Isolation and Identification of High Temperature Yeast in Zhanggonglaojiu Daqu and Optimization of Fermentation Conditions

In order to screen out high-temperature-tolerant yeast,this experiment used the traditional method of microbial isolation and culture to isolate 100 strains of yeast from the initial screening of medium and high temperature daqu of Zhanggonglaojiu,and then obtained a yeast that could grow at 45 ℃ through re-screening,numbered as ZG-3.Through morphological observation and combined with the analysis of 26S rDNA sequence,the ZG-3 strain was identified as Pichia kudriavzevii. The high temperature resistance,ethanol resistance and ethanol fermentation performance were tested by conventional methods. The results showed that the optimum growth temperature of ZG-3 strain was 37 ℃,the maximum growth temperature was 45 ℃,and the ethanol tolerance was up to 12%. The strain was fermented at 40 ℃ for 72 h,producing alcohol 4.7%vol. The response surface was optimized for the fermentation conditions of ZG-3 strain. Under the best fermentation conditions,the inoculation amount was 12%,the fermentation temperature was 40 ℃,the pH was 5,the glucose concentration was 140 g/L,the fermentation was 72 hours,and the alcohol content was 5.2% vol. It can be seen that ZG-3 is a high temperature and ethanol resistant yeast with great potential for application and development.