Abstract: This study analyzed the effects of different proportions (1:4 and 1:5; the corresponding samples of fermented grains were designed as ZL and ZH, respectively) of raw to fermented materials on the structures and metabolite characteristics of microbial communities during the fermentation of fermented grains (Jiupei) for Nongxiangxing Baijiu. The results showed that the species richness, diversity, and evenness of the fungal community in the ZH group were significantly lower than those in the ZL group, and there were significant differences in the fungal community composition and structure between the two groups. As the proportion of raw to fermented materials increased, the succession rate of Lactobacillus as a marker bacterium during fermentation slowed down, while the succession rate of Kazachstania as a marker fungus accelerated. Thermomyces, Saccharomycopsis, and Hanseniaspora were biomarkers of the ZL group, while Kazachstania and Wallemia were biomarkers of the ZH group. Null model analysis indicated that the assembly of microbial communities in both ZL and ZH groups was mainly driven by random processes, but increasing the proportion of raw to fermented materials increased the proportion of deterministic processes. Compared with the ZL group, the contents of non-volatile and semi-volatile substances in the ZH group were significantly increased, as well as the contents of flavor substances such as caffeic acid, vanillic acid, 4-vinylphenol, phenylacetic acid, 4-hydroxybenzoic acid, ethyl stearate, and 1,2,3-butanetriol. This study provides a theoretical basis and practical guidance for improving product quality and style stability and promoting industrial standardization and intellectualization.

Key words: Jiupei; fermentation; microbial communities; metabolites; co-occurrence network