Breeding Of Chinese Rice Wine Yeast Saccharomyces Cerevisiae With Improved Fermentative Activity And Lower Urea Production

Chinese rice wine is a traditional brewed Chinese alcoholic beverage prevalent in eastChina. Improved fermentative activity and lower urea production Chinese rice wine yeast(Saccharomyces cerevisiae) caught a great attention and interests because of its importance inthe field of wine industrial producing rate as well as wine safety since pure yeast breedingfermentation had already applied in Chinese rice wine brewing as the science and technologyprogressed. A new two-step clotrimazole(CTZ)-resistance and L-canavanine resistance as theindicator protocol with a high screening efficiency was used to obtain fast-fermentingperformance and lower urea production Chinese rice wine yeasts through UV mutation firstlyused in this paper. Finally, the mechanism of improved fermentation rate and lower ureaproduction of mutant yeast were preliminarily studied.The main contents, results, and conclusions displayed as follows.(1) UV mutation condition on yeast XY, the results as follows. The yeast XY was in8h,200r/min shaking flask culturing to the log-growth phase under30°C, then disposed underUV (15W,25cm) for3min and then poured onto20mg/L CTZ YNB plate and10mg/LL-canavanine medium for screening drug resistance yeasts.(2) Yeast mutants obtained.16strains of yeast with stability of CTZ and L-canavanineresistance were obtained and then found out that yeast XY-3was endowed with5.21%highermax fermenting rate and7.41%lower urea production than that of yeast XY in flaskfermentation. Two-step drug resistance protocol could increase the screening efficiency asdecreasing the total yeast number to be screened.(3) Lab-scale2L Chinese rice wine brewing. The results indicated that XY-3accumulatedethanol at a faster speed than that of XY in the pre-fermentation stage. However, after4d, theethanol accumulation rate became the same with XY gradually. At6thd, XY-3accumulatedthe max ethanol concentration, however XY did this at the10thd. This led to the result thatXY-3finished fermentation4d in advance than that of XY. For the urea, XY-3had a23.43%lower production. Moreover, the amount of several main volatile flavor compounds of thewine brewed by XY and XY-3has no difference.(4) Preliminarily studying improved fermentative activity and lower urea productionmechanisms of XY-3. The results indicated that improved fermentation activity of XY-3hadlittle to do with the growth rate, brewing circumstances stress tolerance of yeast XY-3. XY-3showed pleiotropic drug resistance (PDR) which may improve the fermentation rate. And thelower urea production of XY-3may relate to a lower arginase activity than that of XY.