Abstract: The pattern and cause of changes in microbial community structure and metabolic activities were explored during the long-term storage of Nongxiangxing Baiju Daqu. The microbial community composition on and in Daqu was determined by high-throughput sequencing technology, and changes in saccharification power and liquefaction power were analyzed. Volatile flavor substances were studied by headspace-solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS), and the formation mechanism of Daqu microbial flora and the cause of metabolite changes during storage were explored by constructing a phylogenetic null model as well as using multivariate statistical analysis. The results showed that during the storage of Nongxiangxing Baijiu Daqu, the microbial community was rebalanced, and enzyme activities and volatile compounds were further enriched and transformed. The development of microbial communities was governed by stochastic processes, and also affected by deterministic processes, in which heterogeneous selection played a major role, and niche width differences also had a certain impact on it. The changes in saccharifying power, liquefaction power and flavor substances of Daqu were closely related to the succession of microbial community. These results provide a theoretical basis for the quality control of Daqu.

Key words: Nongxiangxing Baijiu Daqu; Daqu storage period; microbial community; metabolites; microbial community succession mechanism; correlation analysis