Effect of phenolic compounds on bioconversion of glucose to ethanol by yeast Saccharomyces cerevisiae PE‐2

Abstract

AbstractThe bioconversion of lignocellulosic biomasses to ethanol consists of three main steps: pre‐treatment, enzymatic hydrolysis, and fermentation by microorganisms. Most pre‐treatments induce the formation of substances with a potential inhibitory effect on the microbial metabolism, which may hinder the process. The objective of this study was to investigate the behaviour of Saccharomyces cerevisiae PE‐2 yeast in the presence of four phenolic compounds (vanillin, syringaldehyde, syringic acid, and acetosyringone) resulting from the alkaline pre‐treatment of eucalyptus with green liquor. Eucalyptus is a fast‐growing tree, widely exploited by the paper and pulp industry in Brazil. It was observed that yeast growth and glucose assimilation were affected to an extent directly proportional to the initial amount of vanillin in the medium. Syringaldehyde in a concentration of 1.0 g/L had an adverse effect on the fermentation parameters related to ethanol production, which exhibited a decrease of approximately 50 %. When syringic acid and acetosyringone were used, although the cell growth and glucose consumption profiles were similar to those of the control, they inhibited the conversion at concentrations of 0.1 and 1.0 g/L.