Abstract: This study investigated the physicochemical indicators and microbial communities in the top, middle and bottom layers of fermented grains of Jiangxiangxing Baijiu in the 2nd to 4th rounds of fermentation, and it also systematically revealed the pattern of their microecological interactions. The results showed that the fermentation process exhibited regular dynamics: moisture and acidity continued to rise, starch was continuously consumed, and alcohol content showed a parabola-like trend. These physicochemical dynamic changes revealed the core transformation process of starch consumption, ethanol production and acid accumulation driven by microbial activities. The bacterial community (with Acetilactobacillus as the core) was highly stable, while the core fungal genera underwent significant succession (from Schizosaccharomyces to Pichia), and the core yeasts were mainly distributed in the upper layer. Redundancy analysis and correlation analysis further clarified that the core environmental factors driving the community succession sequentially shifted with the rounds: water and starch contents dominated microbial colonization at the initial stage (the 2nd round). During the transition period (the third round), alcohol content became the dominant stress factor shaping the bacterial community. In the later stage (the fourth round), a stable system dominated by acidity featuring the role of fungi in alcohol synthesis was formed. By revealing the dynamic pattern of the spatiotemporal interaction between the physicochemical environment and microbial communities during the 2nd to 4th rounds of fermentation from a microecological perspective, this study provides a scientific basis for the precise regulation and quality management of the traditional brewing process.

Key words: Jiangxiangxing Baijiu; microbial community structure; physicochemical indicators; dynamic change characteristics