Abstract
Hydrogen is a key intermediate element in microbial electrosynthesis as a mediator of the reduction of carbon dioxide (CO2) into added value compounds. In the present work we aimed at studying the biological production of hydrogen in biocathodes operated at − 1.0 V vs. Ag/AgCl, using a highly comparable technology and CO2 as carbon feedstock. Ten bacterial strains were chosen from genera Rhodobacter, Rhodopseudomonas, Rhodocyclus, Desulfovibrio and Sporomusa, all described as hydrogen producing candidates. Monospecific biofilms were formed on carbon cloth cathodes and hydrogen evolution was constantly monitored using a microsensor. Eight over ten bacteria strains showed electroactivity and H2 production rates increased significantly (two to eightfold) compared to abiotic conditions for two of them (Desulfovibrio paquesii and Desulfovibrio desulfuricans). D. paquesii DSM 16681 exhibited the highest production rate (45.6 ± 18.8 µM min−1) compared to abiotic conditions (5.5 ± 0.6 µM min−1), although specific production rates (per 16S rRNA copy) were similar to those obtained for other strains. This study demonstrated that many microorganisms are suspected to participate in net hydrogen production but inherent differences among strains do occur, which are relevant for future developments of resilient biofilm coated cathodes as a stable hydrogen production platform in microbial electrosynthesis.
Highlights
Hydrogen is a key intermediate element in microbial electrosynthesis as a mediator of the reduction of carbon dioxide (CO2) into added value compounds
The authors demonstrated that the former presence of microorganisms in the reactor had changed the electrode surface via metal deposition leading to an increased H 2 production[19]
In this study we presented an evaluation of ten different bacteria as a first step in the development of a stable H 2-evolving platform for microbial electrosynthesis
Summary
Hydrogen is a key intermediate element in microbial electrosynthesis as a mediator of the reduction of carbon dioxide (CO2) into added value compounds. Several studies have proposed hydrogen ( H2) as the principal electron donor intermediary in the production of commodity chemicals from carbon dioxide and e lectricity[9,10,11] Molecules such as H2, carbon monoxide (CO) and formate are the most preferable for microbial catalysts[12]. Free enzymes (hydrogenases and formate dehydrogenases) previously released by microorganisms[20,21] could be deposited in the electrode surface reinforcing H 2 production yields Another feasible strategy aiming to improve H 2 production in biocathodes is the integration of low-cost metal-based cathode materials such as cobalt phosphide, molybdenum disulfide and nickel-molybdenum with putatively electroactive microorganisms. Its integration with the required conditions for microbial growth might cause toxicity towards m icroorganisms[22], some of these materials have been demonstrated as a promising and biocompatible electrocatalytic H 2-producing platform, while combining with CO2-reducing and H2-utilizing bacteria (like S. ovata and M. maripaludis) ensuring higher value-added chemicals p roduction[23]
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