Susceptibility of Saccharomyces cerevisiae to inhibitors and impact on bioethanol production yield

Abstract

There have been increasing concerns in developing countries over the competition between food and energy resulting from the production of bioethanol from edible biomass. Second generation lignocellulose feedstock is an attractive alternative, as bioethanol can be produced from non-edible materials. However, the pretreatment required for hydrolysis of lignocellulose into pentose and hexose sugars often results in the production of inhibitors likely to impede the activity of Saccharomyces cerevisiae during bioethanol production. This study aims to investigate the comparative inhibitory effects of acetic acid and vanillin on the viability of S. cerevisiae and the production yield of bioethanol. The fermentation broth was spiked with different concentrations of vanillin or acetic acid were and the bioethanol concentration were monitored over time and correlated with cell viability. The results showed that although S. cerevisiae was mostly susceptible by vanillin compared to acetic acid, the inhibitory effect of acetic acid on S cerevisiae had a more severe influence on the final bioethanol yield after 12 h (42.8% reduction) than vanillin (33.3%). The latter was ascribed to the simultaneous production of weak acids during the fermentation process. The viability test has shown that S. cerevisiae can adapt to the presence of inhibitors over 12 h and at lower concentrations (2 g/l vanillin and 4 g/l acetic acid) the effect of inhibitors on S. cerevisiae and ethanol production yield can be overcome by the adaptation of the yeast