Effects of Saccharomyces Cerevisiae Quorum Sensing Signal Molecules on Ethanol Production in Bioethanol Fermentation Process

Abstract

In this study, the concentrations of S. cerevisiae quorum sensing signal molecules (QSMs) were monitored, and the effects of exogenous S. cerevisiae QSMs on sole fermentation of S. cerevisiae and co-fermentation of S. cerevisiae and Lactobacillus plantarum were explored. The results showed that the concentrations of the three signal molecules (i.e., 2-phenylethanol (2-PE), tyrosol and tryptophan) produced by S. cerevisiae increased with the increasing of bacterial density, and tended to stablize at 144 h, which were 118.02, 32.05 and 1.93 mg/L, respectively. Among the three signaling molecules, only 2-PE promoted the ethanol production capacity of S. cerevisiae. The ethanol concentration of the sole fermentation of S. cerevisiae added with 120 mg/L 2-PE reached 3.2 g/L in 9 h, which was 59% higher than that of the control group. Moreover, 2-PE reduced the negative impact of Lactobacillus plantarum on S. cerevisiae. Within the co-fermentation of 12 h, the ethanol concentration of the group addition of 2-PE reached 5.6 g/L, and no significant difference was observed compared to the control group. Simultaneously, the yeast budding rate was also restored to 28.51%. qRT-PCR results showed that sole fermentation of S. cerevisiae for 9 h with 2-PE addition while the relative expression levels of ethanol dehydrogenase gene ADH1 in S. cerevisiae decreased by 25% and the relative expression levels of MLS1, CIT2, IDH1 and CIT1 decreased by 26%, 30%, 22%, and 18%, respectively. The glyoxylic and tricarboxylic acid cycles were greatly inhibited, promoting the accumulation of ethanol production. The results of this study provide novel basic data for the contamination prevention in the industrialized bioethanol production by using QSMs instead of antibiotics.

Keywords: Saccharomyces cerevisiae, quorum sensing signaling molecules, bioethanol, 2-phenylethanol, Lactobacillus plantarum