Regulation of the methanogenesis pathways by hydrogen at transcriptomic level

The biomethane formation from 4H2 plus CO2 by pure cultures of two methanogens, Methanocaldococcus fervens and Methanobacterium thermophilum has been studied. The goal of the study was the understanding of H2 regulation of the molecular events associated with biomethane biosynthesis, using metagenomic, pangenomic and metatranscriptomic approaches.Methanogenesis in the autotrophic methanogen Mc. fervens could be easily switched-off and switched on by H2 and CO2 within about an hour. In contrast, the heterotrophic methanogen Mb. thermophilum was practically insensitive to the addition of the H2 and CO2 trigger although this methanogen also converted H2 and CO2 to CH4. From practical points of view, the regulatory function of H2 and CO2 suggests that in the Power-to-Gas (P2G) renewable excess electricity conversion and storage systems the composition of the biomethane-generating methanogenic community is critical for sustainable operation.In addition to managing the specific hydrogenotrophic methanogenesis biochemistry, H2 and CO2 affected several, apparently unrelated metabolic pathways. The redox-regulated overall biochemistry and symbiotic relationships between the methanogenic communities should be explored in order to make the P2G technology, and other applications of methanogens, more efficient.