One-carbon substrate-based biohydrogen production: Microbes, mechanism, and productivity

Among four basic mechanisms for biological hydrogen (H-2) production, dark fermentation has been considered to show the highest hydrogen evolution rate (HER). H-2 production from one-carbon (Cl) compounds such as formate and carbon monoxide (CO) is promising because formate is an efficient H-2 carrier, and the utilization of CO-containing syngas or industrial waste gas may render the industrial biohydrogen production process cost-effective. A variety of microbes with the formate hydrogen lyase (FHL) system have been identified from phylogenetically diverse groups of archaea and bacteria, and numerous efforts have been undertaken to improve the HER for formate through strain optimization and bioprocess development. CO-dependent H-2 production has been investigated to enhance the H-2 productivity of various carboxydotrophs via an increase in CO gas liquid mass transfer rates and the construction of genetically modified strains. Hydrogenogenic CO-conversion has been applied to syngas and by-product gas of the steel-mill process, and this low-cost feedstock has shown to be promising in the production of biomass and H-2. Here, we focus on recent advances in the isolation of novel phylogenetic groups utilizing formate or CO, the remarkable genetic engineering that enhances H-2 productivity, and the practical implementation of H-2 production from Cl substrates. (C) 2014 Elsevier Inc. All rights reserved.