to 65%, 71% and 89% at the reaction time of 70min, respectively, indicating that the controlling mechanism of sonochemical degradation of AR17 is the free radicals (not pyrolysis). The addition of peroxydisulfate and hydrogen peroxide as enhancer improved the degradation efficiency from 79% to 85% and 93% at the reaction time of 50min, respectively. The result showed good reusability of the synthesized sonocatalyst.

  8. Accelerated weathering-induced degradation of poly(lactic acid) fiber studied by near-infrared (NIR) hyperspectral imaging.

    PubMed

    Shinzawa, Hideyuki; Nishida, Masakazu; Tanaka, Toshiyuki; Kanematsu, Wataru

    2012-04-01

    Hydrolysis degradation of a set of drawn poly(lactic acid) (PLA) fibers was induced by an accelerated weathering test, radiating ultraviolet (UV) light under a certain temperature and humidity. The fine features of the transient behavior of the PLA fibers were captured by near-infrared (NIR) hyperspectral imaging. The PLA fibers showed a gradual decrease in mechanical property (e.g., tensile strength), indicating hydrolysis degradation. Thus, the detailed analysis of the spectral variation, in turn, offers useful information on the molecular-level degradation behavior of the drawn PLA fibers. The variation of the spectral intensity as well as band position shift of the crystalline band of PLA was analyzed. The spectral intensity of the crystalline band of PLA showed gradual decrease, suggesting the decrease in molecular weight induced by the hydrolysis degradation. In addition, the crystalline band also exhibited a coinciding shift to the lower wavenumber direction with the weathering test, revealing cleavage-induced crystallization of the PLA samples. Consequently, the hydrolysis degradation induced by the weathering test substantially accelerates predominant degradation of the amorphous structure of the PLA and such variation of the molecular structure, in turn, brings less ductility to the PLA fiber.

  9. Chemical sporulation and germination: cytoprotective nanocoating of individual mammalian cells with a degradable tannic acid-FeIII complex.

    PubMed

    Lee, Juno; Cho, Hyeoncheol; Choi, Jinsu; Kim, Doyeon; Hong, Daewha; Park, Ji Hun; Yang, Sung Ho; Choi, Insung S

    2015-12-07

    Individual mammalian cells were coated with cytoprotective and degradable films by cytocompatible processes maintaining the cell viability. Three types of mammalian cells (HeLa, NIH 3T3, and Jurkat cells) were coated with a metal-organic complex of tannic acid (TA) and ferric ion, and the TA-Fe(III) nanocoat effectively protected the coated mammalian cells against UV-C irradiation and a toxic compound. More importantly, the cell proliferation was controlled by programmed formation and degradation of the TA-Fe(III) nanocoat, mimicking the sporulation and germination processes found in nature.

  10. Degradation of 2,4-dichlorophenoxyacetic acid by Pseudomonas cepacia DBO1(pRO101) in a dual-substrate chemostat.

    PubMed Central

    Daugherty, D D; Karel, S F

    1994-01-01

    To determine the effect of a secondary carbon source on biodegradation of a chloroaromatic compound, Pseudomonas cepacia DBO1(pRO101) was grown in continuous cultures on basal salts media containing various mixtures of 2,4-dichlorophenoxyacetic acid (2,4-D) and succinate. Both succinate and 2,4-D were metabolized over the entire range of dilution rates and compositions analyzed (0.05 to 0.6 h-1). 2,4-Dichlorophenol (DCP), the only intermediate detected, accumulated to significant amounts (10 to 21 mg/liter) in the chemostat only when the dilution rate was 0.4 h-1 or greater. At these concentrations, DCP reduced the apparent growth rate of P. cepacia DBO1(pRO101) in batch cultures by 15 to 35% over the apparent growth rate on succinate alone. Succinate fed to the chemostat increased the cell density as well as the percentage of 2,4-D that was consumed at each dilution rate. When the amount of succinate in the feed exceeded the amount of 2,4-D, the specific rates of 2,4-D degradation in the chemostat or by washed cells were significantly lower than the specific rates for cells grown on 2,4-D alone, suggesting repression by succinate. However, when the amount of 2,4-D in the feed exceeded the amount of succinate, the specific rates of 2,4-D degradation remained at values equivalent to or higher than the specific rate for cells grown on 2,4-D alone. DCP accumulated significantly in the washed-cell assay, suggesting that the level of DCP hydroxylase is rate limiting.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7524443

  11. (Tri)butyltin biotic degradation rates and pathways in different compartments of a freshwater model ecosystem.

    PubMed

    Tessier, Emmanuel; Amouroux, David; Morin, Anne; Christian, Lehnhoff; Thybaud, Eric; Vindimian, Eric; Donard, Olivier F X

    2007-12-15

    Experiments were conducted in controlled temperate freshwater ecosystems (microcosms) to determine the persistence and biogeochemical dynamic of tributyltin (TBT) and its degradation products. TBT and its derivatives were monitored simultaneously for 23 days (552 h) in sediment-water systems, with or without macroorganisms (macrophytes: Elodea canadensis and gastropods: Lymnaea stagnalis). Biphasic TBT removal from the water column was significantly enhanced by the presence of biota. The persistence of TBT in biota was assessed by a kinetic approach of the different bioaccumulation pathways and associated metabolisms adopted by the snails and the macrophytes in response to the TBT contamination. Furthermore, sediment acted for the final sink for butyltins in both types of microcosms, with more than 70% of TBT and its metabolites recovered in this compartment after two weeks of exposure. Degradation pathways in sediments of both biotic and abiotic microcosms appeared to represent a key process in TBT cycle and were characterized by half-lives in the range of one month. Specific transformation and transfer pathways of TBT as reactional mechanisms are discussed and modelled assessing in detail the role of each compartment with regards to the fate of TBT in the model aquatic ecosystems.

  12. Interplay between acid phosphatase and cysteine proteases in mediating vitellin degradation during early embryogenesis of Periplaneta americana.

    PubMed

    Oliveira, Danielle M P; Ramos, Isabela B; Reis, Flavia C G; Lima, Ana P C A; Machado, Ednildo A

    2008-05-01

    In this work, we characterized the activities of two classes of proteases and AcP during early embryogenesis of Periplaneta americana. AcP activity was first detected at day 6 and reached a maximum level at day 10 of development. Using phosphoamino acids, phosphatase activity was shown to be directed only against phosphotyrosine at day 6 while at day 10 it was also active against phosphoserine. In parallel, two classes of proteases were detected and located within yolk granules: a clan CA-cysteine protease, which was inhibited by E-64, insensitive to CA 074 and activated by acidic pH at day 3; and a neutral serine protease, which was inhibited by aprotinin at day 6. Assays of vitellin (Vt) degradation evidenced that incubations at neutral pH induced slight proteolysis, while the incubations at acidic pH did not result in Vt degradation. However, pre-incubations of Vt with AcP increased the levels of Vt acidic proteolysis and this could be inhibited by the addition of phosphatase inhibitors. On the other hand, the same pre-incubations showed no effects on the profile of degradation at neutral pH. We propose that AcP and cysteine protease cooperate to assure Vt breakdown during early embryogenesis of P. americana.

  13. Degradation of /sup 14/C-labeled lignins and /sup 14/C-labeled aromatic acids by fusarium solani

    SciTech Connect

    Norris, D.M.

    1980-08-01

    Abilities of isolate AF-W1 of Fusarium solani to degrade the side chain and the ring structure of synthetic dehydrogenative polymerizates, aromatic acids, or lignin in sound wood were investigated under several conditions of growth substrate or basal medium and pH. Significant transformations of lignins occurred in 50 days in both unextracted and extracted sound wood substrances with 3% malt as the growth substrate and the pH buffered initially at 4.0 with 2,2-dimethylsuccinate. Degradation of lignin in such woods also occurred under unbuffered pH conditions when a basal medium of either 3% malt or powdered cellulose in deionized water was present. Decomposition of the lignin in these woods did not occur in cultures where D-glucose was present as a growth substrate. F. solani significantly transformed, as measured as evolved /sup 14/CO/sub 2/, both synthetic side chain (beta, gamma)-/sup 14/C- and U-ring-/sup 14/C-labeled lignins in 30 days under liquid culture conditions of only distilled deionized water and no pH adjustment. Degradation of dehydrogenative polymerizates by F. solani was reduced drastically when D2 was the liquid medium. AF-W1 also cleaved the alpha-/sup 14/C from p- hydroxybenzoic acid and evolved /sup 14/CO/sub 2/ from the substrace, (3-/sup 14/C) cinnamic acid. Thus, the fungus cleaved side chain carbon from substrate that originally lacked hydroxyl substitution on the aromatic nucleus. Surprisingly, small amounts of /sup 14/C cleaved from aromatic acids by F. solani were incorporated into cell mass. Initial buffering of the culture medium to pH 4.0 or 5.0 with 0.1 M2,2-dimethylsuccinate significantly increased F. solani degradation of all lignins or aromatic acids. Results indicated that AF-W1 used lignin as a sole carbon source.

  14. Degradation State, Sources, and Reactivity of Dissolved Organic Matter from an Amino Acid Time Series in an Agricultural Watershed

    NASA Astrophysics Data System (ADS)

    Matiasek, S. J.; Pellerin, B. A.; Spencer, R. G.; Bergamaschi, B. A.; Hernes, P.

    2015-12-01

    A detailed time series of dissolved amino acids was obtained in an agricultural watershed in the northern Central Valley, California, USA to investigate the roles of hydrologic and seasonal changes on the composition of dissolved organic matter (DOM). Total hydrolysable amino acid (THAA) concentrations ranged from 0.55 to 9.96 μM (mean 3.76 ± 1.80 μM) and not only peaked with discharge during winter storms, but also remained elevated throughout the irrigation season when discharge was low. Summer irrigation was a critical hydrologic regime for DOM cycling, since it mobilized DOM similar in concentration and reactivity to DOM released during winter storms for an extended period of time, with the largest amino acid contributions to the dissolved organic carbon (DOC) and the dissolved organic nitrogen (DON) pools (3.4 ‒ 3.7 % DOC-AA, 17.4 ‒ 22.5 % DON-AA), the largest proportion of basic amino acids (B/(B+A) = 0.19 ‒ 0.22), and the largest degradation index values (mean 1.37 ± 0.96). The mole percent of non-protein amino acids, commonly considered as an indicator of microbial degradation, decreased with DOM processing and was highest during summer (mean 4.1 ± 1.1%). A lack of correlation between THAA concentrations and UV-Vis absorbance and fluorescence proxies (including "protein-like" fluorophores B and T) indicated that optical properties may be limited in representing amino acid dynamics in this system. A new parameter for DOM processing derived from trends in individual amino acids demonstrated strong potential for inferring the extent of DOM degradation in freshwater systems. The biogeochemical relevance of irrigation practices is heightened by timing, since the additional export of reactive DOM coincides with enhanced downstream DOM processing in the Sacramento-San Joaquin River Delta, a critical habitat for endangered species serving as water source for 25 million Californians.

  15. Degradable, pH-sensitive, membrane-destabilizing, comb-like polymers for intracellular delivery of nucleic acids.

    PubMed

    Lin, Yen-Ling; Jiang, Guohua; Birrell, Lisa K; El-Sayed, Mohamed E H

    2010-09-01

    This report describes the design and synthesis of a new series of degradable, pH-sensitive, membrane-destabilizing, comb-like polymers that can enhance the intracellular delivery of therapeutic nucleic acids. These comb-like polymers are based on a diblock polymer backbone where the first block is a copolymer of pH-sensitive ethyl acrylic acid (EAA) monomers and hydrophobic butyl methacrylate (BMA) or hexyl methacrylate monomers. The second block is a homopolymer of N-acryloxy succinimide (NASI) or ss-benzyl l-aspartate N-carboxy-anhydride (BLA-NCA) monomers, which are functionalized to allow controlled grafting of hydrophobic HMA and cationic trimethyl aminoethyl methacrylate (TMAEMA) copolymers via acid-labile hydrazone linkages. These comb-like polymers displayed high hemolytic activity in acidic solutions, which increased with the increase in polymer concentration. All comb-like polymers degraded into small fragments upon incubation in an acidic solution (pH 5.8) due to hydrolysis of the hydrazone linkages connecting the hydrophobic/cationic grafts to the polymer backbone. Comb-like polymers successfully complexed anti-GAPDH siRNA molecules into serum- and nuclease-stable particles, which successfully silenced GAPDH expression at both the mRNA and protein levels. These results collectively indicate the potential of these new comb-like polymers to serve as vehicles for effective intracellular delivery of therapeutic nucleic acids.

  16. Complete degradation of the azo dye Acid Orange-7 and bioelectricity generation in an integrated microbial fuel cell, aerobic two-stage bioreactor system in continuous flow mode at ambient temperature.

    PubMed

    Fernando, Eustace; Keshavarz, Taj; Kyazze, Godfrey

    2014-03-01

    In this study, the commercially used model azo dye Acid Orange-7 (AO-7) was fully degraded into less toxic intermediates using an integrated microbial fuel cell (MFC) and aerobic bioreactor system. The integrated bioreactor system was operated at ambient temperature and continuous-flow mode. AO-7 loading rate was varied during experiments from 70gm(-3)day(-1) to 210gm(-3)day(-1). Colour and soluble COD removal rates reached>90% under all AO-7 loading rates. The MFC treatment stage prompted AO-7 to undergo reductive degradation into its constituent aromatic amines. HPLC-MS analysis of metabolite extracts from the aerobic stage of the bioreactor system indicated further oxidative degradation of the resulting aromatic amines into simpler compounds. Bioluminescence based Vibrio fischeri ecotoxicity testing demonstrated that aerobic stage effluent exhibited toxicity reductions of approximately fivefold and ten-fold respectively compared to the dye wastewater influent and MFC-stage effluent.

  17. Chemical sporulation and germination: cytoprotective nanocoating of individual mammalian cells with a degradable tannic acid-FeIII complex

    NASA Astrophysics Data System (ADS)

    Lee, Juno; Cho, Hyeoncheol; Choi, Jinsu; Kim, Doyeon; Hong, Daewha; Park, Ji Hun; Yang, Sung Ho; Choi, Insung S.

    2015-11-01

    Individual mammalian cells were coated with cytoprotective and degradable films by cytocompatible processes maintaining the cell viability. Three types of mammalian cells (HeLa, NIH 3T3, and Jurkat cells) were coated with a metal-organic complex of tannic acid (TA) and ferric ion, and the TA-FeIII nanocoat effectively protected the coated mammalian cells against UV-C irradiation and a toxic compound. More importantly, the cell proliferation was controlled by programmed formation and degradation of the TA-FeIII nanocoat, mimicking the sporulation and germination processes found in nature.Individual mammalian cells were coated with cytoprotective and degradable films by cytocompatible processes maintaining the cell viability. Three types of mammalian cells (HeLa, NIH 3T3, and Jurkat cells) were coated with a metal-organic complex of tannic acid (TA) and ferric ion, and the TA-FeIII nanocoat effectively protected the coated mammalian cells against UV-C irradiation and a toxic compound. More importantly, the cell proliferation was controlled by programmed formation and degradation of the TA-FeIII nanocoat, mimicking the sporulation and germination processes found in nature. Electronic supplementary information (ESI) available: Experimental details, LSCM images, and SEM and TEM images. See DOI: 10.1039/c5nr05573c

  18. Antagonism between lipid-derived reactive carbonyls and phenolic compounds in the Strecker degradation of amino acids.

    PubMed

    Delgado, Rosa M; Hidalgo, Francisco J; Zamora, Rosario

    2016-03-01

    The Strecker-type degradation of phenylalanine in the presence of 2-pentanal and phenolic compounds was studied to investigate possible interactions that either promote or inhibit the formation of Strecker aldehydes in food products. Phenylacetaldehyde formation was promoted by 2-pentenal and also by o- and p-diphenols, but not by m-diphenols. This is consequence of the ability of phenolic compounds to be converted into reactive carbonyls and produce the Strecker degradation of the amino acid. When 2-pentenal and phenolic compounds were simultaneously present, an antagonism among them was observed. This antagonism is suggested to be a consequence of the ability of phenolic compounds to either react with both 2-pentenal and phenylacetaldehyde, or compete with other carbonyl compounds for the amino acids, a function that is determined by their structure. All these results suggest that carbonyl-phenol reactions may be used to modulate flavor formation produced in food products by lipid-derived reactive carbonyls.

  19. Inoculation of Pichia kudriavzevii RB1 degrades the organic acids present in raw compost material and accelerates composting.

    PubMed

    Nakasaki, Kiyohiko; Araya, Shogo; Mimoto, Hiroshi

    2013-09-01

    In this study, the yeast strain Pichia kudriavzevii RB1 was used as an inoculum to accelerate organic matter degradation of rabbit food with added organic acids, which was used as a model food waste for composting. The RB1 strain rapidly degraded the organic acids present in the raw compost material, leading to an increase in pH beyond the neutral level, within 2 days. Both mesophilic and thermophilic bacteria proliferated faster in the compost with RB1 inoculation than in that without inoculation. Although the yeast died with the increase in compost temperature, it affected the early stages of composting prior to the thermophilic stage and accelerated the composting process by 2 days by eliminating the initial lag phase seen in the growth of other microorganisms. Moreover, populations of Bacillus thermoamylovorans, Bacillus foraminis, and Bacillus coagulans became dominant during the thermophilic stages of both composting with and without RB1 inoculation.

  20. Modeling of Phenoxy Acid Herbicide Mineralization and Growth of Microbial Degraders in 15 Soils Monitored by Quantitative Real-Time PCR of the Functional tfdA Gene

    PubMed Central

    Bælum, Jacob; Prestat, Emmanuel; David, Maude M.; Strobel, Bjarne W.

    2012-01-01

    Mineralization potentials, rates, and kinetics of the three phenoxy acid (PA) herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA), and 2-(4-chloro-2-methylphenoxy)propanoic acid (MCPP), were investigated and compared in 15 soils collected from five continents. The mineralization patterns were fitted by zero/linear or exponential growth forms of the three-half-order models and by logarithmic (log), first-order, or zero-order kinetic models. Prior and subsequent to the mineralization event, tfdA genes were quantified using real-time PCR to estimate the genetic potential for degrading PA in the soils. In 25 of the 45 mineralization scenarios, ∼60% mineralization was observed within 118 days. Elevated concentrations of tfdA in the range 1 × 105 to 5 × 107 gene copies g−1 of soil were observed in soils where mineralization could be described by using growth-linked kinetic models. A clear trend was observed that the mineralization rates of the three PAs occurred in the order 2,4-D > MCPA > MCPP, and a correlation was observed between rapid mineralization and soils exposed to PA previously. Finally, for 2,4-D mineralization, all seven mineralization patterns which were best fitted by the exponential model yielded a higher tfdA gene potential after mineralization had occurred than the three mineralization patterns best fitted by the Lin model. PMID:22635998

  1. Evaluating the interaction of faecal pellet deposition rates and DNA degradation rates to optimize sampling design for DNA-based mark-recapture analysis of Sonoran pronghorn.

    PubMed

    Woodruff, S P; Johnson, T R; Waits, L P

    2015-07-01

    Knowledge of population demographics is important for species management but can be challenging in low-density, wide-ranging species. Population monitoring of the endangered Sonoran pronghorn (Antilocapra americana sonoriensis) is critical for assessing the success of recovery efforts, and noninvasive DNA sampling (NDS) could be more cost-effective and less intrusive than traditional methods. We evaluated faecal pellet deposition rates and faecal DNA degradation rates to maximize sampling efficiency for DNA-based mark-recapture analyses. Deposition data were collected at five watering holes using sampling intervals of 1-7 days and averaged one pellet pile per pronghorn per day. To evaluate nuclear DNA (nDNA) degradation, 20 faecal samples were exposed to local environmental conditions and sampled at eight time points from one to 124 days. Average amplification success rates for six nDNA microsatellite loci were 81% for samples on day one, 63% by day seven, 2% by day 14 and 0% by day 60. We evaluated the efficiency of different sampling intervals (1-10 days) by estimating the number of successful samples, success rate of individual identification and laboratory costs per successful sample. Cost per successful sample increased and success and efficiency declined as the sampling interval increased. Results indicate NDS of faecal pellets is a feasible method for individual identification, population estimation and demographic monitoring of Sonoran pronghorn. We recommend collecting samples <7 days old and estimate that a sampling interval of four to seven days in summer conditions (i.e., extreme heat and exposure to UV light) will achieve desired sample sizes for mark-recapture analysis while also maximizing efficiency [Corrected].

  2. Enzymatic degradation processes of lamellar crystals in thin films for poly[(R)-3-hydroxybutyric acid] and its copolymers revealed by real-time atomic force microscopy.

    PubMed

    Numata, Keiji; Hirota, Takuya; Kikkawa, Yoshihiro; Tsuge, Takeharu; Iwata, Tadahisa; Abe, Hideki; Doi, Yoshiharu

    2004-01-01

    Enzymatic degradation processes of flat-on lamellar crystals in melt-crystallized thin films of poly[(R)-3-hydroxybutyric acid] (P(3HB)) and its copolymers were characterized by real-time atomic force microscopy (AFM) in a phosphate buffer solution containing PHB depolymerase from Ralstonia pickettii T1. Fiberlike crystals with regular intervals were generated along the crystallographic a axis at the end of lamellar crystals during the enzymatic degradation. The morphologies and sizes of the fiberlike crystals were markedly dependent on the compositions of comonomer units in the polyesters. Length, width, interval, and thickness of the fiberlike crystals after the enzymatic degradation for 2 h were measured by AFM, and the dimensions were related to the solid-state structures of P(3HB) and its copolymers. The width and thickness decreased at the tip of fiberlike crystals, indicating that the enzymatic degradation of crystals takes place not only along the a axis but also along the b and c axes. These results from AFM measurement were compared with the data on crystal size by wide-angle X-ray diffraction, and on lamellar thickness and long period by small-angle X-ray scattering. In addition, the enzymatic erosion rate of flat-on lamellar crystals along the a axis was measured from real-time AFM height images. A schematic glacier model for the enzymatic degradation of flat-on lamellar crystals of P(3HB) by PHB depolymerase has been proposed on the basis of the AFM observations.

  3. 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.

  4. Effect of Glucose on the Fatty Acid Composition of Cupriavidus necator JMP134 during 2,4-Dichlorophenoxyacetic Acid Degradation: Implications for Lipid-Based Stable Isotope Probing Methods▿†

    PubMed Central

    Lerch, Thomas Z.; Dignac, Marie-France; Barriuso, Enrique; Mariotti, André

    2011-01-01

    Combining lipid biomarker profiling with stable isotope probing (SIP) is a powerful technique for studying specific microbial populations responsible for the degradation of organic pollutants in various natural environments. However, the presence of other easily degradable substrates may induce significant physiological changes by altering both the rate of incorporation of the target compound into the biomass and the microbial lipid profiles. In order to test this hypothesis, Cupriavidus necator JMP134, a 2,4-dichlorophenoxyacetic acid (2,4-D)-degrading bacterium, was incubated with [13C]2,4-D, [13C]glucose, or mixtures of both substrates alternatively labeled with 13C. C. necator JMP134 exhibited a preferential use of 2,4-D over glucose. The isotopic analysis showed that glucose had only a small effect on the incorporation of the acetic chain of 2,4-D into the biomass (at days 2 and 3) and no effect on that of the benzenic ring. The addition of glucose did change the fatty acid methyl ester (FAME) composition. However, the overall FAME isotopic signature reflected that of the entire biomass. Compound-specific individual isotopic analyses of FAME composition showed that the 13C-enriched FAME profiles were slightly or not affected when tracing the 2,4-D acetic chain or 2,4-D benzenic ring, respectively. This batch study is a necessary step for validating the use of lipid-based SIP methods in complex environments. PMID:21856833

  5. Distribution and Catabolic Diversity of 3-Chlorobenzoic Acid Degrading Bacteria Isolated from Geographically-Separated Pristine Soils

    DTIC Science & Technology

    1994-08-01

    could be a reflection of current interest in studying bacterial evolution , therefore, rapid development of new pathways is an attractive explanation...Ecology, Research on Microbial Evolution stock cultures (TFD strains). The TFD isolates were collected from a variety of sources and previously...PAGE OF A8STRACT 9954 A,, IL, 4*o DISTRIBUTION AND CATABOLIC DIVERSITY OF 3-CHLOROBENZOIC ACID DEGRADING BACTERIA ISOLATED FROM GEOGRAPHICALLY

  6. The cellular growth rate controls overall mRNA turnover, and modulates either transcription or degradation rates of particular gene regulons

    PubMed Central

    García-Martínez, José; Delgado-Ramos, Lidia; Ayala, Guillermo; Pelechano, Vicent; Medina, Daniel A.; Carrasco, Fany; González, Ramón; Andrés-León, Eduardo; Steinmetz, Lars; Warringer, Jonas; Chávez, Sebastián; Pérez-Ortín, José E.

    2016-01-01

    We analyzed 80 different genomic experiments, and found a positive correlation between both RNA polymerase II transcription and mRNA degradation with growth rates in yeast. Thus, in spite of the marked variation in mRNA turnover, the total mRNA concentration remained approximately constant. Some genes, however, regulated their mRNA concentration by uncoupling mRNA stability from the transcription rate. Ribosome-related genes modulated their transcription rates to increase mRNA levels under fast growth. In contrast, mitochondria-related and stress-induced genes lowered mRNA levels by reducing mRNA stability or the transcription rate, respectively. We also detected these regulations within the heterogeneity of a wild-type cell population growing in optimal conditions. The transcriptomic analysis of sorted microcolonies confirmed that the growth rate dictates alternative expression programs by modulating transcription and mRNA decay. The regulation of overall mRNA turnover keeps a constant ratio between mRNA decay and the dilution of [mRNA] caused by cellular growth. This regulation minimizes the indiscriminate transmission of mRNAs from mother to daughter cells, and favors the response capacity of the latter to physiological signals and environmental changes. We also conclude that, by uncoupling mRNA synthesis from decay, cells control the mRNA abundance of those gene regulons that characterize fast and slow growth. PMID:26717982

  7. The cellular growth rate controls overall mRNA turnover, and modulates either transcription or degradation rates of particular gene regulons.

    PubMed

    García-Martínez, José; Delgado-Ramos, Lidia; Ayala, Guillermo; Pelechano, Vicent; Medina, Daniel A; Carrasco, Fany; González, Ramón; Andrés-León, Eduardo; Steinmetz, Lars; Warringer, Jonas; Chávez, Sebastián; Pérez-Ortín, José E

    2016-05-05

    We analyzed 80 different genomic experiments, and found a positive correlation between both RNA polymerase II transcription and mRNA degradation with growth rates in yeast. Thus, in spite of the marked variation in mRNA turnover, the total mRNA concentration remained approximately constant. Some genes, however, regulated their mRNA concentration by uncoupling mRNA stability from the transcription rate. Ribosome-related genes modulated their transcription rates to increase mRNA levels under fast growth. In contrast, mitochondria-related and stress-induced genes lowered mRNA levels by reducing mRNA stability or the transcription rate, respectively. We also detected these regulations within the heterogeneity of a wild-type cell population growing in optimal conditions. The transcriptomic analysis of sorted microcolonies confirmed that the growth rate dictates alternative expression programs by modulating transcription and mRNA decay.The regulation of overall mRNA turnover keeps a constant ratio between mRNA decay and the dilution of [mRNA] caused by cellular growth. This regulation minimizes the indiscriminate transmission of mRNAs from mother to daughter cells, and favors the response capacity of the latter to physiological signals and environmental changes. We also conclude that, by uncoupling mRNA synthesis from decay, cells control the mRNA abundance of those gene regulons that characterize fast and slow growth.

  8. Water evaporation rates across hydrophobic acid monolayers at equilibrium spreading pressure.

    PubMed

    Tsuji, Minami; Nakahara, Hiromichi; Moroi, Yoshikiyo; Shibata, Osamu

    2008-02-15

    The effect of alkanoic acid [CH(3)(CH(2))(n-2)COOH; HCn] and perfluoroalkanoic acid [CF(3)(CF(2))(n-2)COOH; FCn] monolayers on the water evaporation rate was investigated by thermogravimetry tracing the decrease in amount of water with time. The evaporation rate from the surface covered by a monolayer was measured as a function of temperature and hydrophobic chain length of the acids, where the monolayer was under an equilibrium spreading pressure. From thermal behavior of the crystallized acids, their solid states are C-type in crystalline state over the temperature range from 298.2 to 323.2 K. The dry air was flowed through a furnace tube of a thermogravimetry apparatus at the flow rate of 80 mL min(-1), where the evaporation rate becomes almost constant irrespective of the flow rate. The temperature dependence of the evaporation rate was analyzed kinetically to evaluate the activation energy and thermodynamics values for the activated complex, which demonstrated that these values were almost the same for both alkanoic acids and perfluoroalkanoic acids, although the effect of perfluoroalkanoic acids on the evaporation rate was smaller than that of corresponding hydrogenated fatty acids. The difference in the evaporation rate between FCn and HCn was examined by atomic force microscopy (AFM), Brewster angle microscopy (BAM), surface potential (DeltaV) at equilibrium spreading pressure, and Langmuir curve (pi-A isotherm), and their results were consistent and supported the difference.

  9. Determination of degradation rates of organic substances in the unsaturated soil zone depending on the grain size fractions of various soil types

    NASA Astrophysics Data System (ADS)

    Fichtner, Thomas; Stefan, Catalin; Goersmeyer, Nora

    2015-04-01

    Rate and extent of the biological degradation of organic substances during transport through the unsaturated soil zone is decisively influenced by the chemical and physical properties of the pollutants such as water solubility, toxicity and molecular structure. Furthermore microbial degradation processes are also influenced by soil-specific properties. An important parameter is the soil grain size distribution on which the pore volume and the pore size depends. Changes lead to changes in air and water circulation as well as preferred flow paths. Transport capacity of water inclusive nutrients is lower in existing bad-drainable fine pores in soils with small grain size fractions than in well-drainable coarse pores in a soil with bigger grain size fractions. Because fine pores are saturated with water for a longer time than the coarse pores and oxygen diffusion in water is ten thousand times slower than in air, oxygen is replenished much slower in soils with small grain size fractions. As a result life and growth conditions of the microorganisms are negatively affected. This leads to less biological activity, restricted degradation/mineralization of pollutants or altered microbial processes. The aim of conducted laboratory column experiments was to study the correlation between the grain size fractions respectively pore sizes, the oxygen content and the biodegradation rate of infiltrated organic substances. Therefore two columns (active + sterile control) were filled with different grain size fractions (0,063-0,125 mm, 0,2-0,63 mm and 1-2 mm) of soils. The sterile soil was inoculated with a defined amount of a special bacteria culture (sphingobium yanoikuae). A solution with organic substances glucose, oxalic acid, sinaphylic alcohol and nutrients was infiltrated from the top in intervals. The degradation of organic substances was controlled by the measurement of dissolved organic carbon in the in- and outflow of the column. The control of different pore volumes

  10. Heterogeneous photo-Fenton degradation of acid red B over Fe2O3 supported on activated carbon fiber.

    PubMed

    Lan, Huachun; Wang, Aiming; Liu, Ruiping; Liu, Huijuan; Qu, Jiuhui

    2015-03-21

    Fe2O3 supported on activated carbon fiber (Fe2O3/ACF) was prepared via an impregnation method and characterized by X-ray diffraction, scanning electron microscopy and BET analysis. The results indicated that Fe2O3 with small particle size was highly dispersed on the surface of the ACF and the introduction of Fe2O3 did not change the ACF pore structure. Fe2O3/ACF exhibited a higher Fenton efficiency for the degradation of acid red B (ARB), especially under simulated solar irradiation. Complete decoloration of the ARB solution and 43% removal of TOC could be achieved within 200 min under optimal conditions. It was verified that more ˙OH radicals were generated in the photo-assisted Fenton process and involved as active species in ARB degradation. FTIR analysis indicated that the degradation of ARB was initiated through the cleavage of -N=N-, followed by hydroxylation and opening of phenyl rings to form aliphatic acids, and further oxidation of aliphatic acids would produce CO2 and H2O. Moreover, Fe2O3/ACF maintained its activity after being reused 4 times and the release of iron from the catalyst was found to be insignificant during the Fenton and photo-Fenton processes, indicating that Fe2O3/ACF had good long-term stability.

  11. Radical-driven carbonyl-to-acid conversion and acid degradation in tropospheric aqueous systems studied by CAPRAM

    NASA Astrophysics Data System (ADS)

    Tilgner, A.; Herrmann, H.

    2010-12-01

    Model studies on the aqueous phase radical-driven processing of carbonyl compounds and acids in clouds and deliquescent particles were performed. The model exposed that aqueous radical conversions of carbonyl compounds and its oxidation products can contribute potentially to the formation of functionalised organic acids. The main identified C 2-C 4 organic gas phase precursors are ethylene glycol, glycolaldehyde, glyoxal, methylglyoxal and 1,4-butenedial. The aqueous phase is shown to contribute significantly with about 93%/63%, 47%/8%, 31%/4%, 7%/4%, 36%/8% to the multiphase oxidative fate of these compounds under remote/urban conditions. Interestingly, the studies revealed that aqueous chemical processing is not only limited to in-cloud conditions but also proceeds in deliquescent particle phase with significant fluxes. Oxalic acid is shown to be formed preferably in deliquescent particles subsequent to the in-cloud oxidations. Mean aqueous phase oxalate formation fluxes of about 12, 42 and 0.4 ng m -3 h -1 in the remote, urban and maritime scenario, respectively. Additionally, the turnovers of the oxidation of organics such as methylglyoxal by NO 3 radical reactions are identified to be competitive to their OH pendants. At the current state of CAPRAM, mean C 2-C 4 in-cloud oxidation fluxes of about 0.12 and 0.5 μg m -3 h -1 are modelled under the idealised remote and urban cloud conditions. Finally, turnovers from radical oxidations were compared with those of thermal reactions. It is demonstrated that, based on the sparse kinetic data available organic accretion reaction might be of interest in just a few cases for cloud droplets and aqueous particles but generally do not reach the oxidative conversion rates of the main radical oxidants OH and NO 3. Interestingly, oxidation reactions of H 2O 2 are shown to be competitive to the OH radical conversions in cases when H 2O 2 is not readily used up by the S(IV) oxidation.

  12. Effect of pyrolysis temperature on composition, surface properties and thermal degradation