Identification of novel genes to assign enhanced tolerance to osmotic stress in Saccharomyces cerevisiae.

Saccharomyces cerevisiae strains tolerant to osmotic stress are important for ethanol production during very high gravity (VHG) fermentation. We aimed to identify novel genes that confer enhanced tolerance to osmotic stress in S. cerevisiae. Two strains tolerant to up to 30% (w/v) glucose were isolated by screening a transposon-mediated mutant library. Two genes were identified: TIS11 and SDS23. In addition, the ability of these genes to confer osmotic stress tolerance was demonstrated by disrupting and overexpressing the open reading frame of each gene. The two transposon mutants grew faster than the control strain in YPD rich medium containing 30% (w/v) glucose and showed activation of Hog1p in response to VHG glucose. The disruption of genes identified in this study, TIS11 and SDS23, provides a basis for improved tolerance to osmotic stress under VHG fermentation condition.