ENHANCEMENT OF GLYCEROL PRODUCTION BY BREWING YEAST (SACCHAROMYCES-CEREVISIAE) WITH HEAT-SHOCK TREATMENT

The glycerol 3-phosphate dehydrogenase (GPDH; EC 1.1.1.8) activity of cells subjected to heat shock treatment increased 1.15- to 1.25-fold o ver that of cells not heat shocked. The increased GPDH activity induce d by heat shock treatment extended over several generations, but gradu ally decreased through subcultures, The effect of heat shock treatment during the pre culture stage on glycerol production in the main cultu re was investigated with the shochu yeast BAW-6 (Saccharomyces cerevis iae). Heat shock at 45 and 50 degrees C was effective for glycerol pro duction, but there was no influence at 35 degrees C. The timing of the heat shock treatment did not influence glycerol production. Enhanceme nt of glycerol production induced by heat shock was also observed in t he sake yeast K-7, wine yeast W-3, beer yeast IFO1167, and whisky yeas t IFO2363. Shochu was produced by using heat shocked BAW-6. The glycer ol concentration in the mash was increased by heat shock treatment, th ereby improving the aroma and taste of shochu produced from this mash. In addition to shochu, glycerol is a key factor influencing the taste of other brewed brewages such as sake or wine. The results suggest th at the heat shock treatment during pre culture may be an effective and simple method for improving the quality of shochu, sake, and wine.