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Derek R Lovley - One of the best experts on this subject based on the ideXlab platform.
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Metabolic response of Geobacter sulfurreducens towards Electron Donor/acceptor variation
Microbial Cell Factories, 2010Co-Authors: Tae Hoon Yang, Derek R Lovley, Maddalena V Coppi, Jun SunAbstract:Background Geobacter sulfurreducens is capable of coupling the complete oxidation of organic compounds to iron reduction. The metabolic response of G. sulfurreducens towards variations in Electron Donors (acetate, hydrogen) and acceptors (Fe(III), fumarate) was investigated via ^13C-based metabolic flux analysis. We examined the ^13C-labeling patterns of proteinogenic amino acids obtained from G. sulfurreducens cultured with ^13C-acetate. Results Using ^13C-based metabolic flux analysis, we observed that Donor and acceptor variations gave rise to differences in gluconeogenetic initiation, tricarboxylic acid cycle activity, and amino acid biosynthesis pathways. Culturing G. sulfurreducens cells with Fe(III) as the Electron acceptor and acetate as the Electron Donor resulted in pyruvate as the primary carbon source for gluconeogenesis. When fumarate was provided as the Electron acceptor and acetate as the Electron Donor, the flux analysis suggested that fumarate served as both an Electron acceptor and, in conjunction with acetate, a carbon source. Growth on fumarate and acetate resulted in the initiation of gluconeogenesis by phosphoenolpyruvate carboxykinase and a slightly elevated flux through the oxidative tricarboxylic acid cycle as compared to growth with Fe(III) as the Electron acceptor. In addition, the direction of net flux between acetyl-CoA and pyruvate was reversed during growth on fumarate relative to Fe(III), while growth in the presence of Fe(III) and acetate which provided hydrogen as an Electron Donor, resulted in decreased flux through the tricarboxylic acid cycle. Conclusions We gained detailed insight into the metabolism of G. sulfurreducens cells under various Electron Donor/acceptor conditions using ^13C-based metabolic flux analysis. Our results can be used for the development of G. sulfurreducens as a chassis for a variety of applications including bioremediation and renewable biofuel production.
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reductive dechlorination of 2 chlorophenol by anaeromyxobacter dehalogenans with an electrode serving as the Electron Donor
Environmental Microbiology Reports, 2010Co-Authors: Sarah Strycharz, Kelly P Nevin, Ashley E. Franks, Sarah M Gannon, Amber R Boles, Derek R LovleyAbstract:Summary Electrodespoisedatpotentialslowenoughtoserveas an Electron Donor for microbial respiration, but high enough to avoid the production of hydrogen, have been proposed as an alternative to the use of soluble Electron Donors for stimulating the bioremediation of chlorinated contaminants and/or metals. However, this form of respiration using pure cultures of microorganisms has only been reported in Geobacter species. To further evaluate this bioremediation strategy studies were conducted with Anaeromyxobacter dehalogenans, which has previously been reported to reductively dechlorinate 2-chlorophenol to phenol with acetate as the Electron Donor. Anaeromyxobacter dehalogenans could oxidize acetate with Electron transfer to a graphite electrode poised at a positive potential, demonstrating its ability to directly exchange Electrons with electrodes. Anaeromyxobacter dehalogenans attached to electrodes poised at -300 mV versus standard hydrogen electrode reductively dechlorinated 2-chlorophenol to phenol. There was no dechlorination in the absence of A. dehalogenans and electrode-driven dechlorination stopped when the supply of Electrons to the electrode was disrupted. The findings that microorganisms other than Geobacter species can accept Electrons from electrodes for anaerobic respiration and that chlorinated aromatic compounds can be dechlorinated in this manner suggest that there may be substantial potential for treating a diversity of contaminants with microbe‐electrode interactions.
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graphite electrode as a sole Electron Donor for reductive dechlorination of tetrachlorethene by geobacter lovleyi
Applied and Environmental Microbiology, 2008Co-Authors: Sarah Strycharz, Trevor L Woodard, Jessica P Johnson, Kelly P Nevin, Robert A Sanford, Frank E Loffler, Derek R LovleyAbstract:The possibility that graphite electrodes can serve as the direct Electron Donor for microbially catalyzed reductive dechlorination was investigated with Geobacter lovleyi. In an initial evaluation of whether G. lovleyi could interact Electronically with graphite electrodes, cells were provided with acetate as the Electron Donor and an electrode as the sole Electron acceptor. Current was produced at levels that were ca. 10-fold lower than those previously reported for Geobacter sulfurreducens under similar conditions, and G. lovleyi anode biofilms were correspondingly thinner. When an electrode poised at −300 mV (versus a standard hydrogen electrode) was provided as the Electron Donor, G. lovleyi effectively reduced fumarate to succinate. The stoichiometry of Electrons consumed to succinate produced was 2:1, the ratio expected if the electrode served as the sole Electron Donor for fumarate reduction. G. lovleyi effectively reduced tetrachloroethene (PCE) to cis-dichloroethene with a poised electrode as the sole Electron Donor at rates comparable to those obtained when acetate serves as the Electron Donor. Cells were less abundant on the electrodes when the electrodes served as an Electron Donor than when they served as an Electron acceptor. PCE was not reduced in controls without cells or when the current supply to cells was interrupted. These results demonstrate that G. lovleyi can use a poised electrode as a direct Electron Donor for reductive dechlorination of PCE. The ability to colocalize dechlorinating microorganisms with electrodes has several potential advantages for bioremediation of subsurface chlorinated contaminants, especially in source zones where Electron Donor delivery is challenging and often limits dechlorination.
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Humics as an Electron Donor for anaerobic respiration.
Environmental microbiology, 1999Co-Authors: Derek R Lovley, Jocelyn L. Fraga, John D. Coates, Elizabeth L. Blunt-harrisAbstract:The possibility that microorganisms might use reduced humic substances (humics) as an Electron Donor for the reduction of Electron acceptors with a more positive redox potential was investigated. All of the Fe(III)- and humics-reducing microorganisms evaluated were capable of oxidizing reduced humics and/or the reduced humics analogue anthrahydroquinone-2,6,-disulphonate (AHODS), with nitrate and/or fumarate as the Electron acceptor. These included Geobacter metallireducens, Geobacter sulphurreducens, Geothrix fermentans, Shewanella alga, Wolinella succinogenes and 'S. barnesii'. Several of the humics-oxidizing microorganisms grew in medium with AHQDS as the sole Electron Donor and fumarate as the Electron acceptor. Even though it does not reduce Fe(III) or humics, Paracoccus denitrificans could use AHQDS and reduced humics as Electron Donors for denitrification. However, another denitrifier, Pseudomonas denitrificans, could not. AHODS could also serve as an Electron Donor for selenate and arsenate reduction by W. succinogenes. Electron spin resonance studies demonstrated that humics oxidation was associated with the oxidation of hydroquinone moieties in the humics. Studies with G. metallireducens and W. succinogenes demonstrated that the anthraquinone-2,6-disulphonate (AQDS)/AHQDS redox couple mediated an interspecies Electron transfer between the two organisms. These results suggest that, as microbially reduced humics enter less reduced zones of soils and sediments, the reduced humics may serve as Electron Donors for microbial reduction of several environmentally significant Electron acceptors.
Piet N L Lens - One of the best experts on this subject based on the ideXlab platform.
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Lignocellulosic biowastes as carrier material and slow release Electron Donor for sulphidogenesis of wastewater in an inverse fluidized bed bioreactor
Environmental Science and Pollution Research, 2018Co-Authors: Luis C. Reyes-alvarado, Álvaro Camarillo-gamboa, Elena Rustrian, Piet N L Lens, Eldon R. Rene, Giovanni Esposito, Eric HoubronAbstract:Industrial wastewaters containing high concentrations of sulphate, such as those generated by mining, metallurgical and mineral processing industries, require Electron Donor for biological sulfidogenesis. In this study, five types of lignocellulosic biowastes were characterized as potential low-cost slow release Electron Donors for application in a continuously operated sulphidogenic inverse fluidized bed bioreactor (IFBB). Among them, natural scourer and cork were selected due to their high composition of volatile solids (VS), viz. 89.1 and 96.3%, respectively. Experiments were performed in batch (47 days) and in an IFBB (49 days) using synthetic sulphate-rich wastewater. In batch, the scourer gave higher sulphate reduction rates (67.7 mg SO_4 ^2− L^−1 day^−1) in comparison to cork (12.1 mg SO_4 ^2− L^−1 day^−1), achieving >82% sulphate reduction efficiencies. In the IFBB packed with the natural scourer, the average sulphate reduction efficiency was 24 (±17)%, while the volumetric sulphate reduction rate was 167 (±117) mg SO_4 ^2− L^−1 day^−1. The long incubation time in the batch experiments (47 days) allowed higher sulphate reduction efficiencies in comparison to the short hydraulic retention time (24 h) in the IFBB. This suggests the hydrolysis-fermentation was the rate-limiting step and the Electron Donor supply (through hydrolysis of the lignocellulosic biowaste) was limiting the sulphate reduction. Lignocellulose as carrier material and slow release Electron Donor for sulphidogenesis
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Biotechnological Aspects of the Use of Methane as Electron Donor for Sulfate Reduction
Comprehensive Biotechnology, 2011Co-Authors: G. Gonzalez-gil, Roel J. W. Meulepas, Piet N L LensAbstract:Biotechnological sulfate reduction is a core process in the desulfurization of sulfate-rich waste streams. Sulfate-rich wastewaters from coal-burning power plants, mining, and metallurgical activities represent a special case because these wastewaters do not contain Electron Donors for sulfate reduction. To circumvent this problem, ethanol or hydrogen is added. Implementation of biological sulfate reduction to treat such industrial effluents depends largely on the economic feasibility of the process and most of the cost is associated to the supply of Electron Donor. The direct use of methane as Electron Donor is economically more advantageous. Currently, the main challenge is the development of a sludge or biofilm system that is capable of catalyzing the anaerobic oxidation of methane coupled to sulfate reduction at important rates. This microbial process has been observed in marine ecosystems. The article provides an overview of what is known about the process followed by an analysis of laboratory experiments for its application to treat sulfate-rich streams lacking Electron Donors. Encouraging results have been obtained using membrane-based bioreactors and bottlenecks have been identified.
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Biotechnological aspects of sulfate reduction with methane as Electron Donor
Reviews in Environmental Science and Bio Technology, 2010Co-Authors: Roel J. W. Meulepas, Alfons J. M. Stams, Piet N L LensAbstract:Biological sulfate reduction can be used for the removal and recovery of oxidized sulfur compounds and metals from waste streams. However, the costs of conventional Electron Donors, like hydrogen and ethanol, limit the application possibilities. Methane from natural gas or biogas would be a more attractive Electron Donor. Sulfate reduction with methane as Electron Donor prevails in marine sediments. Recently, several authors succeeded in cultivating the responsible microorganisms in vitro. In addition, the process has been studied in bioreactors. These studies have opened up the possibility to use methane as Electron Donor for sulfate reduction in wastewater and gas treatment. However, the obtained growth rates of the responsible microorganisms are extremely low, which would be a major limitation for applications. Therefore, further research should focus on novel cultivation techniques.
Alfons J. M. Stams - One of the best experts on this subject based on the ideXlab platform.
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Carbon Monoxide as an Electron Donor for the Biological Reduction of Sulphate
International journal of microbiology, 2010Co-Authors: Sofiya N. Parshina, Jan Sipma, Anne M. Henstra, Alfons J. M. StamsAbstract:Several strains of Gram-negative and Gram-positive sulphate-reducing bacteria (SRB) are able to use carbon monoxide (CO) as a carbon source and Electron Donor for biological sulphate reduction. These strains exhibit variable resistance to CO toxicity. The most resistant SRB can grow and use CO as an Electron Donor at concentrations up to 100%, whereas others are already severely inhibited at CO concentrations as low as 1-2%. Here, the utilization, inhibition characteristics, and enzymology of CO metabolism as well as the current state of genomics of CO-oxidizing SRB are reviewed. Carboxydotrophic sulphate-reducing bacteria can be applied for biological sulphate reduction with synthesis gas (a mixture of hydrogen and carbon monoxide) as an Electron Donor.
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Biotechnological aspects of sulfate reduction with methane as Electron Donor
Reviews in Environmental Science and Bio Technology, 2010Co-Authors: Roel J. W. Meulepas, Alfons J. M. Stams, Piet N L LensAbstract:Biological sulfate reduction can be used for the removal and recovery of oxidized sulfur compounds and metals from waste streams. However, the costs of conventional Electron Donors, like hydrogen and ethanol, limit the application possibilities. Methane from natural gas or biogas would be a more attractive Electron Donor. Sulfate reduction with methane as Electron Donor prevails in marine sediments. Recently, several authors succeeded in cultivating the responsible microorganisms in vitro. In addition, the process has been studied in bioreactors. These studies have opened up the possibility to use methane as Electron Donor for sulfate reduction in wastewater and gas treatment. However, the obtained growth rates of the responsible microorganisms are extremely low, which would be a major limitation for applications. Therefore, further research should focus on novel cultivation techniques.
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Citric acid wastewater as Electron Donor for biological sulfate reduction
Applied Microbiology and Biotechnology, 2009Co-Authors: Alfons J. M. Stams, Jacco Huisman, Pedro A. Garcia Encina, Gerard MuyzerAbstract:Citrate-containing wastewater is used as Electron Donor for sulfate reduction in a biological treatment plant for the removal of sulfate. The pathway of citrate conversion coupled to sulfate reduction and the microorganisms involved were investigated. Citrate was not a direct Electron Donor for the sulfate-reducing bacteria. Instead, citrate was fermented to mainly acetate and formate. These fermentation products served as Electron Donors for the sulfate-reducing bacteria. Sulfate reduction activities of the reactor biomass with acetate and formate were sufficiently high to explain the sulfate reduction rates that are required for the process. Two citrate-fermenting bacteria were isolated. Strain R210 was closest related to Trichococcus pasteurii (99.5% ribosomal RNA (rRNA) gene sequence similarity). The closest relative of strain S101 was Veillonella montepellierensis with an rRNA gene sequence similarity of 96.7%. Both strains had a complementary substrate range.
Sarah Strycharz - One of the best experts on this subject based on the ideXlab platform.
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reductive dechlorination of 2 chlorophenol by anaeromyxobacter dehalogenans with an electrode serving as the Electron Donor
Environmental Microbiology Reports, 2010Co-Authors: Sarah Strycharz, Kelly P Nevin, Ashley E. Franks, Sarah M Gannon, Amber R Boles, Derek R LovleyAbstract:Summary Electrodespoisedatpotentialslowenoughtoserveas an Electron Donor for microbial respiration, but high enough to avoid the production of hydrogen, have been proposed as an alternative to the use of soluble Electron Donors for stimulating the bioremediation of chlorinated contaminants and/or metals. However, this form of respiration using pure cultures of microorganisms has only been reported in Geobacter species. To further evaluate this bioremediation strategy studies were conducted with Anaeromyxobacter dehalogenans, which has previously been reported to reductively dechlorinate 2-chlorophenol to phenol with acetate as the Electron Donor. Anaeromyxobacter dehalogenans could oxidize acetate with Electron transfer to a graphite electrode poised at a positive potential, demonstrating its ability to directly exchange Electrons with electrodes. Anaeromyxobacter dehalogenans attached to electrodes poised at -300 mV versus standard hydrogen electrode reductively dechlorinated 2-chlorophenol to phenol. There was no dechlorination in the absence of A. dehalogenans and electrode-driven dechlorination stopped when the supply of Electrons to the electrode was disrupted. The findings that microorganisms other than Geobacter species can accept Electrons from electrodes for anaerobic respiration and that chlorinated aromatic compounds can be dechlorinated in this manner suggest that there may be substantial potential for treating a diversity of contaminants with microbe‐electrode interactions.
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graphite electrode as a sole Electron Donor for reductive dechlorination of tetrachlorethene by geobacter lovleyi
Applied and Environmental Microbiology, 2008Co-Authors: Sarah Strycharz, Trevor L Woodard, Jessica P Johnson, Kelly P Nevin, Robert A Sanford, Frank E Loffler, Derek R LovleyAbstract:The possibility that graphite electrodes can serve as the direct Electron Donor for microbially catalyzed reductive dechlorination was investigated with Geobacter lovleyi. In an initial evaluation of whether G. lovleyi could interact Electronically with graphite electrodes, cells were provided with acetate as the Electron Donor and an electrode as the sole Electron acceptor. Current was produced at levels that were ca. 10-fold lower than those previously reported for Geobacter sulfurreducens under similar conditions, and G. lovleyi anode biofilms were correspondingly thinner. When an electrode poised at −300 mV (versus a standard hydrogen electrode) was provided as the Electron Donor, G. lovleyi effectively reduced fumarate to succinate. The stoichiometry of Electrons consumed to succinate produced was 2:1, the ratio expected if the electrode served as the sole Electron Donor for fumarate reduction. G. lovleyi effectively reduced tetrachloroethene (PCE) to cis-dichloroethene with a poised electrode as the sole Electron Donor at rates comparable to those obtained when acetate serves as the Electron Donor. Cells were less abundant on the electrodes when the electrodes served as an Electron Donor than when they served as an Electron acceptor. PCE was not reduced in controls without cells or when the current supply to cells was interrupted. These results demonstrate that G. lovleyi can use a poised electrode as a direct Electron Donor for reductive dechlorination of PCE. The ability to colocalize dechlorinating microorganisms with electrodes has several potential advantages for bioremediation of subsurface chlorinated contaminants, especially in source zones where Electron Donor delivery is challenging and often limits dechlorination.
R K Banerjee - One of the best experts on this subject based on the ideXlab platform.
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Thiocyanate, a plausible physiological Electron Donor of gastric peroxidase.
The Biochemical journal, 1995Co-Authors: D Das, R K BanerjeeAbstract:Gastric peroxidase (GPO) was purified to apparent homogeneity to characterize its major physiological Electron Donor. The enzyme (RZ = 0.7), with a subunit molecular mass of 50 kDa, is a glycoprotein, with a relative abundance of aspartic and glutamic acid over arginine and lysine. It has a Soret maximum at 412 nm, which is shifted to 426 nm by H2O2 due to formation of compound II. Although the physiological Electron Donors I-, Br- and SCN-, but not Cl-, are oxidized by GPO optimally at acid pH, only I- and SCN- are oxidized appreciably at physiological pH. Considering that the I- concentration in stomach is less than 1 microM, whereas the SCN- concentration is about 250 microM, SCN- may act as a major Electron Donor for GPO. Moreover, SCN- oxidation remains unaltered in the presence of physiological concentrations of other halides. The second-order rate constant for the reaction of GPO with H2O2 (k1) and compound I with SCN- (k2) at pH 7 was found to be 8 x 10(7) M-1.s-1 and 2 x 10(5) M-1.s-1 respectively. GPO has significant pseudocatalase activity also in the presence of I- or Br-, but it is blocked by SCN-. The SCN- oxidation product OSCN- may be reduced back to SCN- by cellular GSH, and GSSG may be reduced back to GSH by glutathione reductase and NADPH. In a system reconstituted with pure glutathione reductase, NADPH, GSH, SCN- and H2O2. GPO-catalysed SCN- oxidation could be coupled to NADPH oxidation. This system where GPO utilizes SCN- as the major physiological Electron Donor may operate efficiently to scavenge intracellular H2O2.