Effect of Protectants and Fermentative Properties of Saccharomyces cerevisiae JBCC-95 Isolated from Makgeolli after Freeze Drying

Abstract

The stability of Saccharomyces cerevisiae is important for industrial usage as a starter culture for the rice wine fermentation process. This study evaluates the effects of diverse protective agents and storage conditions after freeze-drying of the high ethanol-producing S. cerevisiae JBCC-95 strain isolated from traditional rice wine. Four single cryoprotective freeze-drying agents (viz., 10% each of skim milk, lactose, trehalose, and sorbitol) were evaluated, and 10% lactose was determined to be an excellent single protectant. Moreover, the stability of S. cerevisiae JBCC-95 after freeze-drying with 5% skim milk with lactose was greatly enhanced up to 70%, which is 2.5 times higher than the single treatment of lactose. During long-term storage of 30 days at low temperatures, S. cerevisiae JBCC-95 showed less than 13% survival with single protectants, whereas 26% survival was obtained with combined protectants. Physicochemical analysis revealed that freezing of S. cerevisiae JBCC-95 with the selected protectant of 5% skim milk and lactose had no significant effect on the rice wine fermentation (P<0.05). However, the rice wine fermented by freeze-drying S. cerevisiae JBCC-95 with skim milk and lactose as protectants revealed increased levels of esters such as ethyl acetate, isoamyl acetate, and ethyl 2-methylbutyrate and decreased aldehyde contents, indicating that freeze-drying with 5% skim milk and lactose positively affected rice wine fermentation without any significant physicochemical change.