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S R Guiot - One of the best experts on this subject based on the ideXlab platform.
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the role of Carboxydothermus Hydrogenoformans in the conversion of calcium phosphate from amorphous to crystalline state
PLOS ONE, 2014Co-Authors: Mathieu Haddad, S R Guiot, Hojatollah Vali, Jeanne PaquetteAbstract:Two previously unknown modes of biomineralization observed in the presence of Carboxydothermus Hydrogenoformans are presented. Following the addition of NaHCO3 and the formation of an amorphous calcium phosphate precipitate in a DSMZ medium inoculated with C. Hydrogenoformans, two distinct crystalline solids were recovered after 15 and 30 days of incubation. The first of these solids occurred as micrometric clusters of blocky, angular crystals, which were associated with bacterial biofilm. The second solid occurred as 30–50 nm nanorods that were found scattered among the organic products of bacterial lysis. The biphasic mixture of solids was clearly dominated by the first phase. The X-ray diffractometry (XRD) peaks and Fourier transform infrared spectroscopy (FTIR) spectrum of this biphasic material consistently showed features characteristic of Mg-whitlockite. No organic content or protein could be identified by dissolving the solids. In both cases, the mode of biomineralization appears to be biologically induced rather than biologically controlled. Since Mg is known to be a strong inhibitor of the nucleation and growth of CaP, C. Hydrogenoformans may act by providing sites that chelate Mg or form complexes with it, thus decreasing its activity as nucleation and crystal growth inhibitor. The synthesis of whitlockite and nano-HAP-like material by C. Hydrogenoformans demonstrates the versatility of this organism also known for its ability to perform the water-gas shift reaction, and may have applications in bacterially mediated synthesis of CaP materials, as an environmentally friendly alternative process.
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performance of Carboxydothermus Hydrogenoformans in a gas lift reactor for syngas upgrading into hydrogen
International Journal of Hydrogen Energy, 2014Co-Authors: Mathieu Haddad, Ruxandra Cimpoia, S R GuiotAbstract:Abstract The conversion of carbon monoxide (CO) into hydrogen (H2) by a Carboxydothermus Hydrogenoformans pure culture was investigated and optimized in a 35 L gas-lift reactor. The reactor was operated with a continuous supply of gas for 3 months. Reactor performance was evaluated under various operational conditions, such as gas recirculation rates (0.3 and 1.5 L min−1), CO feeding rates (from 0.05 to 0.46 mol L−1reactor day−1) and bacto-peptone addition to the medium. Overall, the H2 yields were constant at 95 ± 1% and 82 ± 1% ( mol H 2 ⋅ mol CO − 1 ) with growth supported by peptone and unsupported respectively, regardless of the operational conditions tested. At the highest biomass density, a maximum CO conversion activity of 0.17 molCO L−1reactor day−1 or 3.79 LCO L−1reactor day−1 was achieved. The ratio of gas recirculation over CO feed flow rates (QR:Qin) was the major parameter that impacted both biological activity and volumetric gas–liquid mass transfer. The CO conversion performance of the gas-lift reactor was kinetically limited over a QR:Qin ratio of 40, and mass transfer limited below that ratio, resulting in a maximum conversion efficiency of 90.4 ± 0.3% and a biological activity of 2.7 ± 0.4 molCO g−1VSS day−1. Overall, the CO conversion performance in the gas-lift reactor was limited by a low cell density, typical of C. Hydrogenoformans planktonic growth. This limitation was found to be the most restrictive factor for higher CO loading rates.
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growth profile of Carboxydothermus Hydrogenoformans on pyruvate
AMB Express, 2013Co-Authors: Mathieu Haddad, Ruxandra Cimpoia, Ya Zhao, S R GuiotAbstract:Carboxydothermus Hydrogenoformans is a thermophilic anaerobic strain most widely known for its ability to produce hydrogen (H2) when grown on carbon monoxide (CO). Although relatively well studied, growth characterization on pyruvate has never been assessed. The present work fully characterizes growth of the bacterium on pyruvate as a sole carbon source. C. Hydrogenoformans demonstrated a growth rate of 0.03 h-1, with pyruvate consumption ranging between 0.21 and 0.48 mol · g-1 volatile suspended solid · d-1. A lag phase was also observed when switching from pyruvate to CO. When grown simultaneously on pyruvate and CO, pyruvate consumption was initiated upon CO depletion. This was attributed to pyruvate oxidation inhibition by CO, and not to a diauxic phenomenom. The strain also showed homoacetogenic activity.
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performance of a Carboxydothermus Hydrogenoformans immobilizing membrane reactor for syngas upgrading into hydrogen
International Journal of Hydrogen Energy, 2013Co-Authors: Mathieu Haddad, Ruxandra Cimpoia, Ya Zhao, S R Guiot, Zhijun LiuAbstract:Abstract Hydrogen conversion of CO by a pure culture of Carboxydothermus Hydrogenoformans was investigated and optimized in a lab-scale hollow fiber membrane bioreactor (HFMBR). The reactor was operated under strict anaerobic, extremely thermophilic (70 °C) conditions with a continuous supply of gas, for four months. Reactor performance was evaluated under various operational conditions, such as liquid velocity (vliq) (13, 65 and 130 m h−1), temperature (70, 65, and 60 °C), CO pressure (from 1 to 2.5 atm) and CO loading rate (from 1.3 to 16 . 5 mol L rxr − 1 d − 1 ). Overall, results indicated a relatively constant H2 yield of 92 ± 4% (mol mol−1) regardless of the operational condition tested. Permeation across the colonized membrane was improved by three orders of magnitude as compared to the abiotic membrane, because of dissolved CO concentration was constantly maintained low in the liquid on the shell side of the membrane as continually depleted by the microorganisms. Once the biofilm was sufficiently developed, a maximum CO conversion activity of 0.44 mol CO g−1 volatile suspended solid (VSS) d−1 was achieved at a pCO of 2 atm or above and a vliq of 65 m h−1. However, this highest activity represented only 15% of the maximal activity potential of the strain under non-limiting conditions, attributed to the low concentration of dissolved CO (0.01–0.07 mM) present in the HFMBR liquid. Higher vliq (130 m h−1) produced shearing stress, which detached a significant portion of the biofilm from the membrane, and/or prevented less sessile growth (57% total biomass as biofilm, as opposed to 84–86% at lower vliq). One may deduce from this work that the volumetric CO conversion performance of such a membrane bioreactor would be at the most in the range of 5 mol CO L rxr − 1 d − 1 . Overall, the CO conversion performance in the HFMBR was biokinetically limited, when not limited by gas–liquid mass transfer. Additionally, over time, membrane fouling and aging decreased membrane permeability such that the CO transfer rate would be the most limiting factor in the long run.
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kinetics of co conversion into h2 by Carboxydothermus Hydrogenoformans
Applied Microbiology and Biotechnology, 2011Co-Authors: Ruxandra Cimpoia, Ya Zhao, Zhijun Liu, S R GuiotAbstract:The objective of this study was to improve the biological water–gas shift reaction for producing hydrogen (H2) by conversion of carbon monoxide (CO) using an anaerobic thermophilic pure strain, Carboxydothermus Hydrogenoformans. Specific hydrogen production rates and yields were investigated at initial biomass densities varying from 5 to 20 mg volatile suspended solid (VSS) L−1. Results showed that the gas–liquid mass transfer limits the CO conversion rate at high biomass concentrations. At 100-rpm agitation and at CO partial pressure of 1 atm, the optimal substrate/biomass ratio must exceed 5 mol CO g−1 biomass VSS in order to avoid gas–liquid substrate transfer limitation. An average H2 yield of 94 ± 3% and a specific hydrogen production rate of ca. 3 mol g−1 VSS day−1 were obtained at initial biomass densities between 5 and 8 mg VSS−1. In addition, CO bioconversion kinetics was assessed at CO partial pressure from 0.16 to 2 atm, corresponding to a dissolved CO concentration at 70°C from 0.09 to 1.1 mM. Specific bioactivity was maximal at 3.5 mol CO g−1 VSS day−1 for a dissolved CO concentration of 0.55 mM in the culture. This optimal concentration is higher than with most other hydrogenogenic carboxydotrophic species.
Holger Dobbek - One of the best experts on this subject based on the ideXlab platform.
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carbon monoxide dehydrogenase reduces cyanate to cyanide
Angewandte Chemie, 2017Co-Authors: Alexandre Ciaccafava, Holger Dobbek, Daria Tombolelli, Lilith Domnik, Jaehun Jeoung, Maria Andrea Mroginski, Ingo Zebger, Peter HildebrandtAbstract:The biocatalytic function of carbon monoxide dehydrogenase (CODH) has a high environmental relevance owing to its ability to reduce CO2. Despite numerous studies on CODH over the past decades, its catalytic mechanism is not yet fully understood. In the present combined spectroscopic and theoretical study, we report first evidences for a cyanate (NCO−) to cyanide (CN−) reduction at the C-cluster. The adduct remains bound to the catalytic center to form the so-called CN−-inhibited state. Notably, this conversion does not occur in crystals of the Carboxydothermus Hydrogenoformans CODH enzyme (CODHIICh), as indicated by the lack of the corresponding CN− stretching mode. The transformation of NCO−, which also acts as an inhibitor of the two-electron-reduced Cred2 state of CODH, could thus mimic CO2 turnover and open new perspectives for elucidation of the detailed catalytic mechanism of CODH.
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when the inhibitor tells more than the substrate the cyanide bound state of a carbon monoxide dehydrogenase
Chemical Science, 2016Co-Authors: Alexandre Ciaccafava, Holger Dobbek, Daria Tombolelli, Lilith Domnik, Jaehun Jeoung, Maria Andrea Mroginski, Ingo Zebger, Jochen Fesseler, Peter HildebrandtAbstract:Carbon monoxide dehydrogenase (CODH) is a key enzyme for reversible CO interconversion. To elucidate structural and mechanistic details of CO binding at the CODH active site (C-cluster), cyanide is frequently used as an iso-electronic substitute and inhibitor. However, previous studies revealed conflicting results on the structure of the cyanide-bound complex and the mechanism of cyanide-inhibition. To address this issue in this work, we have employed IR spectroscopy, crystallography, site directed mutagenesis, and theoretical methods to analyse the cyanide complex of the CODH from Carboxydothermus Hydrogenoformans (CODHIICh). IR spectroscopy demonstrates that a single cyanide binds to the Ni ion. Whereas the inhibitor could be partially removed at elevated temperature, irreversible degradation of the C-cluster occurred in the presence of an excess of cyanide on the long-minute time scale, eventually leading to the formation of [Fe(CN)6]4− and [Ni(CN)4]2− complexes. Theoretical calculations based on a new high-resolution structure of the cyanide-bound CODHIICh indicated that cyanide binding to the Ni ion occurs upon dissociation of the hydroxyl ligand from the Fe1 subsite of the C-cluster. The hydroxyl group is presumably protonated by Lys563 which, unlike to His93, does not form a hydrogen bond with the cyanide ligand. A stable deprotonated e-amino group of Lys563 in the cyanide complex is consistent with the nearly unchanged CN stretching in the Lys563Ala variant of CODHIICh. These findings support the view that the proton channel connecting the solution phase with the active site displays a strict directionality, controlled by the oxidation state of the C-cluster.
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structural basis for electron and methyl group transfer in a methyltransferase system operating in the reductive acetyl coa pathway
Journal of Molecular Biology, 2011Co-Authors: Sebastian Goetzl, Jaehun Jeoung, Sandra E Hennig, Holger DobbekAbstract:Several anaerobic acetogenic, methanogenic, hydrogenogenic, and sulfate-reducing microorganisms are able to use the reductive acetyl-CoA (Wood-Ljungdahl) pathway to convert CO₂ into biomass. The reductive acetyl-CoA pathway consists of two branches connected by the Co/Fe-containing corrinoid iron-sulfur protein (CoFeSP), which transfers a methyl group from a methyltransferase (MeTr)/methyltetrahydrofolate (CH₃-H₄ folate) complex to the reduced Ni-Ni-[4Fe-4S] cluster (cluster A) of acetyl-CoA synthase. We investigated the CoFeSP and MeTr couple of the hydrogenogenic bacterium Carboxydothermus Hydrogenoformans and show that the two proteins are able to catalyze the methyl-group transfer reaction from CH₃-H₄ folate to the Co(I) center of CoFeSP. We determined the crystal structures of both proteins. The structure of CoFeSP includes the previously unresolved N-terminal domain of the large subunit of CoFeSP, revealing a unique four-helix-bundle-like architecture in which a [4Fe-4S] cluster is shielded by hydrophobic amino acids. It further reveals that the corrinoid and the [4Fe-4S] cluster binding domains are mobile, which is mandatory for the postulated electron transfer between them. Furthermore, we solved the crystal structures of apo-MeTr, CH₃-H₄-folate-bound MeTr, and H₄-folate-bound MeTr, revealing a substrate-induced closure of the CH₃-H₄ folate binding cavity of MeTr. We observed three different conformations of Asn200 depending on the substrate bound in the active site, demonstrating its conformational modulation by hydrogen-bonding interactions with the substrate. The observed flexibility could be essential to stabilize the transition state during methyl-group transfer. The conformational space and role of Asn200 are likely conserved in homologous cobalamin-dependent MeTrs such as methionine synthase.
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cooc1 from Carboxydothermus Hydrogenoformans is a nickel binding atpase
Biochemistry, 2009Co-Authors: Jaehun Jeoung, Till Giese, Marlene Grunwald, Holger DobbekAbstract:The maturation of nickel-dependent enzymes requires the participation of several accessory proteins. Typically the hydrolysis of nucleotides is necessary for the final metal transfer steps. The ATPase CooC has been implicated in the insertion of nickel into the Ni,Fe cluster (C cluster) of the carbon monoxide dehydrogenase from Rhodospirillum rubrum. Analysis of the amino acid sequence of CooC suggests the presence of motifs typical for the MinD family of SIMIBI class NTPases, which contain a deviant Walker A motif. The genome of the carboxidotrophic hydrogenogenic bacterium Carboxydothermus Hydrogenoformans contains three open reading frames with distinct sequence homology to CooC from R. rubrum. We overproduced, isolated, and studied CooC1 from C. Hydrogenoformans. As-isolated CooC1 is monomeric in the absence of ligands but dimerizes in the presence of either nickel, ADP, or ATP. CooC1 shows ATPase activity, and the ADP- and ATP-bound dimeric states are distinguished by their stability. The K8A mutant ...
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structural basis of cyanide inhibition of ni fe containing carbon monoxide dehydrogenase
Journal of the American Chemical Society, 2009Co-Authors: Jaehun Jeoung, Holger DobbekAbstract:Carbon monoxide dehydrogenases (CODHs) catalyze the reversible oxidation of carbon monoxide with water to carbon dioxide, two protons, and two electrons. The CODHs of anaerobic microorganisms harbor a complex Ni/Fe/S-containing metal center called a C-cluster in their active site, which activates the substrates water and carbon monoxide, stabilizes an intermediary metal-carboxylate, and transiently stores the two electrons generated in the reaction. Several small molecules have been reported to inhibit carbon monoxide oxidation by CODHs, among which the cyanide anion acts as a slow binding inhibitor. Cyanide is isoelectronic to the substrate carbon monoxide, and its binding to the C-cluster has been reported to involve nickel, nickel and iron, or only iron. We report the crystal structure of CODH-II from Carboxydothermus Hydrogenoformans in complex with cyanide at 1.36 A resolution. The structure reveals that cyanide binds to the C-cluster at an open coordination site completing the square-planar coordination geometry of the nickel ion. While active CODH has a water/hydroxo-ligand bound to an iron ion near nickel, in the cyanide complex the water/hydroxo-ligand is lost and iron occupies a position more close to the nickel ion. Based on the structure, we suggest that the competitive inhibitory character of cyanide originates from it obstruction of carbon monoxide binding to the nickel ion while the slow binding inhibition is due to a conformational change of the protein during which the water/hydroxo-ligand bound to iron is lost.
Mathieu Haddad - One of the best experts on this subject based on the ideXlab platform.
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the role of Carboxydothermus Hydrogenoformans in the conversion of calcium phosphate from amorphous to crystalline state
PLOS ONE, 2014Co-Authors: Mathieu Haddad, S R Guiot, Hojatollah Vali, Jeanne PaquetteAbstract:Two previously unknown modes of biomineralization observed in the presence of Carboxydothermus Hydrogenoformans are presented. Following the addition of NaHCO3 and the formation of an amorphous calcium phosphate precipitate in a DSMZ medium inoculated with C. Hydrogenoformans, two distinct crystalline solids were recovered after 15 and 30 days of incubation. The first of these solids occurred as micrometric clusters of blocky, angular crystals, which were associated with bacterial biofilm. The second solid occurred as 30–50 nm nanorods that were found scattered among the organic products of bacterial lysis. The biphasic mixture of solids was clearly dominated by the first phase. The X-ray diffractometry (XRD) peaks and Fourier transform infrared spectroscopy (FTIR) spectrum of this biphasic material consistently showed features characteristic of Mg-whitlockite. No organic content or protein could be identified by dissolving the solids. In both cases, the mode of biomineralization appears to be biologically induced rather than biologically controlled. Since Mg is known to be a strong inhibitor of the nucleation and growth of CaP, C. Hydrogenoformans may act by providing sites that chelate Mg or form complexes with it, thus decreasing its activity as nucleation and crystal growth inhibitor. The synthesis of whitlockite and nano-HAP-like material by C. Hydrogenoformans demonstrates the versatility of this organism also known for its ability to perform the water-gas shift reaction, and may have applications in bacterially mediated synthesis of CaP materials, as an environmentally friendly alternative process.
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performance of Carboxydothermus Hydrogenoformans in a gas lift reactor for syngas upgrading into hydrogen
International Journal of Hydrogen Energy, 2014Co-Authors: Mathieu Haddad, Ruxandra Cimpoia, S R GuiotAbstract:Abstract The conversion of carbon monoxide (CO) into hydrogen (H2) by a Carboxydothermus Hydrogenoformans pure culture was investigated and optimized in a 35 L gas-lift reactor. The reactor was operated with a continuous supply of gas for 3 months. Reactor performance was evaluated under various operational conditions, such as gas recirculation rates (0.3 and 1.5 L min−1), CO feeding rates (from 0.05 to 0.46 mol L−1reactor day−1) and bacto-peptone addition to the medium. Overall, the H2 yields were constant at 95 ± 1% and 82 ± 1% ( mol H 2 ⋅ mol CO − 1 ) with growth supported by peptone and unsupported respectively, regardless of the operational conditions tested. At the highest biomass density, a maximum CO conversion activity of 0.17 molCO L−1reactor day−1 or 3.79 LCO L−1reactor day−1 was achieved. The ratio of gas recirculation over CO feed flow rates (QR:Qin) was the major parameter that impacted both biological activity and volumetric gas–liquid mass transfer. The CO conversion performance of the gas-lift reactor was kinetically limited over a QR:Qin ratio of 40, and mass transfer limited below that ratio, resulting in a maximum conversion efficiency of 90.4 ± 0.3% and a biological activity of 2.7 ± 0.4 molCO g−1VSS day−1. Overall, the CO conversion performance in the gas-lift reactor was limited by a low cell density, typical of C. Hydrogenoformans planktonic growth. This limitation was found to be the most restrictive factor for higher CO loading rates.
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compared performance of hyperthermophilic hollow fiber membrane and gas lift bioreactors using a pure Carboxydothermus Hydrogenoformans culture for syngas upgrading into hydrogen
2014Co-Authors: Ruxandra Cimpoia, Mathieu Haddad, Ya Zhao, R SergeAbstract:(pCO) (from 1 to 2.5 atm), CO loading rate (from 1.3 to 16.5 mol CO per liter of reactor (rxr) and per day), gas recirculation rates (0.3 and 1.5 L·min –1 ), CO feeding rates (from 0.05 to 0.46 mol·L – 1 rxr·d –1 ), and bacto-peptone addition to the medium. Overall, HFMBR results indicated a relatively constant H2 yield of 92±4% (mol H2·mol –1 CO), regardless of the operational condition tested. Permeation across the colonized membrane was improved by three orders of magnitude as compared to the abiotic membrane. Once the biofilm was sufficiently developed, a maximum CO conversion activity of 0.44 mol CO·g –1 volatile suspended solid (VSS)·d –1 was achieved at a pCO of 2 atm or above and a liquid velocity of 65 m·h –1 . In GLR the H2 yields were approximately constant at 100±6% (mol H2·mol–1 CO) with unsupported growth, at any operational conditions tested. At the highest biomass density, a maximum CO conversion activity of 0.22 molCO·L -1 rxr·d -1 was achieved. Overall, a low cell density, typical of C. Hydrogenoformans growth, limited the CO conversion performance. This limitation was found to be the most restrictive factor for higher CO loading rates for GLR systems.
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growth profile of Carboxydothermus Hydrogenoformans on pyruvate
AMB Express, 2013Co-Authors: Mathieu Haddad, Ruxandra Cimpoia, Ya Zhao, S R GuiotAbstract:Carboxydothermus Hydrogenoformans is a thermophilic anaerobic strain most widely known for its ability to produce hydrogen (H2) when grown on carbon monoxide (CO). Although relatively well studied, growth characterization on pyruvate has never been assessed. The present work fully characterizes growth of the bacterium on pyruvate as a sole carbon source. C. Hydrogenoformans demonstrated a growth rate of 0.03 h-1, with pyruvate consumption ranging between 0.21 and 0.48 mol · g-1 volatile suspended solid · d-1. A lag phase was also observed when switching from pyruvate to CO. When grown simultaneously on pyruvate and CO, pyruvate consumption was initiated upon CO depletion. This was attributed to pyruvate oxidation inhibition by CO, and not to a diauxic phenomenom. The strain also showed homoacetogenic activity.
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performance of a Carboxydothermus Hydrogenoformans immobilizing membrane reactor for syngas upgrading into hydrogen
International Journal of Hydrogen Energy, 2013Co-Authors: Mathieu Haddad, Ruxandra Cimpoia, Ya Zhao, S R Guiot, Zhijun LiuAbstract:Abstract Hydrogen conversion of CO by a pure culture of Carboxydothermus Hydrogenoformans was investigated and optimized in a lab-scale hollow fiber membrane bioreactor (HFMBR). The reactor was operated under strict anaerobic, extremely thermophilic (70 °C) conditions with a continuous supply of gas, for four months. Reactor performance was evaluated under various operational conditions, such as liquid velocity (vliq) (13, 65 and 130 m h−1), temperature (70, 65, and 60 °C), CO pressure (from 1 to 2.5 atm) and CO loading rate (from 1.3 to 16 . 5 mol L rxr − 1 d − 1 ). Overall, results indicated a relatively constant H2 yield of 92 ± 4% (mol mol−1) regardless of the operational condition tested. Permeation across the colonized membrane was improved by three orders of magnitude as compared to the abiotic membrane, because of dissolved CO concentration was constantly maintained low in the liquid on the shell side of the membrane as continually depleted by the microorganisms. Once the biofilm was sufficiently developed, a maximum CO conversion activity of 0.44 mol CO g−1 volatile suspended solid (VSS) d−1 was achieved at a pCO of 2 atm or above and a vliq of 65 m h−1. However, this highest activity represented only 15% of the maximal activity potential of the strain under non-limiting conditions, attributed to the low concentration of dissolved CO (0.01–0.07 mM) present in the HFMBR liquid. Higher vliq (130 m h−1) produced shearing stress, which detached a significant portion of the biofilm from the membrane, and/or prevented less sessile growth (57% total biomass as biofilm, as opposed to 84–86% at lower vliq). One may deduce from this work that the volumetric CO conversion performance of such a membrane bioreactor would be at the most in the range of 5 mol CO L rxr − 1 d − 1 . Overall, the CO conversion performance in the HFMBR was biokinetically limited, when not limited by gas–liquid mass transfer. Additionally, over time, membrane fouling and aging decreased membrane permeability such that the CO transfer rate would be the most limiting factor in the long run.
Ya Zhao - One of the best experts on this subject based on the ideXlab platform.
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compared performance of hyperthermophilic hollow fiber membrane and gas lift bioreactors using a pure Carboxydothermus Hydrogenoformans culture for syngas upgrading into hydrogen
2014Co-Authors: Ruxandra Cimpoia, Mathieu Haddad, Ya Zhao, R SergeAbstract:(pCO) (from 1 to 2.5 atm), CO loading rate (from 1.3 to 16.5 mol CO per liter of reactor (rxr) and per day), gas recirculation rates (0.3 and 1.5 L·min –1 ), CO feeding rates (from 0.05 to 0.46 mol·L – 1 rxr·d –1 ), and bacto-peptone addition to the medium. Overall, HFMBR results indicated a relatively constant H2 yield of 92±4% (mol H2·mol –1 CO), regardless of the operational condition tested. Permeation across the colonized membrane was improved by three orders of magnitude as compared to the abiotic membrane. Once the biofilm was sufficiently developed, a maximum CO conversion activity of 0.44 mol CO·g –1 volatile suspended solid (VSS)·d –1 was achieved at a pCO of 2 atm or above and a liquid velocity of 65 m·h –1 . In GLR the H2 yields were approximately constant at 100±6% (mol H2·mol–1 CO) with unsupported growth, at any operational conditions tested. At the highest biomass density, a maximum CO conversion activity of 0.22 molCO·L -1 rxr·d -1 was achieved. Overall, a low cell density, typical of C. Hydrogenoformans growth, limited the CO conversion performance. This limitation was found to be the most restrictive factor for higher CO loading rates for GLR systems.
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growth profile of Carboxydothermus Hydrogenoformans on pyruvate
AMB Express, 2013Co-Authors: Mathieu Haddad, Ruxandra Cimpoia, Ya Zhao, S R GuiotAbstract:Carboxydothermus Hydrogenoformans is a thermophilic anaerobic strain most widely known for its ability to produce hydrogen (H2) when grown on carbon monoxide (CO). Although relatively well studied, growth characterization on pyruvate has never been assessed. The present work fully characterizes growth of the bacterium on pyruvate as a sole carbon source. C. Hydrogenoformans demonstrated a growth rate of 0.03 h-1, with pyruvate consumption ranging between 0.21 and 0.48 mol · g-1 volatile suspended solid · d-1. A lag phase was also observed when switching from pyruvate to CO. When grown simultaneously on pyruvate and CO, pyruvate consumption was initiated upon CO depletion. This was attributed to pyruvate oxidation inhibition by CO, and not to a diauxic phenomenom. The strain also showed homoacetogenic activity.
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performance of a Carboxydothermus Hydrogenoformans immobilizing membrane reactor for syngas upgrading into hydrogen
International Journal of Hydrogen Energy, 2013Co-Authors: Mathieu Haddad, Ruxandra Cimpoia, Ya Zhao, S R Guiot, Zhijun LiuAbstract:Abstract Hydrogen conversion of CO by a pure culture of Carboxydothermus Hydrogenoformans was investigated and optimized in a lab-scale hollow fiber membrane bioreactor (HFMBR). The reactor was operated under strict anaerobic, extremely thermophilic (70 °C) conditions with a continuous supply of gas, for four months. Reactor performance was evaluated under various operational conditions, such as liquid velocity (vliq) (13, 65 and 130 m h−1), temperature (70, 65, and 60 °C), CO pressure (from 1 to 2.5 atm) and CO loading rate (from 1.3 to 16 . 5 mol L rxr − 1 d − 1 ). Overall, results indicated a relatively constant H2 yield of 92 ± 4% (mol mol−1) regardless of the operational condition tested. Permeation across the colonized membrane was improved by three orders of magnitude as compared to the abiotic membrane, because of dissolved CO concentration was constantly maintained low in the liquid on the shell side of the membrane as continually depleted by the microorganisms. Once the biofilm was sufficiently developed, a maximum CO conversion activity of 0.44 mol CO g−1 volatile suspended solid (VSS) d−1 was achieved at a pCO of 2 atm or above and a vliq of 65 m h−1. However, this highest activity represented only 15% of the maximal activity potential of the strain under non-limiting conditions, attributed to the low concentration of dissolved CO (0.01–0.07 mM) present in the HFMBR liquid. Higher vliq (130 m h−1) produced shearing stress, which detached a significant portion of the biofilm from the membrane, and/or prevented less sessile growth (57% total biomass as biofilm, as opposed to 84–86% at lower vliq). One may deduce from this work that the volumetric CO conversion performance of such a membrane bioreactor would be at the most in the range of 5 mol CO L rxr − 1 d − 1 . Overall, the CO conversion performance in the HFMBR was biokinetically limited, when not limited by gas–liquid mass transfer. Additionally, over time, membrane fouling and aging decreased membrane permeability such that the CO transfer rate would be the most limiting factor in the long run.
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kinetics of co conversion into h2 by Carboxydothermus Hydrogenoformans
Applied Microbiology and Biotechnology, 2011Co-Authors: Ruxandra Cimpoia, Ya Zhao, Zhijun Liu, S R GuiotAbstract:The objective of this study was to improve the biological water–gas shift reaction for producing hydrogen (H2) by conversion of carbon monoxide (CO) using an anaerobic thermophilic pure strain, Carboxydothermus Hydrogenoformans. Specific hydrogen production rates and yields were investigated at initial biomass densities varying from 5 to 20 mg volatile suspended solid (VSS) L−1. Results showed that the gas–liquid mass transfer limits the CO conversion rate at high biomass concentrations. At 100-rpm agitation and at CO partial pressure of 1 atm, the optimal substrate/biomass ratio must exceed 5 mol CO g−1 biomass VSS in order to avoid gas–liquid substrate transfer limitation. An average H2 yield of 94 ± 3% and a specific hydrogen production rate of ca. 3 mol g−1 VSS day−1 were obtained at initial biomass densities between 5 and 8 mg VSS−1. In addition, CO bioconversion kinetics was assessed at CO partial pressure from 0.16 to 2 atm, corresponding to a dissolved CO concentration at 70°C from 0.09 to 1.1 mM. Specific bioactivity was maximal at 3.5 mol CO g−1 VSS day−1 for a dissolved CO concentration of 0.55 mM in the culture. This optimal concentration is higher than with most other hydrogenogenic carboxydotrophic species.
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orthogonal optimization of Carboxydothermus Hydrogenoformans culture medium for hydrogen production from carbon monoxide by biological water gas shift reaction
International Journal of Hydrogen Energy, 2011Co-Authors: Ruxandra Cimpoia, Ya Zhao, Zhijun Liu, S R GuiotAbstract:Abstract The objective of the present study was to investigate the optimal nutritional requirements for hydrogen production from carbon monoxide by biological water-gas shift (WGS) reaction with Carboxydothermus Hydrogenoformans using orthogonal layout methods. Cultures of C. Hydrogenoformans on the medium as formulated by the strain supplier (Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH) unexpectedly showed a large content in inorganic material. This was confirmed by the rather elevated levels of calcium and phosphorus contained in the grown biomass. As an excessive production of those minerals may interfere with the growth and catabolism rates as well as clog up biofilm-based reactors, it was desirable to minimize the mineral accumulation during growth, while keeping at maximal levels both the H2 yield and the specific H2 production rate (SHPR). PO 4 3 − , HCO 3 − , Ca2+ and Mg2+ were considered as potentially the major factors of the mineral accumulation. The experiments were designed according to the Taguchi’s orthogonal method, using the above factors at three levels, and considering the culture mineral content, the H2 yield and the SHPR as optimization criteria. Optimal concentrations of PO 4 3 − , HCO 3 − , Ca2+ and Mg2+ were determined as (mM): 1.0, 5.0, 0.1 and 0.5, respectively. Under those culture conditions, Ca + P content decreased from 55.6 ± 1.8 to 9.5 ± 3% while the highest H2 yield at 90.9 ± 1.2% and SHPR at 0.85 ± 0.06 mol H2 g−1 VSS d−1 were achieved in bottle batch tests at 100% CO headspace atmosphere, neutral pH, a temperature of 70 °C, and an agitation of 100 rpm.
Ruxandra Cimpoia - One of the best experts on this subject based on the ideXlab platform.
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performance of Carboxydothermus Hydrogenoformans in a gas lift reactor for syngas upgrading into hydrogen
International Journal of Hydrogen Energy, 2014Co-Authors: Mathieu Haddad, Ruxandra Cimpoia, S R GuiotAbstract:Abstract The conversion of carbon monoxide (CO) into hydrogen (H2) by a Carboxydothermus Hydrogenoformans pure culture was investigated and optimized in a 35 L gas-lift reactor. The reactor was operated with a continuous supply of gas for 3 months. Reactor performance was evaluated under various operational conditions, such as gas recirculation rates (0.3 and 1.5 L min−1), CO feeding rates (from 0.05 to 0.46 mol L−1reactor day−1) and bacto-peptone addition to the medium. Overall, the H2 yields were constant at 95 ± 1% and 82 ± 1% ( mol H 2 ⋅ mol CO − 1 ) with growth supported by peptone and unsupported respectively, regardless of the operational conditions tested. At the highest biomass density, a maximum CO conversion activity of 0.17 molCO L−1reactor day−1 or 3.79 LCO L−1reactor day−1 was achieved. The ratio of gas recirculation over CO feed flow rates (QR:Qin) was the major parameter that impacted both biological activity and volumetric gas–liquid mass transfer. The CO conversion performance of the gas-lift reactor was kinetically limited over a QR:Qin ratio of 40, and mass transfer limited below that ratio, resulting in a maximum conversion efficiency of 90.4 ± 0.3% and a biological activity of 2.7 ± 0.4 molCO g−1VSS day−1. Overall, the CO conversion performance in the gas-lift reactor was limited by a low cell density, typical of C. Hydrogenoformans planktonic growth. This limitation was found to be the most restrictive factor for higher CO loading rates.
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compared performance of hyperthermophilic hollow fiber membrane and gas lift bioreactors using a pure Carboxydothermus Hydrogenoformans culture for syngas upgrading into hydrogen
2014Co-Authors: Ruxandra Cimpoia, Mathieu Haddad, Ya Zhao, R SergeAbstract:(pCO) (from 1 to 2.5 atm), CO loading rate (from 1.3 to 16.5 mol CO per liter of reactor (rxr) and per day), gas recirculation rates (0.3 and 1.5 L·min –1 ), CO feeding rates (from 0.05 to 0.46 mol·L – 1 rxr·d –1 ), and bacto-peptone addition to the medium. Overall, HFMBR results indicated a relatively constant H2 yield of 92±4% (mol H2·mol –1 CO), regardless of the operational condition tested. Permeation across the colonized membrane was improved by three orders of magnitude as compared to the abiotic membrane. Once the biofilm was sufficiently developed, a maximum CO conversion activity of 0.44 mol CO·g –1 volatile suspended solid (VSS)·d –1 was achieved at a pCO of 2 atm or above and a liquid velocity of 65 m·h –1 . In GLR the H2 yields were approximately constant at 100±6% (mol H2·mol–1 CO) with unsupported growth, at any operational conditions tested. At the highest biomass density, a maximum CO conversion activity of 0.22 molCO·L -1 rxr·d -1 was achieved. Overall, a low cell density, typical of C. Hydrogenoformans growth, limited the CO conversion performance. This limitation was found to be the most restrictive factor for higher CO loading rates for GLR systems.
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growth profile of Carboxydothermus Hydrogenoformans on pyruvate
AMB Express, 2013Co-Authors: Mathieu Haddad, Ruxandra Cimpoia, Ya Zhao, S R GuiotAbstract:Carboxydothermus Hydrogenoformans is a thermophilic anaerobic strain most widely known for its ability to produce hydrogen (H2) when grown on carbon monoxide (CO). Although relatively well studied, growth characterization on pyruvate has never been assessed. The present work fully characterizes growth of the bacterium on pyruvate as a sole carbon source. C. Hydrogenoformans demonstrated a growth rate of 0.03 h-1, with pyruvate consumption ranging between 0.21 and 0.48 mol · g-1 volatile suspended solid · d-1. A lag phase was also observed when switching from pyruvate to CO. When grown simultaneously on pyruvate and CO, pyruvate consumption was initiated upon CO depletion. This was attributed to pyruvate oxidation inhibition by CO, and not to a diauxic phenomenom. The strain also showed homoacetogenic activity.
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performance of a Carboxydothermus Hydrogenoformans immobilizing membrane reactor for syngas upgrading into hydrogen
International Journal of Hydrogen Energy, 2013Co-Authors: Mathieu Haddad, Ruxandra Cimpoia, Ya Zhao, S R Guiot, Zhijun LiuAbstract:Abstract Hydrogen conversion of CO by a pure culture of Carboxydothermus Hydrogenoformans was investigated and optimized in a lab-scale hollow fiber membrane bioreactor (HFMBR). The reactor was operated under strict anaerobic, extremely thermophilic (70 °C) conditions with a continuous supply of gas, for four months. Reactor performance was evaluated under various operational conditions, such as liquid velocity (vliq) (13, 65 and 130 m h−1), temperature (70, 65, and 60 °C), CO pressure (from 1 to 2.5 atm) and CO loading rate (from 1.3 to 16 . 5 mol L rxr − 1 d − 1 ). Overall, results indicated a relatively constant H2 yield of 92 ± 4% (mol mol−1) regardless of the operational condition tested. Permeation across the colonized membrane was improved by three orders of magnitude as compared to the abiotic membrane, because of dissolved CO concentration was constantly maintained low in the liquid on the shell side of the membrane as continually depleted by the microorganisms. Once the biofilm was sufficiently developed, a maximum CO conversion activity of 0.44 mol CO g−1 volatile suspended solid (VSS) d−1 was achieved at a pCO of 2 atm or above and a vliq of 65 m h−1. However, this highest activity represented only 15% of the maximal activity potential of the strain under non-limiting conditions, attributed to the low concentration of dissolved CO (0.01–0.07 mM) present in the HFMBR liquid. Higher vliq (130 m h−1) produced shearing stress, which detached a significant portion of the biofilm from the membrane, and/or prevented less sessile growth (57% total biomass as biofilm, as opposed to 84–86% at lower vliq). One may deduce from this work that the volumetric CO conversion performance of such a membrane bioreactor would be at the most in the range of 5 mol CO L rxr − 1 d − 1 . Overall, the CO conversion performance in the HFMBR was biokinetically limited, when not limited by gas–liquid mass transfer. Additionally, over time, membrane fouling and aging decreased membrane permeability such that the CO transfer rate would be the most limiting factor in the long run.
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kinetics of co conversion into h2 by Carboxydothermus Hydrogenoformans
Applied Microbiology and Biotechnology, 2011Co-Authors: Ruxandra Cimpoia, Ya Zhao, Zhijun Liu, S R GuiotAbstract:The objective of this study was to improve the biological water–gas shift reaction for producing hydrogen (H2) by conversion of carbon monoxide (CO) using an anaerobic thermophilic pure strain, Carboxydothermus Hydrogenoformans. Specific hydrogen production rates and yields were investigated at initial biomass densities varying from 5 to 20 mg volatile suspended solid (VSS) L−1. Results showed that the gas–liquid mass transfer limits the CO conversion rate at high biomass concentrations. At 100-rpm agitation and at CO partial pressure of 1 atm, the optimal substrate/biomass ratio must exceed 5 mol CO g−1 biomass VSS in order to avoid gas–liquid substrate transfer limitation. An average H2 yield of 94 ± 3% and a specific hydrogen production rate of ca. 3 mol g−1 VSS day−1 were obtained at initial biomass densities between 5 and 8 mg VSS−1. In addition, CO bioconversion kinetics was assessed at CO partial pressure from 0.16 to 2 atm, corresponding to a dissolved CO concentration at 70°C from 0.09 to 1.1 mM. Specific bioactivity was maximal at 3.5 mol CO g−1 VSS day−1 for a dissolved CO concentration of 0.55 mM in the culture. This optimal concentration is higher than with most other hydrogenogenic carboxydotrophic species.