Methanol supply speeds up synthesis gas fermentation by methylotrophic-acetogenic bacterium, Eubacterium limosum KIST612

This study analyzed the effect of methanol on the metabolism of syngas components (i.e., H₂ and CO) by the syngas fermenting acetogenic strain E. limosum KIST612. The culture characteristics and relevant proteomic expressions (as fold changes) were carefully analyzed under CO/CO₂ and H₂/CO₂ conditions with and without methanol addition, as well as, under methanol/CO₂ conditions. The culture characteristics (specific growth rate and H₂ consumption rate) under H₂/CO₂ conditions were greatly enhanced in the presence of methanol, by 4.0 and 2.7 times, respectively. However, the promoting effect of methanol was not significant under CO/CO₂ conditions. Proteomic fold changes in most enzyme expression levels in the Wood-Ljungdahl pathway and chemiosmotic energy conservation also exhibited high correspondence between methanol and H₂/CO₂ but not between methanol and CO/CO₂. These findings suggest the advantages of methanol addition to H₂/CO₂ for biomass enhancement and faster consumption of gaseous substrates during syngas fermentation.