Engineering the robustness of Saccharomyces cerevisiae by introducing bifunctional glutathione synthase gene

Robust, high-yielding Saccharomyces cerevisiae is highly desirable for cost-effective cellulosic ethanol production. In this study, the bifunctional glutathione (GSH) synthetase genes GCSGS at high copy number was integrated into ribosomal DNA of S. cerevisiae by Cre-LoxP system. Threefold higher GSH contents (54.9 μmol/g dry weight) accumulated in the engineered strain BY-G compared to the reference strain. Tolerance of BY-G to H2O2 (3 mM), temperature (40 °C), furfural (10 mM), hydroxymethylfurfural (HMF, 10 mM) and 0.5 mM Cd(2+) increased compared to reference strain. Twofold higher ethanol concentration was obtained by BY-G in simultaneous saccharification and fermentation of corn stover compared to the reference strain. The results showed that intracellular GSH content of S. cerevisiae has an influence on robustness. The strategy is used to engineer S. cerevisiae strains adaptive to a combination of tolerance to inhibitors and raised temperature that may occur in high solid simultaneous saccharification and fermentation of lignocellulosic feedstocks.