Emergence of [GAR+ ] cells in yeast from sake brewing affects the fermentation properties.

In the traditional (kimoto) method of sake (Japanese rice wine) brewing, Saccharomyces cerevisiae yeast cells are exposed to lactate, which is produced by lactic acid bacteria in the seed mash. Lactate promotes the appearance of glucose-repression-resistant [GAR⁺ ] cells. Herein, we compared the resistance to glucose repression among kimoto, industrial, and laboratory yeast strains. We observed that the frequencies of the spontaneous emergence of [GAR⁺ ] cells among the kimoto strains were higher than those among the industrial and laboratory strains. The fermentation ability of a kimoto yeast (strain U44) was lower than that of an industrial strain (K701), as [GAR⁺ ] cells generally showed slower ethanol production. The addition of lactate decreased the fermentation abilities of the K701 strain by increasing the number of [GAR⁺ ] cells, but it did not affect those of the U44 strain. These results suggest that lactate controlled fermentation by promoting the appearance of [GAR⁺ ] cells in the industrial sake strains but not in the kimoto strains.