Effect of Bacillus velezensis on the Microbial Community Structure and Volatile Flavor Compounds of Fermented Grains (Jiupei) for Nongxiangxing Baijiu

The changes in the microbial community structure and the synthesis of volatile flavor compounds in fermented grains (Jiupei) for nongxiangxing baijiu in the presence of Bacillus velezensis was analyzed to understand the effect of microorganisms in Daqu, a traditional fermentation starter for the production of baijiu, on microorganisms in Jiupei and their metabolism. Fermentation experiments were carried out by inoculating a strain of B. velezensis isolated from medium- and high-temperature Daqu into Jiupei. Headspace solid phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to detect the volatile flavor compounds of the control and experimental Jiupei, and the microbial community structure of the control and experimental Jiupei was studied by amplicon sequencing. Partial least squares-discriminant analysis (PLS-DA) was used to explore the differential volatile flavor compounds between the control and experimental samples, and Spearman correlation analysis was used to analyze the correlation between the dominant microbial community and the differential volatile flavor compounds in Jiupei. The results showed that the abundance and uniformity of microorganisms in the experimental group did not change significantly compared with the control group, and there was no significant difference in the microbial community structure during the whole fermentation process. The contents of volatile flavor substances such as acids, esters, and alcohols in the experimental group were significantly increased compared with the control group. A total of 15 significantly differential volatile flavor compounds were identified between the control and experimental groups. The contents of caproic acid and ethyl caproate in the experimental group increased significantly. Caproic acid had a significantly positive correlation with Lactobacillus, and ethyl caproate was positively correlated with Pichia and Wickerhamomyces, but negatively correlated with Thermoascus, Bacillus and Weissella. The results of this study can help to understand the perturbation effect of Daqu microorganisms on Jiupei microorganisms and the changes of metabolites.