Journal of Fermentation and Bioengineering, Vol.79, No.6, 560-565, 1995
Breeding of High Glycerol-Producing Shochu Yeast (Saccharomyces-Cerevisiae) with Acquired Salt Tolerance
We have obtained a high glycerol-producing strain of shochu yeast (Saccharomyces cerevisiae) which exhibited acquired salt tolerance, and have produced barley shochu using this strain. The shochu yeast BAW-6 was sensitive to sodium chloride, and did not grow in a medium which contained more than 12% sodium chloride. We have frequently found high glycerol-producing strains among salt tolerant mutants of BAW-6. The amount of glycerol produced by a mutant TK-2, which was tolerant to 18% sodium chloride, was approximately 130% that produced by the parent strain BAW-6. Although alcohol dehydrogenase activities of the two strains were the same, glycerophosphatase activity in TK-2 was higher than that in BAW-6. The amount of glycerol produced by TK-2 was approximately 114% that produced by BAW-6 during the fermentation of barley shochu. The difference in the amount of glycerol produced between TK-2 and BAW-6 was smaller in shochu mash containing citric acid than in the medium in the absence of citric acid. These results may be due to the presence of citric acid. We investigated the behavior of the flavor components during distillation under vacuum. The distillation ratios of isoamyl acetate and beta-phenylethyl acetate of TK-2 were higher than those of BAW-6 although the alcohol distillation ratios were the same. It was considered that the glycerol level in both mashes influenced the distillation of esters.