Abstract: In this study, we investigated the bacterial community composition and structure during the fermentation process of traditional light-flavor baijiu using PacBio SMRT sequencing technology, and further explored the mechanism of bacterial community self-assembly during the fermentation process using a framework to quantitatively infer community assembly mechanisms by phylogenetic bin-based null model analysis (iCAMP). The results showed that the bacterial diversity decreased and then increased during the fermentation process. Lactobacillus, Acetobacter, Pediococcus and Weissella were identified as the dominant genera, and L. pontis, L. paralimentarius, L. brevis and L. acetotolerans as the dominant species. According to the differences among bacterial communities at different fermentation times, the whole fermentation process could be divided into three stages: I (0 days), II (3–10 days) and III (12–28 days). Acetobacter malorum, L. paralimentarius and L. pontis were the differential species in stages I, II and III, respectively, and there were a significant negative correlation between the differential species in different stages and a significant positive correlation between the differential species in the same fermentation stage. In addition, turnover was the major process responsible for bacterial community changes, and drift during stoichiometry was the most important process driving bacterial community self-assembly. Meanwhile, starch content, temperature and moisture content may be the main factors influencing bacterial community self-assembly during fermentation. The above results provide insight into the bacterial species composition, community succession patterns and self-assembly mechanisms during the fermentation of traditional light-flavor baijiu, which can provide a theoretical basis for regulating the microbial communities in the baijiu brewing process and further optimizing the role of multiple microorganisms in the mixed fermentation process.

Key words: light-flavor baijiu; fermented grains; PacBio SMRT; community succession; community self-assembly