The role of Carboxydothermus hydrogenoformans in the conversion of calcium phosphate from amorphous to crystalline state

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. \ua9 2014 Haddad et al.Peer reviewed: YesNRC publication: Ye

Continuous bio-hydrogen production from syngas fermentation in a hollow fiber membrane reactor

Bioconversion of syngas to hydrogen was demonstrated in a continuous hollow fiber membrane bioreactor (MBR) utilizing carbon monoxide (CO) as a carbon source. An anaerobic bacterium, carboxydothermus hydrogenoformans, was used to catalyze the water-gas shift reaction (WGS) for the bioconversion of CO to hydrogen. The anaerobic fermentation of syngas in the MBR was continuously operated at various gas loading rate (Qg) and liquid recirculation speeds (Ql). The maximum CO conversion ratio (\u3b7) and hydrogen production rate (HPR) are 97.6% and 0.46 mol/d at a Qg=0.22 mol/d and a fixed nutrient recirculation speed Ql=1 500 mL/min, respectively. During syngas bioconversion, the yield of H2 can reach up to 90%. At the same time, the maximum mass transfer coefficient (kLa) in the MBR is 1.72 h-1.Peer reviewed: YesNRC publication: Ye

A microcosm test for potential mineralization of chlorinated compounds under coupled aerobic/anaerobic conditions

In this study, the feasibility of using a mineralization test under coupled aerobic/anaerobic conditions was demonstrated. The coupling of anaerobic methanogenic and aerobic methanotrophic conditions in a microcosm required the presence of both a carbon source for anaerobic metabolism and oxygen for aerobic metabolism. These requirements were fulfilled by using a slow hydrolyzing organic matter along with intermittent addition of oxygen to the bottle headspace. Perchloroethylene (PCE) mineralization tests confirmed the effectiveness of the proposed methodology as well as PCE mineralization under coupled conditions.NRC publication: Ye

Electricity production from synthesis gas in a multi-electrode microbial fuel cell

BACKGROUND: Electricity production in single-anode/cathode MFCs fed with simulated synthesis gas (syngas) as the sole electron donor has recently been demonstrated. This study evaluated the ability of a multi-anode/cathode MFC fed with syngas to achieve improved volumetric efficiency at several operating temperatures and electrode arrangements. RESULTS: A maximum power density of 33 mW LR-1 (normalized to the anodic compartment volume) and a coulombic efficiency (CE) of 43% was achieved at an operating temperature of 37\ub0C. MFC operation at 50\ub0C resulted in a much lower power density of 10 mW LR-1 and a CE of 15%. The MFC power density was greatly impacted by the electrode arrangement and the highest power density was achieved in a three anode-two cathode (3A-2C) arrangement. CONCLUSION: The multi-electrode design enhanced the performance of a syngas-fed MFC, which could have major economic and operational implications for designing large-scale syngas-fed MFCs. The MFC performance at elevated temperatures was restricted by low microbial activity, implying that a thermophilic rather than a mesophilic inoculum might be required for successful operation under thermophilic conditions. \ua9 2013 Society of Chemical Industry.Peer reviewed: YesNRC publication: Ye

Microbial characteristics and influence factors during anaerobic fermentation for biohydrogen production from CO

The biohydrogen production from anaerobic fermentation was studied with thermophilic bacterium Carboxydothermus hydrogenoformans using carbon monoxide (CO) dissolved in fermentation broth as the substrate. Bacterium growth model, decay efficient and the maximum specific growth rate were observed based on the experimental study of biomass growing, flocculation and microbial characteristics. The results indicated the feasibility of continuous anaerobic fermentation for hydrogen production from CO with C. hydrogenoformans due to its good hydrogen yield and flocculation ability. Furthermore, by investigating the effect of procedure parameters during CO fermentation, the optimal feed/microorganism was proposed and the maximum CO concentration was observed to avoid CO inhibition which was the key factor to consider in the study of continuous biohydrogen production from CO fermentation.Peer reviewed: YesNRC publication: Ye

Fungal pretreatment by Phanerochaete chrysosporium to reduce the inhibition of methanogenesis by dehydroabietic acid

International audienceThe white-rot basidiomycete Phanerochaete chrysosporium BKM-F-1767 was tested for its capacity to degrade dehydroabietic acid (DHA). In anaerobic treatment, this molecule is the most recalcitrant member of the resin acid group, which is known to cause operational problems to anaerobic reactors treating pulp and paper industry wastewaters. In this study the effect of DHA on different parameters, such as growth, ligninolytic enzyme activity, extracellular protein production as well as both glycerol and ammonium consumption by the fungus, was determined. Although the above parameters were affected by the addition of DHA, the results show that the fungus could still produce significant titres of ligninolytic enzymes. The fungus removed 47% of the DHA initially present in the static culture, after 10 days of incubation. Anaerobic toxicity assays showed that the treatment of DHA with P. chrysosporium reduced the methanogenesis and acetogenesis inhibition caused by DHA and allowed improved methane production by the anaerobic bacteria

Performance of a Carboxydothermus hydrogenoformansimmobilizing membrane reactor for syngas upgrading into hydrogen

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 \ub0C) 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 \ub0C), CO pressure (from 1 to 2.5 atm) and CO loading rate (from 1.3 to 16:5 mol Lrxr -1 d-1). Overall, results indicated a relatively constant H2 yield of 92 \ub1 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 Lrxr -1 d-1. Overall, the CO conversion performance in the HFMBR was biokinetically limited, when not limited by gaseliquid 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. Crown Copyright \ua9 2012, Hydrogen Energy Publications, LLC.Peer reviewed: YesNRC publication: Ye

Fungal pretreatment by Phanerochaete chrysosporium to reduce the inhibition of methanogenesis by dehydroabietic acid

International audienceThe white-rot basidiomycete Phanerochaete chrysosporium BKM-F-1767 was tested for its capacity to degrade dehydroabietic acid (DHA). In anaerobic treatment, this molecule is the most recalcitrant member of the resin acid group, which is known to cause operational problems to anaerobic reactors treating pulp and paper industry wastewaters. In this study the effect of DHA on different parameters, such as growth, ligninolytic enzyme activity, extracellular protein production as well as both glycerol and ammonium consumption by the fungus, was determined. Although the above parameters were affected by the addition of DHA, the results show that the fungus could still produce significant titres of ligninolytic enzymes. The fungus removed 47% of the DHA initially present in the static culture, after 10 days of incubation. Anaerobic toxicity assays showed that the treatment of DHA with P. chrysosporium reduced the methanogenesis and acetogenesis inhibition caused by DHA and allowed improved methane production by the anaerobic bacteria