Development of Saccharomyces cerevisiae Producing Higher Levels of Sulfur Dioxide and Glutathione to Improve Beer Flavor Stability

Sulfur compounds, such as sulfite (SO 2 ), hydrogen sulfide (H 2 S), and glutathione (GSH), play different roles in beer flavor stability. SO 2 and GSH have antiaging effects which are helpful to improve the flavor stability of beer, whereas H 2 S is undesirable to beer flavor because of its unpleasant aroma. Here, we report the development of Saccharomyces cerevisiae which produces higher levels of SO 2 and GSH but lower level of H 2 S to improve beer flavor stability by nongenetic engineering approaches. After two rounds of UV mutagenesis coupled with specific plate screening methods, one promising mutant named MV16 was obtained. Compared with the original strain, the SO 2 and GSH production of MV16 in fermenting liquor increased by 31% and 30.2%, respectively, while H 2 S content decreased by 74.9%, and the DPPH radical clearance and the resistance staling value of beer fermented by MV16 increased by 24.6% and 33.0%, respectively. The antioxidizability of the mutant was improved significantly. The strategy adopted in our study could be used to obtain S. cerevisiae of improved antiaging properties, and the mutant would be safe for public use.