关键词: 白酒；酒醅；宏转录组；活性微生物；群落结构和功能

Abstract: In this study, metatranscriptomics was used to analyze the diversity, succession and differentially transcribed genes of the active microbial community in fermented grains during the main fermentation period of Chinese strong-flavor baijiu (at days 3, 7 and 25). The results showed that the active microbial community was composed of 6 kingdoms, 124 phyla, 195 classes, 2 824 genera, and some unknown or unidentifiable species. The identifiable organisms were mainly composed of bacteria and fungi. As fermentation proceeded, the relative content of fungi decreased from 42.8% to 0.01%, and the content of bacteria increased from 17.7% to 56.3%. Firmicutes and Ascomycota were the major phyla that drove changes in the composition of bacterial and fungal communities, respectively. The numbers of differentially expressed genes among three fermentation times were 6 895 (3 d vs 7 d), 2 640 (7 d vs 25 d) and 6 124 (3 d vs 25 d), respectively. During the fermentation process, the number of down-regulated differential genes was significantly greater than that of up-regulated differential genes. From days 3 to 7 of fermentation, the up-regulated differential genes were significantly enriched in the metabolism of sugars and alcohols. During the whole major fermentation period, the down-regulated differential genes were mainly enriched in cell parts or related biological processes. The results of this study will provide basic data and theoretical support for in-depth understanding of the solid-state brewing mechanism of Chinese strong-flavor baijiu.

Key words: baijiu; fermented grains; metatranscriptomics; active microbial community; community structure and function