Effectively enhancing acetone concentration and acetone/butanol ratio in ABE fermentation by a glucose/acetate co-substrate system incorporating with glucose limitation and C. acetobutylicum/S. cerevisiae co-culturing

Abstract

A novel glucose/acetate co-substrate system incorporating with C. acetobutylicum/S. cerevisiae co-culturing and glucose limitation was proposed and applied in ABE fermentations by C. acetobutylicum. With this strategy, acetone production was enhanced while NADH dependent butanol synthesis rate was adequately restricted by glucose limitation via decreasing initial glucose concentration in the medium and adaptively adding acetate/S. cerevisiae during solventogenic phase. Under these conditions, acetone production ability of C. acetobutylicum could be fully utilized by delaying butanol inhibition occurrence time; favorable environment for acetone production was created while incomplete ABE fermentation due to glucose limitation avoided. The proposed strategy could arbitrarily control or maximize acetone concentration and acetone/butanol ratio (A/B) in the ranges of 6–12g/L and 0.5–1.0, the maximum values could reach the levels of 11.74g/L and 1.02 which would potentially promote ABE fermentative products flexibility and bio-acetone productions using renewable biomass. The theoretical analysis of A/B ratio based on carbon mass and energy balances showed that, the maximum A/B ratio of 1.04 could be achieved when 60g/L glucose and 12g/L acetate were consumed by C. acetobutylicum, which coincided with the experimental data (1.02) well.