Science.gov

Sample records for anaerobic conditions improve

  1. Anaerobic conditions improve germination of a gibberellic acid deficient rice

    NASA Technical Reports Server (NTRS)

    Frantz, Jonathan M.; Bugbee, Bruce

    2002-01-01

    Dwarf plants are useful in research because multiple plants can be grown in a small area. Rice (Oryza sativa L.) is especially important since its relatively simple genome has recently been sequenced. We are characterizing a gibberellic acid (GA) mutant of rice (japonica cv 'Shiokari,' line N-71) that is extremely dwarf (20 cm tall). Unfortunately, this GA mutation is associated with poor germination (70%) under aerobic conditions. Neither exogenous GA nor a dormancy-breaking heat treatment improved germination. However, 95% germination was achieved by germinating the seeds anaerobically, either in a pure N2 environment or submerged in unstirred tap water. The anaerobic conditions appear to break a mild post-harvest dormancy in this rice cultivar. Copyright 2002 Crop Science Society of America.

  2. Anaerobic conditions improve germination of a gibberellic acid deficient rice

    NASA Technical Reports Server (NTRS)

    Frantz, Jonathan M.; Bugbee, Bruce

    2002-01-01

    Dwarf plants are useful in research because multiple plants can be grown in a small area. Rice (Oryza sativa L.) is especially important since its relatively simple genome has recently been sequenced. We are characterizing a gibberellic acid (GA) mutant of rice (japonica cv 'Shiokari,' line N-71) that is extremely dwarf (20 cm tall). Unfortunately, this GA mutation is associated with poor germination (70%) under aerobic conditions. Neither exogenous GA nor a dormancy-breaking heat treatment improved germination. However, 95% germination was achieved by germinating the seeds anaerobically, either in a pure N2 environment or submerged in unstirred tap water. The anaerobic conditions appear to break a mild post-harvest dormancy in this rice cultivar. Copyright 2002 Crop Science Society of America.

  3. Directed evolution of a cellodextrin transporter for improved biofuel production under anaerobic conditions in Saccharomyces cerevisiae.

    PubMed

    Lian, Jiazhang; Li, Yanglin; HamediRad, Mohammad; Zhao, Huimin

    2014-08-01

    Introduction of a cellobiose utilization pathway consisting of a cellodextrin transporter and a β-glucosidase into Saccharomyces cerevisiae enables co-fermentation of cellobiose and xylose. Cellodextrin transporter 1 (CDT1) from Neurospora crassa has been established as an effective transporter for the engineered cellobiose utilization pathways. However, cellodextrin transporter 2 (CDT2) from the same species is a facilitator and has the potential to be more efficient than CDT1 under anaerobic conditions due to its energetic benefits. Currently, CDT2 has a very low activity and is considered rate-limiting in cellobiose fermentation. Here, we report the directed evolution of CDT2 with an increased cellobiose uptake activity, which results in improved cellobiose fermentation under anaerobic conditions. After three rounds of directed evolution, the cellobiose uptake activity of CDT2 was increased by 2.2-fold, which resulted from both increased specific activity and transporter expression level. Using high cell density fermentation under anaerobic conditions, the evolved mutant conferred 4.0- and 4.4-fold increase in the cellobiose consumption rate and ethanol productivity, respectively. In addition, although the cellobiose uptake activity was still lower than that of CDT1, the engineered CDT2 showed significantly improved cellobiose consumption and ethanol production under anaerobic conditions, representing the energetic benefits of a sugar facilitator for anaerobic cellobiose fermentation. This study demonstrated that anaerobic biofuel production could be significantly improved via directed evolution of a sugar transporter protein in yeast.

  4. The metabolic costs of improving ethanol yield by reducing glycerol formation capacity under anaerobic conditions in Saccharomyces cerevisiae

    PubMed Central

    2013-01-01

    Background Finely regulating the carbon flux through the glycerol pathway by regulating the expression of the rate controlling enzyme, glycerol-3-phosphate dehydrogenase (GPDH), has been a promising approach to redirect carbon from glycerol to ethanol and thereby increasing the ethanol yield in ethanol production. Here, strains engineered in the promoter of GPD1 and deleted in GPD2 were used to investigate the possibility of reducing glycerol production of Saccharomyces cerevisiae without jeopardising its ability to cope with process stress during ethanol production. For this purpose, the mutant strains TEFmut7 and TEFmut2 with different GPD1 residual expression were studied in Very High Ethanol Performance (VHEP) fed-batch process under anaerobic conditions. Results Both strains showed a drastic reduction of the glycerol yield by 44 and 61% while the ethanol yield improved by 2 and 7% respectively. TEFmut2 strain showing the highest ethanol yield was accompanied by a 28% reduction of the biomass yield. The modulation of the glycerol formation led to profound redox and energetic changes resulting in a reduction of the ATP yield (YATP) and a modulation of the production of organic acids (acetate, pyruvate and succinate). Those metabolic rearrangements resulted in a loss of ethanol and stress tolerance of the mutants, contrarily to what was previously observed under aerobiosis. Conclusions This work demonstrates the potential of fine-tuned pathway engineering, particularly when a compromise has to be found between high product yield on one hand and acceptable growth, productivity and stress resistance on the other hand. Previous study showed that, contrarily to anaerobiosis, the resulting gain in ethanol yield was accompanied with no loss of ethanol tolerance under aerobiosis. Moreover those mutants were still able to produce up to 90 gl-1 ethanol in an anaerobic SSF process. Fine tuning metabolic strategy may then open encouraging possibilities for further

  5. Accelerated anaerobic hydrolysis rates under a combination of intermittent aeration and anaerobic conditions.

    PubMed

    Jensen, T R; Lastra Milone, T; Petersen, G; Andersen, H R

    2017-04-01

    Anaerobic hydrolysis in activated return sludge was investigated in laboratory scale experiments to find if intermittent aeration would accelerate anaerobic hydrolysis rates compared to anaerobic hydrolysis rates under strict anaerobic conditions. The intermittent reactors were set up in a 240 h experiment with intermittent aeration (3 h:3 h) in a period of 24 h followed by a subsequent anaerobic period of 24 h in a cycle of 48 h which was repeated five times during the experiment. The anaerobic reactors were kept under strict anaerobic conditions in the same period (240 h). Two methods for calculating hydrolysis rates based on soluble chemical oxygen demand were compared. Two-way analysis of variance with the Bonferroni post-test was performed in order to register any significant difference between reactors with intermittent aeration and strictly anaerobic conditions respectively. The experiment demonstrated a statistically significant difference in favor of the reactors with intermittent aeration showing a tendency towards accelerated anaerobic hydrolysis rates due to application of intermittent aeration. The conclusion of the work is thus that intermittent aeration applied in the activated return sludge process can improve the treatment capacity further in full scale applications.

  6. Unsaturated fatty acids from food and in the growth medium improve growth of Bacillus cereus under cold and anaerobic conditions.

    PubMed

    de Sarrau, Benoît; Clavel, Thierry; Zwickel, Nicolas; Despres, Jordane; Dupont, Sébastien; Beney, Laurent; Tourdot-Maréchal, Raphaëlle; Nguyen-The, Christophe

    2013-12-01

    In a chemically defined medium and in Luria broth, cold strongly reduced maximal population density of Bacillus cereus ATCC 14579 in anaerobiosis and caused formation of filaments. In cooked spinach, maximal population density of B. cereus in anaerobiosis was the same at cold and optimal temperatures, with normal cell divisions. The lipid containing fraction of spinach, but not the hydrophilic fraction, restored growth of B. cereus under cold and anaerobiosis when added to the chemically defined medium. This fraction was rich in unsaturated, low melting point fatty acids. Addition of phosphatidylcholine containing unsaturated, low melting point, fatty acids similarly improved B. cereus anaerobic growth at cold temperature. Addition of hydrogenated phosphatidylcholine containing saturated, high melting point, fatty acids did not modify growth. Fatty acids from phospholipids, from spinach and from hydrogenated phosphatidylcholine, although normally very rare in B. cereus, were inserted in the bacterium membrane. Addition of phospholipids rich in unsaturated fatty acids to cold and anaerobic cultures, increased fluidity of B. cereus membrane lipids, to the same level as those from B. cereus normally cold adapted, i.e. grown aerobically at 15 °C. B. cereus is therefore able to use external fatty acids from foods or from the growth medium to adapt its membrane to cold temperature under anaerobiosis, and to recover the maximal population density achieved at optimal temperature.

  7. Improvement of anaerobic digestion of sludge.

    PubMed

    Dohányos, M; Zábranská, J; Kutil, J; Jenícek, P

    2004-01-01

    Anaerobic digestion improvement can be accomplished by different methods. Besides optimization of the process conditions, pretreatment of input sludge and increase of process temperature is frequently used. The thermophilic process brings a higher solids reduction and biogas production, a high resistance to foaming, no problems with odour, better pathogens destruction and an improvement of the energy balance of the whole treatment plant. Disintegration of excess activated sludge in a lysate centrifuge was proved to cause increase of biogas production in full-scale conditions. The rapid thermal conditioning of digested sludge is an acceptable method of particulate matter disintegration and solubilization.

  8. The anaerobic endurance of elite soccer players improved after a high-intensity training intervention in the 8-week conditioning program.

    PubMed

    Sporis, Goran; Ruzic, Lana; Leko, Goran

    2008-03-01

    The purpose of this study was to evaluate changes in anaerobic endurance in elite First-league soccer players throughout 2 consecutive seasons, in 2 phases, with and without high-intensity situational drills. Eighteen soccer players were tested before and after the 8-week summer conditioning and again in the next season. The measured variables included 300-yard shuttle run test, maximal heart rate, and maximal blood lactate at the end of the test. During the first phase of the study, the traditional sprint training was performed only 2 x weeks and consisted of 15 bouts of straight-line sprinting. In the second year the 4 x 4 min drills at an intensity of 90-95% of HRmax, separated by periods of 3-minute technical drills at 55-65% of HRmax were introduced. Statistical significance was set at P conditioning program conducted during the first year of the study did not elicit an improvement in anaerobic endurance as recorded in the 300-yard shuttle run test. After the intervention, the overall test running time improved significantly (55.74 +/- 1.63 s vs. 56.99 +/- 1.64 s; P < 0.05) with the maximal blood lactate at the end of the test significantly greater (15.4 +/- 1.23 mmol.L vs. 13.5 +/- 1.12 mmol.L. P < 0.01). As a result, this study showed some indication that situational high-intensity task training was more efficient than straight-line sprinting in improving anaerobic endurance measured by the 300-yard shuttle run test.

  9. Constitutive expression of Campylobacter jejuni truncated hemoglobin CtrHb improves the growth of Escherichia coli cell under aerobic and anaerobic conditions.

    PubMed

    Yang, Jiang-Ke; Xiong, Wei; Xu, Li; Li, Jia; Zhao, Xiu-Ju

    2015-01-01

    Bacteria hemoglobin could bind to the oxygen, transfer it from the intracellular microenvironment to the respiration process and sustain the energy for the metabolism and reproduction of cells. Heterologous expression of bacteria hemoglobin gene could improve the capacity of the host on oxygen-capturing and allow it to grow even under microaerophilic condition. To develop a system based on hemoglobin to help bacteria cells overcome the oxygen shortage in fermentation, in this study, Campylobacter jejuni truncated hemoglobin (CtrHb) gene was synthesized and expressed under the control of constitutive expression promoters P2 and P(SPO1-II) in Escherichia coli. As showed by the growth curves of the two recombinants P2-CtrHb and P(SPO1-II)-CtrHb, constitutive expression of CtrHb improved cell growth under aerobic shaking-flasks, anaerobic capped-bottles and bioreactor conditions. According to the NMR analysis, this improvement might come from the expression of hemoglobin which could boost the metabolism of cells by supplying more oxygen to the respiratory chain processes. Through semi-quantitative RT-PCR and CO differential spectrum assays, we further discussed the connection between the growth patterns of the recombinants, the expression level of CtrHb and oxygen binding capacity of CtrHb in cells. Based on the growth patterns of these recombinants in bioreactor, a possible choice on different type of recombinants under specific fermentation conditions was also suggested in this study.

  10. PCB biohalogenation under anaerobic conditions

    SciTech Connect

    Gauger, W.K.; McCue, J.J.

    1990-01-01

    The Institute of Gas Technology (IGT) is conducting research on the biodehalogenation of polychlorinated biphenyls (PCB's) under anoxic conditions. Reductive dechlorination of PCB's has been observed in treatments inoculated with Hudson River sediments. Differences in gas chromatograms between time 0 and 4-month incubations indicate pattern shifts of the PCB homologs that constitute Aroclor 1242 from highly chlorinated to lesser chlorinated congeners. Changes in distribution patterns of PCB homologs were also evident. PCB homologs containing 4, 5, 6, and 7 chlorine atoms were shown to decrease over the incubation period, whereas PCB homologs containing 2 and 3 chlorines increased in concentration. 10 refs., 5 figs., 1 tab.

  11. Anaerobic biodegradation of cyanide under methanogenic conditions

    SciTech Connect

    Fallon, R.D.; Cooper, D.A.; Henson, M. ); Speece, R. )

    1991-06-01

    Upflow, anaerobic, fixed-bed, activated charcoal biotreatment columns capable of operating at free cyanide concentrations of {gt}100 mg liter{sup {minus}1} with a hydraulic retention time of {lt}48 h were developed. Methanogenesis was maintained under a variety of feed medium conditions which included ethanol, phenol, or methanol as the primary reduced carbon source. Under optimal conditions, {gt}70% of the inflow free cyanide was removed in the first 30% of the column height. Strongly complexed cyanides were resistant to removal. Ammonia was the nitrogen end product of cyanide transformation. In cell material removed from the charcoal columns, ({sup 14}C) bicarbonate was the major carbon end product of ({sup 14}C) cyanide transformation.

  12. Anaerobic biodegradation of cyanide under methanogenic conditions.

    PubMed Central

    Fallon, R D; Cooper, D A; Speece, R; Henson, M

    1991-01-01

    Upflow, anaerobic, fixed-bed, activated charcoal biotreatment columns capable of operating at free cyanide concentrations of greater than 100 mg liter-1 with a hydraulic retention time of less than 48 h were developed. Methanogenesis was maintained under a variety of feed medium conditions which included ethanol, phenol, or methanol as the primary reduced carbon source. Under optimal conditions, greater than 70% of the inflow free cyanide was removed in the first 30% of the column height. Strongly complexed cyanides were resistant to removal. Ammonia was the nitrogen end product of cyanide transformation. In cell material removed from the charcoal columns, [14C]bicarbonate was the major carbon end product of [14C]cyanide transformation. PMID:1872600

  13. A new approach for concurrently improving performance of South Korean food waste valorization and renewable energy recovery via dry anaerobic digestion under mesophilic and thermophilic conditions.

    PubMed

    Nguyen, Dinh Duc; Yeop, Jeong Seong; Choi, Jaehoon; Kim, Sungsu; Chang, Soon Woong; Jeon, Byong-Hun; Guo, Wenshan; Ngo, Huu Hao

    2017-08-01

    Dry semicontinuous anaerobic digestion (AD) of South Korean food waste (FW) under four solid loading rates (SLRs) (2.30-9.21kg total solids (TS)/m(3)day) and at a fixed TS content was compared between two digesters, one each under mesophilic and thermophilic conditions. Biogas production and organic matter reduction in both digesters followed similar trends, increasing with rising SLR. Inhibitor (intermediate products of the anaerobic fermentation process) effects on the digesters' performance were not observed under the studied conditions. In all cases tested, the digesters' best performance was achieved at the SLR of 9.21kg TS/m(3)day, with 74.02% and 80.98% reduction of volatile solids (VS), 0.87 and 0.90m(3) biogas/kg VSremoved, and 0.65 (65% CH4) and 0.73 (60.02% CH4) m(3) biogas/kg VSfed, under mesophilic and thermophilic conditions, respectively. Thermophilic dry AD is recommended for FW treatment in South Korea because it is more efficient and has higher energy recovery potential when compared to mesophilic dry AD. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Potential of hydrolysis of particulate COD in extended anaerobic conditions to enhance biological phosphorous removal.

    PubMed

    Jabari, P; Yuan, Q; Oleszkiewicz, J A

    2016-11-01

    The effect of anaerobic hydrolysis of particulate COD (pCOD) on biological phosphorous removal in extended anaerobic condition was investigated through (i) sequencing batch reactors (SBR)s with anaerobic hydraulic retention time (HRT) of 0.8, 2, and 4 h; (ii) batch tests using biomass from a full scale biological nutrient removal (BNR) plant; and (iii) activated sludge modeling (BioWin 4.1 simulation). The results from long-term SBRs operation showed that phosphorus removal was correlated to the ratio of filtered COD (FCOD) to total phosphorus (TP) in the influent. Under conditions with low FCOD/TP ratio (average of 20) in the influent, extending anaerobic HRT to 4 h in the presence of pCOD did not significantly improve overall phosphorous removal. During the period with high FCOD/TP ratio (average of 37) in the influent, all SBRs removed phosphorous completely, and the long anaerobic HRT did not have negative effect on overall phosphorous removal. The batch tests also showed that pCOD at different concentration during 4 h test did not affect the rate of anaerobic phosphorus release. The rate of anaerobic hydrolysis of pCOD was significantly low and extending the anaerobic HRT was ineffective. The simulation (BioWin 4.1) of SBRs with low influent FCOD/TP ratio showed that the default kinetics of anaerobic hydrolysis in ASM2d overestimated phosphorous removal in the SBRs (high anaerobic hydrolysis of pCOD). The default anaerobic hydrolysis rate in BioWin 4.1 (ten times lower) could produce similar phosphorous removal to that in the experiment. Results showed that the current kinetics of anaerobic hydrolysis in ASM2d could lead to considerable error in predicting phosphorus removal in processes with extended anaerobic HRT. Biotechnol. Bioeng. 2016;113: 2377-2385. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  15. Improve bio-activity of anaerobic sludge by low energy ultrasound.

    PubMed

    Zhu, Yichun; Li, Xin; Du, Maoan; Liu, Zuwen; Luo, Hui; Zhang, Tao

    2015-01-01

    This research focused on ultrasound-enhanced bio-activity of anaerobic sludge. Low energy ultrasound irradiation can increase the bio-activity of anaerobic sludge. Ultrasonic parameter, characteristics of anaerobic sludge and experimental conditions are important parameters which affect the enhancement effect on anaerobic sludge. In order to assess the effects of characteristics of anaerobic sludge and experimental conditions on ultrasonic irradiation of anaerobic sludge, experiments with different characteristics of anaerobic sludge were carried out and analyzed with the content of coenzyme F420 and dehydrogenase activity (DHA). The results showed that anaerobic sludge bio-activity was impacted by the initial temperature, initial chemical oxygen demand (COD), sludge concentration, and stirring during the ultrasonic process. Optimal performance was achieved when sound frequency, power density, and ultrasonic irradiation period was 20 kHz, 0.1 W/mL, and 10 min, respectively, under which the wastewater COD removal efficiency was increased by 12.9 percentage points. The results indicated that low temperature could affect the anaerobic sludge irradiation effect, while intermittent stirring could enhance the bio-activity of anaerobic sludge irradiation effect and low substrate concentration improved anaerobic sludge activity by ultrasound.

  16. Improving products of anaerobic sludge digestion by microaeration.

    PubMed

    Jenicek, P; Celis, C A; Krayzelova, L; Anferova, N; Pokorna, D

    2014-01-01

    Biogas, digested sludge and sludge liquor are the main products of anaerobic sludge digestion. Each of the products is influenced significantly by specific conditions of the digestion process. Therefore, any upgrade of the digestion technology must be considered with regard to quality changes in all products. Microaeration is one of the methods used for the improvement of biogas quality. Recently, microaeration has been proved to be a relatively simple and highly efficient biological method of sulfide removal in the anaerobic digestion of biosolids, but little attention has been paid to comparing the quality of digested sludge and sludge liquor in the anaerobic and microaerobic digestion and that is why this paper primarily deals with this area of research. The results of the long-term monitoring of digested sludge quality and sludge liquor quality in the anaerobic and microaerobic digesters suggest that products of both technologies are comparable. However, there are several parameters in which the 'microaerobic' products have a significantly better quality such as: sulfide (68% lower) and soluble chemical oxygen demand (COD) (33% lower) concentrations in the sludge liquor and the lower foaming potential of the digested sludge.

  17. Antimicrobial Susceptibility of Enteric Gram Negative Facultative Anaerobe Bacilli in Aerobic versus Anaerobic Conditions

    PubMed Central

    Amachawadi, Raghavendra G.; Renter, David G.; Volkova, Victoriya V.

    2016-01-01

    Antimicrobial treatments result in the host’s enteric bacteria being exposed to the antimicrobials. Pharmacodynamic models can describe how this exposure affects the enteric bacteria and their antimicrobial resistance. The models utilize measurements of bacterial antimicrobial susceptibility traditionally obtained in vitro in aerobic conditions. However, in vivo enteric bacteria are exposed to antimicrobials in anaerobic conditions of the lower intestine. Some of enteric bacteria of food animals are potential foodborne pathogens, e.g., Gram-negative bacilli Escherichia coli and Salmonella enterica. These are facultative anaerobes; their physiology and growth rates change in anaerobic conditions. We hypothesized that their antimicrobial susceptibility also changes, and evaluated differences in the susceptibility in aerobic vs. anaerobic conditions of generic E. coli and Salmonella enterica of diverse serovars isolated from cattle feces. Susceptibility of an isolate was evaluated as its minimum inhibitory concentration (MIC) measured by E-Test® following 24 hours of adaptation to the conditions on Mueller-Hinton agar, and on a more complex tryptic soy agar with 5% sheep blood (BAP) media. We considered all major antimicrobial drug classes used in the U.S. to treat cattle: β-lactams (specifically, ampicillin and ceftriaxone E-Test®), aminoglycosides (gentamicin and kanamycin), fluoroquinolones (enrofloxacin), classical macrolides (erythromycin), azalides (azithromycin), sulfanomides (sulfamethoxazole/trimethoprim), and tetracyclines (tetracycline). Statistical analyses were conducted for the isolates (n≥30) interpreted as susceptible to the antimicrobials based on the clinical breakpoint interpretation for human infection. Bacterial susceptibility to every antimicrobial tested was statistically significantly different in anaerobic vs. aerobic conditions on both media, except for no difference in susceptibility to ceftriaxone on BAP agar. A satellite experiment

  18. Degradation of natural and synthetic polyesters under anaerobic conditions.

    PubMed

    Abou-Zeid, D M; Müller, R J; Deckwer, W D

    2001-03-30

    Often, degradability under anaerobic conditions is desirable for plastics claimed to be biodegradable, e.g. in anaerobic biowaste treatment plants, landfills and in natural anaerobic sediments. The biodegradation of the natural polyesters poly(beta-hydroxybutyrate) (PHB), poly(beta-hydroxybutyrate-co-11.6%-beta-hydroxyvalerate) (PHBV) and the synthetic polyester poly(epsilon-caprolactone) (PCL) was studied in two anaerobic sludges and individual polyester degrading anaerobic strains were isolated, characterized and used for degradation experiments under controlled laboratory conditions. Incubation of PHB and PHBV films in two anaerobic sludges exhibited significant degradation in a time scale of 6-10 weeks monitored by weight loss and biogas formation. In contrast to aerobic conditions, PHB was degraded anaerobically more rapidly than the copolyester PHBV, when tested with either mixed cultures or a single strained isolate. PCL tends to degrade slower than the natural polyesters PHB and PHBV. Four PHB and PCL degrading isolates were taxonomically identified and are obviously new species belonging to the genus Clostridium group I. The depolymerizing enzyme systems of PHB and PCL degrading isolates are supposed to be different. Using one isolated strain in an optimized laboratory degradation test with PHB powder, the degradation time was drastically reduced compared to the degradation in sludges (2 days vs. 6-10 weeks).

  19. Decomposition of organic waste products under aerobic and anaerobic conditions

    SciTech Connect

    Gale, P.M.

    1988-01-01

    The objectives of this research were to determine the kinetics of C and N mineralization under aerobic and anaerobic conditions. These parameters were then used to verify the simulation model, DECOMPOSITION, for the anaerobic system. Incubation experiments were conducted to compare the aerobic and anaerobic decomposition of alfalfa (Medicago sativa L.), a substrate with a low C:N ratio. Under anaerobic conditions the net mineralization of N occurred more rapidly than that under aerobic conditions. However, the rate of C mineralization as measured by CO{sub 2} evolution was much lower. For the anaerobic decomposition of alfalfa, C mineralization was best described as the sum of the CO{sub 2} and CH{sub 4} evolved plus the water soluble organic C formed. The kinetics of C mineralization, as determined by this approach, were used to successfully predict the rate and amount of N mineralization from alfalfa undergoing anaerobic decomposition. The decomposition of paper mill sludge, a high C:N ratio substrate, was also evaluated.

  20. Anaerobic incubation conditions enhance pyrazinamide activity against Mycobacterium tuberculosis.

    PubMed

    Wade, Mary Margaret; Zhang, Ying

    2004-08-01

    Pyrazinamide (PZA) is an unconventional front line tuberculosis drug characterized by high in vivo sterilizing activity, but poor in vitro activity. This disparity in PZA activity may reflect differences between the in vivo tissue environment and in vitro culture conditions. This study examined the effect of anaerobic conditions, which exist in granulomatous lesions in vivo, on PZA activity in vitro. Low oxygen enhanced the activity of PZA against Mycobacterium tuberculosis, with anaerobic conditions resulting in greater enhancement than microaerobic conditions. ATPase and respiratory chain enzyme inhibitors enhanced PZA activity under normal atmospheric conditions, but not under anaerobic conditions. Furthermore, the inhibitors did not enhance isoniazid or rifampicin activity. Nitrate as an alternative electron acceptor antagonized PZA activity under anaerobic conditions. These findings provide further support for a proposed mechanism of action of PZA in which the active form of PZA (pyrazinoic acid) depletes the membrane energy reserve. They also provide another explanation for the higher sterilizing activity of PZA within in vivo lesions with low oxygen than under in vitro drug susceptibility testing conditions with ambient oxygen.

  1. Engineered microorganisms capable of producing target compounds under anaerobic conditions

    DOEpatents

    Buelter, Thomas [Denver, CO; Meinhold, Peter [Denver, CO; Feldman, Reid M. Renny [San Francisco, CA; Hawkins, Andrew C [Parker, CO; Urano, Jun [Irvine, CA; Bastian, Sabine [Pasadena, CA; Arnold, Frances [La Canada, CA

    2012-01-17

    The present invention is generally provides recombinant microorganisms comprising engineered metabolic pathways capable of producing C3-C5 alcohols under aerobic and anaerobic conditions. The invention further provides ketol-acid reductoisomerase enzymes which have been mutated or modified to increase their NADH-dependent activity or to switch the cofactor preference from NADPH to NADH and are expressed in the modified microorganisms. In addition, the invention provides isobutyraldehyde dehydrogenase enzymes expressed in modified microorganisms. Also provided are methods of producing beneficial metabolites under aerobic and anaerobic conditions by contacting a suitable substrate with the modified microorganisms of the present invention.

  2. Degradation of toxaphene in water during anaerobic and aerobic conditions.

    PubMed

    LacayoR, M; van Bavel, B; Mattiasson, B

    2004-08-01

    The degradation of technical toxaphene in water with two kinds of bioreactors operating in sequence was studied. One packed bed reactor was filled with Poraver (foam glass particles) running at anaerobic conditions and one suspended carrier biofilm reactor working aerobically. Chemical oxygen demand (COD), chloride, sulphate, pH, dissolved oxygen, total toxaphene and specific toxaphene isomers were measured. After 6 weeks approx. 87% of the total toxaphene was degraded reaching 98% by week 39. The majority of the conversion took place in the anaerobic reactor. The concentrations of toxaphene isomers with more chlorine substituents decreased more rapidly than for isomers with less chlorine substituents.

  3. DEVELOPMENT OF IMPROVED ANAEROBIC GROWTH OF BACILLUS MOJAVENSIS STRAIN JF-2 FOR THE PURPOSE OF IMPROVED ANAEROBIC BIOSURFACTANT PRODUCTION FOR ENHANCED OIL RECOVERY

    SciTech Connect

    M.J. McInerney; M. Folmsbee; D. Nagle

    2004-05-31

    Our work focuses on the use of microorganisms to recover petroleum hydrocarbons that remain entrapped after current recovery technologies reach their economic limit. Capillary forces between the hydrocarbon and aqueous phases are largely responsible for trapping the hydrocarbons in the pores of the rock and large reductions in the interfacial tension between the hydrocarbon and aqueous phases are needed for hydrocarbon mobilization (1-3, 10, 11). Microorganisms produce a variety of biosurfactants (4), several of which generate the ultra low interfacial tensions needed for hydrocarbon mobilization (4, 5, 8). In particular, the lipopeptide biosurfactant produced by Bacillus mojavensis strain JF-2 reduces the interfacial tension between hydrocarbon and aqueous phases to very low levels (<0.016 mN/m) (8) (9). B. mojavensis JF-2 grows under the environmental conditions found in many oil reservoirs, i. e., anaerobic, NaCl concentrations up to 80 g l{sup -1}, and temperatures up to 45 C (6, 7), making it ideally suited for in situ applications. However, anaerobic growth of B. mojavensis JF-2 was inconsistent and difficult to replicate, which limited its use for in situ applications. Our initial studies revealed that enzymatic digests, such as Proteose Peptone, were required for anaerobic growth of Bacillus mojavensis JF-2. Subsequent purification of the growth-enhancing factor in Proteose Peptone resulted in the identification of the growth-enhancing factor as DNA or deoxyribonucleosides. The addition of salmon sperm DNA, herring sperm DNA, E. coli DNA or synthetic DNA (single or double stranded) to Medium E all supported anaerobic growth of JF-2. Further, we found that JF-2 required all four deoxyribonucleosides (deoxyadeonosine, deoxyguanosine, deoxycytidine and thymidine) for growth under strict anaerobic conditions. The requirement for the deoxyribonucleosides did not occur under aerobic growth conditions. DNA was not used as a sole energy source; sucrose was required

  4. Decolorization of azo dyes under batch anaerobic and sequential anaerobic/aerobic conditions.

    PubMed

    Işik, Mustafa; Sponza, Delia Teresa

    2004-01-01

    Batch anaerobic and sequential anaerobic upflow anaerobic sludge blanket (UASB)/aerobic continuous stirred tank reactor (CSTR) were used to determine the color and COD removals under anaerobic/aerobic conditions. Two azo dyes namely "Reactive Black 5 (RB 5)," "Congo Red (CR)," and glucose as a carbon source were used for synthetic wastewater. The course of the decolorization process approximates to first order and zero order kinetics with respect to dye concentration for RB 5 and Congo Red azo dyes, respectively, in batch conditions. The decolorization kinetic constant (K0) values increased from 3.6 to 11.8 mg(L h)(-1) as increases in dye concentrations from 200 to 3200 mg L(-1) for CR. Increases in dye concentrations from 0 to 3200 mg L(-1) reduce the decolorization rate constant (k1) values from 0.0141 to 0.0019 h(-1) in batch studies performed with RB 5. Decolorization was achieved effectively under test conditions but ultimate decolorization of azo dyes was not observed at all dye concentrations in batch assay conditions. Dye concentrations of 100 mg L(-1) and 3000 mg L(-1) of glucose-COD containing basal medium were used for continuous studies. The effect of organic loadings and HRT, on the color removal efficiencies and methane gas productions were monitored. 94.1-45.4% COD and 79-73% color removal efficiencies were obtained at an organic system during decolorization of Reactive Black 5. 92.3-77.0% COD and 95.3-92.2% decolorization efficiencies were achieved at a organic loading rate of 1.03-6.65 kg (m3 day)(-1) and a HRT of 3.54-0.49 for Congo Red treatment. The results of this study showed that, although decolorization continued, COD removal efficiencies and methane gas production were depressed at high organic loadings under anaerobic conditions. Furthermore, VFA accumulation, alkalinity consumption, and methane gas percentage were monitored at organic loading as high as 2.49-4.74 kg (m3 day)(-1) and 24.60-30.62 kg (m3 day)(-1), respectively, through the

  5. Degradation of triclosan under aerobic, anoxic, and anaerobic conditions.

    PubMed

    Gangadharan Puthiya Veetil, Prajeesh; Vijaya Nadaraja, Anupama; Bhasi, Arya; Khan, Sudheer; Bhaskaran, Krishnakumar

    2012-07-01

    Triclosan (2, 4, 4'-trichloro-2'-hydroxyl diphenyl ether) is a broad-spectrum antimicrobial agent present in a number of house hold consumables. Aerobic and anaerobic enrichment cultures tolerating triclosan were developed and 77 bacterial strains tolerating triclosan at different levels were isolated from different inoculum sources. Biodegradation of triclosan under aerobic, anoxic (denitrifying and sulphate reducing conditions), and anaerobic conditions was studied in batch cultures with isolated pure strains and enrichment consortium developed. Under aerobic conditions, the isolated strains tolerated triclosan up to 1 g/L and degraded the compound in inorganic-mineral-broth and agar media. At 10 mg/L level triclosan, 95 ± 1.2% was degraded in 5 days, producing phenol, catechol and 2, 4-dichlorophenol as the degradation products. The strains were able to metabolize triclosan and its degradation products in the presence of monooxygenase inhibitor 1-pentyne. Under anoxic/anaerobic conditions highest degradation (87%) was observed in methanogenic system with acetate as co-substrate and phenol, catechol, and 2, 4-dichlorophenol were among the products. Three of the isolated strains tolerating 1 g/L triclosan were identified as Pseudomonas sp. (BDC 1, 2, and 3).

  6. Anaerobic

    MedlinePlus

    ... more prolonged exercise like walking or jogging. Anaerobic reactions are faster. We need them during shorter, more intense activities like sprinting. Anaerobic exercise leads to a buildup of lactic acid in our tissues. We need oxygen to remove ...

  7. The Effects of Desiccation on Methanogens Under Aerobic and Anaerobic Conditions

    NASA Astrophysics Data System (ADS)

    Murphy, C.; Kral, T. A.

    2010-04-01

    Survival of methanogens following desiccation depends on whether they are maintained under aerobic or anaerobic conditions. Cells maintained in a desiccated state in the presence of oxygen did not survive as well as those maintained anaerobically.

  8. Stabilisation of microalgae: Iodine mobilisation under aerobic and anaerobic conditions.

    PubMed

    Han, Wei; Clarke, William; Pratt, Steven

    2015-10-01

    Mobilisation of iodine during microalgae stabilisation was investigated, with the view of assessing the potential of stabilised microalgae as an iodine-rich fertiliser. An iodine-rich waste microalgae (0.35 ± 0.05 mg I g(-1) VS(added)) was stabilised under aerobic and anaerobic conditions. Iodine mobilisation was linearly correlated with carbon emission, indicating iodine was in the form of organoiodine. Comparison between iodine and nitrogen mobilisation relative to carbon emission indicated that these elements were, at least in part, housed separately within the cells. After stabilisation, there were 0.22 ± 0.05 and 0.19 ± 0.01 mg g(-1) VS(added) iodine remaining in the solid in the aerobic and anaerobic processed material respectively, meaning 38 ± 5.0% (aerobic) and 50 ± 8.6% (anaerobic) of the iodine were mobilised, and consequently lost from the material. The iodine content of the stabilised material is comparable to the iodine content of some seaweed fertilisers, and potentially satisfies an efficient I-fertilisation dose.

  9. Bacterial Drug Tolerance under Clinical Conditions Is Governed by Anaerobic Adaptation but not Anaerobic Respiration

    PubMed Central

    Hemsley, Claudia M.; Luo, Jamie X.; Andreae, Clio A.; Butler, Clive S.; Soyer, Orkun S.

    2014-01-01

    Noninherited antibiotic resistance is a phenomenon whereby a subpopulation of genetically identical bacteria displays phenotypic tolerance to antibiotics. We show here that compared to Escherichia coli, the clinically relevant genus Burkholderia displays much higher levels of cells that tolerate ceftazidime. By measuring the dynamics of the formation of drug-tolerant cells under conditions that mimic in vivo infections, we show that in Burkholderia bacteria, oxygen levels affect the formation of these cells. The drug-tolerant cells are characterized by an anaerobic metabolic signature and can be eliminated by oxygenating the system or adding nitrate. The transcriptome profile suggests that these cells are not dormant persister cells and are likely to be drug tolerant as a consequence of the upregulation of anaerobic nitrate respiration, efflux pumps, β-lactamases, and stress response proteins. These findings have important implications for the treatment of chronic bacterial infections and the methodologies and conditions that are used to study drug-tolerant and persister cells in vitro. PMID:25049258

  10. Bacterial drug tolerance under clinical conditions is governed by anaerobic adaptation but not anaerobic respiration.

    PubMed

    Hemsley, Claudia M; Luo, Jamie X; Andreae, Clio A; Butler, Clive S; Soyer, Orkun S; Titball, Richard W

    2014-10-01

    Noninherited antibiotic resistance is a phenomenon whereby a subpopulation of genetically identical bacteria displays phenotypic tolerance to antibiotics. We show here that compared to Escherichia coli, the clinically relevant genus Burkholderia displays much higher levels of cells that tolerate ceftazidime. By measuring the dynamics of the formation of drug-tolerant cells under conditions that mimic in vivo infections, we show that in Burkholderia bacteria, oxygen levels affect the formation of these cells. The drug-tolerant cells are characterized by an anaerobic metabolic signature and can be eliminated by oxygenating the system or adding nitrate. The transcriptome profile suggests that these cells are not dormant persister cells and are likely to be drug tolerant as a consequence of the upregulation of anaerobic nitrate respiration, efflux pumps, β-lactamases, and stress response proteins. These findings have important implications for the treatment of chronic bacterial infections and the methodologies and conditions that are used to study drug-tolerant and persister cells in vitro. Copyright © 2014 Hemsley et al.

  11. Dietary sodium citrate supplementation does not improve upper-body anaerobic performance in trained wrestlers in simulated competition-day conditions.

    PubMed

    Aedma, Martin; Timpmann, Saima; Ööpik, Vahur

    2015-02-01

    Similarly to a wrestling match, upper-body intermittent sprint performance (UBISP) test elicits severe acidosis. This study aimed to determine whether sodium citrate (CIT) ingestion would help to better maintain peak power (PP) and mean power (MP) output across four consecutive UBISP tests simulating wrestling matches of a competition-day. In a double-blind, counterbalanced, crossover manner, 11 trained wrestlers ingested either placebo (PLC) or CIT (900 mg kg(-1)) within a 17-h supplementation period. Thereafter they completed four (T1-T4) 6-min UBISP tests interspersed with 30-min recovery periods. Compared with PLC, CIT supplementation resulted in a persistent increase (P < 0.05) in blood HCO3 (-) concentration and pH: pre-T1 25.6 % and 0.08 units, post-T4 39.1 % and 0.14 units, respectively. Post-T1 blood lactate concentration in CIT (16.1 ± 3.8 mmol L(-1)) was higher (P = 0.037) than that in PLC (13.7 ± 2.3 mmol L(-1)). Decrease in plasma volume across the supplementation period and UBISP tests was greater (P = 0.03) in PLC (-6.91 ± 4.37 %) than in CIT (-1.51 ± 4.34 %). There was an overall decrease (P = 0.028) in ratings of perceived exertion in CIT compared with PLC, but no between-trial difference (P > 0.05) in PP or MP in any UBISP test occurred. In trained wrestlers, CIT ingestion induces alkalosis, counteracts reduction in plasma volume, increases post-test blood lactate concentration and reduces perceived exertion, but does not improve PP or MP attained in consecutive UBISP tests simulating four wrestling matches of a competition-day.

  12. Improved anaerobic digestion by staged fermentation and advanced reactor design

    SciTech Connect

    Ghosh, S.; Bostian, H.E.; Henry, M.P.; Sajjad, A.; Farrell, J.B.; Salotto, B.V.

    1985-01-01

    The anaerobic digestion process has taken on new importance and emphasis in recent years because of its potential applications for energy and chemicals production from various types of renewable-carbon resources, and because it can be coupled with certain electrochemical, thermochemical, and biochemical processes to generate electric power, hydrocarbons, methanol, and other high-value products. A number of initiatives have been taken to improve the anaerobic digestion process in keeping with the increasing appreciation for its utility and versatility of application in municipal, industrial, and rural settings.

  13. Microbial communities mediating algal detritus turnover under anaerobic conditions

    PubMed Central

    Morrison, Jessica M.; Murphy, Chelsea L.; Baker, Kristina; Zamor, Richard M.; Nikolai, Steve J.; Wilder, Shawn; Elshahed, Mostafa S.

    2017-01-01

    Background Algae encompass a wide array of photosynthetic organisms that are ubiquitously distributed in aquatic and terrestrial habitats. Algal species often bloom in aquatic ecosystems, providing a significant autochthonous carbon input to the deeper anoxic layers in stratified water bodies. In addition, various algal species have been touted as promising candidates for anaerobic biogas production from biomass. Surprisingly, in spite of its ecological and economic relevance, the microbial community involved in algal detritus turnover under anaerobic conditions remains largely unexplored. Results Here, we characterized the microbial communities mediating the degradation of Chlorella vulgaris (Chlorophyta), Chara sp. strain IWP1 (Charophyceae), and kelp Ascophyllum nodosum (phylum Phaeophyceae), using sediments from an anaerobic spring (Zodlteone spring, OK; ZDT), sludge from a secondary digester in a local wastewater treatment plant (Stillwater, OK; WWT), and deeper anoxic layers from a seasonally stratified lake (Grand Lake O’ the Cherokees, OK; GL) as inoculum sources. Within all enrichments, the majority of algal biomass was metabolized within 13–16 weeks, and the process was accompanied by an increase in cell numbers and a decrease in community diversity. Community surveys based on the V4 region of the 16S rRNA gene identified different lineages belonging to the phyla Bacteroidetes, Proteobacteria (alpha, delta, gamma, and epsilon classes), Spirochaetes, and Firmicutes that were selectively abundant under various substrate and inoculum conditions. Within all kelp enrichments, the microbial communities structures at the conclusion of the experiment were highly similar regardless of the enrichment source, and were dominated by the genus Clostridium, or family Veillonellaceae within the Firmicutes. In all other enrichments the final microbial community was dependent on the inoculum source, rather than the type of algae utilized as substrate. Lineages enriched

  14. Microbial communities mediating algal detritus turnover under anaerobic conditions.

    PubMed

    Morrison, Jessica M; Murphy, Chelsea L; Baker, Kristina; Zamor, Richard M; Nikolai, Steve J; Wilder, Shawn; Elshahed, Mostafa S; Youssef, Noha H

    2017-01-01

    Algae encompass a wide array of photosynthetic organisms that are ubiquitously distributed in aquatic and terrestrial habitats. Algal species often bloom in aquatic ecosystems, providing a significant autochthonous carbon input to the deeper anoxic layers in stratified water bodies. In addition, various algal species have been touted as promising candidates for anaerobic biogas production from biomass. Surprisingly, in spite of its ecological and economic relevance, the microbial community involved in algal detritus turnover under anaerobic conditions remains largely unexplored. Here, we characterized the microbial communities mediating the degradation of Chlorella vulgaris (Chlorophyta), Chara sp. strain IWP1 (Charophyceae), and kelp Ascophyllum nodosum (phylum Phaeophyceae), using sediments from an anaerobic spring (Zodlteone spring, OK; ZDT), sludge from a secondary digester in a local wastewater treatment plant (Stillwater, OK; WWT), and deeper anoxic layers from a seasonally stratified lake (Grand Lake O' the Cherokees, OK; GL) as inoculum sources. Within all enrichments, the majority of algal biomass was metabolized within 13-16 weeks, and the process was accompanied by an increase in cell numbers and a decrease in community diversity. Community surveys based on the V4 region of the 16S rRNA gene identified different lineages belonging to the phyla Bacteroidetes, Proteobacteria (alpha, delta, gamma, and epsilon classes), Spirochaetes, and Firmicutes that were selectively abundant under various substrate and inoculum conditions. Within all kelp enrichments, the microbial communities structures at the conclusion of the experiment were highly similar regardless of the enrichment source, and were dominated by the genus Clostridium, or family Veillonellaceae within the Firmicutes. In all other enrichments the final microbial community was dependent on the inoculum source, rather than the type of algae utilized as substrate. Lineages enriched included the

  15. Hydrogen evolution by strictly aerobic hydrogen bacteria under anaerobic conditions.

    PubMed

    Kuhn, M; Steinbüchel, A; Schlegel, H G

    1984-08-01

    When strains and mutants of the strictly aerobic hydrogen-oxidizing bacterium Alcaligenes eutrophus are grown heterotrophically on gluconate or fructose and are subsequently exposed to anaerobic conditions in the presence of the organic substrates, molecular hydrogen is evolved. Hydrogen evolution started immediately after the suspension was flushed with nitrogen, reached maximum rates of 70 to 100 mumol of H2 per h per g of protein, and continued with slowly decreasing rates for at least 18 h. The addition of oxygen to an H2-evolving culture, as well as the addition of nitrate to cells (which had formed the dissimilatory nitrate reductase system during the preceding growth), caused immediate cessation of hydrogen evolution. Formate is not the source of H2 evolution. The rates of H2 evolution with formate as the substrate were lower than those with gluconate. The formate hydrogenlyase system was not detectable in intact cells or crude cell extracts. Rather the cytoplasmic, NAD-reducing hydrogenase is involved by catalyzing the release of excessive reducing equivalents under anaerobic conditions in the absence of suitable electron acceptors. This conclusion is based on the following experimental results. H2 is formed only by cells which had synthesized the hydrogenases during growth. Mutants lacking the membrane-bound hydrogenase were still able to evolve H2. Mutants lacking the NAD-reducing or both hydrogenases were unable to evolve H2.

  16. Biotransformation potential of phytosterols under anoxic and anaerobic conditions.

    PubMed

    Dykstra, C M; Giles, H D; Banerjee, S; Pavlostathis, S G

    2014-01-01

    The biotransformation potential of three phytosterols (campesterol, stigmasterol and β-sitosterol) under denitrifying, sulfate-reducing and fermentative/methanogenic conditions was assessed. Using a group contribution method, the standard Gibbs free energy of phytosterols was calculated and used to perform theoretical energetic calculations. The oxidation of phytosterols under aerobic, nitrate-reducing, sulfate-reducing and methanogenic conditions was determined to be energetically feasible. However, using semi-continuously fed cultures maintained at 20-22 °C over 16 weekly feeding cycles (112 days; retention time, 21 days), phytosterol removal was observed under nitrate-reducing and sulfate-reducing conditions, but not under fermentative/methanogenic conditions. Under sulfate-reducing conditions, stigmast-4-en-3-one was identified as an intermediate of phytosterol biotransformation, a reaction more likely carried out by dehydrogenases/isomerases, previously reported to act on cholesterol under both oxic and anoxic (denitrifying) conditions. Further study of the biotransformation of phytosterols under anoxic/anaerobic conditions is necessary to delineate the factors and conditions leading to enhanced phytosterol biodegradation and the development of effective biological treatment systems for the removal of phytosterols from pulp and paper wastewaters and other phytosterol-bearing waste streams.

  17. Anaerobic degradation of citrate under sulfate reducing and methanogenic conditions.

    PubMed

    Gámez, Victor M; Sierra-Alvarez, Reyes; Waltz, Rebecca J; Field, James A

    2009-07-01

    Citrate is an important component of metal processing effluents such as chemical mechanical planarization wastewaters of the semiconductor industry. Citrate can serve as an electron donor for sulfate reduction applied to promote the removal of metals, and it can also potentially be used by methanogens that coexist in anaerobic biofilms. The objective of this study was to evaluate the degradation of citrate with sulfate-reducing and methanogenic biofilms. During batch bioassays, the citrate, acetate, methane and sulfide concentrations were monitored. The results indicate that independent of the biofilm or incubation conditions used, citrate was rapidly fermented with specific rates ranging from 566 to 720 mg chemical oxygen demand (COD) consumed per gram volatile suspended solids per day. Acetate was found to be the main fermentation product of citrate degradation, which was later degraded completely under either methanogenic or sulfate reducing conditions. However, if either sulfate reduction or methanogenesis was infeasible due to specific inhibitors (2-bromoethane sulfonate), absence of sulfate or lack of adequate microorganisms in the biofilm, acetate accumulated to levels accounting for 90-100% of the citrate-COD consumed. Based on carbon balances measured in phosphate buffered bioassays, acetate, CO(2) and hydrogen are the main products of citrate fermentation, with a molar ratio of 2:2:1 per mol of citrate, respectively. In bicarbonate buffered bioassays, acetogenesis of H(2) and CO(2) increased the yield of acetate. The results taken as a whole suggest that in anaerobic biofilm systems, citrate is metabolized via the formation of acetate as the main metabolic intermediate prior to methanogenesis or sulfate reduction. Sulfate reducing consortia must be enriched to utilize acetate as an electron donor in order to utilize the majority of the electron-equivalents in citrate.

  18. Carbon Isotope Fractionation In Biotic Vs. Abiotic Anaerobic Conditions

    NASA Astrophysics Data System (ADS)

    Gebrehiwet, T. A.

    2005-12-01

    Dissimilatory metal reducing bacteria (DMRB) are thought to play an important role in the biogeochemical cycling of Fe, and nutrient elements such as C and P, in the anaerobic subsurface. The consumption of organic carbon sources (including contaminants) by these bacteria can significantly fractionate substrate C isotopes, however the effects of solution composition, electron acceptor, or electron donor on C isotopic fractionation by DMRB is at present poorly quantified. We have conducted experiments to compare the effects of bicarbonate (δ13C = -3‰) and phosphate buffers on carbon isotope fractionation by Shewanella putrefaciens strain 200R. The effects of dissolved carbonate and phosphate on δ13C values of dissolved inorganic C evolved during microbial reduction of ferric citrate (δ 13Cinitial = -25‰) were examined using sodium lactate (δ13Cinitial = -25‰) as electron donor under strict anaerobic conditions at neutral pH and 30°C, under dark and (fluorescent) light conditions. Our results suggest that bicarbonate may enhance the rate of Fe(III) reduction by S. putrefaciens, in comparison with media containing phosphate buffer but no added bicarbonate. Compared with phosphate buffered experiments, the presence of dissolved bicarbonate also resulted in a greater degree of C isotopic fractionation (ɛ=2-3‰ and ɛ=5-7‰, respectively). The effect of light on microbial Fe(III) reduction was negligible, however sterile controls showed a minor but significant quantity of carbon dioxide production in liquid media, most likely from photochemical decomposition of citrate. The abiotic experiments also showed measurable carbon isotope fractionation between the carbon dioxide produced and the organic carbon substrate which will be discussed.

  19. Alkaline post-treatment for improved sludge anaerobic digestion.

    PubMed

    Li, Huan; Zou, Shuxin; Li, Chenchen; Jin, Yiying

    2013-07-01

    Alkaline post-treatment was tested in order to improve sludge anaerobic digestion. Between the 8th and the 12th hour of a 24-h digestion cycle, 5% of sludge was extracted from a semi-continuous digester with a sludge retention time of 20 days. The sludge was then disintegrated with 0.1 mol/L NaOH and returned to the digester after neutralization. The results showed that alkaline post-treatment increased the level of soluble organic substances in the extracted sludge, particularly of volatile fatty acids and polysaccharides. This process resulted in a 33% enhancement of biogas production in comparison with the control. When the ratio of the recycled sludge was further increased to 10% or 15%, the increment of biogas yield was reduced, due to excessive inactivation of anaerobic bacteria in the digester. Alkaline post-treatment had a minimal impact on the dewaterability of digested sludge. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. Anaerobic digestion in mesophilic and room temperature conditions: Digestion performance and soil-borne pathogen survival.

    PubMed

    Chen, Le; Jian, Shanshan; Bi, Jinhua; Li, Yunlong; Chang, Zhizhou; He, Jian; Ye, Xiaomei

    2016-05-01

    Tomato plant waste (TPW) was used as the feedstock of a batch anaerobic reactor to evaluate the effect of anaerobic digestion on Ralstonia solanacearum and Phytophthora capsici survival. Batch experiments were carried out for TS (total solid) concentrations of 2%, 4% and 6% respectively, at mesophilic (37±1°C) and room (20-25°C) temperatures. Results showed that higher digestion performance was achieved under mesophilic digestion temperature and lower TS concentration conditions. The biogas production ranged from 71 to 416L/kg VS (volatile solids). The inactivation of anaerobic digestion tended to increase as digestion performance improved. The maximum log copies reduction of R. solanacearum and P. capsici detected by quantitative PCR (polymerase chain reaction) were 3.80 and 4.08 respectively in reactors with 4% TS concentration at mesophilic temperatures. However, both in mesophilic and room temperature conditions, the lowest reduction of R. solanacearum was found in the reactors with 6% TS concentration, which possessed the highest VFA (volatile fatty acid) concentration. These findings indicated that simple accumulation of VFAs failed to restrain R. solanacearum effectively, although the VFAs were considered poisonous. P. capsici was nearly completely dead under all conditions. Based on the digestion performance and the pathogen survival rate, a model was established to evaluate the digestate biosafety.

  1. PGM2 overexpression improves anaerobic galactose fermentation in Saccharomyces cerevisiae

    PubMed Central

    2010-01-01

    Background In Saccharomyces cerevisiae galactose is initially metabolized through the Leloir pathway after which glucose 6-phosphate enters glycolysis. Galactose is controlled both by glucose repression and by galactose induction. The gene PGM2 encodes the last enzyme of the Leloir pathway, phosphoglucomutase 2 (Pgm2p), which catalyses the reversible conversion of glucose 1-phosphate to glucose 6-phosphate. Overexpression of PGM2 has previously been shown to enhance aerobic growth of S. cerevisiae in galactose medium. Results In the present study we show that overexpression of PGM2 under control of the HXT7'promoter from an integrative plasmid increased the PGM activity 5 to 6 times, which significantly reduced the lag phase of glucose-pregrown cells in an anaerobic galactose culture. PGM2 overexpression also increased the anaerobic specific growth rate whereas ethanol production was less influenced. When PGM2 was overexpressed from a multicopy plasmid instead, the PGM activity increased almost 32 times. However, this increase of PGM activity did not further improve aerobic galactose fermentation as compared to the strain carrying PGM2 on the integrative plasmid. Conclusion PGM2 overexpression in S. cerevisiae from an integrative plasmid is sufficient to reduce the lag phase and to enhance the growth rate in anaerobic galactose fermentation, which results in an overall decrease in fermentation duration. This observation is of particular importance for the future development of stable industrial strains with enhanced PGM activity. PMID:20507616

  2. Biodegradability of nitrogenous compounds under anaerobic conditions and its estimation.

    PubMed

    Hongwei, Yang; Zhanpeng, Jiang; Shaoqi, Shi

    2006-02-01

    The anaerobic biodegradability of 23 nitrogenous compounds, including nitrogenous heterocyclic compounds and aliphatic amines, was tested and assessed in integration. These nitrogenous compounds were classified into readily, partially, and poorly biodegradable compounds after calculation of their integrated assessment indices (IAIs), Rules for anaerobic biodegradation of these compounds were also drawn. Stepwise regression and backpropagation artificial neural network (BP-ANN) methods were applied to establish quantitative structure-biodegradability relationships (QSBRs) based on the assessment results. In QSBR models, three molecular structure descriptors-second-order molecular connectivity index (2chi(V3)chi(v)p), and energy of the highest occupied molecular orbital (EHOMO)--were included. After analysis of the sensitivity of variables in QSBR models, it was found that the key molecular structure descriptor affecting anaerobic biodegradability of nitrogenous compounds is EHOMO, which is directly proportional to the anaerobic biodegradability of nitrogenous compounds.

  3. NATURAL BIOLOGICAL ATTENUATION OF AROMATIC HYDROCARBONS UNDER ANAEROBIC CONDITIONS

    EPA Science Inventory

    There is little consistent difference in the calculated half-lives of aromatic hydrocarbons in different anaerobic environments, but methanogenic environments might be generally the least supportive of rapid biotransformation. Toluene was usually the most rapidly biotransformed...

  4. Metabolically engineered glucose-utilizing Shewanella strains under anaerobic conditions.

    PubMed

    Choi, Donggeon; Lee, Sae Bom; Kim, Sohyun; Min, Byoungnam; Choi, In-Geol; Chang, In Seop

    2014-02-01

    Comparative genome analysis of Shewanella strains predicted that the strains metabolize preferably two- and three-carbon carbohydrates as carbon/electron source because many Shewanella genomes are deficient of the key enzymes in glycolysis (e.g., glucokinase). In addition, all Shewanella genomes are known to have only one set of genes associated with the phosphotransferase system required to uptake sugars. To engineer Shewanella strains that can utilize five- and six-carbon carbohydrates, we constructed glucose-utilizing Shewanella oneidensis MR-1 by introducing the glucose facilitator (glf; ZMO0366) and glucokinase (glk; ZMO0369) genes of Zymomonas mobilis. The engineered MR-1 strain was able to grow on glucose as a sole carbon/electron source under anaerobic conditions. The glucose affinity (Ks) and glucokinase activity in the engineered MR-1 strain were 299.46 mM and 0.259 ± 0.034 U/g proteins. The engineered strain was successfully applied to a microbial fuel cell system and exhibited current generation using glucose as the electron source. Copyright © 2013 Elsevier Ltd. All rights reserved.

  5. Pretreatment methods to improve sludge anaerobic degradability: a review.

    PubMed

    Carrère, H; Dumas, C; Battimelli, A; Batstone, D J; Delgenès, J P; Steyer, J P; Ferrer, I

    2010-11-15

    This paper presents a review of the main sludge treatment techniques used as a pretreatment to anaerobic digestion. These processes include biological (largely thermal phased anaerobic), thermal hydrolysis, mechanical (such as ultrasound, high pressure and lysis), chemical with oxidation (mainly ozonation), and alkali treatments. The first three are the most widespread. Emphasis is put on their impact on the resulting sludge properties, on the potential biogas (renewable energy) production and on their application at industrial scale. Thermal biological provides a moderate performance increase over mesophilic digestion, with moderate energetic input. Mechanical treatment methods are comparable, and provide moderate performance improvements with moderate electrical input. Thermal hydrolysis provides substantial performance increases, with a substantial consumption of thermal energy. It is likely that low impact pretreatment methods such as mechanical and thermal phased improve speed of degradation, while high impact methods such as thermal hydrolysis or oxidation improve both speed and extent of degradation. While increased nutrient release can be a substantial cost in enhanced sludge destruction, it also offers opportunities to recover nutrients from a concentrated water stream as mineral fertiliser. Copyright © 2010 Elsevier B.V. All rights reserved.

  6. Enhanced anaerobic degradability of highly polluted pesticides-bearing wastewater under thermophilic conditions.

    PubMed

    García-Mancha, N; Monsalvo, V M; Puyol, D; Rodriguez, J J; Mohedano, A F

    2017-10-05

    This work presents a sustainable and cost-competitive solution for hardly biodegradable pesticides-bearing wastewater treatment in an anaerobic expanded granular sludge bed (EGSB) reactor at mesophilic (35°C) and thermophilic (55°C). The reactor was operated in continuous mode during 160days, achieving an average COD removal of 33 and 44% under mesophilic and thermophilic conditions, respectively. The increase of temperature improved the biomass activity and the production of methane by 35%. Around 96% of pesticides identified in raw wastewater were not detected in both mesophilic and thermophilic effluents. A dramatic selection of the microbial population in anaerobic granules was caused by the presence of pesticides, which also changed significantly when the temperature was increased. Pesticides caused a significant inhibition on methanogenesis, especially over acetoclastic methanogens. Aerobic biodegradability tests of the resulting anaerobic effluents revealed that aerobic post-treatment is also a feasible and effective option, yielding more than 60% COD reduction. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Improving Project Outcomes and Growing the Anaerobic Digestion Industy Report

    EPA Pesticide Factsheets

    Anaerobic digestion ombudsmen assist with project development, ensure the long-term sustainability of projects, and help advance the industry. This report explores the benefits of anaerobic digestion ombudsmen and provides guidance for implementing them.

  8. Performance and diversity of polyvinyl alcohol-degrading bacteria under aerobic and anaerobic conditions.

    PubMed

    Huang, Jianping; Yang, Shisu; Zhang, Siqi

    2016-11-01

    To compare the degradation performance and biodiversity of a polyvinyl alcohol-degrading microbial community under aerobic and anaerobic conditions. An anaerobic-aerobic bioreactor was operated to degrade polyvinyl alcohol (PVA) in simulated wastewater. The degradation performance of the bioreactor during sludge cultivation and the microbial communities in each reactor were compared. Both anaerobic and aerobic bioreactors demonstrated high chemical oxygen demand removal efficiencies of 87.5 and 83.6 %, respectively. Results of 16S rDNA sequencing indicated that Proteobacteria dominated in both reactors and that the microbial community structures varied significantly under different operating conditions. Both reactors obviously differed in bacterial diversity from the phyla Planctomycetes, Chlamydiae, Bacteroidetes, and Chloroflexi. Betaproteobacteria and Alphaproteobacteria dominated, respectively, in the anaerobic and aerobic reactors. The anaerobic-aerobic system is suitable for PVA wastewater treatment, and the microbial genetic analysis may serve as a reference for PVA biodegradation.

  9. Microbial degradation of lignin-derived compounds under anaerobic conditions

    SciTech Connect

    Colberg, P.J.

    1983-01-01

    Lignin is the second most abundant form of organic carbon in the biosphere. Recent laboratory studies indicate that a large fraction of polymeric lignin is incompletely degraded by aerobic lignolytic microorganisms and is subsequently released as lignin fragments of reduced molecular size. If such lignin-derived compounds become available in the anaerobic environment, they may serve as potential sources of organic carbon for organisms which release methane precursors. The methanogenic bacteria, in turn, serve as terminal members of the anaerobic food chain, and thus, limit the accumulation of organic carbon in anaerobic sinks. This thesis presents evidence to suggest that lignin-derived compounds which have molecular sizes greater than those of single-ring aromatic compounds (MW > 200) are anaerobically biodegradable to methane. This research involved development of selective enrichment cultures capable of utilizing oligolignols as sole carbon sources. Radiolabeled water-soluble catabolites, released during aerobic lignin degradation by the white rot fungus Phanerochaete chrysosporium, were subjected to anaerobic degradation. The second phase of work involved capillary gas chromatographic analyses of enrichment cultures fed a /sup 14/C-labeled, lignin-derived substrate of average molecular weight 600. 2-Bromoethanesulfonic acid was used to inhibit methane formation and enhance buildup of metabolic intermediates, resulting in the accumulation of volatile fatty acids, phenylacetate, benzoate, catechol, 3-phenyl-propionate, vanillin, syringic acid, vanillic acid, ferulic acid, and caffeic acid. A conceptual model for the anaerobic degradation of two- and three-ring lignin fragments is proposed which overlaps both the ferulate and benzoate degradation pathways at the level of single-ring aromatic compounds.

  10. Metabolism of aniline under different anaerobic electron-accepting and nutritional conditions

    SciTech Connect

    De, M.A.; O'Connor, O.A.; Kosson, D.S. . Dept. of Chemical and Biochemical Engineering)

    1994-02-01

    The biodegradability of aniline was evaluated under two different anaerobic conditions, denitrifying and methanogenic. In addition, under denitrifying conditions, the influence of bicarbonate was studied. Anaerobic sewage digester sludge and estuarine sediment were used as heterogeneous sources of bacteria. Under anaerobic denitrifying conditions amended with bicarbonate, aniline was completely mineralized to CO[sub 2] and N[sub 2]. After an initial lag period, N[sub 2] recoveries of 74 and 100% were obtained for sludge and sediment cultures, respectively. Under anaerobic denitrifying conditions with no bicarbonate, aniline depletion was observed; however, stoichiometric quantities of N[sub 2] were not produced from mineralization and were in fact inhibited below background controls. Under methanogenic conditions, aniline concentration remained unchanged for > 31 weeks. A metabolite of aniline, 4-hydroxybenzoate, was detected in bicarbonate-amended denitrifying cultures.

  11. ANAEROBIC BIODEGRADATION OF ALKYLBENZENES IN LABORATORY MICROCOSMS REPRESENTING AMBIENT CONDITIONS

    EPA Science Inventory

    A microcosm study was performed to document the anaerobic biodegradation of benzene, toluene, ethylbenzene, m- xylene, and/or o-xylene in petroleum-contaminated aquifer sediment from sites in Michigan (MI) and North Carolina (NC) and relate the results to previous field investiga...

  12. ANAEROBIC BIODEGRADATION OF ALKYLBENZENES IN LABORATORY MICROCOSMS REPRESENTING AMBIENT CONDITIONS

    EPA Science Inventory

    A microcosm study was performed to document the anaerobic biodegradation of benzene, toluene, ethylbenzene, m- xylene, and/or o-xylene in petroleum-contaminated aquifer sediment from sites in Michigan (MI) and North Carolina (NC) and relate the results to previous field investiga...

  13. Candidatus Accumulibacter phosphatis clades enriched under cyclic anaerobic and microaerobic conditions simultaneously use different electron acceptors

    EPA Science Inventory

    Lab- and pilot-scale simultaneous nitrification, denitrification and phosphorus removal-sequencing batch reactors were operated under cyclic anaerobic and micro-aerobic conditions. The use of oxygen, nitrite, and nitrate as electron acceptors by Candidatus Accumulibacter phosphat...

  14. MICROBIAL DEGRADATION OF NITROGEN, OXYGEN AND SULFUR HETEROCYCLIC COMPOUNDS UNDER ANAEROBIC CONDITIONS: STUDIES WITH AQUIFER SAMPLES

    EPA Science Inventory

    The potential for anaerobic biodegradation of 12 heterocyclic model compounds was studied. Nine of the model compounds were biotransformed in aquifer slurries under sulfate-reducing or methanogenic conditions. The nitrogen and oxygen heterocyclic compounds were more susceptible t...

  15. MICROBIAL DEGRADATION OF NITROGEN, OXYGEN AND SULFUR HETEROCYCLIC COMPOUNDS UNDER ANAEROBIC CONDITIONS: STUDIES WITH AQUIFER SAMPLES

    EPA Science Inventory

    The potential for anaerobic biodegradation of 12 heterocyclic model compounds was studied. Nine of the model compounds were biotransformed in aquifer slurries under sulfate-reducing or methanogenic conditions. The nitrogen and oxygen heterocyclic compounds were more susceptible t...

  16. Candidatus Accumulibacter phosphatis clades enriched under cyclic anaerobic and microaerobic conditions simultaneously use different electron acceptors

    EPA Science Inventory

    Lab- and pilot-scale simultaneous nitrification, denitrification and phosphorus removal-sequencing batch reactors were operated under cyclic anaerobic and micro-aerobic conditions. The use of oxygen, nitrite, and nitrate as electron acceptors by Candidatus Accumulibacter phosphat...

  17. Development of microorganisms in the chernozem under aerobic and anaerobic conditions

    NASA Astrophysics Data System (ADS)

    Polyanskaya, L. M.; Gorbacheva, M. A.; Milanovskii, E. Yu.; Zvyagintsev, D. G.

    2010-03-01

    A microbial succession was studied under aerobic and anaerobic conditions by means of experiments with microcosms in different horizons of a chernozem. It was revealed that, under aerobic conditions, all the microorganisms grow irrespective of the soil horizon; fungi and bacteria grow at the first succession stages, and actinomycetes grow at the last stages. It was shown that, in the case of a simulated anaerobiosis commonly used to study anaerobic populations of bacteria, the mycelium of micromycetes grows in the upper part of the chernozem’s A horizon. Under anaerobic conditions, the peak of the mycelium development is shifted from the 3rd to 7th days (typical for aerobic conditions) to the 7th to 15th days of incubation. The level of mycelium length’s stabilization under aerobic and anaerobic conditions also differs: it is higher or lower than the initial one, respectively. Under anaerobic conditions, the growth of fungal mycelium, bacteria, and actinomycetes in the lower part of the A horizon and in the B horizon is extremely weak. There was not any observed growth of actinomycetes in all the chernozem’s horizons under anaerobic conditions.

  18. Characterization of lighted upflow anaerobic sludge blanket (LUASB) method under sulfate-rich conditions.

    PubMed

    Sawayama, S; Tsukahara, K; Yagishita, T; Hanada, S

    2001-01-01

    Growth of phototrophic bacteria was induced from granules in a lighted upflow anaerobic sludge blanket (LUASB) reactor supplied with an organic-acid-based medium containing 141.7 mg S.l(-1) of SO4(2-) under light conditions (100 microE.m(-2).s(-1)). We investigated the population dynamics of phototrophic bacteria in the LUASB reactor and the performance of the LUASB reactor for wastewater treatment and poly-beta-hydroxybutyrate (PHB) production under anaerobic light and sulfate-rich conditions. In vivo absorption spectra and a colony count suggested that populations of Rhodopseudomonas palustris and Blastochloris sulfoviridis in the LUASB reactor supplied with a medium containing 574.4 mg S.l(-1) of SO4(2-) under light conditions were lower than those supplied with a medium containing 1.0 or 141.7 mg S.l(-1) of SO4(2-) under parallel conditions. Removal efficiencies of ammonium and phosphate in the LUASB reactor supplied with the medium containing 141.7 mg S.l(-1) of SO4(2-) under light conditions were higher than those under parallel conditions but without illumination. The difference in the results of runs under light or dark conditions suggested that the ammonium and phosphate ion removal efficiencies were improved by increasing the amount of phototrophic bacterial biomass in the LUASB reactor under sulfate-rich conditions. The average PHB production rates of the bacterial cells recovered from the effluent of the LUASB reactor supplied with a medium containing 141.7, 283.5 or 574.4 mg S.l(-1) of SO4(2-) were 1.0-2.9 mg.l(-1)-reactor.d(-1) and the average PHB content based on the dry bacterial biomass was 1.4-3.6%.

  19. Reduction of Nitrated Diphenylamine Derivatives under Anaerobic Conditions

    PubMed Central

    Drzyzga, O.; Schmidt, A.; Blotevogel, K.

    1995-01-01

    2-Nitrodiphenylamine, 4-nitrodiphenylamine, and 2,4-dinitrodiphenylamine were anaerobically metabolized in sediment-water batch enrichments inoculated with mud from the German North Sea coast. The first intermediate in 2,4-dinitrodiphenylamine degradation was 2-amino-4-nitrodiphenylamine, which appeared in large (nearly stoichiometric) amounts before being completely reduced to 2,4-diaminodiphenylamine. Of the second theoretically expected metabolite, 4-amino-2-nitrodiphenylamine, only traces were detected by gas chromatographic-mass spectrometric analysis in highly concentrated extracts. In addition, low levels of 4-nitrodiphenylamine, which may be the product of ortho deamination of intermediately produced 2-amino-4-nitrodiphenylamine, were observed. 2-Nitrodiphenylamine and 4-nitrodiphenylamine were primarily reduced to 2-aminodiphenylamine and 4-aminodiphenylamine, respectively. Diphenylamine was never detected in any experiment as a theoretically possible intermediate. Results from studies with dense cell suspensions of anaerobic, aromatic-compound-mineralizing bacteria confirmed the transformation reactions, which were carried out by microorganisms indigenous to the anaerobic coastal water sediment. PMID:16535118

  20. The role of anaerobic sludge recycle in improving anaerobic digester performance.

    PubMed

    Young, Michelle N; Krajmalnik-Brown, Rosa; Liu, Wenjun; Doyle, Michael L; Rittmann, Bruce E

    2013-01-01

    Solids retention time (SRT) is a critical parameter for the performance of anaerobic digesters (AD) in wastewater treatment plants. AD SRT should increase when active biomass is input to the AD by recycling anaerobic sludge via the wastewater-treatment tanks, creating a hybrid aerobic/anaerobic system. When 85% of the flow through the AD was recycled in pilot-scale hybrid systems, the AD SRT increased by as much as 9-fold, compared to a parallel system without anaerobic-sludge recycle. Longer AD SRTs resulted in increased hydrolysis and methanogenesis in the AD: net solids yield decreased by 39-96% for overall and 23-94% in the AD alone, and AD methane yield increased 1.5- to 5.5-fold. Microbial community assays demonstrated higher, more consistent Archaea concentrations in all tanks in the wastewater-treatment system with anaerobic-sludge recycle. Thus, multiple lines of evidence support that AD-sludge recycle increased AD SRT, solids hydrolysis, and methane generation.

  1. Effect of micro-aeration on anaerobic digestion of primary sludge under septic tank conditions.

    PubMed

    Diak, James; Örmeci, Banu; Kennedy, Kevin J

    2013-04-01

    Micro-aeration, which refers to the addition of very small amounts of air, is a simple technology that can potentially be incorporated in septic tanks to improve the digestion performance. The purpose of this study was to investigate and compare the effects of micro-aeration on anaerobic digestion of primary sludge under septic tank conditions. 1.6 L batch reactor experiments were carried out in duplicate using raw primary sludge, with 4.1 % total solids, and diluted primary sludge, with 2.1 % total solids. Reactors were operated for 5 weeks at room temperature to simulate septic tank conditions. Micro-aeration rate of 0.00156 vvm effectively solubilised chemical oxygen demand (COD) and improved the subsequent degradation of COD. Micro-aeration also increased the generation of ammonia and soluble proteins, but did not improve the reduction in total and volatile solids, or the reduction in carbohydrates. Experiments using diluted sludge samples showed similar trends as the experiments with raw sludge, which suggest that initial solids concentration did not have a significant effect on the degradation of primary sludge under septic tank conditions.

  2. Nitrous oxide production by Alcaligenes faecalis under transient and dynamic aerobic and anaerobic conditions.

    PubMed Central

    Otte, S; Grobben, N G; Robertson, L A; Jetten, M S; Kuenen, J G

    1996-01-01

    Nitrous oxide can be a harmful by-product in nitrogen removal from wastewater. Since wastewater treatment systems operate under different aeration regimens, the influence of different oxygen concentrations and oxygen fluctuations on denitrification was studied. Continuous cultures of Alcaligenes faecalis TUD produced N2O under anaerobic as well as aerobic conditions. Below a dissolved oxygen concentration of 5% air saturation, the relatively highest N2O production was observed. Under these conditions, significant activities of nitrite reductase could be measured. After transition from aerobic to anaerobic conditions, there was insufficient nitrite reductase present to sustain growth and the culture began to wash out. After 20 h, nitrite reductase became detectable and the culture started to recover. Nitrous oxide reductase became measurable only after 27 h, suggesting sequential induction of the denitrification reductases, causing the transient accumulation of N2O. After transition from anaerobic conditions to aerobic conditions, nitrite reduction continued (at a lower rate) for several hours. N2O reduction appeared to stop immediately after the switch, indicating inhibition of nitrous oxide reductase, resulting in high N2O emissions (maximum, 1.4 mmol liter-1 h-1). The nitrite reductase was not inactivated by oxygen, but its synthesis was repressed. A half-life of 16 to 22 h for nitrite reductase under these conditions was calculated. In a dynamic aerobic-anaerobic culture of A. faecalis, a semisteady state in which most of the N2O production took place after the transition from anaerobic to aerobic conditions was obtained. The nitrite consumption rate in this culture was equal to that in an anaerobic culture (0.95 and 0.92 mmol liter-1 h-1, respectively), but the production of N2O was higher in the dynamic culture (28 and 26% of nitrite consumption, respectively). PMID:8779582

  3. Decomposition Dynamics and Changes in Chemical Composition of Wheat Straw Residue under Anaerobic and Aerobic Conditions

    PubMed Central

    Gao, Hongjian; Chen, Xi; Wei, Junling; Zhang, Yajie; Zhang, Ligan; Chang, Jiang; Thompson, Michael L.

    2016-01-01

    Soil aeration is a crucial factor that regulates crop residue decomposition, and the chemical composition of decomposing crop residues may change the forms and availability of soil nutrients, such as N and P. However, to date, differences in the chemical composition of crop straw residues after incorporation into soil and during its decomposition under anaerobic vs. aerobic conditions have not been well documented. The objective of the present study was to assess changes in the C-containing functional groups of wheat straw residue during its decomposition in anaerobic and aerobic environments. A 12-month incubation experiment was carried out to investigate the temporal variations of mass, carbon, and nitrogen loss, as well as changes in the chemical composition of wheat (Triticum aestivum L) straw residues under anaerobic and aerobic conditions by measuring C-containing functional groups using solid state nuclear magnetic resonance (NMR) spectroscopy. The residual mass, carbon content, and nitrogen content of the straw residue sharply declined during the initial 3 months, and then slowly decreased during the last incubation period from 3 to 12 months. The decomposition rate constant (k) for mass loss under aerobic conditions (0.022 d-1) was higher than that under anaerobic conditions (0.014 d-1). The residual mass percentage of cellulose and hemicellulose in the wheat straw gradually declined, whereas that of lignin gradually increased during the entire 12-month incubation period. The NMR spectra of C-containing functional groups in the decomposing straw under both aerobic and anaerobic conditions were similar at the beginning of the incubation as well as at 1 month, 6 months, and 12 months. The main alterations in C-containing functional groups during the decomposition of wheat straw were a decrease in the relative abundances of O-alkyl C and an increase in the relative abundances of alkyl C, aromatic C and COO/N-C = O functional groups. The NMR signals of alkyl C

  4. Decomposition Dynamics and Changes in Chemical Composition of Wheat Straw Residue under Anaerobic and Aerobic Conditions.

    PubMed

    Gao, Hongjian; Chen, Xi; Wei, Junling; Zhang, Yajie; Zhang, Ligan; Chang, Jiang; Thompson, Michael L

    2016-01-01

    Soil aeration is a crucial factor that regulates crop residue decomposition, and the chemical composition of decomposing crop residues may change the forms and availability of soil nutrients, such as N and P. However, to date, differences in the chemical composition of crop straw residues after incorporation into soil and during its decomposition under anaerobic vs. aerobic conditions have not been well documented. The objective of the present study was to assess changes in the C-containing functional groups of wheat straw residue during its decomposition in anaerobic and aerobic environments. A 12-month incubation experiment was carried out to investigate the temporal variations of mass, carbon, and nitrogen loss, as well as changes in the chemical composition of wheat (Triticum aestivum L) straw residues under anaerobic and aerobic conditions by measuring C-containing functional groups using solid state nuclear magnetic resonance (NMR) spectroscopy. The residual mass, carbon content, and nitrogen content of the straw residue sharply declined during the initial 3 months, and then slowly decreased during the last incubation period from 3 to 12 months. The decomposition rate constant (k) for mass loss under aerobic conditions (0.022 d-1) was higher than that under anaerobic conditions (0.014 d-1). The residual mass percentage of cellulose and hemicellulose in the wheat straw gradually declined, whereas that of lignin gradually increased during the entire 12-month incubation period. The NMR spectra of C-containing functional groups in the decomposing straw under both aerobic and anaerobic conditions were similar at the beginning of the incubation as well as at 1 month, 6 months, and 12 months. The main alterations in C-containing functional groups during the decomposition of wheat straw were a decrease in the relative abundances of O-alkyl C and an increase in the relative abundances of alkyl C, aromatic C and COO/N-C = O functional groups. The NMR signals of alkyl C

  5. Anaerobic Oxidation of [1,2-14C]Dichloroethene under Mn(IV)-Reducing Conditions

    PubMed Central

    Bradley, Paul M.; Landmeyer, James E.; Dinicola, Richard S.

    1998-01-01

    Anaerobic oxidation of [1,2-14C]dichloroethene to 14CO2 under Mn(IV)-reducing conditions was demonstrated. The results indicate that oxidative degradation of partially chlorinated solvents like dichloroethene can be significant even under anoxic conditions and demonstrate the potential importance of Mn(IV) reduction for remediation of chlorinated groundwater contaminants. PMID:16349554

  6. Anaerobic oxidation of [1,2-14C]Dichloroethene under Mn(IV)-reducing conditions

    USGS Publications Warehouse

    Bradley, Paul M.; Landmeyer, James E.; Dinicola, Richard S.

    1998-01-01

    Anaerobic oxidation of [1,2-14C]dichloroethene to14CO2 under Mn(IV)-reducing conditions was demonstrated. The results indicate that oxidative degradation of partially chlorinated solvents like dichloroethene can be significant even under anoxic conditions and demonstrate the potential importance of Mn(IV) reduction for remediation of chlorinated groundwater contaminants.

  7. Succinate and Lactate Production from Euglena gracilis during Dark, Anaerobic Conditions

    PubMed Central

    Tomita, Yuko; Yoshioka, Kazumasa; Iijima, Hiroko; Nakashima, Ayaka; Iwata, Osamu; Suzuki, Kengo; Hasunuma, Tomohisa; Kondo, Akihiko; Hirai, Masami Yokota; Osanai, Takashi

    2016-01-01

    Euglena gracilis is a eukaryotic, unicellular phytoflagellate that has been widely studied in basic science and applied science. Under dark, anaerobic conditions, the cells of E. gracilis produce a wax ester that can be converted into biofuel. Here, we demonstrate that under dark, anaerobic conditions, E. gracilis excretes organic acids, such as succinate and lactate, which are bulk chemicals used in the production of bioplastics. The levels of succinate were altered by changes in the medium and temperature during dark, anaerobic incubation. Succinate production was enhanced when cells were incubated in CM medium in the presence of NaHCO3. Excretion of lactate was minimal in the absence of external carbon sources, but lactate was produced in the presence of glucose during dark, anaerobic incubation. E. gracilis predominantly produced L-lactate; however, the percentage of D-lactate increased to 28.4% in CM medium at 30°C. Finally, we used a commercial strain of E. gracilis for succinate production and found that nitrogen-starved cells, incubated under dark, anaerobic conditions, produced 869.6 mg/L succinate over a 3-day incubation period, which was 70-fold higher than the amount produced by nitrogen-replete cells. This is the first study to demonstrate organic acid excretion by E. gracilis cells and to reveal novel aspects of primary carbon metabolism in this organism. PMID:28066371

  8. Succinate and Lactate Production from Euglena gracilis during Dark, Anaerobic Conditions.

    PubMed

    Tomita, Yuko; Yoshioka, Kazumasa; Iijima, Hiroko; Nakashima, Ayaka; Iwata, Osamu; Suzuki, Kengo; Hasunuma, Tomohisa; Kondo, Akihiko; Hirai, Masami Yokota; Osanai, Takashi

    2016-01-01

    Euglena gracilis is a eukaryotic, unicellular phytoflagellate that has been widely studied in basic science and applied science. Under dark, anaerobic conditions, the cells of E. gracilis produce a wax ester that can be converted into biofuel. Here, we demonstrate that under dark, anaerobic conditions, E. gracilis excretes organic acids, such as succinate and lactate, which are bulk chemicals used in the production of bioplastics. The levels of succinate were altered by changes in the medium and temperature during dark, anaerobic incubation. Succinate production was enhanced when cells were incubated in CM medium in the presence of NaHCO3. Excretion of lactate was minimal in the absence of external carbon sources, but lactate was produced in the presence of glucose during dark, anaerobic incubation. E. gracilis predominantly produced L-lactate; however, the percentage of D-lactate increased to 28.4% in CM medium at 30°C. Finally, we used a commercial strain of E. gracilis for succinate production and found that nitrogen-starved cells, incubated under dark, anaerobic conditions, produced 869.6 mg/L succinate over a 3-day incubation period, which was 70-fold higher than the amount produced by nitrogen-replete cells. This is the first study to demonstrate organic acid excretion by E. gracilis cells and to reveal novel aspects of primary carbon metabolism in this organism.

  9. Nitrous oxide production by Alcaligenes faecalis under transient and dynamic aerobic and anaerobic conditions

    SciTech Connect

    Otte, S.; Grobben, N.G.; Robertson, L.A.; Jetten, M.S.M.; Kuenen, J.G.

    1996-07-01

    Nitrous oxide production contributes to both greenhouse effect and ozone depletion in the stratosphere. A significant part of the global N2O emission can be attributed to microbial processes, especially nitrification and denitrification, used in biological wastewater treatment systems. This study looks at the efficiency of denitrification and the enzymes involved, with the emphasis on N2O production during the transient phase from aerobic to anaerobic conditions and vice versa. The effect of repetitive changing aerobic-anaerobic conditions on N2O was also studied. Alcaligenes faecalis was used as the model denitrofing organism. 35 refs., 3 figs., 1 tab.

  10. Heterologous production of Pseudomonas aeruginosa rhamnolipid under anaerobic conditions for microbial enhanced oil recovery.

    PubMed

    Zhao, F; Shi, R; Zhao, J; Li, G; Bai, X; Han, S; Zhang, Y

    2015-02-01

    The ex situ application of rhamnolipid to enhance oil recovery is costly and complex in terms of rhamnolipid production and transportation, while in situ production of rhamnolipid is restricted by the oxygen-deficient environments of oil reservoirs. To overcome the oxygen-limiting conditions and to circumvent the complex regulation of rhamnolipid biosynthesis in Pseudomonas aeruginosa, an engineered strain Pseudomonas stutzeri Rhl was constructed for heterologous production of rhamnolipid under anaerobic conditions. The rhlABRI genes for rhamnolipid biosynthesis were cloned into a facultative anaerobic strain Ps. stutzeri DQ1 to construct the engineered strain Rhl. Anaerobic production of rhamnolipid was confirmed by thin layer chromatography and Fourier transform infrared analysis. Rhamnolipid product reduced the air-water surface tension to 30.3 mN m(-1) and the oil-water interfacial tension to 0.169 mN m(-1). Rhl produced rhamnolipid of 1.61 g l(-1) using glycerol as the carbon source. Rhl anaerobic culture emulsified crude oil up to EI24 ≈ 74. An extra 9.8% of original crude oil was displaced by Rhl in the core flooding test. Strain Rhl achieved anaerobic production of rhamnolipid and worked well for enhanced oil recovery in the core flooding model. The rhamnolipid produced by Rhl was similar to that of the donor strain SQ6. This is the first study to achieve anaerobic and heterologous production of rhamnolipid. Results demonstrated the potential feasibility of Rhl as a promising strain to enhance oil recovery through anaerobic production of rhamnolipid. © 2014 The Society for Applied Microbiology.

  11. Improved anaerobic use of arginine by Saccharomyces cerevisiae.

    PubMed

    Martin, Olga; Brandriss, Marjorie C; Schneider, Gisbert; Bakalinsky, Alan T

    2003-03-01

    Anaerobic arginine catabolism in Saccharomyces cerevisiae was genetically modified to allow assimilation of all four rather than just three of the nitrogen atoms in arginine. This was accomplished by bypassing normal formation of proline, an unusable nitrogen source in the absence of oxygen, and causing formation of glutamate instead. A pro3 ure2 strain expressing a PGK1 promoter-driven PUT2 allele encoding Delta(1)-pyrroline-5-carboxylate dehydrogenase lacking a mitochondrial targeting sequence produced significant cytoplasmic activity, accumulated twice as much intracellular glutamate, and produced twice as much cell mass as the parent when grown anaerobically on limiting arginine as sole nitrogen source.

  12. Anaerobic degradation and dehalogenation of chlorosalicylates and salicylate under four reducing conditions.

    PubMed

    Milligan, P W; Häggblom, M M

    2001-01-01

    The anaerobic biodegradability and transformation of the mono-and dichlorinated salicylates (2-hydroxybenzoates) was examined under denitrifying, Fe (III) reducing, sulfate reducing and methanogenic conditions. 3,6-Dichlorosalicylate and 6-chlorosalicylate are anaerobic microbial metabolites of dicamba, a widely used herbicide. Anaerobic microcosms were established with dicamba treated soil from Wyoming, and golf course drainage stream sediments from New Jersey, which were each spiked with salicylate, 3,6-dichlorosalicylate or one of the four monochlorosalicylate isomers. Salicylate was degraded under denitrifying, sulfidogenic and methanogenic conditions. In methanogenic enrichments 5-chlorosalicylate and 3-chlorosalicylate were reductively dehalogenated to salicylate which was then utilized. Dehalogenation of monochlorinated salicylates to salicylate was also observed in denitrifying chlorosalicylate degrading cultures. The study revealed that the position of the chlorine substituent as well as the predominant electron accepting process affect the rate and extent of chlorosalicylate degradation in anoxic environments.

  13. Enhanced anaerobic digestion of organic contaminants containing diverse microbial population by combined microbial electrolysis cell (MEC) and anaerobic reactor under Fe(III) reducing conditions.

    PubMed

    Zhang, Jingxin; Zhang, Yaobin; Quan, Xie; Chen, Shuo; Afzal, Shahzad

    2013-05-01

    Microbial electrolysis cell (MEC) devices are efficient for wastewater treatment, but its application was limited due to low anode oxidation rate. The objective of this study was to improve anode performance of a MEC combined anaerobic reactor (R1) for high concentration industrial wastewater treatment via dosing Fe(OH)3. For the first 53 days without power, the addition of Fe(OH)3 in R1 enhanced the degradation of reactive brilliant red X-3B dye and sucrose. Applying a voltage of 0.8 V in R1 resulted in a higher decolorization and COD removal through driving the redox reactions at electrodes under Fe(III)-reducing conditions. Real-time PCR and enzyme activity analysis showed that the abundance and azoreductase activity of bacteria were improved in R1. Pyrosequencing revealed that dominant populations in anode biofilm and R1 were more diverse and abundant than the common anaerobic reactor (R2), and there was a significant distinction among anode film, R1 and R2 in microbial community structure. Copyright © 2013 Elsevier Ltd. All rights reserved.

  14. Monoaromatic hydrocarbon transformation under anaerobic conditions at Seal Beach, California: Laboratory studies

    SciTech Connect

    Ball, H.A.; Reinhard, M.

    1996-02-01

    Anaerobic biotransformation of several aromatic hydrocarbons found in gasoline including benzene, toluene, ethylbenzene, m-xylene, p-xylene, and o-xylene (BTEX) was studied in batch anaerobic laboratory microcosms. Aquifer sediment and ground water were obtained from the site of a historic gasoline spill at Seal Beach, California. Sulfate is present in the site ground water at 80 mg/L, and sulfate-reducing activity appears to be the dominant intrinsic BTEX bioremediation process where nitrate is absent. In the laboratory, the microcosms were set up with different electron acceptors (sulfate and nitrate) in site ground water and various defined anaerobic media to estimate intrinsic biodegradation rates and to suggest conditions under which anaerobic bioremediation could be enhanced. In unamended microcosms, anaerobic biotransformation of toluene and m + p-xylene occurred at a rate of 7.2 and 4.1 {micro}g/liter hr, respectively, with sulfate as the apparent electron acceptor. Addition of nitrate stimulated nitrate-reducing conditions and increased rates of toluene and m + p-xylene biotransformation to 30.1 and 5.4 {micro}g/liter hr, respectively. The catabolic substrate range was altered to include ethylbenzene in the nitrate-amended microcosms, suggesting an apparent preferential use of different BTEX compounds depending on the electron acceptor available. Under all the conditions studied, more than twice the amount of nitrate or sulfate was used than could be accounted for by the observed BTEX degradation. The results of these experiments indicate that indigenous microorganisms from the Seal Beach aquifer have significant capability to degrade BTEX hydrocarbons and that intrinsic processes in the Seal Beach aquifer may remediate a portion of the hydrocarbon contamination in situ without intervention. However, the data also suggest that intervention by nitrate addition would enhance the rate and extent of anaerobic BTEX biotransformation.

  15. Binary Interactions of Antagonistic Bacteria with Candida albicans Under Aerobic and Anaerobic Conditions.

    PubMed

    Benadé, Eliska; Stone, Wendy; Mouton, Marnel; Postma, Ferdinand; Wilsenach, Jac; Botha, Alfred

    2016-04-01

    We used both aerobic and anaerobic liquid co-cultures, prepared with Luria Bertani broth, to study the effect of bacteria on the survival of Candida albicans in the external environment, away from an animal host. The bacteria were represented by Aeromonas hydrophila, Bacillus cereus, Bacillus subtilis, Clostridium, Enterobacter, Klebsiella pneumoniae, Kluyvera ascorbata and Serratia marcescens. Under aerobic conditions, the yeast's growth was inhibited in the presence of bacterial growth; however, under anaerobic conditions, yeast and bacterial growth in co-cultures was similar to that observed for pure cultures. Subsequent assays revealed that the majority of bacterial strains aerobically produced extracellular hydrolytic enzymes capable of yeast cell wall hydrolysis, including chitinases and mannan-degrading enzymes. In contrast, except for the A. hydrophila strain, these enzymes were not detected in anaerobic bacterial cultures, nor was the antimicrobial compound prodigiosin found in anaerobic cultures of S. marcescens. When we suspended C. albicans cells in crude extracellular enzyme preparations from K. pneumoniae and S. marcescens, we detected no negative effect on yeast viability. However, we found that these preparations enhance the toxicity of prodigiosin towards the yeast, especially in combination with mannan-degrading enzymes. Analyses of the chitin and mannan content of yeast cell walls revealed that less chitin was produced under anaerobic than aerobic conditions; however, the levels of mannan, known for its low permeability, remained the same. The latter phenomenon, as well as reduced production of the bacterial enzymes and prodigiosin, may contribute to anaerobic growth and survival of C. albicans in the presence of bacteria.

  16. Use of Response Surface Methodology to Optimize Culture Conditions for Hydrogen Production by an Anaerobic Bacterial Strain from Soluble Starch

    NASA Astrophysics Data System (ADS)

    Kieu, Hoa Thi Quynh; Nguyen, Yen Thi; Dang, Yen Thi; Nguyen, Binh Thanh

    2016-05-01

    Biohydrogen is a clean source of energy that produces no harmful byproducts during combustion, being a potential sustainable energy carrier for the future. Therefore, biohydrogen produced by anaerobic bacteria via dark fermentation has attracted attention worldwide as a renewable energy source. However, the hydrogen production capability of these bacteria depends on major factors such as substrate, iron-containing hydrogenase, reduction agent, pH, and temperature. In this study, the response surface methodology (RSM) with central composite design (CCD) was employed to improve the hydrogen production by an anaerobic bacterial strain isolated from animal waste in Phu Linh, Soc Son, Vietnam (PL strain). The hydrogen production process was investigated as a function of three critical factors: soluble starch concentration (8 g L-1 to 12 g L-1), ferrous iron concentration (100 mg L-1 to 200 mg L-1), and l-cysteine concentration (300 mg L-1 to 500 mg L-1). RSM analysis showed that all three factors significantly influenced hydrogen production. Among them, the ferrous iron concentration presented the greatest influence. The optimum hydrogen concentration of 1030 mL L-1 medium was obtained with 10 g L-1 soluble starch, 150 mg L-1 ferrous iron, and 400 mg L-1 l-cysteine after 48 h of anaerobic fermentation. The hydrogen concentration produced by the PL strain was doubled after using RSM. The obtained results indicate that RSM with CCD can be used as a technique to optimize culture conditions for enhancement of hydrogen production by the selected anaerobic bacterial strain. Hydrogen production from low-cost organic substrates such as soluble starch using anaerobic fermentation methods may be one of the most promising approaches.

  17. Anaerobic Biodegradation of Soybean Biodiesel and Diesel Blends under Methanogenic Conditions

    EPA Science Inventory

    Biotransformation of soybean biodiesel and the inhibitory effect of petrodiesel were studied under methanogenic conditions. Biodiesel removal efficiency of more than 95% was achieved in a chemostat with influent biodiesel concentrations up to 2.45 g/L. The kinetics of anaerobic...

  18. Proton motive force generation from stored polymers for the uptake of acetate under anaerobic conditions.

    PubMed

    Saunders, Aaron M; Mabbett, Amanda N; McEwan, Alastair G; Blackall, Linda L

    2007-09-01

    The bacteria facilitating enhanced biological phosphorus removal gain a selective advantage from intracellularly stored polymer-driven substrate uptake under anaerobic conditions during sequential anaerobic : aerobic cycling. Mechanisms for these unusual membrane transport processes were proposed and experimentally validated using selective inhibitors and highly-enriched cultures of a polyphosphate-accumulating organism, Accumulibacter, and a glycogen-accumulating organism, Competibacter. Acetate uptake by both Accumulibacter and Competibacter was driven by a proton motive force (PMF). Stored polymers were used to generate the PMF -Accumulibacter used phosphate efflux through the Pit transporter, while Competibacter generated a PMF by proton efflux through the ATPase and fumarate reductase in the reductive TCA cycle.

  19. Isolation and Characterization of an Enterobacter cloacae Strain That Reduces Hexavalent Chromium under Anaerobic Conditions

    PubMed Central

    Wang, Pi-Chao; Mori, Tsukasa; Komori, Kohya; Sasatsu, Masanori; Toda, Kiyoshi; Ohtake, Hisao

    1989-01-01

    An Enterobacter cloacae strain (HO1) capable of reducing hexavalent chromium (chromate) was isolated from activated sludge. This bacterium was resistant to chromate under both aerobic and anaerobic conditions. Only the anaerobic culture of the E. cloacae isolate showed chromate reduction. In the anaerobic culture, yellow turned white with chromate and the turbidity increased as the reduction proceeded, suggesting that insoluble chromium hydroxide was formed. E. cloacae is likely to utilize toxic chromate as an electron acceptor anaerobically because (i) the anaerobic growth of E. cloacae HO1 accompanied the decrease of toxic chromate in culture medium, (ii) the chromate-reducing activity was rapidly inhibited by oxygen, and (iii) the reduction occurred more rapidly in glycerol- or acetate-grown cells than in glucose-grown cells. The chromate reduction in E. cloacae HO1 was observed at pH 6.0 to 8.5 (optimum pH, 7.0) and at 10 to 40°C (optimum, 30°C). PMID:16347962

  20. Rapid detection of a gfp-marked Enterobacter aerogenes under anaerobic conditions by aerobic fluorescence recovery.

    PubMed

    Zhang, Chong; Xing, Xin-Hui; Lou, Kai

    2005-08-15

    A gfp- and kanamycin-resistance gene-containing plasmid pUCGK was successfully constructed and transformed into Enterobacter aerogenes to develop a rapid GFP-based method for quantifying the bacterial concentration under anaerobic conditions for production of biohydrogen. Since the use of GFP as a molecular reporter is restricted by its requirement for oxygen in the development of the fluorophore, fluorescence detection for the fluorescent E. aerogenes grown anaerobically for hydrogen production was performed by developing a method of aerobic fluorescence recovery (AFR) of the anaerobically expressed GFP. By using this AFR method, rapid and non-disruptive cell quantification of E. aerogenes by fluorescence density was achieved for analyzing the hydrogen production process.

  1. Biodegradability of biodegradable/degradable plastic materials under aerobic and anaerobic conditions.

    PubMed

    Mohee, R; Unmar, G D; Mudhoo, A; Khadoo, P

    2008-01-01

    A study was conducted on two types of plastic materials, Mater-Bi Novamont (MB) and Environmental Product Inc. (EPI), to assess their biodegradability under aerobic and anaerobic conditions. For aerobic conditions, organic fractions of municipal solid wastes were composted. For the anaerobic process, anaerobic inoculum from a wastewater treatment plant was used. Cellulose filter papers (CFP) were used as a positive control for both mediums. The composting process was monitored in terms of temperature, moisture and volatile solids and the biodegradation of the samples were monitored in terms of mass loss. Monitoring results showed a biodegradation of 27.1% on a dry basis for MB plastic within a period of 72 days of composting. Biodegradability under an anaerobic environment was monitored in terms of biogas production. A cumulative methane gas production of 245 ml was obtained for MB, which showed good degradation as compared to CFP (246.8 ml). However, EPI plastic showed a cumulative methane value of 7.6 ml for a period of 32 days, which was close to the blank (4.0 ml). The EPI plastic did not biodegrade under either condition. The cumulative carbon dioxide evolution after 32 days was as follows: CFP 4.406 cm3, MB 2.198 cm3 and EPI 1.328 cm3. The cumulative level of CO2 varying with time fitted sigmoid type curves with R2 values of 0.996, 0.996 and 0.995 for CFP, MB and EPI, respectively.

  2. Comparison of the transport and deposition of Pseudomonas aeruginosa under aerobic and anaerobic conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Huixin; Zeng, Hongbo; Ulrich, Ania C.; Liu, Yang

    2016-02-01

    Laboratory-scale columns were employed to study the effect of oxygen and ionic strength on the transport of Pseudomonas aeruginosa PAO1 in porous media. In anaerobic experiments, cells were grown and transport experiments were conducted in a well-controlled anaerobic chamber. Cell surface electrokinetic potentials were measured and surface elemental composition was analyzed using X-ray photoelectron spectroscopy (XPS). Transport experimental results showed reduced travel distance of PAO1 with increased ionic strength under aerobic and anaerobic conditions, consistent with calculated Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The deposition rates of PAO1 were significantly higher in aerobic than in anaerobic condition at higher ionic strength (10 and 100 mM), although the electrokinetic potentials were similar throughout the tested ionic strength (1, 10, and 100 mM). No difference in PAO1 deposition rate was observed at 1 mM. XPS analysis showed that variation in cell surface composition due to different growth conditions played a primary role in determining the different deposition behaviors.

  3. Effects of reservoir anaerobic, reducing conditions on surfactant retention in chemical flooding

    SciTech Connect

    Wang, F.H.L. )

    1993-05-01

    Surfactant retentions observed in four microemulsion-flooding pilot tests at the Loudon field were substantially lower than predicted from conventional laboratory coreflood experiments. This paper presents research results that explain this discrepancy. The oil reservoir was in an anaerobic, reducing conditions, whereas laboratory corefloods were normally conducted under aerobic, oxidizing conditions. The difference in redox condition was shown to have a serious effect on surfactant retention. Laboratory corefloods conducted under reservoir-like, anaerobic, reducing conditions gave surfactant retention results significantly closer to those observed in field tests. The effect of redox conditions on surfactant adsorption was substantiated further by results from static adsorption experiments with various clay types. Exposure of preserved cores from a reduced reservoir to aerobic conditions can cause high surfactant retention in corefloods. Methods were developed to restore such oxygen-contaminated core material to its original, anaerobic, reduced state. These coreflood procedures simulate actual reservoir conditions better and give meaningful surfactant-retention results for process design optimization.

  4. Products of Leishmania braziliensis glucose catabolism: release of D-lactate and, under anaerobic conditions, glycerol

    SciTech Connect

    Darling, T.N.; Davis, D.G.; London, R.E.; Blum, J.J.

    1987-10-01

    Leishmania braziliensis panamensis promastigotes were incubated with glucose as the sole carbon source. About one-fifth of the glucose consumed under aerobic conditions was oxidized to CO/sub 2/. Nuclear magnetic resonance studies with (1-/sup 13/C)glucose showed that the other products released were succinate, acetate, alanine, pyruvate, and lactate. Under anaerobic conditions, lactate output increased, glycerol became a major product, and, surprisingly, glucose consumption decreased. Enzymatic assays showed that the lactate formed was D(-)-lactate. The release of alanine during incubation with glucose as the sole carbon source suggested that appreciable proteolysis occurred, consistent with our observation that a large amount of ammonia was released under these conditions. The discoveries that D-lactate is a product of L. braziliensis glucose catabolism, that glycerol is produced under anaerobic conditions, and that the cells exhibit a reverse Pasteur effect open the way for detailed studies of the pathways of glucose metabolism and their regulation in this organism.

  5. A statistical method for enhancing the production of succinic acid from Escherichia coli under anaerobic conditions.

    PubMed

    Isar, Jasmine; Agarwal, Lata; Saran, Saurabh; Saxena, Rajendra Kumar

    2006-09-01

    The most influential parameters for succinic acid production obtained through one at a time method were sucrose, tryptone, magnesium carbonate, inoculum size and incubation period. These resulted in the production of 7.0 g L(-1) of succinic acid in 60 h from Escherichia coli W3110 under anaerobic conditions. Based on these results, a statistical method, face centered central composite design (FCCCD) falling under response surface method (RSM) was employed for further enhancing the succinic acid production and to monitor the interactive effect of these parameters, which resulted in a twofold increase in yield (14.3 g L(-1) in 48 h). The analysis of variance (ANOVA) showed the adequacy of the model and the verification experiments confirmed its validity. On subsequent scale-up in a 10-L bioreactor using conditions optimized through RSM, 24.2 g L(-1) of succinic acid was obtained in 30 h. This clearly indicated that the model stood valid even on large-scale. Thus, the statistical optimization strategy led to a 3.5-fold increase in the yield of succinic acid. This is the first report on the use of FCCCD to improve succinic acid production from E. coli.

  6. Comparison of sludge digestion under aerobic and anaerobic conditions with a focus on the degradation of proteins at mesophilic temperature.

    PubMed

    Shao, Liming; Wang, Tianfeng; Li, Tianshui; Lü, Fan; He, Pinjing

    2013-07-01

    Aerobic and anaerobic digestion are popular methods for the treatment of waste activated sludge. However, the differences in degradation of sludge during aerobic and anaerobic digestion remain unclear. In this study, the sludge degradation during aerobic and anaerobic digestion was investigated at mesophilic temperature, focused on protein based on the degradation efficiency and degree of humification. The duration of aerobic and anaerobic digestion was about 90 days. The final degradation efficiency of volatile solid was 66.1 ± 1.6% and 66.4 ± 2.4% under aerobic and anaerobic conditions, respectively. The final degradation efficiency of protein was 67.5 ± 1.4% and 65.1 ± 2.6% under aerobic and anaerobic conditions, respectively. The degradation models of volatile solids were consistent with those of protein under both aerobic and anaerobic conditions. The solubility of protein under aerobic digestion was greater than that under anaerobic digestion. Moreover, the humification index of dissolved organic matter of aerobic digestion was greater than that during anaerobic digestion.

  7. Cyanide toxicity in hepatocytes under aerobic and anaerobic conditions.

    PubMed

    Aw, T Y; Jones, D P

    1989-09-01

    The effect of cyanide on cell viability and mitochondrial function was studied in hepatocytes exposed to air or argon. Cells were more susceptible to cyanide toxicity under air than under argon. Analysis of the disposition of cyanide showed that the difference in susceptibility to KCN was not due to O2-dependent differences in cyanide metabolism or elimination. Studies of mitochondrial function revealed that cyanide under aerobic conditions resulted in substantial swelling of the mitochondria, which corresponded to a matrix loading of phosphate. In addition, cyanide caused a loss of the mitochondrial protonmotive force. This was in contrast to the results for cells exposed to 30 min of anoxia alone in which there was no loss of mitochondrial delta pH, no detectable change in mitochondrial volume, and little matrix loading of phosphate. These results show that at least some of the protective mechanisms elicited by anoxia (B. S. Andersson, T. Y. Aw, and D. P. Jones. Am. J. Physiol. 252 (Cell Physiol. 21): C349-C355, 1987) are not elicited by cyanide alone. Thus cyanide under aerobic conditions does not provide a completely valid model for simple anoxia. Moreover, the results suggest that the molecular sensor necessary to signal suppression of metabolic and transport functions during neahypoxia is dependent on O2 and is neither stimulated nor antagonized by KCN.

  8. Insights into the global regulation of anaerobic metabolism for improved biohydrogen production.

    PubMed

    Lu, Yuan; Zhao, Hongxin; Zhang, Chong; Xing, Xin-Hui

    2016-01-01

    To improve the biohydrogen yield in bacterial dark fermentation, a new approach of global anaerobic regulation was introduced. Two cellular global regulators FNR and NarP were overexpressed in two model organisms: facultatively anaerobic Enterobacter aerogenes (Ea) and strictly anaerobic Clostridium paraputrificum (Cp). The overexpression of FNR and NarP greatly altered anaerobic metabolism and increased the hydrogen yield by 40%. Metabolic analysis showed that the global regulation caused more reducing environment inside the cell. To get a thorough understanding of the global metabolic regulation, more genes (fdhF, fhlA, ppk, Cb-fdh1, and Sc-fdh1) were overexpressed in different Ea and Cp mutants. For the first time, it demonstrated that there were approximately linear relationships between the relative change of hydrogen yield and the relative change of NADH yield or ATP yield. It implied that cellular reducing power and energy level played vital roles in the biohydrogen production.

  9. Can anaerobic performance be improved by remote ischemic preconditioning?

    PubMed

    Lalonde, François; Curnier, Daniel Y

    2015-01-01

    Remote ischemic preconditioning (RIPC) provides a substantial benefit for heart protection during surgery. Recent literature on RIPC reveals the potential to benefit the enhancement of sports performance as well. The aim of this study was to investigate the effect of RIPC on anaerobic performance. Seventeen healthy participants who practice regular physical activity participated in the project (9 women and 8 men, mean age 28 ± 8 years). The participants were randomly assigned to an RIPC intervention (four 5-minute cycles of ischemia reperfusion, followed by 5 minutes using a pressure cuff) or a SHAM intervention in a crossover design. After the intervention, the participants were tested for alactic anaerobic performance (6 seconds of effort) followed by a Wingate test (lactic system) on an electromagnetic cycle ergometer. The following parameters were evaluated: average power, peak power, the scale of perceived exertion, fatigue index (in watt per second), peak power (in Watt), time to reach peak power (in seconds), minimum power (in Watt), the average power-to-weight ratio (in watt per kilogram), and the maximum power-to-weight ratio (in watt per kilogram). The peak power for the Wingate test is 794 W for RIPC and 777 W for the control group (p = 0.208). The average power is 529 W (RIPC) vs. 520 W for controls (p = 0.079). Perceived effort for RIPC is 9/10 on the Borg scale vs. 10/10 for the control group (p = 0.123). Remote ischemic preconditioning does not offer any significant benefits for anaerobic performance.

  10. Dissipation of [(14)C]acetochlor herbicide under anaerobic aquatic conditions in flooded soil microcosms.

    PubMed

    Loor-Vela, Sandra X; Crawford Simmons, Jennifer J; Simmons, F William; Raskin, Lutgarde

    2003-11-05

    Acetochlor degradation was studied under anaerobic conditions representative of conditions in flooded soils. Soil-water microcosms were prepared with a saturated Drummer clay loam and made anaerobic by either glucose pretreatment or N(2) sparging. Sparged microcosms consisted of sulfate-amended, unamended, and gamma-irradiated microcosms. The microcosms were sampled in triplicate at predetermined time intervals during a 371 day incubation period. Volatile, aqueous, extractable, and bound (unextractable) (14)C residues were quantified with liquid scintillation counting and characterized using high-performance liquid radiochromatography (HPLRC) and soil combustion. SO(4)(2)(-), Fe(II), CH(4), and pH were monitored. Complete anaerobic degradation of [(14)C]acetochlor was observed in all viable treatments. The time observed for 50% acetochlor disappearance (DT(50)) was 10 days for iron-reducing and sulfate-reducing conditions (sulfate-amended), 15 days for iron-reducing conditions (unamended), and 16 days for methanogenic conditions (glucose-pretreated). Acetochlor remained after 371 days in the gamma-irradiated microcosms, and metabolites were observed. [(14)C]Metabolites were detected throughout the study. Formation of one of the metabolites correlated with Fe(II) formation (r(2)(), 0.83). A significant portion of the (14)C activity was eventually incorporated into soil-bound residue (30-50% of applied acetochlor) in all treatments.

  11. Detoxification of furfural in Corynebacterium glutamicum under aerobic and anaerobic conditions.

    PubMed

    Tsuge, Yota; Hori, Yoshimi; Kudou, Motonori; Ishii, Jun; Hasunuma, Tomohisa; Kondo, Akihiko

    2014-10-01

    The toxic fermentation inhibitors in lignocellulosic hydrolysates raise serious problems for the microbial production of fuels and chemicals. Furfural is considered to be one of the most toxic compounds among these inhibitors. Here, we describe the detoxification of furfural in Corynebacterium glutamicum ATCC13032 under both aerobic and anaerobic conditions. Under aerobic culture conditions, furfuryl alcohol and 2-furoic acid were produced as detoxification products of furfural. The ratio of the products varied depending on the initial furfural concentration. Neither furfuryl alcohol nor 2-furoic acid showed any toxic effect on cell growth, and both compounds were determined to be the end products of furfural degradation. Interestingly, unlike under aerobic conditions, most of the furfural was converted to furfuryl alcohol under anaerobic conditions, without affecting the glucose consumption rate. Both the NADH/NAD(+) and NADPH/NADP(+) ratio decreased in the accordance with furfural concentration under both aerobic and anaerobic conditions. These results indicate the presence of a single or multiple endogenous enzymes with broad and high affinity for furfural and co-factors in C. glutamicum ATCC13032.

  12. Improvement of anaerobic digestion of sewage sludge through microwave pre-treatment.

    PubMed

    Serrano, A; Siles, J A; Martín, M A; Chica, A F; Estévez-Pastor, F S; Toro-Baptista, E

    2016-07-15

    Sewage sludge generated in the activated sludge process is a polluting waste that must be treated adequately to avoid important environmental impacts. Traditional management methods, such as landfill disposal or incineration, are being ruled out due to the high content in heavy metal, pathogens, micropolluting compounds of the sewage sludge and the lack of use of resources. Anaerobic digestion could be an interesting treatment, but must be improved since the biomethanisation of sewage sludge entails low biodegradability and low methane production. A microwave pre-treatment at pilot scale is proposed to increase the organic matter solubilisation of sewage sludge and enhance the biomethanisation yield. The operational variables of microwave pre-treatment (power and specific energy applied) were optimised by analysing the physicochemical characteristics of sewage sludge (both total and soluble fraction) under different pre-treatment conditions. According to the variation in the sCOD and TN concentration, the optimal operation variables of the pre-treatment were fixed at 20,000 J/g TS and 700 W. A subsequent anaerobic digestion test was carried out with raw and pre-treated sewage sludge under different conditions (20,000 J/g TS and 700 W; 20,000 J/g TS and 400 W; and 30,000 J/g TS and 400 W). Although stability was maintained throughout the process, the enhancement in the total methane yield was not high (up to 17%). Nevertheless, very promising improvements were determined for the kinetics of the process, where the rG and the OLR increased by 43% and 39%, respectively, after carrying out a pre-treatment at 20,000 J/g TS and 700 W.

  13. Stability of antibiotics under growth conditions for thermophilic anaerobes

    SciTech Connect

    Peteranderl, R.; Shotts, E.B. Jr.; Wiegel, J. )

    1990-06-01

    It was shown that the inhibitory effect of kanamycin and streptomycin in a growing culture of Clostridium thermohydrosulfuricum JW 102 is of limited duration. To screen a large number of antibiotics, their stability during incubation under the growth conditions of thermophilic clostridia was determined at 72 and 50C by using a 0.2% yeast extract-amended prereduced mineral medium with a pH of 7.3 or 5.0. Half-lives were determined in a modified MIC test with Escherichia coli, Staphylococcus aureus, and Bacillus megaterium as indicator strains. All compounds tested were similar at the two temperatures or more stable at 50 than at 72C. The half-life (t{sub 1/2}) at pH 7.3 and 72C ranged from 3.3 h (k = 7.26 day{sup {minus}1}, where k (degradation constant) = 1/t{sub 1/2}) for ampicillin to no detectable loss of activity for kanamycin, neomycin, and other antibiotics. Apparently some compounds became more potent during incubation. A change to pH 5.0 caused some compounds to become more labile to become more stable than at pH 7.3.

  14. CO2 -dependent metabolic modulation in red blood cells stored under anaerobic conditions.

    PubMed

    Dumont, Larry J; D'Alessandro, Angelo; Szczepiorkowski, Zbigniew M; Yoshida, Tatsuro

    2016-02-01

    Anaerobic red blood cell (RBC) storage reduces oxidative damage, maintains adenosine triphosphate (ATP) and 2,3-diphosphoglycerate (DPG) levels, and has superior 24-hour recovery at 6 weeks compared to standard storage. This study will determine if removal of CO2 during O2 depletion by gas exchange may affect RBCs during anaerobic storage. This is a matched three-arm study (n = 14): control, O2 and CO2 depleted with Ar (AN), and O2 depleted with 95%Ar/5%CO2 (AN[CO2 ]). RBCs in additives AS-3 or OFAS-3 were evenly divided into three bags, and anaerobic conditions were established by gas exchange. Bags were stored at 1 to 6°C in closed chambers under anaerobic conditions or ambient air, sampled weekly for up to 9 weeks for a panel of in vitro tests. A full metabolomics screening was conducted for the first 4 weeks of storage. Purging with Ar (AN) results in alkalization of the RBC and increased glucose consumption. The addition of 5% CO2 to the purging gas prevented CO2 loss with an equivalent starting and final pH and lactate to control bags (p > 0.5, Days 0-21). ATP levels are higher in AN[CO2 ] (p < 0.0001). DPG was maintained beyond 2 weeks in the AN arm (p < 0.0001). Surprisingly, DPG was lost at the same rate in both control and AN[CO2 ] arms (p = 0.6). Maintenance of ATP in the AN[CO2 ] arm demonstrates that ATP production is not solely a function of the pH effect on glycolysis. CO2 in anaerobic storage prevented the maintenance of DPG, and DPG production appears to be pH dependent. CO2 as well as O2 depletion provides metabolic advantage for stored RBCs. © 2015 AABB.

  15. Microbial community dynamics in batch high-solid anaerobic digestion of food waste under mesophilic conditions.

    PubMed

    Yi, Jing; Dong, Bin; Xue, Yonggang; Li, Ning; Gao, Peng; Zhao, Yuxin; Dai, Lingling; Dai, Xiaohu

    2014-02-28

    Microbial community shifts, associated with performance data, were investigated in an anaerobic batch digester treating high-solid food waste under mesophilic conditions using, a combination of molecular techniques and chemical analysis methods. The batch process was successfully operated with an organic removal efficiency of 44.5% associated with a biogas yield of 0.82 L/g VSremoval. Microbial community structures were examined by denaturing gel gradient electrophoresis. Clostridium and Symbiobacterium organisms were suggested to be mainly responsible for the organic matter catabolism in hydrolysis and acidogenesis reactions. The dynamics of archaeal and methanogenic populations were monitored using real-time PCR targeting 16S rRNA genes. Methanosarcina was the predominant methanogen, suggesting that the methanogenesis took place mainly via an aceticlastic pathway. Hydrogenotrophic methanogens were also supported in high-solid anaerobic digestion of food waste through syntrophism with syntrophic bacterium. Microbial community shifts showed good agreement with the performance parameters in anaerobic digestion, implying the possibility of diagnosing a high-solid anaerobic digestion process by monitoring microbial community shifts. On the other hand, the batch results could be relevant to the start-up period of a continuous system and could also provide useful information to set up a continuous operation.

  16. Physiological requirements for growth and competitiveness of Dekkera bruxellensis under oxygen-limited or anaerobic conditions.

    PubMed

    Blomqvist, Johanna; Nogué, Violeta Sànchez; Gorwa-Grauslund, Marie; Passoth, Volkmar

    2012-07-01

    The effect of glucose and oxygen limitation on the growth and fermentation performances of Dekkera bruxellensis was investigated in order to understand which factors favour its propagation in ethanol or wine plants. Although D. bruxellensis has been described as a facultative anaerobe, no growth was observed in mineral medium under complete anaerobiosis while growth was retarded under severe oxygen limitation. In a continuous culture with no gas inflow, glucose was not completely consumed, most probably due to oxygen limitation. When an air/nitrogen mixture (O(2)-content ca. 5%) was sparged to the culture, growth became glucose-limited. In co-cultivations with Saccharomyces cerevisiae, ethanol yields/g consumed sugar were not affected by the co-cultures as compared to the pure cultures. However, different population responses were observed in both systems. In oxygen-limited cultivation, glucose was depleted within 24 h after challenging with S. cerevisiae and both yeast populations were maintained at a stable level. In contrast, the S. cerevisiae population constantly decreased to about 1% of its initial cell number in the sparged glucose-limited fermentation, whereas the D. bruxellensis population remained constant. To identify the requirements of D. bruxellensis for anaerobic growth, the yeast was cultivated in several nitrogen sources and with the addition of amino acids. Yeast extract and most of the supplied amino acids supported anaerobic growth, which points towards a higher nutrient demand for D. bruxellensis compared to S. cerevisiae in anaerobic conditions. Copyright © 2012 John Wiley & Sons, Ltd.

  17. TBA biodegradation in surface-water sediments under aerobic and anaerobic conditions

    USGS Publications Warehouse

    Bradley, P.M.; Landmeyer, J.E.; Chapelle, F.H.

    2002-01-01

    The potential for [U-14C] TBA biodegradation was examined in laboratory microcosms under a range of terminal electron accepting conditions. TBA mineralization to CO2 was substantial in surface-water sediments under oxic, denitrifying, or Mn(IV)-reducing conditions and statistically significant but low under SO4-reducing conditions. Thus, anaerobic TBA biodegradation may be a significant natural attenuation mechanism for TBA in the environment, and stimulation of in situ TBA bioremediation by addition of suitable terminal electron acceptors may be feasible. No degradation of [U-14C] TBA was observed under methanogenic or Fe(III)-reducing conditions.

  18. Biodegradation of soluble aromatic compounds of jet fuel under anaerobic conditions: laboratory batch experiments.

    PubMed

    Zheng, Z; Breedveld, G; Aagaard, P

    2001-11-01

    Laboratory batch experiments were performed with contaminated aquifer sediments and four soluble aromatic components of jet fuel to assess their biodegradation under anaerobic conditions. The biodegradation of four aromatic compounds, toluene, o-xylene, 1,2,4-trimethylbenzene (TMB), and naphthalene, separately or together, was investigated under strictly anaerobic conditions in the dark for a period of 160 days. Of the aromatic compounds, toluene and o-xylene were degraded both as a single substrate and in a mixture with the other aromatic compounds, while TMB was not biodegraded as a single substrate, but was biodegraded in the presence of the other aromatic hydrocarbons. Substrate interaction is thus significant in the biodegradation of TMB. Biodegradation of naphthalene was not observed, either as a single substrate or in a mixture of other aromatic hydrocarbons. Although redox conditions were dominated by iron reduction, a clear relation between degradation and sulfate reduction was observed. Methanogenesis took place during the later stages of incubation. However, the large background of Fe(II) masked the increase of Fe(II) concentration due to iron reduction. Thus, although microbial reduction of Fe(III) is an important process, the evidence is not conclusive. Our results have shown that a better understanding of the degradation of complex mixtures of hydrocarbons under anaerobic conditions is important in the application of natural attenuation as a remedial method for soil and groundwater contamination.

  19. Anionic metabolite biosynthesis enhanced by potassium under dark, anaerobic conditions in cyanobacteria

    PubMed Central

    Ueda, Sakiko; Kawamura, Yuhki; Iijima, Hiroko; Nakajima, Mitsuharu; Shirai, Tomokazu; Okamoto, Mami; Kondo, Akihiko; Hirai, Masami Yokota; Osanai, Takashi

    2016-01-01

    Potassium (K+) is an essential macronutrient for all living organisms including cyanobacteria. Cyanobacteria are a group of bacteria performing oxygenic photosynthesis, widely studied in basic and applied sciences. The primary metabolism of the unicellular cyanobacterium Synechocystis sp. PCC 6803 is altered by environmental conditions, and it excretes organic acids and hydrogen under dark, anaerobic conditions. Here we demonstrated that K+ widely changes the primary carbon metabolism of this cyanobacterium. Succinate and lactate excretion from the cells incubated under dark, anaerobic conditions was enhanced in the presence of K+, while hydrogen production was repressed. The addition of K+ and the genetic manipulation of acetate kinase AckA and an RNA polymerase sigma factor SigE additively increased succinate and lactate production to 141.0 and 217.6 mg/L, which are 11 and 46 times, compared to the wild-type strain without K+, respectively. Intracellular levels of 2-oxoglutarate, succinate, fumarate, and malate increased by K+ under dark, anaerobic conditions. This study provides the evidence of the considerable effect of K+ on the biosynthesis of anionic metabolites in a unicellular cyanobacterium. PMID:27576448

  20. Continuous Drip Flow System to Develop Biofilm of E. faecalis under Anaerobic Conditions

    PubMed Central

    Gonzalez, Ana Maria; Corpus, Erika; Silva-Herzog, Daniel; Aragon-Piña, Antonio; Cohenca, Nestor

    2014-01-01

    Purpose. To evaluate a structurally mature E. faecalis biofilm developed under anaerobic/dynamic conditions in an in vitro system. Methods. An experimental device was developed using a continuous drip flow system designed to develop biofilm under anaerobic conditions. The inoculum was replaced every 24 hours with a fresh growth medium for up to 10 days to feed the system. Gram staining was done every 24 hours to control the microorganism purity. Biofilms developed under the system were evaluated under the scanning electron microscope (SEM). Results. SEM micrographs demonstrated mushroom-shaped structures, corresponding to a mature E. faecalis biofilm. In the mature biofilm bacterial cells are totally encased in a polymeric extracellular matrix. Conclusions. The proposed in vitro system model provides an additional useful tool to study the biofilm concept in endodontic microbiology, allowing for a better understanding of persistent root canal infections. PMID:25371913

  1. Theoretical analysis of municipal solid waste treatment by leachate recirculation under anaerobic and aerobic conditions.

    PubMed

    van Turnhout, André G; Brandstätter, Christian; Kleerebezem, Robbert; Fellner, Johann; Heimovaara, Timo J

    2017-10-07

    Long-term emissions of Municipal Solid Waste (MSW) landfills are a burden for future generations because of the required long-term aftercare. To shorten aftercare, treatment methods have to be developed that reduce long-term emissions. A treatment method that reduces emissions at a lysimeter scale is re-circulation of leachate. However, its effectiveness at the field scale still needs to be demonstrated. Field scale design can be improved by theoretical understanding of the processes that control the effectiveness of leachate recirculation treatment. In this study, the simplest and most fundamental sets of processes are distilled that describe the emission data measured during aerobic and anaerobic leachate recirculation in lysimeters. A toolbox is used to select essential processes with objective performance criteria produced by Bayesian statistical analysis. The controlling processes indicate that treatment efficiency is mostly affected by how homogeneously important reactants are spread through the MSW during treatment. A more homogeneous spread of i.e. oxygen or methanogens increases the total amount of carbon degraded. Biodegradable carbon removal is highest under aerobic conditions, however, the hydrolysis rate constant is lower which indicates that hydrolysis is not enhanced intrinsically in aerobic conditions. Controlling processes also indicate that nitrogen removal via sequential nitrification and denitrification is plausible under aerobic conditions as long as sufficient biodegradable carbon is present in the MSW. Major removal pathways for carbon and nitrogen are indicated which are important for monitoring treatment effectiveness at a field scale. Optimization strategies for field scale application of treatments are discussed. Copyright © 2017. Published by Elsevier Ltd.

  2. De novo assembly and comparative transcriptome analysis of Euglena gracilis in response to anaerobic conditions.

    PubMed

    Yoshida, Yuta; Tomiyama, Takuya; Maruta, Takanori; Tomita, Masaru; Ishikawa, Takahiro; Arakawa, Kazuharu

    2016-03-03

    The phytoflagellated protozoan, Euglena gracilis, has been proposed as an attractive feedstock for the accumulation of valuable compounds such as β-1,3-glucan, also known as paramylon, and wax esters. The production of wax esters proceeds under anaerobic conditions, designated as wax ester fermentation. In spite of the importance and usefulness of Euglena, the genome and transcriptome data are currently unavailable, though another research group has recently published E.gracilis transcriptome study during our submission. We herein performed an RNA-Seq analysis to provide a comprehensive sequence resource and some insights into the regulation of genes including wax ester metabolism by comparative transcriptome analysis of E.gracilis under aerobic and anaerobic conditions. The E.gracilis transcriptome analysis was performed using the Illumina platform and yielded 90.3 million reads after the filtering steps. A total of 49,826 components were assembled and identified as a reference sequence of E.gracilis, of which 26,479 sequences were considered to be potentially expressed (having FPKM value of greater than 1). Approximately half of all components were estimated to be regulated in a trans-splicing manner, with the addition of protruding spliced leader sequences. Nearly 40 % of 26,479 sequences were annotated by similarity to Swiss-Prot database using the BLASTX program. A total of 2080 transcripts were identified as differentially expressed genes (DEGs) in response to anaerobic treatment for 24 h. A comprehensive pathway enrichment analysis using the KEGG pathway revealed that the majority of DEGs were involved in photosynthesis, nucleotide metabolism, oxidative phosphorylation, fatty acid metabolism. We successfully identified a candidate gene set of paramylon and wax esters, including novel β-1,3-glucan and wax ester synthases. A comparative expression analysis of aerobic- and anaerobic-treated E.gracilis cells indicated that gene expression changes in these

  3. Evaluation of the improvement of sonication pre-treatment in the anaerobic digestion of sewage sludge.

    PubMed

    Martín, María Ángeles; González, Inmaculada; Serrano, Antonio; Siles, José Ángel

    2015-01-01

    Sewage sludge is a polluting and hazardous waste generated in wastewater treatment plants with severe management problems. The high content in heavy metal, pathogens and micropolluting compounds limit the implementation of the available management methods. Anaerobic digestion could be an interesting treatment method, but must be improved since the biomethanisation of sewage sludge entails low biodegradability and low methane production. A sonication pre-treatment at lab scale is proposed to increase the organic matter solubilisation of sewage sludge and enhance the biomethanisation yield. Sonication time was optimised by analysing the physicochemical characteristics of sewage sludge (both total and soluble fraction) at different pre-treatment times. The pre-treatment time was fixed at 45 min under the study conditions given that the solubilisation of organic matter did not increase significantly at lower sonication times, whereas the concentration of total nitrogen increased markedly at higher times. The volatile fatty acids generation rate was also evaluated for the pre-treatment conditions. The anaerobic digestion of untreated and pre-treated sewage sludge was subsequently compared and promising results were obtained for loads of 1.0 g VS/L (VS, total volatile solids). The methane yield coefficient increased from 88 to 172 mLSTP/g VS (STP, 0 °C, 1 atm) after the pre-treatment, while biodegradability was found to be around 81% (in VS). Moreover, the allowed organic loading rate and methane production rate observed for the sewage sludge reached values of up to 4.1 kg VS/m(3)·d and 1270 LSTP/m(3)·d, respectively.

  4. Coenzyme B12 can be produced by engineered Escherichia coli under both anaerobic and aerobic conditions.

    PubMed

    Ko, Yeounjoo; Ashok, Somasundar; Ainala, Satish Kumar; Sankaranarayanan, Mugesh; Chun, Ah Yeong; Jung, Gyoo Yeol; Park, Sunghoon

    2014-12-01

    Coenzyme B12 (Vitamin B12 ) is one of the most complex biomolecules and an essential cofactor required for the catalytic activity of many enzymes. Pseudomonas denitrificans synthesizes coenzyme B12 in an oxygen-dependent manner using a pathway encoded by more than 25 genes that are located in six different operons. Escherichia coli, a robust and suitable host for metabolic engineering was used to produce coenzyme B12 . These genes were cloned into three compatible plasmids and expressed heterologously in E. coli BL21 (DE3). Real-time PCR, SDS-PAGE analysis and bioassay showed that the recombinant E. coli expressed the coenzyme B12 synthetic genes and successfully produced coenzyme B12 . However, according to the quantitative determination by inductively coupled plasma-mass spectrometry, the amount of coenzyme B12 produced by the recombinant E. coli (0.21 ± 0.02 μg/g cdw) was approximately 13-fold lower than that by P. denitrificans (2.75 ± 0.22 μg/g cdw). Optimization of the culture conditions to improve the production of coenzyme B12 by the recombinant E. coli was successful, and the highest titer (0.65 ± 0.03 μg/g cdw) of coenzyme B12 was obtained. Interestingly, although the synthesis of coenzyme B12 in P. denitrificans is strictly oxygen-dependent, the recombinant E. coli could produce coenzyme B12 under anaerobic conditions. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Cadmium removal by Euglena gracilis is enhanced under anaerobic growth conditions.

    PubMed

    Santiago-Martínez, M Geovanni; Lira-Silva, Elizabeth; Encalada, Rusely; Pineda, Erika; Gallardo-Pérez, Juan Carlos; Zepeda-Rodriguez, Armando; Moreno-Sánchez, Rafael; Saavedra, Emma; Jasso-Chávez, Ricardo

    2015-05-15

    The facultative protist Euglena gracilis, a heavy metal hyper-accumulator, was grown under photo-heterotrophic and extreme conditions (acidic pH, anaerobiosis and with Cd(2+)) and biochemically characterized. High biomass (8.5×10(6)cellsmL(-1)) was reached after 10 days of culture. Under anaerobiosis, photosynthetic activity built up a microaerophilic environment of 0.7% O₂, which was sufficient to allow mitochondrial respiratory activity: glutamate and malate were fully consumed, whereas 25-33% of the added glucose was consumed. In anaerobic cells, photosynthesis but not respiration was activated by Cd(2+) which induced higher oxidative stress. Malondialdehyde (MDA) levels were 20 times lower in control cells under anaerobiosis than in aerobiosis, although Cd(2+) induced a higher MDA production. Cd(2+) stress induced increased contents of chelating thiols (cysteine, glutathione and phytochelatins) and polyphosphate. Biosorption (90%) and intracellular accumulation (30%) were the mechanisms by which anaerobic cells removed Cd(2+) from medium, which was 36% higher versus aerobic cells. The present study indicated that E. gracilis has the ability to remove Cd(2+) under anaerobic conditions, which might be advantageous for metal removal in sediments from polluted water bodies or bioreactors, where the O₂ concentration is particularly low.

  6. Influence of operational conditions on biofilm specific activity of an anaerobic fluidized bed reactor.

    PubMed

    García-Morales, J L; Romero, L I; Sales, D

    2003-01-01

    A key parameter in water and wastewater treatment technology is the biomass activity in terms of substrate removal ability. The effects of organic load rate and percentage of bed expansion on biofilm specific methanogenic activity were determined in an anaerobic fluidized bed reactor treating wine-distillery wastes in the thermophilic range (55 degrees C). The proposed activity tests are highly reproducible: an experiment with three identical tests has shown that the standard deviation with respect to the mean values is less than 3%. Specific tests are applied to measure the maximum methanogenic activities of the biomass carrier in lab-scale anaerobic biofilm reactors. These tests have been successfully applied for monitoring the support colonization process and the evolution of biofilm activity in reactors, anaerobic filter and fluidized bed, with different operating conditions. The results show a dependence between the percentage of bed expansion and the specific activity of methanogenic microbiote on biofilm. There is a relationship between the percentage of bed expansion, the sheer stress on the biofilm and the hydrodynamic conditions in the system. Initial biofilm detachment can be compensated with the increase of biomass and of its activity due to the reduction of the substrate diffusional limitations to the microorganism growth inside the support pores.

  7. A Hidden Transhydrogen Activity of a FMN-Bound Diaphorase under Anaerobic Conditions

    PubMed Central

    Collins, John; Zhang, Ting; Huston, Scott; Sun, Fangfang; Zhang, Y.-H. Percival; Fu, Jinglin

    2016-01-01

    Background Redox cofactors of NADH/NADPH participate in many cellular metabolic pathways for facilitating the electron transfer from one molecule to another in redox reactions. Transhydrogenase plays an important role in linking catabolism and anabolism, regulating the ratio of NADH/NADPH in cells. The cytoplasmic transhydrogenases could be useful to engineer synthetic biochemical pathways for the production of high-value chemicals and biofuels. Methodology/Principal Findings A transhydrogenase activity was discovered for a FMN-bound diaphorase (DI) from Geobacillus stearothermophilus under anaerobic conditions. The DI-catalyzed hydride exchange were monitored and characterized between a NAD(P)H and a thio-modified NAD+ analogue. This new function of DI was demonstrated to transfer a hydride from NADPH to NAD+ that was consumed by NAD-specific lactate dehydrogenase and malic dehydrogenase. Conclusions/Significance We discover a novel transhydrogenase activity of a FMN-DI by stabilizing the reduced state of FMNH2 under anaerobic conditions. FMN-DI was demonstrated to catalyze the hydride transfer between NADPH and NAD+. In the future, it may be possible to incorporate this FMN-DI into synthetic enzymatic pathways for balancing NADH generation and NADPH consumption for anaerobic production of biofuels and biochemicals. PMID:27145082

  8. Interrogation of Chesapeake Bay sediment microbial communities for intrinsic alkane-utilizing potential under anaerobic conditions.

    PubMed

    Johnson, Jamie M; Wawrik, Boris; Isom, Catherine; Boling, Wilford B; Callaghan, Amy V

    2015-02-01

    Based on the transient exposure of Chesapeake Bay sediments to hydrocarbons and the metabolic versatility of known anaerobic alkane-degrading microorganisms, it was hypothesized that distinct Bay sediment communities, governed by geochemical gradients, would have intrinsic alkane-utilizing potential under sulfate-reducing and/or methanogenic conditions. Sediment cores were collected along a transect of the Bay. Community DNA was interrogated via pyrosequencing of 16S rRNA genes, PCR of anaerobic hydrocarbon activation genes, and qPCR of 16S rRNA genes and genes involved in sulfate reduction/methanogenesis. Site sediments were used to establish microcosms amended with n-hexadecane under sulfate-reducing and methanogenic conditions. Sequencing of 16S rRNA genes indicated that sediments associated with hypoxic water columns contained significantly greater proportions of Bacteria and Archaea consistent with syntrophic degradation of organic matter and methanogenesis compared to less reduced sediments. Microbial taxa frequently associated with hydrocarbon-degrading communities were found throughout the Bay, and the genetic potential for hydrocarbon metabolism was demonstrated via the detection of benzyl-(bssA) and alkylsuccinate synthase (assA) genes. Although microcosm studies did not indicate sulfidogenic alkane degradation, the data suggested that methanogenic conversion of alkanes was occurring. These findings highlight the potential role that anaerobic microorganisms could play in the bioremediation of hydrocarbons in the Bay.

  9. Identification of crude-oil components and microorganisms that cause souring under anaerobic conditions.

    PubMed

    Hasegawa, R; Toyama, K; Miyanaga, K; Tanji, Y

    2014-02-01

    Oil souring has important implications with respect to energy resources. Understanding the physiology of the microorganisms that play a role and the biological mechanisms are both important for the maintenance of infrastructure and mitigation of corrosion processes. The objective of this study was to identify crude-oil components and microorganisms in oil-field water that contribute to crude-oil souring. To identify the crude-oil components and microorganisms that are responsible for anaerobic souring in oil reservoirs, biological conversion of crude-oil components under anaerobic conditions was investigated. Microorganisms in oil field water in Akita, Japan degraded alkanes and aromatics to volatile fatty acids (VFAs) under anaerobic conditions, and fermenting bacteria such as Fusibacter sp. were involved in VFA production. Aromatics such as toluene and ethylbenzene were degraded by sulfate-reducing bacteria (Desulfotignum sp.) via the fumarate-addition pathway and not only degradation of VFA but also degradation of aromatics by sulfate-reducing bacteria was the cause of souring. Naphthenic acid and 2,4-xylenol were not converted.

  10. Kinetics and thermodynamics of biodegradation of hydrolyzed polyacrylamide under anaerobic and aerobic conditions.

    PubMed

    Zhao, Lanmei; Bao, Mutai; Yan, Miao; Lu, Jinren

    2016-09-01

    Kinetics and thermodynamics of hydrolyzed polyacrylamide (HPAM) biodegradation in anaerobic and aerobic activated sludge biochemical treatment systems were explored to determine the maximum rate and feasibility of HPAM biodegradation. The optimal nutrient proportions for HPAM biodegradation were determined to be 0.08g·L(-1) C6H12O6, 1.00g·L(-1) NH4Cl, 0.36g·L(-1) NaH2PO4 and 3.00g·L(-1) K2HPO4 using response surface methodology (RSM). Based on the kinetics, the maximum HPAM biodegradation rates were 16.43385mg·L(-1)·d(-1) and 2.463mg·L(-1)·d(-1) in aerobic and anaerobic conditions, respectively. The activation energy (Ea) of the aerobic biodegradation was 48.9897kJ·mol(-1). Entropy changes (ΔS) of biochemical treatment system decreased from 216.21J·K(-1) to 2.39J·K(-1). Thermodynamic windows of opportunity for HPAM biodegradation were drawn. And it demonstrated HPAM was biodegraded into acetic acid and CO2 under laboratory conditions. Growth-process equations for functional bacteria anaerobically grown on polyacrylic acid were constructed and it confirmed electron equivalence between substrate and product. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Long-term geochemical evolution of acidic mine wastes under anaerobic conditions.

    PubMed

    Lu, Wenzhou; Lin, Chuxia; Ma, Yingqun

    2013-08-01

    A nearly 5-year anaerobic incubation experiment was conducted to observe the geochemical evolution of an acidic mine waste. Long-term storage of the mine waste under strict anaerobic conditions caused marked increase in aqueous sulfur, while aqueous iron showed no remarkable change. Co-existing oxidation and reduction of elemental sulfur appeared to play a central role in controlling the evolutionary trends of aqueous sulfur and iron. Addition of organic matter increased the aqueous Fe concentration, possibly due to enhanced iron mobilization by microbial iron reduction and increased iron solubility by forming organically complexed Fe species. Further addition of CaCO3 resulted in immobilization of aqueous iron and sulfur due to elevated pH and gypsum formation. The chemical behaviors of environmentally significant metals were markedly affected by the added organic matter; Al, Cr, Cu, Ni and Zn tended to be immobilized probably due to elevated pH and complexation with insoluble organic molecules, while As and Pb tended to be mobilized. Jarosite exhibited high stability after nearly 5 years of anaerobic incubation and even under circumneutral pH conditions. Long-term weathering of aluminosilicate through acid attack raised pH, while continuous reaction between the added CaCO3 and mine waste-borne stored acid decreased pH.

  12. Improving Care for Chronic Conditions

    PubMed Central

    Mattke, Soeren; Mengistu, Tewodaj; Klautzer, Lisa; Sloss, Elizabeth M.; Brook, Robert H.

    2015-01-01

    Abstract The need for better management of chronic conditions is urgent. About 141 million people in the United States were living with one or more chronic conditions in 2010, and this number is projected to increase to 171 million by 2030. To address this challenge, many health plans have piloted and rolled out innovative approaches to improving care for their members with chronic conditions. This article documents the current range of chronic care management services, identifies best practices and industry trends, and examines factors in the plans' operating environment that limit their ability to optimize chronic care programs. The authors conducted telephone surveys with a representative sample of health plans and made in-depth case studies of six plans. All plans in the sample provide a wide range of products and services around chronic care, including wellness/lifestyle management programs for healthy members, disease management for members with common chronic conditions, and case management for high-risk members regardless of their underlying condition. Health plans view these programs as a “win-win” situation and believe that they improve care for their most vulnerable members and reduce cost of coverage. Plans are making their existing programs more patient-centric and are integrating disease and case management, and sometimes lifestyle management and behavioral health, into a consolidated chronic care management program, believing that this will increase patient engagement and prevent duplication of services and missed opportunities. PMID:28083379

  13. Intermittent hypoxic training improves anaerobic performance in competitive swimmers when implemented into a direct competition mesocycle.

    PubMed

    Czuba, Miłosz; Wilk, Robert; Karpiński, Jakub; Chalimoniuk, Małgorzata; Zajac, Adam; Langfort, Józef

    2017-01-01

    The main objective of this research was to evaluate the efficacy of intermittent hypoxic training (IHT) on anaerobic and aerobic capacity and swimming performance in well-trained swimmers. Sixteen male swimmers were randomly divided into a hypoxia (H) group (n = 8), which trained in a normobaric hypoxia environment, and a control (C) group (n = 8), which exercised under normoxic conditions. However, one participant left the study without explanation. During the experiment group H trained on land twice per week in simulated hypoxia (FiO2 = 15.5%, corresponding to 2,500 m a.s.l); however, they conducted swim training in normoxic conditions. Group C performed the same training program under normoxic conditions. The training program included four weekly microcyles, followed by three days of recovery. During practice sessions on land, the swimmers performed 30 second sprints on an arm-ergometer, alternating with two minute high intensity intervals on a lower limb cycle ergometer. The results showed that the training on land caused a significant (p<0.05) increase in absolute maximal workload (WRmax) by 7.4% in group H and by 3.2% in group C and relative values of VO2max by 6.9% in group H and 3.7% in group C. However, absolute values of VO2max were not significantly changed. Additionally, a significant (p<0.05) increase in mean power (Pmean) during the first (11.7%) and second (11.9%) Wingate tests was only observed in group H. The delta values of lactate concentration (ΔLA) after both Wingate tests were significantly (p<0.05) higher in comparison to baseline levels by 28.8% in group H. Opposite changes were observed in delta values of blood pH (ΔpH) after both Wingate tests in group H, with a significant decrease in values of ΔpH by 33.3%. The IHT caused a significant (p<0.05) improvement in 100m and 200m swimming performance, by 2.1% and 1.8%, respectively in group H. Training in normoxia (group C), resulted in a significant (p<0.05) improvement of swimming

  14. Intermittent hypoxic training improves anaerobic performance in competitive swimmers when implemented into a direct competition mesocycle

    PubMed Central

    Wilk, Robert; Karpiński, Jakub; Chalimoniuk, Małgorzata; Zajac, Adam; Langfort, Józef

    2017-01-01

    The main objective of this research was to evaluate the efficacy of intermittent hypoxic training (IHT) on anaerobic and aerobic capacity and swimming performance in well-trained swimmers. Sixteen male swimmers were randomly divided into a hypoxia (H) group (n = 8), which trained in a normobaric hypoxia environment, and a control (C) group (n = 8), which exercised under normoxic conditions. However, one participant left the study without explanation. During the experiment group H trained on land twice per week in simulated hypoxia (FiO2 = 15.5%, corresponding to 2,500 m a.s.l); however, they conducted swim training in normoxic conditions. Group C performed the same training program under normoxic conditions. The training program included four weekly microcyles, followed by three days of recovery. During practice sessions on land, the swimmers performed 30 second sprints on an arm-ergometer, alternating with two minute high intensity intervals on a lower limb cycle ergometer. The results showed that the training on land caused a significant (p<0.05) increase in absolute maximal workload (WRmax) by 7.4% in group H and by 3.2% in group C and relative values of VO2max by 6.9% in group H and 3.7% in group C. However, absolute values of VO2max were not significantly changed. Additionally, a significant (p<0.05) increase in mean power (Pmean) during the first (11.7%) and second (11.9%) Wingate tests was only observed in group H. The delta values of lactate concentration (ΔLA) after both Wingate tests were significantly (p<0.05) higher in comparison to baseline levels by 28.8% in group H. Opposite changes were observed in delta values of blood pH (ΔpH) after both Wingate tests in group H, with a significant decrease in values of ΔpH by 33.3%. The IHT caused a significant (p<0.05) improvement in 100m and 200m swimming performance, by 2.1% and 1.8%, respectively in group H. Training in normoxia (group C), resulted in a significant (p<0.05) improvement of swimming

  15. Improvement of anaerobic digestion of waste-activated sludge by using H₂O₂ oxidation, electrolysis, electro-oxidation and thermo-alkaline pretreatments.

    PubMed

    Feki, Emna; Khoufi, Sonia; Loukil, Slim; Sayadi, Sami

    2015-10-01

    Disintegration of municipal waste-activated sludge (WAS) is regarded as a prerequisite of the anaerobic digestion process to reduce sludge volume and improve biogas yield. Pretreatment of WAS using thermo-alkaline (TA), H2O2 oxidation, electrolysis and electro-oxidation (EO) processes were investigated and compared in term of COD solubilization and biogas production. For each pretreatment, the influences of different operational variables were studied in detail. At optimum conditions, EO gave the maximum COD solubilization (28 %). The effects of pretreatments under the optimum conditions on anaerobic digestion were experienced with biochemical methane potential assay. Significant increases in biogas yield up to 78 and 40 % were observed respectively in the EO and TA pretreated samples compared to raw sludge. Results clearly revealed that the application of EO is a significant alternative method for the improvement of WAS anaerobic digestion.

  16. Can the anaerobic potentially mineralizable nitrogen test improve predictions of fertilizer nitrogen rates in the Cornbelt?

    USDA-ARS?s Scientific Manuscript database

    Correctly estimating the amount of mineralizable nitrogen (N) can enhance nitrogen use efficiency. The anaerobic potentially mineralizable nitrogen (PMNAn) test is a tool that may help improve predictions of N uptake, grain yield, and the economical optimum nitrogen rate (EONR) of corn (Zea mays L...

  17. Unconventional anaerobic digester designs for improving methane yields from sea kelp

    SciTech Connect

    Fannin, K F; Srivastava, V J; Chynoweth, D P

    1982-01-01

    Studies were performed as part of an ongoing comprehensive research program to develop and optimize the anaerobic digestion process for producing methane from sea kelp (Macrocystis pyrifera). Laboratory-scale studies focused on digester design and operating techniques applicable toward the goal of increasing methane yields and production rates over those observed in previous studies using conventional stirred tank reactors (STR). Two unconventional anaerobic digesters, an upflow solids reactor and a baffle flow reactor, were used to study the anaerobic digestion performance of kelp; both digesters permit solids retention times that are longer than the hydraulic retention times. The performance of the unconventional digesters was compared with that of the STR on the basis of methane yield and process stability. These studies demonstrated that, although digester performance was markedly affected by kelp variability, the methane yield in both unconventional digesters exceeded 70% of the theoretical yield and was substantialy higher than that of the STR. Utilization of simple digester designs that promoted long solids retention times improved the anaerobic digester performance significantly over that observed in conventional anaerobic digestion processes.

  18. Waste-Activated Sludge Fermentation for Polyacrylamide Biodegradation Improved by Anaerobic Hydrolysis and Key Microorganisms Involved in Biological Polyacrylamide Removal

    PubMed Central

    Dai, Xiaohu; Luo, Fan; Zhang, Dong; Dai, Lingling; Chen, Yinguang; Dong, Bin

    2015-01-01

    During the anaerobic digestion of dewatered sludge, polyacrylamide (PAM), a chemical conditioner, can usually be consumed as a carbon and nitrogen source along with other organic matter (e.g., proteins and carbohydrates in the sludge). However, a significant accumulation of acrylamide monomers (AMs) was observed during the PAM biodegradation process. To improve the anaerobic hydrolysis of PAM, especially the amide hydrolysis process, and to avoid the generation of the intermediate product AM, a new strategy is reported herein that uses an initial pH of 9, 200 mg COD/L of PAM and a fermentation time of 17 d. First, response surface methodology (RSM) was applied to optimize PAM removal in the anaerobic digestion of the sludge. The biological hydrolysis of PAM reached 86.64% under the optimal conditions obtained from the RSM. Then, the mechanisms for the optimized parameters that significantly improved the biological hydrolysis of PAM were investigated by the synergistic effect of the main organic compounds in the sludge, the floc size distribution, and the enzymatic activities. Finally, semi-continuous-flow experiments for a microbial community study were investigated based on the determination of key microorganisms involved in the biological hydrolysis of PAM. PMID:26144551

  19. Waste-Activated Sludge Fermentation for Polyacrylamide Biodegradation Improved by Anaerobic Hydrolysis and Key Microorganisms Involved in Biological Polyacrylamide Removal.

    PubMed

    Dai, Xiaohu; Luo, Fan; Zhang, Dong; Dai, Lingling; Chen, Yinguang; Dong, Bin

    2015-07-06

    During the anaerobic digestion of dewatered sludge, polyacrylamide (PAM), a chemical conditioner, can usually be consumed as a carbon and nitrogen source along with other organic matter (e.g., proteins and carbohydrates in the sludge). However, a significant accumulation of acrylamide monomers (AMs) was observed during the PAM biodegradation process. To improve the anaerobic hydrolysis of PAM, especially the amide hydrolysis process, and to avoid the generation of the intermediate product AM, a new strategy is reported herein that uses an initial pH of 9, 200 mg COD/L of PAM and a fermentation time of 17 d. First, response surface methodology (RSM) was applied to optimize PAM removal in the anaerobic digestion of the sludge. The biological hydrolysis of PAM reached 86.64% under the optimal conditions obtained from the RSM. Then, the mechanisms for the optimized parameters that significantly improved the biological hydrolysis of PAM were investigated by the synergistic effect of the main organic compounds in the sludge, the floc size distribution, and the enzymatic activities. Finally, semi-continuous-flow experiments for a microbial community study were investigated based on the determination of key microorganisms involved in the biological hydrolysis of PAM.

  20. Improved ADM1 model for anaerobic digestion process considering physico-chemical reactions.

    PubMed

    Zhang, Yang; Piccard, Sarah; Zhou, Wen

    2015-11-01

    The "Anaerobic Digestion Model No. 1" (ADM1) was modified in the study by improving the bio-chemical framework and integrating a more detailed physico-chemical framework. Inorganic carbon and nitrogen balance terms were introduced to resolve the discrepancies in the original bio-chemical framework between the carbon and nitrogen contents in the degraders and substrates. More inorganic components and solids precipitation processes were included in the physico-chemical framework of ADM1. The modified ADM1 was validated with the experimental data and used to investigate the effects of calcium ions, magnesium ions, inorganic phosphorus and inorganic nitrogen on anaerobic digestion in batch reactor. It was found that the entire anaerobic digestion process might exist an optimal initial concentration of inorganic nitrogen for methane gas production in the presence of calcium ions, magnesium ions and inorganic phosphorus.

  1. Sulfate-reducing bacteria mediate thionation of diphenylarsinic acid under anaerobic conditions.

    PubMed

    Guan, Ling; Shiiya, Ayaka; Hisatomi, Shihoko; Fujii, Kunihiko; Nonaka, Masanori; Harada, Naoki

    2015-02-01

    Diphenylarsinic acid (DPAA) is often found as a toxic intermediate metabolite of diphenylchloroarsine or diphenylcyanoarsine that were produced as chemical warfare agents and were buried in soil after the World Wars. In our previous study Guan et al. (J Hazard Mater 241-242:355-362, 2012), after application of sulfate and carbon sources, anaerobic transformation of DPAA in soil was enhanced with the production of diphenylthioarsinic acid (DPTAA) as a main metabolite. This study aimed to isolate and characterize anaerobic soil microorganisms responsible for the metabolism of DPAA. First, we obtained four microbial consortia capable of transforming DPAA to DPTAA at a high transformation rate of more than 80% after 4 weeks of incubation. Sequencing for the bacterial 16S rRNA gene clone libraries constructed from the consortia revealed that all the positive consortia contained Desulfotomaculum acetoxidans species. In contrast, the absence of dissimilatory sulfite reductase gene (dsrAB) which is unique to sulfate-reducing bacteria was confirmed in the negative consortia showing no DPAA reduction. Finally, strain DEA14 showing transformation of DPAA to DPTAA was isolated from one of the positive consortia. The isolate was assigned to D. acetoxidans based on the partial 16S rDNA sequence analysis. Thionation of DPAA was also carried out in a pure culture of a known sulfate-reducing bacterial strain, Desulfovibrio aerotolerans JCM 12613(T). These facts indicate that sulfate-reducing bacteria are microorganisms responsible for the transformation of DPAA to DPTAA under anaerobic conditions.

  2. Dry co-digestion of sewage sludge and rice straw under mesophilic and thermophilic anaerobic conditions.

    PubMed

    Chu, Xiangqian; Wu, Guangxue; Wang, Jiaquan; Hu, Zhen-Hu

    2015-12-01

    Dry anaerobic digestion of sewage sludge can recover biogas as energy; however, its low C/N ratio limits it as a single substrate in the anaerobic digestion. Rice straw is an abundant agricultural residue in China, which is rich in carbon and can be used as carbon source. In the present study, the performance of dry co-digestion of sewage sludge and rice straw was investigated under mesophilic (35 °C) and thermophilic (55 °C) conditions. The operational factors impacting dry co-digestion of sewage sludge and rice straw such as C/N ratio, moisture content, and initial pH were explored under mesophilic conditions. The results show that low C/N ratios resulted in a higher biogas production rate, but a lower specific biogas yield; low moisture content of 65 % resulted in the instability of the digestion system and a low specific biogas yield. Initial pH ranging 7.0-9.0 did not affect the performance of the anaerobic digestion. The C/N ratio of 26-29:1, moisture content of 70-80 %, and pH 7.0-9.0 resulted in good performance in the dry mesophilic co-digestion of sewage sludge and rice straw. As compared with mesophilic digestion, thermophilic co-digestion of sewage sludge and rice straw significantly enhanced the degradation efficiency of the substrates and the specific biogas yield (p < 0.05) at the conditions of C/N ratio 26:1, moisture content 80 %, and natural initial pH. Although high concentrations of ammonia-nitrogen (NH4-N, 1500 mg/kg wet weight) were formed during thermophilic digestion, there was no obvious inhibition occurred. The results indicated that rice straw can be used as carbon source for the dry co-digestion of sewage sludge under mesophilic and thermophilic conditions.

  3. Anaerobic digestion of mixed microalgae cultivated in secondary effluent under mesophilic and thermophilic conditions.

    PubMed

    Cea-Barcia, Glenda; Moreno, Gloria; Buitrón, Germán

    2015-01-01

    The anaerobic digestion of mixed indigenous microalgae, grown in a secondary effluent, was evaluated in batch tests at mesophilic (35°C) and thermophilic (50°C) conditions. Under mesophilic conditions, specific methane production varied from 178 to 207 mL CH4/g volatile solids (VS) and the maximum production rate varied from 8.8 to 26.1 mL CH4/(gVS day), depending on the type of microalgae culture. Lower methane parameters were observed in those cultures where Scenedesmus represents more than 95% of the microalge. The culture with the lowest digestion performances under mesophilic conditions was studied under thermophilic conditions. The increase in the incubation temperature significantly increased the specific methane production (390 mL CH4/g VS) and rate (26.0 mL CH4/(gVS day)). However, under thermophilic conditions a lag period of 30 days was observed.

  4. Acyl homoserine lactone-based quorum sensing stimulates biofilm formation by Salmonella Enteritidis in anaerobic conditions.

    PubMed

    Almeida, Felipe Alves de; Pimentel-Filho, Natan de Jesus; Pinto, Uelinton Manoel; Mantovani, Hilário Cuquetto; Oliveira, Leandro Licursi de; Vanetti, Maria Cristina Dantas

    2017-04-01

    Quorum sensing regulates a variety of phenotypes in bacteria including the production of virulence factors. Salmonella spp. have quorum sensing systems mediated by three autoinducers (AI-1, AI-2, and AI-3). The AI-1-mediated system is incomplete in that the bacterium relies on the synthesis of signaling molecules by other microorganisms. This study aimed to evaluate the influence of the AI-1 N-dodecanoyl-DL-homoserine lactone (C12-HSL) on the growth, motility, adhesion, and biofilm formation of Salmonella enterica serovar Enteritidis PT4 578 on a polystyrene surface. Experiments were conducted at 37 °C in anaerobic tryptone soy broth supplemented with C12-HSL and/or a mixture of four synthetic furanones, at the concentration of 50 nM each. The planktonic growth, adhesion, swarming, and twitching motility were not altered in the presence of C12-HSL and/or furanones under anaerobic conditions. However, C12-HSL induced biofilm formation after 36 h of cultivation as determined by quantification of biofilm formation, by enumeration of adhered cells to polystyrene coupons, and finally by imaging the presence of multilayered cells on an epifluorescence microscope. When furanones were present in the medium, an antagonistic effect against C12-HSL on the biofilm development was observed. The results demonstrate an induction of biofilm formation in Salmonella Enteritidis by AI-1 under anaerobic conditions. Considering that Salmonella does not produce AI-1 but respond to it, C12-HSL synthesized by other bacterial species could trigger biofilm formation by this pathogen in conditions that are relevant for its pathogenesis.

  5. Antibiotic Susceptibilities of Pseudomonas aeruginosa Isolates Derived from Patients with Cystic Fibrosis under Aerobic, Anaerobic, and Biofilm Conditions

    PubMed Central

    Hill, Dominic; Rose, Barbara; Pajkos, Aniko; Robinson, Michael; Bye, Peter; Bell, Scott; Elkins, Mark; Thompson, Barbara; MacLeod, Colin; Aaron, Shawn D.; Harbour, Colin

    2005-01-01

    Recent studies have determined that Pseudomonas aeruginosa can live in a biofilm mode within hypoxic mucus in the airways of patients with cystic fibrosis (CF). P. aeruginosa grown under anaerobic and biofilm conditions may better approximate in vivo growth conditions in the CF airways, and combination antibiotic susceptibility testing of anaerobically and biofilm-grown isolates may be more relevant than traditional susceptibility testing under planktonic aerobic conditions. We tested 16 multidrug-resistant isolates of P. aeruginosa derived from CF patients using multiple combination bactericidal testing to compare the efficacies of double and triple antibiotic combinations against the isolates grown under traditional aerobic planktonic conditions, in planktonic anaerobic conditions, and in biofilm mode. Both anaerobically grown and biofilm-grown bacteria were significantly less susceptible (P < 0.01) to single and combination antibiotics than corresponding aerobic planktonically grown isolates. Furthermore, the antibiotic combinations that were bactericidal under anaerobic conditions were often different from those that were bactericidal against the same organisms grown as biofilms. The most effective combinations under all conditions were colistin (tested at concentrations suitable for nebulization) either alone or in combination with tobramycin (10 μg ml−1), followed by meropenem combined with tobramycin or ciprofloxacin. The findings of this study illustrate that antibiotic sensitivities are dependent on culture conditions and highlight the complexities of choosing appropriate combination therapy for multidrug-resistant P. aeruginosa in the CF lung. PMID:16207967

  6. A Portable Anaerobic Microbioreactor Reveals Optimum Growth Conditions for the Methanogen Methanosaeta concilii▿

    PubMed Central

    Steinhaus, Benjamin; Garcia, Marcelo L.; Shen, Amy Q.; Angenent, Largus T.

    2007-01-01

    Conventional studies of the optimum growth conditions for methanogens (methane-producing, obligate anaerobic archaea) are typically conducted with serum bottles or bioreactors. The use of microfluidics to culture methanogens allows direct microscopic observations of the time-integrated response of growth. Here, we developed a microbioreactor (μBR) with ∼1-μl microchannels to study some optimum growth conditions for the methanogen Methanosaeta concilii. The μBR is contained in an anaerobic chamber specifically designed to place it directly onto an inverted light microscope stage while maintaining a N2-CO2 environment. The methanogen was cultured for months inside microchannels of different widths. Channel width was manipulated to create various fluid velocities, allowing the direct study of the behavior and responses of M. concilii to various shear stresses and revealing an optimum shear level of ∼20 to 35 μPa. Gradients in a single microchannel were then used to find an optimum pH level of 7.6 and an optimum total NH4-N concentration of less than 1,100 mg/liter (<47 mg/liter as free NH3-N) for M. concilii under conditions of the previously determined ideal shear stress and pH and at a temperature of 35°C. PMID:17220251

  7. Investigating the nitrification and denitrification kinetics under aerobic and anaerobic conditions by Paracoccus denitrificans ISTOD1.

    PubMed

    Medhi, Kristina; Singhal, Anjali; Chauhan, D K; Thakur, Indu Shekhar

    2017-03-16

    Municipal wastewater contains multiple nitrogen contaminants such as ammonia, nitrate and nitrite. Two heterotrophic nitrifier and aerobic denitrifiers, bacterial isolates ISTOD1 and ISTVD1 were isolated from domestic wastewater. On the basis of removal efficiency of ammonia, nitrate and nitrite under both aerobic and anaerobic conditions, ISTOD1 was selected and identified as Paracoccus denitrificans. Aerobically, NH4(+)-N had maximum specific nitrogen removal rate (Rxi) of 7.6g/gDCW/h and anaerobically, NO3(-)N showed Rxi of 2.5*10(-1)g/g DCW/h. Monod equation described the bioprocess kinetic coefficients, µmax and Ks, obtained by regression. Error functions were calculated to validate the Monod equation experimental data. Aerobic NO3(-)N showed the highest YW of 0.372mg DCW/mg NO3(-)N among the five conditions. ISTOD1 serves as a potential candidate for treating nitrogen rich wastewater using simultaneous nitrification and aerobic denitrification. It can be used in bioaugmentation studies under varied condition.

  8. Anaerobic digestion of raw and thermally hydrolyzed wastewater solids under various operational conditions.

    PubMed

    Wilson, Christopher A; Tanneru, Charan T; Banjade, Sarita; Murthy, Sudhir N; Novak, John T

    2011-09-01

    In this study, high-solids anaerobic digestion of thermally pretreated wastewater solids (THD) was compared with conventional mesophilic anaerobic digestion (MAD). Operational conditions, such as pretreatment temperature (150 to 170 degrees C), solids retention time (15 to 20 days), and digestion temperature (37 to 42 degrees C), were varied for the seven THD systems operated. Volatile solids reduction (VSR) by THD ranged from 56 to 62%, compared with approximately 50% for MAD. Higher VSR contributed to 24 to 59% increased biogas production (m3/kg VSR-d) from THD relative to MAD. The high-solids conditions of the THD feed resulted in high total ammonia-nitrogen (proportional to solids loading) and total alkalinity concentrations in excess of 14 g/L as calcium carbonate (CaCO3). Increased pH in THD reactors caused 5 to 8 times more un-ionized ammonia to be present than in MAD, and this likely led to inhibition of aceticlastic methanogens, resulting in accumulation of residual volatile fatty acids between 2 and 6 g/L as acetic acid. The THD produced biosolids cake that possessed low organic sulfur-based biosolids odor and dewatered to between 33 and 39% total solids. Dual conditioning with cationic polymer and ferric chloride was shown to be an effective strategy for mitigating dissolved organic nitrogen and UV-quenching compounds in the return stream following centrifugal dewatering of THD biosolids.

  9. Microbial metabolism of pyridine, quinoline, acridine, and their derivatives under aerobic and anaerobic conditions.

    PubMed Central

    Kaiser, J P; Feng, Y; Bollag, J M

    1996-01-01

    Our review of the metabolic pathways of pyridines and aza-arenes showed that biodegradation of heterocyclic aromatic compounds occurs under both aerobic and anaerobic conditions. Depending upon the environmental conditions, different types of bacteria, fungi, and enzymes are involved in the degradation process of these compounds. Our review indicated that different organisms are using different pathways to biotransform a substrate. Our review also showed that the transformation rate of the pyridine derivatives is dependent on the substituents. For example, pyridine carboxylic acids have the highest transformation rate followed by mono-hydroxypyridines, methylpyridines, aminopyridines, and halogenated pyridines. Through the isolation of metabolites, it was possible to demonstrate the mineralization pathway of various heterocyclic aromatic compounds. By using 14C-labeled substrates, it was possible to show that ring fission of a specific heterocyclic compound occurs at a specific position of the ring. Furthermore, many researchers have been able to isolate and characterize the microorganisms or even the enzymes involved in the transformation of these compounds or their derivatives. In studies involving 18O labeling as well as the use of cofactors and coenzymes, it was possible to prove that specific enzymes (e.g., mono- or dioxygenases) are involved in a particular degradation step. By using H2 18O, it could be shown that in certain transformation reactions, the oxygen was derived from water and that therefore these reactions might also occur under anaerobic conditions. PMID:8840783

  10. Uranium Biominerals Precipitated by an Environmental Isolate of Serratia under Anaerobic Conditions

    PubMed Central

    Newsome, Laura; Morris, Katherine; Lloyd, Jonathan. R.

    2015-01-01

    Stimulating the microbially-mediated precipitation of uranium biominerals may be used to treat groundwater contamination at nuclear sites. The majority of studies to date have focussed on the reductive precipitation of uranium as U(IV) by U(VI)- and Fe(III)-reducing bacteria such as Geobacter and Shewanella species, although other mechanisms of uranium removal from solution can occur, including the precipitation of uranyl phosphates via bacterial phosphatase activity. Here we present the results of uranium biomineralisation experiments using an isolate of Serratia obtained from a sediment sample representative of the Sellafield nuclear site, UK. When supplied with glycerol phosphate, this Serratia strain was able to precipitate 1 mM of soluble U(VI) as uranyl phosphate minerals from the autunite group, under anaerobic and fermentative conditions. Under phosphate-limited anaerobic conditions and with glycerol as the electron donor, non-growing Serratia cells could precipitate 0.5 mM of uranium supplied as soluble U(VI), via reduction to nano-crystalline U(IV) uraninite. Some evidence for the reduction of solid phase uranyl(VI) phosphate was also observed. This study highlights the potential for Serratia and related species to play a role in the bioremediation of uranium contamination, via a range of different metabolic pathways, dependent on culturing or in situ conditions. PMID:26132209

  11. Isolation and characterization of a sulfur-oxidizing chemolithotroph growing on crude oil under anaerobic conditions.

    PubMed

    Kodama, Yumiko; Watanabe, Kazuya

    2003-01-01

    Molecular approaches have shown that a group of bacteria (called cluster 1 bacteria) affiliated with the epsilon subclass of the class Proteobacteria constituted major populations in underground crude-oil storage cavities. In order to unveil their physiology and ecological niche, this study isolated bacterial strains (exemplified by strain YK-1) affiliated with the cluster 1 bacteria from an oil storage cavity at Kuji in Iwate, Japan. 16S rRNA gene sequence analysis indicated that its closest relative was Thiomicrospira denitrificans (90% identity). Growth experiments under anaerobic conditions showed that strain YK-1 was a sulfur-oxidizing obligate chemolithotroph utilizing sulfide, elemental sulfur, thiosulfate, and hydrogen as electron donors and nitrate as an electron acceptor. Oxygen also supported its growth only under microaerobic conditions. Strain YK-1 could not grow on nitrite, and nitrite was the final product of nitrate reduction. Neither sugars, organic acids (including acetate), nor hydrocarbons could serve as carbon and energy sources. A typical stoichiometry of its energy metabolism followed an equation: S(2-) + 4NO(3)(-) --> SO(4)(2-) + 4NO(2)(-) (Delta G(0) = -534 kJ mol(-1)). In a difference from other anaerobic sulfur-oxidizing bacteria, this bacterium was sensitive to NaCl; growth in medium containing more than 1% NaCl was negligible. When YK-1 was grown anaerobically in a sulfur-depleted inorganic medium overlaid with crude oil, sulfate was produced, corresponding to its growth. On the contrary, YK-1 could not utilize crude oil as a carbon source. These results suggest that the cluster 1 bacteria yielded energy for growth in oil storage cavities by oxidizing petroleum sulfur compounds. Based on its physiology, ecological interactions with other members of the groundwater community are discussed.

  12. Suppression of Eis and expression of Wag31 and GroES in Mycobacterium tuberculosis cytosol under anaerobic culture conditions.

    PubMed

    Maurya, Vineet K; Singh, Kavita; Sinha, Sudhir

    2014-08-01

    A major impediment in chemotherapy of Tuberculosis (TB) is the persistence of M. tuberculosis in a latent or dormant state, possibly perpetuated by paucity of oxygen within the lung granuloma. Proteome analysis of the anaerobically persisting microbe could therefore provide novel targets for drugs against latent TB infection (LTBI). An Indian clinical isolate of M. tuberculosis was cultured under aerobic and anaerobic conditions following Wayne's hypoxia model and its cytosolic proteins were resolved by two-dimensional gel electrophoresis (2DE). Peptide mass fingerprinting of 32 differentially expressed spots using MALDI TOF-TOF MS-MS resulted in identification of 23 proteins. Under the anaerobic culture conditions, expression of 12 of these proteins was highly suppressed (>2 fold reduction in spot volumes), with 4 of them (GrpE, CanB, MoxR1 and Eis) appearing as completely suppressed since corresponding spots were not detectable in the anaerobic sample. On the other hand, 4 proteins were highly expressed, with two of them (Wag31 and GroES) being uniquely expressed under anaerobic conditions. Suppression of Eis could make the anaerobically persisting bacilli susceptible to the aminoglycoside antibiotics which are known to be acetylated and inactivated by Eis. Although all 4 overexpressed proteins can be considered as putative drug targets for LTBI, Wag31 appears particularly interesting in view of its role in the cell wall biogenesis.

  13. Influence of extreme ambient temperatures and anaerobic conditions on Peltigera aphthosa (L.) Willd. viability

    NASA Astrophysics Data System (ADS)

    Dyakov, M. Yu.; Insarova, I. D.; Kharabadze, D. E.; Ptushenko, V. V.; Shtaer, O. V.

    2015-11-01

    Lichen are symbiotic systems constituted by heterotrophic fungi (mycobionts) and photosynthetic microorganism (photobionts). These organisms can survive under extreme stress conditions. The aim of this work was to study the influence of low (- 70 °C) or high (+ 70 °C) temperatures, temperature fluctuations from + 70 °C to - 70 °C, and anaerobic conditions on P. aphthosa (L.) Willd. viability. None of the studied stress factors affected significantly photosynthetic and respiratory activity of the thalli. No changes in morphology or ultrastructure of the cells were revealed for both photobiont and mycobiont components after extreme temperature treatment of P. aphthosa thalli. The data show the extreme tolerance of P. aphthosa to some stress factors inherent to the space flight conditions.

  14. Quantitative proteome and transcriptome analysis of the archaeon Thermoplasma acidophilum cultured under aerobic and anaerobic conditions.

    PubMed

    Sun, Na; Pan, Cuiping; Nickell, Stephan; Mann, Matthias; Baumeister, Wolfgang; Nagy, István

    2010-09-03

    A comparative proteome and transcriptome analysis of Thermoplasma acidophilum cultured under aerobic and anaerobic conditions has been performed. One-thousand twenty-five proteins were identified covering 88% of the cytosolic proteome. Using a label-free quantitation method, we found that approximately one-quarter of the identified proteome (263 proteins) were significantly induced (>2 fold) under anaerobic conditions. Thirty-nine macromolecular complexes were identified, of which 28 were quantified and 15 were regulated under anaerobiosis. In parallel, a whole genome cDNA microarray analysis was performed showing that the expression levels of 445 genes were influenced by the absence of oxygen. Interestingly, more than 40% of the membrane protein-encoding genes (145 out of 335 ORFs) were up- or down-regulated at the mRNA level. Many of these proteins are functionally associated with extracellular protein or peptide degradation or ion and amino acid transport. Comparison of the transcriptome and proteome showed only a weak positive correlation between mRNA and protein expression changes, which is indicative of extensive post-transcriptional regulatory mechanisms in T. acidophilum. Integration of transcriptomics and proteomics data generated hypotheses for physiological adaptations of the cells to anaerobiosis, and the quantitative proteomics data together with quantitative analysis of protein complexes provide a platform for correlation of MS-based proteomics studies with cryo-electron tomography-based visual proteomics approaches.

  15. Formation of diphenylthioarsinic acid from diphenylarsinic acid under anaerobic sulfate-reducing soil conditions.

    PubMed

    Hisatomi, Shihoko; Guan, Ling; Nakajima, Mami; Fujii, Kunihiko; Nonaka, Masanori; Harada, Naoki

    2013-11-15

    Diphenylarsinic acid (DPAA) is a toxic phenylarsenical compound often found around sites contaminated with phenylarsenic chemical warfare agents, diphenylcyanoarsine or diphenylchloroarsine, which were buried in soil after the World Wars. This research concerns the elucidation of the chemical structure of an arsenic metabolite transformed from DPAA under anaerobic sulfate-reducing soil conditions. In LC/ICP-MS analysis, the retention time of the metabolite was identical to that of a major phenylarsenical compound synthesized by chemical reaction of DPAA and hydrogen sulfide. Moreover the mass spectra for the two compounds measured using LC/TOF-MS were similar. Subsequent high resolution mass spectral analysis indicated that two major ions at m/z 261 and 279, observed on both mass spectra, were attributable to C12H10AsS and C12H12AsSO, respectively. These findings strongly suggest that the latter ion is the molecular-related ion ([M+H](+)) of diphenylthioarsinic acid (DPTA; (C6H5)2AsS(OH)) and the former ion is its dehydrated fragment. Thus, our results reveal that DPAA can be transformed to DPTA, as a major metabolite, under sulfate-reducing soil conditions. Moreover, formation of diphenyldithioarsinic acid and subsequent dimerization were predicted by the chemical reaction analysis of DPAA with hydrogen sulfide. This is the first report to elucidate the occurrence of DPAA-thionation in an anaerobic soil.

  16. Mechanism of xanthine oxidase catalyzed biotransformation of HMX under anaerobic conditions.

    PubMed

    Bhushan, Bharat; Paquet, Louise; Halasz, Annamaria; Spain, Jim C; Hawari, Jalal

    2003-06-27

    Enzyme catalyzed biotransformation of the energetic chemical octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) is not known. The present study describes a xanthine oxidase (XO) catalyzed biotransformation of HMX to provide insight into the biodegradation pathway of this energetic chemical. The rates of biotransformation under aerobic and anaerobic conditions were 1.6+/-0.2 and 10.5+/-0.9 nmolh(-1)mgprotein(-1), respectively, indicating that anaerobic conditions favored the reaction. The biotransformation rate was about 6-fold higher using NADH as an electron-donor compared to xanthine. During the course of reaction, the products obtained were nitrite (NO(2)(-)), methylenedinitramine (MDNA), 4-nitro-2,4-diazabutanal (NDAB), formaldehyde (HCHO), nitrous oxide (N(2)O), formic acid (HCOOH), and ammonium (NH(4)(+)). The product distribution gave carbon and nitrogen mass-balances of 91% and 88%, respectively. A comparative study with native-, deflavo-, and desulfo-XO and the site-specific inhibition studies showed that HMX biotransformation occurred at the FAD-site of XO. Nitrite stoichiometry revealed that an initial single N-denitration step was sufficient for the spontaneous decomposition of HMX.

  17. Determination of operating conditions in an anaerobic acid-phase reactor treating dairy wastewater

    SciTech Connect

    Kasapgil, B.; Ince, O.; Anderson, G.K.

    1996-11-01

    Anaerobic digestion of organic material is a multistep process. Two groups of bacteria, namely acidogenic and methanogenic bacteria, are responsible for the acidification and for the methane formation, respectively. The growth requirements of the two groups of bacteria are rather different. In order to create optimum conditions for the process, it was first proposed to separate the process into two phases. Operating variables applicable for the selection and enrichment of microbial populations in phased digesters include digester loading, hydraulic retention time (HRT), pH, temperature, reactor design, and operating mode. By proper manipulation of these operating parameters it is possible to prevent any significant growth of methane bacteria and at the same time achieve the required level of acidification in the first reactor. Further enrichment of two cultures is possible by biomass recycle around each phase. Since the 1970s, phase separation has been introduced into anaerobic digestion technology. However, data concerning the optimization of operating conditions in both acidogenic and methanogenic phase reactors are scarce. This study was therefore carried out for the purposes given below. These were: (1) to determine the best combination of pH and temperature within the ranges studied for the pre-acidification of dairy wastewater; (2) to determine the maximum acidogenic conversion from COD to VFAs, and (3) to determine the changes in the distribution of major VFAs being produced during the pre-acidification of dairy wastewater.

  18. Breaking The Enzymatic Latch: Do Anaerobic Conditions Constrain Decomposition In Humid Tropical Forest Soil?

    NASA Astrophysics Data System (ADS)

    Hall, S. J.; Silver, W. L.

    2011-12-01

    Anaerobic conditions have been proposed to impose a "latch" on soil organic matter decomposition by inhibiting the activity of extracellular enzymes that catalyze the transformation of organic polymers into monomers for microbial assimilation. Here, we tested the hypothesis that anaerobiosis inhibits soil hydrolytic enzyme activity in a humid tropical forest ecosystem in Puerto Rico. We sampled surface and sub-surface soil from each of 59 plots (n = 118) stratified across distinct topographical zones (ridges, slopes, and valleys) known to vary in soil oxygen (O2) concentrations, and measured the potential activity of five hydrolytic enzymes that decompose carbon (C), nitrogen (N), and phosphorus (P) substrates. We measured reduced iron (Fe (II)) concentrations in soil extractions to provide a spatially and temporally integrated index of anaerobic microbial activity, since iron oxides constitute the dominant anaerobic terminal electron acceptor in this ecosystem. Surprisingly, we observed positive relationships between Fe (II) concentrations and the activity of all enzymes that we assayed. Linear mixed effects models that included Fe (II) concentration, topographic position, and their interaction explained between 30 to 70 % of the variance of enzyme activity of β-1,4-glucosidase, β-cellobiohydrolase, β-xylosidase, N-acetylglucosaminidase, and acid phosphatase. Soils from ridges and slopes contained between 10 and 800 μg Fe (II) g-1 soil, and exhibited consistently positive relationships (p < 0.0001) between Fe (II) and enzyme activity. Valley soils did not display significant relationships between enzyme activity and Fe (II), although they displayed variation in soil Fe (II) concentrations similar to ridges and slopes. Overall, valleys exhibited lower enzyme activity and lower Fe (II) concentrations than ridges or slopes, possibly related to decreased root biomass and soil C. Our data provide no indication that anaerobiosis suppresses soil enzyme activity, but

  19. High-solids anaerobic mono-digestion of riverbank grass under thermophilic conditions.

    PubMed

    Andriamanohiarisoamanana, Fetra J; Matsunami, Nobuyuki; Yamashiro, Takaki; Iwasaki, Masahiro; Ihara, Ikko; Umetsu, Kazutaka

    2017-02-01

    The purpose of this study was to investigate the potential of high-solids anaerobic mono-digestion of riverbank grass under thermophilic conditions, focusing on the effects of the strength and the amount of inoculum. Ensiled grass was inoculated with three different inocula; inoculum from liquid anaerobic digester (LI), inoculum from dry anaerobic digester (DI), and mixture of LI and DI (MI), at feedstock-to-inoculum ratio (FIR) of 1, 2 and 4. The ensiling process of riverbank grass reduced moisture content (p>0.05), while the hemicellulose content was significantly increased from 30.88% to 35.15% (p<0.05), on dry matter basis. The highest methane production was at an FIR of 2 with MI (167L/kg VSadded), which was significantly higher (p<0.05) than with DI, but not significant compared to LI (p>0.05). At an FIR of 4, digesters inoculated with LI and DI failed to produce methane, whereas 135LCH4/kg VSadded was obtained with MI. The kinetic studies showed that at an FIR of 1 with LI and MI, the inoculum had less of effects on the hydrolysis rate constant (0.269day(-1) and 0.245day(-1)) and methane production (135 versus 149L/kg VSadded); rather, it affected the lag phase. In a thermophilic HS-AD of riverbank grass, the mixture of inoculum with low and high total solids content (TS) helps increase the TS of inoculum and digestion process. An FIR of 2 was deducted to be the limit for a better startup time and higher volumetric productivity of methane. Copyright © 2016. Published by Elsevier B.V.

  20. Oxygen Consumption by Anaerobic Saccharomyces cerevisiae under Enological Conditions: Effect on Fermentation Kinetics

    PubMed Central

    Rosenfeld, Eric; Beauvoit, Bertrand; Blondin, Bruno; Salmon, Jean-Michel

    2003-01-01

    The anaerobic growth of the yeast Saccharomyces cerevisiae normally requires the addition of molecular oxygen, which is used to synthesize sterols and unsaturated fatty acids (UFAs). A single oxygen pulse can stimulate enological fermentation, but the biochemical pathways involved in this phenomenon remain to be elucidated. We showed that the addition of oxygen (0.3 to 1.5 mg/g [dry mass] of yeast) to a lipid-depleted medium mainly resulted in the synthesis of the sterols and UFAs required for cell growth. However, the addition of oxygen during the stationary phase in a medium containing excess ergosterol and oleic acid increased the specific fermentation rate, increased cell viability, and shortened the fermentation period. Neither the respiratory chain nor de novo protein synthesis was required for these medium- and long-term effects. As de novo lipid synthesis may be involved in ethanol tolerance, we studied the effect of oxygen addition on sterol and UFA auxotrophs (erg1 and ole1 mutants, respectively). Both mutants exhibited normal anaerobic fermentation kinetics. However, only the ole1 mutant strain responded to the oxygen pulse during the stationary phase, suggesting that de novo sterol synthesis is required for the oxygen-induced increase of the specific fermentation rate. In conclusion, the sterol pathway appears to contribute significantly to the oxygen consumption capacities of cells under anaerobic conditions. Nevertheless, we demonstrated the existence of alternative oxygen consumption pathways that are neither linked to the respiratory chain nor linked to heme, sterol, or UFA synthesis. These pathways dissipate the oxygen added during the stationary phase, without affecting the fermentation kinetics. PMID:12513985

  1. Anaerobic Naphthalene Degradation by Microbial Pure Cultures under Nitrate-Reducing Conditions

    PubMed Central

    Rockne, Karl J.; Chee-Sanford, Joanne C.; Sanford, Robert A.; Hedlund, Brian P.; Staley, James T.; Strand, Stuart E.

    2000-01-01

    Pure bacterial cultures were isolated from a highly enriched denitrifying consortium previously shown to anaerobically biodegrade naphthalene. The isolates were screened for the ability to grow anaerobically in liquid culture with naphthalene as the sole source of carbon and energy in the presence of nitrate. Three naphthalene-degrading pure cultures were obtained, designated NAP-3-1, NAP-3-2, and NAP-4. Isolate NAP-3-1 tested positive for denitrification using a standard denitrification assay. Neither isolate NAP-3-2 nor isolate NAP-4 produced gas in the assay, but both consumed nitrate and NAP-4 produced significant amounts of nitrite. Isolates NAP-4 and NAP-3-1 transformed 70 to 90% of added naphthalene, and the transformation was nitrate dependent. No significant removal of naphthalene occurred under nitrate-limited conditions or in cell-free controls. Both cultures exhibited partial mineralization of naphthalene, representing 7 to 20% of the initial added 14C-labeled naphthalene. After 57 days of incubation, the largest fraction of the radiolabel in both cultures was recovered in the cell mass (30 to 50%), with minor amounts recovered as unknown soluble metabolites. Nitrate consumption, along with the results from the 14C radiolabel study, are consistent with the oxidation of naphthalene coupled to denitrification for NAP-3-1 and nitrate reduction to nitrite for NAP-4. Phylogenetic analyses based on 16S ribosomal DNA sequences of NAP-3-1 showed that it was closely related to Pseudomonas stutzeri and that NAP-4 was closely related to Vibrio pelagius. This is the first report we know of that demonstrates nitrate-dependent anaerobic degradation and mineralization of naphthalene by pure cultures. PMID:10742247

  2. Plutonium Oxidation State Distribution under Aerobic and Anaerobic Subsurface Conditions for Metal-Reducing Bacteria

    NASA Astrophysics Data System (ADS)

    Reed, D. T.; Swanson, J.; Khaing, H.; Deo, R.; Rittmann, B.

    2009-12-01

    The fate and potential mobility of plutonium in the subsurface is receiving increased attention as the DOE looks to cleanup the many legacy nuclear waste sites and associated subsurface contamination. Plutonium is the near-surface contaminant of concern at several DOE sites and continues to be the contaminant of concern for the permanent disposal of nuclear waste. The mobility of plutonium is highly dependent on its redox distribution at its contamination source and along its potential migration pathways. This redox distribution is often controlled, especially in the near-surface where organic/inorganic contaminants often coexist, by the direct and indirect effects of microbial activity. The redox distribution of plutonium in the presence of facultative metal reducing bacteria (specifically Shewanella and Geobacter species) was established in a concurrent experimental and modeling study under aerobic and anaerobic conditions. Pu(VI), although relatively soluble under oxidizing conditions at near-neutral pH, does not persist under a wide range of the oxic and anoxic conditions investigated in microbiologically active systems. Pu(V) complexes, which exhibit high chemical toxicity towards microorganisms, are relatively stable under oxic conditions but are reduced by metal reducing bacteria under anaerobic conditions. These facultative metal-reducing bacteria led to the rapid reduction of higher valent plutonium to form Pu(III/IV) species depending on nature of the starting plutonium species and chelating agents present in solution. Redox cycling of these lower oxidation states is likely a critical step in the formation of pseudo colloids that may lead to long-range subsurface transport. The CCBATCH biogeochemical model is used to explain the redox mechanisms and final speciation of the plutonium oxidation state distributions observed. These results for microbiologically active systems are interpreted in the context of their importance in defining the overall migration

  3. Transposon mutagenesis identified chromosomal and plasmid genes essential for adaptation of the marine bacterium Dinoroseobacter shibae to anaerobic conditions.

    PubMed

    Ebert, Matthias; Laaß, Sebastian; Burghartz, Melanie; Petersen, Jörn; Koßmehl, Sebastian; Wöhlbrand, Lars; Rabus, Ralf; Wittmann, Christoph; Tielen, Petra; Jahn, Dieter

    2013-10-01

    Anaerobic growth and survival are integral parts of the life cycle of many marine bacteria. To identify genes essential for the anoxic life of Dinoroseobacter shibae, a transposon library was screened for strains impaired in anaerobic denitrifying growth. Transposon insertions in 35 chromosomal and 18 plasmid genes were detected. The essential contribution of plasmid genes to anaerobic growth was confirmed with plasmid-cured D. shibae strains. A combined transcriptome and proteome approach identified oxygen tension-regulated genes. Transposon insertion sites of a total of 1,527 mutants without an anaerobic growth phenotype were determined to identify anaerobically induced but not essential genes. A surprisingly small overlap of only three genes (napA, phaA, and the Na(+)/Pi antiporter gene Dshi_0543) between anaerobically essential and induced genes was found. Interestingly, transposon mutations in genes involved in dissimilatory and assimilatory nitrate reduction (napA, nasA) and corresponding cofactor biosynthesis (genomic moaB, moeB, and dsbC and plasmid-carried dsbD and ccmH) were found to cause anaerobic growth defects. In contrast, mutation of anaerobically induced genes encoding proteins required for the later denitrification steps (nirS, nirJ, nosD), dimethyl sulfoxide reduction (dmsA1), and fermentation (pdhB1, arcA, aceE, pta, acs) did not result in decreased anaerobic growth under the conditions tested. Additional essential components (ferredoxin, cccA) of the anaerobic electron transfer chain and central metabolism (pdhB) were identified. Another surprise was the importance of sodium gradient-dependent membrane processes and genomic rearrangements via viruses, transposons, and insertion sequence elements for anaerobic growth. These processes and the observed contributions of cell envelope restructuring (lysM, mipA, fadK), C4-dicarboxylate transport (dctM1, dctM3), and protease functions to anaerobic growth require further investigation to unravel the

  4. Microbial Ecology in Anaerobic Digestion at Agitated and Non-Agitated Conditions

    PubMed Central

    Tian, Zhuoli; Cabrol, Léa; Ruiz-Filippi, Gonzalo; Pullammanappallil, Pratap

    2014-01-01

    To investigate the distribution and dynamics of microbial community in anaerobic digestion at agitated and non-agitated condition, 454 pyrosequencing of 16s rRNA was conducted. It revealed the distinct community compositions between the two digesters and their progressive shifting over time. Methanogens and syntrophic bacteria were found much less abundant in the agitated digester, which was mainly attributed to the presence of bacterial genera Acetanaerobacterium and Ruminococcus with relatively high abundance. The characterization of the microbial community corroborated the digestion performance affected at the agitated condition, where lower methane yield and delayed methane production rate were observed. This was further verified by the accumulation of propionic acid in the agitated digester. PMID:25313520

  5. Detailed observation and measurement of sewer sediment erosion under aerobic and anaerobic conditions.

    PubMed

    Schellart, A; Veldkamp, R; Klootwijk, M; Clemens, F; Tait, S; Ashley, R; Howes, C

    2005-01-01

    A greater understanding of the erosion behaviour of sewer sediments is necessary in order to reliably estimate the amount and nature of the sewer sediments released from deposits in sewers and transported either to waste water treatment plants or discharged into the environment. Research has indicated that microbial activity in sediment can influence the physical release of sediment from in-pipe deposits. This paper reports on a series of erosion tests in which sewer sediments from different sewer networks are kept under different environmental conditions and their resistance to erosion is examined. The erosion tests are carried out under aerobic and anaerobic conditions and two temperatures, one representing ambient sewer temperatures and a lower temperature that significantly suppresses bacterial activity.

  6. Anaerobic digestion of the microalga Spirulina at extreme alkaline conditions: biogas production, metagenome, and metatranscriptome

    PubMed Central

    Nolla-Ardèvol, Vímac; Strous, Marc; Tegetmeyer, Halina E.

    2015-01-01

    A haloalkaline anaerobic microbial community obtained from soda lake sediments was used to inoculate anaerobic reactors for the production of methane rich biogas. The microalga Spirulina was successfully digested by the haloalkaline microbial consortium at alkaline conditions (pH 10, 2.0 M Na+). Continuous biogas production was observed and the obtained biogas was rich in methane, up to 96%. Alkaline medium acted as a CO2 scrubber which resulted in low amounts of CO2 and no traces of H2S in the produced biogas. A hydraulic retention time (HRT) of 15 days and 0.25 g Spirulina L−1 day−1 organic loading rate (OLR) were identified as the optimal operational parameters. Metagenomic and metatranscriptomic analysis showed that the hydrolysis of the supplied substrate was mainly carried out by Bacteroidetes of the “ML635J-40 aquatic group” while the hydrogenotrophic pathway was the main producer of methane in a methanogenic community dominated by Methanocalculus. PMID:26157422

  7. Reductive dechlorination of methoxychlor and DDT by human intestinal bacterium Eubacterium limosum under anaerobic conditions.

    PubMed

    Yim, You-Jin; Seo, Jiyoung; Kang, Su-Il; Ahn, Joong-Hoon; Hur, Hor-Gil

    2008-04-01

    Methoxychlor [1,1,1-trichloro-2,2-bis(p-methoxyphenyl)ethane], a substitute for 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), is a compound of environmental concern because of potential long-term health risks related to its endocrine-disrupting and carcinogenic potency. In order to determine the metabolic fate of methoxychlor and DDT in the human intestinal gut, Eubacterium limosum (ATCC 8486), a strict anaerobe isolated from the human intestine that is capable of O-demethylation toward O-methylated isoflavones, was used as a model intestinal microbial organism. Under anaerobic incubation conditions, E. limosum completely transformed methoxychlor and DDT in 16 days. Based on gas chromatography-mass chromatography analyses, the metabolites produced from methoxychlor and DDT by E. limosum were confirmed to be 1,1-dichloro-2,2-bis(p-methoxyphenyl)ethane (methoxydichlor) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD), respectively. This study suggests that E. limosum in the human intestinal gut might be a participant in the reductive dechlorination of methoxychlor to the more antiandrogenic active methoxydichlor.

  8. Study of the operational conditions for anaerobic digestion of urban solid wastes

    SciTech Connect

    Castillo M, Edgar Fernando . E-mail: efcastil@uis.edu.co; Cristancho, Diego Edison; Victor Arellano, A.

    2006-07-01

    This paper describes an experimental evaluation of anaerobic digestion technology as an option for the management of organic solid waste in developing countries. As raw material, a real and heterogeneous organic waste from urban solid wastes was used. In the first experimental phase, seed selection was achieved through an evaluation of three different anaerobic sludges coming from wastewater treatment plants. The methanization potential of these sludges was assessed in three different batch digesters of 500 mL, at two temperature levels. The results showed that by increasing the temperature to 15 deg. C above room temperature, the methane production increases to three times. So, the best results were obtained in the digester fed with a mixed sludge, working at mesophilic conditions (38-40 deg. C). Then, this selected seed was used at the next experimental phase, testing at different digestion times (DT) of 25, 20 and 18 days in a bigger batch digester of 20 L with a reaction volume of 13 L. The conversion rates were registered at the lowest DT (18 days), reaching 44.9 L/kg{sup -1} of wet waste day{sup -1}. Moreover, DT also has a strong influence over COD removal, because there is a direct relationship between solids removal inside the reactor and DT.

  9. Study of the operational conditions for anaerobic digestion of urban solid wastes.

    PubMed

    M, Edgar Fernando Castillo; Cristancho, Diego Edison; Arellano, A Victor

    2006-01-01

    This paper describes an experimental evaluation of anaerobic digestion technology as an option for the management of organic solid waste in developing countries. As raw material, a real and heterogeneous organic waste from urban solid wastes was used. In the first experimental phase, seed selection was achieved through an evaluation of three different anaerobic sludges coming from wastewater treatment plants. The methanization potential of these sludges was assessed in three different batch digesters of 500 mL, at two temperature levels. The results showed that by increasing the temperature to 15 degrees C above room temperature, the methane production increases to three times. So, the best results were obtained in the digester fed with a mixed sludge, working at mesophilic conditions (38-40 degrees C). Then, this selected seed was used at the next experimental phase, testing at different digestion times (DT) of 25, 20 and 18 days in a bigger batch digester of 20 L with a reaction volume of 13 L. The conversion rates were registered at the lowest DT (18 days), reaching 44.9 L/kg(-1) of wet wasteday(-1). Moreover, DT also has a strong influence over COD removal, because there is a direct relationship between solids removal inside the reactor and DT.

  10. Increased bactericidal activity of colistin on Pseudomonas aeruginosa biofilms in anaerobic conditions.

    PubMed

    Kolpen, Mette; Appeldorff, Cecilie F; Brandt, Sarah; Mousavi, Nabi; Kragh, Kasper N; Aydogan, Sevtap; Uppal, Haleema A; Bjarnsholt, Thomas; Ciofu, Oana; Høiby, Niels; Jensen, Peter Ø

    2016-02-01

    Tolerance towards antibiotics of Pseudomonas aeruginosa biofilms is recognized as a major cause of therapeutic failure of chronic lung infection in cystic fibrosis (CF) patients. This lung infection is characterized by antibiotic-tolerant biofilms in mucus with zones of O2 depletion mainly due to polymorphonuclear leukocytic activity. In contrast to the main types of bactericidal antibiotics, it has not been possible to establish an association between the bactericidal effects of colistin and the production of detectable levels of OH ˙ on several strains of planktonic P. aeruginosa. Therefore, we propose that production of OH ˙ may not contribute significantly to the bactericidal activity of colistin on P. aeruginosa biofilm. Thus, we investigated the effect of colistin treatment on biofilm of wild-type PAO1, a catalase-deficient mutant (ΔkatA) and a colistin-resistant CF isolate cultured in microtiter plates in normoxic- or anoxic atmosphere with 1 mM nitrate. The killing of bacteria during colistin treatment was measured by CFU counts, and the OH⋅ formation was measured by 3(')-(p-hydroxylphenyl fluorescein) fluorescein (HPF) fluorescence. Validation of the assay was done by hydrogen peroxide treatment. OH⋅ formation was undetectable in aerobic PAO1 biofilms during 3 h of colistin treatment. Interestingly, we demonstrate increased susceptibility of P. aeruginosa biofilms towards colistin during anaerobic conditions. In fact, the maximum enhancement of killing by anaerobic conditions exceeded 2 logs using 4 mg L(-1) of colistin compared to killing at aerobic conditions. © FEMS 2015.

  11. Increased bactericidal activity of colistin on Pseudomonas aeruginosa biofilms in anaerobic conditions

    PubMed Central

    Kolpen, Mette; Appeldorff, Cecilie F.; Brandt, Sarah; Mousavi, Nabi; Kragh, Kasper N.; Aydogan, Sevtap; Uppal, Haleema A.; Bjarnsholt, Thomas; Ciofu, Oana; Høiby, Niels; Jensen, Peter Ø.

    2015-01-01

    Tolerance towards antibiotics of Pseudomonas aeruginosa biofilms is recognized as a major cause of therapeutic failure of chronic lung infection in cystic fibrosis (CF) patients. This lung infection is characterized by antibiotic-tolerant biofilms in mucus with zones of O2 depletion mainly due to polymorphonuclear leukocytic activity. In contrast to the main types of bactericidal antibiotics, it has not been possible to establish an association between the bactericidal effects of colistin and the production of detectable levels of OH ˙ on several strains of planktonic P. aeruginosa. Therefore, we propose that production of OH ˙ may not contribute significantly to the bactericidal activity of colistin on P. aeruginosa biofilm. Thus, we investigated the effect of colistin treatment on biofilm of wild-type PAO1, a catalase-deficient mutant (ΔkatA) and a colistin-resistant CF isolate cultured in microtiter plates in normoxic- or anoxic atmosphere with 1 mM nitrate. The killing of bacteria during colistin treatment was measured by CFU counts, and the OH⋅ formation was measured by 3′-(p-hydroxylphenyl fluorescein) fluorescein (HPF) fluorescence. Validation of the assay was done by hydrogen peroxide treatment. OH⋅ formation was undetectable in aerobic PAO1 biofilms during 3 h of colistin treatment. Interestingly, we demonstrate increased susceptibility of P. aeruginosa biofilms towards colistin during anaerobic conditions. In fact, the maximum enhancement of killing by anaerobic conditions exceeded 2 logs using 4 mg L−1 of colistin compared to killing at aerobic conditions. PMID:26458402

  12. Continuous high-solids anaerobic co-digestion of organic solid wastes under mesophilic conditions

    SciTech Connect

    Kim, Dong-Hoon; Oh, Sae-Eun

    2011-09-15

    Highlights: > High-solids (dry) anaerobic digestion is attracting a lot of attention these days. > One reactor was fed with food waste (FW) and paper waste. > Maximum biogas production rate of 5.0 m{sup 3}/m{sup 3}/d was achieved at HRT 40 d and 40% TS. > The other reactor was fed with FW and livestock waste (LW). > Until a 40% LW content increase, the reactor exhibited a stable performance. - Abstract: With increasing concerns over the limited capacity of landfills, conservation of resources, and reduction of CO{sub 2} emissions, high-solids (dry) anaerobic digestion of organic solid waste (OSW) is attracting a great deal of attention these days. In the present work, two dry anaerobic co-digestion systems fed with different mixtures of OSW were continuously operated under mesophilic conditions. Dewatered sludge cake was used as a main seeding source. In reactor (I), which was fed with food waste (FW) and paper waste (PW), hydraulic retention time (HRT) and solid content were controlled to find the maximum treatability. At a fixed solid content of 30% total solids (TS), stable performance was maintained up to an HRT decrease to 40 d. However, the stable performance was not sustained at 30 d HRT, and hence, HRT was increased to 40 d again. In further operation, instead of decreasing HRT, solid content was increased to 40% TS, which was found to be a better option to increase the treatability. The biogas production rate (BPR), CH{sub 4} production yield (MPY) and VS reduction achieved in this condition were 5.0 m{sup 3}/m{sup 3}/d, 0.25 m{sup 3} CH{sub 4}/g COD{sub added}, and 80%, respectively. Reactor (II) was fed with FW and livestock waste (LW), and LW content was increased during the operation. Until a 40% LW content increase, reactor (II) exhibited a stable performance. A BPR of 1.7 m{sup 3}/m{sup 3}/d, MPY of 0.26 m{sup 3} CH{sub 4}/g COD{sub added}, and VS reduction of 72% was achieved at 40% LW content. However, when the LW content was increased to 60

  13. Continuous high-solids anaerobic co-digestion of organic solid wastes under mesophilic conditions.

    PubMed

    Kim, Dong-Hoon; Oh, Sae-Eun

    2011-01-01

    With increasing concerns over the limited capacity of landfills, conservation of resources, and reduction of CO(2) emissions, high-solids (dry) anaerobic digestion of organic solid waste (OSW) is attracting a great deal of attention these days. In the present work, two dry anaerobic co-digestion systems fed with different mixtures of OSW were continuously operated under mesophilic conditions. Dewatered sludge cake was used as a main seeding source. In reactor (I), which was fed with food waste (FW) and paper waste (PW), hydraulic retention time (HRT) and solid content were controlled to find the maximum treatability. At a fixed solid content of 30% total solids (TS), stable performance was maintained up to an HRT decrease to 40 d. However, the stable performance was not sustained at 30 d HRT, and hence, HRT was increased to 40 d again. In further operation, instead of decreasing HRT, solid content was increased to 40% TS, which was found to be a better option to increase the treatability. The biogas production rate (BPR), CH(4) production yield (MPY) and VS reduction achieved in this condition were 5.0m(3)/m(3)/d, 0.25 m(3) CH(4)/g COD(added), and 80%, respectively. Reactor (II) was fed with FW and livestock waste (LW), and LW content was increased during the operation. Until a 40% LW content increase, reactor (II) exhibited a stable performance. A BPR of 1.7 m(3)/m(3)/d, MPY of 0.26 m(3) CH(4)/g COD(added), and VS reduction of 72% was achieved at 40% LW content. However, when the LW content was increased to 60%, there was a significant performance drop, which was attributed to free ammonia inhibition. The performances in these two reactors were comparable to the ones achieved in the conventional wet digestion and thermophilic dry digestion processes. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. Molecular Dynamics Simulation and Analysis of Interfacial Water at Selected Sulfide Mineral Surfaces under Anaerobic Conditions

    SciTech Connect

    Jin, Jiaqi; Miller, Jan D.; Dang, Liem X.

    2014-04-10

    In this paper, we report on a molecular dynamics simulation (MDS) study of the behavior of interfacial water at selected sulfide mineral surfaces under anaerobic conditions. The study revealed the interfacial water structure and wetting characteristics of the pyrite (100) surface, galena (100) surface, chalcopyrite (012) surface, sphalerite (110) surface, and molybdenite surfaces (i.e., the face, armchair-edge, and zigzag-edge surfaces), including simulated contact angles, relative number density profiles, water dipole orientations, hydrogen-bonding, and residence times. For force fields of the metal and sulfur atoms in selected sulfide minerals used in the MDS, we used the universal force field (UFF) and another set of force fields optimized by quantum chemical calculations for interactions with interfacial water molecules at selected sulfide mineral surfaces. Simulation results for the structural and dynamic properties of interfacial water molecules indicate the natural hydrophobic character for the selected sulfide mineral surfaces under anaerobic conditions as well as the relatively weak hydrophobicity for the sphalerite (110) surface and two molybdenite edge surfaces. Part of the financial support for this study was provided by the U.S. Department of Energy (DOE) under Basic Science Grant No. DE-FG-03-93ER14315. The Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences (BES), of the DOE, funded work performed by Liem X. Dang. Battelle operates Pacific Northwest National Laboratory for DOE. The calculations were carried out using computer resources provided by BES. The authors are grateful to Professor Tsun-Mei Chang for valuable discussions.

  15. pH-Dependent Uptake of Fumaric Acid in Saccharomyces cerevisiae under Anaerobic Conditions

    PubMed Central

    Jamalzadeh, Elaheh; Verheijen, Peter J. T.; Heijnen, Joseph J.

    2012-01-01

    Microbial production of C4 dicarboxylic acids from renewable resources has gained renewed interest. The yeast Saccharomyces cerevisiae is known as a robust microorganism and is able to grow at low pH, which makes it a suitable candidate for biological production of organic acids. However, a successful metabolic engineering approach for overproduction of organic acids requires an incorporation of a proper exporter to increase the productivity. Moreover, low-pH fermentations, which are desirable for facilitating the downstream processing, may cause back diffusion of the undissociated acid into the cells with simultaneous active export, thereby creating an ATP-dissipating futile cycle. In this work, we have studied the uptake of fumaric acid in S. cerevisiae in carbon-limited chemostat cultures under anaerobic conditions. The effect of the presence of fumaric acid at different pH values (3 to 5) has been investigated in order to obtain more knowledge about possible uptake mechanisms. The experimental results showed that at a cultivation pH of 5.0 and an external fumaric acid concentration of approximately 0.8 mmol · liter−1, the fumaric acid uptake rate was unexpectedly high and could not be explained by diffusion of the undissociated form across the plasma membrane alone. This could indicate the presence of protein-mediated import. At decreasing pH levels, the fumaric acid uptake rate was found to increase asymptotically to a maximum level. Although this observation is in accordance with protein-mediated import, the presence of a metabolic bottleneck for fumaric acid conversion under anaerobic conditions could not be excluded. PMID:22113915

  16. Antibacterial Action of Nitric Oxide-Releasing Chitosan Oligosaccharides against Pseudomonas aeruginosa under Aerobic and Anaerobic Conditions

    PubMed Central

    Reighard, Katelyn P.

    2015-01-01

    Chitosan oligosaccharides were modified with N-diazeniumdiolates to yield biocompatible nitric oxide (NO) donor scaffolds. The minimum bactericidal concentrations and MICs of the NO donors against Pseudomonas aeruginosa were compared under aerobic and anaerobic conditions. Differential antibacterial activities were primarily the result of NO scavenging by oxygen under aerobic environments and not changes in bacterial physiology. Bacterial killing was also tested against nonmucoid and mucoid biofilms and compared to that of tobramycin. Smaller NO payloads were required to eradicate P. aeruginosa biofilms under anaerobic versus aerobic conditions. Under oxygen-free environments, the NO treatment was 10-fold more effective at killing biofilms than tobramycin. These results demonstrate the potential utility of NO-releasing chitosan oligosaccharides under both aerobic and anaerobic environments. PMID:26239983

  17. Dynamics of brominated flame retardants removal in contaminated wastewater sewage sludge under anaerobic conditions.

    PubMed

    Stiborova, Hana; Vrkoslavova, Jana; Pulkrabova, Jana; Poustka, Jan; Hajslova, Jana; Demnerova, Katerina

    2015-11-15

    Disposal of solid waste to landfills from waste water sewage treatment plants (WWTPs) serves as a potential source of contamination by polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD). Native microbial communities have been found to degrade a variety of xenobiotics, such as PBDEs and HBCDs. This study investigates the potential of autochthonous microflora to remove 11 PBDE congeners and HBCDs in waste water sludge under anaerobic conditions. Laboratory microcosms were constructed with sewage sludge from the WWTPs of Hradec Kralove and Brno. BDE 209 was detected as the prevailing congener in concentrations 685 and 1403 ng/g dw and the total amounts of 10 lower PBDEs (BDE 28, 47, 49, 66, 85, 99, 100, 153, 154, 183) were 605 and 205 ng/g dw in sludge from Hradec Kralove and Brno, respectively. The levels of HBCD were detected in both sludge lower than 24 ng/g dw. The experiment was carried out for 15 months. After three months of incubation, HBCD was completely degraded to below detection limits. In sewage from both WWTPs, the higher brominated DEs were removed faster than the lower brominated congeners. One exception was tri-BDE, which was degraded completely within 15 months of cultivation. A significant increase in congener tetra-BDE 49 concentrations was observed over the course of the experiment in all tested sewage. The relative distribution of individual congeners among all PBDEs changed after 15 months of the incubation in favour of lower brominated congeners. This indicates that debromination is the major mechanism of anaerobic biodegradation. Despite of the increase of BDE 49, the overall removal of all 11 PBDEs achieved the levels of 47.4 and 68.7% in samples from WWTPs Hradec Kralove and Brno, respectively.

  18. Reductive Disslocation of Pu(IV) by Clostridium sp. Under Anaerobic Conditions

    SciTech Connect

    Francis,A.; Dodge, C.; Gillow, J.

    2008-01-01

    An anaerobic, gram positive, spore-forming bacterium Clostridium sp., common in soils and wastes, capable of reduction of Fe(III) to Fe(II), Mn(IV) to Mn(II), Tc(VII) to Tc(IV), and U(VI) to U(IV), reduced Pu(IV) to Pu(III). Addition of 242Pu (IV)-nitrate to the bacterial growth medium at pH 6.4 resulted in the precipitation of Pu as amorphous Pu(OH)4 due to hydrolysis and polymerization reactions. The Pu (1 x 10-5 M) had no effect upon growth of the bacterium as evidenced by glucose consumption; carbon dioxide and hydrogen production; a decrease in pH of the medium from 6.4 to 3.0 due to production of acetic and butyric acids from glucose fermentation; and a change in the Eh of the culture medium from +50 to -180 mV. Commensurate with bacterial growth, Pu was rapidly solubilized as evidenced by an increase in Pu concentration in solution which passed through a 0.03 {mu}m filtration. Selective solvent extraction of the culture by thenoyltrifluoroacetone (TTA) indicated the presence of a reduced Pu species in the soluble fraction. X-ray absorption near edge spectroscopic (XANES) analysis of Pu in the culture sample at the Pu LIII absorption edge (18.054 keV) showed a shift of -3 eV compared to a Pu(IV) standard indicating reduction of Pu(IV) to Pu(III). These results suggest that, although Pu generally exists as insoluble Pu(IV) in the environment, under appropriate conditions, anaerobic microbial activity could affect the long-term stability and mobility of Pu by its reductive dissolution.

  19. Chemical Changes during Anaerobic Decomposition of Hardwood, Softwood, and Old Newsprint under Mesophilic and Thermophilic Conditions

    Treesearch

    Florentino B. De la Cruz; Daniel J. Yelle; Hanna S. Gracz; Morton A. Barlaz

    2014-01-01

    The anaerobic decomposition of plant biomass is an important aspect of global organic carbon cycling. While the anaerobic metabolism of cellulose and hemicelluloses to methane and carbon dioxide are well-understood, evidence for the initial stages of lignin decomposition is fragmentary. The objective of this study was to look for evidence of chemical transformations of...

  20. Experimental evidence for growth advantage and metabolic shift stimulated by photophosphorylation of proteorhodopsin expressed in Escherichia coli at anaerobic condition.

    PubMed

    Wang, Ying; Li, Yan; Xu, Tuan; Shi, Zhenyu; Wu, Qiong

    2015-05-01

    Since solar light energy is the source of all renewable biological energy, the direct usage of light energy by bacterial cell factory has been a very attractive concept, especially using light energy to promote anaerobic fermentation growth and even recycle low-energy carbon source when energy is the limiting factor. Proteorhodopsin(PR), a light-driven proton pump proven to couple with ATP synthesis when expressed heterogeneously, is an interesting and simple option to enable light usage in engineered strains. However, although it was reported to influence fermentation in some cases, heterogeneous proteorhodopsin expression was never shown to support growth advantage or cause metabolic shift by photophosphorylation so far. Hereby, we presented the first experimental evidence that heterogeneously expressed proteorhodopsin can provide growth advantage and cause ATP-dependent metabolism shift of acetate and lactate changes in Escherichia coli at anaerobic condition. Those discoveries suggest further application potential of PR in anaerobic fermentation where energy is a limiting factor.

  1. Anaerobic power in road cyclists is improved after 10 weeks of whole-body vibration training.

    PubMed

    Oosthuyse, Tanja; Viedge, Alison; McVeigh, Joanne; Avidon, Ingrid

    2013-02-01

    Whole-body vibration (WBV) training has previously improved muscle power in various athletic groups requiring explosive muscle contractions. To evaluate the benefit of including WBV as a training adjunct for improving aerobic and anaerobic cycling performance, road cyclists (n = 9) performed 3 weekly, 10-minute sessions of intermittent WBV on synchronous vertical plates (30 Hz) while standing in a static posture. A control group of cyclists (n = 8) received no WBV training. Before and after the 10-week intervention period, lean body mass (LBM), cycling aerobic peak power (Wmax), 4 mM lactate concentration (OBLA), VO2peak, and Wingate anaerobic peak and mean power output were determined. The WBV group successfully completed all WBV sessions but reported a significant 30% decrease in the weekly cycling training time (pre: 9.4 ± 3.3 h·wk(-1); post: 6.7 ± 3.7 h·wk(-1); p = 0.01) that resulted in a 6% decrease in VO2peak and a 4% decrease in OBLA. The control group reported a nonsignificant 6% decrease in cycling training volume (pre: 9.5 ± 3.6 h·wk(-1); 8.6 ± 2.9 h·wk(-1); p = 0.13), and all measured variables were maintained. Despite the evidence of detraining in the WBV group, Wmax was maintained (pre: 258 ± 53 W; post: 254 ± 57 W; p = 0.43). Furthermore, Wingate peak power increased by 6% (668 ± 189 to 708 ± 220 W; p = 0.055), and Wingate mean power increased by 2% (553 ± 157 to 565 ± 157 W; p = 0.006) in the WBV group from preintervention to postintervention, respectively, without any change to LBM. The WBV training is an attractive training supplement for improving anaerobic power without increasing muscle mass in road cyclists.

  2. Surfactants in anaerobic digestion of cheese whey, poultry waste, and cattle dung for improved biomethanation

    SciTech Connect

    Desai, M.; Madamwar, D.

    1994-05-01

    To obtain enriched methane content and improve the anaerobic digestion of a mixture of cattle dung, poultry waste and cheese whey, with enriched methane content, the effect of various surfactants was studied. Among the surfactants tested, Tween 80 and sodium lauryl sulphate showed the maximum enhancement in gas production as well as methane content, indicating better process performance. The Tween 80 dosed digester (300 {mu}L/L) produced about 3.5 L gas/L of digester/d with 70% methane. Results also indicated increased percent COD reduction in the presence of Tween 80. 13 refs., 2 figs.

  3. Changes in microbial community structures due to varying operational conditions in the anaerobic digestion of oxytetracycline-medicated cow manure.

    PubMed

    Turker, Gokhan; Aydin, Sevcan; Akyol, Çağrı; Yenigun, Orhan; Ince, Orhan; Ince, Bahar

    2016-07-01

    Management of manure containing veterinary antibiotics is a major concern in anaerobic treatment systems because of their possible adverse effects on microbial communities. Therefore, the aim of study was to investigate how oxytetracycline (OTC) influences bacteria and acetoclastic and hydrogenotrophic methanogens under varying operational conditions in OTC-medicated and non-medicated anaerobic cow manure digesters. Concentrations of OTC and its metabolites throughout the anaerobic digestion were determined using ultraviolet-high-performance liquid chromatography (UV-HPLC) and tandem liquid chromatography-mass spectrometry (LC/MS/MS), respectively. Fluorescent in situ hybridization, denaturing gradient gel electrophoresis, cloning, and sequencing analyses were used to monitor changes in microbial community structures. According to the results of analytical and molecular approaches, operating conditions highly influence active microbial community dynamics and associate with biogas production and elimination of OTC and its metabolites during anaerobic digestion of cow manure in the presence of an average initial concentration of 2.2 mg OTC/L. The impact of operating conditions has a drastic effect on acetoclastic methanogens than hydrogenotrophic methanogens and bacteria.

  4. Anaerobic aquifer transformations of 2,4-Dinitrophenol under different terminal electron accepting conditions

    USGS Publications Warehouse

    Krumholz, L.R.; Suflita, J.M.

    1997-01-01

    We evaluated the susceptibility of 2,4-dinitrophenol (2,4-DNP) and 2,4-diaminophenol to anaerobic biodegradation in aquifer slurries. Aquifer microorganisms depleted 2,4-DNP at rates of 25, 9 and 0.4 μM/day under methanogenic, sulfate-reducing and nitrate-reducing conditions, respectively. Rates of abiotic, 2,4-DNP loss in autoclaved control incubations were 7.2, 6.2 and 0.95 μM/day respectively. Abiotic, 2,4-DNP reduction was especially important as the first step in its transformation. 2-Amino-4-nitrophenol was produced by this process, but this compound was further metabolized in methanogenic and sulfate-reducing aquifer slurries. This partially reduced compound persisted in autoclaved controls and in the nitrate-reducing aquifer slurries. Aquifer slurries incubated with either 2,4-DNP or 2,4-diaminophenol produced methane when incubated with no other electron acceptor suggesting that mineralization had occurred under these conditions. In parallel experiments, aquifer slurries amended with 2,6-dinitrophenol or picric acid did not produce methane at levels above the substrate unamended controls.

  5. Anaerobic biodegradation of soybean biodiesel and diesel blends under methanogenic conditions.

    PubMed

    Wu, Shuyun; Yassine, Mohamad H; Suidan, Makram T; Venosa, Albert D

    2015-12-15

    Biotransformation of soybean biodiesel and the inhibitory effect of petrodiesel were studied under methanogenic conditions. Biodiesel removal efficiency of more than 95% was achieved in a chemostat with influent biodiesel concentrations up to 2.45 g/L. The kinetics of anaerobic biodegradation of soybean biodiesel B100 (biodiesel only) with different petrodiesel loads was studied using biomass pre-acclimated to B100 and B80 (80% biodiesel and 20% petrodiesel). The results indicated that the biodiesel fraction of the blend could be effectively biodegraded, whereas petrodiesel was not biodegraded at all under methanogenic conditions. The presence of petrodiesel in blends with biodiesel had a greater inhibitory effect on the rate of biodegradation than the biodegradation efficiency (defined as the efficiency of methane production). Both the biodegradation rate coefficient and the methane production efficiency increased almost linearly with the increasing fraction of biodiesel. With the increasing fraction of petrodiesel, the biodegradation rate and efficiency were correlated with the concentration of soluble FAMEs in the water.

  6. Biofilm formation, phenotypic production of cellulose and gene expression in Salmonella enterica decrease under anaerobic conditions.

    PubMed

    Lamas, A; Miranda, J M; Vázquez, B; Cepeda, A; Franco, C M

    2016-12-05

    Salmonella enterica subsp. enterica is one of the main food-borne pathogens. This microorganism combines an aerobic life outside the host with an anaerobic life within the host. One of the main concerns related to S. enterica is biofilm formation and cellulose production. In this study, biofilm formation, morphotype, cellulose production and transcription of biofilm and quorum sensing-related genes of 11 S. enterica strains were tested under three different conditions: aerobiosis, microaerobiosis, and anaerobiosis. The results showed an influence of oxygen levels on biofilm production. Biofilm formation was significantly higher (P<0.05) in aerobiosis than in microaerobiosis and anaerobiosis. Cellulose production and RDAR (red, dry, and rough) were expressed only in aerobiosis. In microaerobiosis, the strains expressed the SAW (smooth and white) morphotype, while in anaerobiosis the colonies appeared small and red. The expression of genes involved in cellulose synthesis (csgD and adrA) and quorum sensing (sdiA and luxS) was reduced in microaerobiosis and anaerobiosis in all S. enterica strains tested. This gene expression levels were less reduced in S. Typhimurium and S. Enteritidis compared to the tested serotypes. There was a relationship between the expression of biofilm and quorum sensing-related genes. Thus, the results from this study indicate that biofilm formation and cellulose production are highly influenced by atmospheric conditions. This must be taken into account as contamination with these bacteria can occur during food processing under vacuum or modified atmospheres.

  7. Anaerobic degradation of toluene and xylene by aquifer microorganisms under sulfate-reducing conditions.

    PubMed Central

    Edwards, E A; Wills, L E; Reinhard, M; Grbić-Galić, D

    1992-01-01

    Toluene and the three isomers of xylene were completely mineralized to CO2 and biomass by aquifer-derived microorganisms under strictly anaerobic conditions. The source of the inoculum was gasoline-contaminated sediment from Seal Beach, Calif. Evidence confirming that sulfate was the terminal electron acceptor is presented. Benzene and ethylbenzene were not degraded under the experimental conditions used. Successive transfers of the mixed cultures that were enriched from aquifer sediments retained the ability to degrade toluene and xylenes. Greater than 90% of 14C-labeled toluene or 14C-labeled o-xylene was mineralized to 14CO2. The doubling time for the culture grown on toluene or m-xylene was about 20 days, and the cell yield was about 0.1 to 0.14 g of cells (dry weight) per g of substrate. The accumulation of sulfide in the cultures as a result of sulfate reduction appeared to inhibit degradation of aromatic hydrocarbons. PMID:1575482

  8. Dissolution and Mobilization of Uranium in a Reduced Sediment by Natural Humic Substances under Anaerobic Conditions

    SciTech Connect

    Gu, Baohua; Luo, Wensui

    2009-01-01

    Biological reduction and precipitation of uranium (U) has been proposed as a remedial option for immobilizing uranium at contaminated sites, but the long-term stability and mobility of uranium remain a concern because it is neither removed nor destroyed. In this study, the dissolution and mobilization of reduced and oxidized forms of uranium [U(IV) and U(VI)] by natural humic substances were investigated in batch and column flow systems using a bioreduced sediment containing both U(IV) and U(VI). The addition of humic substances significantly increased the dissolution of U(IV) under anaerobic conditions. Humic acid (HA) was found to be more effective than fulvic acid (FA) in dissolving U(IV) in either 1 mM KCl or KHCO3 background solution. However, more U(VI) was dissolved in 1 mM KHCO3 than in 1 mM KCl background electrolytes. The HA also was found to be more effective than FA in mobilizing uranium under reducing and column flow conditions, although an accumulative amount of eluted U(VI) and U(IV) was relatively low (<60 g) after leaching with ~97 pore volumes of the humic solution in 1 mM KHCO3. These observations suggest that natural humic substances could potentially influence the long-term stability of bioreduced U(IV) even under strong reducing environments.

  9. Anaerobic co-digestion of sewage sludge and strawberry extrudate under mesophilic conditions.

    PubMed

    Serrano, Antonio; Siles, José A; Chica, Arturo F; Martín, M Ángeles

    2014-01-01

    The biomethanization of sewage sludge has several disadvantages such as low methane yield, poor biodegradability and nutrient imbalance. In this paper, a sewage sludge and strawberry extrudate mixture in a proportion of 40:60 (wet weight) is proposed to improve the viability of the process. The addition of an easily biodegradable co-substrate enhanced the nutrient balance and diluted the heavy metals and inhibitors from sewage sludge. Two different experimental set-ups at lab and semi-pilot scale were employed in order to ensure the reproducibility and significance of the obtained values. Co-digestion improved the stability of the process by decreasing the alkalinity to a mean value of 3215 ± 190 mg CaCO₃/L, while maintaining the pH within the optimal range for anaerobic digestion. The methane yield coefficient and biodegradability were 176 L/kg VS (total volatile solids) (0°C, 1 atm) and 81% (VS), respectively. Kinetic parameters decreased at the highest loads, suggesting the occurrence of a slowing down phenomenon. A quality organic amendment with a heavy metal content lower than the limits established under European legislation for agricultural applications was obtained from the digestate of the proposed treatment.

  10. 6:2 and 8:2 fluorotelomer alcohol anaerobic biotransformation in digester sludge from a WWTP under methanogenic conditions.

    PubMed

    Zhang, Shu; Szostek, Bogdan; McCausland, Patricia K; Wolstenholme, Barry W; Lu, Xiaoxia; Wang, Ning; Buck, Robert C

    2013-05-07

    6:2 FTOH and 8:2 FTOH [FTOHs, F(CF2)nCH2CH2OH, n = 6, 8] are the principal polyfluorinated raw materials used to manufacture FTOH-based products, which may be released to WWTPs during their product life cycle. For the first time, anaerobic biotransformation of FTOHs and key biotransformation intermediates in WWTP digester sludge under methanogenic conditions was investigated. 6:2 FTOH was transformed to 6:2 FTCA, [F(CF2)6CH2COOH, 32-43 mol %], 6:2 FTUCA [F(CF2)5CF═CHCOOH, 1.8-8.0 mol %], and 5:3 acid [F(CF2)5CH2CH2COOH, 18-23 mol %] by day 90 and day 176 in two separate studies. 8:2 FTOH was transformed by day 181 to 8:2 FTCA (18 mol %), 8:2 FTUCA (5.1 mol %), and 7:3 acid (27 mol %). 6:2 and 8:2 FTOH anaerobic biotransformation led to low levels of perfluorohexanoic acid (PFHxA, ≤0.4 mol %) and perfluorooctanoic acid (PFOA, 0.3 mol %), respectively. 6:2 FTUCA anaerobic biotransformation led to a newly identified novel transient intermediate 3-fluoro 5:3 acid [F(CF2)5CFHCH2COOH] and 5:3 acid, but not 5:2 sFTOH [F(CF2)5CH(OH)CH3] and α-OH 5:3 acid [F(CF2)5CH2CH(OH)COOH], two precursors leading to PFPeA (perfluoropentanoic acid) and PFHxA. Thus, FTOH anaerobic biotransformation pathways operated by microbes in the environment was likely inefficient at shortening carbon chains of FTOHs to form PFCAs (perfluorinated carboxylic acids). These results imply that anaerobic biotransformation of FTOH-based products may produce polyfluorinated acids, but is not likely a major source of PFCAs detected in anaerobic environmental matrices such as anaerobic digester sludge, landfill leachate, and anaerobic sediment under methanogenic conditions.

  11. Evaluation of anaerobic sludge volume for improving azo dye decolorization in a hybrid anaerobic reactor with built-in bioelectrochemical system.

    PubMed

    Cui, Min-Hua; Cui, Dan; Gao, Lei; Wang, Ai-Jie; Cheng, Hao-Yi

    2017-02-01

    A hybrid anaerobic reactor with built-in bioelectrochemical system (BES) has been verified for efficiently treating mixed azo dye wastewater, yet still facing many challenges, such as uncertain reactor construction and insufficient electron donors. In this study, an up-flow hybrid anaerobic reactor with built-in BES was developed for acid orange 7 (AO7) containing wastewater treatment. Cathode and real domestic wastewater both served as electron donor for driving azo dye decolorization. The decolorization efficiency (DE) of AO7 (200 mg/L) in the hybrid reactor was 80.34 ± 2.11% with volume ratio between anaerobic sludge and cathode (VRslu:cat) of 0.5:1 and hydraulic retention time (HRT) of 6 h, which was 15.79% higher than that in BES without sludge zone. DE was improved to 86.02 ± 1.49% with VRslu:cat increased to 1:1. Further increase in the VRslu:cat to 1.5:1 and 2:1, chemical oxygen demand (COD) removal efficiency was continuously improved to 28.78 ± 1.96 and 32.19 ± 0.62%, but there was no obvious DE elevation (slightly increased to 87.62 ± 2.50 and 90.13 ± 3.10%). BES presented efficient electron utilization, the electron usage ratios (EURs) in which fluctuated between 11.02 and 13.06 mol e(-)/mol AO7. It was less than half of that in sludge zone of 24.73-32.06 mol e(-)/mol AO7. The present work optimized the volume ratio between anaerobic sludge and cathode that would be meaningful for the practical application of this hybrid system.

  12. In vitro metabolism of rebaudioside B, D, and M under anaerobic conditions: comparison with rebaudioside A.

    PubMed

    Purkayastha, Sidd; Pugh, George; Lynch, Barry; Roberts, Ashley; Kwok, David; Tarka, Stanley M

    2014-03-01

    The hydrolysis of the steviol glycosides rebaudioside A, B, D, and M, as well as of steviolbioside (a metabolic intermediate) to steviol was evaluated in vitro using human fecal homogenates from healthy donors under anaerobic conditions. Incubation of each of the rebaudiosides resulted in rapid hydrolysis to steviol. Metabolism was complete within 24h, with the majority occurring within the first 8h. There were no clear differences in the rate or extent of metabolism of rebaudioside B, D, or M, relative to the comparative control rebaudioside A. The hydrolysis of samples containing 2.0mg/mL of each rebaudioside tended to take slightly longer than solutions containing 0.2mg/mL. There was no apparent gender differences in the amount of metabolism of any of the rebaudiosides, regardless of the concentrations tested. An intermediate in the hydrolysis of rebaudioside M to steviol, steviolbioside, was also found to be rapidly degraded to steviol. The results demonstrate that rebaudiosides B, D, and M are metabolized to steviol in the same manner as rebaudioside A. These data support the use of toxicology data available on steviol, and on steviol glycosides metabolized to steviol (i.e., rebaudioside A) to substantiate the safety of rebaudiosides B, D, and M.

  13. Juvenile roach (Rutilus rutilus) increase their anaerobic metabolism in response to copper exposure in laboratory conditions.

    PubMed

    Maes, Virginie; Betoulle, Stéphane; Jaffal, Ali; Dedourge-Geffard, Odile; Delahaut, Laurence; Geffard, Alain; Palluel, Olivier; Sanchez, Wilfried; Paris-Palacios, Séverine; Vettier, Aurélie; David, Elise

    2016-07-01

    This study aims to determine the potential impairment of cell energy synthesis processes (glycolysis and respiratory chain pathways) by copper in juvenile roach at different regulation levels by using a multi-marker approach. Juvenile roach were exposed to 0, 10, 50, and 100 µg/L of copper for 7 days in laboratory conditions. The glycolysis pathway was assessed by measuring the relative expression levels of 4 genes encoding glycolysis enzymes. The respiratory chain was studied by assessing the electron transport system and cytochrome c oxidase gene expression. Muscle mitochondria ultrastructure was studied, and antioxidant responses were measured. Furthermore, the main energy reserves-carbohydrates, lipids, and proteins-were measured, and cellular energy was evaluated by measuring ATP, ADP, AMP and IMP concentrations. This study revealed a disturbance of the cell energy metabolism due to copper exposure, with a significant decrease in adenylate energy charge in roach exposed to 10 μg/L of copper after 1 day. Moreover, ATP concentrations significantly decreased in roach exposed to 10 μg/L of copper after 1 day. This significant decrease persisted in roach exposed to 50 µg/L of copper after 7 days. AMP concentrations increased in all contaminated fish after 1 day of exposure. In parallel, the relative expression of 3 genes encoding for glycolysis enzymes increased in all contaminated fish after 1 day of copper exposure. Focusing on the respiratory chain, cytochrome c oxidase gene expression also increased in all contaminated fish at the two time-points. The activity of the electron transport system was not disturbed by copper, except in roach exposed to 100 µg/L of copper after 1 day. Copper induced a metabolic stress. Juvenile roach seemed to respond to the ensuing high energy demand by increasing their anaerobic metabolism, but the energy produced by the anaerobic metabolism is unable to compensate for the stress induced by copper after 7

  14. Six-week anaerobic training improves proteolytic profile of diabetic rats.

    PubMed

    Oliveira-Batista, Rogério de; Silva, Angelita; Passos, Kaique Marques Rodrigues dos; Nogueira, Rosa Maria Barilli; Seraphim, Patricia Monteiro

    2015-10-01

    To evaluate the effect of six-week anaerobic training on the mRNA expression of genes related to proteolysis Ubb (Ubiquitin), E2-14kDa, Trim63 (MuRF1 protein) and Nfkb1 in the skeletal muscle of diabetic rats. Four groups were established: DE (DiabetesExercised), DS (Diabetes Sedentary), CE (Control Exercised) and CS (Control Sedentary). The training consisted of 3 sets of 12 jumps in the liquid mean with load equivalent to 50% of BW for 6 weeks. Euthanasia occurred under ip anesthesia, and blood, adipose tissue and skeletal muscles were collected. Gene expression was quantified by RT-PCR in the gastrocnemius muscle. ANOVA one-way was used for comparison among groups, with post-hoc (Tukey) when necessary, considering p < 0.05. We observed reduction in the body weight and adipose tissue in the diabetic groups. The muscle mass was reduced in DS, which could be reversed by training (DE). Although DS and DE have presented similar body weight, the training protocol in DE promoted reduction in the adipose tissue, and increase of muscle mass. Anaerobic training was efficient to reduce glycaemia only in the diabetic animals until 6 hours after the end of training. The Trim63 gene expression was increased in DS; decreased Ubb gene level was observed in trained rats (CE and DE) compared to sedentary (CS and DS), and DE presented the lowest level of E2-14kDa gene expression. Six-week anaerobic training promoted muscle mass gain, improved glycemic control, and exerted inhibitory effect on the proteolysis of gastrocnemius muscle of diabetic rats.

  15. Co-effects of pyrene and nitrate on the activity and abundance of soil denitrifiers under anaerobic condition.

    PubMed

    Zhou, Zhi-Feng; Yao, Yan-Hong; Wang, Ming-Xia; Zuo, Xiao-Hu

    2017-04-18

    It has previously been confirmed that polycyclic aromatic hydrocarbons (PAHs) could be degraded by soil microbes coupling with denitrification, but the relationships among soil denitrifiers, PAHs, and nitrate under obligate anaerobic condition are still unclear. Here, co-effects of pyrene and nitrate on the activity and abundance of soil denitrifiers were investigated through a 45-day incubation experiment. Two groups of soil treatments with (N30) and without (N0) nitrate (30 mg kg(-1) dry soil) amendment were conducted, and each group contained three treatments with different pyrene concentrations (0, 30, and 60 mg kg(-1) dry soil denoted as P0, P30, and P60, respectively). The pyrene content, abundances of denitrification concerning genes (narG, periplasmic nitrate reductase gene; nirS, cd 1-nitrite reductase gene; nirK, copper-containing nitrite reductase gene), and productions of N2O and CO2 were measured at day 3, 14, 28, and 45, and the bacterial community structures in four represented treatments (N0P0, N0P60, N30P0, and N30P60) were analyzed at day 45. The results indicated that the treatments with higher pyrene concentration had higher final pyrene removal rates than the treatments with lower pyrene concentration. Additionally, intensive emission of N2O was detected in all treatments only at day 3, but a continuous production of CO2 was measured in each treatment during the incubation. Nitrate amendment could enhance the activity of soil denitrifiers, and be helpful for soil microbes to sustain their activity. While pyrene seemed had no influence on the productions of N2O and CO2, and amendment with pyrene or nitrate both had no obvious effect on abundances of denitrification concerning genes. Furthermore, it was nitrate but not pyrene had an obvious influence on the community structure of soil bacteria. These results revealed that, under anaerobic condition, the activity and abundance of soil denitrifiers both were insensitive to pyrene, but nitrate

  16. Anaerobic hydrocarbon degradation in petroleum-contaminated harbor sediments under sulfate-reducing and artificially imposed iron-reducing conditions

    USGS Publications Warehouse

    Coates, J.D.; Anderson, R.T.; Woodward, J.C.; Phillips, E.J.P.; Lovley, D.R.

    1996-01-01

    The potential use of iron(III) oxide to stimulate in-situ hydrocarbon degradation in anaerobic petroleum-contaminated harbor sediments was investigated. Previous studies have indicated that Fe(III)-reducing bacteria (FeRB) can oxidize some electron donors more effectively than sulfate- reducing bacteria (SRB). In contrast to previous results in freshwater sediments, the addition of Fe(III) to marine sediments from San Diego Bay, CA did not switch the terminal electron-accepting process (TEAP) from sulfate reduction to Fe-(III) reduction. Addition of Fe(III) also did not stimulate anaerobic hydrocarbon oxidation. Exposure of the sediment to air [to reoxidize Fe(II) to Fe(III)] followed by anaerobic incubation of the sediments, resulted in Fe-(III) reduction as the TEAP, but contaminant degradation was not stimulated and in some instances was inhibited. The difference in the ability of FeRB to compete with the SRB in the different sediment treatments was related to relative population sizes. Although the addition of Fe(III) did not stimulate hydrocarbon degradation, the results presented here as well as other recent studies demonstrate that there may be significant anaerobic hydrocarbon degradation under sulfate-reducing conditions in harbor sediments.

  17. Comparison of Seven Chemical Pretreatments of Corn Straw for Improving Methane Yield by Anaerobic Digestion

    PubMed Central

    Song, Zilin; GaiheYang; Liu, Xiaofeng; Yan, Zhiying; Yuan, Yuexiang; Liao, Yinzhang

    2014-01-01

    Agriculture straw is considered a renewable resource that has the potential to contribute greatly to bioenergy supplies. Chemical pretreatment prior to anaerobic digestion can increase the anaerobic digestibility of agriculture straw. The present study investigated the effects of seven chemical pretreatments on the composition and methane yield of corn straw to assess their effectiveness of digestibility. Four acid reagents (H2SO4, HCl, H2O2, and CH3COOH) at concentrations of 1%, 2%, 3%, and 4% (w/w) and three alkaline reagents (NaOH, Ca(OH)2, and NH3·H2O) at concentrations of 4%, 6%, 8%, and 10% (w/w) were used for the pretreatments. All pretreatments were effective in the biodegradation of the lignocellulosic straw structure. The straw, pretreated with 3% H2O2 and 8% Ca(OH)2, acquired the highest methane yield of 216.7 and 206.6 mL CH4 g VS −1 in the acid and alkaline pretreatments, which are 115.4% and 105.3% greater than the untreated straw. H2O2 and Ca(OH)2 can be considered as the most favorable pretreatment methods for improving the methane yield of straw because of their effectiveness and low cost. PMID:24695485

  18. Comparison of seven chemical pretreatments of corn straw for improving methane yield by anaerobic digestion.

    PubMed

    Song, Zilin; GaiheYang; Liu, Xiaofeng; Yan, Zhiying; Yuan, Yuexiang; Liao, Yinzhang

    2014-01-01

    Agriculture straw is considered a renewable resource that has the potential to contribute greatly to bioenergy supplies. Chemical pretreatment prior to anaerobic digestion can increase the anaerobic digestibility of agriculture straw. The present study investigated the effects of seven chemical pretreatments on the composition and methane yield of corn straw to assess their effectiveness of digestibility. Four acid reagents (H2SO4, HCl, H2O2, and CH3COOH) at concentrations of 1%, 2%, 3%, and 4% (w/w) and three alkaline reagents (NaOH, Ca(OH)2, and NH3·H2O) at concentrations of 4%, 6%, 8%, and 10% (w/w) were used for the pretreatments. All pretreatments were effective in the biodegradation of the lignocellulosic straw structure. The straw, pretreated with 3% H2O2 and 8% Ca(OH)2, acquired the highest methane yield of 216.7 and 206.6 mL CH4 g VS(-1) in the acid and alkaline pretreatments, which are 115.4% and 105.3% greater than the untreated straw. H2O2 and Ca(OH)2 can be considered as the most favorable pretreatment methods for improving the methane yield of straw because of their effectiveness and low cost.

  19. Improvement of mesophilic anaerobic co-digestion of agri-food waste by addition of glycerol.

    PubMed

    Serrano, Antonio; Siles, Jose A; Chica, Arturo F; Martin, M Angeles

    2014-07-01

    Anaerobic co-digestion is a promising alternative to manage agri-food waste rather than landfilling, composting or incineration. But improvement of methane yield and biodegradability is often required to optimize its economic viability. Biomethanization of agri-food solid waste presents the disadvantage of a slow hydrolytic phase, which might be enhanced by adding a readily digestible substrate such as glycerol. In this study, strawberry extrudate, fish waste and crude glycerol derived from biodiesel manufacturing are mixed at a proportion of 54:5:41, in VS (VS, total volatile solids), respectively. The mesophilic anaerobic co-digestion at lab-scale of the mixture was stable at loads lower than 1.85 g VS/L, reaching a methane yield coefficient of 308 L CH4/kg VS (0 °C, 1 atm) and a biodegradability of 96.7%, in VS. Moreover, the treatment capacity of strawberry and fish waste was increased 16% at adding the crude glycerol. An economic assessment was also carried out in order to evaluate the applicability of the proposed process. Even in a pessimistic scenario, the net balance was found to be positive. The glycerol adding implied a net saving in a range from 25.5 to 42.1 €/t if compared to landfill disposal.

  20. Comparison of different conditions, substrates and operation modes by dynamic simulation of a full-scale anaerobic SBR plant.

    PubMed

    Rönner-Holm, S G E; Zak, A; Holm, N C

    2012-01-01

    Simulation studies for a full-scale anaerobic unit of a wastewater treatment plant (WWTP) were performed using the anaerobic digestion model no. 1 (ADM1). The anaerobic full-scale plant consists of one mesophilic and one thermophilic digester, operated in an anaerobic sequential batch reactor (ASBR) mode, and sludge enrichment reactors (SER) for each digester. The digesters are fed with a mixture of vegetable waste and process wastewater from the food factory. Characteristics such as COD(total), N(total) and NH(4)-N concentrations in the influent and effluent of the digester and SERs were measured and used for input fractionation. Parameters such as level, pH, biogas amount and composition in the digester were measured online and used for calibration. For simulation studies, different temperatures and operation modes with varying chemical oxygen demand (COD) input loads corresponding to feedstocks such as fruits, vegetables and grain were analysed and compared. Higher gas production and digestion efficiency in the thermophilic reactor and in shorter cycles were found and confirmed at full scale. Serial operation mode increased the gas production, but pH inhibition occurred earlier. Feeding only biosolids into digester I and the effluent of digester I together with process water into digester II further improved gas production in serial operation mode.

  1. Sensitive and selective culture medium for detection of environmental Clostridium difficile isolates without requirement for anaerobic culture conditions.

    PubMed

    Cadnum, Jennifer L; Hurless, Kelly N; Deshpande, Abhishek; Nerandzic, Michelle M; Kundrapu, Sirisha; Donskey, Curtis J

    2014-09-01

    Effective and easy-to-use methods for detecting Clostridium difficile spore contamination would be useful for identifying environmental reservoirs and monitoring the effectiveness of room disinfection. Culture-based detection methods are sensitive for detecting C. difficile, but their utility is limited due to the requirement of anaerobic culture conditions and microbiological expertise. We developed a low-cost selective broth medium containing thioglycolic acid and l-cystine, termed C. difficile brucella broth with thioglycolic acid and l-cystine (CDBB-TC), for the detection of C. difficile from environmental specimens under aerobic culture conditions. The sensitivity and specificity of CDBB-TC (under aerobic culture conditions) were compared to those of CDBB (under anaerobic culture conditions) for the recovery of C. difficile from swabs collected from hospital room surfaces. CDBB-TC was significantly more sensitive than CDBB for recovering environmental C. difficile (36/41 [88%] versus 21/41 [51%], respectively; P = 0.006). C. difficile latex agglutination, an enzyme immunoassay for toxins A and B or glutamate dehydrogenase, and a PCR for toxin B genes were all effective as confirmatory tests. For 477 total environmental cultures, the specificity of CDBB-TC versus that of CDBB based upon false-positive yellow-color development of the medium without recovery of C. difficile was 100% (0 false-positive results) versus 96% (18 false-positive results), respectively. False-positive cultures for CDBB were attributable to the growth of anaerobic non-C. difficile organisms that did not grow in CDBB-TC. Our results suggest that CDBB-TC provides a sensitive and selective medium for the recovery of C. difficile organisms from environmental samples, without the need for anaerobic culture conditions. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

  2. Reactor performance and microbial community dynamics during solid-state anaerobic digestion of corn stover at mesophilic and thermophilic conditions.

    PubMed

    Shi, Jian; Wang, Zhongjiang; Stiverson, Jill A; Yu, Zhongtang; Li, Yebo

    2013-05-01

    Reactor performance and microbial community dynamics were investigated during solid state anaerobic digestion (SS-AD) of corn stover at mesophilic and thermophilic conditions. Thermophilic SS-AD led to faster and greater reductions of cellulose and hemicelluloses during the first 12 days compared to mesophilic SS-AD. However, accumulation of volatile fatty acids (VFAs) was 5-fold higher at thermophilic than mesophilic temperatures, resulting in a large pH drop during days 6-12 in the thermophilic reactors. Culture-based enumeration revealed 10-50 times greater populations of cellulolytic and xylanolytic microbes during thermophilic SS-AD than mesophilic SS-AD. DGGE analysis of PCR amplified 16S rRNA genes showed dynamic shifts, especially during the thermophilic SS-AD, of bacterial and archaeal communities over the 38 days of SS-AD as a result of acclimation of the initial seed microbial consortia to the lignocellulosic feedstock. The findings of this study can guide future studies to improve efficiency and stability of SS-AD. Copyright © 2013 Elsevier Ltd. All rights reserved.

  3. Physiological activities associated with biofilm growth in attached and suspended growth bioreactors under aerobic and anaerobic conditions.

    PubMed

    Naz, Iffat; Seher, Shama; Perveen, Irum; Saroj, Devendra P; Ahmed, Safia

    2015-01-01

    This research work evaluated the biofilm succession on stone media and compared the biochemical changes of sludge in attached and suspended biological reactors operated under aerobic and anaerobic conditions. Stones incubated (30±2°C) with activated sludge showed a constant increase in biofilm weight up to the fifth and seventh week time under anaerobic and aerobic conditions, respectively, where after reduction (>80%) the most probable number index of pathogen indicators on ninth week was recorded. Reduction in parameters such as biological oxygen demand (BOD) (47.7%), chemical oxygen demand (COD, 41%), nitrites (60.2%), nitrates (105.5%) and phosphates (58.9%) and increase in dissolved oxygen (176.5%) of sludge were higher in aerobic attached growth reactors as compared with other settings. While, considerable reductions in these values were also observed (BOD, 53.8%; COD, 2.8%; nitrites, 28.6%; nitrates, 31.7%; phosphates, 41.4%) in the suspended growth system under anaerobic conditions. However, higher sulphate removal was observed in suspended (40.9% and 54.9%) as compared with biofilm reactors (28.2% and 29.3%). Six weeks biofilm on the stone media showed maximum physiological activities; thus, the operational conditions should be controlled to keep the biofilm structure similar to six-week-old biofilm, and can be used in fixed biofilm reactors for wastewater treatment.

  4. Anaerobic Biodegradation Tests of Poly(lactic acid) under Mesophilic and Thermophilic Conditions Using a New Evaluation System for Methane Fermentation in Anaerobic Sludge

    PubMed Central

    Yagi, Hisaaki; Ninomiya, Fumi; Funabashi, Masahiro; Kunioka, Masao

    2009-01-01

    Anaerobic biodegradation tests of poly(lactic acid) (PLA) powder were done at the thermophilic (55 °C) and mesophilic temperature (35 °C) under aquatic conditions [total solid concentrations of the used sludge were 2.07% (at 55 °C) and 2.24% (at 35 °C)] using a newly developed evaluation system. With this system, the evolved biogas is collected in a gas sampling bag at atmospheric pressure. This method is more convenient than using a pressure transducer or inverted graduated cylinder submerged in water. PLA was degraded about 60% in 30 days, about 80% in 40 days and about 90% in 60 days at 55 °C. On the other hand, the PLA degradation started in 55 days at 35 °C and degradation rate was much slower than at 55 °C. PMID:19865521

  5. Anaerobic biodegradation tests of poly(lactic acid) under mesophilic and thermophilic conditions using a new evaluation system for methane fermentation in anaerobic sludge.

    PubMed

    Yagi, Hisaaki; Ninomiya, Fumi; Funabashi, Masahiro; Kunioka, Masao

    2009-09-02

    Anaerobic biodegradation tests of poly(lactic acid) (PLA) powder were done at the thermophilic (55 degrees C) and mesophilic temperature (35 degrees C) under aquatic conditions [total solid concentrations of the used sludge were 2.07% (at 55 degrees C) and 2.24% (at 35 degrees C)] using a newly developed evaluation system. With this system, the evolved biogas is collected in a gas sampling bag at atmospheric pressure. This method is more convenient than using a pressure transducer or inverted graduated cylinder submerged in water. PLA was degraded about 60% in 30 days, about 80% in 40 days and about 90% in 60 days at 55 degrees C. On the other hand, the PLA degradation started in 55 days at 35 degrees C and degradation rate was much slower than at 55 degrees C.

  6. Anaerobic co-digestion of food waste and chemically enhanced primary-treated sludge under mesophilic and thermophilic conditions.

    PubMed

    Obulisamy, Parthiba Karthikeyan; Chakraborty, Debkumar; Selvam, Ammaiyappan; Wong, Jonathan W C

    2016-12-01

    Anaerobic co-digestion of food waste with primary sewage sludge is beneficial for urban centers, while the optimized conditions reported in the literature are not locally suitable for Hong Kong. Therefore, the present study was aimed to develop an optimized mixing ratio of food waste to chemically enhanced primary-treated sewer sludge (CEPT) for co-digestion using batch tests under mesophilic (37°C) and thermophilic (55°C) conditions. The mixing ratios of 1:1, 1:2, 1:3, 2:1 and 3:1 (v v(-1)) of food waste to CEPT sludge was tested under the following conditions: temperature - 35°C and 55°C; pH - not regulated; agitation - 150 rpm and time - 20 days. The thermophilic incubations led a good hydrolysis rate and 2-12-fold higher enzyme activities than in mesophilic incubations for different mixing ratios. While the acidogenesis were found retarded that leading to 'sour and stuck' digestion for all mixing ratio of food waste to CEPT sludge from thermophilic incubations. The measured zeta potential was most favourable (-5 to -16.8 mV) for methane production under thermophilic incubations; however the CH4 recovery was less than that in mesophilic incubations. The results suggested that the quick hydrolysis and subsequent acid accumulation under thermophilic incubation lead to inhibited methanogenesis at the early stage than in mesophilic systems. It is concluded that buffer addition is therefore required for any mixing ratio of food waste to CEPT sludge for improved CH4 recovery for both mesophilic and thermophilic operations.

  7. Microbial community structure reveals how microaeration improves fermentation during anaerobic co-digestion of brown water and food waste.

    PubMed

    Lim, Jun Wei; Chiam, Jun An; Wang, Jing-Yuan

    2014-11-01

    The purpose of this study was to investigate the impact of microaeration on the fermentation process during anaerobic co-digestion of brown water (BW) and food waste (FW). This was achieved by daily monitoring of reactor performance and the determination of its bacterial consortium towards the end of the study. Molecular cloning and sequencing results revealed that bacteria within phyla Firmicutes and Bacteriodetes represented the dominant phylogenetic group. As compared to anaerobic conditions, the fermentation of BW and FW under microaeration conditions gave rise to a significantly more diverse bacterial population and higher proportion of bacterial clones affiliated to the phylum Firmicutes. The acidogenic reactor was therefore able to metabolize a greater variety of substrates leading to higher hydrolysis rates as compared to the anaerobic reactor. Other than enhanced fermentation, microaeration also led to a shift in fermentation production pattern where acetic acid was metabolized for the synthesis of butyric acid.

  8. Biogeochemical changes induced in uranium mining waste pile samples by uranyl nitrate treatments under anaerobic conditions.

    PubMed

    Geissler, A; Merroun, M; Geipel, G; Reuther, H; Selenska-Pobell, S

    2009-06-01

    Response of the subsurface soil bacterial community of a uranium mining waste pile to treatments with uranyl nitrate over different periods of time was studied under anaerobic conditions. The fate of the added U(VI) without supplementation with electron donors was investigated as well. By using 16S rRNA gene retrieval, we demonstrated that incubation with uranyl nitrate for 4 weeks resulted in a strong reduction in and even disappearance of some of the most predominant bacterial groups of the original sample. Instead, a strong proliferation of denitrifying and uranium-resistant populations of Rahnella spp. from Gammaproteobacteria and of Firmicutes occurred. After longer incubations for 14 weeks with uranyl nitrate, bacterial diversity increased and populations intrinsic to the untreated samples such as Bacteroidetes and Deltaproteobacteria propagated and replaced the above-mentioned uranium-resistant groups. This indicated that U(VI) was immobilized. Mössbauer spectroscopic analysis revealed an increased Fe(III) reduction by increasing the incubation time from four to 14 weeks. This result signified that Fe(III) was used as an electron acceptor by the bacterial community established at the later stages of the treatment. X-ray absorption spectroscopic analysis demonstrated that no detectable amounts of U(VI) were reduced to U(IV) in the time frames of the performed experiments. The reason for this observation is possibly due to the low level of electron donors in the studied oligotrophic environment. Time-resolved laser-induced fluorescence spectroscopic analysis demonstrated that most of the added U(VI) was bound by organic or inorganic phosphate phases both of biotic origin.

  9. [Influences of humic acids on the dissimilatory iron reduction of red soil in anaerobic condition].

    PubMed

    Xu, Li-na; Li, Zhong-pei; Che, Yu-ping

    2009-01-01

    Iron oxide is abundant in red soil. Reduction and oxidation of iron oxide are important biogeochemical processes. In this paper, we reported the effects of humic acid on dissimilatory iron reduction (DISSIR) in red soil by adding glucose or humic acid (HA), under an anaerobic condition. Results indicated that DISSIR is weak for the red soil with a low content of organic matter, Glucose that act as electron donators promoted the process of DISSIR in red soil. HA added to soil solely didn't accelerate the DISSIR since it couldn't provide electron donators to microbe. However, adding of both glucose and HA promoted the DISSIR at the beginning of the incubation but then inhibited the process, which maybe caused by the effects of precipitation and adsorption of red soil. Concentrations of HA strongly affected the DISSIR, HA at low concentrations(0.20 and 0.02 g/kg) had weak effects, while HA at a high concentration (2.00 g/kg) promoted the process at the beginning and then inhibited it. HA extracted from different materials had distinct effects on the DISSIR. HA from Weathering coal of Datong in Shanxi Province (HAs), lignite of Gongxian in Henan Province (HAh) and Dianchi Lake sediment in Kunming of Yunnan Province (HAk) all promoted the DISSIR at the beginning of the incubation. However, at the end of incubation, HAk with a low aromaticity still promoted the process, while HAs and HAh with a higher aromaticity weakened the DISSIR. This may be due to the increase in adsorption of soil with the aromaticity of HA.

  10. Direct production of organic acids from starch by cell surface-engineered Corynebacterium glutamicum in anaerobic conditions

    PubMed Central

    2013-01-01

    We produced organic acids, including lactate and succinate, directly from soluble starch under anaerobic conditions using high cell-density cultures of Corynebacterium glutamicum displaying α-amylase (AmyA) from Streptococcus bovis 148 on the cell surface. Notably, reactions performed under anaerobic conditions at 35 and 40°C, which are higher than the optimal growth temperature of 30°C, showed 32% and 19%, respectively, higher productivity of the organic acids lactate, succinate, and acetate compared to that at 30°C. However, α-amylase was not stably anchored and released into the medium from the cell surface during reactions at these higher temperatures, as demonstrated by the 61% and 85% decreases in activity, respectively, from baseline, compared to the only 8% decrease at 30°C. The AmyA-displaying C. glutamicum cells retained their starch-degrading capacity during five 10 h reaction cycles at 30°C, producing 107.8 g/l of total organic acids, including 88.9 g/l lactate and 14.0 g/l succinate. The applicability of cell surface-engineering technology for the production of organic acids from biomass by high cell-density cultures of C. glutamicum under anaerobic conditions was demonstrated. PMID:24342107

  11. Impact of ArcA loss in Shewanella oneidensis revealed by comparative proteomics under aerobic and anaerobic conditions

    SciTech Connect

    Yuan, Jie; Wei, Buyun; Lipton, Mary S.; Gao, Haichun

    2012-06-01

    Shewanella inhabit a wide variety of niches in nature and can utilize a broad spectrum of electron acceptors under anaerobic conditions. How they modulate their gene expression to adapt is poorly understood. ArcA, homologue of a global regulator controlling hundreds of genes involved in aerobic and anaerobic respiration in E. coli, was shown to be important in aerobiosis/anaerobiosis of S. oneidensis as well. Loss of ArcA, in addition to altering transcription of many genes, resulted in impaired growth under aerobic condition, which was not observed in E. coli. To further characterize the impact of ArcA loss on gene expression on the level of proteome under aerobic and anaerobic conditions, liquid-chromatography-mass-spectrometry (LC-MS) based proteomic approach was employed. Results show that ArcA loss led to globally altered gene expression, generally consistent with that observed with transcripts. Comparison of transcriptomic and proteomic data permitted identification of 17 high-confidence ArcA targets. Moreover, our data indicate that ArcA is required for regulation of cytochrome c proteins, and the menaquinone level may play a role in regulating ArcA as in E. coli. Proteomic-data-guided growth assay revealed that the aerobic growth defect of ArcA mutant is presumably due to impaired peptide utilization.

  12. Effect of volatile fatty acids in anaerobic conditions on viability of helminth ova (Ascaris suum) in sanitization of municipal sludge.

    PubMed

    Rojas-Oropeza, Marcelo; Hernández-Uresti, Alejandro S; Ortega-Charleston, Luis S; Cabirol, Nathalie

    2017-09-01

    The present work aimed at evaluating the effect of four different mixtures of diverse volatile fatty acids (VFAs) on the viability of helminth ova (Ascaris suum), under mesophilic (35°C) anaerobic conditions and at different incubation times, in order to reproduce the process of two-phase anaerobic digestion. The mixtures of VFAs contained acetic, propionic, butyric, valeric, and isovaleric acids, used at concentrations normally found in acidogenic anaerobic digesters. The four treatments all showed a reduction in Ascaris suum ova viability, among which Treatment III (4.2 g-acetic acid L(-1) +  2.2 g-propionic acid L(-1) + 0.6 g-valeric acid L(-1) + 0.6 g-isovaleric acid L(-1)) resulted the most efficient. We found that the full effect of VFAs on the viability loss of Ascaris suum ova in mesophilic conditions requires a minimum incubation time of 3 days. The highest efficiency in the loss of viability was observed with Treatment III and 4-day incubation. Interestingly, the proportion of acetic acid was three times as much in this treatment than in the other ones and resulted in an effect in a minimum time of 3 days. The mesophilic condition, however, was not sufficient to induce a complete loss of viability.

  13. Mechanisms of Chromium and Uranium Toxicity in Pseudomonas stutzeri RCH2 Grown under Anaerobic Nitrate-Reducing Conditions

    PubMed Central

    Thorgersen, Michael P.; Lancaster, W. Andrew; Ge, Xiaoxuan; Zane, Grant M.; Wetmore, Kelly M.; Vaccaro, Brian J.; Poole, Farris L.; Younkin, Adam D.; Deutschbauer, Adam M.; Arkin, Adam P.; Wall, Judy D.; Adams, Michael W. W.

    2017-01-01

    Chromium and uranium are highly toxic metals that contaminate many natural environments. We investigated their mechanisms of toxicity under anaerobic conditions using nitrate-reducing Pseudomonas stutzeri RCH2, which was originally isolated from a chromium-contaminated aquifer. A random barcode transposon site sequencing library of RCH2 was grown in the presence of the chromate oxyanion (Cr[VI]O42−) or uranyl oxycation (U[VI]O22+). Strains lacking genes required for a functional nitrate reductase had decreased fitness as both metals interacted with heme-containing enzymes required for the later steps in the denitrification pathway after nitrate is reduced to nitrite. Cr[VI]-resistance also required genes in the homologous recombination and nucleotide excision DNA repair pathways, showing that DNA is a target of Cr[VI] even under anaerobic conditions. The reduced thiol pool was also identified as a target of Cr[VI] toxicity and psest_2088, a gene of previously unknown function, was shown to have a role in the reduction of sulfite to sulfide. U[VI] resistance mechanisms involved exopolysaccharide synthesis and the universal stress protein UspA. As the first genome-wide fitness analysis of Cr[VI] and U[VI] toxicity under anaerobic conditions, this study provides new insight into the impact of Cr[VI] and U[VI] on an environmental isolate from a chromium contaminated site, as well as into the role of a ubiquitous protein, Psest_2088. PMID:28848534

  14. Bioaugmentation with hydrolytic microbes to improve the anaerobic biodegradability of lignocellulosic agricultural residues.

    PubMed

    Tsapekos, P; Kougias, P G; Vasileiou, S A; Treu, L; Campanaro, S; Lyberatos, G; Angelidaki, I

    2017-03-12

    Bioaugmentation with hydrolytic microbes was applied to improve the methane yield of bioreactors fed with agricultural wastes. The efficiency of Clostridium thermocellum and Melioribacter roseus to degrade lignocellulosic matter was evaluated in batch and continuously stirred tank reactors (CSTRs). Results from batch assays showed that C. thermocellum enhanced the methane yield by 34%. A similar increase was recorded in CSTR during the bioaugmentation period; however, at steady-state the effect was noticeably lower (7.5%). In contrast, the bioaugmentation with M. roseus did not promote markedly the anaerobic biodegradability, as the methane yield was increased up to 10% in batch and no effect was shown in CSTR. High-throughput 16S rRNA amplicon sequencing was used to assess the effect of bioaugmentation strategies on bacterial and archaeal populations. The microbial analysis revealed that both strains were not markedly resided into biogas microbiome. Additionally, the applied strategies did not alter significantly the microbial communities.

  15. Microbial Anaerobic Ammonium Oxidation Under Iron Reducing Conditions, Alternative Electron Acceptors

    NASA Astrophysics Data System (ADS)

    Ruiz-Urigüen, M.; Jaffe, P. R.

    2015-12-01

    Autotrophic Acidimicrobiaceae-bacterium named A6 (A6), part of the Actinobacteria phylum have been linked to anaerobic ammonium (NH4+) oxidation under iron reducing conditions. These organisms obtain their energy by oxidizing NH4+ and transferring the electrons to a terminal electron acceptor (TEA). Under environmental conditions, the TEAs are iron oxides [Fe(III)], which are reduced to Fe(II), this process is known as Feammox. Our studies indicate that alternative forms of TEAs can be used by A6, e.g. iron rich clays (i.e. nontronite) and electrodes in bioelectrochemical systems such as Microbial Electrolysis Cells (MECs), which can sustain NH4+removal and A6 biomass production. Our results show that nontronite can support Feammox and promote bacterial cell production. A6 biomass increased from 4.7 x 104 to 3.9 x 105 cells/ml in 10 days. Incubations of A6 in nontronite resulted in up to 10 times more NH4+ removal and 3 times more biomass production than when ferrihydrite is used as the Fe(III) source. Additionally, Fe in nontronite can be reoxidized by aeration and A6 can reutilize it; however, Fe is still finite in the clay. In contrast, in MECs, A6 harvest electrons from NH4+ and use an anode as an unlimited TEA, as a result current is produced. We operated multiple MECs in parallel using a single external power source, as described by Call & Logan (2011). MECs were run with an applied voltage of 0.7V and different growing mediums always containing initial 5mM NH4+. Results show that current production is favored when anthraquinone-2,6-disulfonate (AQDS), an electron shuttled, is present in the medium as it facilitates the transfer of electrons from the bacterial cell to the anode. Additionally, A6 biomass increased from 1 x 104 to 9.77 x 105cells/ml in 14 days of operation. Due to Acidimicrobiaceae-bacterium A6's ability to use various TEAs, MECs represent an alternative, iron-free form, for optimized biomass production of A6 and its application in NH4

  16. Tolerance of anaerobic conditions caused by flooding during germination and early growth in rice (Oryza sativa L.)

    PubMed Central

    Miro, Berta; Ismail, Abdelbagi M.

    2013-01-01

    Rice is semi-aquatic, adapted to a wide range of hydrologies, from aerobic soils in uplands to anaerobic and flooded fields in waterlogged lowlands, to even deeply submerged soils in flood-prone areas. Considerable diversity is present in native rice landraces selected by farmers over centuries. Our understanding of the adaptive features of these landraces to native ecosystems has improved considerably over the recent past. In some cases, major genes associated with tolerance have been cloned, such as SUB1A that confers tolerance of complete submergence and SNORKEL genes that control plant elongation to escape deepwater. Modern rice varieties are sensitive to flooding during germination and early growth, a problem commonly encountered in rainfed areas, but few landraces capable of germination under these conditions have recently been identified, enabling research into tolerance mechanisms. Major QTLs were also identified, and are being targeted for molecular breeding and for cloning. Nevertheless, limited progress has been made in identifying regulatory processes for traits that are unique to tolerant genotypes, including faster germination and coleoptile elongation, formation of roots and leaves under hypoxia, ability to catabolize starch into simple sugars for subsequent use in glycolysis and fermentative pathways to generate energy. Here we discuss the state of knowledge on the role of the PDC-ALDH-ACS bypass and the ALDH enzyme as the likely candidates effective in tolerant rice genotypes. Potential involvement of factors such as cytoplasmic pH regulation, phytohormones, reactive oxygen species scavenging and other metabolites is also discussed. Further characterization of contrasting genotypes would help in elucidating the genetic and biochemical regulatory and signaling mechanisms associated with tolerance. This could facilitate breeding rice varieties suitable for direct seeding systems and guide efforts for improving waterlogging tolerance in other crops

  17. Co-conditioning of the anaerobic digested sludge of a municipal wastewater treatment plant with alum sludge: benefit of phosphorus reduction in reject water.

    PubMed

    Yang, Y; Zhao, Y Q; Babatunde, A O; Kearney, P

    2007-12-01

    In this study, alum sludge was introduced to co-conditioning and dewatering with an anaerobic digested sludge from a municipal wastewater treatment plant, to examine the role of the alum sludge in improving the dewaterbility of the mixed sludge and also in immobilizing phosphorus in the reject water. Experiments have demonstrated that the optimal mix ratio for the two sludges is 2:1 (anaerobic digested sludge:alum sludge: volume basis), and this can bring approximately 99% phosphorus reduction in the reject water through the adsorption of phosphorus by alum in the sludge. The phosphorus loading in wastewater treatment plants is itself derived from the recycling of reject water during the wastewater treatment process. Consequently, this co-conditioning and dewatering strategy can achieve a significant reduction in phosphorus loading in wastewater treatment plants. In addition, the use of the alum sludge has been shown to beneficially enhance the dewaterability of the resultant mixed sludge, by decreasing both the specific resistance to filtration and the capillary suction time. This is attributed to the alum sludge acting in charge neutralization and/or as adsorbent for phosphate in the aqueous phase of the sludge. Experiments have also demonstrated that the optimal polymer (Superfloc C2260, Cytec, Botlek, Netherlands) dose for the anaerobic digested sludge was 120 mg/L, while the optimal dose for the mixed sludge (mix ratio 2:1) was 15 mg/L, highlighting a huge savings in polymer addition. Therefore, from the technical perspective, the co-conditioning and dewatering strategy can be viewed as a "win-win" situation. However, for its full-scale application, integrated cost-effective analysis of process capabilities, sludge transport, increased cake disposal, additional administration, polymer saving, and so on, should be factored in.

  18. Effect Of Imposed Anaerobic Conditions On Metals Release From Acid-Mine Drainage Contaminated Streambed Sediments

    EPA Science Inventory

    Remediation of streams influenced by mine-drainage may require removal and burial of metal-containing bed sediments. Burial of aerobic sediments into an anaerobic environment may release metals, such as through reductive dissolution of metal oxyhydroxides. Mining-impacted aerob...

  19. Effect Of Imposed Anaerobic Conditions On Metals Release From Acid-Mine Drainage Contaminated Streambed Sediments

    EPA Science Inventory

    Remediation of streams influenced by mine-drainage may require removal and burial of metal-containing bed sediments. Burial of aerobic sediments into an anaerobic environment may release metals, such as through reductive dissolution of metal oxyhydroxides. Mining-impacted aerob...

  20. Comparison of Sterol Import under Aerobic and Anaerobic Conditions in Three Fungal Species, Candida albicans, Candida glabrata, and Saccharomyces cerevisiae

    PubMed Central

    Zavrel, Martin; Hoot, Sam J.

    2013-01-01

    Sterol import has been characterized under various conditions in three distinct fungal species, the model organism Saccharomyces cerevisiae and two human fungal pathogens Candida glabrata and Candida albicans, employing cholesterol, the sterol of higher eukaryotes, as well as its fungal equivalent, ergosterol. Import was confirmed by the detection of esterified cholesterol within the cells. Comparing the three fungal species, we observe sterol import under three different conditions. First, as previously well characterized, we observe sterol import under low oxygen levels in S. cerevisiae and C. glabrata, which is dependent on the transcription factor Upc2 and/or its orthologs or paralogs. Second, we observe sterol import under aerobic conditions exclusively in the two pathogenic fungi C. glabrata and C. albicans. Uptake emerges during post-exponential-growth phases, is independent of the characterized Upc2-pathway and is slower compared to the anaerobic uptake in S. cerevisiae and C. glabrata. Third, we observe under normoxic conditions in C. glabrata that Upc2-dependent sterol import can be induced in the presence of fetal bovine serum together with fluconazole. In summary, C. glabrata imports sterols both in aerobic and anaerobic conditions, and the limited aerobic uptake can be further stimulated by the presence of serum together with fluconazole. S. cerevisiae imports sterols only in anaerobic conditions, demonstrating aerobic sterol exclusion. Finally, C. albicans imports sterols exclusively aerobically in post-exponential-growth phases, independent of Upc2. For the first time, we provide direct evidence of sterol import into the human fungal pathogen C. albicans, which until now was believed to be incapable of active sterol import. PMID:23475705

  1. Improving efficiency of existing air-conditioning

    NASA Technical Reports Server (NTRS)

    Obler, H. D.

    1977-01-01

    Inexpensive duct work changes improves hot-and-cold deck air conditioning units. Energy cost of reheating cooled air can be eliminated by tying all cold air decks to one air-conditioning unit and all hot decks to another. Resultant energy savings are easily possible with two or more units.

  2. Thermophilic and cellulolytic consortium isolated from composting plants improves anaerobic digestion of cellulosic biomass: Toward a microbial resource management approach.

    PubMed

    Kinet, R; Destain, J; Hiligsmann, S; Thonart, P; Delhalle, L; Taminiau, B; Daube, G; Delvigne, F

    2015-01-01

    A cellulolytic consortium was isolated from a composting plant in order to boost the initial hydrolysis step encountered in anaerobic digestion. Improvement of the cellulose degradation, as well as biogas production, was observed for the cultures inoculated with the exogenous consortium. Metagenomics analyses pointed out a weak richness (related to the number of OTUs) of the exogenous consortium induced by the selective pressure (cellulose as sole carbon source) met during the initial isolation steps. Main microbial strains determined were strictly anaerobic and belong to the Clostridia class. During cellulose anaerobic degradation, pH drop induced a strong modification of the microbial population. Despite the fact that richness and evenness were very weak, the exogenous consortium was able to adapt and to maintain the cellulolytic degradation potential. This important result point out the fact that simplified microbial communities could be used in order to increase the robustness of mixed cultures involved in environmental biotechnology.

  3. An anaerobic field injection experiment in a landfill leachate plume, Grindsted, Denmark: 2. Deduction of anaerobic (methanogenic, sulfate-, and Fe (III)-reducing) redox conditions

    NASA Astrophysics Data System (ADS)

    Albrechtsen, Hans-JøRgen; Bjerg, Poul L.; Ludvigsen, Liselotte; Rügge, Kirsten; Christensen, Thomas H.

    1999-04-01

    Redox conditions may be environmental factors which affect the fate of the xenobiotic organic compounds. Therefore the redox conditions were characterized in an anaerobic, leachate-contaminated aquifer 15-60 m downgradient from the Grindsted Landfill, Denmark, where an field injection experiment was carried out. Furthermore, the stability of the redox conditions spatially and over time were investigated, and different approaches to deduce the redox conditions were evaluated. The redox conditions were evaluated in a set of 20 sediment and groundwater samples taken from locations adjacent to the sediment samples. Samples were investigated with respect to groundwater chemistry, including hydrogen and volatile fatty acids (VFAs) and sediment geochemistry, and bioassays were performed. The groundwater chemistry, including redox sensitive species for a large number of samples, varied over time during the experimental period of 924 days owing to variations in the leachate from the landfill. However, no indication of change in the redox environment resulting from the field injection experiment or natural variation was observed in the individual sampling points. The methane, Fe(II), hydrogen, and VFA groundwater chemistry parameters strongly indicated a Fe(III)-reducing environment. This was further supported by the bioassays, although methane production and sulfate-reduction were also observed in a few samples close to the landfill. On the basis of the calculated carbon conversion, Fe(III) was the dominant electron acceptor in the region of the aquifer, which was investigated. Because of the complexity of a landfill leachate plume, several redox processes may occur simultaneously, and an array of methods must be applied for redox characterization in such multicomponent systems.

  4. New insights into the key microbial phylotypes of anaerobic sludge digesters under different operational conditions.

    PubMed

    Hao, Liping; Bize, Ariane; Conteau, Delphine; Chapleur, Olivier; Courtois, Sophie; Kroff, Pablo; Desmond-Le Quéméner, Elie; Bouchez, Théodore; Mazéas, Laurent

    2016-10-01

    Analyses on bacterial, archaeal communities at family level and methane-production metabolism were conducted in thirteen full-scale and pilot-scale anaerobic sludge digesters. These digesters were operated at different conditions regarding solids concentration, sludge retention time, organic loading rate and feedstock composition, seeking to optimize digester capacity. Correlations between process parameters and identified microbial phylotypes were evaluated based on relative abundance of these phylotypes determined by Quantitative PCR and 16S rDNA amplicon sequencing. Results showed that, Total Solids concentration (TS), among the evaluated operational parameters, demonstrated the most positive correlation with chemical parameters (including NH3 and VFAs) and significant impact on the abundance of key microbial phylotypes regardless of other factors. Digesters were grouped into 'Higher-TS' with higher stress (TS > 44 g/L, NH3 > 90 mg/L, VFAs > 300 mg/L) and 'Lower-TS' under easier status (TS ≤ 44 g/L, NH3 < 120 mg/L, VFAs < 525 mg/L) in this study. We identified the key microbial phylotypes, i.e. the most abundant and discriminating populations, in 'Higher-TS' digesters with high biogas production rate, which were the class Clostridia, the family Methanosarcinaceae and the order Methanobacteriales. Thermoanaerobacteraceae and Syntrophomonadaceae were identified as key families of Clostridia. Methane was produced both from acetoclastic and hydrogenotrophic methanogenesis. By contrast, in 'Higher-TS' digesters with low biogas production rate, the classes Alpha-, Beta- and Gamma-proteobacteria were detected in higher percentages, of which Rhodobacteraceae, Comamonadaceae and Xanthomonadaceae were the most abundant families respectively, and Methanomicrobiales was the prevailing methanogen order. Consistently, hydrogenotrophic pathway was predominant for methanogenesis, indicating existence of syntrophic acetate oxidation in such 'high-stress', low

  5. Humic acids facilitated microbial reduction of polymeric Pu(IV) under anaerobic conditions.

    PubMed

    Xie, Jinchuan; Liang, Wei; Lin, Jianfeng; Zhou, Xiaohua; Li, Mei

    2017-08-25

    Flavins and humic substances have been extensively studied with emphasis on their ability to transfer extracellular electrons to insoluble metal oxides. Nevertheless, whether the low-solubility Pu(IV) polymers are microbially reduced to aqueous Pu(III) remains uncertain. Experiments were conducted under anaerobic and slightly alkaline conditions to study the difference between humic acids and flavins to transport extracellular electrons to Pu(IV) polymers. Our study demonstrates that Shewanella putrefaciens was unable to directly reduce polymeric Pu(IV) with a notably low reduction rate (3.4×10(-12)mol/L Pu(III)aq within 144h). The relatively high redox potential of flavins reveals the thermodynamically unfavorable reduction: Eh(PuO2(am)/Pu(3+))

  6. Strain and bioprocess improvement of a thermophilic anaerobe for the production of ethanol from wood

    SciTech Connect

    Herring, Christopher D.; Kenealy, William R.; Shaw, A. Joe; Covalla, Sean F.; Olson, Daniel G.; Zhang, Jiayi; Sillers, W. Ryan; Tsakraklides, Vasiliki; Bardsley, John S.; Rogers, Stephen R.; Thorne, Philip G.; Johnson, Jessica P.; Foster, Abigail; Shikhare, Indraneel D.; Klingeman, Dawn M.; Brown, Steven D.; Davison, Brian H.; Lynd, Lee R.; Hogsett, David A.

    2016-06-16

    Here, the thermophilic, anaerobic bacterium Thermoanaerobacterium saccharolyticum digests hemicellulose and utilizes the major sugars present in biomass. It was previously engineered to produce ethanol at yields equivalent to yeast. While saccharolytic anaerobes have been long studied as potential biomass-fermenting organisms, development efforts for commercial ethanol production have not been reported.

  7. Strain and bioprocess improvement of a thermophilic anaerobe for the production of ethanol from wood

    DOE PAGES

    Herring, Christopher D.; Kenealy, William R.; Shaw, A. Joe; ...

    2016-06-16

    Here, the thermophilic, anaerobic bacterium Thermoanaerobacterium saccharolyticum digests hemicellulose and utilizes the major sugars present in biomass. It was previously engineered to produce ethanol at yields equivalent to yeast. While saccharolytic anaerobes have been long studied as potential biomass-fermenting organisms, development efforts for commercial ethanol production have not been reported.

  8. Improving anaerobic digestion of a cellulosic waste via routine bioaugmentation with cellulolytic microorganisms.

    PubMed

    Martin-Ryals, Ana; Schideman, Lance; Li, Peng; Wilkinson, Henry; Wagner, Richard

    2015-01-01

    This study investigated routine bioaugmentation in the acid-phase of a two-phase anaerobic digestion (AD) process treating a largely cellulosic waste material generated from sweet corn processing. A proprietary cellulolytic bioculture was used for bioaugmentation with the aim of increasing substrate hydrolysis to improve overall methanogenic efficiency. In a sequencing batch experiment routine bioaugmentation achieved significantly greater soluble chemical oxygen demand (sCOD) generation (+25%) and methane production (+15%) compared to one-time bioaugmentation. In a continuous bench-scale system, routine bioaugmentation increased acid-phase sCOD by 29-68% and acetic acid concentrations by 31-34%. This benefit to hydrolysis and acetogenesis subsequently led to sustained increase in methane production (+56%) compared to non-bioaugmentation. A cursory economic analysis indicated that routine bioaugmentation could improve the economics of corn waste AD by $27-$34/dry tonne of waste. Overall, routine bioaugmentation showed significant promise for improving AD of corn waste by achieving sustained increases in substrate hydrolysis and methane production. Copyright © 2015. Published by Elsevier Ltd.

  9. Membrane biofilm development improves COD removal in anaerobic membrane bioreactor wastewater treatment.

    PubMed

    Smith, Adam L; Skerlos, Steven J; Raskin, Lutgarde

    2015-09-01

    Membrane biofilm development was evaluated to improve psychrophilic (15°C) anaerobic membrane bioreactor (AnMBR) treatment of domestic wastewater. An AnMBR containing three replicate submerged membrane housings with separate permeate collection was operated at three levels of membrane fouling by independently controlling biogas sparging for each membrane unit. High membrane fouling significantly improved permeate quality, but resulted in dissolved methane in the permeate at a concentration two to three times the equilibrium concentration predicted by Henry's law. Illumina sequencing of 16S rRNA targeting Bacteria and Archaea and reverse transcription-quantitative polymerase chain reaction targeting the methyl coenzyme-M reductase (mcrA) gene in methanogens indicated that the membrane biofilm was enriched in highly active methanogens and syntrophic bacteria. Restoring fouled membranes to a transmembrane pressure (TMP) near zero by increasing biogas sparging did not disrupt the biofilm's treatment performance, suggesting that microbes in the foulant layer were tightly adhered and did not significantly contribute to TMP. Dissolved methane oversaturation persisted without high TMP, implying that methanogenesis in the biofilm, rather than high TMP, was the primary driving force in methane oversaturation. The results describe an attractive operational strategy to improve treatment performance in low-temperature AnMBR by supporting syntrophy and methanogenesis in the membrane biofilm through controlled membrane fouling.

  10. Membrane biofilm development improves COD removal in anaerobic membrane bioreactor wastewater treatment

    PubMed Central

    Smith, Adam L; Skerlos, Steven J; Raskin, Lutgarde

    2015-01-01

    Membrane biofilm development was evaluated to improve psychrophilic (15°C) anaerobic membrane bioreactor (AnMBR) treatment of domestic wastewater. An AnMBR containing three replicate submerged membrane housings with separate permeate collection was operated at three levels of membrane fouling by independently controlling biogas sparging for each membrane unit. High membrane fouling significantly improved permeate quality, but resulted in dissolved methane in the permeate at a concentration two to three times the equilibrium concentration predicted by Henry’s law. Illumina sequencing of 16S rRNA targeting Bacteria and Archaea and reverse transcription-quantitative polymerase chain reaction targeting the methyl coenzyme-M reductase (mcrA) gene in methanogens indicated that the membrane biofilm was enriched in highly active methanogens and syntrophic bacteria. Restoring fouled membranes to a transmembrane pressure (TMP) near zero by increasing biogas sparging did not disrupt the biofilm’s treatment performance, suggesting that microbes in the foulant layer were tightly adhered and did not significantly contribute to TMP. Dissolved methane oversaturation persisted without high TMP, implying that methanogenesis in the biofilm, rather than high TMP, was the primary driving force in methane oversaturation. The results describe an attractive operational strategy to improve treatment performance in low-temperature AnMBR by supporting syntrophy and methanogenesis in the membrane biofilm through controlled membrane fouling. PMID:26238293

  11. Two-step upflow anaerobic sludge bed system for sewage treatment under subtropical conditions with posttreatment in waste stabilization ponds.

    PubMed

    Seghezzo, Lucas; Trupiano, Aníbal P; Liberal, Viviana; Todd, Patrick G; Figueroa, María E; Gutiérrez, Marcelo A; Da Silva Wilches, Ana C; Iribarnegaray, Martín; Guerra, Raquel G; Arena, Angélica; Cuevas, Carlos M; Zeeman, Grietje; Lettinga, Gatze

    2003-01-01

    A pilot-scale sewage treatment system consisting of two upflow anaerobic sludge bed (UASB) reactors followed by five waste stabilization ponds (WSPs) in series was studied under subtropical conditions. The first UASB reactor started up in only 1 mo (stable operation, high chemical oxygen demand [COD] removal efficiency, low volatile fatty acids concentration in the effluent, alkalinity ratio above 0.7, biogas production above 0.1 Nm3/kg of CODremoved). Removal efficiencies up to 90% were obtained in the anaerobic steps at a hydraulic retention time of 6 + 4 h (80% removal in the first step). Fecal coliform removal in the whole system was 99.9999% (99.94% in anaerobic steps and 99.98% in WSPs). COD balances over UASB reactors are provided. A minimum set of data necessary to build COD balances is proposed. Intermittent sludge washout was detected in the reactors with the COD balances. Sludge washout from single-step UASB reactors should be monitored and minimized in order to ensure constant compliance with discharge standards, especially when no posttreatment is provided. The system combined high COD and fecal coliform removal efficiency with an extremely low effluent concentration, complying with discharge standards, and making it an attractive option for sewage treatment in subtropical regions.

  12. Improving methane production and anaerobic digestion stability of food waste by extracting lipids and mixing it with sewage sludge.

    PubMed

    Algapani, Dalal E; Wang, Jing; Qiao, Wei; Su, Min; Goglio, Andrea; Wandera, Simon M; Jiang, Mengmeng; Pan, Xiang; Adani, Fabrizio; Dong, Renjie

    2017-11-01

    Anaerobic digestion (AD) of FW shows instability due to both the presence of high lipids and accumulation of volatile fatty acids. In this study, AD of food waste (FW) was optimized by removing lipids (LRFW) and by co-digestion with sewage sludge (1:1w/w on dry matter). The results obtained showed that lipids extraction increased FW methane yield from 400 to 418mL-gVSadded(-1) under mesophilic conditions (35°C) and from 426 to 531mL-gVSadded(-1) in thermophilic conditions (55°C). Two degradation phases (k1 and k2) described FW and LRFW degradation. In the thermophilic, LRFW-k1 (0.1591d(-1)) was slightly higher than that of FW (k1 of 0.1543d(-1)) and in the second stage FW-k2 of 0.0552d(-1) was higher than that of LRFW (k2 of 0.0117d(-1)). The majority of LRFW was degraded in the first stage. FW and sewage sludge co-digestion reduced VFA accumulation, preventing media acidification and improving process stability. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Gaseous elemental mercury emissions and CO(2) respiration rates in terrestrial soils under controlled aerobic and anaerobic laboratory conditions.

    PubMed

    Obrist, Daniel; Faïn, Xavier; Berger, Carsen

    2010-03-01

    Mercury (Hg) levels in terrestrial soils are linked to the presence of organic carbon (C). Carbon pools are highly dynamic and subject to mineralization processes, but little is known about the fate of Hg during decomposition. This study evaluated relationships between gaseous Hg emissions from soils and carbon dioxide (CO(2)) respiration under controlled laboratory conditions to assess potential losses of Hg to the atmosphere during C mineralization. Results showed a linear correlation (r(2)=0.49) between Hg and CO(2) emissions in 41 soil samples, an effect unlikely to be caused by temperature, radiation, different Hg contents, or soil moisture. Stoichiometric comparisons of Hg/C ratios of emissions and underlying soil substrates suggest that 3% of soil Hg was subject to evasion. Even minute emissions of Hg upon mineralization, however, may be important on a global scale given the large Hg pools sequestered in terrestrial soils and C stocks. We induced changes in CO(2) respiration rates and observed Hg flux responses, including inducement of anaerobic conditions by changing chamber air supply from N(2)/O(2) (80% and 20%, respectively) to pure N(2). Unexpectedly, Hg emissions almost quadrupled after O(2) deprivation while oxidative mineralization (i.e., CO(2) emissions) was greatly reduced. This Hg flux response to anaerobic conditions was lacking when repeated with sterilized soils, possibly due to involvement of microbial reduction of Hg(2+) by anaerobes or indirect abiotic effects such as alterations in soil redox conditions. This study provides experimental evidence that Hg volatilization, and possibly Hg(2+) reduction, is related to O(2) availability in soils from two Sierra Nevada forests. If this result is confirmed in soils from other areas, the implication is that Hg volatilization from terrestrial soils is partially controlled by soil aeration and that low soil O(2) levels and possibly low soil redox potentials lead to increased Hg volatilization from

  14. Factors Affecting Cis-Dichloroethene and Vinyl Chloride Biological Transformation Under Anaerobic Conditions

    DTIC Science & Technology

    2006-05-01

    the Department of Defense Strategic Environmental Research and Development Program (SERDP). The publication of this report does not indicate...ethene. Therefore, overall objectives of this project have been: • To develop a better understanding of the microorganisms, enzymes, and mechanisms...involved in anaerobic reduction of cDCE and VC, and to develop molecular probes for monitoring these processes, • To determine the kinetics involved in

  15. Inactivation of Ascaris suum and poliovirus in biosolids under thermophilic anaerobic digestion conditions.

    PubMed

    Aitken, Michael D; Sobsey, Mark D; Blauth, Kimberly E; Shehee, Mina; Crunk, Phillip L; Walters, Glenn W

    2005-08-01

    There is considerable interest in the United States in production of Class A (low pathogen content) biosolids from the treatment of municipal wastewater sludge. Current requirements imposed by the U.S. Environmental Protection Agency make it difficult for thermophilic anaerobic digestion, in its simplest process configurations, to achieve Class A status. In particular, the time-temperature requirements necessitate long batch treatment times at temperatures associated with thermophilic anaerobic digestion. The time-temperature requirements are meant to ensure extensive inactivation of helminth eggs and enteric viruses, considered to be the most heat-resistant of the relevant pathogen classes. However, data on inactivation kinetics of these pathogens at precisely controlled and well-characterized temperatures are scarce. We measured inactivation of vaccine-strain poliovirus and eggs from the helminth Ascaris suum at temperatures from 49 to 55 degrees C in a lab-scale batch reactor containing biosolids from a continuous-flow thermophilic anaerobic digester. Both microbes were inactivated rapidly, with Ascaris more resistant to inactivation than poliovirus, and the relationships between inactivation rate and temperature were steep. The Arrhenius correlation between inactivation rate and temperature over the range 49-53 degrees C is consistent with protein denaturation as the inactivation mechanism for both microbes. The least stringent of the EPA time-temperature equations for thermal processes requires batch treatment times more than 2 orders of magnitude greater than would be required for three-log reduction of Ascaris at the rates we measured, suggesting an overly conservative regulatory approach. Such a grossly conservative approach can hinder full-scale implementation of thermophilic anaerobic digestion.

  16. Toxicity and biodegradability of selected N-substituted phenols under anaerobic conditions

    SciTech Connect

    Donlon, B.; Razo-Flores, E.; Hwu, C.S.; Field, J.; Lettinga, G.

    1995-12-31

    The anaerobic toxicity and biodegradability of N-substituted aromatics were evaluated in order to obtain information on their ultimate biotreatment. The toxicity of selected N-substituted aromatic compounds toward acetoclastic methanogens in granular sludge was measured in batch assays. This toxicity was highly correlated with compound hydrophobicity, indicating that partitioning into the bacterial membranes was an important factor in the toxicity. However, other factors, such as chemical interactions with key cell components, were suggested to be playing an important role. Nitroaromatic compounds were, on the average, over 300-fold more toxic than their amino-substituted counterparts. This finding suggests that the facile reduction of nitro-groups known to occur in anaerobic environments would result in a high level of detoxification. To test this hypothesis, continuous lab-scale upward-flow anaerobic sludge bed reactors treating 2-nitrophenol and 4-nitrophenol were established. The 4-nitrophenol was readily converted to the corresponding 4-aminophenol, whereas complete mineralization of 2-nitrophenol via intermediate formation of 2-aminophenol was obtained. These conversions led to a dramatic detoxification of the nitrophenols, because it was feasible to treat the highly toxic nitrophenolics at high organic loading rates.

  17. Creatine supplementation improves the anaerobic performance of elite junior fin swimmers.

    PubMed

    Juhász, Imre; Györe, I; Csende, Zs; Rácz, L; Tihanyi, J

    2009-09-01

    The objective of this study was to determine whether creatine supplementation (CrS) could improve mechanical power output, and swimming performance in highly trained junior competitive fin swimmers. Sixteen male fin swimmers (age:15.9+/-1.6 years) were randomly and evenly assigned to either a creatine (CR, 4x5 g/day creatine monohydrate for 5 days) or placebo group (P, same dose of a dextrose-ascorbic acid placebo) in a double-blind research. Before and after CrS the average power output was determined by a Bosco-test and the swimming time was measured in two maximal 100 m fin swims. After five days of CrS the average power of one minute continuous rebound jumps increased by 20.2%. The lactate concentration was significantly less after 5 minutes restitution at the second measurement in both groups. The swimming time was significantly reduced in both first (pre: 50.69+/-1.41 s; post: 48.86+/-1.34 s) and second (pre: 50.39+/-1.38 s; post: 48.53+/-1.35 s) sessions of swimming in CR group, but remained almost unchanged in the P group.The results of this study indicate that five day Cr supplementation enhances the dynamic strength and may increase anaerobic metabolism in the lower extremity muscles, and improves performance in consecutive maximal swims in highly trained adolescent fin swimmers.

  18. A study of two-stage anaerobic digestion of solid potato waste using reactors under mesophilic and thermophilic conditions.

    PubMed

    Parawira, W; Murto, M; Read, J S; Mattiasson, B

    2007-11-01

    A two-stage anaerobic digestion process operated under mesophilic and thermophilic conditions was investigated for the treatment of solid potato waste to determine optimal methane yield, efficiency of operation and process stability. A solid-bed reactor was used for hydrolysis/acidification stage while an upflow anaerobic sludge blanket (UASB) reactor was used in the second stage, for methanogenesis. Three sets of conditions were investigated: (1) mesophilic + mesophilic, (II) mesophilic + thermophilic and (III) thermophilic + thermophilic in the hydrolysis/acidification and methanogenesis reactors, respectively. The methane yield was higher under mesophilic conditions (0.49 l CH4 g COD(-1)degraded) than thermophilic conditions (0.41 l CH4 g COD(-1)degraded) with reference to the methanogenic reactors. (COD)--chemical oxygen demand. However, the digestion period was shorter in systems II and III than in system I. Also, in system III the UASB reactor (thermophilic conditions) could handle a higher organic loading rate (OLR) (36 g COD 1(-1)d(-1)) than in system I (11 g COD 1(-1)d(-1)) (mesophilic conditions) with stable operation. Higher OLRs in the methanogenic reactors resulted in reactor failure due to increasing total volatile fatty acid levels. In all systems, the concentration of propionate was one of the highest, higher than acetic acid, among the volatile fatty acids in the effluent. The results show the feasibility of using a two-stage system to treat solid potato waste under both mesophilic and thermophilic conditions. If the aim is to treat solid potato waste completely within a short period of time thermophilic conditions are to be preferred, but to obtain higher methane yield mesophilic conditions are preferable and therefore there is a need to balance methane yield and complete digestion period when dealing with large quantities of solid potato waste.

  19. Anaerobic digestion of post-hydrothermal liquefaction wastewater for improved energy efficiency of hydrothermal bioenergy processes.

    PubMed

    Zhou, Yan; Schideman, Lance; Zheng, Mingxia; Martin-Ryals, Ana; Li, Peng; Tommaso, Giovana; Zhang, Yuanhui

    2015-01-01

    Hydrothermal liquefaction (HTL) is a promising process for converting wet biomass and organic wastes into bio-crude oil. It also produces an aqueous product referred to as post-hydrothermal liquefaction wastewater (PHWW) containing up to 40% of the original feedstock carbon, which reduces the overall energy efficiency of the HTL process. This study investigated the feasibility of using anaerobic digestion (AD) to treat PHWW, with the aid of activated carbon. Results showed that successful AD occurred at relatively low concentrations of PHWW (≤ 6.7%), producing a biogas yield of 0.5 ml/mg CODremoved, and ∼53% energy recovery efficiency. Higher concentrations of PHWW (≥13.3%) had an inhibitory effect on the AD process, as indicated by delayed, slower, or no biogas production. Activated carbon was shown to effectively mitigate this inhibitory effect by enhancing biogas production and allowing digestion to proceed at higher PHWW concentrations (up to 33.3%), likely due to sequestering toxic organic compounds. The addition of activated carbon also increased the net energy recovery efficiency of AD with a relatively high concentration of PHWW (33.3%), taking into account the energy for producing activated carbon. These results suggest that AD is a feasible approach to treat PHWW, and to improve the energy efficiency of the HTL processes.

  20. Removal of nutrients from undiluted anaerobically treated piggery wastewater by improved microalgae.

    PubMed

    Wang, Mingzi; Yang, Yi; Chen, Zhihong; Chen, Yanzhen; Wen, Yangmin; Chen, Bilian

    2016-12-01

    This study aimed at improving the adaptability and biodegradability of tested microalgae in undiluted anaerobic fermentation slurry of piggery wastewater. For that, a two-stage method based on UV irradiation followed by gradual domestication was developed. The distinctness of this method was the elimination of a screening procedure and just needed the UV-irradiated cells with appropriate survival to be subjected to gradual domestication. The microalgae treated with the method not only grew well in undiluted slurry, but achieved outstanding removal efficiencies in total nitrogen (TN) and total phosphorus (TP). Large-scale application was conducted in an open raceway pond, and the concentrations of TN and TP after treatment were 43.80mg/L (removal rate of 89.5%) and 5.83mg/L (removal rate of 85.3%) respectively, which greatly excelled the Chinese discharge standards for livestock and poultry wastewater. The strategy is therefore a promising method for microalgae to purify piggery slurry containing high nutrient contents. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Improvement of COD removal by controlling the substrate degradability during the anaerobic digestion of recalcitrant wastewater.

    PubMed

    Kawai, Minako; Nagao, Norio; Kawasaki, Nobuyuki; Imai, Akio; Toda, Tatsuki

    2016-10-01

    The recalcitrant landfill leachate was anaerobically digested at various mixing ratios with labile synthetic wastewater to evaluate the degradation properties of recalcitrant wastewater. The proportion of leachate to the digestion system was increased in three equal steps, starting from 0% to 100%, and later decreased back to 0% with the same steps. The chemical oxygen demand (COD) for organic carbon and other components were calculated by analyzing the COD and dissolved organic carbon (DOC), and the removal efficiencies of COD carbon and COD others were evaluated separately. The degradation properties of COD carbon and COD others shifted owing to changing of substrate degradability, and the removal efficiencies of COD carbon and COD others were improved after supplying 100% recalcitrant wastewater. The UV absorptive property and total organic carbon (TOC) of each molecular size using high performance liquid chromatography (HPLC)-size exclusion chromatography (SEC) with UVA and TOC detectors were also investigated, and the degradability of different molecular sizes was determined. Although the SEC system detected extracellular polymeric substances (EPS), which are produced by microbes in stressful environments, during early stages of the experiment, EPS were not detected after feeding 100% recalcitrant wastewater. These results suggest that the microbes had acclimatized to the recalcitrant wastewater degradation. The high removal rates of both COD carbon and COD others were sustained when the proportion of labile wastewater in the substrate was 33%, indicating that the effective removal of recalcitrant COD might be controlled by changing the substrate's degradability.

  2. Investigations Into Improving Dewaterability at a Bio-P/Anaerobic Digestion Plant.

    PubMed

    Alm, Rebecca; Sealock, Adam W; Nollet, Yabing; Sprouse, George

    2016-01-08

    Metropolitan Council Environmental Services has observed poorer than expected dewatering performance at its Empire Plant. This plant has both anaerobic digestion and enhanced biological phosphorus removal in its treatment train. A research program using pilot scale anaerobic digesters, investigated potential solutions to the plant's poor dewaterability. The dewaterability goal was to increase the cake solids from 12% total solids (TS) to 16%TS, or higher.

  3. Macroscopic mass and energy balance of a pilot plant anaerobic bioreactor operated under thermophilic conditions.

    PubMed

    Espinosa-Solares, Teodoro; Bombardiere, John; Chatfield, Mark; Domaschko, Max; Easter, Michael; Stafford, David A; Castillo-Angeles, Saul; Castellanos-Hernandez, Nehemias

    2006-01-01

    Intensive poultry production generates over 100,000 t of litter annually in West Virginia and 9 x 10(6) t nationwide. Current available technological alternatives based on thermophilic anaerobic digestion for residuals treatment are diverse. A modification of the typical continuous stirred tank reactor is a promising process being relatively stable and owing to its capability to manage considerable amounts of residuals at low operational cost. A 40-m3 pilot plant digester was used for performance evaluation considering energy input and methane production. Results suggest some changes to the pilot plant configuration are necessary to reduce power consumption although maximizing biodigester performance.

  4. Organic intermediates in the anaerobic biodegradation of coal to methane under laboratory conditions

    USGS Publications Warehouse

    Orem, W.H.; Voytek, M.A.; Jones, E.J.; Lerch, H.E.; Bates, A.L.; Corum, M.D.; Warwick, P.D.; Clark, A.C.

    2010-01-01

    Organic intermediates in coal fluids produced by anaerobic biodegradation of geopolymers in coal play a key role in the production of methane in natural gas reservoirs. Laboratory biodegradation experiments on sub-bituminous coal from Texas, USA, were conducted using bioreactors to examine the organic intermediates relevant to methane production. Production of methane in the bioreactors was linked to acetate accumulation in bioreactor fluid. Long chain fatty acids, alkanes (C19-C36) and various low molecular weight aromatics, including phenols, also accumulated in the bioreactor fluid and appear to be the primary intermediates in the biodegradation pathway from coal-derived geopolymers to acetate and methane. ?? 2010.

  5. Efficacy of a Ventilatory Training Mask to Improve Anaerobic and Aerobic Capacity in Reserve Officers' Training Corps Cadets.

    PubMed

    Sellers, John H; Monaghan, Taylor P; Schnaiter, Jessica A; Jacobson, Bert H; Pope, Zachary K

    2016-04-01

    The purpose of this study was to examine the efficacy of a ventilatory training mask to improve anaerobic and aerobic fitness in reserve officers' training corps (ROTC) cadets. Seventeen ROTC cadets from a Midwest university completed pre- and postassessments consisting of anthropometry, a 30-second Wingate Anaerobic Test (WAnT), and a maximal aerobic capacity test (V[Combining Dot Above]O2max). A 6-week intervention training period was used during which time participants completed their mandatory physical training (PT) sessions. Participants were randomly assigned to either the experimental group (MASK; n = 9) or the control group (CON; n = 8). The ventilatory training masks were adjusted to simulate an altitude of 2,750 m. There was no significant effect (p ≤ 0.05) between groups on fatigue index, anaerobic capacity, peak power, V[Combining Dot Above]O2max, or time to exhaustion. These results suggest that the use of the ventilatory training mask during mandatory PT did not elicit superior aerobic or anaerobic adaptations in ROTC cadets. Therefore, it is recommended that more established simulated altitude training methods be used when incorporating intermittent hypoxic training.

  6. Pretreatment of sludge with microwaves for pathogen destruction and improved anaerobic digestion performance.

    PubMed

    Hong, Seung M; Park, Jae K; Teeradej, N; Lee, Y O; Cho, Y K; Park, C H

    2006-01-01

    A new way of generating Class A sludge using microwaves was evaluated through a series of laboratory-scale experiments. Microwaves provide rapid and uniform heating throughout the material. Other benefits of microwave treatment include instant and accurate control and selective and concentrated heating on materials, such as sludge, that have a high dielectric loss factor. Sludge was irradiated with 2450-MHz microwaves, and fecal coliforms were counted. Fecal coliforms were not detected at 65 degrees C for primary sludge and anaerobic digester sludge and at 85 degrees C for waste activated sludge when sludge was irradiated with 2450-MHz microwaves. During the bench-scale anaerobic digester operation, the highest average log reduction of fecal coliforms was achieved by the anaerobic digester fed with microwave-pretreated sludge (> or = 2.66 log removal). The anaerobic digester fed with microwave-irradiated sludge was more efficient in inactivation of fecal coliforms than the other two digesters fed with raw sludge and externally heated sludge, respectively. It took more than three hydraulic retention times for a bench-scale mesophilic anaerobic digester to meet Class A sludge requirements after feeding microwave-irradiated sludge. Class A sludge can be produced consistently with a continuously fed mesophilic anaerobic digester if sludge is pretreated with microwaves to reach 65 degrees C.

  7. EFFECT OF MUSIC ON ANAEROBIC EXERCISE PERFORMANCE

    PubMed Central

    2013-01-01

    For years, mostly the effects of music on cardiorespiratory exercise performance have been studied, but a few studies have examined the effect of music on anaerobic exercise. The purpose of this study was to assess the effect of listening to music and its rhythm on anaerobic exercise: on power output, heart rate and the concentration of blood lactate. 28 male subjects were required to visit the laboratory on 6 occasions, each separated by 48 hours. Firstly, each subject performed the Running-based Anaerobic Sprint Test (RAST) under 3 conditions on separate days: while listening to “slow rhythm music”, “fast rhythm music” or “no music”. 48 hours after the subjects completed RAST under 3 conditions, Wingate Anaerobic Power (WAN) tests were performed under 3 music conditions. The order of the 3 conditions (slow music, fast music and no music) was selected randomly to prevent an order effect. Results showed no significant differences between 3 conditions in anaerobic power assessments, heart rate or blood lactate (p > 0.05). On the basis of these results it can be said that music cannot improve anaerobic performance. The type of music had no impact on power outputs during RAST and WAN exercise. As a conclusion, listening to music and its rhythm cannot enhance anaerobic performance and cannot change the physiological response to supramaximal exercise. PMID:24744463

  8. Increased temperature in the thermophilic stage in temperature phased anaerobic digestion (TPAD) improves degradability of waste activated sludge.

    PubMed

    Ge, Huoqing; Jensen, Paul D; Batstone, Damien J

    2011-03-15

    Two-stage temperature phased anaerobic digestion (TPAD) is an increasingly popular method to improve stabilisation of sewage waste activated sludge, which normally has inherently poor and slow degradation. However, there has been limited systematic analysis of the impact of the initial thermophilic stage (temperature, pH and retention time) on performance in the main mesophilic stage. In this study, we demonstrate a novel two-stage batch test method for TPAD processes, and use it to optimize operating conditions of the thermophilic stage in terms of degradation extent and methane production. The method determines overall degradability and apparent hydrolysis coefficient in both stages. The overall process was more effective with short pre-treatment retention times (1-2 days) and neutral pH compared to longer retention time (4 days) and low pH (4-5). Degradabilities and apparent hydrolysis coefficients were 0.3-0.5 (fraction degradable) and 0.1-0.4d(-1), respectively, with a margin of error in each measurement of approximately 20% relative (95% confidence). Pre-treatment temperature had a strong impact on the whole process, increasing overall degradability from 0.3 to 0.5 as temperature increased from 50 to 65 °C, with apparent hydrolysis coefficient increasing from 0.1 to 0.4d(-1).

  9. Optimization of microwave pretreatment conditions to maximize methane production and methane yield in mesophilic anaerobic sludge digestion.

    PubMed

    Park, W J; Ahn, J H

    2011-10-01

    The objective of this study was to find optimum microwave pretreatment conditions for methane production and methane yield in anaerobic sludge digestion. The sludge was pretreated using a laboratory-scale industrial microwave unit (2450 MHz frequency). Microwave temperature increase rate (TIR) (2.9-17.1 degrees C/min) and final temperature (FT) (52-108 degrees C) significantly affected solubilization, methane production, and methane yield. Solubilization degree (soluble chemical oxygen demand (COD)/total COD) in the pretreated sludge (3.3-14.7%) was clearly higher than that in the raw sludge (2.6%). Within the design boundaries, the optimum conditions for maximum methane production (2.02 L/L) were TIR = 9.1 degrees C/min and FT = 90 degrees C, and the optimum conditions for maximum methane yield (809 mL/g VS(removed)) were TIR 7.1 degrees C/min and FT = 92 degrees C.

  10. Degradation of glycol based aircraft deicing fluids under anaerobic methanogenic conditions

    NASA Astrophysics Data System (ADS)

    Veltman, Shawn Herbert

    2000-11-01

    Large quantities of aircraft deicing fluid (ADF) comprised mainly of ethylene glycol (EG) and propylene glycol (PG) are used for aircraft deicing/anti-icing during cold weather operations at airports throughout the world. Several different formulations of ADF have been developed and are used. Type I solutions are commonly employed to remove snow and ice from aircraft surfaces (deicing), and Type IV solutions are commonly applied to prevent ice from reforming (anti-icing). The runoff from aircraft deicing operations is known to have a high oxygen demand. As a consequence, deicing wastes are often collected at airports for treatment. ADF products also contain small amounts of colorants, corrosion inhibitors, and thickeners, and these compounds may pose a greater environmental concern than oxygen depletion. Several studies have been completed to compare the relative toxicity of the pure glycols (EG and PG) vs. ADF using Microtox RTM assays and other aquatic tests, and it has been reported that ADF is significantly more inhibitory than the pure glycols. With growing concern over the environmental consequences of deicing there has been interest in developing anaerobic technology to treat deicing waste. In this dissertation a survey, a deicing waste characterization study, and research efforts employing serum bottles and bench scale laboratory reactors were used to demonstrate that ADF may be degraded effectively and efficiently in an anaerobic methanogenic environment. The factors that may affect this degradation are examined and discussed.

  11. Biotransformation of 2,4-dinitrotoluene by obligate marine Shewanella marisflavi EP1 under anaerobic conditions.

    PubMed

    Huang, Jiexun; Ning, Guojing; Li, Feili; Sheng, G Daniel

    2015-03-01

    Anaerobic transformation of 2,4-DNT by obligate marine Shewanella marisflavi EP1 was investigated. The cell growth of EP1 was proportional to the total amount of 2,4-DNT reduced. The eventual transformation product was 2,4-diaminotoluene, via 2-amino-4-nitrotoluene and 4-amino-2-nitrotoluene as intermediates. The presence of Cu(2+), dicumarol, metyrapone and flavins intensively influenced the reduction activity of 2,4-DNT, suggesting that dehydrogenease, menaquinone, cytochromes and flavins are essentially involved in electron transport process for 2,4-DNT reduction. These results indicate that biotransformation of 2,4-DNT by EP1 is a form of microbial anaerobic respiration. Furthermore, EP1 was capable of transforming 2,4-DNT at relatively alkaline range of pH (7-9), and at a wide range of temperature (4-40°C) and salinity (2-8% NaCl concentration). Our findings not only deepen our understanding of the environmental fate of 2,4-DNT, but also provide an extension to the application of shewanellae in the site bioremediation and/or wastewater treatment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Biofilm dynamics and kinetics during high-rate sulfurate reduction under anaerobic conditions

    SciTech Connect

    Nielsen, P.H.

    1987-01-01

    The sulfate kinetics in an anaerobic, sulfate-reducing biofilm were investigated with an annular biofilm reactor. Biofilm growth, sulfide production, and kinetic constants (K/sub m/ and V/sub max/) for the bacterial sulfate uptake within the biofilm were determined. These parameters were used to model the biofilm kinetics, and the experimental results were in good agreement with the model predictions. Typical zero-order volume rate constants for sulfate reduction in a biofilm without substrate limitation ranged from 56 to 93 ..mu..mol of SO/sub 4//sup 2 -/ cm/sup -3/ h/sup -1/ at 20/sup 0/C. The temperature dependence (Q/sub 10/) of sulfate reduction was equivalent to 3.4 at between 9 and 20/sup 0/C. The measured rates of sulfate reduction could explain the relatively high sulfide levels found in sewers and wastewater treatment systems. Furthermore, it has been shown that sulfate reduction in biofilms just a few hundred micrometers thick is limited by sulfate diffusion into biofilm at concentrations below 0.5 mM. This observation might, in some cases, be an explanation for the relatively poor capacity of the sulfate-reducing bacteria to compete with the methanogenic bacteria in anaerobic wastewater treatment in submerged filters.

  13. Strategies for changing temperature from mesophilic to thermophilic conditions in anaerobic CSTR reactors treating sewage sludge.

    PubMed

    Bousková, A; Dohányos, M; Schmidt, J E; Angelidaki, I

    2005-04-01

    Thermophilic anaerobic digestion presents an advantageous way for stabilization of sludge from wastewater treatment plants. Two different strategies for changing operational process temperature from mesophilic (37 degrees C) to thermophilic (55 degrees C) were tested using two continuous flow stirred tank reactors operated at constant organic loading rate of 1.38 g VS/l reactor/day and hydraulic retention time of 20 days. In reactor A, the temperature was increased step-wise: 37 degrees C-->42 degrees C-->47 degrees C-->51 degrees C-->55 degrees C. While in reactor B, the temperature was changed in one-step, from 37 degrees C to the desired temperature of 55 degrees C, The results showed that the overall adaptation of the process for the step-wise temperature increment took 70 days in total and a new change was applied when the process was stabilized as indicated by stable methane production and low volatile fatty acids concentrations. Although the one-step temperature increase caused a severe disturbance in all the process parameters, the system reached a new stable operation after only 30 days indicating that this strategy is the best in changing from mesophilic to thermophilic operation in anaerobic digestion plants.

  14. Anaerobic killing of mucoid Pseudomonas aeruginosa by acidified nitrite derivatives under cystic fibrosis airway conditions

    PubMed Central

    Yoon, Sang Sun; Coakley, Ray; Lau, Gee W.; Lymar, Sergei V.; Gaston, Benjamin; Karabulut, Ahmet C.; Hennigan, Robert F.; Hwang, Sung-Hei; Buettner, Garry; Schurr, Michael J.; Mortensen, Joel E.; Burns, Jane L.; Speert, David; Boucher, Richard C.; Hassett, Daniel J.

    2006-01-01

    Mucoid, mucA mutant Pseudomonas aeruginosa cause chronic lung infections in cystic fibrosis (CF) patients and are refractory to phagocytosis and antibiotics. Here we show that mucoid bacteria perish during anaerobic exposure to 15 mM nitrite (NO2–) at pH 6.5, which mimics CF airway mucus. Killing required a pH lower than 7, implicating formation of nitrous acid (HNO2) and NO, that adds NO equivalents to cellular molecules. Eighty-seven percent of CF isolates possessed mucA mutations and were killed by HNO2 (3-log reduction in 4 days). Furthermore, antibiotic-resistant strains determined were also equally sensitive to HNO2. More importantly, HNO2 killed mucoid bacteria (a) in anaerobic biofilms; (b) in vitro in ultrasupernatants of airway secretions derived from explanted CF patient lungs; and (c) in mouse lungs in vivo in a pH-dependent fashion, with no organisms remaining after daily exposure to HNO2 for 16 days. HNO2 at these levels of acidity and NO2– also had no adverse effects on cultured human airway epithelia in vitro. In summary, selective killing by HNO2 may provide novel insights into the important clinical goal of eradicating mucoid P. aeruginosa from the CF airways. PMID:16440061

  15. Tegoprens in anaerobic digestion of a mixture of cheese whey, poultry waste, and cattle dung for improved biomethanation

    SciTech Connect

    Patel, C.; Sastry, V.; Madamwar, D.

    1996-01-01

    To obtain enriched methane content and improve the anaerobic digestion of a mixture of cattle dung, poultry waste, and cheese whey, the effect of various doses of Tegoprens: T-3012, T-3099, T-5842, T-5843, T-5851, T-5852 has been studied, in bench-scale digesters. Among them, Tegoprens 3022 showed more than a 45% increase in gas production with higher methane content. 18 refs., 1 fig.

  16. Reorganization of the bacterial and archaeal populations associated with organic loading conditions in a thermophilic anaerobic digester.

    PubMed

    Hori, Tomoyuki; Haruta, Shin; Sasaki, Daisuke; Hanajima, Dai; Ueno, Yoshiyuki; Ogata, Atsushi; Ishii, Masaharu; Igarashi, Yasuo

    2015-03-01

    Organic loading conditions are an important factor influencing reactor performances in methanogenic bioreactors. Yet the underlying microbiological basis of the process stability, deterioration, and recovery remains to be understood. Here, structural responses of the bacterial and archaeal populations to the change of organic loading conditions in a thermophilic anaerobic digester were investigated by process analyses and 16S rRNA gene-based molecular approaches. The biogas was produced stably without the accumulation of volatile fatty acids (VFAs) at low organic loading rates (OLRs) in the beginning of reactor operation. Increasing OLR in stages disrupted the stable reactor performance, and high OLR conditions continued the deteriorated performance with slight biogas production and high accumulation of VFAs. Thereafter, the gradual decrease of OLR resulted in the recovery from the deterioration, giving rise to the stable performance again. The stable performances before and after the high OLR conditions conducted were associated with compositionally similar but not identical methanogenic consortia. The bacterial and archaeal populations were synchronously changed at both the transient phases toward the deteriorated performance and in recovery process, during which the dynamic shift of aceticlastic and hydrogenotrophic methanogens including the recently identified Methanomassiliicoccus might contribute to the maintenance of the methanogenic activity. The distinctive bacterial population with a high predominance of Methanobacterium formicicum as archaeal member was found for the deteriorated performance. The results in this study indicate the coordinated reorganization of the bacterial and archaeal populations in response to functional states induced by the change of organic loading conditions in the anaerobic digester. Copyright © 2014 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  17. Anaerobic-aerobic sequencing bioreactors improve energy efficiency for treatment of personal care product industry wastes.

    PubMed

    Ahammad, S Z; Bereslawski, J L; Dolfing, J; Mota, C; Graham, D W

    2013-07-01

    Personal care product (PCP) industry liquid wastes contain shampoo residues, which are usually treated by aerobic activated sludge (AS). Unfortunately, AS is expensive for PCP wastes because of high aeration and energy demands, whereas potentially energy-positive anaerobic designs cannot meet effluent targets. Therefore, combined anaerobic-aerobic systems may be the best solution. Seven treatment systems were assessed in terms of energy and treatment performance for shampoo wastes, including one aerobic, three anaerobic (HUASB, AHR and AnCSTR) and three anaerobic-aerobic reactor designs. COD removals were highest in the HUASB-aerobic (87.9 ± 0.4%) and AHR-aerobic (86.8±0.5%) systems, which used 69.2% and 62.5% less energy than aerobic AS. However, actual methane production rates were low relative to theoretical in the UASB and AHR units (∼10% methane/COD removed) compared with the AnCSTR unit (∼70%). Anaerobic-aerobic sequence reactors show promise for treating shampoo wastes, but optimal designs depend upon whether methane production or COD removal is most important to operations.

  18. Some Improvements in Signal-Conditioning Circuits

    NASA Technical Reports Server (NTRS)

    Shuler, Robert L.

    2004-01-01

    Two documents present wide-ranging discussions of some issues in the design and operation of signal-conditioning circuits. The first document focuses on active low-pass filter circuits that contain resistors, capacitors, and operational amplifiers. It describes design and operational problems encountered previously, deficiencies of prior designs, and four design improvements to overcome the deficiencies. These improvements are as follows: 1. An offset-calibration feature in which an electronic switch isolates a filter capacitor in order to preserve its voltage during a calibration performed to measure the offset voltage of the operational amplifier; 2. Configuring a pair of complementary operational amplifiers to prevent latchup and decrease the degree of nonlinearity in overall response; 3. Minimizing distortion by taking the filter output from the operational-amplifier output nodes instead of from one of the other nodes as in prior designs; and 4. Providing for switching different feedback resistors to change filter break frequencies. The second document addresses topics in the architecture of signal-conditioning and multiplexing circuitry. Improvements are described as being made with respect to greater compactness, increased flexibility in accommodating a variety of inputs, improvements in filter performance, simplification of wiring, and reconfigurability of designs.

  19. Enrichment of acetogenic bacteria in high rate anaerobic reactors under mesophilic and thermophilic conditions.

    PubMed

    Ryan, P; Forbes, C; McHugh, S; O'Reilly, C; Fleming, G T A; Colleran, E

    2010-07-01

    The objective of the current study was to expand the knowledge of the role of acetogenic Bacteria in high rate anaerobic digesters. To this end, acetogens were enriched by supplying a variety of acetogenic growth supportive substrates to two laboratory scale high rate upflow anaerobic sludge bed (UASB) reactors operated at 37 degrees C (R1) and 55 degrees C (R2). The reactors were initially fed a glucose/acetate influent. Having achieved high operational performance and granular sludge development and activity, both reactors were changed to homoacetogenic bacterial substrates on day 373 of the trial. The reactors were initially fed with sodium vanillate as a sole substrate. Although % COD removal indicated that the 55 degrees C reactor out performed the 37 degrees C reactor, effluent acetate levels from R2 were generally higher than from R1, reaching values as high as 5023 mg l(-1). Homoacetogenic activity in both reactors was confirmed on day 419 by specific acetogenic activity (SAA) measurement, with higher values obtained for R2 than R1. Sodium formate was introduced as sole substrate to both reactors on day 464. It was found that formate supported acetogenic activity at both temperatures. By the end of the trial, no specific methanogenic activity (SMA) was observed against acetate and propionate indicating that the methane produced was solely by hydrogenotrophic Archaea. Higher SMA and SAA values against H(2)/CO(2) suggested development of a formate utilising acetogenic population growing in syntrophy with hydrogenotrophic methanogens. Throughout the formate trial, the mesophilic reactor performed better overall than the thermophilic reactor.

  20. Survival of weed seeds and animal parasites as affected by anaerobic digestion at meso- and thermophilic conditions.

    PubMed

    Johansen, Anders; Nielsen, Henrik B; Hansen, Christian M; Andreasen, Christian; Carlsgart, Josefine; Hauggard-Nielsen, Henrik; Roepstorff, Allan

    2013-04-01

    Anaerobic digestion of residual materials from animals and crops offers an opportunity to simultaneously produce bioenergy and plant fertilizers at single farms and in farm communities where input substrate materials and resulting digested residues are shared among member farms. A surplus benefit from this practice may be the suppressing of propagules from harmful biological pests like weeds and animal pathogens (e.g. parasites). In the present work, batch experiments were performed, where survival of seeds of seven species of weeds and non-embryonated eggs of the large roundworm of pigs, Ascaris suum, was assessed under conditions similar to biogas plants managed at meso- (37°C) and thermophilic (55°C) conditions. Cattle manure was used as digestion substrate and experimental units were sampled destructively over time. Regarding weed seeds, the effect of thermophilic conditions (55°C) was very clear as complete mortality, irrespective of weed species, was reached after less than 2 days. At mesophilic conditions, seeds of Avena fatua, Sinapsis arvensis, Solidago canadensis had completely lost germination ability, while Brassica napus, Fallopia convolvulus and Amzinckia micrantha still maintained low levels (~1%) of germination ability after 1 week. Chenopodium album was the only weed species which survived 1 week at substantial levels (7%) although after 11 d germination ability was totally lost. Similarly, at 55°C, no Ascaris eggs survived more than 3h of incubation. Incubation at 37°C did not affect egg survival during the first 48 h and it took up to 10 days before total elimination was reached. In general, anaerobic digestion in biogas plants seems an efficient way (thermophilic more efficient than mesophilic) to treat organic farm wastes in a way that suppresses animal parasites and weeds so that the digestates can be applied without risking spread of these pests.

  1. Rhodobacter capsulatus Catalyzes Light-Dependent Fe(II) Oxidation under Anaerobic Conditions as a Potential Detoxification Mechanism▿

    PubMed Central

    Poulain, Alexandre J.; Newman, Dianne K.

    2009-01-01

    Diverse bacteria are known to oxidize millimolar concentrations of ferrous iron [Fe(II)] under anaerobic conditions, both phototrophically and chemotrophically. Yet whether they can do this under conditions that are relevant to natural systems is understood less well. In this study, we tested how light, Fe(II) speciation, pH, and salinity affected the rate of Fe(II) oxidation by Rhodobacter capsulatus SB1003. Although R. capsulatus cannot grow photoautotrophically on Fe(II), it oxidizes Fe(II) at rates comparable to those of bacteria that do grow photoautotrophically on Fe(II) as soon as it is exposed to light, provided it has a functional photosystem. Chelation of Fe(II) by diverse organic ligands promotes Fe(II) oxidation, and as the pH increases, so does the oxidation rate, except in the presence of nitrilotriacetate; nonchelated forms of Fe(II) are also more rapidly oxidized at higher pH. Salt concentrations typical of marine environments inhibit Fe(II) oxidation. When growing photoheterotrophically on humic substances, R. capsulatus is highly sensitive to low concentrations of Fe(II); it is inhibited in the presence of concentrations as low as 5 μM. The product of Fe(II) oxidation, ferric iron, does not hamper growth under these conditions. When other parameters, such as pH or the presence of chelators, are adjusted to promote Fe(II) oxidation, the growth inhibition effect of Fe(II) is alleviated. Together, these results suggest that Fe(II) is toxic to R. capsulatus growing under strictly anaerobic conditions and that Fe(II) oxidation alleviates this toxicity. PMID:19717624

  2. Enhancement of sludge anaerobic biodegradability by combined microwave-H2O2 pretreatment in acidic conditions.

    PubMed

    Eswari, Parvathy; Kavitha, S; Kaliappan, S; Yeom, Ick-Tae; Banu, J Rajesh

    2016-07-01

    The aim of this study was to increase the sludge disintegration and reduce the cost of microwave (MW) pretreatment. Thermodynamic analysis of MW hydrolysis revealed the best fit with a first-order kinetic model at a specific energy of 18,600 kJ/kg total solids (TS). Combining H2O2 with MW resulted in a significant increment in solubilization from 30 to 50 % at 18,600 kJ/kg TS. The pH of H2O2-assisted MW-pretreated sludge (MW + H2O2) was in the alkaline range (pH 9-10), and it made the sludge unfavorable for subsequent anaerobic digestion and inhibits methane production. In order to nullify the alkaline effect caused by the MW + H2O2 combination, the addition of acid was considered for pH adjustment. H2O2-assisted MW-pretreated sludge in acidic conditions (MW + H2O2 + acid) showed a maximum methane production of 323 mL/g volatile solids (VS) than others during anaerobic biodegradability. A cost analysis of this study reveals that MW + H2O2 + acid was the most economical method with a net profit of 59.90 €/t of sludge.

  3. Reactor performance of a 750 m(3) anaerobic digestion plant: varied substrate input conditions impacting methanogenic community.

    PubMed

    Wagner, Andreas Otto; Malin, Cornelia; Lins, Philipp; Gstraunthaler, Gudrun; Illmer, Paul

    2014-10-01

    A 750 m(3) anaerobic digester was studied over a half year period including a shift from good reactor performance to a reduced one. Various abiotic parameters like volatile fatty acids (VFA) (formic-, acetic-, propionic-, (iso-)butyric-, (iso-)valeric-, lactic acid), total C, total N, NH4 -N, and total proteins, as well as the organic matter content and dry mass were determined. In addition several process parameters such as temperature, pH, retention time and input of substrate and the concentrations of CH4, H2, CO2 and H2S within the reactor were monitored continuously. The present study aimed at the investigation of the abundance of acetogens and total cell numbers and the microbial methanogenic community as derived from PCR-dHPLC analysis in order to put it into context with the determined abiotic parameters. An influence of substrate quantity on the efficiency of the anaerobic digestion process was found as well as a shift from a hydrogenotrophic in times of good reactor performance towards an acetoclastic dominated methanogenic community in times of reduced reactor performance. After the change in substrate conditions it took the methano-archaeal community about 5-6 weeks to be affected but then changes occurred quickly.

  4. Improved azo dye decolorization in an advanced integrated system of bioelectrochemical module with surrounding electrode deployment and anaerobic sludge reactor.

    PubMed

    Kong, Fanying; Wang, Aijie; Ren, Hong-Yu

    2015-01-01

    A new integrated system, embedding a modular bioelectrochemical system (BES) with surrounding electrode deployment into an anaerobic sludge reactor (ASR), was developed to improve azo dye decolorization. Results demonstrated that the AO7 decolorization and COD removal can be improved without co-substrate in such system. The kinetic rate of decolorization (0.54h(-1)) in integrated system was 1.4-fold and 54.0-fold higher than that in biocathode BES (0.39h(-1)) and ASR (0.01h(-1)), respectively. COD can be removed after cleavage of azo bond, different from biocathode BES. The combined advantages of this integrated system were achieved by the cooperation of biocathode in modular BES and sludge in ASR. Biocathode was a predominant factor in AO7 decolorization, and anaerobic sludge contributed negligibly to AO7 reduction decolorization but mostly in the COD removal. These results demonstrated the great potential of integrating a BES module with anaerobic treatment process for azo dye treatment. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Potential of high-frequency ultrasounds to improve sludge anaerobic conversion and surfactants removal at different food/inoculum ratio.

    PubMed

    Gallipoli, A; Gianico, A; Gagliano, M C; Braguglia, C M

    2014-05-01

    High-frequency ultrasounds have recently gained interest as oxidative technique for sonochemical degradation of organic contaminants in water. In this study an innovative approach applying 200 kHz ultrasounds to improve both sludge anaerobic biodegradability and decontamination is proposed. Digestion tests were performed on batch reactors fed either with untreated or sonicated sludge, at different food/inoculum (F/I) ratio, in the range 0.3-0.9. First order kinetic highlighted a decreasing trend of the hydrolysis rate by increasing F/I, both for untreated and sonicated sludge. Positive effect of ultrasounds on specific biogas production was evident, but the conversion rate for pretreated sludge was strongly affected by F/I, and decreased by increasing F/I. Anionic surfactants anaerobic removal occurred in all tests, but the effect of ultrasounds was significant only at F/I=0.3. By pretreating sludge with high frequency ultrasounds, low F/I was the ideal ratio improving both sludge anaerobic digestion and decontamination.

  6. Characterization of anaerobic sulfite reduction by Salmonella typhimurium and purification of the anaerobically induced sulfite reductase

    SciTech Connect

    Hallenbeck, P.C. ); Clark, M.A.; Barrett, E.L. )

    1989-06-01

    Mutants of Salmonella typhimurium that lack the biosynthetic sulfite reductase (cysI and cysJ mutants) retain the ability to reduce sulfite for growth under anaerobic conditions. Here we report studies of sulfite reduction by a cysI mutant of S. typhimurium and purification of the associated anaerobic sulfite reductase. Sulfite reduction for anaerobic growth did not require a reducing atmosphere but was prevented by an argon atmosphere contaminated with air (<0.33%). It was also prevented by the presence of 0.1 mM nitrate. Anaerobic growth in liquid minimal medium, but not on agar, was found to require additions of trace amounts (10{sup {minus}7} M) of cysteine. Spontaneous mutants that grew under the argon contaminated with air also lost the requirement for 10{sup {minus}7}M cysteine for anaerobic growth in liquid. A role for sulfite reduction in anaerobic energy generation was contraindicated by the findings that sulfite reduction did not improve cell yields, and anaerobic sulfite reductase activity was greatest during the stationary phase of growth. Sulfite reductase was purified from the cytoplasmic fraction of the anaerobically grown cysI mutant and was purified 190-fold. The most effective donor in crude extracts was NADH. NADHP and methyl viologen were, respectively, 40 and 30% as effective as NADH. Oxygen reversibly inhibited the enzyme. The anaerobic sulfite reductase showed some resemblance to the biosynthetic sulfite reductase, but apparently it has a unique, as yet unidentified function.

  7. Model based evaluation of a contaminant plume development under aerobic and anaerobic conditions in 2D bench-scale tank experiments.

    PubMed

    Ballarini, E; Beyer, C; Bauer, R D; Griebler, C; Bauer, S

    2014-06-01

    The influence of transverse mixing on competitive aerobic and anaerobic biodegradation of a hydrocarbon plume was investigated using a two-dimensional, bench-scale flow-through laboratory tank experiment. In the first part of the experiment aerobic degradation of increasing toluene concentrations was carried out by the aerobic strain Pseudomonas putida F1. Successively, ethylbenzene (injected as a mixture of unlabeled and fully deuterium-labeled isotopologues) substituted toluene; nitrate was added as additional electron acceptor and the anaerobic denitrifying strain Aromatoleum aromaticum EbN1 was inoculated to study competitive degradation under aerobic /anaerobic conditions. The spatial distribution of anaerobic degradation was resolved by measurements of compound-specific stable isotope fractionation induced by the anaerobic strain as well as compound concentrations. A fully transient numerical reactive transport model was employed and calibrated using measurements of electron donors, acceptors and isotope fractionation. The aerobic phases of the experiment were successfully reproduced using a double Monod kinetic growth model and assuming an initial homogeneous distribution of P. putida F1. Investigation of the competitive degradation phase shows that the observed isotopic pattern cannot be explained by transverse mixing driven biodegradation only, but also depends on the inoculation process of the anaerobic strain. Transient concentrations of electron acceptors and donors are well reproduced by the model, showing its ability to simulate transient competitive biodegradation.

  8. Improving the cyanide toxicity tolerance of anaerobic reactor: Microbial interactions and toxin reduction.

    PubMed

    Gupta, Pragya; Ahammad, S Z; Sreekrishnan, T R

    2016-09-05

    Anaerobic biological treatment of high organics containing wastewater is amongst the preferred treatment options but poor tolerance to toxins makes its use prohibitive. In this study, efforts have been made to understand the key parameters for developing anaerobic reactor, resilient to cyanide toxicity. A laboratory scale anaerobic batch reactor was set up to treat cyanide containing wastewater. The reactor was inoculated with anaerobic sludge obtained from a wastewater treatment plant and fresh cow dung in the ratio of 3:1. The focus was on acclimatization and development of cyanide-degrading biomass and to understand the toxic effects of cyanide on the dynamic equilibrium between various microbial groups. The sludge exposed to cyanide was found to have higher bacterial diversity than the control. It was observed that certain hydrogenotrophic methanogens and bacterial groups were able to grow and produce methane in the presence of cyanide. Also, it was found that hydrogen utilizing methanogens were more cyanide tolerant than acetate utilizing methanogens. So, effluents from various industries like electroplating, coke oven plant, petroleum refining, explosive manufacturing, and pesticides industries which are having high concentrations of cyanide can be treated by favoring the growth of the tolerant microbes in the reactors. It will provide much better treatment efficiency by overcoming the inhibitory effects of cyanide to certain extent. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Improvement of anaerobic digester performance by wastewater recirculation through an aerated membrane.

    USDA-ARS?s Scientific Manuscript database

    Swine wastewater from an anaerobic digester was recirculated through a silicone hose located in an external aeration chamber to determine its effect on wastewater malodorants and biogas composition. The silicone hose acted as a semipermeable membrane for the passage of small molecules. In the first...

  10. The Effects of a Sport-Specific Maximal Strength and Conditioning Training on Critical Velocity, Anaerobic Running Distance, and 5-km Race Performance.

    PubMed

    Karsten, Bettina; Stevens, Liesbeth; Colpus, Mark; Larumbe-Zabala, Eneko; Naclerio, Fernando

    2016-01-01

    To investigate the effects of a sport-specific maximal 6-wk strength and conditioning program on critical velocity (CV), anaerobic running distance (ARD), and 5-km time-trial performance (TT). 16 moderately trained recreational endurance runners were tested for CV, ARD, and TT performances on 3 separate occasions (baseline, midstudy, and poststudy). Participants were randomly allocated into a strength and conditioning group (S&C; n = 8) and a comparison endurance-training-only group (EO; n = 8). During the first phase of the study (6 wk), the S&C group performed concurrent maximal strength and endurance training, while the EO group performed endurance-only training. After the retest of all variables (midstudy), both groups subsequently, during phase 2, performed another 6 wk of endurance-only training that was followed by poststudy tests. No significant change for CV was identified in either group. The S&C group demonstrated a significant decrease for ARD values after phases 1 and 2 of the study. TT performances were significantly different in the S&C group after the intervention, with a performance improvement of 3.62%. This performance increase returned close to baseline after the 6-wk endurance-only training. Combining a 6-wk resistance-training program with endurance training significantly improves 5-km TT performance. Removing strength training results in some loss of those performance improvements.

  11. Comparison of microbial communities during the anaerobic digestion of Gracilaria under mesophilic and thermophilic conditions.

    PubMed

    Azizi, Aqil; Kim, Wonduck; Lee, Jung Hyun

    2016-10-01

    Mesophilic and thermophilic anaerobic digesters (MD and TD, respectively) utilizing Gracilaria and marine sediment as the substrate and inoculum, respectively, were compared by analyzing their performances and microbial community changes. During three successive transfers, the average cumulative methane yields in the MD and TD were 222.6 ± 17.3 mL CH4/g volatile solids (VS) and 246.1 ± 11 mL CH4/g VS, respectively. The higher hydrolysis rate and acidogenesis in the TD resulted in a several fold greater accumulation of volatile fatty acids (acetate, propionate, and butyrate) followed by a larger pH drop with a prolonged recovery than in the MD. However, the operational stability between both digesters remained comparable. Pyrosequencing analyses revealed that the MD had more complex microbial diversity indices and microbial community changes than the TD. Interestingly, Methanomassiliicoccales, the seventh methanogen order was the predominant archaeal order in the MD along with bacterial orders of Clostridiales, Bacteriodales, and Synergistales. Meanwhile, Coprothermobacter and Methanobacteriales dominated the bacterial and archaeal community in the TD, respectively. Although the methane yield is comparable, both MD and TD show a different profile of pH, VFA and the microbial communities.

  12. Anaerobic digestion of pig and dairy manure under photo-dark fermentation condition.

    PubMed

    Yin, Dongxue; Liu, Wei; Zhai, Ningning; Yang, Gaihe; Wang, Xiaojiao; Feng, Yongzhong; Ren, Guangxin

    2014-08-01

    Anaerobic digestion (AD) with livestock manure is a promising way for biogas production. This work presents the influence of photo-dark fermentation on biogas production of pig manure (PM) and dairy manure (DM). All sets were conducted with temperature 35 ± 2 °C and total solid concentrations 8%: PM₁ and DM₁ in transparent reactor under sunlight for photo-dark fermentation, and PM₂ and DM₂ in non-transparent reactor for dark fermentation. DM₂ had the best cumulative biogas production (CBP) of 15,447.5 mL, followed by PM₁ (15,020 mL) with stable pH and low total ammonium nitrogen (TAN) concentration (1384.99 mg/L), and DM₁ and PM₂. The CBP of DM₂ was 5.77 times as much as PM₂. The relationship between CBP and four factors including volatile fatty acid (VFA), TAN, total alkalinity and pH was analyzed. pH gained the maximum determination coefficient with the CBP among all sets and total alkalinity showed negative correlation with CBP of PM₁ and DM₁.

  13. Wastewater sludges pretreated by different oxidation systems at mild conditions to promote the biogas formation in anaerobic processes.

    PubMed

    Segura, Y; Puyol, D; Ballesteros, L; Martínez, F; Melero, J A

    2016-12-01

    The effect of different oxidation processes at mild conditions including the coupled-Fenton (sono-Fenton, photo-Fenton, and sono-photo-Fenton) and their blank systems (ultrasound, ultraviolet, zero valent iron, and Fenton) on anaerobic digestion of the sludge for biogas production was investigated. Ultrasounds led to the highest organic matter solubilization (3.8 up to 5.2 g chemical oxygen demand (COD)/L, for the raw and treated sludge, respectively), while for the rest, organic matter transformation was observed resulting in an almost soluble COD net balance. Results indicated that for the most oxidative processes, the released organic matter was probably mineralized by the hydroxyl radicals produced during the treatments. It is interesting to remark that even if the biochemical methane potential was barely enhanced by the different methods applied, all the methods demonstrated to enhance the overall kinetics of the biomethanation processes, increasing the rapidly biodegradable fraction of the sludge.

  14. Partial degradation mechanisms of malachite green and methyl violet B by Shewanella decolorationis NTOU1 under anaerobic conditions.

    PubMed

    Chen, C-H; Chang, C-F; Liu, S-M

    2010-05-15

    This work demonstrated that Shewanella decolorationis NTOU1 decolorized 200 mg l(-1) of crystal violet, malachite green, or methyl violet B within 2-11h under anaerobic conditions at 35 degrees C. The initial color removal rate of malachite green was highest, while that of methyl violet was lowest. GC/MS analyses of the intermediate compounds produced during and after decolorization of malachite green and methyl violet B suggested that biodegradation of these dyes involved reduction to leuco form, N-demethylation, and reductive splitting of the triphenyl rings. The number of N-methylated groups of these dyes might have influenced decolorization rates and the reductive splitting of the triphenyl rings of these dyes. Cytotoxicity and antimicrobial test data showed that malachite green and methyl violet B solution (100 mg l(-1)) were toxic. Toxicity of the dyes decreased after their decolorization, but further incubation resulted in increased toxicity.

  15. Microcosm experiments to control anaerobic redox conditions when studying the fate of organic micropollutants in aquifer material

    NASA Astrophysics Data System (ADS)

    Barbieri, Manuela; Carrera, Jesús; Sanchez-Vila, Xavier; Ayora, Carlos; Cama, Jordi; Köck-Schulmeyer, Marianne; López de Alda, Miren; Barceló, Damià; Tobella Brunet, Joana; Hernández García, Marta

    2011-11-01

    The natural processes occurring in subsurface environments have proven to effectively remove a number of organic pollutants from water. The predominant redox conditions revealed to be one of the controlling factors. However, in the case of organic micropollutants the knowledge on this potential redox-dependent behavior is still limited. Motivated by managed aquifer recharge practices microcosm experiments involving aquifer material, settings potentially feasible in field applications, and organic micropollutants at environmental concentrations were carried out. Different anaerobic redox conditions were promoted and sustained in each set of microcosms by adding adequate quantities of electron donors and acceptors. Whereas denitrification and sulfate-reducing conditions are easily achieved and maintained, Fe- and Mn-reduction are strongly constrained by the slower dissolution of the solid phases commonly present in aquifers. The thorough description and numerical modeling of the evolution of the experiments, including major and trace solutes and dissolution/precipitation of solid phases, have been proven necessary to the understanding of the processes and closing the mass balance. As an example of micropollutant results, the ubiquitous beta-blocker atenolol is completely removed in the experiments, the removal occurring faster under more advanced redox conditions. This suggests that aquifers constitute a potentially efficient alternative water treatment for atenolol, especially if adequate redox conditions are promoted during recharge and long enough residence times are ensured.

  16. Serial completely stirred tank reactors for improving biogas production and substance degradation during anaerobic digestion of corn stover.

    PubMed

    Li, YuQian; Liu, ChunMei; Wachemo, Akiber Chufo; Yuan, HaiRong; Zou, DeXun; Liu, YanPing; Li, XiuJin

    2017-03-11

    Several completely stirred tank reactors (CSTR) connected in series for anaerobic digestion of corn stover were investigated in laboratory scale. Serial anaerobic digestion systems operated at a total HRT of 40days, and distribution of HRT are 10+30days (HRT10+30d), 20+20days (HRT20+20d), and 30+10days (HRT30+10d) were compared to a conventional one-step CSTR at the same HRT of 40d. The results showed that in HRT10+30d serial system, the process became very unstable at organic load of 50gTS·L(-1). The HRT20+20d and HRT30+10d serial systems improved methane production by 8.3-14.6% compared to the one-step system in all loads of 50, 70, 90gTS·L(-1). The conversion rates of total solid, cellulose, and hemicellulose were increased in serial anaerobic digestion systems compared to single system. The serial systems showed more stable process performance in high organic load. HRT30+10d system showed the best biogas production and conversions among all systems.

  17. Polyhydroxyalkanoates in waste activated sludge enhances anaerobic methane production through improving biochemical methane potential instead of hydrolysis rate.

    PubMed

    Wang, Qilin; Sun, Jing; Zhang, Chang; Xie, Guo-Jun; Zhou, Xu; Qian, Jin; Yang, Guojing; Zeng, Guangming; Liu, Yiqi; Wang, Dongbo

    2016-01-21

    Anaerobic sludge digestion is the main technology for sludge reduction and stabilization prior to sludge disposal. Nevertheless, methane production from anaerobic digestion of waste activated sludge (WAS) is often restricted by the poor biochemical methane potential and slow hydrolysis rate of WAS. This work systematically investigated the effect of PHA levels of WAS on anaerobic methane production, using both experimental and mathematical modeling approaches. Biochemical methane potential tests showed that methane production increased with increased PHA levels in WAS. Model-based analysis suggested that the PHA-based method enhanced methane production by improving biochemical methane potential of WAS, with the highest enhancement being around 40% (from 192 to 274 L CH4/kg VS added; VS: volatile solid) when the PHA levels increased from 21 to 143 mg/g VS. In contrast, the hydrolysis rate (approximately 0.10 d(-1)) was not significantly affected by the PHA levels. Economic analysis suggested that the PHA-based method could save $1.2/PE/y (PE: population equivalent) in a typical wastewater treatment plant (WWTP). The PHA-based method can be easily integrated into the current WWTP to enhance methane production, thereby providing a strong support to the on-going paradigm shift in wastewater management from pollutant removal to resource recovery.

  18. Polyhydroxyalkanoates in waste activated sludge enhances anaerobic methane production through improving biochemical methane potential instead of hydrolysis rate

    NASA Astrophysics Data System (ADS)

    Wang, Qilin; Sun, Jing; Zhang, Chang; Xie, Guo-Jun; Zhou, Xu; Qian, Jin; Yang, Guojing; Zeng, Guangming; Liu, Yiqi; Wang, Dongbo

    2016-01-01

    Anaerobic sludge digestion is the main technology for sludge reduction and stabilization prior to sludge disposal. Nevertheless, methane production from anaerobic digestion of waste activated sludge (WAS) is often restricted by the poor biochemical methane potential and slow hydrolysis rate of WAS. This work systematically investigated the effect of PHA levels of WAS on anaerobic methane production, using both experimental and mathematical modeling approaches. Biochemical methane potential tests showed that methane production increased with increased PHA levels in WAS. Model-based analysis suggested that the PHA-based method enhanced methane production by improving biochemical methane potential of WAS, with the highest enhancement being around 40% (from 192 to 274 L CH4/kg VS added; VS: volatile solid) when the PHA levels increased from 21 to 143 mg/g VS. In contrast, the hydrolysis rate (approximately 0.10 d-1) was not significantly affected by the PHA levels. Economic analysis suggested that the PHA-based method could save $1.2/PE/y (PE: population equivalent) in a typical wastewater treatment plant (WWTP). The PHA-based method can be easily integrated into the current WWTP to enhance methane production, thereby providing a strong support to the on-going paradigm shift in wastewater management from pollutant removal to resource recovery.

  19. Polyhydroxyalkanoates in waste activated sludge enhances anaerobic methane production through improving biochemical methane potential instead of hydrolysis rate

    PubMed Central

    Wang, Qilin; Sun, Jing; Zhang, Chang; Xie, Guo-Jun; Zhou, Xu; Qian, Jin; Yang, Guojing; Zeng, Guangming; Liu, Yiqi; Wang, Dongbo

    2016-01-01

    Anaerobic sludge digestion is the main technology for sludge reduction and stabilization prior to sludge disposal. Nevertheless, methane production from anaerobic digestion of waste activated sludge (WAS) is often restricted by the poor biochemical methane potential and slow hydrolysis rate of WAS. This work systematically investigated the effect of PHA levels of WAS on anaerobic methane production, using both experimental and mathematical modeling approaches. Biochemical methane potential tests showed that methane production increased with increased PHA levels in WAS. Model-based analysis suggested that the PHA-based method enhanced methane production by improving biochemical methane potential of WAS, with the highest enhancement being around 40% (from 192 to 274 L CH4/kg VS added; VS: volatile solid) when the PHA levels increased from 21 to 143 mg/g VS. In contrast, the hydrolysis rate (approximately 0.10 d−1) was not significantly affected by the PHA levels. Economic analysis suggested that the PHA-based method could save $1.2/PE/y (PE: population equivalent) in a typical wastewater treatment plant (WWTP). The PHA-based method can be easily integrated into the current WWTP to enhance methane production, thereby providing a strong support to the on-going paradigm shift in wastewater management from pollutant removal to resource recovery. PMID:26791952

  20. Adsorption of heavy metals on to sugar cane bagasse: improvement of adsorption capacities due to anaerobic degradation of the biosorbent.

    PubMed

    Joseph, Osnick; Rouez, Maxime; Métivier-Pignon, Hélène; Bayard, Rémy; Emmanuel, Evens; Gourdon, Rémy

    2009-12-01

    In this work, anaerobic degradation of sugar cane bagasse was studied with a dual objective: the production of biogas and the improvement of the material's characteristics for its implementation in adsorption processes. The biogas production was determined by means of biomethane potential tests carried out over two months of incubation at 35 degrees C. Biogas and methane cumulative productions were assumed to follow a first-order rate of decay. Theoretical cumulative methane and biogas productions were calculated using Buswell's equation. The anaerobic digestion resulted in a 92% decrease in the leachable organic fraction and a 40% mass loss of bagasse. The average productions of biogas and methane from the whole set of experiments were 293 +/- 6 and 122 +/- 4 mL g(-1) of volatile solids, respectively. The anaerobic incubation of the raw material led to an increase in adsorption capacities towards metal ions, which were multiplied by around 2.0 for Zn2+ and 2.3 for Cd2+.

  1. Acute citrulline-malate supplementation improves maximal strength and anaerobic power in female, masters athletes tennis players.

    PubMed

    Glenn, Jordan M; Gray, Michelle; Jensen, Austen; Stone, Matthew S; Vincenzo, Jennifer L

    2016-11-01

    Citrulline-malate (CM) is a precursor to nitric-oxide (NO) in the NO synthase (NOS) pathway and is suggested to increase exercise performance in younger individuals. With age, NO production decreases and augmented NO production may provide beneficial effects on sports performance among masters athletes (MAs). To examine the effects of acute CM supplementation on grip strength, vertical power, and anaerobic cycling performance in female, MA tennis players. Seventeen female MA (51 ± 9 years) completed two double-blind, randomized trials consuming CM (12 g dextrose + 8 g CM) and placebo (PLA) (12 g dextrose). One hour after consumption, subjects completed grip strength, vertical power, and Wingate anaerobic cycling assessments in respective order. Maximal and average grip strength, peak and average vertical power, anaerobic capacity, peak power, explosive power, and ability to sustain anaerobic power were calculated from the tests. When consuming CM, participants exhibited greater maximal (p = .042) and average (p = .045) grip strength compared to PLA. No differences existed between trials for peak (p = .51) or average (p = .51) vertical power. For the Wingate, peak power (p < .001) and explosive power (p < .001) were significantly greater when consuming CM compared to PLA. For the ability to sustain power, a significant effect (p < .001) was observed for time within trials, but no significant differences were observed between trials regarding supplement consumed. These data suggest that consuming CM before competition has the potential to improve tennis match-play performance in masters tennis athletes. However, this study utilized a controlled laboratory environment and research evaluating direct application to on-court performance is warranted.

  2. Evidence for Anaerobic Methane Oxidation Under Iron-Reducing Conditions in a Crude-Oil Contaminated Aquifer

    NASA Astrophysics Data System (ADS)

    Bekins, B. A.; Amos, R. T.; Cozzarelli, I. M.; Voytek, M. A.; Kirshtein, J.; Jones, E. J.; Delin, G. N.

    2008-12-01

    Although anaerobic methane oxidation (AMO) under iron reducing conditions is energetically feasible, its existence is still an open question. At a crude oil spill site near the town of Bemidji, MN, methanogenic degradation of entrapped oil floating at the water table has been occurring for more than 20 years. In the anaerobic portion of the hydrocarbon plume there is evidence for AMO under iron-reducing conditions between 75 m and 120 m downgradient of the oil body. In this zone, dissolved methane concentrations decrease steadily from over 0.6 mmol/L to less than 0.06 mmol/L. Decreases in dissolved methane are accompanied by an increase in δ13C-CH4 indicating that methane attenuation occurs through microbially mediated oxidation. The dissolved methane decrease of ~0.5 mmol/L occurs where dissolved sulfate is below 0.06 mmol/L, dissolved oxygen is below 3 μmol/L, and nitrate is below 0.02 mmol/L. Together these electron acceptors can account for degradation of only 0.07 mmol/L of methane. Moreover, hydrocarbon contaminants contribute an additional ~1 mmol/L total organic carbon in this area. Active iron- reduction is indicated by dissolved iron concentrations exceeding 0.15 mmol/L. To investigate the sediment bioavailable iron and microbial populations, 2-m-long cores were collected at four locations spaced 15 m horizontally and sampled at 50-cm-depth intervals. Values of bioavailable Fe(III) averaged 8 mmol/kg (n=16), which is over eight times the amount required to degrade 0.5 mmol/L methane. Geobacter detected by qPCR averaged over 2,600/g, while sulfate reducing bacteria were detected in only four samples with 100/g being the highest abundance measured. Laboratory incubations were performed with eight sediment samples from these cores. For each location, 1 g of sediment was added to 10 mL anaerobic medium and amended with amorphous FeOOH, Fe(III)NTA, sulfate, or nitrate. Loss of methane occurred in 33% of the iron-amended treatments, 25% of the nitrate

  3. Intracellular Accumulation of Glycine in Polyphosphate-Accumulating Organisms in Activated Sludge, a Novel Storage Mechanism under Dynamic Anaerobic-Aerobic Conditions

    PubMed Central

    Nguyen, Hien Thi Thu; Kristiansen, Rikke; Vestergaard, Mette; Wimmer, Reinhard

    2015-01-01

    Dynamic anaerobic-aerobic feast-famine conditions are applied to wastewater treatment plants to select polyphosphate-accumulating organisms to carry out enhanced biological phosphorus removal. Acetate is a well-known substrate to stimulate this process, and here we show that different amino acids also are suitable substrates, with glycine as the most promising. 13C-labeled glycine and nuclear magnetic resonance (NMR) were applied to investigate uptake and potential storage products when activated sludge was fed with glycine under anaerobic conditions. Glycine was consumed by the biomass, and the majority was stored intracellularly as free glycine and fermentation products. Subsequently, in the aerobic phase without addition of external substrate, the stored glycine was consumed. The uptake of glycine and oxidation of intracellular metabolites took place along with a release and uptake of orthophosphate, respectively. Fluorescence in situ hybridization combined with microautoradiography using 3H-labeled glycine revealed uncultured actinobacterial Tetrasphaera as a dominant glycine consumer. Experiments with Tetrasphaera elongata as representative of uncultured Tetrasphaera showed that under anaerobic conditions it was able to take up labeled glycine and accumulate this and other labeled metabolites to an intracellular concentration of approximately 4 mM. All components were consumed under subsequent aerobic conditions. Intracellular accumulation of amino acids seems to be a novel storage strategy for polyphosphate-accumulating bacteria under dynamic anaerobic-aerobic feast-famine conditions. PMID:25956769

  4. Improved conditions for murine epidermal cell culture.

    PubMed

    Fischer, S M; Viaje, A; Harris, K L; Miller, D R; Bohrman, J S; Slaga, T J

    1980-02-01

    An improved method for cultivating newborn mouse epidermal cells has been developed that increases the longevity, epithelial nature and efficiency of cell-line establishment. The use of Super Medium, an enriched Waymouth's formulation, increased proliferation for long periods of time, as did incubation at 31 degrees C rather than 37 degrees C. The fetal bovine serum requirement was found to be reduced at the lower temperature. An increase in labeling indices was seen when epidermal growth factor (EGF) or the cyclic nucleotides were added and the presence of EGF receptors was determined. Of the prostaglandins (PG) examined, PGE1 and PGE2 produced the greatest increase in DNA synthesis. The PG precursors, arachidonic and 8,11,14-eicosatrienoic acid, were also greatly stimulatory. The use of a lethally irradiated 3T3 feeder layer at 31 degrees C proved superior in maintenance of an epithelial morphology. Subculturable cell lines were established much more readily and reproducibly in carcinogen-treated cultures grown under the improved conditions.

  5. Antimicrobial effects of weak acids on the survival of Escherichia coli O157:H7 under anaerobic conditions.

    PubMed

    Lu, Huiying J; Breidt, Frederick; Pérez-Díaz, Ilenys M; Osborne, Jason A

    2011-06-01

    Outbreaks of disease due to vegetative bacterial pathogens associated with acid foods (such as apple cider) have raised concerns about acidified vegetables and related products that have a similar pH (3.2 to 4.0). Escherichia coli O157:H7 and related strains of enterohemorrhagic E. coli (EHEC) have been identified as the most acid resistant vegetative pathogens in these products. Previous research has shown that the lack of dissolved oxygen in many hermetically sealed acid or acidified food products can enhance survival of EHEC compared with their survival under aerobic conditions. We compared the antimicrobial effects of several food acids (acetic, malic, lactic, fumaric, benzoic, and sorbic acids and sulfite) on a cocktail of EHEC strains under conditions representative of non-heat-processed acidified vegetables in hermetically sealed jars, holding the pH (3.2) and ionic strength (0.342) constant under anaerobic conditions. The overall antimicrobial effectiveness of weak acids used in this study was ranked, from most effective to least effective: sulfite > benzoic acid > sorbic acid > fumaric acid > L- and D-lactic acid > acetic acid > malic acid. These rankings were based on the estimated protonated concentrations required to achieve a 5-log reduction in EHEC after 24 h of incubation at 30°C. This study provides information that can be used to formulate safer acid and acidified food products and provides insights about the mode of action of weak acids against EHEC.

  6. Electron Acceptors Induce Secretion of Enterotoxigenic Escherichia coli Heat-Labile Enterotoxin under Anaerobic Conditions through Promotion of GspD Assembly

    PubMed Central

    Lu, Xi; Fu, Enqing; Xie, Yonghong

    2016-01-01

    Heat-labile enterotoxin (LT), the major virulence factor of enterotoxigenic Escherichia coli (ETEC), can lead to severe diarrhea and promotes ETEC adherence to intestinal epithelial cells. Most previous in vitro studies focused on ETEC pathogenesis were conducted under aerobic conditions, which do not reflect the real situation of ETEC infection because the intestine is anoxic. In this study, the expression and secretion of LT under anaerobic or microaerobic conditions were determined; LT was not efficiently secreted into the supernatant under anaerobic or microaerobic conditions unless terminal electron acceptors (trimethylamine N-oxide dihydrate [TMAO] or nitrate) were available. Furthermore, we found that the restoration effects of TMAO and nitrate on LT secretion could be inhibited by amytal or ΔtorCAD and ΔnarG E. coli strains, indicating that LT secretion under anaerobic conditions was dependent on the integrity of the respiratory chain. At the same time, electron acceptors increase the ATP level of ETEC, but this increase was not the main reason for LT secretion. Subsequently, the relationship between the integrity of the respiratory chain and the function of the type II secretion system was determined. The GspD protein, the secretin of ETEC, was assembled under anaerobic conditions and was accompanied by LT secretion when TMAO or nitrate was added. Our data also demonstrated that TMAO and nitrate could not induce the GspD assembly and LT secretion in ΔtorCAD and ΔnarG strains, respectively. Moreover, GspD assembly under anaerobic conditions was assisted by the pilot protein YghG. PMID:27430271

  7. Determination of the in vivo NAD:NADH ratio in Saccharomyces cerevisiae under anaerobic conditions, using alcohol dehydrogenase as sensor reaction.

    PubMed

    Bekers, K M; Heijnen, J J; van Gulik, W M

    2015-08-01

    With the current quantitative metabolomics techniques, only whole-cell concentrations of NAD and NADH can be quantified. These measurements cannot provide information on the in vivo redox state of the cells, which is determined by the ratio of the free forms only. In this work we quantified free NAD:NADH ratios in yeast under anaerobic conditions, using alcohol dehydrogenase (ADH) and the lumped reaction of glyceraldehyde-3-phosphate dehydrogenase and 3-phosphoglycerate kinase as sensor reactions. We showed that, with an alternative accurate acetaldehyde determination method, based on rapid sampling, instantaneous derivatization with 2,4 diaminophenol hydrazine (DNPH) and quantification with HPLC, the ADH-catalysed oxidation of ethanol to acetaldehyde can be applied as a relatively fast and simple sensor reaction to quantify the free NAD:NADH ratio under anaerobic conditions. We evaluated the applicability of ADH as a sensor reaction in the yeast Saccharomyces cerevisiae, grown in anaerobic glucose-limited chemostats under steady-state and dynamic conditions. The results found in this study showed that the cytosolic redox status (NAD:NADH ratio) of yeast is at least one order of magnitude lower, and is thus much more reduced, under anaerobic conditions compared to aerobic glucose-limited steady-state conditions. The more reduced state of the cytosol under anaerobic conditions has major implications for (central) metabolism. Accurate determination of the free NAD:NADH ratio is therefore of importance for the unravelling of in vivo enzyme kinetics and to judge accurately the thermodynamic reversibility of each redox reaction.

  8. Anaerobic thermophilic culture

    DOEpatents

    Ljungdahl, Lars G.; Wiegel, Jurgen K. W.

    1981-01-01

    A newly discovered thermophilic anaerobe is described that was isolated in a biologically pure culture and designated Thermoanaerobacter ethanolicus ATCC 3/550. T. Ethanolicus is cultured in aqueous nutrient medium under anaerobic, thermophilic conditions and is used in a novel process for producing ethanol by subjecting carbohydrates, particularly the saccharides, to fermentation action of the new microorganism in a biologically pure culture.

  9. Pathways of N removal and N2O emission from a one-stage autotrophic N removal process under anaerobic conditions

    PubMed Central

    Li, Kai; Fang, Fang; Wang, Han; Wang, Chao; Chen, Youpeng; Guo, Jinsong; Wang, Xixi; Jiang, Fuyang

    2017-01-01

    To investigate the pathways of nitrogen (N) removal and N2O emission in a one-stage autotrophic N removal process during the non-aeration phase, biofilm from an intermittent aeration sequencing batch biofilm reactor (SBBR) and organic carbon-free synthetic wastewater were applied to two groups of lab-scale batch experiments in anaerobic conditions using a 15N isotopic tracer and specific inhibitors, respectively. Then, the microbial composition of the biofilm was analysed using high-throughput sequencing. The results of the 15N isotopic experiments showed that anaerobic ammonium oxidation (Anammox) was the main pathway of N transformation under anaerobic conditions and was responsible for 83–92% of N2 production within 24 h. Furthermore, experiments using specific inhibitors revealed that when nitrite was the main N source under anaerobic conditions, N2O emissions from heterotrophic denitrification (HD) and ammonia-oxidizing bacteria (AOB) denitrification were 64% and 36%, respectively. Finally, analysing the microbial composition demonstrated that Proteobacteria, Planctomycetes, and Nitrospirae were the dominant microbes, corresponding to 21%, 13%, and 7% of the microbial community, respectively, and were probably responsible for HD, Anammox, and AOB denitrification, respectively. PMID:28205581

  10. Pathways of N removal and N2O emission from a one-stage autotrophic N removal process under anaerobic conditions

    NASA Astrophysics Data System (ADS)

    Li, Kai; Fang, Fang; Wang, Han; Wang, Chao; Chen, Youpeng; Guo, Jinsong; Wang, Xixi; Jiang, Fuyang

    2017-02-01

    To investigate the pathways of nitrogen (N) removal and N2O emission in a one-stage autotrophic N removal process during the non-aeration phase, biofilm from an intermittent aeration sequencing batch biofilm reactor (SBBR) and organic carbon-free synthetic wastewater were applied to two groups of lab-scale batch experiments in anaerobic conditions using a 15N isotopic tracer and specific inhibitors, respectively. Then, the microbial composition of the biofilm was analysed using high-throughput sequencing. The results of the 15N isotopic experiments showed that anaerobic ammonium oxidation (Anammox) was the main pathway of N transformation under anaerobic conditions and was responsible for 83-92% of N2 production within 24 h. Furthermore, experiments using specific inhibitors revealed that when nitrite was the main N source under anaerobic conditions, N2O emissions from heterotrophic denitrification (HD) and ammonia-oxidizing bacteria (AOB) denitrification were 64% and 36%, respectively. Finally, analysing the microbial composition demonstrated that Proteobacteria, Planctomycetes, and Nitrospirae were the dominant microbes, corresponding to 21%, 13%, and 7% of the microbial community, respectively, and were probably responsible for HD, Anammox, and AOB denitrification, respectively.

  11. Anaerobic submerged membrane bioreactor (AnSMBR) for municipal wastewater treatment under mesophilic and psychrophilic temperature conditions.

    PubMed

    Martinez-Sosa, David; Helmreich, Brigitte; Netter, Thomas; Paris, Stefania; Bischof, Franz; Horn, Harald

    2011-11-01

    A pilot scale anaerobic submerged membrane bioreactor (AnSMBR) with an external filtration unit for municipal wastewater treatment was operated for 100 days. Besides gas sparging, additional shear was created by circulating sludge to control membrane fouling. During the first 69 days, the reactor was operated under mesophilic temperature conditions. Afterwards, the temperature was gradually reduced to 20 °C. A slow and linear increase in the filtration resistance was observed under critical flux conditions (7 L/(m2 h)) at 35 °C. However, an increase in the fouling rate probably linked to an accumulation of solids, a higher viscosity and soluble COD concentrations in the reactor was observed at 20 °C. The COD removal efficiency was close to 90% under both temperature ranges. Effluent COD and BOD5 concentrations were lower than 80 and 25 mg/L, respectively. Pathogen indicator microorganisms (fecal coliforms bacteria) were reduced by log(10)5. Hence, the effluent could be used for irrigation purposes in agriculture. Copyright © 2011 Elsevier Ltd. All rights reserved.

  12. Corrosion and fate of depleted uranium penetrators under progressively anaerobic conditions in estuarine sediment.

    PubMed

    Handley-Sidhu, Stephanie; Worsfold, Paul J; Boothman, Christopher; Lloyd, Jonathan R; Alvarez, Rebeca; Livens, Francis R; Vaughan, David J; Keith-Roach, Miranda J

    2009-01-15

    The testing of armor-piercing depleted uranium (DU) "penetrators" has resulted in the deposition of DU in the sediments of the Solway Firth, UK. In this study, DU-amended, microcosm experiments simulating Solway Firth sediments under high (31.5) and medium (16.5) salinity conditions were used to investigate the effect of salinity and biogeochemical conditions on the corrosion and fate of DU, and the impact of the corroding DU on the microbial population. Under suboxic conditions, the average corrosion rates were the same forthe 31.5 and 16.5 salinity systems at 0.056 +/- 0.006 g cm(-2) y(-1), implying that complete corrosion of a 120 mm penetrator would take approximately 540 years. Under sulfate-reducing conditions, corrosion ceased due to passivation of the surface. Corroding DU resulted in more reducing conditions and decreased microbial diversity as indicated by DNA sequencing and phylogenetic analysis. The lack of colloidal and particulate DU corrosion products, along with measurable dissolved U and a homogeneous association of U with the sediment, suggest that U was transported from the penetrator surface into the surrounding environment through dissolution of U(VI), with subsequent interactions resulting in the formation of secondary uranium species in the sediment.

  13. Minimizing asynchronism to improve the performances of anaerobic co-digestion of food waste and corn stover.

    PubMed

    Zhou, Qi; Shen, Fei; Yuan, Hairong; Zou, Dexun; Liu, Yanping; Zhu, Baoning; Jaffu, Muhanmad; Chufo, Akiber; Li, Xiujin

    2014-08-01

    To investigate the existence of the asynchronism during the anaerobic co-digestion of different substrates, two typical substrates of food waste and corn stover were anaerobically digested with altering organic loadings (OL). The results indicated that the biodegradability of food waste and corn stover was calculated to be 81.5% and 55.1%, respectively, which was main reason causing the asynchronism in the co-digestion. The asynchronism was minimized by NaOH-pretreatment for corn stover, which could improve the biodegradability by 36.6%. The co-digestion with pretreatment could increase the biomethane yield by 12.2%, 3.2% and 0.6% comparing with the co-digestion without pretreatment at C/N ratios of 20, 25 and 30 at OL of 35 g-VS/L, respectively. The results indicated that the digestibility synchronism of food waste and corn stover was improved through enhancing the accessibility and digestibility of corn stover. The biomethane production could be increased by minimizing the asynchronism of two substrates in co-digestion.

  14. Improving Biomethane Production and Mass Bioconversion of Corn Stover Anaerobic Digestion by Adding NaOH Pretreatment and Trace Elements

    PubMed Central

    Liu, ChunMei; Yuan, HaiRong; Zou, DeXun; Liu, YanPing; Zhu, BaoNing; Li, XiuJin

    2015-01-01

    This research applied sodium hydroxide (NaOH) pretreatment and trace elements to improve biomethane production when using corn stover for anaerobic digestion. Full-factor experimental tests identified the best combination of trace elements with the NaOH pretreatment, indicating that the best combination was with 1.0, 0.4, and 0.4 mg·L−1·d−1 of elements Fe, Co, and Ni, respectively. The cumulative biomethane production adding NaOH pretreatment and trace elements was 11,367 mL; total solid bioconversion rate was 55.7%, which was 41.8%–62.2% higher than with NaOH-pretreatment alone and 22.2%–56.3% higher than with untreated corn stover. The best combination was obtained 5–9 days shorter than T90 and maintained good system operation stability. Only a fraction of the trace elements in the best combination was present in the resulting solution; more than 85% of the total amounts added were transferred into the solid fraction. Adding 0.897 g of Fe, 0.389 g of Co, and 0.349 g of Ni satisfied anaerobic digestion needs and enhanced biological activity at the beginning of the operation. The results showed that NaOH pretreatment and adding trace elements improve corn stover biodegradability and enhance biomethane production. PMID:26137469

  15. Improving the mixing performances of rice straw anaerobic digestion for higher biogas production by computational fluid dynamics (CFD) simulation.

    PubMed

    Shen, Fei; Tian, Libin; Yuan, Hairong; Pang, Yunzhi; Chen, Shulin; Zou, Dexun; Zhu, Baoning; Liu, Yanping; Li, Xiujin

    2013-10-01

    As a lignocellulose-based substrate for anaerobic digestion, rice straw is characterized by low density, high water absorbability, and poor fluidity. Its mixing performances in digestion are completely different from traditional substrates such as animal manures. Computational fluid dynamics (CFD) simulation was employed to investigate mixing performances and determine suitable stirring parameters for efficient biogas production from rice straw. The results from CFD simulation were applied in the anaerobic digestion tests to further investigate their reliability. The results indicated that the mixing performances could be improved by triple impellers with pitched blade, and complete mixing was easily achieved at the stirring rate of 80 rpm, as compared to 20-60 rpm. However, mixing could not be significantly improved when the stirring rate was further increased from 80 to 160 rpm. The simulation results agreed well with the experimental results. The determined mixing parameters could achieve the highest biogas yield of 370 mL (g TS)(-1) (729 mL (g TS(digested))(-1)) and 431 mL (g TS)(-1) (632 mL (g TS(digested))(-1)) with the shortest technical digestion time (T 80) of 46 days. The results obtained in this work could provide useful guides for the design and operation of biogas plants using rice straw as substrates.

  16. Anaerobic Biodegradation of soybean biodiesel and diesel blends under sulfate-reducing conditions

    EPA Science Inventory

    Biotransformation of soybean biodiesel and its biodiesel/petrodiesel blends were investigated under sulfate-reducing conditions. Three blends of biodiesel, B100, B50, and B0, were treated using microbial cultures pre-acclimated to B100 (biodiesel only) and B80 (80% biodiesel and ...

  17. Biogas production from co-digestion of corn stover and chicken manure under anaerobic wet, hemi-solid, and solid state conditions.

    PubMed

    Li, Yeqing; Zhang, Ruihong; Chen, Chang; Liu, Guangqing; He, Yanfeng; Liu, Xiaoying

    2013-12-01

    Corn stover (CS) and chicken manure (CM) are ubiquitous agricultural wastes at low cost and have the potential to achieve a nutrient-balance when mixed together to produce biomethane via anaerobic digestion (AD). The main objective of this work was to investigate methane production at different CS to CM ratios and to evaluate the process stability under wet (W-AD), hemi-solid state (HSS-AD) and solid state (SS-AD) conditions. Results showed that synergistic effects were found when mixing two substrates at CS:CM ratios of 3:1 and 1:1 (on volatile solid basis). The highest methane yield of 218.8 mL/g VS added was achieved in W-AD at CS:CM ratio of 3:1. In SS-AD, the highest volumetric methane productivity of 14.2L methane/L reactor volume was found at CS:CM of 1:1. The results of this work provide useful information to improve the efficiency and stability of co-digestion of CS and CM under different AD conditions. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Anaerobic biodegradation of soybean biodiesel and diesel blends under sulfate-reducing conditions.

    PubMed

    Wu, Shuyun; Yassine, Mohamad H; Suidan, Makram T; Venosa, Albert D

    2016-10-01

    Biotransformation of soybean biodiesel and its biodiesel/petrodiesel blends were investigated under sulfate-reducing conditions. Three blends of biodiesel, B100, B50, and B0, were treated using microbial cultures pre-acclimated to B100 (biodiesel only) and B80 (80% biodiesel and 20% petrodiesel). Results indicate that the biodiesel could be effectively biodegraded in the presence or absence of petrodiesel, whereas petrodiesel could not be biodegraded at all under sulfate-reducing conditions. The kinetics of biodegradation of individual Fatty Acid Methyl Ester (FAME) compounds and their accompanying sulfate-reduction rates were studied using a serum bottle test. As for the biodegradation of individual FAME compounds, the biodegradation rates for the saturated FAMEs decreased with increasing carbon chain length. For unsaturated FAMEs, biodegradation rates increased with increasing number of double bonds. The presence of petrodiesel had a greater effect on the rate of biodegradation of biodiesel than on the extent of removal.

  19. A genomic island of the sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough promotes survival under stress conditions while decreasing the efficiency of anaerobic growth.

    PubMed

    Johnston, Shawna; Lin, Shiping; Lee, Phoebe; Caffrey, Sean M; Wildschut, Janine; Voordouw, Johanna K; da Silva, Sofia M; Pereira, Ines A C; Voordouw, Gerrit

    2009-04-01

    A 47 kb genomic island (GEI) bracketed by 50 bp direct repeats, containing 52 annotated genes, was found to delete spontaneously from the genome of Desulfovibrio vulgaris Hildenborough. The island contains genes for site-specific recombinases and transposases, rubredoxin:oxygen oxidoreductase-1 (Roo1) and hybrid cluster protein-1 (Hcp1), which promote survival in air and nitrite stress. The numbering distinguishes these from the Roo2 and Hcp2 homologues for which the genes are located elsewhere in the genome. Cells with and without the island (GEI(+) and GEI(-) cells respectively) were obtained by colony purification. GEI(-) cells arise in anaerobic cultures of colony-purified GEI(+) cells, indicating that the site-specific recombinases encoded by the island actively delete this region. GEI(+) cells survive better in microaerophilic conditions due to the presence of Roo1, whereas the Hcps appear to prevent inhibition by sulfur and polysulfide, which are formed by chemical reaction of sulfide and nitrite. Hence, the island confers resistance to oxygen and nitrite stress. However, GEI(-) cells have a higher growth rate in anaerobic media. Microarrays and enzyme activity stains indicated that the GEI(-) cells have increased expression of genes, which promote anaerobic energy conservation, explaining the higher growth rate. Hence, while lowering the efficiency of anaerobic metabolism, the GEI increases the fitness of D. vulgaris under stress conditions, a feature reminiscent of pathogenicity islands which allow more effective colonization of environments provided by the targeted hosts.

  20. Effects of anaerobic growth conditions on biomass accumulation, root morphology, and efficiencies of nutrient uptake and utilization in seedlings of some southern coastal plain

    SciTech Connect

    Topa, M.A.

    1984-01-01

    Seedlings of pond, and loblolly pines were grown in a non-circulating, continuously-flowing solution culture under anaerobic (0.75 mg/1 O/sub 2/) conditions to determine the effects of anaerobiosis on overall growth, root morphology and efficiencies of nutrient uptake and utilization. Although shoot growth of the 11-week old loblolly and pond was not affected by anaerobic treatment, it did significantly reduce root biomass. Sand pine suffered the largest biomass reduction. Flooding tolerance was positively correlated with morphological changes which enhanced root internal aeration. Oxygen transport from shoot to the root was demonstrated via rhizosphere oxidation experiments using indigo-carmine dye solutions and polarography. Stem and root collar lenticels were found to be the major sites of atmospheric O/sub 2/ entry for submerged roots. Longitudinal and radial pathways for gas diffusion via intercellular spaces in the pericycle and ray parenchyma, respectively, were elucidated histologically. Lenticel and aerenchyma development, and rhizosphere oxidation in roots of anaerobically-grown sand pine seedlings were minimal. Elemental analyses showed that anaerobic conditions interfered with nutrient absorption and utilization. Short-term /sup 32/P uptake experiments with intact seedlings indicated that net absorption decreased because of the reduction in root biomass. Phosphorus absorption rates were negatively correlated with internal tissue phosphorus concentrations, and root and shoot biomass. 315 refs., 25 figs., 14 tabs.

  1. Removal of estrogens in municipal wastewater treatment under aerobic and anaerobic conditions: consequences for plant optimization.

    PubMed

    Joss, Adriano; Andersen, Henrik; Ternes, Thomas; Richle, Philip R; Siegrist, Hansruedi

    2004-06-01

    The removal of estrogens (estrone E1, estradiol E2, and ethinylestradiol EE2) was studied in various municipal wastewater treatment processes equipped for nutrient removal. A biological degradation model is formulated, and kinetic parameters are evaluated with batch experiments under various redox conditions. The resulting model calculations are then compared with sampling campaigns performed on differenttypes of full-scale plant: conventional activated-sludge treatment, a membrane bioreactor, and a fixed-bed reactor. The results show a > 90% removal of all estrogens in the activated sludge processes. (Due to the analytical quantification limit and low influent concentrations, however, this removal efficiency represents only an observable minimum.) The removal efficiencies of 77% and > or = 90% for E1 and E2, respectively, in the fixed-bed reactor represent a good performance in view of the short hydraulic retention time of 35 min. The first-order removal-rate constant in batch experiments observed for E2 varied from 150 to 950 d(-1) for a 1 gSS L(-1) sludge suspension. The removal efficiency of E1 and EE2 clearly depends on the redox conditions, the maximum removal rate occurring under aerobic conditions when E1 was reduced to E2. Sampling campaigns on full-scale plants indicate that the kinetic values identified in batch experiments (without substrate addition) for the natural estrogens may overestimate the actual removal rates. Although this paper does not give direct experimental evidence, it seems that the substrate present in the raw influent competitively inhibits the degradation of E1 and E2. These compounds are therefore removed mainly in activated sludge compartments with low substrate loading. Theoretical evaluation leads us to expect that diffusive mass transfer inside the floc (but not across the laminar boundary layer) appreciably influences the observed degradation rates of E1 and E2, but not of EE2.

  2. Unravelling the active microbial community in a thermophilic anaerobic digester-microbial electrolysis cell coupled system under different conditions.

    PubMed

    Cerrillo, Míriam; Viñas, Marc; Bonmatí, August

    2017-03-01

    Thermophilic anaerobic digestion (AD) of pig slurry coupled to a microbial electrolysis cell (MEC) with a recirculation loop was studied at lab-scale as a strategy to increase AD stability when submitted to organic and nitrogen overloads. The system performance was studied, with the recirculation loop both connected and disconnected, in terms of AD methane production, chemical oxygen demand removal (COD) and volatile fatty acid (VFA) concentrations. Furthermore, the microbial population was quantitatively and qualitatively assessed through DNA and RNA-based qPCR and high throughput sequencing (MiSeq), respectively to identify the RNA-based active microbial populations from the total DNA-based microbial community composition both in the AD and MEC reactors under different operational conditions. Suppression of the recirculation loop reduced the AD COD removal efficiency (from 40% to 22%) and the methane production (from 0.32 to 0.03 m(3) m(-3) d(-1)). Restoring the recirculation loop led to a methane production of 0.55 m(3) m(-3) d(-1) concomitant with maximum MEC COD and ammonium removal efficiencies of 29% and 34%, respectively. Regarding microbial analysis, the composition of the AD and MEC anode populations differed from really active microorganisms. Desulfuromonadaceae was revealed as the most active family in the MEC (18%-19% of the RNA relative abundance), while hydrogenotrophic methanogens (Methanobacteriaceae) dominated the AD biomass. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Anaerobic co-digestion of steam-treated Quercus serrata chips and sewage sludge under mesophilic and thermophilic conditions.

    PubMed

    Wang, Feng; Hidaka, Taira; Sakurai, Kensuke; Tsumori, Jun

    2014-08-01

    The biodegradation of Quercus serrata chips was evaluated by anaerobic digestion under various steam explosion conditions. In continuous experiments, untreated chips (W₀) and chips steam-treated at less than 1.0 MPa (W₁) and 2.0 MPa (W₄) were co-digested with sewage sludge (S₁ and S₂) taken from two different wastewater treatment plants. The apparent methane yield of W₁ and W₄ co-digested with S₁ (thermophilic) was 261 dm(3)/kgVS (volatile solids) and 248 dm(3)/kgVS, respectively. The apparent methane yield of W₄ co-digested with S₂ was 258 dm(3)/kgVS (mesophilic) and 271 dm(3)/kgVS (thermophilic). Methane production was inhibited by W₀ due to components released during hydrolysis. The methane conversion ratio of pretreated chips obtained in batch experiments varied from 40.5% to 53.8% (mesophilic) and from 49.0% to 63.7% (thermophilic). The methane conversion ratio increased with decreasing acid-soluble lignin content in the chips.

  4. Anaerobic digestion of whole stillage from dry-grind corn ethanol plant under mesophilic and thermophilic conditions.

    PubMed

    Eskicioglu, Cigdem; Kennedy, Kevin J; Marin, Juan; Strehler, Benjamin

    2011-01-01

    Anaerobic digestion of whole stillage from a dry-grind corn-based ethanol plant was evaluated by batch and continuous-flow digesters under thermophilic and mesophilic conditions. At whole corn stillage concentrations of 6348 to 50,786 mg total chemical oxygen demand (TCOD)/L, at standard temperature (0 °C) and pressure (1 atm), preliminary biochemical methane potential assays produced 88±8 L (49±5 L CH4) and 96±19 L (65±14 L CH4) biogas per L stillage from mesophilic and thermophilic digesters, respectively. Continuous-flow studies for the full-strength stillage (TCOD=254 g/L) at organic loadings of 4.25, 6.30 and 9.05 g TCOD/L days indicated unstable performance for the thermophilic digester. Among the sludge retention times (SRTs) of 60, 45 and 30 days tested, the mesophilic digestion was successful only at 60 days-SRT which does not represent a practical operation time for a large scale bioethanol plant. Future laboratory studies will focus on different reactor configurations to reduce the SRT needed in the digesters.

  5. Decolorization and detoxification of a sulfonated triphenylmethane dye aniline blue by Shewanella oneidensis MR-1 under anaerobic conditions.

    PubMed

    Wu, Yongmin; Xiao, Xiang; Xu, Cancan; Cao, Danming; Du, Daolin

    2013-08-01

    In this work, the extracellular decolorization of aniline blue, a sulfonated triphenylmethane dye, by Shewanella oneidensis MR-1 was confirmed. S. oneidensis MR-1 showed a high capacity for decolorizing aniline blue even at a concentration of up to 1,000 mg/l under anaerobic conditions. Maximum decolorization efficiency appeared at pH 7.0 and 30 °C. Lactate was a better candidate of electron donor for the decolorization of aniline blue. The addition of nitrate, hydrous ferric oxide, or trimethylamine N-oxide all could cause a significant decline of decolorization efficiency. The Mtr respiratory pathway was found to be involved into the decolorization of aniline blue by S. oneidensis MR-1. The toxicity evaluation through phytotoxicity and genotoxicity showed that S. oneidensis MR-1 could decrease the toxicity of aniline blue during the decolorization process. Thus, this work may facilitate a better understanding on the degradation mechanisms of the triphenylmethane dyes by Shewanella and is beneficial to their application in bioremediation.

  6. Ammonia inhibition on hydrogen enriched anaerobic digestion of manure under mesophilic and thermophilic conditions.

    PubMed

    Wang, Han; Zhang, Yifeng; Angelidaki, Irini

    2016-11-15

    Capturing of carbon dioxide by hydrogen derived from excess renewable energy (e.g., wind mills) to methane in a microbially catalyzed process offers an attractive technology for biogas production and upgrading. This bioconversion process is catalyzed by hydrogenotrophic methanogens, which are known to be sensitive to ammonia. In this study, the tolerance of the biogas process under supply of hydrogen, to ammonia toxicity was studied under mesophilic and thermophilic conditions. When the initial hydrogen partial pressure was 0.5 atm, the methane yield at high ammonia load (7 g NH4(+)-N L(-1)) was 41.0% and 22.3% lower than that at low ammonia load (1 g NH4(+)-N L(-1)) in mesophilic and thermophilic condition, respectively. Meanwhile no significant effect on the biogas composition was observed. Moreover, we found that hydrogentrophic methanogens were more tolerant to the ammonia toxicity than acetoclastic methanogens in the hydrogen enriched biogas production and upgrading processes. The highest methane production yield was achieved under 0.5 atm hydrogen partial pressure in batch reactors at all the tested ammonia levels. Furthermore, the thermophilic methanogens at 0.5 atm of hydrogen partial pressure were more tolerant to high ammonia levels (≥5 g NH4(+)-N L(-1)), compared with mesophilic methanogens. The present study offers insight in developing resistant hydrogen enriched biogas production and upgrading processes treating ammonia-rich waste streams.

  7. Linked Redox Precipitation of Sulfur and Selenium under Anaerobic Conditions by Sulfate-Reducing Bacterial Biofilms

    PubMed Central

    Hockin, Simon L.; Gadd, Geoffrey M.

    2003-01-01

    A biofilm-forming strain of sulfate-reducing bacteria (SRB), isolated from a naturally occurring mixed biofilm and identified by 16S rDNA analysis as a strain of Desulfomicrobium norvegicum, rapidly removed 200 μM selenite from solution during growth on lactate and sulfate. Elemental selenium and elemental sulfur were precipitated outside SRB cells. Precipitation occurred by an abiotic reaction with bacterially generated sulfide. This appears to be a generalized ability among SRB, arising from dissimilatory sulfide biogenesis, and can take place under low redox conditions and in the dark. The reaction represents a new means for the deposition of elemental sulfur by SRB under such conditions. A combination of transmission electron microscopy, environmental scanning electron microscopy, and cryostage field emission scanning electron microscopy were used to reveal the hydrated nature of SRB biofilms and to investigate the location of deposited sulfur-selenium in relation to biofilm elements. When pregrown SRB biofilms were exposed to a selenite-containing medium, nanometer-sized selenium-sulfur granules were precipitated within the biofilm matrix. Selenite was therefore shown to pass through the biofilm matrix before reacting with bacterially generated sulfide. This constitutes an efficient method for the removal of toxic concentrations of selenite from solution. Implications for environmental cycling and the fate of sulfur and selenium are discussed, and a general model for the potential action of SRB in selenium transformations is presented. PMID:14660350

  8. Linked redox precipitation of sulfur and selenium under anaerobic conditions by sulfate-reducing bacterial biofilms.

    PubMed

    Hockin, Simon L; Gadd, Geoffrey M

    2003-12-01

    A biofilm-forming strain of sulfate-reducing bacteria (SRB), isolated from a naturally occurring mixed biofilm and identified by 16S rDNA analysis as a strain of Desulfomicrobium norvegicum, rapidly removed 200 micro M selenite from solution during growth on lactate and sulfate. Elemental selenium and elemental sulfur were precipitated outside SRB cells. Precipitation occurred by an abiotic reaction with bacterially generated sulfide. This appears to be a generalized ability among SRB, arising from dissimilatory sulfide biogenesis, and can take place under low redox conditions and in the dark. The reaction represents a new means for the deposition of elemental sulfur by SRB under such conditions. A combination of transmission electron microscopy, environmental scanning electron microscopy, and cryostage field emission scanning electron microscopy were used to reveal the hydrated nature of SRB biofilms and to investigate the location of deposited sulfur-selenium in relation to biofilm elements. When pregrown SRB biofilms were exposed to a selenite-containing medium, nanometer-sized selenium-sulfur granules were precipitated within the biofilm matrix. Selenite was therefore shown to pass through the biofilm matrix before reacting with bacterially generated sulfide. This constitutes an efficient method for the removal of toxic concentrations of selenite from solution. Implications for environmental cycling and the fate of sulfur and selenium are discussed, and a general model for the potential action of SRB in selenium transformations is presented.

  9. Improving anaerobic digestion of easy-acidification substrates by promoting buffering capacity using biochar derived from vermicompost.

    PubMed

    Wang, Dou; Ai, Jing; Shen, Fei; Yang, Gang; Zhang, Yanzong; Deng, Shihuai; Zhang, Jing; Zeng, Yongmei; Song, Chun

    2017-03-01

    Acid-buffering of VCBC and VC was evaluated using 4 VFAs, and their application on anaerobic digestion of CM and KW was investigated. Results indicated acid-buffering capacity of VCBC to acetic, propionic, butyric, and valeric acid was 2.5, 1.1, 1.9 and 1.6-fold higher comparing with VC. CM digestion was not initiated at higher organic loading of 50gTS/kg, while it worked well with 5.0% VCBC or VC. KW was not digested even though VC or VCBC was increased to 15% and 20%. However, KW digestion can be alleviated with increasing VCBC or VC proportion, in which the alleviation by VCBC was better than VC. Average VFAs concentration during CM digestion with VC was 4077.7mg/L comparing with 2835.8mg/L of VCBC, and biogas release was delayed for 10-days accompanying rapid pH decrease in CM digestion with VC, which reflected acid-buffering of biochar played a crucial role on improving anaerobic digestion.

  10. Improvement of hydrogen production via ethanol-type fermentation in an anaerobic down-flow structured bed reactor.

    PubMed

    Anzola-Rojas, Mélida del Pilar; Zaiat, Marcelo; De Wever, Heleen

    2016-02-01

    Although a novel anaerobic down-flow structured bed reactor has shown feasibility and stable performance for a long-term compared to other anaerobic fixed bed systems for continuous hydrogen production, the volumetric rates and yields have so far been too low. In order to improve the performance, an operation strategy was applied by organic loading rate (OLR) variation (12-96 g COD L(-1) d(-1)). Different volumetric hydrogen rates, and yields at the same OLR indicated that the system was mainly driven by the specific organic load (SOL). When SOL was kept between 3.8 and 6.2 g sucrose g(-1) VSS d(-1), the volumetric rates raised from 0.1 to 8.9 L H2 L(-1) d(-1), and the yields were stable around 2.0 mol H2 mol(-1) converted sucrose. Furthermore, hydrogen was produced mainly via ethanol-type fermentation, reaching a total energy conversion rate of 23.40 kJ h(-1) L(-1) based on both hydrogen and ethanol production.

  11. Effect of fermentation conditions on biohydrogen production from cassava starch by anaerobic mixed cultures

    NASA Astrophysics Data System (ADS)

    Tien, Hai M.; Le, Kien A.; Tran, An T.; Le, Phung K.

    2016-06-01

    In this work, a series of batch tests were conducted to investigate the effect of pH, temperature, fermentation time, and inoculums ratio to hydrogen production using cassava starch as a substrate. The statistical analysis of the experiment indicated that the significant effects for the fermentation yield were the main effect of temperature, pH and inoculums ratio. It was fouund that the suitable fermentation conditions of biohydrogen production should be at temperature 40 ° C; pH 6.5, inoculums to medium ratio 10 % and COD operation at 4800 g/mL. The maximum value of hydrogen volume produced was 76.22 mL. These affected has been evaluated and the result can be used as an reference for the pilot or industrial biohydrogen production.

  12. Post-translational modification of Cu/Zn superoxide dismutase under anaerobic conditions.

    PubMed

    Leitch, Jeffry M; Li, Cissy X; Baron, J Allen; Matthews, Lauren M; Cao, Xiaohang; Hart, P John; Culotta, Valeria C

    2012-01-17

    In eukaryotic organisms, the largely cytosolic copper- and zinc-containing superoxide dismutase (Cu/Zn SOD) enzyme represents a key defense against reactive oxygen toxicity. Although much is known about the biology of this enzyme under aerobic conditions, less is understood regarding the effects of low oxygen levels on Cu/Zn SOD enzymes from diverse organisms. We show here that like bakers' yeast (Saccharomyces cerevisiae), adaptation of the multicellular Caenorhabditis elegans to growth at low oxygen levels involves strong downregulation of its Cu/Zn SOD. Much of this regulation occurs at the post-translational level where CCS-independent activation of Cu/Zn SOD is inhibited. Hypoxia inactivates the endogenous Cu/Zn SOD of C. elegans Cu/Zn SOD as well as a P144 mutant of S. cerevisiae Cu/Zn SOD (herein denoted Sod1p) that is independent of CCS. In our studies of S. cerevisiae Sod1p, we noted a post-translational modification to the inactive enzyme during hypoxia. Analysis of this modification by mass spectrometry revealed phosphorylation at serine 38. Serine 38 represents a putative proline-directed kinase target site located on a solvent-exposed loop that is positioned at one end of the Sod1p β-barrel, a region immediately adjacent to residues previously shown to influence CCS-dependent activation. Although phosphorylation of serine 38 is minimal when the Sod1p is abundantly active (e.g., high oxygen level), up to 50% of Sod1p can be phosphorylated when CCS activation of the enzyme is blocked, e.g., by hypoxia or low-copper conditions. Serine 38 phosphorylation can be a marker for inactive pools of Sod1p.

  13. Effect of increasing total solids contents on anaerobic digestion of food waste under mesophilic conditions: performance and microbial characteristics analysis.

    PubMed

    Yi, Jing; Dong, Bin; Jin, Jingwei; Dai, Xiaohu

    2014-01-01

    The total solids content of feedstocks affects the performances of anaerobic digestion and the change of total solids content will lead the change of microbial morphology in systems. In order to increase the efficiency of anaerobic digestion, it is necessary to understand the role of the total solids content on the behavior of the microbial communities involved in anaerobic digestion of organic matter from wet to dry technology. The performances of mesophilic anaerobic digestion of food waste with different total solids contents from 5% to 20% were compared and the microbial communities in reactors were investigated using 454 pyrosequencing technology. Three stable anaerobic digestion processes were achieved for food waste biodegradation and methane generation. Better performances mainly including volatile solids reduction and methane yield were obtained in the reactors with higher total solids content. Pyrosequencing results revealed significant shifts in bacterial community with increasing total solids contents. The proportion of phylum Chloroflexi decreased obviously with increasing total solids contents while other functional bacteria showed increasing trend. Methanosarcina absolutely dominated in archaeal communities in three reactors and the relative abundance of this group showed increasing trend with increasing total solids contents. These results revealed the effects of the total solids content on the performance parameters and the behavior of the microbial communities involved in the anaerobic digestion of food waste from wet to dry technologies.

  14. Effect of Increasing Total Solids Contents on Anaerobic Digestion of Food Waste under Mesophilic Conditions: Performance and Microbial Characteristics Analysis

    PubMed Central

    Jin, Jingwei; Dai, Xiaohu

    2014-01-01

    The total solids content of feedstocks affects the performances of anaerobic digestion and the change of total solids content will lead the change of microbial morphology in systems. In order to increase the efficiency of anaerobic digestion, it is necessary to understand the role of the total solids content on the behavior of the microbial communities involved in anaerobic digestion of organic matter from wet to dry technology. The performances of mesophilic anaerobic digestion of food waste with different total solids contents from 5% to 20% were compared and the microbial communities in reactors were investigated using 454 pyrosequencing technology. Three stable anaerobic digestion processes were achieved for food waste biodegradation and methane generation. Better performances mainly including volatile solids reduction and methane yield were obtained in the reactors with higher total solids content. Pyrosequencing results revealed significant shifts in bacterial community with increasing total solids contents. The proportion of phylum Chloroflexi decreased obviously with increasing total solids contents while other functional bacteria showed increasing trend. Methanosarcina absolutely dominated in archaeal communities in three reactors and the relative abundance of this group showed increasing trend with increasing total solids contents. These results revealed the effects of the total solids content on the performance parameters and the behavior of the microbial communities involved in the anaerobic digestion of food waste from wet to dry technologies. PMID:25051352

  15. Laboratory Study of Chemical Speciation of Mercury in Lake Sediment and Water under Aerobic and Anaerobic Conditions

    PubMed Central

    Regnell, Olof; Tunlid, Anders

    1991-01-01

    Chemical speciation and partitioning of radiolabeled HgCl2 were studied in model aquatic systems consisting of undisturbed eutrophic lake sediment and water in plastic cylinders. The cylinders were either gradually made anaerobic by a gentle flow of N2-CO2 or kept aerobic by air flow. The proportion of methylated 203Hg was significantly higher, in both water and sediment, in the anaerobic systems than in the aerobic systems. The composition and total concentration of fatty acids originating from bacterial phospholipids, as well as the concentration of vitamin B12, including related cobalamins, were similar in sediments from the anaerobic and aerobic systems. Bacterial cell numbers were, on average, 3.6 times higher in the anaerobic water columns than in the aerobic ones. Volatilization of 203Hg occurred in all systems except in an autoclaved control and was of similar magnitudes in the anaerobic and aerobic systems. Incorporation of 203Hg into the sediment was significantly faster in the aerobic systems than in the anaerobic systems. These results suggest that episodes of anoxia in bottom waters and sediment cause an increase in net mercury methylation and, hence, an increase in bioavailable mercury. PMID:16348444

  16. Anaerobic bacteria

    MedlinePlus

    Anaerobic bacteria are bacteria that do not live or grow when oxygen is present. In humans, these bacteria ... Goldstein EJ. Diseases caused by non-spore forming anaerobic bacteria. In: Goldman L, Schafer AI, eds. Goldman's Cecil ...

  17. Anaerobic biodegradation of polylactic acid under mesophilic condition using thermal-alkaline pretreatment

    NASA Astrophysics Data System (ADS)

    Samitthiwetcharong, Sutisa; Kullavanijaya, Pratin; Chavalparit, Orathai

    2017-07-01

    The propose of this study was to investigate the effect of thermal-alkaline pretreatment with emphasis on sodium hydroxide concentration (NaOH), temperature and reaction time, on enhancement of polylactic acid (PLA) films degradation and biogas production. The results found that NaOH concentration and reaction time were two main parameters influencing on PLA degradation. While, less significant was found for temperature. From the Response Surface Methodology (RSM), it was concluded that the optimum pretreatment conditions were at 0.5 M of NaOH, temperature of 60°C and 24 hr of reaction time. This was generated about 3.7 times (215.47 ml/gVSadded) higher gas production comparing to non-pretreated PLA films which was 58.28 ml/gVSadded. The maximum biodegradability of PLA film was 20.14%. This was estimated to be 4.7 times higher than non-pretreated PLA (4.32%). This finding demonstrated the benefit of thermal-alkaline pretreatment on surface of PLA films destruction. Consequently, the microbial enzymes could degrade PLA more easily, resulting in an increase of biogas production.

  18. Influence of Environmental Conditions on Methanogenic Compositions in Anaerobic Biogas Reactors

    PubMed Central

    Karakashev, Dimitar; Batstone, Damien J.; Angelidaki, Irini

    2005-01-01

    The influence of environmental parameters on the diversity of methanogenic communities in 15 full-scale biogas plants operating under different conditions with either manure or sludge as feedstock was studied. Fluorescence in situ hybridization was used to identify dominant methanogenic members of the Archaea in the reactor samples; enriched and pure cultures were used to support the in situ identification. Dominance could be identified by a positive response by more than 90% of the total members of the Archaea to a specific group- or order-level probe. There was a clear dichotomy between the manure digesters and the sludge digesters. The manure digesters contained high levels of ammonia and of volatile fatty acids (VFA) and were dominated by members of the Methanosarcinaceae, while the sludge digesters contained low levels of ammonia and of VFA and were dominated by members of the Methanosaetaceae. The methanogenic diversity was greater in reactors operating under mesophilic temperatures. The impact of the original inoculum used for the reactor start-up was also investigated by assessment of the present population in the reactor. The inoculum population appeared to have no influence on the eventual population. PMID:15640206

  19. The determination of the real nano-scale sizes of bacteria in chernozem during microbial succession by means of hatching of a soil in aerobic and anaerobic conditions

    NASA Astrophysics Data System (ADS)

    Gorbacheva, M.

    2012-04-01

    M.A. Gorbacheva,L.M. Polyanskaya The Faculty of Soil Science, Moscow State University, Leninskie Gory, GSP-1, Moscow,119991,Russia In recent years there's been particular attention paid to the smallest life's forms- bacteria which size can be measured in nanometer. These are the forms of bacteria with diameter of 5-200 nm. Theoretical calculations based on the content of the minimum number of DNA, enzyme, lipids in and ribosome in cells indicates impossibility of existence of a living cells within diameter less than 300 nm. It is theoretically possible for a living cell to exist within possible diameter of approximately 140 nm. Using a fluorescence microscope there's been indicated in a number of samples from lakes, rivers, soil, snow and rain water that 200 nm is the smallest diameter of a living cell. Supposingly, such a small size of bacteria in soil is determined by natural conditions which limit their development by nutritious substances and stress-factors. Rejuvenescence of nanobacteria under unfavourable natural conditions and stress-factors is studied in laboratory environment. The object of the current study has become the samples of typical arable chernozem of the Central Chernozem State Biosphere Reserve in Kursk. The detailed morphological description of the soil profile and its basic analytical characteristics are widely represented in scientific publications. The soil is characterized by a high carbon content which makes up 3,96% ,3,8% , and 2,9% for the upper layers of the A horizon, and 0,79% for the layer of the B horizon. A microbial succession was studied under aerobic and anaerobic conditions by means of experiments with microcosms in upper A horizons and B horizon of a chernozem. The final aim is to identify the cells size of bacteria in aerobic and anaerobic soil conditions in chernozem during the microbial succession, by dampening and application of chitin by means of «cascade filtration» method. The study of the microcosms is important for

  20. Effects of temperature on anaerobic decomposition of high-molecular weight organic matter under sulfate-reducing conditions

    NASA Astrophysics Data System (ADS)

    Matsui, Takato; Kojima, Hisaya; Fukui, Manabu

    2013-03-01

    Most sedimentary mineralization occurs along coasts under anaerobic conditions. In the absence of oxygen, high-molecular weight organic matter in marine sediments is gradually decomposed by hydrolysis, fermentation and sulfate reduction. Because of the different responses of the respective steps to temperature, degradation may be specifically slowed or stopped in certain step. To evaluate the effect of temperature on cellobiose degradation, culture experiments were performed at six different temperatures (3 °C, 8 °C, 13 °C, 18 °C, 23 °C, and 28 °C) under sulfate-reducing conditions. This study measured the concentrations of sulfide, dissolved organic carbon (DOC), and organic acids during that degradation. Degradation patterns were divided into three temperature groups: 3 °C, 8/13 °C, and 18/23/28 °C. The decrease in DOC proceeded in two steps, except at 3 °C. The length of the stagnant phase separating these two steps differed greatly between temperatures of 8/13 °C and 18/23/28 °C. In the first step, organic carbon was consumed by hydrolysis, fermentation and sulfate reduction. In the second step, acetate accumulated during the first step was oxidized by sulfate reduction. Bacterial communities in the cultures were analyzed by denaturing gradient gel electrophoresis (DGGE); the major differences among the three temperature groups were attributed to shifts in acetate-using sulfate reducers of the genus Desulfobacter. This suggests that temperature characteristics of dominant acetate oxidizers are important factors in determining the response of carbon flow in coastal marine sediments in relation to the changes in temperature.

  1. [Influence of extracellular polymeric substance on enzyme hydrolysis of sludge under anaerobic condition].

    PubMed

    Chen, Wei; Jia, Yuan-Yuan; Zheng, Wei; Li, Xiao-Ming; Zhou, Jun; Yang, Qi; Luo, Kun

    2011-08-01

    The effect of extracellular polymeric substance (EPS) on the enzymatic solubilisation of sludge and the changes of chemical components was investigated. Sludge solubilization with and without EPS was studied in the enzymatic system, and in the normal system without enzyme addition, respectively. The result indicated that only EPS could be hydrolyzed when the enzyme addition less than 20 mg/g, while the cell lysis occurred significantly with the doses of enzymes increasing. Treatment with lysozyme for the original sludge was proved to have a higher hydrolysis efficiency, and the SCOD/TCOD rate reached up to 28.14%. And at the enzyme dosage of 60 mg/g, the VSS removal rate increased to 51.66% and the concentration of DNA attained 68.34 mg/g (calculated by VSS) after 48 h reaction, which were 29.01% and 59.63 mg/g higher than the control test, respectively, and were 24.86% and 53.39 mg/g higher than that with EPS removed in advance, respectively. Meanwhile, NH4+ -N, PO4(3-)-P and SCOD showed high dissolution efficiency, and the maximal concentrations achieved to 503 mg/L, 78.9 mg/L and 3171 mg/L, respectively. After removal of extracellular polymers, higher lysis efficiency was also observed by protease and cellulose, by which VSS reduction rate reached to 49.95% and 39.85%, respectively. The concentration of DNA showed a correlation coefficient of more than 0.9 with the concentrations of SCOD, NH4+ -N and PO4(3-)-P. And the highest hydrolysis rate obtained in 6 hours, which was about 3 hours earlier than the control test. Moreover, under those condition, sludge hydrolyzation could be well realized by only small amount of the enzyme addition.

  2. [High-solids anaerobic co-digestion of sludge and kitchen garbage under mesophilic conditions].

    PubMed

    Duan, Ni-Na; Dong, Bin; Li, Jiang-Hua; Dai, Ling-Ling; Dai, Xiao-Hu

    2013-01-01

    At solid retention time (SRT) of 20 days, biogas production, volatile solid (VS) degradation and system stability in co-digestion systems of dewatered sludge (DS) and kitchen garbage (KG) were investigated in semi-continuous completely mixed reactors numbered R1-R5 (the DS/KG of their feeding substrate based on wet mass was 1:0, 4:1, 3:2, 2:3 and 0:1, respectively). The results showed that, with larger proportion of KG in feeding substrate, higher methane yield and biogas yield were obtained with lower methane content. For certain reactor at given SRT, KG addition could significantly improve the organic loading rate (OLR) and volume biogas production. System with more KG addition favored higher hydraulic constant k and VS reduction. The hydraulic constant k was 0.25 d(-1), 0.61 d(-1), 1.09 d(-1) and 1.56 d(-1), and the VS reduction was 37.4%, 50.6%, 60.7% and 68.2% for R1-R4, respectively, indicating higher hydrolysis rates with more KG addition, which led to increased VS reductions. With larger KG proportion in feeding substrate, pH, total alkalinity (TA), total ammonia nitrogen (TAN) and free ammonia nitrogen (FAN) showed decreasing trend. As KG addition increased by 60%, pH, TA, TAN and FAN decreased by 6%, 16%, 22% and 75%, respectively. FAN and Na+ respectively were potential inhibitory chemicals that threatened the stability of the mono-system of DS and KG. In comparison with the mono-system of DS or KG, the co-system showed higher stability by diluting toxic chemicals like ammonia or Na+ to much lower levels.

  3. Women and Working Conditions: Prospects for Improvement?

    ERIC Educational Resources Information Center

    Seguret, Marie-Claire

    1983-01-01

    Women's difficult working conditions are due to factors such as the nature and form of women's employment, their reproductive role, and family responsibilities. The relative importance of these factors must be assessed in order to redress inequalities. (SK)

  4. Dissolution Coupled Biodegradation of Pce by Inducing In-Situ Biosurfactant Production Under Anaerobic Conditions

    NASA Astrophysics Data System (ADS)

    Dominic, J.; Nambi, I. M.

    2013-12-01

    Biosurfactants have proven to enhance the bioavailability and thereby elevate the rate of degradation of Light Non Aqueous Phase Liquids (LNAPLs) such as crude oil and petroleum derivatives. In spite of their superior characteristics, use of these biomolecules for remediation of Dense Non Aqueous Phase Liquids (DNAPLs) such as chlorinated solvents is still not clearly understood. In this present study, we have investigated the fate of tetrachloroethylene (PCE) by inducing in-situ biosurfactants production, a sustainable option which hypothesizes increase in bioavailability of LNAPLs. In order to understand the effect of biosurfactants on dissolution and biodegradation under the inducement of in-situ biosurfactant production, batch experiments were conducted in pure liquid media. The individual influence of each process such as biosurfactant production, dissolution of PCE and biodegradation of PCE were studied separately for getting insights on the synergistic effect of each process on the fate of PCE. Finally the dissolution coupled biodegradation of non aqueous phase PCE was studied in conditions where biosurfactant production was induced by nitrate limitation. The effect of biosurfactants was differentiated by repeating the same experiments were the biosurfactant production was retarded. The overall effect of in-situ biosurfactant production process was evaluated by use of a mathematical model. The process of microbial growth, biosurfactant production, dissolution and biodegradation of PCE were translated as ordinary differential equations. The modelling exercise was mainly performed to get insight on the combined effects of various processes that determine the concentration of PCE in its aqueous and non-aqueous phases. Model simulated profiles of PCE with the kinetic coefficients evaluated earlier from individual experiments were compared with parameters fitted for observations in experiments with dissolution coupled biodegradation process using optimization

  5. Kinetics of Fe(II)-catalyzed transformation of 6-line ferrihydrite under anaerobic flow conditions

    SciTech Connect

    Yang, L.; Steefel, C.I.; Marcus, M.A.; Bargar, J.R.

    2010-04-01

    The readsorption of ferrous ions produced by the abiotic and microbially-mediated reductive dissolution of iron oxy-hydroxides drives a series of transformations of the host minerals. To further understand the mechanisms by which these transformations occur and their kinetics within a microporous flow environment, flow-through experiments were conducted in which capillary tubes packed with ferrihydrite-coated glass spheres were injected with inorganic Fe(II) solutions under circumneutral pH conditions at 25 C. Synchrotron X-ray diffraction was used to identify the secondary phase(s) formed and to provide data for quantitative kinetic analysis. At concentrations at and above 1.8 mM Fe(II) in the injection solution, magnetite was the only secondary phase formed (no intermediates were detected), with complete transformation following a nonlinear rate law requiring 28 hours and 150 hours of reaction at 18 and 1.8 mM Fe(II), respectively. However, when the injection solution consisted of 0.36 mM Fe(II), goethite was the predominant reaction product and formed much more slowly according to a linear rate law, while only minor magnetite was formed. When the rates are normalized based on the time to react half of the ferrihydrite on a reduced time plot, it is apparent that the 1.8 mM and 18 mM input Fe(II) experiments can be described by the same reaction mechanism, while the 0.36 input Fe(II) experiment is distinct. The analysis of the transformation kinetics suggest that the transformations involved an electron transfer reaction between the aqueous as well as sorbed Fe(II) and ferrihydrite acting as a semiconductor, rather than a simple dissolution and recrystallization mechanism. A transformation mechanism involving sorbed inner sphere Fe(II) alone is not supported, since the essentially equal coverage of sorption sites in the 18 mM and 1.8 mM Fe(II) injections cannot explain the difference in the transformation rates observed.

  6. Contribution of quinone-reducing microorganisms to the anaerobic biodegradation of organic compounds under different redox conditions.

    PubMed

    Cervantes, Francisco J; Gutiérrez, Claudia H; López, Kitzia Y; Estrada-Alvarado, María Isabel; Meza-Escalante, Edna R; Texier, Anne-Claire; Cuervo, Flor; Gómez, Jorge

    2008-04-01

    The capacity of two anaerobic consortia to oxidize different organic compounds, including acetate, propionate, lactate, phenol and p-cresol, in the presence of nitrate, sulfate and the humic model compound, anthraquinone-2,6-disulfonate (AQDS) as terminal electron acceptors, was evaluated. Denitrification showed the highest respiratory rates in both consortia studied and occurred exclusively during the first hours of incubation for most organic substrates degraded. Reduction of AQDS and sulfate generally started after complete denitrification, or even occurred at the same time during the biodegradation of p-cresol, in anaerobic sludge incubations; whereas methanogenesis did not significantly occur during the reduction of nitrate, sulfate, and AQDS. AQDS reduction was the preferred respiratory pathway over sulfate reduction and methanogenesis during the anaerobic oxidation of most organic substrates by the anaerobic sludge studied. In contrast, sulfate reduction out-competed AQDS reduction during incubations performed with anaerobic wetland sediment, which did not achieve any methanogenic activity. Propionate was a poor electron donor to achieve AQDS reduction; however, denitrifying and sulfate-reducing activities carried out by both consortia promoted the reduction of AQDS via acetate accumulated from propionate oxidation. Our results suggest that microbial reduction of humic substances (HS) may play an important role during the anaerobic oxidation of organic pollutants in anaerobic environments despite the presence of alternative electron acceptors, such as sulfate and nitrate. Methane inhibition, imposed by the inclusion of AQDS as terminal electron acceptor, suggests that microbial reduction of HS may also have important implications on the global climate preservation, considering the green-house effects of methane.

  7. Improving the stability of thermophilic anaerobic digesters treating SS-OFMSW through enrichment with compost and leachate seeds.

    PubMed

    Ghanimeh, Sophia; El-Fadel, Mutasem; Saikaly, Pascal

    2013-03-01

    This paper examines the potential of improving the stability of thermophilic anaerobic digestion of source-sorted organic fraction of municipal solid waste (SS-OFMSW) by adding leachate and compost during inoculation. For this purpose, two stable thermophilic digesters, A (control) and B (with added leachate and compost), were subjected to a sustained substrate shock by doubling the organic loading rate for one week. Feeding was suspended then gradually resumed to reach the pre-shock loading rate (2 gVS/l/d). Digester A failed, exhibiting excessive increase in acetate and a corresponding decrease in pH and methane generation, and lower COD and solids removal efficiencies. In contrast, digester B was able to restore its functionality with 90% recovery of pre-shock methane generation rate at stable pH, lower hydrogen levels, and reduced VFAs and ammonia accumulation.

  8. A Primer on Improving Contingent Faculty Conditions

    ERIC Educational Resources Information Center

    McGrew, Heidi; Untener, Joe

    2010-01-01

    Challenges associated with the increasing use of contingent faculty appointments in American higher education are mounting. The AAUP and other professional groups have identified several major problems: (1) unacceptable conditions and compensation for contingent faculty members; (2) poor learning outcomes for students; and (3) the potential…

  9. A Primer on Improving Contingent Faculty Conditions

    ERIC Educational Resources Information Center

    McGrew, Heidi; Untener, Joe

    2010-01-01

    Challenges associated with the increasing use of contingent faculty appointments in American higher education are mounting. The AAUP and other professional groups have identified several major problems: (1) unacceptable conditions and compensation for contingent faculty members; (2) poor learning outcomes for students; and (3) the potential…

  10. Comprehensive analysis of glucose and xylose metabolism in Escherichia coli under aerobic and anaerobic conditions by (13)C metabolic flux analysis.

    PubMed

    Gonzalez, Jacqueline E; Long, Christopher P; Antoniewicz, Maciek R

    2017-01-01

    Glucose and xylose are the two most abundant sugars derived from the breakdown of lignocellulosic biomass. While aerobic glucose metabolism is relatively well understood in E. coli, until now there have been only a handful of studies focused on anaerobic glucose metabolism and no (13)C-flux studies on xylose metabolism. In the absence of experimentally validated flux maps, constraint-based approaches such as MOMA and RELATCH cannot be used to guide new metabolic engineering designs. In this work, we have addressed this critical gap in current understanding by performing comprehensive characterizations of glucose and xylose metabolism under aerobic and anaerobic conditions, using recent state-of-the-art techniques in (13)C metabolic flux analysis ((13)C-MFA). Specifically, we quantified precise metabolic fluxes for each condition by performing parallel labeling experiments and analyzing the data through integrated (13)C-MFA using the optimal tracers [1,2-(13)C]glucose, [1,6-(13)C]glucose, [1,2-(13)C]xylose and [5-(13)C]xylose. We also quantified changes in biomass composition and confirmed turnover of macromolecules by applying [U-(13)C]glucose and [U-(13)C]xylose tracers. We demonstrated that under anaerobic growth conditions there is significant turnover of lipids and that a significant portion of CO2 originates from biomass turnover. Using knockout strains, we also demonstrated that β-oxidation is critical for anaerobic growth on xylose. Quantitative analysis of co-factor balances (NADH/FADH2, NADPH, and ATP) for different growth conditions provided new insights regarding the interplay of energy and redox metabolism and the impact on E. coli cell physiology.

  11. Improvement of dairy manufacture effluent anaerobic digestion with biological waste addition using a Chinese dome digester.

    PubMed

    Jihen, Toumi; Hassib, Bouallagui; Moktar, Hamdi; Said, Nouira

    2010-05-01

    Anaerobic co-digestion of dairy manufacture effluent (DME) and biological waste (BW) was investigated at various DME/BW ratios using laboratory batch digesters. The biogas yield ranged 0.34-0.88l biogas g(-1) volatile solids (VS) removed. The highest VS reductions of 58% and 62% were obtained for DME/BW ratios of 60:40% and 80:20%, respectively. Results were used to operate a pilot-scale digester of 5m(3). The highest biogas yield of 0.48lg(-1) VS removed was obtained at an organic loading rate (OLR) of 1.64gVSl(-1)d(-1) corresponding to a DME/BW ratio of 80:20%. This could be mainly attributed to the higher biodegradability of DME and the correction of the C:N ratio by the addition of the BW. The N, P and K contents were increased significantly in the TS of the digestate to be around 6.8%, 0.64% and 1.26%, respectively.

  12. CO2 fixation by anaerobic non-photosynthetic mixotrophy for improved carbon conversion.

    PubMed

    Jones, Shawn W; Fast, Alan G; Carlson, Ellinor D; Wiedel, Carrissa A; Au, Jennifer; Antoniewicz, Maciek R; Papoutsakis, Eleftherios T; Tracy, Bryan P

    2016-09-30

    Maximizing the conversion of biogenic carbon feedstocks into chemicals and fuels is essential for fermentation processes as feedstock costs and processing is commonly the greatest operating expense. Unfortunately, for most fermentations, over one-third of sugar carbon is lost to CO2 due to the decarboxylation of pyruvate to acetyl-CoA and limitations in the reducing power of the bio-feedstock. Here we show that anaerobic, non-photosynthetic mixotrophy, defined as the concurrent utilization of organic (for example, sugars) and inorganic (for example, CO2) substrates in a single organism, can overcome these constraints to increase product yields and reduce overall CO2 emissions. As a proof-of-concept, Clostridium ljungdahlii was engineered to produce acetone and achieved a mass yield 138% of the previous theoretical maximum using a high cell density continuous fermentation process. In addition, when enough reductant (that is, H2) is provided, the fermentation emits no CO2. Finally, we show that mixotrophy is a general trait among acetogens.

  13. CO2 fixation by anaerobic non-photosynthetic mixotrophy for improved carbon conversion

    PubMed Central

    Jones, Shawn W.; Fast, Alan G.; Carlson, Ellinor D.; Wiedel, Carrissa A.; Au, Jennifer; Antoniewicz, Maciek R.; Papoutsakis, Eleftherios T.; Tracy, Bryan P.

    2016-01-01

    Maximizing the conversion of biogenic carbon feedstocks into chemicals and fuels is essential for fermentation processes as feedstock costs and processing is commonly the greatest operating expense. Unfortunately, for most fermentations, over one-third of sugar carbon is lost to CO2 due to the decarboxylation of pyruvate to acetyl-CoA and limitations in the reducing power of the bio-feedstock. Here we show that anaerobic, non-photosynthetic mixotrophy, defined as the concurrent utilization of organic (for example, sugars) and inorganic (for example, CO2) substrates in a single organism, can overcome these constraints to increase product yields and reduce overall CO2 emissions. As a proof-of-concept, Clostridium ljungdahlii was engineered to produce acetone and achieved a mass yield 138% of the previous theoretical maximum using a high cell density continuous fermentation process. In addition, when enough reductant (that is, H2) is provided, the fermentation emits no CO2. Finally, we show that mixotrophy is a general trait among acetogens. PMID:27687501

  14. Reducing agitation energy-consumption by improving rheological properties of corn stover substrate in anaerobic digestion.

    PubMed

    Tian, Libin; Shen, Fei; Yuan, Hairong; Zou, Dexun; Liu, Yanping; Zhu, Baoning; Li, Xiujin

    2014-09-01

    Rheological properties of corn stover substrate were investigated to explore agitation energy reduction potential for different total solid (TS) in anaerobic digestion. The effects of particle size and temperature on rheological properties and corresponding energy reduction were studied. The results indicated that corn stover slurry exhibited pseudo-plastic flow behavior at TS of 4.23-7.32%, and was well described by Power-law model. At TS of 4.23%, rheological properties were not obviously affected by particle size and temperature. However, when TS was increased to 7.32%, there was 10.37% shear stress reduction by size-reduction from 20 to 80-mesh, and 11.73% shear stress reduction by temperature-increase from 25 to 55 °C. PTS was advanced as variations of power consumption by TS-increase from 4.23% to 7.32%. There was 9.2% PTS-reduction by size-reduction from 20 to 80-mesh at 35 °C. Moreover, PTS-reduction of 10.3%/10 °C was achieved at 20-mesh compared with 9.0%/10 °C at 80-mesh. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Hydrogen Photoproduction by Nutrient-Deprived Chalamydomonas reinhardtii Cells Immobilized Within Thin Alginate Films Under Aerobic and Anaerobic Conditions

    SciTech Connect

    Kosourov, S. N.; Seibert, M.

    2009-01-01

    A new technique for immobilizing H{sub 2}-photoproducing green algae within a thin (<400 {micro}m) alginate film has been developed. Alginate films with entrapped sulfur/phosphorus-deprived Chlamydomonas reinhardtii, strain cc124, cells demonstrate (a) higher cell density (up to 2,000 {micro}g Chl mL{sup -1} of matrix), (b) kinetics of H{sub 2} photoproduction similar to sulfur-deprived suspension cultures, (c) higher specific rates (up to 12.5 {micro}mol mg{sup -1} Chl h{sup -1}) of H{sub 2} evolution, (d) light conversion efficiencies to H{sub 2} of over 1% and (e) unexpectedly high resistance of the H{sub 2}-photoproducing system to inactivation by atmospheric O{sub 2}. The algal cells, entrapped in alginate and then placed in vials containing 21% O{sub 2} in the headspace, evolved up to 67% of the H{sub 2} gas produced under anaerobic conditions. The results indicate that the lower susceptibility of the immobilized algal H{sub 2}-producing system to inactivation by O{sub 2} depends on two factors: (a) the presence of acetate in the medium, which supports higher rates of respiration and (b) the capability of the alginate polymer itself to effectively separate the entrapped cells from O{sub 2} in the liquid and headspace and restrict O{sub 2} diffusion into the matrix. The strategy presented for immobilizing algal cells within thin polymeric matrices shows the potential for scale-up and possible future applications.

  16. Performance evaluation of a completely stirred anaerobic reactor treating pig manure at a low range of mesophilic conditions

    SciTech Connect

    Guo, Jianbin; Dong, Renjie; Clemens, Joachim; Wang, Wei

    2013-11-15

    Highlights: • The biogas process can run stably at 20 °C at extremely low OLR after long-term acclimation of bacteria. • A biogas plant running at 28 °C seems as efficient as that operated at 38 °C at low OLR of 1.3 g ODM L{sup −1} d{sup −1}. • Lower temperature operation is inadvisable for the commercial biogas plant running at rather high OLR. • The estimated sludge yield at 28 °C is higher than that at 38 °C. - Abstract: Many Chinese biogas plants run in the lower range of mesophilic conditions. This study evaluated the performance of a completely stirred anaerobic reactor treating pig manure at different temperatures (20, 28 and 38 °C). The start-up phase of the reactor at 20 °C was very long and extremely poor performance was observed with increasing organic loading rate (OLR). At an OLR of 4.3 g ODM L{sup −1} d{sup −1}, methane production at 28 °C was comparable (3% less) with that at 38 °C, but the risk of acidification was high at 28 °C. At low OLR (1.3 g ODM L{sup −1} d{sup −1}), the biogas process appeared stable at 28 °C and gave same methane yields as compared to the reactor operating at 38 °C. The estimated sludge yield at 28 °C was 0.065 g VSS g{sup −1} COD{sub removed,} which was higher than that at 38 °C (0.016 g VSS g{sup −1} COD{sub removed})

  17. Purification and characterization of a catalase from photosynthetic bacterium Rhodospirillum rubrum S1 grown under anaerobic conditions.

    PubMed

    Kang, Yoon-Suk; Lee, Dong-Heon; Yoon, Byoung-Jun; Oh, Duck-Chul

    2006-04-01

    The photosynthetic bacterium, Rhodospirillum rubrum S1, when grown under anaerobic conditions, generated three different types of catalases. In this study, we purified and characterized the highest molecular weight catalase from the three catalases. The total specific catalase activity of the crude cell extracts was 88 U/mg. After the completion of the final purification step, the specific activity of the purified catalase was 1,256 U/mg. The purified catalase evidenced an estimated molecular mass of 318 kDa, consisting of four identical subunits, each of 79 kDa. The purified enzyme exhibited an apparent Km value of 30.4 mM and a Vmax of 2,564 U against hydrogen peroxide. The enzyme also exhibited a broad optimal pH (5.0-9.0), and remained stable over a broad temperature range (20 degrees C-60 degrees C). It maintained 90% activity against organic solvents (ethanol/chloroform) known hydroperoxidase inhibitors, and exhibited no detectable peroxidase activity. The catalase activity of the purified enzyme was reduced to 19% of full activity as the result of the administration of 10 mM 3-amino-1,2,4-triazole, a heme-containing catalase inhibitor. Sodium cyanide, sodium azide, and hydroxylamine, all of which are known heme protein inhibitors, inhibited catalase activity by 50% at concentrations of 11.5 microM, 0.52 microM, and 0.11 microM, respectively. In accordance with these findings, the enzyme was identified as a type of monofunctional catalase.

  18. Effect of anaerobic and stationary phase growth conditions on the heat shock and oxidative stress responses in Escherichia coli K-12.

    PubMed

    Díaz-Acosta, Alondra; Sandoval, María L; Delgado-Olivares, Luis; Membrillo-Hernández, Jorge

    2006-06-01

    The natural living style of Escherichia coli occurs in the gastrointestinal tract, where most of its existence is spent under anaerobic conditions and in stationary phase of growth. Here we report on the heat shock response of E. coli K-12 cells growing in the presence or absence of oxygen. An rpoH mutant (impaired in the synthesis of the sigma(32) transcriptional factor) exhibited an increased sensitivity to heat shock but only in the exponential phase of aerobic growth, suggesting that in anaerobic growth conditions, and in aerobic stationary phase, sigma(32)-independent mechanisms are playing a prime role in protecting cells from heat stress. Our results demonstrated that sigma(S) is not involved in this protection system. Studies on the kinetics of synthesis of Heat shock proteins (Hsp) after an abrupt rise in temperature demonstrated that in the absence of oxygen, the synthesis of Hsp is triggered faster and is sustained for a longer period of time compared to aerobic growth conditions. Finally, the heated cells in the exponential phase of aerobic growth displayed a high concentration of oxidatively damaged proteins in the presence of 4 mM H(2)O(2), in sharp contrast to cultures of stationary phase or anaerobic growth.

  19. Modeling microbial ethanol production by E. coli under aerobic/anaerobic conditions: applicability to real postmortem cases and to postmortem blood derived microbial cultures.

    PubMed

    Boumba, Vassiliki A; Kourkoumelis, Nikolaos; Gousia, Panagiota; Economou, Vangelis; Papadopoulou, Chrissanthy; Vougiouklakis, Theodore

    2013-10-10

    The mathematical modeling of the microbial ethanol production under strict anaerobic experimental conditions for some bacterial species has been proposed by our research group as the first approximation to the quantification of the microbial ethanol production in cases where other alcohols were produced simultaneously with ethanol. The present study aims to: (i) study the microbial ethanol production by Escherichia coli under controlled aerobic/anaerobic conditions; (ii) model the correlation between the microbial produced ethanol and the other higher alcohols; and (iii) test their applicability in: (a) real postmortem cases that had positive BACs (>0.10 g/L) and co-detection of higher alcohols and 1-butanol during the original ethanol analysis and (b) postmortem blood derived microbial cultures under aerobic/anaerobic controlled experimental conditions. The statistical evaluation of the results revealed that the formulated models were presumably correlated to 1-propanol and 1-butanol which were recognized as the most significant descriptors of the modeling process. The significance of 1-propanol and 1-butanol as descriptors was so powerful that they could be used as the only independent variables to create a simple and satisfactory model. The current models showed a potential for application to estimate microbial ethanol - within an acceptable standard error - in various tested cases where ethanol and other alcohols have been produced from different microbes.

  20. Improving solids retention in upflow anaerobic sludge blanket reactors at low temperatures using lamella settlers.

    PubMed

    Halalsheh, Maha M; Muhsen, Hussien H; Shatanawi, Khaldoun M; Field, Jim A

    2010-01-01

    Lamella settlers were used to increase sludge concentration in pilot scale UASB reactors treating concentrated sewage at low temperature. The aim was to increase sludge retention time (SRT) and achieve better digestion in UASB reactors without the need for increasing the hydraulic retention time (HRT). Two modified UASB reactors were used for this purpose. In the first reactor, lamella settlers were installed in the settling zone of the UASB reactor and the reactor was named UASB-ESR1. In the second reactor, lamella settlers were installed underneath the gas liquid separator (GLS) and the reactor was named UASB-ESR2. The sludge concentration, sludge profile, and system performance of each reactor were monitored. The obtained sludge concentrations were 50 and 53 g TS/l for UASB-ESR1 and UASB-ESR2, respectively. The measured concentrations were almost double the concentrations reported for conventional UASB reactors ranging 16-26 g TS/l. The calculated SRT in the modified UASB reactors was 103 days in both reactors. The average total COD (COD(tot)) and suspended COD (COD(ss)) removal efficiencies were 38% and 60%, respectively for the UASB-ESR1. The average COD(tot) and COD(ss) removal efficiencies for the UASB-ESR2 were 41% and 62%, respectively. The modified reactors were considered at the startup period and the performances of the modified systems are expected to significantly improve when arriving at steady state conditions.

  1. Influence of aerobic and anaerobic conditions on survival of Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium in Luria-Bertani broth, farm-yard manure and slurry.

    PubMed

    Semenov, Alexander V; van Overbeek, Leo; Termorshuizen, Aad J; van Bruggen, Ariena H C

    2011-03-01

    The influence of aerobic and anaerobic conditions on the survival of the enteropathogens Escherichia coli O157:H7 and Salmonella serovar Typhimurium was investigated in microcosms with broth, cattle manure or slurry. These substrates were inoculated with a green fluorescent protein transformed strain of the enteropathogens at 10(7) cells g(-1) dry weight. Survival data was fitted to the Weibull model. The survival curves in aerobic conditions generally showed a concave curvature, while the curvature was convex in anaerobic conditions. The estimated survival times showed that E. coli O157:H7 survived significantly longer under anaerobic than under aerobic conditions. Survival ranged from approximately. 2 weeks for aerobic manure and slurry to more than six months for anaerobic manure at 16 °C. On average, in 56.3% of the samplings, the number of recovered E. coli O157:H7 cells by anaerobic incubation of Petri plates was significantly (p < 0.05) higher in comparison with aerobic incubation. Survival of Salmonella serovar Typhimurium was not different between aerobic and anaerobic storage of LB broth or manure as well as between aerobic and anaerobic incubation of Petri dishes. The importance of changes in microbial community and chemical composition of manure and slurry was distinguished for the survival of E. coli O157:H7 in different oxygen conditions. Copyright © 2010 Elsevier Ltd. All rights reserved.

  2. Anaerobic thermophiles.

    PubMed

    Canganella, Francesco; Wiegel, Juergen

    2014-02-26

    The term "extremophile" was introduced to describe any organism capable of living and growing under extreme conditions. With the further development of studies on microbial ecology and taxonomy, a variety of "extreme" environments have been found and an increasing number of extremophiles are being described. Extremophiles have also been investigated as far as regarding the search for life on other planets and even evaluating the hypothesis that life on Earth originally came from space. The first extreme environments to be largely investigated were those characterized by elevated temperatures. The naturally "hot environments" on Earth range from solar heated surface soils and water with temperatures up to 65 °C, subterranean sites such as oil reserves and terrestrial geothermal with temperatures ranging from slightly above ambient to above 100 °C, to submarine hydrothermal systems with temperatures exceeding 300 °C. There are also human-made environments with elevated temperatures such as compost piles, slag heaps, industrial processes and water heaters. Thermophilic anaerobic microorganisms have been known for a long time, but scientists have often resisted the belief that some organisms do not only survive at high temperatures, but actually thrive under those hot conditions. They are perhaps one of the most interesting varieties of extremophilic organisms. These microorganisms can thrive at temperatures over 50 °C and, based on their optimal temperature, anaerobic thermophiles can be subdivided into three main groups: thermophiles with an optimal temperature between 50 °C and 64 °C and a maximum at 70 °C, extreme thermophiles with an optimal temperature between 65 °C and 80 °C, and finally hyperthermophiles with an optimal temperature above 80 °C and a maximum above 90 °C. The finding of novel extremely thermophilic and hyperthermophilic anaerobic bacteria in recent years, and the fact that a large fraction of them belong to the Archaea has definitely

  3. Anaerobic Thermophiles

    PubMed Central

    Canganella, Francesco; Wiegel, Juergen

    2014-01-01

    The term “extremophile” was introduced to describe any organism capable of living and growing under extreme conditions. With the further development of studies on microbial ecology and taxonomy, a variety of “extreme” environments have been found and an increasing number of extremophiles are being described. Extremophiles have also been investigated as far as regarding the search for life on other planets and even evaluating the hypothesis that life on Earth originally came from space. The first extreme environments to be largely investigated were those characterized by elevated temperatures. The naturally “hot environments” on Earth range from solar heated surface soils and water with temperatures up to 65 °C, subterranean sites such as oil reserves and terrestrial geothermal with temperatures ranging from slightly above ambient to above 100 °C, to submarine hydrothermal systems with temperatures exceeding 300 °C. There are also human-made environments with elevated temperatures such as compost piles, slag heaps, industrial processes and water heaters. Thermophilic anaerobic microorganisms have been known for a long time, but scientists have often resisted the belief that some organisms do not only survive at high temperatures, but actually thrive under those hot conditions. They are perhaps one of the most interesting varieties of extremophilic organisms. These microorganisms can thrive at temperatures over 50 °C and, based on their optimal temperature, anaerobic thermophiles can be subdivided into three main groups: thermophiles with an optimal temperature between 50 °C and 64 °C and a maximum at 70 °C, extreme thermophiles with an optimal temperature between 65 °C and 80 °C, and finally hyperthermophiles with an optimal temperature above 80 °C and a maximum above 90 °C. The finding of novel extremely thermophilic and hyperthermophilic anaerobic bacteria in recent years, and the fact that a large fraction of them belong to the Archaea has

  4. APOLLO 10: Improvments in Living Conditions

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Living conditions were superior on this flight to any previously. From the film documentary 'APOLLO 10: 'Green Light for a Lunar Landing''. Part of a documentary series made in the early 70's on the APOLLO missions, and narrated by Burgess Meredith. (Actual date created is not known at this time) APOLLO 10: Manned lunar orbital flight with Thomas P Stafford, John W. Young, and Eugene A. Cernan to test all aspects of an actual manned lunar landing except the landing. Mission Duration 192hrs 3mins 23 sec

  5. Anaerobic fermentation of agricultural residue: potential for improvement and implementation. Final report, Volume II

    SciTech Connect

    Jewell, W. J.; Dell'orto, S.; Fanfoni, K. J.; Hayes, T. D.; Leuschner, A. P.; Sherman, D. F.

    1980-04-01

    Earlier studies have shown that although large quantities of agricultural residues are generated on small farms, it was difficult to economically justify use of conventional anaerobic digestion technology, such as used for sewage sludge digestion. A simple, unmixed, earthen-supported structure appeared to be capable of producing significant quantities of biogas at a cost that would make it competitive with many existing fuels. The goal of this study was to define and demonstrate a methane fermentation technology that could be practical and economically feasible on small farms. This study provides the first long term, large scale (reactor volumes of 34 m/sup 3/) parallel testing of the major theory, design, construction, and operation of a low cost approach to animal manure fermentation as compared to the more costly and complex designs. The main objectives were to define the lower limits for successful fermentor operation in terms of mixing, insulation, temperature, feed rate, and management requirements in a cold climate with both pilot scale and full scale fermentors. Over a period of four years, innovative fermentation processes for animal manures were developed from theoretical concept to successful full scale demonstration. Reactors were sized for 50 to 65 dairy animals, or for the one-family dairy size. The results show that a small farm biogas generation system that should be widely applicable and economically feasible was operated successfully for nearly two years. Although this low cost system out-performed the completely mixed unit throughout the study, perhaps the greatest advantage of this approach is its ease of modification, operation, and maintenance.

  6. Decrease of U(VI) Immobilization Capability of the Facultative Anaerobic Strain Paenibacillus sp. JG-TB8 under Anoxic Conditions Due to Strongly Reduced Phosphatase Activity

    PubMed Central

    Reitz, Thomas; Rossberg, Andre; Barkleit, Astrid; Selenska-Pobell, Sonja; Merroun, Mohamed L.

    2014-01-01

    Interactions of a facultative anaerobic bacterial isolate named Paenibacillus sp. JG-TB8 with U(VI) were studied under oxic and anoxic conditions in order to assess the influence of the oxygen-dependent cell metabolism on microbial uranium mobilization and immobilization. We demonstrated that aerobically and anaerobically grown cells of Paenibacillus sp. JG-TB8 accumulate uranium from aqueous solutions under acidic conditions (pH 2 to 6), under oxic and anoxic conditions. A combination of spectroscopic and microscopic methods revealed that the speciation of U(VI) associated with the cells of the strain depend on the pH as well as on the aeration conditions. At pH 2 and pH 3, uranium was exclusively bound by organic phosphate groups provided by cellular components, independently on the aeration conditions. At higher pH values, a part (pH 4.5) or the total amount (pH 6) of the dissolved uranium was precipitated under oxic conditions in a meta-autunite-like uranyl phosphate mineral phase without supplying an additional organic phosphate substrate. In contrast to that, under anoxic conditions no mineral formation was observed at pH 4.5 and pH 6, which was clearly assigned to decreased orthophosphate release by the cells. This in turn was caused by a suppression of the indigenous phosphatase activity of the strain. The results demonstrate that changes in the metabolism of facultative anaerobic microorganisms caused by the presence or absence of oxygen can decisively influence U(VI) biomineralization. PMID:25157416

  7. Anaerobic thermophilic bacteria isolated from a Venezuelan oil field and its potential use in microbial improved oil recovery

    SciTech Connect

    Trebbau, G.; Fernandez, B.; Marin, A.

    1995-12-31

    The objective of this work is to determine the ability of indigenous bacteria from a Venezuelan oil field to grow under reservoir conditions inside a porous media, and to produce metabolites capable of recovering residual crude oil. For this purpose, samples of formation waters from a central-eastern Venezuelan oil reservoir were enriched with different carbon sources and a mineral basal media. Formation water was used as a source of trace metals. The enrichments obtained were incubated at reservoir temperature (71{degrees}C), reservoir pressure (1,200 psi), and under anaerobic conditions for both outside and inside porous media (Berea core). Growth and metabolic activity was followed outside porous media by measuring absorbance at 660 nm, increases in pressure, and decreases in pH. Inside porous media bacterial activity was determined by visual examination of the produced waters (gas bubbles and bacterial cells). All the carbohydrates tested outside porous media showed good growth at reservoir conditions. The pH was lowered, gases such as CO{sub 2} and CH{sub 4} were identified by GC. Surface tension was lowered in some enrichments by 30% when compared to controls. Growth was decreased inside porous media, but gases were produced and helped displace oil. In addition, 10% residual oil was recovered from the Berea core. Mathematical modeling was applied to the laboratory coreflood experiment to evaluate the reproducibility of the results obtained.

  8. Effect of anaerobic soil disinfestation and vermicompost on soilborne phytopathogenic agents under tree-crop nursery conditions

    USDA-ARS?s Scientific Manuscript database

    Anaerobic soil disinfestation (ASD) is a fumigation-independent management strategy for controlling soilborne pathogens. Walnut nurseries currently employ preplant fumigation to control soilborne phytopathogens and weeds, and may be amenable to use ASD instead. We investigated the potential of ASD a...

  9. 43 CFR 4120.3-1 - Conditions for range improvements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Conditions for range improvements. 4120.3... LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR RANGE MANAGEMENT (4000) GRAZING ADMINISTRATION-EXCLUSIVE OF ALASKA Grazing Management § 4120.3-1 Conditions for range improvements. (a) Range improvements shall...

  10. Biostimulation of anaerobic BTEX biodegradation under fermentative methanogenic conditions at source-zone groundwater contaminated with a biodiesel blend (B20).

    PubMed

    Ramos, Débora Toledo; da Silva, Márcio Luis Busi; Chiaranda, Helen Simone; Alvarez, Pedro J J; Corseuil, Henry Xavier

    2013-06-01

    Field experiments were conducted to assess the potential for anaerobic biostimulation to enhance BTEX biodegradation under fermentative methanogenic conditions in groundwater impacted by a biodiesel blend (B20, consisting of 20 % v/v biodiesel and 80 % v/v diesel). B20 (100 L) was released at each of two plots through an area of 1 m(2) that was excavated down to the water table, 1.6 m below ground surface. One release was biostimulated with ammonium acetate, which was added weekly through injection wells near the source zone over 15 months. The other release was not biostimulated and served as a baseline control simulating natural attenuation. Ammonium acetate addition stimulated the development of strongly anaerobic conditions, as indicated by near-saturation methane concentrations. BTEX removal began within 8 months in the biostimulated source zone, but not in the natural attenuation control, where BTEX concentrations were still increasing (due to source dissolution) 2 years after the release. Phylogenetic analysis using quantitative PCR indicated an increase in concentration and relative abundance of Archaea (Crenarchaeota and Euryarchaeota), Geobacteraceae (Geobacter and Pelobacter spp.) and sulfate-reducing bacteria (Desulfovibrio, Desulfomicrobium, Desulfuromusa, and Desulfuromonas) in the biostimulated plot relative to the control. Apparently, biostimulation fortuitously enhanced the growth of putative anaerobic BTEX degraders and associated commensal microorganisms that consume acetate and H2, and enhance the thermodynamic feasibility of BTEX fermentation. This is the first field study to suggest that anaerobic-methanogenic biostimulation could enhance source zone bioremediation of groundwater aquifers impacted by biodiesel blends.

  11. Anaerobic digestate from biogas production as a resource for improving soil fertility: effects on crop yield and soil properties

    NASA Astrophysics Data System (ADS)

    Pastorelli, Roberta; Lagomarsino, Alessandra; Vignozzi, Nadia; Valboa, Giuseppe; Papini, Rossella; Fabiani, Arturo; Simoncini, Stefania; Mocali, Stefano; Piccolo, Raimondo

    2013-04-01

    Soil fertility is fundamental in determining crops productivity in all farming systems. Production of biogas through anaerobic digestion of energy crops generates residues that can represent a valuable resource to sustain and improve soil fertility and to increase soil organic matter content. Residues from anaerobic digestion contain organic fractions and available nutrients, that can thus be returned to the cultivation soil as fertilizer and soil conditioner. However, some unknown aspects of digested residues utilization remain to explore: i) the nutrient supply and the real potential for mineral fertilization substitution, ii) the impact on the structure and functioning of soil microbial communities, iii) the direct and indirect effects on soil structure, organic matter and C mineralization. The aim of the present research was to gain a better understanding of these aspects, evaluating the effects of anaerobic digestate application on soil properties and maize yield. With the main focus of comparing mineral fertilization (250 Kg N ha-1) with digested residues addition (at the dose of 25 % and 50 % of mineral fertilizer), a triplicate sets of plots were designed in a field experiment on a silty-clay loam soil in the southern Po Valley (Italy). The amount of applied residues was calculated according to its N content in order to fertilizer each plots with the same amount of total nitrogen. Residues from digestion showed a N content of 0.4 % (60 % as N-NH4) and a C/N ratio of 3. Changes in soil quality after residues application were studied with a holistic approach, involving microbiological, physical and chemical aspects of soil fertility. In particular, we determined: the abundance and diversity of bacterial and fungal soil communities; the soil organic matter content, its distribution within soil aggregates and the C mineralization potential; cation exchange capacity; the main macro and micro nutrients; bulk density; aggregate stability. No significant

  12. Biochemical and Structural Studies of NADH-Dependent FabG Used To Increase the Bacterial Production of Fatty Acids under Anaerobic Conditions

    PubMed Central

    Javidpour, Pouya; Pereira, Jose H.; Goh, Ee-Been; McAndrew, Ryan P.; Ma, Suzanne M.; Friedland, Gregory D.; Keasling, Jay D.; Chhabra, Swapnil R.; Adams, Paul D.

    2014-01-01

    Major efforts in bioenergy research have focused on producing fuels that can directly replace petroleum-derived gasoline and diesel fuel through metabolic engineering of microbial fatty acid biosynthetic pathways. Typically, growth and pathway induction are conducted under aerobic conditions, but for operational efficiency in an industrial context, anaerobic culture conditions would be preferred to obviate the need to maintain specific dissolved oxygen concentrations and to maximize the proportion of reducing equivalents directed to biofuel biosynthesis rather than ATP production. A major concern with fermentative growth conditions is elevated NADH levels, which can adversely affect cell physiology. The purpose of this study was to identify homologs of Escherichia coli FabG, an essential reductase involved in fatty acid biosynthesis, that display a higher preference for NADH than for NADPH as a cofactor. Four potential NADH-dependent FabG variants were identified through bioinformatic analyses supported by crystallographic structure determination (1.3- to 2.0-Å resolution). In vitro assays of cofactor (NADH/NADPH) preference in the four variants showed up to ∼35-fold preference for NADH, which was observed with the Cupriavidus taiwanensis FabG variant. In addition, FabG homologs were overexpressed in fatty acid- and methyl ketone-overproducing E. coli host strains under anaerobic conditions, and the C. taiwanensis variant led to a 60% higher free fatty acid titer and 75% higher methyl ketone titer relative to the titers of the control strains. With further engineering, this work could serve as a starting point for establishing a microbial host strain for production of fatty acid-derived biofuels (e.g., methyl ketones) under anaerobic conditions. PMID:24212572

  13. Anaerobic Infections

    MedlinePlus

    ... doses of antibiotics taken by mouth for months. Bacteroides and Prevotella infections. Bacterial organisms from species called Bacteroides and Prevotella are anaerobic. They are common organisms ...

  14. Tenax extraction for exploring rate-limiting factors in methyl-β-cyclodextrin enhanced anaerobic biodegradation of PAHs under denitrifying conditions in a red paddy soil.

    PubMed

    Sun, Mingming; Ye, Mao; Hu, Feng; Li, Huixin; Teng, Ying; Luo, Yongming; Jiang, Xin; Kengara, Fredrick Orori

    2014-01-15

    The effectiveness of anaerobic bioremediation systems for PAH-contaminated soil may be constrained by low contaminants bioaccessibility due to limited aqueous solubility and lack of suitable electron acceptors. Information on what is the rate-limiting factor in bioremediation process is of vital importance in the decision in what measures can be taken to assist the biodegradation efficacy. In the present study, four different microcosms were set to study the effect of methyl-β-cyclodextrin (MCD) and nitrate addition (N) on PAHs biodegradation under anaerobic conditions in a red paddy soil. Meanwhile, sequential Tenax extraction combined with a first-three-compartment model was employed to evaluate the rate-limiting factors in MCD enhanced anaerobic biodegradation of PAHs. Microcosms with both 1% (w/w) MCD and 20mM N addition produced maximum biodegradation of total PAHs of up to 61.7%. It appears rate-limiting factors vary with microcosms: low activity of degrading microorganisms is the vital rate-limiting factor for control and MCD addition treatments (CK and M treatments); and lack of bioaccessible PAHs is the main rate-limiting factor for nitrate addition treatments (N and MN treatments). These results have practical implications for site risk assessment and cleanup strategies.

  15. Oxygen-Insensitive Nitroreductases NfsA and NfsB of Escherichia coli Function under Anaerobic Conditions as Lawsone-Dependent Azo Reductases

    PubMed Central

    Rau, Jörg; Stolz, Andreas

    2003-01-01

    Quinones can function as redox mediators in the unspecific anaerobic reduction of azo compounds by various bacterial species. These quinones are enzymatically reduced by the bacteria and the resulting hydroquinones then reduce in a purely chemical redox reaction the azo compounds outside of the cells. Recently, it has been demonstrated that the addition of lawsone (2-hydroxy-1,4-naphthoquinone) to anaerobically incubated cells of Escherichia coli resulted in a pronounced increase in the reduction rates of different sulfonated and polymeric azo compounds. In the present study it was attempted to identify the enzyme system(s) responsible for the reduction of lawsone by E. coli and thus for the lawsone-dependent anaerobic azo reductase activity. An NADH-dependent lawsone reductase activity was found in the cytosolic fraction of the cells. The enzyme was purified by column chromatography and the amino-terminal amino acid sequence of the protein was determined. The sequence obtained was identical to the sequence of an oxygen-insensitive nitroreductase (NfsB) described earlier from this organism. Subsequent biochemical tests with the purified lawsone reductase activity confirmed that the lawsone reductase activity detected was identical with NfsB. In addition it was proven that also a second oxygen-insensitive nitroreductase of E. coli (NfsA) is able to reduce lawsone and thus to function under adequate conditions as quinone-dependent azo reductase. PMID:12788749

  16. Biodegradation of polyacrylamide by anaerobic digestion under mesophilic condition and its performance in actual dewatered sludge system.

    PubMed

    Dai, Xiaohu; Luo, Fan; Yi, Jing; He, Qunbiao; Dong, Bin

    2014-02-01

    Polyacrylamide (PAM) used in sludge dewatering widely exists in high-solid anaerobic digestion. Degradation of polyacrylamide accompanied with accumulation of its toxic monomer is important to disposition of biogas residues. The potential of anaerobic digestion activity in microbial utilization of PAM was investigated in this study. The results indicated that the utilization rate of PAM (as nitrogen source) was influenced by accumulation of ammonia, while cumulative removal of amide group was accorded with zeroth order reaction in actual dewatered system. The adjoining amide group can combined into ether group after biodegradation. PAM can be broken down in different position of its carbon chain backbone. In actual sludge system, the hydrolytic PAM was liable to combined tyrosine-rich protein to form colloid complex, and then consumed as carbon source to form monomer when easily degradable organics were exhausted. The accumulation of acrylamide was leveled off ultimately, accompanied with the yield of methane. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. Impact of high external circulation ratio on the performance of anaerobic reactor treating coal gasification wastewater under thermophilic condition.

    PubMed

    Jia, Shengyong; Han, Hongjun; Zhuang, Haifeng; Hou, Baolin; Li, Kun

    2015-09-01

    A laboratory-scale external circulation anaerobic reactor (ECAR) was developed to treat actual coal gasification wastewater. The external circulation ratio (R) was selected as the main operating variable for analysis. From the results, with the hydraulic retention time of 50h, pH > 8.0 and R of 3, the COD, total phenols, volatile phenol and NH4(+)-N removal efficiencies were remarkably increased to 10 ± 2%, 22 ± 5%, 18 ± 1%, and -1 ± 2%, respectively. Besides, increasing R resulted in more transformation from bound extracellular polymeric substances (EPS) to free EPS in the liquid and the particle size distribution of anaerobic granular sludge accumulated in the middle size range of 1.0-2.5mm. Results showed the genus Saccharofermentans dominanted in the ECAR and the bacterial community shift was observed at different external circulation ratio, influencing the pollutants removal profoundly.

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

    PubMed

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

    2016-02-01

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

  19. Positive feedback of crop residue incorporation on dissolved organic carbon contents under anaerobic conditions in temperate rice paddy soils

    NASA Astrophysics Data System (ADS)

    Said-Pullicino, Daniel; Sodano, Marcella; Bertora, Chiara; Lerda, Cristina; Sacco, Dario; Celi, Luisella

    2016-04-01

    Rice paddy soils are generally characterized by large concentrations and fluxes of DOC in comparison to other ecosystems. Our recent studies have shown that the combination of relatively high pore-water DOC concentrations under anoxic soil conditions (>10-20 mg C l-1) and important percolation fluxes of water during field flooding may contribute significant organic C inputs into the subsoil (18-51 g C m-2) over the cropping season. Crop residues incorporated into the soil after harvest represent the main input of organic C into paddy soils, returning about 200-300 g C m-2 y-1 in single-cropped rice paddies. The anaerobic decomposition of these residues may supply important amounts of DOC to soil pore waters. Moreover, the supply of electron donors with the input of residue-derived labile OM may further increase DOC contents by stimulating the microbially-catalyzed reductive dissolution of Fe and Mn oxyhydroxides under anoxic conditions, and release of DOC previously stabilized on the mineral matrix (i.e. positive feedback). This could have important implications on organic C inputs into the subsoil as well as substrate availability for methane production. We therefore hypothesized that crop residue management practices that influence the amount of labile organic matter present in the soil at the time of field flooding may strongly influence soil solution DOC concentrations as well as the positive feedback on the release of soil-derived DOC. We tested this hypothesis at field-scale by evaluating variations in the contents and quality of DOC above and beneath the plough pan over the cropping season as a function of crop residue management practices involving: tillage and crop residue incorporation in spring (SPR), tillage and crop residue incorporation in spring, dry seeding and 1 month delayed flooding (DRY), tillage and crop residue incorporation in autumn (AUT), and straw removal after harvest and tillage in spring (REM). Moreover, we linked changes in DOC

  20. Use of an algal hydrolysate to improve enzymatic hydrolysis of anaerobically digested fiber

    USDA-ARS?s Scientific Manuscript database

    This study investigated the use of acid hydrolyzed algae to enhance the enzymatic hydrolysis of cellulosic biomass. We first characterized wastewater-grown algal samples and determined the optimal conditions (acid concentration, reaction temperature, and reaction time) for algal hydrolysis using di...

  1. Anaerobic respiration and antioxidant responses of Corythucha ciliata (Say) adults to heat-induced oxidative stress under laboratory and field conditions.

    PubMed

    Ju, Rui-Ting; Wei, He-Ping; Wang, Feng; Zhou, Xu-Hui; Li, Bo

    2014-03-01

    High temperature often induces oxidative stress and antioxidant response in insects. This phenomenon has been well documented under controlled laboratory conditions, but whether it happens under fluctuating field conditions is largely unknown. In this study, we used an invasive lace bug (Corythucha ciliata) as a model species to compare the effects of controlled thermal treatments (2 h at 33-43 °C with 2 °C intervals in the laboratory) and naturally fluctuating thermal conditions (08:00-14:00 at 2-h intervals (29.7-37.2 °C) on a hot summer day in a field in Shanghai, China) on lipid peroxidation (malondialdehyde (MDA) was the marker) and anaerobic respiration (lactate dehydrogenase (LDH) was the marker), as well as superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and glutathione reductase (GR). The results show that MDA concentration increased significantly in response to heat stresses with similar trend in the laboratory and field. LDH activities did not significantly vary across temperatures in the laboratory-exposed individuals, but they significantly increased by rising temperature in the field. The activities or concentrations of SOD, CAT, GSH, and GR all significantly increased with increasing temperature in the two populations. These findings indicate that high temperature induces oxidative stress, resulting in high anaerobic respiration and antioxidant defenses in C. ciliata under both the laboratory and field conditions, which likely provide a defense mechanism against oxidative damage due to the accumulation of ROS.

  2. Improving methane production and phosphorus release in anaerobic digestion of particulate saline sludge from a brackish aquaculture recirculation system.

    PubMed

    Zhang, Xuedong; Ferreira, Rui B; Hu, Jianmei; Spanjers, Henri; van Lier, Jules B

    2014-06-01

    In this study, batch tests were conducted to examine the effects of trehalose and glycine betaine as well as potassium on the specific methanogenic activity (SMA), acid and alkaline phosphatase activity of anaerobic biomass and phosphorus release in anaerobic digestion of saline sludge from a brackish recirculation aquaculture system. The results of ANOVA and Tukey's HSD (honestly significant difference) tests showed that glycine betaine and trehalose enhanced SMA of anaerobic biomass and reactive phosphorus release from the particulate waste. Moreover, SMA tests revealed that methanogenic sludge, which was long-term acclimatized to a salinity level of 17 g/L was severely affected by the increase in salinity to values exceeding 35 g/L. Addition of compatible solutes, such as glycine betaine and trehalose, could be used to enhance the specific methane production rate and phosphorus release in anaerobic digestion from particulate organic waste produced in marine or brackish aquaculture recirculation systems.

  3. Model experiments on improving nitrogen removal in laboratory scale subsurface constructed wetlands by enhancing the anaerobic ammonia oxidation.

    PubMed

    Paredes, D; Kuschk, P; Stange, F; Müller, R A; Köser, H

    2007-01-01

    Anaerobic ammonia oxidation (Anammox) has been identified as a new general process-strategy for nitrogen removal in wastewater treatment. In order to evaluate the role and effects of the Anammox process in wetlands, laboratory-scale model experiments were performed with planted fixed bed reactors. A reactor (planted with Juncus effusus) was fed with synthetic wastewater containing 150-200 mg L(-1) NH4+ and 75-480 mg L(-1) NO2(-). Under these operating conditions, the plants were affected by the high ammonia and nitrite concentrations and the nitrogen removal rate fell within the same range of 45-49 mg N d(-1) (equivalent to 0.64-0.70 g Nm(-2)d(-1)) as already reported by other authors. In order to stimulate the rate of nitrogen conversion, the planted reactor was inoculated with Anammox biomass. As a result, the rate of nitrogen removal was increased 4-5-fold and the toxic effects on the plants also disappeared. The results show that, in principle, subsurface flow wetlands can also function as an "Anammox bioreactor". However, the design of a complete process for the treatment of waters with a high ammonia load and, in particular, the realisation of simple technical solutions for partial nitrification have still to be developed.

  4. Review of feedstock pretreatment strategies for improved anaerobic digestion: From lab-scale research to full-scale application.

    PubMed

    Carrere, Hélène; Antonopoulou, Georgia; Affes, Rim; Passos, Fabiana; Battimelli, Audrey; Lyberatos, Gerasimos; Ferrer, Ivet

    2016-01-01

    When properly designed, pretreatments may enhance the methane potential and/or anaerobic digestion rate, improving digester performance. This paper aims at providing some guidelines on the most appropriate pretreatments for the main feedstocks of biogas plants. Waste activated sludge was firstly investigated and implemented at full-scale, its thermal pretreatment with steam explosion being most recommended as it increases the methane potential and digestion rate, ensures sludge sanitation and the heat needed is produced on-site. Regarding fatty residues, saponification is preferred for enhancing their solubilisation and bioavailability. In the case of animal by-products, this pretreatment can be optimised to ensure sterilisation, solubilisation and to reduce inhibition linked to long chain fatty acids. With regards to lignocellulosic biomass, the first goal should be delignification, followed by hemicellulose and cellulose hydrolysis, alkali or biological (fungi) pretreatments being most promising. As far as microalgae are concerned, thermal pretreatment seems the most promising technique so far. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

    PubMed

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

    2016-11-01

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

  6. Full-scale demonstration of step feed concept for improving an anaerobic/anoxic/aerobic nutrient removal process.

    PubMed

    Ge, Shijian; Zhu, Yunpeng; Lu, Congcong; Wang, Shuying; Peng, Yongzhen

    2012-09-01

    A small wastewater treatment plant (WWTP) failed to meet effluent requirements of the first-A discharge standard in China, with the anaerobic/anoxic/oxic (A/A/O) process treating municipal and partial industrial wastewater. Thus an A/O step feed process (Anoxic/oxic/anoxic/oxic/anoxic/oxic) with floating plastic carriers in aerobic units was proposed to improve nutrient removal within the existing WWTP. Four main reform strategies were applied: (1) the original influent was divided into three streams which led into corresponding anoxic units; (2) floating plastic carriers were placed in the second and third oxic units; (3) nitrified liquid recycling was omitted; (4) channel shapes and sizes were adjusted between adjacent units to prevent backflow. After these modifications were implemented, the total nitrogen and phosphorus concentrations in the effluent were reduced from 20.8 to 14.2mg/L, and from 1.89 to 0.57 mg/L, respectively. Moreover, annual electricity consumption in the WWTP was reduced by 245 MWh as a result of these modifications.

  7. Improved anaerobic digestion of a thermally pretreated mixture of physicochemical sludge; broiler excreta and sugar cane wastes (SCW): Effect on organic matter solubilization, biodegradability and bioenergy production.

    PubMed

    Nava-Valente, Noemí; Alvarado-Lassman, Alejandro; Nativitas-Sandoval, Liliana S; Mendez-Contreras, Juan M

    2016-01-01

    Thermal pretreatment effect of a mixture of organic wastes (physicochemical sludge, excreta of broiler chickens and sugarcane wastes (SCW)) in the solubilization and biodegradability organic matter as well as bioenergy production by anaerobic digestion was evaluated. Two different mixtures of physicochemical sludge, excreta of broiler chickens and SCW (70%, 15%, 15% and 60%, 20%, 20% of VS, respectively) were treated at different temperatures (80 °C, 85 °C and 90 °C) and contact time (30, 60 and 90 min). Results indicate that, organic matter solubilization degree increased from 1.14 to 6.56%; subsequently, in the anaerobic digestion process, an increase of 50% in the volatile solids removal and 10% in biogas production was observed, while, retention time decreased from 23 up to 9 days. The results obtained were similar to pilot-scale. In both experimental scales it showed that the synergy produced by the simultaneous anaerobic digestion of different substrates could increase bioenergy production up to 1.3 L bio g(-1) VS removed and 0.82 L CH4 g(-1) VS removed. The treatment conditions presented in this study allow for large residue quantities to be treated and large bioenergy quantities to be produced (10% higher than during conventional treatment) without increasing the anaerobic digester volume.

  8. Improvement of anaerobic digestion of sewage sludge in a wastewater treatment plant by means of mechanical and thermal pre-treatments: Performance, energy and economical assessment.

    PubMed

    Ruffino, Barbara; Campo, Giuseppe; Genon, Giuseppe; Lorenzi, Eugenio; Novarino, Daniel; Scibilia, Gerardo; Zanetti, Mariachiara

    2015-01-01

    Performances of mechanical and low-temperature (<100°C) thermal pre-treatments were investigated to improve the present efficiency of anaerobic digestion (AD) carried out on waste activated sludge (WAS) in the largest Italian wastewater treatment plant (2,300,000p.e.). Thermal pre-treatments returned disintegration rates of one order of magnitude higher than mechanical ones (about 25% vs. 1.5%). The methane specific production increased by 21% and 31%, with respect to untreated samples, for treatment conditions of respectively 70 and 90°C, 3h. Thermal pre-treatments also decreased WAS viscosity. Preliminary energy and economic assessments demonstrated that a WAS final total solid content of 5% was enough to avoid the employment of auxiliary methane for the pre-treatment at 90°C and the subsequent AD process, provided that all the heat generated was transferred to WAS through heat exchangers. Moreover, the total revenues from sale of the electricity produced from biogas increased by 10% with respect to the present scenario. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Improving nutrient fixation and dry matter content of an ammonium-rich anaerobic digestion effluent by struvite formation and clay adsorption.

    PubMed

    Estevez, Maria M; Linjordet, Roar; Horn, Svein J; Morken, John

    2014-01-01

    The anaerobic digestion (AD) of organic wastes that contain nitrogen leads to its mineralization, yielding a digestate rich in ammonium (NH(4)(+)), an important fertilizing nutrient. The applicability of AD digestate as fertilizer can be improved by fixating the nutrients and increasing its dry matter content. Methods for the fixation and recovery of the digestate's NH(4)(+) and possible also PO(4)(3-) include struvite precipitation and adsorption in clay materials such as bentonite. These techniques were tested in batch experiments employing the liquid fraction of a digestate originating from the AD of a substrate mix containing lignocellulose, cattle manure and fish industrial waste. The concentration of NH(4)(+)-N in this digestate was 2,300 mg L⁻¹. Struvite precipitation conditions at a molar ratio of 1.2:1:1 (Mg²⁺:NH(4)(+):PO(4)(3-)) and pH 9.5 were best in terms of simultaneous removal of NH(4)(+)-N (88%), PO(4)(3-) (60%) and soluble chemical oxygen demand (44%). Bentonite adsorption gave comparably high removal levels for NH(4)(+)-N (82%) and PO(4)(3-) (52%). Analysis of the precipitates' morphology and elemental composition confirmed their struvite and bentonite nature. Dry matter content was increased from 5.8% in the AD digestate to 27% and 22% in the struvite and bentonite sludges, respectively.

  10. Improve the Anaerobic Biodegradability by Copretreatment of Thermal Alkali and Steam Explosion of Lignocellulosic Waste

    PubMed Central

    Siddhu, Muhammad Abdul Hanan; Li, Jianghao; Zhang, Jiafu; Huang, Yan; Wang, Wen; Chen, Chang; Liu, Guangqing

    2016-01-01

    Effective alteration of the recalcitrance properties like crystallization of cellulose, lignin shield, and interlinking of lignocellulosic biomass is an ideal way to utilize the full-scale potential for biofuel production. This study exhibited three different pretreatment effects to enhance the digestibility of corn stover (CS) for methane production. In this context, steam explosion (SE) and thermal potassium hydroxide (KOH-60°C) treated CS produced the maximal methane yield of 217.5 and 243.1 mL/gvs, which were 40.0% and 56.4% more than untreated CS (155.4 mL/gvs), respectively. Copretreatment of thermal potassium hydroxide and steam explosion (CPTPS) treated CS was highly significant among all treatments and improved 88.46% (292.9 mL/gvs) methane yield compared with untreated CS. Besides, CPTPS also achieved the highest biodegradability up to 68.90%. Three kinetic models very well simulated dynamics of methane production yield. Moreover, scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD) analyses declared the most effective changes in physicochemical properties after CPTPS pretreatment. Thus, CPTPS might be a promising approach to deconstructing the recalcitrance of lignocellulosic structure to improve the biodegradability for AD. PMID:27200370

  11. Improve the Anaerobic Biodegradability by Copretreatment of Thermal Alkali and Steam Explosion of Lignocellulosic Waste.

    PubMed

    Siddhu, Muhammad Abdul Hanan; Li, Jianghao; Zhang, Jiafu; Huang, Yan; Wang, Wen; Chen, Chang; Liu, Guangqing

    2016-01-01

    Effective alteration of the recalcitrance properties like crystallization of cellulose, lignin shield, and interlinking of lignocellulosic biomass is an ideal way to utilize the full-scale potential for biofuel production. This study exhibited three different pretreatment effects to enhance the digestibility of corn stover (CS) for methane production. In this context, steam explosion (SE) and thermal potassium hydroxide (KOH-60°C) treated CS produced the maximal methane yield of 217.5 and 243.1 mL/gvs, which were 40.0% and 56.4% more than untreated CS (155.4 mL/gvs), respectively. Copretreatment of thermal potassium hydroxide and steam explosion (CPTPS) treated CS was highly significant among all treatments and improved 88.46% (292.9 mL/gvs) methane yield compared with untreated CS. Besides, CPTPS also achieved the highest biodegradability up to 68.90%. Three kinetic models very well simulated dynamics of methane production yield. Moreover, scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD) analyses declared the most effective changes in physicochemical properties after CPTPS pretreatment. Thus, CPTPS might be a promising approach to deconstructing the recalcitrance of lignocellulosic structure to improve the biodegradability for AD.

  12. The anaerobic co-digestion of sheep bedding and ⩾ 50% cattle manure increases biogas production and improves biofertilizer quality.

    PubMed

    Cestonaro, Taiana; Costa, Mônica Sarolli Silva de Mendonça; Costa, Luiz Antônio de Mendonça; Rozatti, Marcos Antonio Teofilo; Pereira, Dercio Ceri; Lorin, Higor Eisten Francisconi; Carneiro, Leocir José

    2015-12-01

    Sheep manure pellets are peculiarly shaped as small 'capsules' of limited permeability and thus are difficult to degrade. Fragmentation of manure pellets into a homogeneous mass is important for decomposition by microorganisms, and occurs naturally by physical shearing due to animal trampling, when sheep bedding is used. However, the high lignocellulose content of sheep bedding may limit decomposition of sheep manure. Here, we evaluated if co-digestion of sheep bedding with cattle manure would improve the yield and quality of the useful products of anaerobic digestion of sheep bedding--biogas and biofertilizer--by providing a source of nutrients and readily available carbon. Mixtures of sheep bedding and cattle manure in varying proportions (0%, 25%, 50%, 75%, or 100% cattle manure) were added to 6-L digesters, used in a batch system, and analyzed by uni and multivariate statistical tools. PC1, which explained 64.96% of data variability, can be referred to as 'organic fraction/productivity', because higher rates of organic fraction consumption (COD, cellulose and hemicellulose contents) led to higher digester productivity (biogas production, nutrient concentration, and sample stability changes). Therefore, productivity and organic fraction variables were most influenced by manure mixtures with higher (⩾ 50%) or lower (⩽ 25%) ratios of cattle manure, respectively. Increasing the amount of cattle manure up to 50% enhanced the biogas potential production from 142 L kg(-1)TS (0% of cattle manure) to 165, 171, 160 L biogas kg(-1)TS for the mixtures containing 100%, 75% and 50% of cattle manure, respectively. Our results show that the addition of ⩾ 50% cattle manure to the mixture increases biogas production and improves the quality of the final biofertilizer. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Anaerobic α-amylase production and secretion with fumarate as the final electron acceptor in Saccharomyces cerevisiae.

    PubMed

    Liu, Zihe; Österlund, Tobias; Hou, Jin; Petranovic, Dina; Nielsen, Jens

    2013-05-01

    In this study, we focus on production of heterologous α-amylase in the yeast Saccharomyces cerevisiae under anaerobic conditions. We compare the metabolic fluxes and transcriptional regulation under aerobic and anaerobic conditions, with the objective of identifying the final electron acceptor for protein folding under anaerobic conditions. We find that yeast produces more amylase under anaerobic conditions than under aerobic conditions, and we propose a model for electron transfer under anaerobic conditions. According to our model, during protein folding the electrons from the endoplasmic reticulum are transferred to fumarate as the final electron acceptor. This model is supported by findings that the addition of fumarate under anaerobic (but not aerobic) conditions improves cell growth, specifically in the α-amylase-producing strain, in which it is not used as a carbon source. Our results provide a model for the molecular mechanism of anaerobic protein secretion using fumarate as the final electron acceptor, which may allow for further engineering of yeast for improved protein secretion under anaerobic growth conditions.

  14. Improvement through low cost biofilm carrier in anaerobic tubular digestion in cold climate regions.

    PubMed

    Martí-Herrero, J; Alvarez, R; Rojas, M R; Aliaga, L; Céspedes, R; Carbonell, J

    2014-09-01

    The aim of this research is to evaluate the increase of biogas production with low cost tubular digesters in cold climates using PET rings inside the reactor. Two similar digesters have been operated and monitored in cold weather conditions and have been fed with cow manure. Digester 1 was filled with PET - rings as a biofilm carrier, Digester 2 was kept as a reference. Through the PET - rings the functional surface could be increased by a factor 4.2. The results show that 44% more biogas per Kg SV has been produced with the biofilm carrier in use (0.33 m(3)/kg SV) (reference digester -0.23 m(3)/kg SV), at an organic load rate of 0.26 kg SV/m(3)/d. The thermal performance shows that with an adaptation of the low cost tubular digester the slurry temperature can be raised up to 16.6°C (average) by surrounding temperature of 6.1°C (average) without using any active heating system.

  15. Improved anaerobic digestion performance and biogas production from poultry litter after lowering its nitrogen content.

    PubMed

    Markou, Giorgos

    2015-11-01

    Poultry litter (PL) was pre-treated in order to reduce its nitrogen content and to increase the C/N ratio. The pre-treatment consisted of a first anaerobiosis phase of about 60days in order to accumulate ammonia nitrogen, followed by an ammonia stripping phase by heating the substrate at 80°C for 24h. The digestion was performed with PL and pre-treated PL (TPL) after ammonia stripping as mono-substrate under four total solids loads, i.e. 5%, 10%, 15% and 20%. The TPL after ammonia stripping displayed lower ammonia (62-73%) and VFA (41-65%) concentrations compared to digesters with raw PL, while bio-methane yield increased about 8-124%. Bio-methane yields in the series with TPL after ammonia stripping were about 193, 196, 215 and 147 [Formula: see text] /kgCOD, based on the COD added, for 5%, 10%, 15% and 20% TS load, respectively. The results indicate that lowering nitrogen content using the suggested process improves bio-methane yields significantly. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Relationship between the physiology of Enterobacter agglomerans CNCM 1210 grown anaerobically on glycerol and the culture conditions.

    PubMed

    Barbirato, F; Bories, A

    1997-01-01

    In a preliminary study, levels of activity of enzymes involved in anaerobic glycerol catabolism by Enterobacter agglomerans grown in batch cultures regulated in a pH range of 6.5-8.0 were monitored. That study showed that activities of key enzymes of the downstream metabolism of glycerol--glyceradehyde-3-phosphate dehydrogenase (GAP-DH), lactate dehydrogenase and pyruvate formate lyase--were strongly dependent on the culture pH. To investigate the influence of pH on the physiology of the strain, E. agglomerans was grown anaerobically in a continuous culture supplied with glycerol as the sole carbon source and regulated at pH 8. A complete biochemical analysis was performed and was compared with that previously described for the continuous culture regulated at pH 7. A limitation of the glycolytic flux at the level of GAP-DH was demonstrated at high dilution rate, resulting in an overflow metabolism through the 1,3-propanediol formation pathway. Increasing the specific rate of glycerol consumption also resulted in enhanced lactate production due to limitation by the pyruvate decarboxylation step. Finally, changing the culture pH significantly modified the enzymatic profile of E. agglomerans, and it enabled the stability of the culture to be increased by preventing the accumulation in the fermentation broth of 3-hydroxypropionaldehyde, an inhibitory metabolite, when the glycerol supply was suddenly increased.

  17. Biological sulfate reduction in the acidogenic phase of anaerobic digestion under dissimilatory Fe (III)--reducing conditions.

    PubMed

    Zhang, Jingxin; Zhang, Yaobin; Chang, Jinghui; Quan, Xie; Li, Qi

    2013-04-15

    In this study, a novel approach was developed for sulfate - containing wastewater treatment via dosing Fe₂O₃ in a two - stage anaerobic reactor (A1, S1). The addition of Fe₂O₃ in its second stage i.e. acidogenic sulfate-reducing reactor (S1) resulted in microbial reduction of Fe (III), which significantly enhanced the biological sulfate reduction. In reactor S1, increasing influent sulfate concentration to 1400 mg/L resulted in a higher COD removal (27.3%) and sulfate reduction (57.9%). In the reference reactor without using Fe₂O₃ (S2), the COD and sulfate removal were 15.6% and 29%, respectively. The combined performance of the two-stage anaerobic reactor (A1, S1) also showed a higher COD removal of 74.2%. Denaturing gradient gel electrophoresis (DGGE) and phylogenetic analysis showed that the dominant bacteria with high similarity to IRB species as well as sulfate reducer Desulfovibrio and acidogenic bacteria (AB) were enriched in S1. Quantitative Polymerase Chain Reaction (qPCR) analysis presented a higher proportion of sulfate reducer Desulfovibrio marrakechensis and Fe (III) reducer Iron-reducing bacteria HN54 in S1. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Cooperative Actions of CRP-cAMP and FNR Increase the Fosfomycin Susceptibility of Enterohaemorrhagic Escherichia coli (EHEC) by Elevating the Expression of glpT and uhpT under Anaerobic Conditions

    PubMed Central

    Kurabayashi, Kumiko; Tanimoto, Koichi; Tomita, Haruyoshi; Hirakawa, Hidetada

    2017-01-01

    Bacterial infections to anaerobic site are often hard to be treated because the activity of most of antimicrobials decreases under anaerobic conditions. However, fosfomycin rather provides a greater activity under anaerobic conditions than aerobic conditions. Previously, we found that expression of glpT and uhpT, fosfomycin symporters in enterohaemorrhagic Escherichia coli (EHEC) was upregulated by FNR, a global regulator during the anaerobiosis of the bacterium, which led to increased uptake and susceptibility to this drug. In this study, we showed that expression of glpT and uhpT is induced by CRP-cAMP, the regulator complex under both aerobic and anaerobic conditions. The activity of CRP-cAMP in EHEC was elevated under anaerobic conditions because levels of both CRP and cAMP were higher in the cells when grown anaerobically than those when grown aerobically. Results of expression study using mutants indicated that CRP-cAMP is indispensable for expression of glpT but not uhpT—whereas that of uhpT requires UhpA that is the response regulator composing of two-component system with the sensor kinase, UhpB. The CRP-cAMP protein bound to a region that overlaps RNA polymerase binding site for glpT and region upstream of UhpA binding site for uhpT. FNR bound to a region further upstream of CRP-cAMP binding site on region upstream of the glpT gene. These combined results suggested that increased antibacterial activity of fosfomycin to EHEC under anaerobic conditions is due to activation of FNR and increment of CRP-cAMP activity. Then, FNR enhances the expression of glpT activated by CRP-cAMP while CRP-cAMP and FNR cooperatively aids the action of UhpA to express uhpT to maximum level. PMID:28360903

  19. Complete anaerobic mineralization of pentachlorophenol (PCP) under continuous flow conditions by sequential combination of PCP-dechlorinating and phenol-degrading consortia.

    PubMed

    Li, Zhiling; Yang, Suyin; Inoue, Yasushi; Yoshida, Naoko; Katayama, Arata

    2010-12-01

    Complete mineralization of 50 µM of pentachlorophenol (PCP) was achieved anaerobically under continuous flow conditions using two columns connected in series with a hydraulic retention time of 14.2 days, showing the highest reported mineralization rate yet of 3.5 µM day(-1). The first column, when injected with a reductive PCP dechlorinating consortium, dechlorinated PCP to mainly phenol and traces of 3-chlorophenol (3-CP) using lactate supplied continuously as an electron donor. The second column, with an anaerobic phenol degrading consortium, decomposed phenol and 3-CP under iron-reducing conditions with substantial fermentative degradation of organic compounds. When 20 mM of lactate was introduced into the first column, the phenol degradation activity of the second column was lost in a short period of time, because the amorphous Fe(III) oxide (FeOOH) that had been packed in the column before use was depleted by lactate metabolites, such as acetate and propionate, flowing into the second column from the first column. The complete mineralization of PCP was maintained for a long period by reducing the lactate concentration to 4 mM, effectively extending the longevity of second-column activity with no depletion of FeOOH for more than 200 pore volumes (corresponding to 3,000 days). The carbon balance showed that 50 µM PCP and 4 mM lactate in the influent had transformed to CO(2) (81%) and CH(4) (3%) and had contributed to biomass growth (8%). A comparison of the microbial consortia introduced into the columns and those flowing out from the columns suggested that the introduced population did not flow out during the experiments, although the microbial composition of the phenol column was considered to be affected by the inflow of microbes from the PCP dechlorination column. These results suggest that a sequential combination of reductive dechlorinating and anaerobic oxidizing consortia is useful for anaerobic remediation of chlorinated aromatic compounds in

  20. Isolation of Three New Surface Layer Protein Genes (slp) from Lactobacillus brevis ATCC 14869 and Characterization of the Change in Their Expression under Aerated and Anaerobic Conditions

    PubMed Central

    Jakava-Viljanen, Miia; Åvall-Jääskeläinen, Silja; Messner, Paul; Sleytr, Uwe B.; Palva, Airi

    2002-01-01

    Two new surface layer (S-layer) proteins (SlpB and SlpD) were characterized, and three slp genes (slpB, slpC, and slpD) were isolated, sequenced, and studied for their expression in Lactobacillus brevis neotype strain ATCC 14869. Under different growth conditions, L. brevis strain 14869 was found to form two colony types, smooth (S) and rough (R), and to express the S-layer proteins differently. Under aerobic conditions R-colony type cells produced SlpB and SlpD proteins, whereas under anaerobic conditions S-colony type cells synthesized essentially only SlpB. Anaerobic and aerated cultivations of ATCC 14869 cells in rich medium also resulted in S-layer protein patterns similar to those of the S- and R-colony type cells, respectively. Electron microscopy suggested the presence of only a single S-layer with an oblique structure on the cells of both colony forms. The slpB and slpC genes were located adjacent to each other, whereas the slpD gene was not closely linked to the slpB-slpC gene region. Northern analyses confirmed that both slpB and slpD formed a monocistronic transcription unit and were effectively expressed, but slpD expression was induced under aerated conditions. slpC was a silent gene under the growth conditions tested. The amino acid contents of all the L. brevis ATCC 14869 S-layer proteins were typical of S-layer proteins, whereas their sequence similarities with other S-layer proteins were negligible. The interspecies identity of the L. brevis S-layer proteins was mainly restricted to the N-terminal regions of those proteins. Furthermore, Northern analyses, expression of a PepI reporter protein under the control of the slpD promoter, and quantitative real-time PCR analysis of slpD expression under aerated and anaerobic conditions suggested that, in L. brevis ATCC 14869, the variation of S-layer protein content involves activation of transcription by a soluble factor rather than DNA rearrangements that are typical for most of the S-layer phase

  1. Improved hydrogen production under microaerophilic conditions by overexpression of polyphosphate kinase in Enterobacter aerogenes.

    PubMed

    Lu, Yuan; Zhang, Chong; Lai, Qiheng; Zhao, Hongxin; Xing, Xin-Hui

    2011-02-08

    Effects of different microaerophilic conditions on cell growth, glucose consumption, hydrogen production and cellular metabolism of wild Enterobacter aerogenes strain and polyphosphate kinase (PPK) overexpressing strain were systematically studied in this paper, using NaH(2)PO(4) as the phosphate sources. Under different microaerophilic conditions, PPK-overexpressing strain showed better cell growth, glucose consumption and hydrogen production than the wild strain. In the presence of limited oxygen (2.1%) and by PPK overexpression, the hydrogen production per liter of culture, the hydrogen production per cell and the hydrogen yield per mol of glucose increased by 20.1%, 12.3% and 10.8%, respectively, compared with the wild strain under strict anaerobic conditions. Metabolic analysis showed that the increase of the total hydrogen yield was attributed to the improvement of NADH pathway. The result of more reductive cellular oxidation state balance also further demonstrated that, under proper initial microaerophilic conditions and by PPK overexpression, the cell could adjust the cellular redox states and make more energy flow into hydrogen production pathways.

  2. 43 CFR 4120.3-1 - Conditions for range improvements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR RANGE MANAGEMENT (4000) GRAZING ADMINISTRATION-EXCLUSIVE OF ALASKA Grazing Management § 4120.3-1 Conditions for range improvements. (a) Range improvements shall be... consistent with multiple-use management. (b) Prior to installing, using, maintaining, and/or modifying range...

  3. 43 CFR 4120.3-1 - Conditions for range improvements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR RANGE MANAGEMENT (4000) GRAZING ADMINISTRATION-EXCLUSIVE OF ALASKA Grazing Management § 4120.3-1 Conditions for range improvements. (a) Range improvements shall be... consistent with multiple-use management. (b) Prior to installing, using, maintaining, and/or modifying range...

  4. 43 CFR 4120.3-1 - Conditions for range improvements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR RANGE MANAGEMENT (4000) GRAZING ADMINISTRATION-EXCLUSIVE OF ALASKA Grazing Management § 4120.3-1 Conditions for range improvements. (a) Range improvements shall be... consistent with multiple-use management. (b) Prior to installing, using, maintaining, and/or modifying range...

  5. Effect of alkaline pretreatment on anaerobic digestion of solid wastes

    SciTech Connect

    Lopez Torres, M. Espinosa Llorens, Ma. del C.

    2008-11-15

    The introduction of the anaerobic digestion for the treatment of the organic fraction of municipal solid waste (OFMSW) is currently of special interest. The main difficulty in the treatment of this waste fraction is its biotransformation, due to the complexity of organic material. Therefore, the first step must be its physical, chemical and biological pretreatment for breaking complex molecules into simple monomers, to increase solubilization of organic material and improve the efficiency of the anaerobic treatment in the second step. This paper describes chemical pretreatment based on lime addition (Ca(OH){sub 2}), in order to enhance chemical oxygen demand (COD) solubilization, followed by anaerobic digestion of the OFMSW. Laboratory-scale experiments were carried out in completely mixed reactors, 1 L capacity. Optimal conditions for COD solubilization in the first step of pretreatment were 62.0 mEq Ca(OH){sub 2}/L for 6.0 h. Under these conditions, 11.5% of the COD was solubilized. The anaerobic digestion efficiency of the OFMSW, with and without pretreatment, was evaluated. The highest methane yield under anaerobic digestion of the pretreated waste was 0.15 m{sup 3} CH{sub 4}/kg volatile solids (VS), 172.0% of the control. Under that condition the soluble COD and VS removal were 93.0% and 94.0%, respectively. The results have shown that chemical pretreatment with lime, followed by anaerobic digestion, provides the best results for stabilizing the OFMSW.

  6. Steam explosion pretreatment of wheat straw to improve methane yields: investigation of the degradation kinetics of structural compounds during anaerobic digestion.

    PubMed

    Theuretzbacher, Franz; Lizasoain, Javier; Lefever, Christopher; Saylor, Molly K; Enguidanos, Ramon; Weran, Nikolaus; Gronauer, Andreas; Bauer, Alexander

    2015-03-01

    Wheat straw can serve as a low-cost substrate for energy production without competing with food or feed production. This study investigated the effect of steam explosion pretreatment on the biological methane potential and the degradation kinetics of wheat straw during anaerobic digestion. It was observed that the biological methane potential of the non steam exploded, ground wheat straw (276 l(N) kg VS(-1)) did not significantly differ from the best steam explosion treated sample (286 l(N) kg VS(-1)) which was achieved at a pretreatment temperature of 140°C and a retention time of 60 min. Nevertheless degradation speed was improved by the pretreatment. Furthermore it was observed that compounds resulting from chemical reactions during the pretreatment and classified as pseudo-lignin were also degraded during the anaerobic batch experiments. Based on the rumen simulation technique, a model was developed to characterise the degradation process. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Characteristics, process parameters, and inner components of anaerobic bioreactors.

    PubMed

    Abdelgadir, Awad; Chen, Xiaoguang; Liu, Jianshe; Xie, Xuehui; Zhang, Jian; Zhang, Kai; Wang, Heng; Liu, Na

    2014-01-01

    The anaerobic bioreactor applies the principles of biotechnology and microbiology, and nowadays it has been used widely in the wastewater treatment plants due to their high efficiency, low energy use, and green energy generation. Advantages and disadvantages of anaerobic process were shown, and three main characteristics of anaerobic bioreactor (AB), namely, inhomogeneous system, time instability, and space instability were also discussed in this work. For high efficiency of wastewater treatment, the process parameters of anaerobic digestion, such as temperature, pH, Hydraulic retention time (HRT), Organic Loading Rate (OLR), and sludge retention time (SRT) were introduced to take into account the optimum conditions for living, growth, and multiplication of bacteria. The inner components, which can improve SRT, and even enhance mass transfer, were also explained and have been divided into transverse inner components, longitudinal inner components, and biofilm-packing material. At last, the newly developed special inner components were discussed and found more efficient and productive.

  8. Characteristics, Process Parameters, and Inner Components of Anaerobic Bioreactors

    PubMed Central

    Abdelgadir, Awad; Chen, Xiaoguang; Liu, Jianshe; Xie, Xuehui; Zhang, Jian; Zhang, Kai; Wang, Heng; Liu, Na

    2014-01-01

    The anaerobic bioreactor applies the principles of biotechnology and microbiology, and nowadays it has been used widely in the wastewater treatment plants due to their high efficiency, low energy use, and green energy generation. Advantages and disadvantages of anaerobic process were shown, and three main characteristics of anaerobic bioreactor (AB), namely, inhomogeneous system, time instability, and space instability were also discussed in this work. For high efficiency of wastewater treatment, the process parameters of anaerobic digestion, such as temperature, pH, Hydraulic retention time (HRT), Organic Loading Rate (OLR), and sludge retention time (SRT) were introduced to take into account the optimum conditions for living, growth, and multiplication of bacteria. The inner components, which can improve SRT, and even enhance mass transfer, were also explained and have been divided into transverse inner components, longitudinal inner components, and biofilm-packing material. At last, the newly developed special inner components were discussed and found more efficient and productive. PMID:24672798

  9. Operating conditions influence microbial community structures, elimination of the antibiotic resistance genes and metabolites during anaerobic digestion of cow manure in the presence of oxytetracycline.

    PubMed

    Turker, Gokhan; Akyol, Çağrı; Ince, Orhan; Aydin, Sevcan; Ince, Bahar

    2017-08-29

    The way that antibiotic residues in manure follow is one of the greatest concerns due to its potential negative impacts on microbial communities, the release of metabolites and antibiotic resistant genes (ARGs) into the nature and the loss of energy recovery in anaerobic digestion (AD) systems. This study evaluated the link between different operating conditions, the biodegradation of oxytetracycline (OTC) and the formation of its metabolites and ARGs in anaerobic digesters treating cow manure. Microbial communities and ARGs were determined through the use of quantitative real-time PCR. The biodegradation of OTC and occurrence of metabolites were determined using UV-HPLC and LC/MS/MS respectively. The maximum quantity of resistance genes was also examined at the beginning of AD tests and concentration was in the order of: tetM >tetO. The numbers of ARGs were always higher at high volatile solids (VS) content and high mixing rate. The results of the investigation revealed that relationship between mixing rate and VS content plays a crucial role for elimination of ARGs, OTC and metabolites. This can be attributed to high abundance of microorganisms due to high VS content and their increased contact with elevated mixing rate. An increased interaction between microorganisms triggers the promotion of ARGs. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Random UV-C mutagenesis of Scheffersomyces (formerly Pichia) stipitis NRRL Y-7124 to improve anaerobic growth on lignocellulosic sugars

    USDA-ARS?s Scientific Manuscript database

    Yeast strains for anaerobic conversion of lignocellulosic sugars to ethanol were produced from Scheffersomyces (formerly Pichia) stipitis NRRL Y-7124 using UV-C mutagenesis. Random UV-C mutagenesis potentially produces large numbers of mutations broadly and uniformly over the whole genome to genera...

  11. Identifying proper agitation interval to prevent floating layers formation of corn stover and improve biogas production in anaerobic digestion.

    PubMed

    Tian, Libin; Zou, Dexun; Yuan, Hairong; Wang, Linfeng; Zhang, Xin; Li, Xiujin

    2015-06-01

    Floating tests were conducted in anaerobic digestion with different OLR of corn stover to investigate formation of floating layers and to find proper agitation interval for preventing floating layer formation. Floating layers were formed in the early stage of no-agitation period. The daily biogas production was decreased by 81.87-87.90% in digesters with no agitation and feeding compared with digesters having agitation. Reduction of biogas production was mainly attributed to poor contact of substrate-microorganisms. Agitation intervals of 10 h, 6 h, and 2 h were found to be proper for eliminating floating layer at OLR of 1.44, 1.78 and 2.11 g(TS) L(-1) d(-1), respectively. The proper agitation interval was further validated by anaerobic experiments. It showed that proper agitation interval could not only prevent floating layer formation and achieve high biogas production but also increase energy efficiency of anaerobic digestion. The finding is useful for operating anaerobic digester with corn stover in a cost-effective way. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Improved water quality and reduction of odorous compounds in anaerobic lagoon columns receiving pre-treated pig wastewater

    USDA-ARS?s Scientific Manuscript database

    Large volumes of wastewater from confined pig production are stored in anaerobic lagoons. Control methods are needed to reduce air pollution by foul odors released from these lagoons. In a pilot-scale experiment, we evaluated the effect of pig wastewater pre-treatment on reducing the concentration o...

  13. Sodium nitrite-mediated killing of the major cystic fibrosis pathogens Pseudomonas aeruginosa, Staphylococcus aureus, and Burkholderia cepacia under anaerobic planktonic and biofilm conditions.

    PubMed

    Major, Tiffany A; Panmanee, Warunya; Mortensen, Joel E; Gray, Larry D; Hoglen, Niel; Hassett, Daniel J

    2010-11-01

    A hallmark of airways in patients with cystic fibrosis (CF) is highly refractory, chronic infections by several opportunistic bacterial pathogens. A recent study demonstrated that acidified sodium nitrite (A-NO(2)(-)) killed the highly refractory mucoid form of Pseudomonas aeruginosa, a pathogen that significantly compromises lung function in CF patients (S. S. Yoon et al., J. Clin. Invest. 116:436-446, 2006). Therefore, the microbicidal activity of A-NO(2)(-) (pH 6.5) against the following three major CF pathogens was assessed: P. aeruginosa (a mucoid, mucA22 mutant and a sequenced nonmucoid strain, PAO1), Staphylococcus aureus USA300 (methicillin resistant), and Burkholderia cepacia, a notoriously antibiotic-resistant organism. Under planktonic, anaerobic conditions, growth of all strains except for P. aeruginosa PAO1 was inhibited by 7.24 mM (512 μg ml(-1) NO(2)(-)). B. cepacia was particularly sensitive to low concentrations of A-NO(2)(-) (1.81 mM) under planktonic conditions. In antibiotic-resistant communities known as biofilms, which are reminiscent of end-stage CF airway disease, A-NO(2)(-) killed mucoid P. aeruginosa, S. aureus, and B. cepacia; 1 to 2 logs of cells were killed after a 2-day incubation with a single dose of ∼15 mM A-NO(2)(-). Animal toxicology and phase I human trials indicate that these bactericidal levels of A-NO(2)(-) can be easily attained by aerosolization. Thus, in summary, we demonstrate that A-NO(2)(-) is very effective at killing these important CF pathogens and could be effective in other infectious settings, particularly under anaerobic conditions where bacterial defenses against the reduction product of A-NO(2)(-), nitric oxide (NO), are dramatically reduced.

  14. Anaerobic thermophilic culture system

    DOEpatents

    Ljungdahl, Lars G.; Wiegel, Jurgen K. W.

    1981-01-01

    A mixed culture system of the newly discovered microorganism Thermoanaerobacter ethanolicus ATCC31550 and the microorganism Clostridium thermocellum ATCC31549 is described. In a mixed nutrient culture medium that contains cellulose, these microorganisms have been coupled and cultivated to efficiently ferment cellulose to produce recoverable quantities of ethanol under anaerobic, thermophilic conditions.

  15. Anaerobic digestion process

    SciTech Connect

    Ishida, M.; Haga, R.; Odawara, Y.

    1984-04-10

    First, the organic waste slurry of sewage sludge and/or kitchen garbage is stored in a stable condition after effecting partially thereto a liquefaction treatment in advance by adding liquefying bacteria, and next this slurry is effectively digested anaerobically by way of a liquefaction/gasification-mixed step or a liquefaction/gasification separated step.

  16. Start-up and maturation phases of a full-scale, high-rate anaerobic pond bioreactor(®) plus improved facultative ponds to treat municipal wastewater.

    PubMed

    Peña, M R; Aponte, A; Toro, A F

    2015-01-01

    Results of the start-up and maturation phases of a full-scale, high-rate anaerobic pond bioreactor (HRAPB)(®) plus improved facultative ponds (IFPs) to treat municipal wastewater are presented (CODt: 759 mg L⁻¹, CODf: 219 mg L⁻¹, S-SO(4)(2-): 102 mg L⁻¹, and Cr⁺: 1,500 μgL⁻¹). The start-up of the HRAPB(®) comprised, first, the application of a selective pressure increasing up-flow velocity rates. Second, batch stages between successive rates were allowed until 70% of the initial CODf was removed. The IFPs were left in batch and ended when in-pond Chlorophyll-a concentration reached 800 μgL⁻¹. Subsequently, the system underwent gradual maturation and reached effluent concentrations of CODt: 223 mg L⁻¹, CODf: 50 mg L⁻¹, and Cr⁺: 60 μgL⁻¹. The actual efficiency of the system compared with the expected design efficiency was lower given the characteristics of the influent wastewater biochemical oxygen demand/chemical oxygen demand ratios < 0.4, presence of Cr⁺ >1,000 μgL⁻¹, and variations in both conductivity (500-4,500 μScm⁻¹) and pH (6.5-10.5 units). Nonetheless, the system exhibited an adaptation state in less than 1.5 months and yielded an ST/SV ratio of 0.46, and specific methanogenic activity of 0.43 g-CH4-CODg⁻¹SV⁻¹d⁻¹ for HRAPB(®); the in-pond Chlorophyll-a was on average 1,200 μgL⁻¹ in the IFPs, which demonstrated the robustness of these eco-technologies in tropical conditions.

  17. Anaerobic treatment of rice winery wastewater in an upflow filter packed with steel slag under different hydraulic loading conditions.

    PubMed

    Jo, Yeadam; Kim, Jaai; Hwang, Seokhwan; Lee, Changsoo

    2015-10-01

    Rice-washing drainage (RWD), a strong organic wastewater, was anaerobically treated using an upflow filter filled with blast-furnace slag. The continuous performance of the reactor was examined at varying hydraulic retention times (HRTs). The reactor achieved 91.7% chemical oxygen demand removal (CODr) for a 10-day HRT (0.6 g COD/Ld organic loading rate) and maintained fairly stable performance until the HRT was shortened to 2.2 days (CODr > 84%). Further decreases in HRT caused process deterioration (CODr < 50% and pH < 5.5 for a 0.7-day HRT). The methane production rate increased with decreasing HRT to reach the peak level for a 1.3-day HRT, whereas the yield was significantly greater for 3.4-day or longer HRTs. The substrate removal and methane production kinetics were successfully evaluated, and the generated kinetic models produced good performance predictions. The methanogenic activity of the reactor likely relies on the filter biofilm, with Methanosaeta being the main driver. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Homeostasis of metabolites in Escherichia coli on transition from anaerobic to aerobic conditions and the transient secretion of pyruvate

    PubMed Central

    Yasid, Nur Adeela; Rolfe, Matthew D.; Green, Jeffrey

    2016-01-01

    We have developed a method for rapid quenching of samples taken from chemostat cultures of Escherichia coli that gives reproducible and reliable measurements of extracellular and intracellular metabolites by 1H NMR and have applied it to study the major central metabolites during the transition from anaerobic to aerobic growth. Almost all metabolites showed a gradual change after perturbation with air, consistent with immediate inhibition of pyruvate formate-lyase, dilution of overflow metabolites and induction of aerobic enzymes. Surprisingly, although pyruvate showed almost no change in intracellular concentration, the extracellular concentration transiently increased. The absence of intracellular accumulation of pyruvate suggested that one or more glycolytic enzymes might relocate to the cell membrane. To test this hypothesis, chromosomal pyruvate kinase (pykF) was modified to express either PykF-green fluorescent protein or PykF-FLAG fusion proteins. Measurements showed that PykF-FLAG relocates to the cell membrane within 5 min of aeration and then slowly returns to the cytoplasm, suggesting that on aeration, PykF associates with the membrane to facilitate secretion of pyruvate to maintain constant intracellular levels. PMID:27853594

  19. Subsurface Thermal Energy Storage for Improved Air Conditioning Efficiency

    DTIC Science & Technology

    2016-11-01

    EW-201013) Subsurface Thermal Energy Storage for Improved Air Conditioning Efficiency November 2016 This document has been cleared for public...December 2016 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER 10-C-0027-A Cost and Performance Report. Subsurface Thermal Energy Storage for Improved...distribution is unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT This project involved a field demonstration of subsurface thermal energy storage for

  20. An intestinal parasitic protist, Entamoeba histolytica, possesses a non-redundant nitrogen fixation-like system for iron-sulfur cluster assembly under anaerobic conditions.

    PubMed

    Ali, Vahab; Shigeta, Yasuo; Tokumoto, Umechiyo; Takahashi, Yasuhiro; Nozaki, Tomoyoshi

    2004-04-16

    We have characterized the iron-sulfur (Fe-S) cluster formation in an anaerobic amitochondrial protozoan parasite, Entamoeba histolytica, in which Fe-S proteins play an important role in energy metabolism and electron transfer. A genomewide search showed that E. histolytica apparently possesses a simplified and non-redundant NIF (nitrogen fixation)-like system for the Fe-S cluster formation, composed of only a catalytic component, NifS, and a scaffold component, NifU. Amino acid alignment and phylogenetic analyses revealed that both amebic NifS and NifU (EhNifS and EhNifU, respectively) showed a close kinship to orthologs from epsilon-proteobacteria, suggesting that both of these genes were likely transferred by lateral gene transfer from an ancestor of epsilon-proteobacteria to E. histolytica. The EhNifS protein expressed in E. coli was present as a homodimer, showing cysteine desulfurase activity with a very basic optimum pH compared with NifS from other organisms. Eh-NifU protein existed as a tetramer and contained one stable [2Fe-2S]2+ cluster per monomer, revealed by spectroscopic and iron analyses. Fractionation of the whole parasite lysate by anion exchange chromatography revealed three major cysteine desulfurase activities, one of which corresponded to the EhNifS protein, verified by immunoblot analysis using the specific EhNifS antibody; the other two peaks corresponded to methionine gamma-lyase and cysteine synthase. Finally, ectopic expression of the EhNifS and EhNifU genes successfully complemented, under anaerobic but not aerobic conditions, the growth defect of an Escherichia coli strain, in which both the isc and suf operons were deleted, suggesting that EhNifS and EhNifU are necessary and sufficient for Fe-S clusters of non-nitrogenase Fe-S proteins to form under anaerobic conditions. This is the first demonstration of the presence and biological significance of the NIF-like system in eukaryotes.

  1. TM0486 from the hyperthermophilic anaerobe Thermotoga maritima is a thiamin-binding protein involved in response of the cell to oxidative conditions.

    PubMed

    Dermoun, Zorah; Foulon, Amélie; Miller, Mitchell D; Harrington, Daniel J; Deacon, Ashley M; Sebban-Kreuzer, Corinne; Roche, Philippe; Lafitte, Daniel; Bornet, Olivier; Wilson, Ian A; Dolla, Alain

    2010-07-16

    The COG database was used for a comparative genome analysis with genomes from anaerobic and aerobic microorganisms with the aim of identifying proteins specific to the anaerobic way of life. A total of 33 COGs were identified, five of which correspond to proteins of unknown function. We focused our study on TM0486 from Thermotoga maritima, which belongs to one of these COGs of unknown function, namely COG0011. The crystal structure of the protein was determined at 2 A resolution. The structure adopts a beta alpha beta beta alpha beta ferredoxin-like fold and assembles as a homotetramer. The structure also revealed the presence of a pocket in each monomer that bound an unidentified ligand. NMR and calorimetry revealed that TM0486 specifically bound thiamin with a K(d) of 1.58 microM, but not hydroxymethyl pyrimidine (HMP), which has been implicated as a potential ligand. We demonstrated that the TM0486 gene belongs to the same multicistronic unit as TM0483, TM0484 and TM0485. Although these three genes have been assigned to the transport of HMP, with TM0484 being the periplasmic thiamin/HMP-binding protein and TM0485 and TM0483 the transmembrane and the ATPase components, respectively, our results led us to conclude that this operon encodes an ABC transporter dedicated to thiamin, with TM0486 transporting charged thiamin in the cytoplasm. Given that this transcriptional unit was up-regulated when T. maritima was exposed to oxidative conditions, we propose that, by chelating cytoplasmic thiamin, TM0486 and, by extension, proteins belonging to COG0011 are involved in the response mechanism to stress that could arise during aerobic conditions.

  2. Zymomonas with improved xylose utilization in stress conditions

    DOEpatents

    Caimi, Perry G; Emptage, Mark; Li, Xu; Viitanen, Paul V; Chou, Yat-Chen; Franden, Mary Ann; Zhang, Min

    2013-06-18

    Strains of xylose utilizing Zymomonas with improved xylose utilization and ethanol production during fermentation in stress conditions were obtained using an adaptation method. The adaptation involved continuously growing xylose utilizing Zymomonas in media containing high sugars, acetic acid, ammonia, and ethanol.

  3. Simultaneous Hydrogen and Methane Production Through Multi-Phase Anaerobic Digestion of Paperboard Mill Wastewater Under Different Operating Conditions.

    PubMed

    Farghaly, Ahmed; Tawfik, Ahmed

    2017-01-01

    Multi-phase anaerobic reactor for H2 and CH4 production from paperboard mill wastewater was studied. The reactor was operated at hydraulic retention times (HRTs) of 12, 18, 24, and 36 h, and organic loading rates (OLRs) of 2.2, 1.5, 1.1, and 0.75 kg chemical oxygen demand (COD)/m(3) day, respectively. HRT of 12 h and OLR of 2.2 kg COD/m(3) day provided maximum hydrogen yield of 42.76 ± 14.5 ml/g CODremoved and volumetric substrate uptake rate (-rS) of 16.51 ± 4.43 mg COD/L h. This corresponded to the highest soluble COD/total COD (SCOD/TCOD) ratio of 56.25 ± 3.3 % and the maximum volatile fatty acid (VFA) yield (YVFA) of 0.21 ± 0.03 g VFA/g COD, confirming that H2 was mainly produced through SCOD conversion. The highest methane yield (18.78 ± 3.8 ml/g CODremoved) and -rS of 21.74 ± 1.34 mgCOD/L h were achieved at an HRT of 36 h and OLR of 0.75 kg COD/m(3) day. The maximum hydrogen production rate (HPR) and methane production rate (MPR) were achieved at carbon to nitrogen (C/N) ratio of 47.9 and 14.3, respectively. This implies the important effect of C/N ratio on the distinction between the dominant microorganism bioactivities responsible for H2 and CH4 production.

  4. Persistence and cell culturability of biocontrol strain Pseudomonas fluorescens CHA0 under plough pan conditions in soil and influence of the anaerobic regulator gene anr.

    PubMed

    Mascher, Fabio; Schnider-Keel, Ursula; Haas, Dieter; Défago, Geneviève; Moënne-Loccoz, Yvan

    2003-02-01

    Certain fluorescent pseudomonads can protect plants from soil-borne pathogens, and it is important to understand how these biocontrol agents survive in soil. The persistence of the biocontrol strain Pseudomonas fluorescens CHA0-Rif under plough pan conditions was assessed in non-sterile soil microcosms by counting total cells (immunofluorescence microscopy), intact cells (BacLight membrane permeability test), viable cells (Kogure's substrate-responsiveness test) and culturable cells (colony counts on selective plates) of the inoculant. Viable but non-culturable cells of CHA0-Rif (106 cells g-1 soil) were found in flooded microcosms amended with fermentable organic matter, in which the soil redox potential was low (plough pan conditions), in agreement with previous observations of plough pan samples from a field inoculated with CHA0-Rif. However, viable but non-culturable cells were not found in unamended flooded, amended unflooded or unamended unflooded (i.e. control) microcosms, suggesting that such cells resulted from exposure of CHA0-Rif to a combination of low redox potential and oxygen limitation in soil. CHA0-Rif is strictly aerobic. Its anaerobic regulator ANR is activated by low oxygen concentrations and it controls production of the biocontrol metabolite hydrogen cyanide under microaerophilic conditions. Under plough pan conditions, an anr-deficient mutant of CHA0-Rif and its complemented derivative displayed the same persistence pattern as CHA0-Rif, indicating that anr was not implicated in the formation of viable but non-culturable cells of this strain at the plough pan.

  5. Redesigning Escherichia coli metabolism for anaerobic production of isobutanol.

    PubMed

    Trinh, Cong T; Li, Johnny; Blanch, Harvey W; Clark, Douglas S

    2011-07-01

    Fermentation enables the production of reduced metabolites, such as the biofuels ethanol and butanol, from fermentable sugars. This work demonstrates a general approach for designing and constructing a production host that uses a heterologous pathway as an obligately fermentative pathway to produce reduced metabolites, specifically, the biofuel isobutanol. Elementary mode analysis was applied to design an Escherichia coli strain optimized for isobutanol production under strictly anaerobic conditions. The central metabolism of E. coli was decomposed into 38,219 functional, unique, and elementary modes (EMs). The model predictions revealed that during anaerobic growth E. coli cannot produce isobutanol as the sole fermentative product. By deleting 7 chromosomal genes, the total 38,219 EMs were constrained to 12 EMs, 6 of which can produce high yields of isobutanol in a range from 0.29 to 0.41 g isobutanol/g glucose under anaerobic conditions. The remaining 6 EMs rely primarily on the pyruvate dehydrogenase enzyme complex (PDHC) and are typically inhibited under anaerobic conditions. The redesigned E. coli strain was constrained to employ the anaerobic isobutanol pathways through deletion of 7 chromosomal genes, addition of 2 heterologous genes, and overexpression of 5 genes. Here we present the design, construction, and characterization of an isobutanol-producing E. coli strain to illustrate the approach. The model predictions are evaluated in relation to experimental data and strategies proposed to improve anaerobic isobutanol production. We also show that the endogenous alcohol/aldehyde dehydrogenase AdhE is the key enzyme responsible for the production of isobutanol and ethanol under anaerobic conditions. The glycolytic flux can be controlled to regulate the ratio of isobutanol to ethanol production.

  6. Flue gas conditioning for improved particle collection in electrostatic precipitators

    SciTech Connect

    Durham, M.D.

    1992-01-14

    Electrostatic precipitators (ESP) serve as the primary air pollution control device for the majority of coal-fired utility boilers in the Eastern and Midwestern regions of the United States. Since most of these ESPs are collecting flyash generated from medium- and high-sulfur coal, they are not experiencing operational limitations which are common when treating high-resistivity particles and are performing at an efficiency that is as high as could be expected. However, there are indications that the collection efficiency could be improved with flue gas conditioning. Conditioning is commonly used for solving operational problems associated with high-resistivity dusts. The purpose of conditioning for low- and moderate-resistivity applications is to increase the adhesive characteristics of the dust. Flue gas conditioning that increases particle adhesion has the potential to improve collection efficiency because a large percentage of particulate emissions from a well-performing ESP is due to reentrainment. Improved ESP performance should result if particle reentrainment could be reduced by making the particles more adhesive. This could produce a significant reduction in emissions from and ESP from the Following mechanisms: reduced erosion-type reentrainment; reduced rapping emissions; reduced hopper reentrainment; increased agglomeration of fine particles.

  7. Enhanced anaerobic digestion of food waste by trace metal elements supplementation and reduced metals dosage by green chelating agent [S, S]-EDDS via improving metals bioavailability.

    PubMed

    Zhang, Wanli; Zhang, Lei; Li, Aimin

    2015-11-01

    This study aimed at investigating the effects of trace metals on methane production from food waste and examining the feasibility of reducing metals dosage by ethylenediamine-N,N'-disuccinic acid (EDDS) via improving metals bioavailability. The results indicated that the effects of metal elements highly depended on the supplemental concentrations. Trace metals supplemented under moderate concentrations greatly enhanced the methane yield. However, the excessive supplementation of Fe (1000 mg/L) and Ni (50 mg/L) exhibited the obvious toxicity to methanogens. The combinations of trace metals exhibited remarkable synergistic effects. The supplementation of Fe (100 mg/L) + Co (1 mg/L) + Mo (5 mg/L) + Ni (5 mg/L) obtained the greatest methane yield of 504 mL/g VSadded and the highest increment of 35.5% compared to the reactor without metals supplementation (372 mL/g VSadded). The changes of metals speciation showed the reduction of metals bioavailability during anaerobic digestion, which might weaken the stimulative effects of trace metals. However, the addition of EDDS improved metals bioavailability for microbial uptake and stimulated the activity of methanogens, and therefore, strengthened the stimulative effects of metals on anaerobic digestion of food waste. The batch and semi-continuous experiments confirmed that the addition of EDDS (20 mg/L) bonded to trace metals prior to their supplementation could obtain a 50% reduction of optimal metals dosage. This study provided a feasible method to reduce trace metals dosage without the degeneration of process performance of anaerobic digestion.

  8. Effect of feeding strategy on the stability of anaerobic sequencing batch reactor responses to organic loading conditions.

    PubMed

    Cheong, Dae-Yeol; Hansen, Conly L

    2008-07-01

    The goal of this study was to examine the effect of feeding strategy on the capability for treatment and the stability of an anaerobic sequencing batch reactor (ASBR) under increasing organic loading. The lab-scale ASBR systems were operated at 35 degrees C using synthetic organic wastewater under both batch and fed-batch operational modes with different feed to cycle time (F:C) ratios. Experimental studies were conducted over a wide range of volumetric organic loading rates (VOLRs) (1.524 g COD/l/d) by varying the hydraulic retention time (HRT) (1.25, 2.5, and 5d) and the feed wastewater's COD (3750-30,000 mg/l). With an F:C ratio greater than or equal to 0.42, the fed-batch mode operation showed higher system efficiency in COD removal, volumetric methane production rate (VMPR), and specific methane production rate (SMPR) as compared to those in the batch mode with identical VOLR and HRT. In the fed-batch mode, the COD removals reached 86-95% with VOLR up to 12 g COD/l/d. The maximums for VMPR of 3.17 l CH4/l/d and for SMPR of 1.63 g CH4-COD/g VSS/d were achieved with a VOLR of 12 g COD/l/d at HRTs of 2.5 and 1.25 d, respectively. The fed-batch operation presented a lower concentration of volatile fatty acids (VFAs) than those in the batch operation. A lower concentration of VFAs confirmed the stability and efficiency of the fed-batch mode operation. The specific methanogenic activity (SMA) analysis showed that the VFA-degrading activity of the biomass in the fed-batch mode was higher for acetate and butyrate, and lower for propionate. Determined biomass yield and bacterial decay coefficients in the fed-batch operational mode were 0.05 g VSS/g COD rem and 0.001 d(-1), respectively.

  9. Anaerobic transformation of TNT

    SciTech Connect

    Kulpa, C.F.; Roopathy, R.

    1995-12-31

    Most studies on the microbial metabolism of nitroaromatic compounds have used aerobic tempts to degrade nitroaromatics under aerobic microorganisms. In many cases attempts to degrade nitroaromatics under aerobic conditions results in no mineralization and only superficial modifications of the structure. However, under anaerobic sulfate-reducing conditions, the nitroaromatic compounds undergo a series of reductions with the formation of amino compounds. Trinitrotoluene under sulfate-reducing conditions is reduced to triaminotoluene presumably by the enzyme nitrite reductase, which is commonly found in many Desulfovibrio spp. The removal of nitrate from trinitrotoluene is achieved by a series of reductive reactions with the production of ammonia and toluene by Desulfovibrio sp. (B strain). Similar metabolic processes could be applied to other nitroaromatic compounds like nitrobenzene, nitrobenzoic acids, nitrophenols, and aniline. This presentation will review the data supporting the anaerobic transformation of TNT and other nitroaromatics.

  10. Anaerobic crystallization and initial X-ray diffraction data of biphenyl 2,3-dioxygenase from Burkholderia xenovorans LB400: addition of agarose improved the quality of the crystals.

    PubMed

    Kumar, Pravindra; Gómez-Gil, Leticia; Mohammadi, Mahmood; Sylvestre, Michel; Eltis, Lindsay D; Bolin, Jeffrey T

    2011-01-01

    Biphenyl 2,3-dioxygenase (BPDO; EC 1.14.12.18) catalyzes the initial step in the degradation of biphenyl and some polychlorinated biphenyls (PCBs). BPDOLB400, the terminal dioxygenase component from Burkholderia xenovorans LB400, a proteobacterial species that degrades a broad range of PCBs, has been crystallized under anaerobic conditions by sitting-drop vapour diffusion. Initial crystals obtained using various polyethylene glycols as precipitating agents diffracted to very low resolution (∼8 Å) and the recorded reflections were diffuse and poorly shaped. The quality of the crystals was significantly improved by the addition of 0.2% agarose to the crystallization cocktail. In the presence of agarose, wild-type BPDOLB400 crystals that diffracted to 2.4 Å resolution grew in space group P1. Crystals of the BPDOP4 and BPDORR41 variants of BPDOLB400 grew in space group P2(1).

  11. Improved education in musculoskeletal conditions is necessary for all doctors.

    PubMed Central

    Akesson, Kristina; Dreinhöfer, Karsten E.; Woolf, A. D.

    2003-01-01

    It is likely that everyone will, at some time, suffer from a problem related to the musculoskeletal system, ranging from a very common problem such as osteoarthritis or back pain to severely disabling limb trauma or rheumatoid arthritis. Many musculoskeletal problems are chronic conditions. The most common symptoms are pain and disability, with an impact not only on individuals' quality of life but also, importantly, on people's ability to earn a living and be independent. It has been estimated that one in four consultations in primary care is caused by problems of the musculoskeletal system and that these conditions may account for up to 60% of all disability pensions. In contrast, teaching at undergraduate and graduate levels--and the resulting competence and confidence of many doctors--do not reflect the impact of these conditions on individuals and society. Many medical students do not have any clinical training in assessing patients with bone and joint problems. Under the umbrella of the Bone and Joint Decade 2000-2010, experts from all parts of the world with an interest in teaching have developed recommendations for an undergraduate curriculum to improve the teaching of musculoskeletal conditions in medical schools. The goal for each medical school should be a course in musculoskeletal medicine concentrating on clinical assessment, common outpatient musculoskeletal problems and recognition of emergencies. Improving competency in the management of musculoskeletal problems within primary care settings through improved education is the next aim, but there are needs for improvement for all professionals and at all levels within the health care system. PMID:14710510

  12. Lvad pump speed increase is associated with increased peak exercise cardiac output and vo2, postponed anaerobic threshold and improved ventilatory efficiency.

    PubMed

    Vignati, Carlo; Apostolo, Anna; Cattadori, Gaia; Farina, Stefania; Del Torto, Alberico; Scuri, Silvia; Gerosa, Gino; Bottio, Tomaso; Tarzia, Vincenzo; Bejko, Jonida; Sisillo, Erminio; Nicoli, Flavia; Sciomer, Susanna; Alamanni, Francesco; Paolillo, Stefania; Agostoni, Piergiuseppe

    2017-03-01

    Peak exercise cardiac output (CO) increase is associated with an increase of peak oxygen uptake (VO2), provided that arteriovenous O2 difference [Δ(Ca-Cv)O2] does not decrease. At anaerobic threshold, VO2, is related to CO. We tested the hypothesis that, in heart failure (HF) patients with left ventricular assistance device (LVAD), an acute increase of CO obtained through changes in LVAD pump speed is associated with peak exercise and anaerobic threshold VO2 increase. Fifteen of 20 patients bearing LVAD (Jarvik 2000) enrolled in the study successfully performed peak exercise evaluation. All patients had severe HF as shown by clinical evaluation, laboratory tests, echocardiography, spirometry with alveolar-capillary diffusion, and maximal cardiopulmonary exercise testing (CPET). CPETs with non-invasive CO measurements at rest and peak exercise were done on 2days at LVAD pump speed set randomly at 2 and 4. Increasing LVAD pump speed from 2 to 4 increased CO from 3.4±0.9 to 3.8±1.0L/min (ΔCO 0.4±0.6L/min, p=0.04) and from 5.3±1.3 to 5.9±1.4L/min (ΔCO 0.6±0.7L/min, p<0.01) at rest and peak exercise, respectively. Similarly, VO2 increased from 788±169 to 841±152mL/min (ΔVO2 52±76mL/min, p=0.01) and from 568±116 to 619±124mL/min (ΔVO2 69±96mL/min, p=0.02) at peak exercise and at anaerobic threshold, respectively. Δ(Ca-Cv)O2 did not change significantly, while ventilatory efficiency improved (VE/VCO2 slope from 39.9±5.4 to 34.9±8.3, ΔVE/VCO2 -5.0±6.4, p<0.01). In HF, an increase in CO with a higher LVAD pump speed is associated with increased peak VO2, postponed anaerobic threshold, and improved ventilatory efficiency. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  13. PCB breakdown by anaerobic microorganisms

    SciTech Connect

    Not Available

    1989-03-01

    Recently, altered PCB cogener distribution patterns observed in anaerobic sediment samples from the upper Hudson River are being attributed to biologically mediated reductive dechlorination. The authors report their successful demonstration of biologically mediated reductive dechlorination of an Aroclor mixture. In their investigation, they assessed the ability of microorganisms from PCB-contaminated Hudson River sediments (60-562 ppm PCBs) to dechlorinate Aroclor 1242 under anaerobic conditions by eluting microorganisms from the PCB- contaminated sediments and transferring them to a slurry of reduced anaerobic mineral medium and PCB-free sediments in tightly stoppered bottles. They observed dechlorination to be the most rapid at the highest PCB concentration tried by them.

  14. Improvement of the trace metal composition of medium for nitrite-dependent anaerobic methane oxidation bacteria: Iron (II) and copper (II) make a difference.

    PubMed

    He, Zhanfei; Geng, Sha; Pan, Yawei; Cai, Chaoyang; Wang, Jiaqi; Wang, Liqiao; Liu, Shuai; Zheng, Ping; Xu, Xinhua; Hu, Baolan

    2015-11-15

    Nitrite-dependent anaerobic methane oxidation (n-damo) is a potential bioprocess for treating nitrogen-containing wastewater. This process uses methane, an inexpensive and nontoxic end-product of anaerobic digestion, as an external electron donor. However, the low turnover rate and slow growth rate of n-damo functional bacteria limit the practical application of this process. In the present study, the short- and long-term effects of variations in trace metal concentrations on n-damo bacteria were investigated, and the concentrations of trace metal elements of medium were improved. The results were subsequently verified by a group of long-term inoculations (90 days) and were applied in a sequencing batch reactor (SBR) (84 days). The results indicated that iron (Fe(II)) and copper (Cu(II)) (20 and 10 μmol L(-1), respectively) significantly stimulated the activity and the growth of n-damo bacteria, whereas other trace metal elements, including zinc (Zn), molybdenum (Mo), cobalt (Co), manganese (Mn), and nickel (Ni), had no significant effect on n-damo bacteria in the tested concentration ranges. Interestingly, fluorescence in situ hybridization (FISH) showed that a large number of dense, large aggregates (10-50 μm) of n-damo bacteria were formed by cell adhesion in the SBR reactor after using the improved medium, and to our knowledge this is the first discovery of large aggregates of n-damo bacteria.

  15. Flue gas conditioning for improved particle collection in electrostatic precipitators

    SciTech Connect

    Durham, M.D.

    1992-04-27

    The purpose of this research program is to identify and evaluate a variety of additives capable of increasing particle cohesion which could be used for improving collection efficiency in an ESP. A three-phase screening process will be used to provide the, evaluation of many additives in a logical and cost-effective manner. The three step approach involves the following experimental setups: 1. Provide a preliminary screening in the laboratory by measuring the effects of various conditioning agents on reentrainment of flyash particles in an electric field operating at simulated flue gas conditions. 2. Evaluate the successful additives using a 100 acfm bench-scale ESP operating on actual flue gas. 3. Obtain the data required for scaling up the technology by testing the two or three most promising conditioning agents at the pilot scale.

  16. The possible combinatory effects of acute consumption of caffeine, creatine, and amino acids on the improvement of anaerobic running performance in humans.

    PubMed

    Fukuda, David H; Smith, Abbie E; Kendall, Kristina L; Stout, Jeffrey R

    2010-09-01

    Preexercise nutritional investigations have recently become a popular avenue of examining the interaction of multiple ingredients on exercise and training methods. The critical velocity (CV) test is used to quantify the relationship between total running distance and time to exhaustion (TTE), yielding aerobic (CV) and anaerobic parameters (anaerobic running capacity [ARC]). The purpose of this study was to examine the hypothesis that a preexercise supplement containing caffeine, creatine, and amino acids (Game Time; Corr-Jen Laboratories Inc, Aurora, CO) would positively impact CV and ARC in college-aged men and women. In a single-blind crossover design, 10 participants consumed the preexercise supplement (ACT) or placebo (PL) before each testing session. Each participant completed runs to exhaustion on a treadmill at 110%, 90% (day 1), and 105% and 100% (day 2) of the peak velocity (PV) determined from a graded exercise test. The ACT elicited a 10.8% higher ARC (P = .02) compared with the PL, whereas no difference was found in CV (0.6%, P = .38). The TTE was greater for the ACT than the PL at 110% (ACT = 125.7 ± 9.6 seconds, PL = 117.3 ± 12.6 seconds), 105% (ACT = 156.9 ± 11.0 seconds, PL = 143.8 ± 12.9 seconds), and 100% PV (ACT = 185.7 ± 10.7 seconds, PL = 169.7 ± 12.8 seconds) (P = .01-.04); but there was no difference for the TTE at 90% PV (ACT = 353.5 ± 52.7 seconds, PL = 332.7 ± 54.0 seconds) (P = .08). These findings suggest that the acute ingestion of this preexercise supplement may be an effective strategy for improving anaerobic performance, but appears to have no effect on aerobic power.

  17. Effects of the operational conditions on the production of 1,3-propanediol derived from glycerol in anaerobic granular sludge reactors.

    PubMed

    Nakazawa, Mitsue M; Florencio, Lourdinha; Kato, Mario T; Gavazza, Savia; Sanz, Jose L

    2017-02-01

    The aim of this study has been to produce 1,3-propanediol (1,3-PDO) from glycerol (gly) fermentation by means of a microbial mixed culture (granular sludge), as well as to establish the operational conditions of two up-flow anaerobic sludge blanket (UASB) reactors in order to achieve a maximum 1,3-PDO yield. The UASB reactors with initial pH values set at 6.8 and 5.5 were operated at 30 °C during 165 days. Thirteen variables were previously screened by a Plackett-Burman (PB) design; results showed that yeast extract, MgSO4 and methanogenesis inhibition (by heat shock) showed a positive effect, whereas high glycerol concentration, tryptone and CaCl2 showed a negative impact on the 1,3-PDO produced by glycerol degradation. Following four experimental periods, the highest average yield of 0.43 mol 1,3-PDO mol(-1) gly was achieved when sodium bicarbonate was added to the reactors. Propionate and acetate were also produced and a high microorganism diversity was detected; however, the restrictive operational conditions of the reactors led to the death of the methanogenic archaea. Nevertheless, the continuous production of 1,3-PDO from glycerol within UASB reactors inoculated with granular sludge can be considered highly feasible.

  18. Activated sludge mass reduction and biodegradability of the endogenous residues by digestion under different aerobic to anaerobic conditions: Comparison and modeling.

    PubMed

    Martínez-García, C G; Fall, C; Olguín, M T

    2016-03-01

    This study was performed to identify suitable conditions for the in-situ reduction of excess sludge production by intercalated digesters in recycle-activated sludge (RAS) flow. The objective was to compare and model biological sludge mass reduction and the biodegradation of endogenous residues (XP) by digestion under hypoxic, aerobic, anaerobic, and five intermittent-aeration conditions. A mathematical model based on the heterotrophic endogenous decay constant (bH) and including the biodegradation of XP was used to fit the long-term data from the digesters to identify and estimate the parameters. Both the bH constant (0.02-0.05 d(-1)) and the endogenous residue biodegradation constant (bP, 0.001-0.004 d(-1)) were determined across the different mediums. The digesters with intermittent aeration cycles of 12 h-12 h and 5 min-3 h (ON/OFF) were the fastest, compared to the aerobic reactor. The study provides a basis for rating RAS-digester volumes to avoid the accumulation of XP in aeration tanks. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Anaerobic treatment of tequila vinasses under seasonal operating conditions: start-up, normal operation and restart-up after a long stop and starvation period.

    PubMed

    Jáuregui-Jáuregui, J A; Méndez-Acosta, H O; González-Álvarez, V; Snell-Castro, R; Alcaraz-González, V; Godon, J J

    2014-09-01

    This study examines the performance of an anaerobic fixed-film bioreactor under seasonal operating conditions prevailing in medium and small size Tequila factories: start-up, normal operation and particularly, during the restart-up after a long stop and starvation period. The proposed start-up procedure attained a stable biofilm in a rather short period (28 days) despite unbalanced COD/N/P ratio and the use of non-acclimated inoculum. The bioreactor was restarted-up after being shut down for 6 months during which the inoculum starved. Even when biofilm detachment and bioreactor clogging were detected at the very beginning of restart-up, results show that the bioreactor performed better as higher COD removal and methane yield were attained. CE-SSCP and Q-PCR analyses, conducted on the biofilm prokaryotic communities for each operating condition, confirmed that the high COD removal results after the bioreactor clogging and the severe starvation period were mainly due to the stable archaeal and resilient bacterial populations.

  20. Enhanced biogas production from anaerobic codigestion of solid waste by sonolysis.

    PubMed

    Cesaro, Alessandra; Naddeo, Vincenzo; Amodio, Valeria; Belgiorno, Vincenzo

    2012-05-01

    This paper examines the effectiveness of sonolysis in improving the anaerobic biodegradability of the organic fraction of municipal solid waste coming from mechanical selection, thus enhancing biogas production and energy recovery as well. Methane yield of solid organic material anaerobic digestion is significantly affected by substrate availability that was evaluated, in this investigation, through organic matter solubilisation tests carried out at different conditions of ultrasound treatment. Results show that sonolysis can significantly improve the solubilisation of organic solid waste, thus allowing higher biogas production from anaerobic treatment of sonicated substrates. After 45 days, the biogas produced during anaerobic codigestion tests for the sonicated mixture was 24% higher than untreated one. Therefore, these results can lay the basis for the development of technologies useful to produce high biogas quantities, in order to improve clean energy generation from biowaste. Copyright © 2011 Elsevier B.V. All rights reserved.

  1. Microbial aerobic and anaerobic degradation of acrylamide in sludge and water under environmental conditions--case study in a sand and gravel quarry.

    PubMed

    Guezennec, A G; Michel, C; Ozturk, S; Togola, A; Guzzo, J; Desroche, N

    2015-05-01

    Polyacrylamides (PAMs) are used in sand and gravel quarries as water purification flocculants for recycling process water in a recycling loop system where the flocculants remove fine particles in the form of sludge. The PAM-based flocculants, however, contain residual amounts of acrylamide (AMD) that did not react during the polymerization process. This acrylamide is released into the environment when the sludge is discharged into a settling basin. Here, we explore the microbial diversity and the potential for AMD biodegradation in water and sludge samples collected in a quarry site submitted to low AMD concentrations. The microbial diversity, analyzed by culture-dependent methods and the denaturing gradient gel electrophoresis approach, reveals the presence of Proteobacteria, Cyanobacteria, and Actinobacteria, among which some species are known to have an AMD biodegradation activity. Results also show that the two main parts of the water recycling loop-the washing process and the settling basin-display significantly different bacterial profiles. The exposure time with residual AMD could, thus, be one of the parameters that lead to a selection of specific bacterial species. AMD degradation experiments with 0.5 g L(-1) AMD showed a high potential for biodegradation in all parts of the washing process, except the make-up water. The AMD biodegradation potential in samples collected from the washing process and settling basin was also analyzed taking into account on-site conditions: low (12 °C) and high (25 °C) temperatures reflecting the winter and summer seasons, and AMD concentrations of 50 μg L(-1). Batch tests showed rapid (as little as 18 h) AMD biodegradation under aerobic and anaerobic conditions at both the winter and summer temperatures, although there was a greater lag time before activity started with the AMD biodegradation at 12 °C. This study, thus, demonstrates that bacteria present in sludge and water samples exert an in situ and rapid

  2. Comparative Analysis of Performance and Microbial Characteristics Between High-Solid and Low-Solid Anaerobic Digestion of Sewage Sludge Under Mesophilic Conditions.

    PubMed

    Lu, Qin; Yi, Jing; Yang, Dianhai

    2016-01-01

    High-solid anaerobic digestion of sewage sludge achieves highly efficient volatile solid reduction, and production of volatile fatty acid (VFA) and methane compared with conventional low-solid anaerobic digestion. In this study, the potential mechanisms of the better performance in high-solid anaerobic digestion of sewage sludge were investigated by using 454 high-throughput pyrosequencing and real-time PCR to analyze the microbial characteristics in sewage sludge fermentation reactors. The results obtained by 454 high-throughput pyrosequencing revealed that the phyla Chloroflexi, Bacteroidetes, and Firmicutes were the dominant functional microorganisms in high-solid and low-solid anaerobic systems. Meanwhile, the real-time PCR assays showed that high-solid anaerobic digestion significantly increased the number of total bacteria, which enhanced the hydrolysis and acidification of sewage sludge. Further study indicated that the number of total archaea (dominated by Methanosarcina) in a high-solid anaerobic fermentation reactor was also higher than that in a low-solid reactor, resulting in higher VFA consumption and methane production. Hence, the increased key bacteria and methanogenic archaea involved in sewage sludge hydrolysis, acidification, and methanogenesis resulted in the better performance of high-solid anaerobic sewage sludge fermentation.

  3. Anaerobic Biodegradation Of Methyl tert-Butyl Ether Under Iron-Reducing Conditions In Batch And Continuous-Flow Cultures

    EPA Science Inventory

    The feasibility of biodegradation of the fuel oxygenate methyl tert-butyl ether (MTBE) under iron-reducing conditions was explored in batch and continuous-flow systems. A porous pot completely-mixed reactor was seeded with diverse cultures and operated under iron-reducing...

  4. Anaerobic Biodegradation Of Methyl tert-Butyl Ether Under Iron-Reducing Conditions In Batch And Continuous-Flow Cultures

    EPA Science Inventory

    The feasibility of biodegradation of the fuel oxygenate methyl tert-butyl ether (MTBE) under iron-reducing conditions was explored in batch and continuous-flow systems. A porous pot completely-mixed reactor was seeded with diverse cultures and operated under iron-reducing...

  5. Mitochondria from Dipodascus (Endomyces) magnusii and Yarrowia lipolytica yeasts did not undergo a Ca²⁺-dependent permeability transition even under anaerobic conditions.

    PubMed

    Trendeleva, Tat'yana; Sukhanova, Evgeniya; Ural'skaya, Ludmila; Saris, Nils-Erik; Zvyagilskaya, Renata

    2011-12-01

    In this study we used tightly-coupled mitochondria from Yarrowia lipolytica and Dipodascus (Endomyces) magnusii yeasts. The two yeast strains are good alternatives to Saccharomyces cerevisiae, being aerobes containing well structured mitochondria (thus ensuring less structural limitation to observe their appreciable swelling) and fully competent respiratory chain with three invariantly functioning energy conservation points, including Complex I, that can be involved in induction of the canonical Ca²⁺/P(i)-dependent mitochondrial permeability transition (mPTP pore) with an increased open probability when electron flux increases(Fontaine et al. J Biol Chem 273: 25734–25740, 1998; Bernardi et al. FEBS J 273:2077–2099, 2006). High amplitude swelling and collapse of the membrane potential were used as parameters for demonstrating pore opening. Previously (Kovaleva et al. J Bioenerg Biomembr 41:239–249, 2009; Kovaleva et al. Biochemistry (Moscow) 75: 297–303, 2010) we have shown that mitochondria from Y.lipolytica and D. magnusii were very resistant to the Ca²⁺overload combined with varying concentrations of P(i),palmitic acid, SH-reagents, carboxyatractyloside (an inhibitor of ADP/ATP translocator), as well as depletion of intramitochondrial adenine nucleotide pools, deenergization of mitochondria, and shifting to acidic pH values in the presence of high [P(i)]. Here we subjected yeast mitochondria to other conditions known to induce an mPTP in animal and plant mitochondria, namely to Ca²⁺ overload under hypoxic conditions (anaerobiosis). We were unable to observe Ca²⁺-induced high permeability of the inner membrane of D. magnusii and Y. lipolytica yeast mitochondria under anaerobic conditions, thus suggesting that an mPTP-like pore, if it ever occurs in yeast mitochondria, is not coupled with the Ca²⁺ uptake. The results provide the first demonstration of ATP-dependent energization of yeast mitochondria under conditions of anaerobiosis.

  6. Improvement of anaerobic digestion performance by continuous nitrogen removal with a membrane contactor treating a substrate rich in ammonia and sulfide.

    PubMed

    Lauterböck, B; Nikolausz, M; Lv, Z; Baumgartner, M; Liebhard, G; Fuchs, W

    2014-04-01

    The effect of reduced ammonia levels on anaerobic digestion was investigated. Two reactors were fed with slaughterhouse waste, one with a hollow fiber membrane contractor for ammonia removal and one without. Different organic loading rates (OLR) and free ammonia and sulfide concentrations were investigated. In the reactor with the membrane contactor, the NH4-N concentration was reduced threefold. At a moderate OLR (3.1 kg chemical oxygen demand - COD/m(3)/d), this reactor performed significantly better than the reference reactor. At high OLR (4.2 kg COD/m(3)/d), the reference reactor almost stopped producing methane (0.01 Nl/gCOD). The membrane reactor also showed a stable process with a methane yield of 0.23 Nl/g COD was achieved. Both reactors had predominantly a hydrogenotrophic microbial consortium, however in the membrane reactor the genus Methanosaeta (acetoclastic) was also detected. In general, all relevant parameters and the methanogenic consortium indicated improved anaerobic digestion of the reactor with the membrane. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Anaerobic digestion process

    SciTech Connect

    Ishida, M.; Haga, R.; Odawara, Y.

    1982-10-19

    An algae culture grown on the water from the digested slurry of a biogasification plant serves as a means of removing CO/sub 2/ from the methane stream while purifying the wastewater and providing more biomass for the anaerobic digestion plant. Tested on a sewage-sludge digestion system, the proposed process improved the methane yield by 32% and methane concentration by 53-98 vol % while lowering the concentration of nitrogen and phosphorus in the final water.

  8. Improving medium chain fatty acid productivity using chain elongation by reducing the hydraulic retention time in an upflow anaerobic filter.

    PubMed

    Grootscholten, T I M; Steinbusch, K J J; Hamelers, H V M; Buisman, C J N

    2013-05-01

    The objective of this investigation was to further increase the medium chain fatty acid (MCFA) production rate by reducing the hydraulic retention time (HRT) in an upflow anaerobic filter. The results showed that the volumetric MCFA production rate was increased to 57.4 g MCFA l(-1) d(-1), more than 3 times higher than previous work. Despite the lower MCFA concentrations at 4h HRT, the MCFA selectivity remained above 80%. Extra carbon dioxide additions and higher yeast extract concentrations were required to increase the MCFA production rate. More research related to substrates and (micro)nutrients in mixed culture continuous reactors needs to be performed to reduce yeast extract use in chain elongation.

  9. Improvement of the anaerobic treatment of potato processing wastewater in a UASB reactor by co-digestion with glycerol.

    PubMed

    Ma, Jingxing; Van Wambeke, Mariane; Carballa, Marta; Verstraete, Willy

    2008-05-01

    The effect of three different types of glycerol on the performance of up-flow anaerobic sludge blanket (UASB) reactors treating potato processing wastewater was investigated. High COD removal efficiencies were obtained in both control and supplemented UASB reactors (around 85%). By adding 2 ml glycerol product per liter of raw wastewater, the biogas production could be increased by 0.74 l biogas ml(-1) glycerol product, which leads to energy values in the range of 810-1270 kWh(electric) per m(3) product. Moreover, a better in-reactor biomass yield was observed for the supplemented UASB reactor (0.012 g VSS g(-1) COD(removed)) compared to the UASB control (0.002 g VSS g(-1) COD(removed)), which suggests a positive effect of glycerol on the sludge blanket growth.

  10. Responses of Alnus glutinosa to anaerobic conditions--mechanisms and rate of oxygen flux into the roots.

    PubMed

    Dittert, K; Wötzel, J; Sattelmacher, B

    2006-03-01

    Upon exposure to waterlogged growing conditions two-year-old alder trees reduced total root mass. Roots were concentrated in the uppermost soil horizon, and only few coarse roots penetrated into deeper soil layers. Root porosity was only slightly affected and did not exceed 8 % in fine roots. Porosity of coarse roots was higher (27 %) but unaffected by growing conditions. The stem base area covered by lenticels increased strongly and so did the cross section diameter of the stem base. The latter showed a highly significant correlation with O (2) transport into the roots, measured by a Clark type oxygen electrode. Exposure of the lower 5 cm of the stem base, where lenticels were concentrated, to pure N (2) led to a cessation of O (2) transport, confirming that lenticels were the major site of air entry into the stem. In alder plants grown under waterlogged conditions, temperature had a pronounced effect on O (2) gas exchange of the root system. The temperature compensation point, i.e., the temperature where O (2) transport equals O (2) consumption by respiration, was 10.5 degrees C for the entire root system, when measured in a range of 0.15 - 0.20 mmol dissolved O (2) L (-1), which is typical for an open water surface equilibrated with air. O (2) net flow was inversely related to O (2) concentration in the rooting media, indicating that higher root and microbial respiration induced higher net fluxes of O (2) into the root system. With 0.04 mmol dissolved O (2) L (-1) nutrient solution, the temperature compensation point increased to 20 degrees C. Measurement of O (2) gradients in the rhizosphere of agar-embedded roots using O (2) microelectrodes showed a preference for O (2) release in the tip region of coarse roots. Increasing stem temperature over air temperature by 5 degrees C stimulated O (2) flux into the roots as suggested by the model of thermo-osmotic gas transport. However determination of stem and air temperature in a natural alder swamp in northern

  11. Anaerobic codigestion of the mechanically sorted organic fraction of a municipal solid waste with cattle manure in packed microcosms under batch conditions.

    PubMed

    Bertin, L; Todaro, D; Bettini, C; Fava, F

    2008-01-01

    Packed microcosms, consisting of 0.6 L-flask filled with tire chips (TC, a non-cost-recyclable non-biodegradable material) or ceramic cubes, were employed in the wet batch mesophilic anaerobic codigestion of a mechanically sorted organic fraction of a municipal solid waste with cattle manure. Two different waste mixtures were digested within four successive batch experiments, performed by collecting the digested waste and by refilling each microcosm with the same experimental mixture. Methane production yields related to the first experiment were comparable to those of non-packed identically developed microcosms, while they significantly grew during all the following experiences. No CH4-production lag-phase was observed since the second batch experiment. Similar results were obtained for both packing materials: however, the highest methane yields were achieved within bioreactors packed with TC in the presence of a mixture in which the volatile suspended solids (VSS) provided by the municipal waste represented the 55% of the total ones. Under such condition, a methane yield corresponding to the biochemical methane potential (BMP) calculated through a 6-month experiment with non-packed microcosms (176 ml/gVS) was attained in about 1/4 of the time. Importantly, the BMP can significantly grow up as a consequence of the approach described in this study. IWA Publishing 2008.

  12. Prokaryotic diversity and dynamics in a full-scale municipal solid waste anaerobic reactor from start-up to steady-state conditions.

    PubMed

    Cardinali-Rezende, Juliana; Colturato, Luís F D B; Colturato, Thiago D B; Chartone-Souza, Edmar; Nascimento, Andréa M A; Sanz, José L

    2012-09-01

    The prokaryotic diversity of an anaerobic reactor for the treatment of municipal solid waste was investigated over the course of 2 years with the use of 16S rDNA-targeted molecular approaches. The fermentative Bacteroidetes and Firmicutes predominated, and Proteobacteria, Actinobacteria, Tenericutes and the candidate division WWE1 were also identified. Methane production was dominated by the hydrogenotrophic Methanomicrobiales (Methanoculleus sp.) and their syntrophic association with acetate-utilizing and propionate-oxidizing bacteria. qPCR demonstrated the predominance of the hydrogenotrophic over aceticlastic Methanosarcinaceae (Methanosarcina sp. and Methanimicrococcus sp.), and Methanosaetaceae (Methanosaeta sp.) were measured in low numbers in the reactor. According to the FISH and CARD-FISH analyses, Bacteria and Archaea accounted for 85% and 15% of the cells, respectively. Different cell counts for these domains were obtained by qPCR versus FISH analyses. The use of several molecular tools increases our knowledge of the prokaryotic community dynamics from start-up to steady-state conditions in a full-scale MSW reactor. Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. Optimization of wastewater feeding for single-cell protein production in an anaerobic wastewater treatment process utilizing purple non-sulfur bacteria in mixed culture condition.

    PubMed

    Honda, Ryo; Fukushi, Kensuke; Yamamoto, Kazuo

    2006-10-01

    Impacts of operation timing of feeding and withdrawal on anaerobic wastewater treatment utilizing purple non-sulfur bacteria have been investigated in mixed culture condition with acidogenic bacteria. Simulated wastewater containing glucose was treated in a laboratory-scale chemostat reactor, changing the timing of wastewater feeding and withdrawal. Rhodopseudomonas palustris, which does not utilize glucose as a substrate, was inoculated in the reactor. Rps. palustris was detected by a fluorescent in situ hybridization (FISH) technique using the specific Rpal686 probe. As a result, population ratios of Rps. palustris were over 20% through the operation. Rps. palustris could grow by utilizing metabolites of acidogenic bacteria that coexisted in the reactor. A morning feed was effective for a good growth of purple non-sulfur bacteria. A protein content of cultured bacteria was the highest when wastewater was fed in the morning. Dissolved organic carbon (DOC) removal was 94% independent of the timing control. Consequently, feeding in the morning is the optimum feed-timing control from the aspects of growth of purple non-sulfur bacteria and single-cell protein production.

  14. Growth condition and bacterial community for maximum hydrolysis of suspended organic materials in anaerobic digestion of food waste-recycling wastewater.

    PubMed

    Kim, Man Deok; Song, Minkyung; Jo, Minho; Shin, Seung Gu; Khim, Jee Hyeong; Hwang, Seokhwan

    2010-02-01

    This paper reports the effects of changing pH (5-7) and temperature (T, 40-60 degrees C) on the efficiencies of bacterial hydrolysis of suspended organic matter (SOM) in wastewater from food waste recycling (FWR) and the changes in the bacterial community responsible for this hydrolysis. Maximum hydrolysis efficiency (i.e., 50.5% reduction of volatile suspended solids) was predicted to occur at pH 5.7 and T = 44.5 degrees C. Changes in short-chain volatile organic acid profiles and in acidogenic bacterial communities were investigated under these conditions. Propionic and butyric acids concentrations increased rapidly during the first 2 days of incubation. Several band sequences consistent with Clostridium spp. were detected using denaturing gel gradient electrophoresis. Clostridium thermopalmarium and Clostridium novyi seemed to contribute to butyric acid production during the first 1.5 days of acidification of FWR wastewater, and C. thermopalmarium was a major butyric acid producer afterward. C. novyi was an important propionic acid producer. These two species appear to be important contributors to hydrolysis of SOM in the wastewater. Other acidogenic anaerobes, Aeromonas sharmana, Bacillus coagulans, and Pseudomonas plecoglossicida, were also indentified.

  15. Enhancement in hydrogen production by thermophilic anaerobic co-digestion of organic fraction of municipal solid waste and sewage sludge--optimization of treatment conditions.

    PubMed

    Tyagi, Vinay Kumar; Angériz Campoy, Rubén; Álvarez-Gallego, C J; Romero García, L I

    2014-07-01

    Batch dry-thermophilic anaerobic co-digestion (55°C) of organic fraction of municipal solid waste (OFMSW) and sewage sludge (SS) for hydrogen production was studied under several sludge combinations (primary sludge, PS; waste activated sludge, WAS; and mixed sludge, MS), TS concentrations (10-25%) and mixing ratios of OFMSW and SS (1:1, 2.5:1, 5:1, 10:1). The co-digestion of OFMSW and SS showed a 70% improvement in hydrogen production rate over the OFMSW fermentation only. The co-digestion of OFMSW with MS showed 47% and 115% higher hydrogen production potential as compared with OFMSW+PS and OFMSW+WAS, respectively. The maximum hydrogen yield of 51 mL H2/g VS consumed was observed at TS concentration of 20% and OFMSW to MS mixing ratio of 5:1, respectively. The acetic and butyric acids were the main acids in VFAs evolution; however, the higher butyric acid evolution indicated that the H2 fermentation was butyrate type fermentation.

  16. Examination of various cell culture techniques for co-incubation of virulent Treponema pallidum (Nichols I strain) under anaerobic conditions.

    PubMed Central

    Sandok, P L; Knight, S T; Jenkin, H M

    1976-01-01

    Treponema pallidum (Nichols virulent) was incubated with and without cells in cell culture medium reduced to -275 mV Ecal, pH 7.3, under deoxygenated conditions. Five to ten percent of the treponemes attached to cells and remained motile for at least 120 h in cell-treponeme systems of co-incubation. Virulent treponemes could be detected after 120 to 144 h in the supernatant fluids of cell-treponeme co-incubation cultures and in cell-free tubes containing medium harvested from aerobically cultivated mammalian cells. Medium supplemented with ox serum ultrafiltrate, pyruvate, and sodium thioglycolate and gas mixtures containing H2 and CO2 enhanced treponemal survival. Increases in treponemal numbers were observed using dark-field microscopy but were not substantiated using the rabbit lesion test. Continuous passage of the treponeme was not achieved in vitro. PMID:789395

  17. FeS-coated sand for removal of arsenic(III) under anaerobic conditions in permeable reactive barriers

    USGS Publications Warehouse

    Han, Y.-S.; Gallegos, T.J.; Demond, A.H.; Hayes, K.F.

    2011-01-01

    Iron sulfide (as mackinawite, FeS) has shown considerable promise as a material for the removal of As(III) under anoxic conditions. However, as a nanoparticulate material, synthetic FeS is not suitable for use in conventional permeable reactive barriers (PRBs). This study developed a methodology for coating a natural silica sand to produce a material of an appropriate diameter for a PRB. Aging time, pH, rinse time, and volume ratios were varied, with a maximum coating of 4.0 mg FeS/g sand achieved using a pH 5.5 solution at a 1:4 volume ratio (sand: 2 g/L FeS suspension), three days of aging and no rinsing. Comparing the mass deposited on the sand, which had a natural iron-oxide coating, with and without chemical washing showed that the iron-oxide coating was essential to the formation of a stable FeS coating. Scanning electron microscopy images of the FeS-coated sand showed a patchwise FeS surface coating. X-ray photoelectron spectroscopy showed a partial oxidation of the Fe(II) to Fe(III) during the coating process, and some oxidation of S to polysulfides. Removal of As(III) by FeS-coated sand was 30% of that by nanoparticulate FeS at pH 5 and 7. At pH 9, the relative removal was 400%, perhaps due to the natural oxide coating of the sand or a secondary mineral phase from mackinawite oxidation. Although many studies have investigated the coating of sands with iron oxides, little prior work reports coating with iron sulfides. The results suggest that a suitable PRB material for the removal of As(III) under anoxic conditions can be produced through the deposition of a coating of FeS onto natural silica sand with an iron-oxide coating. ?? 2010 Elsevier Ltd.

  18. Anaerobic growth of Corynebacterium glutamicum via mixed-acid fermentation.

    PubMed

    Michel, Andrea; Koch-Koerfges, Abigail; Krumbach, Karin; Brocker, Melanie; Bott, Michael

    2015-11-01

    Corynebacterium glutamicum, a model organism in microbial biotechnology, is known to metabolize glucose under oxygen-deprived conditions to l-lactate, succinate, and acetate without significant growth. This property is exploited for efficient production of lactate and succinate. Our detailed analysis revealed that marginal growth takes place under anaerobic conditions with glucose, fructose, sucrose, or ribose as a carbon and energy source but not with gluconate, pyruvate, lactate, propionate, or acetate. Supplementation of glucose minimal medium with tryptone strongly enhanced growth up to a final optical density at 600 nm (OD600) of 12, whereas tryptone alone did not allow growth. Amino acids with a high ATP demand for biosynthesis and amino acids of the glutamate family were particularly important for growth stimulation, indicating ATP limitation and a restricted carbon flux into the oxidative tricarboxylic acid cycle toward 2-oxoglutarate. Anaerobic cultivation in a bioreactor with constant nitrogen flushing disclosed that CO2 is required to achieve maximal growth and that the pH tolerance is reduced compared to that under aerobic conditions, reflecting a decreased capability for pH homeostasis. Continued growth under anaerobic conditions indicated the absence of an oxygen-requiring reaction that is essential for biomass formation. The results provide an improved understanding of the physiology of C. glutamicum under anaerobic conditions. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  19. Anaerobic Growth of Corynebacterium glutamicum via Mixed-Acid Fermentation

    PubMed Central

    Michel, Andrea; Koch-Koerfges, Abigail; Krumbach, Karin; Brocker, Melanie

    2015-01-01

    Corynebacterium glutamicum, a model organism in microbial biotechnology, is known to metabolize glucose under oxygen-deprived conditions to l-lactate, succinate, and acetate without significant growth. This property is exploited for efficient production of lactate and succinate. Our detailed analysis revealed that marginal growth takes place under anaerobic conditions with glucose, fructose, sucrose, or ribose as a carbon and energy source but not with gluconate, pyruvate, lactate, propionate, or acetate. Supplementation of glucose minimal medium with tryptone strongly enhanced growth up to a final optical density at 600 nm (OD600) of 12, whereas tryptone alone did not allow growth. Amino acids with a high ATP demand for biosynthesis and amino acids of the glutamate family were particularly important for growth stimulation, indicating ATP limitation and a restricted carbon flux into the oxidative tricarboxylic acid cycle toward 2-oxoglutarate. Anaerobic cultivation in a bioreactor with constant nitrogen flushing disclosed that CO2 is required to achieve maximal growth and that the pH tolerance is reduced compared to that under aerobic conditions, reflecting a decreased capability for pH homeostasis. Continued growth under anaerobic conditions indicated the absence of an oxygen-requiring reaction that is essential for biomass formation. The results provide an improved understanding of the physiology of C. glutamicum under anaerobic conditions. PMID:26276118

  20. The challenges of anaerobic digestion and the role of biochar in optimizing anaerobic digestion.

    PubMed

    Fagbohungbe, Michael O; Herbert, Ben M J; Hurst, Lois; Ibeto, Cynthia N; Li, Hong; Usmani, Shams Q; Semple, Kirk T

    2017-03-01

    Biochar, like most other adsorbents, is a carbonaceous material, which is formed from the combustion of plant materials, in low-zero oxygen conditions and results in a material, which has the capacity to sorb chemicals onto its surfaces. Currently, research is being carried out to investigate the relevance of biochar in improving the soil ecosystem, digestate quality and most recently the anaerobic digestion process. Anaerobic digestion (AD) of organic substrates provides both a sustainable source of energy and a digestate with the potential to enhance plant growth and soil health. In order to ensure that these benefits are realised, the anaerobic digestion system must be optimized for process stability and high nutrient retention capacity in the digestate produced. Substrate-induced inhibition is a major issue, which can disrupt the stable functioning of the AD system reducing microbial breakdown of the organic waste and formation of methane, which in turn reduces energy output. Likewise, the spreading of digestate on land can often result in nutrient loss, surface runoff and leaching. This review will examine substrate inhibition and their impact on anaerobic digestion, nutrient leaching and their environmental implications, the properties and functionality of biochar material in counteracting these challenges.

  1. Application of Anaerobic Digestion Model No. 1 for simulating anaerobic mesophilic sludge digestion

    SciTech Connect

    Mendes, Carlos Esquerre, Karla Matos Queiroz, Luciano

    2015-01-15

    Highlights: • The behavior of a anaerobic reactor was evaluated through modeling. • Parametric sensitivity analysis was used to select most sensitive of the ADM1. • The results indicate that the ADM1 was able to predict the experimental results. • Organic load rate above of 35 kg/m{sup 3} day affects the performance of the process. - Abstract: Improving anaerobic digestion of sewage sludge by monitoring common indicators such as volatile fatty acids (VFAs), gas composition and pH is a suitable solution for better sludge management. Modeling is an important tool to assess and to predict process performance. The present study focuses on the application of the Anaerobic Digestion Model No. 1 (ADM1) to simulate the dynamic behavior of a reactor fed with sewage sludge under mesophilic conditions. Parametric sensitivity analysis is used to select the most sensitive ADM1 parameters for estimation using a numerical procedure while other parameters are applied without any modification to the original values presented in the ADM1 report. The results indicate that the ADM1 model after parameter estimation was able to predict the experimental results of effluent acetate, propionate, composites and biogas flows and pH with reasonable accuracy. The simulation of the effect of organic shock loading clearly showed that an organic shock loading rate above of 35 kg/m{sup 3} day affects the performance of the reactor. The results demonstrate that simulations can be helpful to support decisions on predicting the anaerobic digestion process of sewage sludge.

  2. Anaerobic Digestion.

    PubMed

    Liebetrau, Jan; Sträuber, Heike; Kretzschmar, Jörg; Denysenko, Velina; Nelles, Michael

    2017-04-09

    The term anaerobic digestion usually refers to the microbial conversion of organic material to biogas, which mainly consists of methane and carbon dioxide. The technical application of the naturally-occurring process is used to provide a renewable energy carrier and - as the substrate is often waste material - to reduce the organic matter content of the substrate prior to disposal.Applications can be found in sewage sludge treatment, the treatment of industrial and municipal solid wastes and wastewaters (including landfill gas utilization), and the conversion of agricultural residues and energy crops.For biorefinery concepts, the anaerobic digestion (AD) process is, on the one hand, an option to treat organic residues from other production processes. Concomitant effects are the reduction of organic carbon within the treated substance, the conversion of nitrogen and sulfur components, and the production of an energy-rich gas - the biogas. On the other hand, the multistep conversion of complex organic material offers the possibility of interrupting the conversion chain and locking out intermediates for utilization as basic material within the chemical industry.

  3. Conditional BDNF release under pathological conditions improves Huntington's disease pathology by delaying neuronal dysfunction

    PubMed Central

    2011-01-01

    Background Brain-Derived Neurotrophic Factor (BDNF) is the main candidate for neuroprotective therapy for Huntington's disease (HD), but its conditional administration is one of its most challenging problems. Results Here we used transgenic mice that over-express BDNF under the control of the Glial Fibrillary Acidic Protein (GFAP) promoter (pGFAP-BDNF mice) to test whether up-regulation and release of BDNF, dependent on astrogliosis, could be protective in HD. Thus, we cross-mated pGFAP-BDNF mice with R6/2 mice to generate a double-mutant mouse with mutant huntingtin protein and with a conditional over-expression of BDNF, only under pathological conditions. In these R6/2:pGFAP-BDNF animals, the decrease in striatal BDNF levels induced by mutant huntingtin was prevented in comparison to R6/2 animals at 12 weeks of age. The recovery of the neurotrophin levels in R6/2:pGFAP-BDNF mice correlated with an improvement in several motor coordination tasks and with a significant delay in anxiety and clasping alterations. Therefore, we next examined a possible improvement in cortico-striatal connectivity in R62:pGFAP-BDNF mice. Interestingly, we found that the over-expression of BDNF prevented the decrease of cortico-striatal presynaptic (VGLUT1) and postsynaptic (PSD-95) markers in the R6/2:pGFAP-BDNF striatum. Electrophysiological studies also showed that basal synaptic transmission and synaptic fatigue both improved in R6/2:pGAP-BDNF mice. Conclusions These results indicate that the conditional administration of BDNF under the GFAP promoter could become a therapeutic strategy for HD due to its positive effects on synaptic plasticity. PMID:21985529

  4. Effect of caffeine on upper-body anaerobic performance in wrestlers in simulated competition-day conditions.

    PubMed

    Aedma, Martin; Timpmann, Saima; Ööpik, Vahur

    2013-12-01

    Peak power (PP) and mean power (MP) attained in upper body sprint performance test are considered important factors for competitive success in wrestling. This study aimed to determine whether acute caffeine ingestion would better maintain PP and MP across a simulated competition day in wrestling. In a double-blind, counterbalanced, crossover study, 14 trained wrestlers ingested either placebo or 5 mg/kg caffeine and completed four 6-min upper body intermittent sprint performance tests with 30-min recovery periods between consecutive tests. PP and MP were recorded during and blood lactate concentration was measured before and after each test. Ratings of perceived fatigue (RPF) and exertion (RPE) were recorded before and after each test, respectively. Heart rate (HR) was monitored across the whole testing period. Mean power decreased across four tests in both trials (p < .05), but the reduction in PP (from 277.2 ± 34.6 W to 257.3 ± 45.1 W; p < .05) only occurred in caffeine trial. Both pretest blood lactate concentration and HR were higher in caffeine than in placebo trial (p < .05) in the third and fourth tests. No between-trial differences occurred in RPF or RPE. Under simulated competition day conditions mimicking four consecutive wrestling matches, acute caffeine ingestion has a partially detrimental effect on upper body intermittent sprint performance in trained wrestlers. Elevated HR and blood lactate levels observed between tests after caffeine ingestion suggest that caffeine may impair recovery between consecutive maximal efforts.

  5. Model selection, identification and validation in anaerobic digestion: a review.

    PubMed

    Donoso-Bravo, Andres; Mailier, Johan; Martin, Cristina; Rodríguez, Jorge; Aceves-Lara, César Arturo; Vande Wouwer, Alain

    2011-11-01

    Anaerobic digestion enables waste (water) treatment and energy production in the form of biogas. The successful implementation of this process has lead to an increasing interest worldwide. However, anaerobic digestion is a complex biological process, where hundreds of microbial populations are involved, and whose start-up and operation are delicate issues. In order to better understand the process dynamics and to optimize the operating conditions, the availability of dynamic models is of paramount importance. Such models have to be inferred from prior knowledge and experimental data collected from real plants. Modeling and parameter identification are vast subjects, offering a realm of approaches and methods, which can be difficult to fully understand by scientists and engineers dedicated to the plant operation and improvements. This review article discusses existing modeling frameworks and methodologies for parameter estimation and model validation in the field of anaerobic digestion processes. The point of view is pragmatic, intentionally focusing on simple but efficient methods.

  6. Sonolysis and ozonation as pretreatment for anaerobic digestion of solid organic waste.

    PubMed

    Cesaro, Alessandra; Belgiorno, Vincenzo

    2013-05-01

    This study aims to compare the efficiency of sonolysis and ozonation in improving anaerobic biodegradability of source sorted organic fraction of municipal solid waste, for the enhancing of biogas production and energy recovery as well. The methane yield of solid organic material anaerobic digestion is significantly affected by substrate availability, which can be favoured by pretreatments. In this investigation, both sonolysis and ozonation effects on substrate solubilisation and anaerobic biodegradability were evaluated under different treatment conditions. Results show that both pretreatments can significantly improve the solubilisation of organic solid waste. However, during ozonation experiments, no correlation was observed between increased solubilisation and biogas production: the application of higher ozone doses led to the formation of by-products less biodegradable than untreated substrate. This evidence makes the ultrasound process more efficient than ozonation and addresses further studies for sonolysis optimisation as pretreatment for solid waste anaerobic digestion.

  7. Global warming potential of material fractions occurring in source-separated organic household waste treated by anaerobic digestion or incineration under different framework conditions.

    PubMed

    Naroznova, Irina; Møller, Jacob; Scheutz, Charlotte

    2016-12-01

    This study compared the environmental profiles of anaerobic digestion (AD) and incineration, in relation to global warming potential (GWP), for treating individual material fractions that may occur in source-separated organic household waste (SSOHW). Different framework conditions representative for the European Union member countries were considered. For AD, biogas utilisation with a biogas engine was considered and two potential situations investigated - biogas combustion with (1) combined heat and power production (CHP) and (2) electricity production only. For incineration, four technology options currently available in Europe were covered: (1) an average incinerator with CHP production, (2) an average incinerator with mainly electricity production, (3) an average incinerator with mainly heat production and (4) a state-of-the art incinerator with CHP working at high energy recovery efficiencies. The study was performed using a life cycle assessment in its consequential approach. Furthermore, the role of waste-sorting guidelines (defined by the material fractions allowed for SSOHW) in relation to GWP of treating overall SSOHW with AD was investigated. A case-study of treating 1tonne of SSOHW under framework conditions in Denmark was conducted. Under the given assumptions, vegetable food waste was the only material fraction which was always better for AD compared to incineration. For animal food waste, kitchen tissue, vegetation waste and dirty paper, AD utilisation was better unless it was compared to a highly efficient incinerator. Material fractions such as moulded fibres and dirty cardboard were attractive for AD, albeit only when AD with CHP and incineration with mainly heat production were compared. Animal straw, in contrast, was always better to incinerate. Considering the total amounts of individual material fractions in waste generated within households in Denmark, food waste (both animal and vegetable derived) and kitchen tissue are the main material

  8. Impacts of microalgae pre-treatments for improved anaerobic digestion: thermal treatment, thermal hydrolysis, ultrasound and enzymatic hydrolysis.

    PubMed

    Ometto, Francesco; Quiroga, Gerardo; Pšenička, Pavel; Whitton, Rachel; Jefferson, Bruce; Villa, Raffaella

    2014-11-15

    Anaerobic digestion (AD) of microalgae is primarily inhibited by the chemical composition of their cell walls containing biopolymers able to resist bacterial degradation. Adoption of pre-treatments such as thermal, thermal hydrolysis, ultrasound and enzymatic hydrolysis have the potential to remove these inhibitory compounds and enhance biogas yields by degrading the cell wall, and releasing the intracellular algogenic organic matter (AOM). This work investigated the effect of four pre-treatments on three microalgae species, and their impact on the quantity of soluble biomass released in the media and thus on the digestion process yields. The analysis of the composition of the soluble COD released and of the TEM images of the cells showed two main degradation actions associated with the processes: (1) cell wall damage with the release of intracellular AOM (thermal, thermal hydrolysis and ultrasound) and (2) degradation of the cell wall constituents with the release of intracellular AOM and the solubilisation of the cell wall biopolymers (enzymatic hydrolysis). As a result of this, enzymatic hydrolysis showed the greatest biogas yield increments (>270%) followed by thermal hydrolysis (60-100%) and ultrasounds (30-60%).

  9. Appropriate Fe (II) Addition Significantly Enhances Anaerobic Ammonium Oxidation (Anammox) Activity through Improving the Bacterial Growth Rate

    PubMed Central

    Liu, Yiwen; Ni, Bing-Jie

    2015-01-01

    The application of anaerobic ammonium oxidation (Anammox) process is often limited by the slow growth rate of Anammox bacteria. As the essential substrate element that required for culturing Anammox sludge, Fe (II) is expected to affect Anammox bacterial growth. This work systematically studied the effects of Fe (II) addition on Anammox activity based on the kinetic analysis of specific growth rate using data from batch tests with an enriched Anammox sludge at different dosing levels. Results clearly demonstrated that appropriate Fe (II) dosing (i.e., 0.09 mM) significantly enhanced the specific Anammox growth rate up to 0.172 d−1 compared to 0.118 d−1 at regular Fe (II) level (0.03 mM). The relationship between Fe (II) concentration and specific Anammox growth rate was found to be well described by typical substrate inhibition kinetics, which was integrated into currently well-established Anammox model to describe the enhanced Anammox growth with Fe (II) addition. The validity of the integrated Anammox model was verified using long-term experimental data from three independent Anammox reactors with different Fe (II) dosing levels. This Fe (II)-based approach could be potentially implemented to enhance the process rate for possible mainstream application of Anammox technology, in order for an energy autarchic wastewater treatment. PMID:25644239

  10. Appropriate Fe (II) addition significantly enhances anaerobic ammonium oxidation (Anammox) activity through improving the bacterial growth rate.

    PubMed

    Liu, Yiwen; Ni, Bing-Jie

    2015-02-03

    The application of anaerobic ammonium oxidation (Anammox) process is often limited by the slow growth rate of Anammox bacteria. As the essential substrate element that required for culturing Anammox sludge, Fe (II) is expected to affect Anammox bacterial growth. This work systematically studied the effects of Fe (II) addition on Anammox activity based on the kinetic analysis of specific growth rate using data from batch tests with an enriched Anammox sludge at different dosing levels. Results clearly demonstrated that appropriate Fe (II) dosing (i.e., 0.09 mM) significantly enhanced the specific Anammox growth rate up to 0.172 d(-1) compared to 0.118 d(-1) at regular Fe (II) level (0.03 mM). The relationship between Fe (II) concentration and specific Anammox growth rate was found to be well described by typical substrate inhibition kinetics, which was integrated into currently well-established Anammox model to describe the enhanced Anammox growth with Fe (II) addition. The validity of the integrated Anammox model was verified using long-term experimental data from three independent Anammox reactors with different Fe (II) dosing levels. This Fe (II)-based approach could be potentially implemented to enhance the process rate for possible mainstream application of Anammox technology, in order for an energy autarchic wastewater treatment.

  11. Improvement of operating conditions in waste incinerators using engineering tools.

    PubMed

    Yang, Won; Nam, Hyung-Sik; Choi, Sangmin

    2007-01-01

    Operation parameters such as waste feed rate, air supply, and temperature of the gas in incineration plants should be carefully determined for various situations, which include seasonal and annual changes in fuel characteristics, and performance change of the hardware. These changes may cause off-design point operation of the incinerators, which results in many problems in operation of the flue gas treatment system, low-oxygen in the combustion chamber, thermal damage of the incinerator wall, and so on. In this study, an engineering approach using computational tools along with field tests and observation is presented. For computational tools, a 0-dimensional model for heat and mass balance, computational fluid dynamics (CFD), and a global prediction model for dioxin are employed. They play a key role in diagnosing incineration systems and evaluating changes in operating conditions. The typical results of each tool are reported, and examples of improvement in operating performance are described.

  12. Breeding crops for improved mineral nutrition under climate change conditions.

    PubMed

    Pilbeam, David J

    2015-06-01

    Improvements in understanding how climate change may influence chemical and physical processes in soils, how this may affect nutrient availability, and how plants may respond to changed availability of nutrients will influence crop breeding programmes. The effects of increased atmospheric CO2 and warmer temperatures, both individually and combined, on soil microbial activity, including mycorrhizas and N-fixing organisms, are evaluated, together with their implications for nutrient availability. Potential changes to plant growth, and the combined effects of soil and plant changes on nutrient uptake, are discussed. The organization of research on the efficient use of macro- and micronutrients by crops under climate change conditions is outlined, including analysis of QTLs for nutrient efficiency. Suggestions for how the information gained can be used in plant breeding programmes are given.

  13. Effect of long term anaerobic and intermittent anaerobic/aerobic starvation on aerobic granules.

    PubMed

    Pijuan, Maite; Werner, Ursula; Yuan, Zhiguo

    2009-08-01

    The effect of long term anaerobic and intermittent anaerobic/aerobic starvation on the structure and activity of aerobic granules was studied. Aerobic granular sludge treating abattoir wastewater and achieving high levels of nutrient removal was subjected to 4-5 week starvation under anaerobic and intermittent anaerobic/aerobic conditions. Microscopic pictures of granules at the beginning of the starvation period presented a round and compact surface morphology with a much defined external perimeter. Under both starvation conditions, the morphology changed at the end of starvation with the external border of the granules surrounded by floppy materials. The loss of granular compactness was faster and more pronounced under anaerobic/aerobic starvation conditions. The release of Ca(2+) at the onset of anaerobic/aerobic starvation suggests a degradation of extracellular polymeric substances. The activity of ammonia oxidizing bacteria was reduced by 20 and 36% during anaerobic and intermittent anaerobic/aerobic starvation, respectively. When fresh wastewater was reintroduced, the granules recovered their initial morphology within 1 week of normal operation and the nutrient removal activity recovered fully in 3 weeks. The results show that both anaerobic and intermittent anaerobic/aerobic conditions are suitable for maintaining granule structure and activity during starvation.

  14. Improving flight condition situational awareness through Human Centered Design.

    PubMed

    Craig, Carol

    2012-01-01

    In aviation, there is currently a lack of accurate and timely situational information, specifically weather data, which is essential when dealing with the unpredictable complexities that can arise while flying. For example, weather conditions that require immediate evasive action by the flight crew, such as isolated heavy rain, micro bursts, and atmospheric turbulence, require that the flight crew receive near real-time and precise information about the type, position, and intensity of those conditions. Human factors issues arise in considering how to display the various sources of weather information to the users of that information and how to integrate this display into the existing environment. In designing weather information display systems, it is necessary to meet the demands of different users, which requires an examination of the way in which the users process and use weather information. Using Human Centered Design methodologies and concepts will result in a safer, more efficient and more intuitive solution. Specific goals of this approach include 1) Enabling better fuel planning; 2) Allowing better divert strategies; 3) Ensuring pilots, navigators, dispatchers and mission planners are referencing weather from the same sources; 4) Improving aircrew awareness of aviation hazards such as turbulence, icing, hail and convective activity; 5) Addressing inconsistent availability of hazard forecasts outside the United States Air Defense Identification Zone (ADIZ); and 6) Promoting goal driven approaches versus event driven (prediction).

  15. [Participation to improve working conditions: evidence and experience].

    PubMed

    García, Ana M; Boix, Pere; G Benavides, Fernando; Gadea, Rafael; Rodrigo, Fernando; Serra, Consol

    2016-11-01

    Participation of stakeholders is a key requirement for the success of public health programmes. Working and employment conditions are major determinants for people's health and wellbeing, and workplaces are ideal environments to implement programmes with a very direct level of participation. In Spain, the main regulatory framework for occupational health and safety, Law 31/1995, establishes the principles of "efficiency, coordination and participation" as a necessary basis for workers' health protection. This same Law establishes the role of the health and safety workers' representative, responsible for occupational risk prevention, and the occupational health and safety committee, a body with equal representation and the same objectives at the heart of the company. Among recent experiences of participation in occupational health, participatory ergonomics programmes have stood out. The aim of these programmes is to improve working conditions with a view to reducing musculoskeletal disorders, which is a very common and highly prevalent work-related injury in Spain. This study describes the characteristics and results of some experiences of participatory ergonomics carried out recently in Spain, from which relevant learning can be extrapolated about processes, facilitators and barriers in order to extend such programmes to other areas of occupational and public health.

  16. An urgent need to improve life conditions of seniors.

    PubMed

    Hebert, R

    2010-10-01

    In the fall of 2007, the Government of Quebec set up a Public Consultation on Living Conditions of Seniors. Fifty sessions were held in 26 cities across all 17 regions of the province. More than 4000 seniors attended the sessions and 275 briefs were received from scientists and associations. Three themes were identified in the report published in 2008: supporting seniors and their caregivers, reinforcing the place of seniors in society, and preventing problems associated with aging (suicide, abuse, addictions). The main actions that I recommended included: Increasing the Guaranteed Income Supplement to prevent poverty; Modifying pension plans and working conditions to allow for progressive retirement; Making a major investment in home care to provide access to services regardless of place of residence; Introducing an Autonomy Support Benefit and autonomy insurance program for financing services to support people with disabilities; Generalizing an Integrated Service Delivery Network providing services to frail older people; Better training for professionals in gerontology. I also recommended setting up a National Policy on Seniors to align all government departments and agencies, municipalities and the private sector around a vision, objectives and a set of actions for improving the integration of seniors in an aging society. This would contribute to a more equitable, interdependent and wiser society. Unfortunately, the Government did not support these recommendations. It is now time for scientists to get involved in leading policy on seniors and in the political arena.

  17. Flue gas conditioning for improved particle collection in electrostatic precipitators

    SciTech Connect

    Durham, M.D.

    1993-01-15

    It is concluded that the laboratory tests should be conducted at high levels of SO[sub 3] such that the resulting resistivity is in the range of 10[sup 7]--10[sup 8] ohm-cm. There are several reasons leading to this conclusion. At SO[sub 3] concentrations of 30 ppM and greater, the curves for both dew point and resistivity are relatively flat so that changes in gas phase SO[sub 3] will have minimal impact on particle characteristics. In addition, the electrostatic forces are relatively flat in this range so that changes in flue gas conditions will that result in a change in resistivity by up to two orders of magnitude will have little effect on the magnitude of reentrainment. Finally, at the very low resistivity conditions, reentrainment will be the highest. Since the purpose of the laboratory resistivity tests is to determine the relative ability of the various additives to reduce resistivity, the greater the reentrainment, the easier it will be to measure an improvement. Tests were conducted by first operating at baseline conditions with no additives and then repeating the test with additives. The data collected during each test includes the resistivity of the material, thickness of the collected dust layer, and subjective indications of the dust characteristics. The candidate additives were from the polymer group, cellulose derivatives, starches and gums, and oils. No waxes or synthetic compounds have been tested to date in the laboratory apparatus. Of the seventeen additives tested, eight appeared to have a positive impact on either the ash layer thickness or the physical appearance of the dust layer. Excessive deposits on the discharge electrode resulted during injection of some of the additives. Three of the additives resulted in significant deposits in the injection chamber. The build up on the electrode was interpreted as a positive indicator of increase particle adhesion. The initial observations and comments for the eight additives are listed in Table 1.

  18. Azospirillum improves lettuce growth and transplant under saline conditions.

    PubMed

    Fasciglione, Gabriela; Casanovas, Elda M; Yommi, Alejandra; Sueldo, Rolando J; Barassi, Carlos A

    2012-09-01

    Recent studies have shown that as a plant-growth-promoting rhizobacteria (PGPR), Azospirillum inoculation could contribute to the mitigation of the negative effects caused by salt on lettuce growth. Moreover, the use of PGPR to alleviate the effects of transplant in vegetables has also been recognized. However, the scarce data available on the use of Azospirillum to improve lettuce growth before and after transplant under saline conditions prompted us to focus our research on this topic. Early germination and seedling settlement of seeds exposed to 0 and 40 mol m(-3) NaCl were clearly improved by Azospirillum inoculation. At 0 mol m(-3) NaCl, plant establishment, leaf mass and root mass parameters before transplant were significantly higher in inoculated plants than in non-inoculated controls. At harvest, leaf fresh weight, ascorbic acid content and plant survival to transplant were also significantly higher in Azospirillum-inoculated plants grown at 0 mol m(-3) NaCl. In addition to these effects, leaf dry weight, area and chlorophyll content were also increased by Azospirillum inoculation when plants were grown at 40 mol m(-3) NaCl. Azospirillum-inoculated lettuce seeds yield a higher number of transplanted plants with superior quality than non-inoculated controls grown at 0 or at 40 mol m(-3) NaCl. Copyright © 2012 Society of Chemical Industry.

  19. Cosubstrate independent mineralization of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by a Desulfovibrio species under anaerobic conditions.

    PubMed

    Arnett, Clint M; Adrian, Neal R

    2009-02-01

    Past handling practices associated with the manufacturing and processing of the high explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has resulted in extensive environmental contamination. In-situ biodegradation is a promising technology for remediating RDX contaminated sites but often relies on the addition of a cosubstrate. A sulfate-reducing bacterium isolated from an RDX-degrading enrichment culture was studied for its ability to grow on RDX as a sole source of carbon and nitrogen and for its ability to mineralize RDX in the absence of a cosubstrate. The results showed the isolate degraded 140 muM RDX in 63 days when grown on RDX as a carbon source. Biomass within the carbon limited culture increased 9-fold compared to the RDX unamended controls. When the isolate was incubated with RDX as sole source of nitrogen it degraded 160 muM RDX in 41 days and exhibited a 4-fold increase in biomass compared to RDX unamended controls. Radiolabeled studies under carbon limiting conditions with (14)C-hexahydro-1,3,5-trinitro-1,3,5-triazine confirmed mineralization of the cyclic nitramine. After 60 days incubation 26% of the radiolabel was recovered as (14)CO(2), while in the control bottles less than 1% of the radiolabel was recovered as (14)CO(2). Additionally, approximately 2% of the radiolabeled carbon was found to be associated with the biomass. The 16S rDNA gene was sequenced and identified the isolate as a novel species of Desulfovibrio, having a 95.1% sequence similarity to Desulfovibrio desulfuricans. This is the first known anaerobic bacterium capable of mineralizing RDX when using it as a carbon and energy source for growth.

  20. Supplementation of Acqua Lete® (Bicarbonate Calcic Mineral Water) improves hydration status in athletes after short term anaerobic exercise

    PubMed Central

    2012-01-01

    Background Experimental studies suggest that mineral waters with high concentrations of calcium and bicarbonate can impact acid–base balance. The purpose of this study was to test the effect on acid–base balance and specific urine gravity, of a bicarbonate calcic mineral water (Acqua Lete®) compared to a minimally mineralized water. Methods 88 amateur male athletes underwent two experimental trials with a modified Wingate test: the first was carried out without hydration (Control Test, Test C, n = 88); the second was carried out after one week of controlled hydration (Test with hydration, Test H, n = 88), with 1.5 L/day of a very low mineral content water (Group A, n = 44) or 1.5 L/day of Acqua Lete® (Group B, n = 44). Measure of body temperature, bioimpedance analysis, muscular ultrasound, and urinalysis were taken before (t0), immediately after (t1), 5’ (t2), and 30’ (t3) after exercise. Results Hydration results in a decreased core temperature; muscular ultrasound showed increased muscle thickness after exercise related to content of body water. Regarding urinalysis, in test H, we found in both groups after exercise a significant decrease of specific urine gravity with significantly lower levels in Group B. We also found a significant increase of pH in the same Group B. Conclusions In conclusion all the athletes hydrated with Acqua Lete® showed a positive impact on hydration status after anaerobic exercise with significant decrease of specific urine gravity and a positive effect on pH. PMID:22835267

  1. Quantification of the inert chemical oxygen demand of raw wastewater and evaluation of soluble microbial product production in demo-scale upflow anaerobic sludge blanket reactors under different operational conditions.

    PubMed

    Aquino, Sergio F; Gloria, Roberto M; Silva, Silvana Q; Chernicharo, Carlos A L

    2009-06-01

    This paper investigates the production of soluble microbial products (SMPs) in demonstration-scale upflow anaerobic sludge blanket reactors operated under different conditions and fed with raw wastewater. The results showed that 9.2 +/- 1.3% of the influent soluble chemical oxygen demand (COD) could be considered inert to anaerobic treatment and that the amount of COD produced by biomass varied from 30 to 70 mg x L(-1), accounting for 45 to 63% of the soluble effluent COD. The accumulation of SMP appeared to be dependent on the hydraulic retention time (HRT) applied to the reactors, with a larger accumulation of SMP observed at the lowest HRT (5 hours); this may have been due to stress conditions caused by high upflow velocity (1.1 m x h(-1)). In terms of residual COD characterization, ultrafiltration results showed that higher amounts of high molecular weight compounds were found when HRT was the lowest (5 hours), and that the molecular weight distribution depended on the operational condition of the reactors. Biodegradability tests showed that the low and high molecular weight SMPs were only partially degraded anaerobically (10 to 60%) and that the high molecular weight SMPs were difficult to degrade aerobically.

  2. Anaerobic benzene degradation by bacteria

    PubMed Central

    Vogt, Carsten; Kleinsteuber, Sabine; Richnow, Hans‐Hermann

    2011-01-01

    Summary Benzene is a widespread and toxic contaminant. The fate of benzene in contaminated aquifers seems to be primarily controlled by the abundance of oxygen: benzene is aerobically degraded at high rates by ubiquitous microorganisms, and the oxygen‐dependent pathways for its breakdown were elucidated more than 50 years ago. In contrast, benzene was thought to be persistent under anoxic conditions until 25 years ago. Nevertheless, within the last 15 years, several benzene‐degrading cultures have been enriched under varying electron acceptor conditions in laboratories around the world, and organisms involved in anaerobic benzene degradation have been identified, indicating that anaerobic benzene degradation is a relevant environmental process. However, only a few benzene degraders have been isolated in pure culture so far, and they all use nitrate as an electron acceptor. In some highly enriched strictly anaerobic cultures, benzene has been described to be mineralized cooperatively by two or more different organisms. Despite great efforts, the biochemical mechanism by which the aromatic ring of benzene is activated in the absence of oxygen is still not fully elucidated; methylation, hydroxylation and carboxylation are discussed as likely reactions. This review summarizes the current knowledge about the ‘key players’ of anaerobic benzene degradation under different electron acceptor conditions and the possible pathway(s) of anaerobic benzene degradation. PMID:21450012

  3. Anaerobic lactic acid degradation during ensilage of whole crop maize inoculated with lactobacillus buchneri inhibits yeast growth and improves aerobic stability

    PubMed

    Driehuis; Elferink; Spoelstra

    1999-10-01

    Aerobic deterioration of silages is initiated by (facultative) aerobic micro-organisms, usually yeasts, that oxidize the preserving organic acids. In this study, a Lactobacillus buchneri strain isolated from maize silage was evaluated for its potential as a bacterial inoculant that enhances aerobic stability of silages. In four experiments, chopped whole crop maize (30-43% dry matter (DM)) was inoculated with Lact. buchneri and ensiled in laboratory silos. Uninoculated silages served as controls. Analysis of silages treated with Lact. buchneri at levels of 103-106 cfu g-1 after about 3 months of anaerobic storage showedthat acetic acid and 1-propanol contents increased with inoculum levels above 104 cfu g-1,whereas lactic acid decreased. Propionic acid, silage pH and DM loss increased withinoculum levels above 105 cfu g-1. Time course experiments with maize inoculated with Lact. buchneri at 4 x 104-2 x 105 cfu g-1 showed that up to 7-14 d after ensiling, Lact. buchneri had no effect on silage characteristics. Thereafter, the lactic acid content of the inoculated silages declined and, simultaneously, acetic acid and, to a lesser extent, propionic acid and 1-propanol, accumulated. Inoculation reduced survival of yeasts during the anaerobic storage phase and inhibited yeast growth when the silage was exposed to O2, resulting in a substantial improvement in aerobic stability. The results indicate that the use of Lact. buchneri as a silage inoculant can enhance aerobic stability by inhibition of yeasts. The ability of the organism to ferment lactic acid to acetic acid appears to be an important underlying principle of this effect.

  4. Physiologically anaerobic microorganisms of the deep subsurface

    SciTech Connect

    Stevens, S.E. Jr.; Chung, K.T.

    1991-06-01

    This study seeks to determine numbers, diversity, and morphology of anaerobic microorganisms in 15 samples of subsurface material from the Idaho National Engineering Laboratory, in 18 samples from the Hanford Reservation and in 1 rock sample from the Nevada Test Site; set up long term experiments on the chemical activities of anaerobic microorganisms based on these same samples; work to improve methods for the micro-scale determination of in situ anaerobic microbial activity;and to begin to isolate anaerobes from these samples into axenic culture with identification of the axenic isolates.

  5. Biodegradation of the nitramine explosives hexahydro-1,3,5-trinitro-1,3,5-triazine and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine in cold marine sediment under anaerobic and oligotrophic conditions.

    PubMed

    Zhao, Jian-Shen; Greer, Charles W; Thiboutot, Sonia; Ampleman, Guy; Hawari, Jalal

    2004-02-01

    The in situ degradation of the two nitramine explosives, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), was evaluated using a mixture of RDX and HMX, incubated anaerobically at 10 degrees C with marine sediment from a previous military dumping site of unexploded ordnance (UXO) in Halifax Harbor, Nova Scotia, Canada. The RDX concentration (14.7 mg.L-1) in the aqueous phase was reduced by half in 4 days, while reduction of HMX concentration (1.2 mg.L-1) by half required 50 days. Supplementation with the carbon sources glucose, acetate, or citrate did not affect the removal rate of RDX but improved removal of HMX. Optimal mineralization of RDX and HMX was obtained in the presence of glucose. Using universally labeled (UL)-[14C]RDX, we obtained a carbon mass balance distributed as follows: CO2, 48%-58%; water soluble products, 27%-31%; acetonitrile extractable products, 2.0%-3.4%; and products covalently bound to the sediments and biomass, 8.9% (in the presence of glucose). The disappearance of RDX was accompanied by the formation of the mononitroso derivative hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) and formaldehyde (HCHO) that subsequently disappeared. In the case of HMX, mineralization reached only 13%-27% after 115 days of incubation in the presence or absence of the carbon sources. The disappearance of HMX was also accompanied by the formation of the mononitroso derivative. The total population of psychrotrophic anaerobes that grew at 10 degrees C was 2.6 x 10(3) colony-forming units.(g sediment dry mass)-1, and some psychrotrophic sediment isolates were capable of degrading RDX under conditions similar to those used for sediments. Based on the distribution of products, we suggest that the sediment microorganisms degrade RDX and HMX via an initial reduction to the corresponding mononitroso derivative, followed by denitration and ring cleavage.

  6. Cofactor engineering of ketol-acid reductoisomerase (IlvC) and alcohol dehydrogenase (YqhD) improves the fusel alcohol yield in algal protein anaerobic fermentation

    SciTech Connect

    Wu, Weihua; Tran-Gyamfi, Mary Bao; Jaryenneh, James Dekontee; Davis, Ryan W.

    2016-08-24

    Recently the feasibility of conversion of algal protein to mixed alcohols has been demonstrated with an engineered E.coli strain, enabling comprehensive utilization of the biomass for biofuel applications. However, the yield and titers of mixed alcohol production must be improved for market adoption. A major limiting factor for achieving the necessary yield and titer improvements is cofactor imbalance during the fermentation of algal protein. To resolve this problem, a directed evolution approach was applied to modify the cofactor specificity of two key enzymes (IlvC and YqhD) from NADPH to NADH in the mixed alcohol metabolic pathway. Using high throughput screening, more than 20 YqhD mutants were identified to show activity on NADH as a cofactor. Of these 20 mutants, the top five of YqhD mutants were selected for combination with two IlvC mutants with NADH as a cofactor for the modification of the protein conversion strain. The combination of the IlvC and YqhD mutants yielded a refined E.coli strain, subtype AY3, with increased fusel alcohol yield of ~60% compared to wild type under anaerobic fermentation on amino acid mixtures. When applied to real algal protein hydrolysates, the strain AY3 produced 100% and 38% more total mixed alcohols than the wild type strain on two different algal hydrolysates, respectively. The results indicate that cofactor engineering is a promising approach to improve the feasibility of bioconversion of algal protein into mixed alcohols as advanced biofuels.

  7. An improved titration model reducing over estimation of total volatile fatty acids in anaerobic digestion of energy crop, animal slurry and food waste.

    PubMed

    Purser, B J Jobling; Thai, S-M; Fritz, T; Esteves, S R; Dinsdale, R M; Guwy, A J

    2014-09-15

    Titration methodologies have been used for the many years for low cost routine monitoring of full scale anaerobic digestion plants. These methodologies have been correlated to indicate the carbonate alkalinity and the volatile fatty acids (VFA) content within digesters. Two commonly used two end-point titration methods were compared using a dataset of 154 samples from energy crop and animal slurry digestates and were shown to be inaccurate in the estimation of tVFA. Using this dataset correlated with HPLC VFA analysis, two empirical bivariate linear regression equations were derived, where the validation dataset showed an absolute tVFA mean error improvement from ±3386 and ±3324 mg kg(-1) tVFA to ±410 and ±286 mg kg(-1) tVFA, respectively. The same equation was then applied to a food waste dataset where an absolute tVFA mean error was improved from ±3828 to ±576 mg kg(-1) tVFA. The newly derived titration equations can provide greater confidence in digester performance monitoring and are tools that can improve digester management. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Improved biogas production and biodegradation of oilseed rape straw by using kitchen waste and duck droppings as co-substrates in two-phase anaerobic digestion.

    PubMed

    Wang, Chuqiao; Hong, Feng; Lu, Yong; Li, Xianning; Liu, Hengming

    2017-01-01

    Oilseed rape straw (ORS) is a kind of biorefractory waste widely existing in the rural area of China, which is highly suitable to mix with kitchen waste (KW) and duck droppings (DD) in two-phase anaerobic digestion (AD). This research introduced the importance of KW and DD addition to improve the biogas production and biodegradation of ORS. A set of comparative experiments were conducted on two-phase mono- and co-digestion with organic load of 60 g VS/L. The total methane yield (TMY) and the biodegradation of ORS of co-digestions were obviously improving, and the synergistic effect found in the two-phase co-digestions. The optimum mixing ratio of ORS, KW and DD was 50:40:10, and the corresponding TMY and VS degradation rate of ORS were 374.5 mL/g VS and 49.7%, respectively. Addition of KW and DD maintained the pH within the optimal range for the hydrolyzing-acidification, improved the phase separation and buffering capacity of AD system.

  9. Improved biogas production and biodegradation of oilseed rape straw by using kitchen waste and duck droppings as co-substrates in two-phase anaerobic digestion

    PubMed Central

    Wang, Chuqiao; Hong, Feng; Lu, Yong; Liu, Hengming

    2017-01-01

    Oilseed rape straw (ORS) is a kind of biorefractory waste widely existing in the rural area of China, which is highly suitable to mix with kitchen waste (KW) and duck droppings (DD) in two-phase anaerobic digestion (AD). This research introduced the importance of KW and DD addition to improve the biogas production and biodegradation of ORS. A set of comparative experiments were conducted on two-phase mono- and co-digestion with organic load of 60 g VS/L. The total methane yield (TMY) and the biodegradation of ORS of co-digestions were obviously improving, and the synergistic effect found in the two-phase co-digestions. The optimum mixing ratio of ORS, KW and DD was 50:40:10, and the corresponding TMY and VS degradation rate of ORS were 374.5 mL/g VS and 49.7%, respectively. Addition of KW and DD maintained the pH within the optimal range for the hydrolyzing-acidification, improved the phase separation and buffering capacity of AD system. PMID:28767709

  10. Cofactor engineering of ketol-acid reductoisomerase (IlvC) and alcohol dehydrogenase (YqhD) improves the fusel alcohol yield in algal protein anaerobic fermentation

    SciTech Connect

    Wu, Weihua; Tran-Gyamfi, Mary Bao; Jaryenneh, James Dekontee; Davis, Ryan W.

    2016-08-24

    Recently the feasibility of conversion of algal protein to mixed alcohols has been demonstrated with an engineered E.coli strain, enabling comprehensive utilization of the biomass for biofuel applications. However, the yield and titers of mixed alcohol production must be improved for market adoption. A major limiting factor for achieving the necessary yield and titer improvements is cofactor imbalance during the fermentation of algal protein. To resolve this problem, a directed evolution approach was applied to modify the cofactor specificity of two key enzymes (IlvC and YqhD) from NADPH to NADH in the mixed alcohol metabolic pathway. Using high throughput screening, more than 20 YqhD mutants were identified to show activity on NADH as a cofactor. Of these 20 mutants, the top five of YqhD mutants were selected for combination with two IlvC mutants with NADH as a cofactor for the modification of the protein conversion strain. The combination of the IlvC and YqhD mutants yielded a refined E.coli strain, subtype AY3, with increased fusel alcohol yield of ~60% compared to wild type under anaerobic fermentation on amino acid mixtures. When applied to real algal protein hydrolysates, the strain AY3 produced 100% and 38% more total mixed alcohols than the wild type strain on two different algal hydrolysates, respectively. The results indicate that cofactor engineering is a promising approach to improve the feasibility of bioconversion of algal protein into mixed alcohols as advanced biofuels.

  11. A novel fast mass transfer anaerobic inner loop fluidized bed biofilm reactor for PTA wastewater treatment.

    PubMed

    Chen, Yingwen; Zhao, Jinlong; Li, Kai; Xie, Shitao

    In this paper, a fast mass transfer anaerobic inner loop fluidized bed biofilm reactor (ILFBBR) was developed to improve purified terephthalic acid (PTA) wastewater treatment. The emphasis of this study was on the start-up mode of the anaerobic ILFBBR, the hydraulic loadings and the operation stability. The biological morphology of the anaerobic biofilm in the reactors was also analyzed. The anaerobic column could operate successfully for 46 days due to the pre-aerating process. The anaerobic column had the capacity to resist shock loadings and maintained a high stable chemical oxygen demand (COD) and terephthalic acid removal rates at a hydraulic retention time of 5-10 h, even under conditions of organic volumetric loadings as high as 28.8 kg COD·m(-3).d(-1). The scanning electron microscope analysis of the anaerobic carrier demonstrated that clusters of prokaryotes grew inside of pores and that the filaments generated by pre-aeration contributed to the anaerobic biofilm formation and stability.

  12. Improving initial conditions for cosmological N-body simulations

    NASA Astrophysics Data System (ADS)

    Garrison, Lehman H.; Eisenstein, Daniel J.; Ferrer, Douglas; Metchnik, Marc V.; Pinto, Philip A.

    2016-10-01

    In cosmological N-body simulations, the representation of dark matter as discrete `macroparticles' suppresses the growth of structure, such that simulations no longer reproduce linear theory on small scales near kNyquist. Marcos et al. demonstrate that this is due to sparse sampling of modes near kNyquist and that the often-assumed continuum growing modes are not proper growing modes of the particle system. We develop initial conditions (ICs) that respect the particle linear theory growing modes and then rescale the mode amplitudes to account for growth suppression. These ICs also allow us to take advantage of our very accurate N-body code ABACUS to implement second-order Lagrangian perturbation theory (2LPT) in configuration space. The combination of 2LPT and rescaling improves the accuracy of the late-time power spectra, halo mass functions, and halo clustering. In particular, we achieve 1 per cent accuracy in the power spectrum down to kNyquist, versus kNyquist/4 without rescaling or kNyquist/13 without 2LPT, relative to an oversampled reference simulation. We anticipate that our 2LPT will be useful for large simulations where fast Fourier transforms are expensive and that rescaling will be useful for suites of medium-resolution simulations used in cosmic emulators and galaxy survey mock catalogues. Code to generate ICs is available at https://github.com/lgarrison/zeldovich-PLT.

  13. New housing conditions: improving the welfare of experimental animals.

    PubMed

    Ottesen, Jan L; Weber, Anett; Gürtler, Hanne; Mikkelsen, Lars Friis

    2004-06-01

    As animal experiments and testing are still a necessary part of the discovery and development of new drugs and do not seem likely to be totally replaced in the foreseeable future, it is important that the care and use of these animals are continuously refined. Since the housing facilities are where most experimental animals spend the major part of their lives, this area should be given special attention to ensure optimal welfare for the animals. In a unique collaboration between a pharmaceutical company and an animal welfare organisation, the housing conditions of mice, rats, guinea-pigs, rabbits and dogs, respectively, were reviewed with focus on the basic needs of the animals. Prototypes for new housing systems satisfying the most important of these basic needs of the animals were developed, with valuable input from international experts with special knowledge of the behaviour of experimental animals. These new housing systems and species-specific, newly introduced socialisation programmes contribute to improved animal welfare and a better occupational health of the animal caretakers. Since these new housing systems are more pleasant and appealing, they may also have the added benefit that they contribute to a broader public acceptance of the use of experimental animals.

  14. An integrated microbial electrolysis-anaerobic digestion process combined with pretreatment of wastewater solids to improve hydrogen production

    DOE PAGES

    Beegle, Jeff R.; Borole, Abhijeet P.

    2017-08-17

    A combined anaerobic digestion (AD) and microbial electrolysis cell (MEC) system, named here as ADMEC, was investigated in this paper to evaluate the energy recovery from pretreated wastewater solids. Alkaline and thermal hydrolysis pretreatment methods increased the solubility of organic compounds present in the raw solids by 25% and 20%, respectively. The soluble phase from pretreatment was separated and used for microbial electrolysis, whereas the insoluble fraction was fed into semi-continuous digesters. The digester effluent was later utilized as a second MEC substrate. The pretreatment had variable effects on AD and MEC performance. The methane content in AD biogas wasmore » higher in pretreated groups, 78.29 ± 2.89% and 73.2 ± 1.79%, for alkaline and thermal, than the control, 50.26 ± 0.53%, but the overall biogas production rates were lower than the control, 20 and 30 mL CH4 gCOD-1 d-1 for alkaline and thermal compared to 80 mL CH4 gCOD-1 d-1. The effluent streams from thermally pretreated digesters were the best substrate for microbial electrolysis, in terms of hydrogen production and efficiency. The MECs produced 1.7 ± 0.2 L-H2 per L per day, 0.3 ± 0.1 L-H2 per L per day, and 0.29 ± 0.1 L-H2 per L per day, for thermal, alkaline, and control reactors. The productivity was lower compared to acetate and propionate controls, which yielded 5.79 ± 0.03 L-H2 per L per day and 3.49 ± 0.10 L-H2 per L per day, respectively. The pretreatment solubilized fractions were not ideal substrates for microbial electrolysis. Finally, a chemical oxygen demand (COD) mass balance showed that pretreatment shifts the electron flux away from methane and biomass sinks towards hydrogen production.« less

  15. Anaerobic Mycobacterium tuberculosis cell death stems from intracellular acidification mitigated by the DosR regulon.

    PubMed

    Reichlen, Matthew J; Leistikow, Rachel L; Scobey, Micah S; Born, Sarah E M; Voskuil, Martin I

    2017-09-05

    Mycobacterium tuberculosis (Mtb) is a strict aerobe capable of prolonged survival in the absence of oxygen. We investigated the ability of anaerobic Mtb to counter challenges to internal pH homeostasis in the absence of aerobic respiration, the primary mechanism of proton efflux for aerobic bacilli. Anaerobic Mtb populations were markedly impaired for survival under a mildly acidic pH relative to standard culture conditions. Acidic environmental pH greatly increased the susceptibility of anaerobic bacilli to collapse of proton motive force by protonophores, to antimicrobial compounds that target entry into the electron transport system, and to small organic acids with uncoupling activity. However, anaerobic bacilli exhibited high tolerance to these challenges at near neutral pH. At a slightly alkaline pH which was near the optimum intracellular pH, protonophore addition even improved long-term bacilli survival. Although anaerobic Mtb in acidic conditions maintained 40% lower ATP levels than bacilli at standard culture conditions, ATP loss alone could not explain the viability drop. Protonophores decreased ATP levels by more than 90% regardless of extracellular pH but were bactericidal only under acidic conditions, indicating anaerobic bacilli could survive extreme ATP loss provided the external pH was within viable intracellular parameters. Acidic conditions drastically decreased anaerobic survival of a DosR mutant while an alkaline environment improved survival of the DosR mutant. Together these findings indicate intracellular acidification is a primary challenge for anaerobic Mtb survival and that the DosR regulon plays a critical role in sustaining internal pH homeostasis.Importance: During infection, Mtb bacilli are prevalent in environments largely devoid of oxygen. Yet the factors that influence survival of these severely growth- and metabolically-limited bacilli remain poorly understood. We determined how anaerobic bacilli respond to fluctuations in

  16. Influence of pretreatment techniques on anaerobic digestion of pulp and paper mill sludge: A review.

    PubMed

    Veluchamy, C; Kalamdhad, Ajay S

    2017-09-01

    Pulp and paper industry is one of the most polluting, energy and water intensive industries in the world. Produced pulp and paper mill sludge (PPMS) faces a major problem for handling and its management. An anaerobic digestion has become an alternative source. This review provides a detailed summary of anaerobic digestion of PPMS - An overview of the developments and improvement opportunities. This paper explores the different pretreatment methods to enhance biogas production from the PPMS. First, the paper gives an overview of PPMS production, and then it reviews PPMS as a substrate for anaerobic digestion with or without pretreatment. Finally, it discuss the optimal condition and concentration of organic and inorganic compounds required for the anaerobic metabolic activity. Future research should focus on the combination of different pretreatment technologies, relationship between sludge composition, reactor design and its operation, and microbial community dynamics. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. [Characteristics of N2, N2O, NO, CO2 and CH4 Emissions in Anaerobic Condition from Sandy Loam Paddy Soil].

    PubMed

    Cao, Na; Wang, Rui; Liao, Ting-ting; Chen, Nuo; Zheng, Xun-hua; Yao, Zhi-sheng; Zhang, Hai; Butterbach-Bahl, Klaus

    2015-09-01

    Understanding the characteristics of the production of nitrogen gases (N2, N2O and NO), CO2 and CH4 in anaerobic paddy soils is not only a prerequisite for an improved mechanistic understanding of key microbial processes involved in the production of atmospheric greenhouse gases (GHG), but might also provide the basis for designing greenhouse gas mitigation strategies. Moreover, quantifying the composition fractions of denitrification gaseous products is of key importance for improving parameterization schemes of microbial processes in process-oriented models which are increasingly used for assessing soil GHG emissions at site and national scales. In our experiments we investigated two sandy loam soils from two paddy fields. The initial concentrations of soil nitrate and dissolved organic carbon (DOC) were set at approximately 50 mg.kg-1 and mg.kg-1, respectively, by adding a mixture solution of KNO3 and glucose. The emissions of N2, N2O NO, CO2 and CH4, as well as concentrations of carbon and nitrogen substrates for each soil sample were measured simultaneously, using a gas-flow-soil-core technique and a paralleling substrate monitoring system. The results showed that the accumulative emissions of N2, N2O and NO of the two soil samples for the entire incubation period were 6 - 8, 20, and 15 - 18 mg.kg-1, respectively. By measuring the cumulative emissions of denitrification gases (N, = N2 + N2O + NO) we were able to explain 95% to 98% of observed changes in s1ifr nilrate concentrations. The mass fractions of N2, N2O and NO emissions to Nt were approximately 15% -19%, 47% -49%, and 34% -36%, respectively. Thus, in our experiments N2O and NO were the main products of denitrification for the entire incubation period. However, as the temporal courses of hourly or daily production of the denitrification gases showed, NO production dominated and peaked firstly, and then N2O, before finally N2 became the dominant product. Our results show the high temporal dynamic of

  18. Effect of anaerobic soil disinfestation on the bacterial community and key soilborne phytopathogenic agents under walnut tree-crop nursery conditions

    USDA-ARS?s Scientific Manuscript database

    Background and Aims: Anaerobic Soil Disinfestation (ASD) is a chemical-independent approach to manage soilborne phytopathogens. While it has been demonstrated that ASD can suppress phytopathogens in vegetable cropping systems, it has not been examined for control of tree-crop diseases. We examined t...

  19. Model-based design of an agricultural biogas plant: application of anaerobic digestion model no.1 for an improved four chamber scheme.

    PubMed

    Wett, B; Schoen, M; Phothilangka, P; Wackerle, F; Insam, H

    2007-01-01

    Different digestion technologies for various substrates are addressed by the generic process description of Anaerobic Digestion Model No. 1. In the case of manure or agricultural wastes a priori knowledge about the substrate in terms of ADM1 compounds is lacking and influent characterisation becomes a major issue. The actual project has been initiated for promotion of biogas technology in agriculture and for expansion of profitability also to rather small capacity systems. In order to avoid costly individual planning and installation of each facility a standardised design approach needs to be elaborated. This intention pleads for bio kinetic modelling as a systematic tool for process design and optimisation. Cofermentation under field conditions was observed, quality data and flow data were recorded and mass flow balances were calculated. In the laboratory different substrates have been digested separately in parallel under specified conditions. A configuration of four ADM1 model reactors was set up. Model calibration identified disintegration rate, decay rates for sugar degraders and half saturation constant for sugar as the three most sensitive parameters showing values (except the latter) about one order of magnitude higher than default parameters. Finally, the model is applied to the comparison of different reactor configurations and volume partitions. Another optimisation objective is robustness and load flexibility, i.e. the same configuration should be adaptive to different load situations only by a simple recycle control in order to establish a standardised design.

  20. Biogas production improvement and C/N control by natural clinoptilolite addition into anaerobic co-digestion of Phragmites australis, feces and kitchen waste.

    PubMed

    Wang, Xiaowei; Zhang, Lieyu; Xi, Beidou; Sun, Wenjun; Xia, Xunfeng; Zhu, Chaowei; He, Xiaosong; Li, Mingxiao; Yang, Tianxue; Wang, Pengfei; Zhang, Zhonglei

    2015-03-01

    Anaerobic co-digestion (A co-D) performance of Phragmites australis, feces and kitchen waste with addition of clinoptilolite (one main kind of zeolite) was investigated to evaluate the improvement of biogas/methane production and internal mechanism of nitrogen and organics control. A better biogas/methane production was observed by 10% clinoptilolite (v/v) than bentonite and diatomite, with the shortest lag phase of 0.070d(-1), the max rate of 15.89L/(kgVSday) and ultimate biogas production of 308.2L/kgVS as the modified Gompertz equation predicted. Accordingly, the content of methane in the biogas was increased from 44.10% to 65.30%. Furthermore, the clinoptilolite inhibited the acidification of digestion liquid (optimum pH 7.0-7.5) and enhanced the VFAs (acetic acid, propionic acid and butyric acid) destruction. Moreover, 10% of clinoptilolite optimally enhanced the microbial utilization of Ca(2+)/Mg(2+), controlled the C/N ratio, and improved the biogas production as well as NH3-N/NO3-N inhibition efficiency.

  1. Improved Monitoring of Semi-Continuous Anaerobic Digestion of Sugarcane Waste: Effects of Increasing Organic Loading Rate on Methanogenic Community Dynamics.

    PubMed

    Leite, Athaydes Francisco; Janke, Leandro; Lv, Zuopeng; Harms, Hauke; Richnow, Hans-Hermann; Nikolausz, Marcell

    2015-09-25

    The anaerobic digestion of filter cake and its co-digestion with bagasse, and the effect of gradual increase of the organic loading rate (OLR) from start-up to overload were investigated. Understanding the influence of environmental and technical parameters on the development of particular methanogenic pathway in the biogas process was an important aim for the prediction and prevention of process failure. The rapid accumulation of volatile organic acids at high OLR of 3.0 to 4.0 gvs·L⁻¹·day⁻¹ indicated strong process inhibition. Methanogenic community dynamics of the reactors was monitored by stable isotope composition of biogas and molecular biological analysis. A potential shift toward the aceticlastic methanogenesis was observed along with the OLR increase under stable reactor operating conditions. Reactor overloading and process failure were indicated by the tendency to return to a predominance of hydrogenotrophic methanogenesis with rising abundances of the orders Methanobacteriales and Methanomicrobiales and drop of the genus Methanosarcina abundance.

  2. Improved Monitoring of Semi-Continuous Anaerobic Digestion of Sugarcane Waste: Effects of Increasing Organic Loading Rate on Methanogenic Community Dynamics

    PubMed Central

    Leite, Athaydes Francisco; Janke, Leandro; Lv, Zuopeng; Harms, Hauke; Richnow, Hans-Hermann; Nikolausz, Marcell

    2015-01-01

    The anaerobic digestion of filter cake and its co-digestion with bagasse, and the effect of gradual increase of the organic loading rate (OLR) from start-up to overload were investigated. Understanding the influence of environmental and technical parameters on the development of particular methanogenic pathway in the biogas process was an important aim for the prediction and prevention of process failure. The rapid accumulation of volatile organic acids at high OLR of 3.0 to 4.0 gvs·L−1·day−1 indicated strong process inhibition. Methanogenic community dynamics of the reactors was monitored by stable isotope composition of biogas and molecular biological analysis. A potential shift toward the aceticlastic methanogenesis was observed along with the OLR increase under stable reactor operating conditions. Reactor overloading and process failure were indicated by the tendency to return to a predominance of hydrogenotrophic methanogenesis with rising abundances of the orders Methanobacteriales and Methanomicrobiales and drop of the genus Methanosarcina abundance. PMID:26404240

  3. Livestock Anaerobic Digester Database

    EPA Pesticide Factsheets

    The Anaerobic Digester Database provides basic information about anaerobic digesters on livestock farms in the United States, organized in Excel spreadsheets. It includes projects that are under construction, operating, or shut down.

  4. Improved Design of Anaerobic Digesters for Household Biogas Production in Indonesia: One Cow, One Digester, and One Hour of Cooking per Day

    PubMed Central

    Usack, Joseph G.; Wiratni, Wiratni; Angenent, Largus T.

    2014-01-01

    A government-sponsored initiative in Indonesia to design and implement low-cost anaerobic digestion systems resulted in 21 full-scale systems with the aim to satisfy the cooking fuel demands of rural households owning at least one cow. The full-scale design consisted of a 0.3 m diameter PVC pipe, which was operated as a conventional plug-flow system. The system generated enough methane to power a cooking stove for ∼1 h. However, eventual clogging from solids accumulation inside the bioreactor proved to be a major drawback. Here, we improved the digester configuration to remedy clogging while maintaining system performance. Controlled experiments were performed using four 9-L laboratory-scale digesters operated at a temperature of 27 ± 1°C, a volatile solids loading rate of 2.0 g VS·L−1·day−1, and a 21-day hydraulic retention time. Two of the digesters were replicates of the original design (control digesters), while the other two digesters included internal mixing or effluent recycle (experimental digesters). The performance of each digester was compared based on methane yields, VS removal efficiencies, and steady-state solids concentrations during an operating period of 311 days. Statistical analyses revealed that internal mixing and effluent recycling resulted in reduced solids accumulation compared to the controls without diminishing methane yields or solids removal efficiencies. PMID:24715809

  5. Eliminating methanogenic activity in hydrogen reactor to improve biogas production in a two-stage anaerobic digestion process co-digesting municipal food waste and sewage sludge.

    PubMed

    Zhu, Heguang; Parker, Wayne; Conidi, Daniela; Basnar, Robert; Seto, Peter

    2011-07-01

    Laboratory scale two-stage anaerobic digestion process model was operated for 280 days to investigate the feasibility to produce both hydrogen and methane from a mixture feedstock (1:1 (v/v)) of municipal food waste and sewage sludge. The maximum hydrogen and methane yields obtained in the two stages were 0.93 and 9.5 mL/mL feedstock. To eliminate methanogenic activity and obtain substantial hydrogen production in the hydrogen reactor, both feedstock and mixed liquor required treatment. The heat treatment (100°C, 10 min) for feedstock and a periodical treatment (every 2-5 weeks, either heating, removal of biomass particles or flushing with air) for mixed liquor were effective in different extent. The methane production in the second stage was significantly improved by the hydrogen production in the first stage. The maximum methane production obtained in the period of high hydrogen production was more than 2-fold of that observed in the low hydrogen production period.

  6. Improved design of anaerobic digesters for household biogas production in indonesia: one cow, one digester, and one hour of cooking per day.

    PubMed

    Usack, Joseph G; Wiratni, Wiratni; Angenent, Largus T

    2014-01-01

    A government-sponsored initiative in Indonesia to design and implement low-cost anaerobic digestion systems resulted in 21 full-scale systems with the aim to satisfy the cooking fuel demands of rural households owning at least one cow. The full-scale design consisted of a 0.3 m diameter PVC pipe, which was operated as a conventional plug-flow system. The system generated enough methane to power a cooking stove for ∼ 1 h. However, eventual clogging from solids accumulation inside the bioreactor proved to be a major drawback. Here, we improved the digester configuration to remedy clogging while maintaining system performance. Controlled experiments were performed using four 9-L laboratory-scale digesters operated at a temperature of 27 ± 1 °C, a volatile solids loading rate of 2.0 g VS · L(-1) · day(-1), and a 21-day hydraulic retention time. Two of the digesters were replicates of the original design (control digesters), while the other two digesters included internal mixing or effluent recycle (experimental digesters). The performance of each digester was compared based on methane yields, VS removal efficiencies, and steady-state solids concentrations during an operating period of 311 days. Statistical analyses revealed that internal mixing and effluent recycling resulted in reduced solids accumulation compared to the controls without diminishing methane yields or solids removal efficiencies.

  7. Start-up performance and granular sludge features of an improved external circulating anaerobic reactor for algae-laden water treatment.

    PubMed

    Yu, Yaqin; Lu, Xiwu

    2017-09-01

    The microbial characteristics of granular sludge during the rapid start of an enhanced external circulating anaerobic reactor were studied to improve algae-laden water treatment efficiency. Results showed that algae laden water was effectively removed after about 35 d, and the removal rates of chemical oxygen demand (COD) and algal toxin were around 85% and 92%, respectively. Simultaneously, the gas generation rate was around 380 mL/gCOD. The microbial community structure in the granular sludge of the reactor was complicated, and dominated by coccus and filamentous bacteria. Methanosphaera, Methanolinea, Thermogymnomonas, Methanoregula, Methanomethylovorans, and Methanosaeta were the major microorganisms in the granular sludge. The activities of protease and coenzyme F420 were high in the granular sludge. The intermittent stirring device and the reverse-flow system were further found to overcome the disadvantage of the floating and crusting of cyanobacteria inside the reactor. Meanwhile, the effect of mass transfer inside the reactor can be accelerated to help give the reactor a rapid start.

  8. Cofactor engineering of ketol-acid reductoisomerase (IlvC) and alcohol dehydrogenase (YqhD) improves the fusel alcohol yield in algal protein anaerobic fermentation

    DOE PAGES

    Wu, Weihua; Tran-Gyamfi, Mary Bao; Jaryenneh, James Dekontee; ...

    2016-08-24

    Recently the feasibility of conversion of algal protein to mixed alcohols has been demonstrated with an engineered E.coli strain, enabling comprehensive utilization of the biomass for biofuel applications. However, the yield and titers of mixed alcohol production must be improved for market adoption. A major limiting factor for achieving the necessary yield and titer improvements is cofactor imbalance during the fermentation of algal protein. To resolve this problem, a directed evolution approach was applied to modify the cofactor specificity of two key enzymes (IlvC and YqhD) from NADPH to NADH in the mixed alcohol metabolic pathway. Using high throughput screening,more » more than 20 YqhD mutants were identified to show activity on NADH as a cofactor. Of these 20 mutants, the top five of YqhD mutants were selected for combination with two IlvC mutants with NADH as a cofactor for the modification of the protein conversion strain. The combination of the IlvC and YqhD mutants yielded a refined E.coli strain, subtype AY3, with increased fusel alcohol yield of ~60% compared to wild type under anaerobic fermentation on amino acid mixtures. When applied to real algal protein hydrolysates, the strain AY3 produced 100% and 38% more total mixed alcohols than the wild type strain on two different algal hydrolysates, respectively. The results indicate that cofactor engineering is a promising approach to improve the feasibility of bioconversion of algal protein into mixed alcohols as advanced biofuels.« less

  9. [Anaerobic bacteria 150 years after their discovery by Pasteur].

    PubMed

    García-Sánchez, José Elías; García-Sánchez, Enrique; Martín-Del-Rey, Ángel; García-Merino, Enrique

    2015-02-01

    In 2011 we celebrated the 150th anniversary of the discovery of anaerobic bacteria by Louis Pasteur. The interest of the biomedical community on such bacteria is still maintained, and is particularly focused on Clostridium difficile. In the past few years important advances in taxonomy have been made due to the genetic, technological and computing developments. Thus, a significant number of new species related to human infections have been characterised, and some already known have been reclassified. At pathogenic level some specimens of anaerobic microflora, that had not been isolated from human infections, have been now isolated in some clinical conditions. There was emergence (or re-emergence) of some species and clinical conditions. Certain anaerobic bacteria have been associated with established infectious syndromes. The virulence of certain strains has increased, and some hypotheses on their participation in certain diseases have been given. In terms of diagnosis, the routine use of MALDI-TOF has led to a shortening of time and a cost reduction in the identification, with an improvement directly related to the improvement of data bases. The application of real-time PCR has been another major progress, and the sequencing of 16srRNA gene and others is currently a reality for several laboratories. Anaerobes have increased their resistance to antimicrobial agents, and the emergence of resistance to carbapenems and metronidazole, and multi-resistance is a current reality. In this situation, linezolid could be an effective alternative for Bacteroides. Fidaxomicin is the only anti-anaerobic agent introduced in the recent years, specifically for the diarrhoea caused by C.difficile. Moreover, some mathematical models have also been proposed in relation with this species. Copyright © 2013 Elsevier España, S.L.U. y Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.

  10. A residency clinic chronic condition management quality improvement project.

    PubMed

    Halverson, Larry W; Sontheimer, Dan; Duvall, Sharon

    2007-02-01

    Quality improvement in chronic disease management is a major agenda for improving health and reducing health care costs. A six-component chronic disease management model can help guide this effort. Several characteristics of the "new model" of family medicine described by the Future of Family Medicine (FFM) Project Leadership Committee are promulgated to foster practice changes that improve quality. Our objective was to implement and assess a quality improvement project guided by the components of a chronic disease management model and FFM new model characteristics. Diabetes was selected as a model chronic disease focus. Multiple practice changes were implemented. A mature electronic medical record facilitated data collection and measurement of quality improvement progress. Data from the diabetes registry demonstrates that our efforts have been effective. Significant improvement occurred in five out of six quality indicators. Multidisciplinary teamwork in a model residency practice guided by chronic disease management principles and the FFM new model characteristics can produce significant management improvements in one important chronic disease.

  11. The curing agent sodium nitrite, used in the production of fermented sausages, is less inhibiting to the bacteriocin-producing meat starter culture Lactobacillus curvatus LTH 1174 under anaerobic conditions.

    PubMed

    Verluyten, Jurgen; Messens, Winy; De Vuyst, Luc

    2003-07-01

    Curvacin A is a listericidal bacteriocin produced by Lactobacillus curvatus LTH 1174, a strain isolated from fermented sausage. The response of this strain to an added curing agent (sodium nitrite) in terms of cell growth and bacteriocin production was