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

Abstract

This study analyzed the effect of methanol on the metabolism of syngas components (i.e., H-2 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 H-2/CO2 conditions with and without methanol addition, as well as, under methanol/CO2 conditions. The culture characteristics (specific growth rate and H-2 consumption rate) under H-2/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 H-2/CO2 but not between methanol and CO/CO2. These findings suggest the advantages of methanol addition to H-2/CO2 for biomass enhancement and faster consumption of gaseous substrates during syngas fermentation.