Laboratory-scale fermentation and multidimensional screening of lactic acid bacteria from Daqu

Lactic acid bacteria (LAB) are abundant in Daqu, a Chinese traditional fermentation starter primarily for the production of Baijiu. The fermentation characteristics of LAB and their contribution to flavor compounds in alcoholic fermentation were studied using a multidimensional screening procedure to select the LAB and apply them to alcoholic fermentation. The LAB strains isolated from Daqu were characterized for tolerance to pH 3 and 12% ethanol, the yield of amylase and esterase, and the capacity to utilize sugar in sorghum media. After multivariate statistical analysis, strains were selected for alcoholic fermentation on a laboratory-scale to confirm their roles in the production of flavor compounds using HS-SPME-GCMS. A total of 59 LAB strains were isolated from Daqu. Eleven LAB species belonging to 4 genera were identified: Lactobacillus, Pediococcus, Weissella and Enterococcus. Among them, L. plantarum E2 and E11, W. paramesenteroides E27, and P. pentosaceus E48 were selected and inoculated for alcoholic fermentations. Ethyl acetate, ethyl lactate, tetramethyl-pyrazine and 4-ethyl-2-methoxy-phenol increased significantly after fermentation with E2, E11 and E48. This study showed that a systematic screening process for indigenous LAB strains could be applied to Baijiu fermentation for flavor enhancement and quality control as well as construction of a Daqu synthetic microbial community.