Abstract: In this study, high-throughput sequencing and headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS) were employed to investigate the succession of microbial communities and the composition of volatile flavor compounds in the fermented grains from the fifth round of stacking fermentation of jiangxiangxing baijiu produced in a distillery in Luzhou, respectively. Furthermore, the correlations between microbial communities and volatile flavor compounds were analyzed. A total of 49 volatile flavor compounds were detected in the fermented grains, including 12 alcohols, 8 aldehydes, 3 organic acids, 19 esters, 2 pyrazines, 2 furans, 2 phenols, and 1 other compound. Alcohols and esters were found to be enriched at the early stage and decreased at the late stage; aldehydes and acids exhibited overall fluctuating trends, while pyrazines were continuously accumulated. In terms of microbial composition, 257 bacterial genera and 80 fungal genera were identified, with Virgibacillus, Kroppenstedtia, Bacillus, Byssochlamys, Thermoascus, and Thermomyces being the dominant ones. Byssochlamys, Thermomyces, Thermoascus, and Bacillus were identified as the key functional microbiota during stacking fermentation by Mantel test and Pearson correlation analysis. Null-model-based individual-based community assembly modeling (iCAMP) analysis of the assembly mechanisms of these key functional genera indicated that their community assembly was driven by both deterministic and stochastic processes. Specifically, the assembly of Bacillus involved multiple pathways including ecological drift, homogenizing dispersal, variable selection, homogeneous selection, and dispersal limitation, whereas Byssochlamys, Thermomyces, and Thermoascus were primarily assembled via homogeneous selection and ecological drift. This study provides scientific evidence for elucidating the mechanisms of stacking fermentation in jiangxiangxing baijiu production.

Key words: jiangxiangxing baijiu; microbial community; flavor compounds; correlation; key functional microbiota