Molecular Mechanisms of Ethanol Tolerance in Saccharomyces cerevisiae

Abstract

The yeast Saccharomyces cerevisiae is a superb ethanol producer, yet sensitive to ethanol at higher concentrations, especially under high gravity or very high gravity fermentation conditions. Although significant efforts have been made to study ethanol stress response in past decades, molecular mechanisms of ethanol tolerance are not well known. With developments of genome sequencing and genomic technologies, our understanding of yeast biology has been revolutionarily advanced. Additional evidence of ethanol tolerance has been discovered involving numerous genes with variety of functions, multiple loci, and complex interactions, as well as signal transduction pathways and regulatory networks. Genetic manipu- lation of one or a few genes is unable to achieve desirable phenotype for multiple stress tolerance. Transcription dynamics and profiling studies of key gene sets such as heat shock proteins provided new insight into tolerance mechanisms. A transient gene expression response or a stress response to ethanol does not necessarily lead to ethanol-tolerant phenotype in yeast. Reprogrammed pathways and interactions of cofactor regeneration and redox balance revealed by time-course studies suggest constitutive gene expression response is important for ethanol tolerance. Fine-tuned expression of key transcription factor genes, which regulate numerous genes associated with ethanol stress, may achieve desirable phenotype and avoid side effect to cell growth at the same time.