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., H 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/CO and H/CO conditions with and without methanol addition, as well as, under methanol/CO conditions. The culture characteristics (specific growth rate and H consumption rate) under H/CO 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/CO 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 H/CO but not between methanol and CO/CO. These findings suggest the advantages of methanol addition to H/CO for biomass enhancement and faster consumption of gaseous substrates during syngas fermentation.