A Peculiar Stimulatory Effect of Acetic Acid on Ethanol Fermentation of Saccharomyces cerevisiae

Abstract

In the integrated ethanol-methane fermentation process, acetic acid was accumulated once the process runs badly. Ethanol production per DCW (dry cell weight) was increased when low concentrations of acetic acid was present, where glycerol yields significantly decreased. To explain it, we monitored intracellular energy factors (ATP, ADP and AMP) and cofactors (NAD+, NADH and NADP) at pH 4.5. In the presence of 60 mM acetic acid at pH 4.5, ATP per unit DCW increased by 47.52% compared to the control, while NADH per unit DCW decreased by 38.64%. Furthermore, in the presence of 90 mM acetic acid, the trehalose per unit DCW increased by 55.81% compared to the control. In addition, the fluorescence intensity of membrane potential increased along with the increase of acetic acid. So the positive effect of acetic acid on ethanol fermentation made the integrated process more applied.