Regional fingerprint, enrichment and flavor contribution of Bacillus community in Daqu for Chinese Baijiu

Bacillus is an important multifunctional genus, but the enrichment and flavor contribution mechanism of this bioresource in Baijiu Daqu are still unclear. In this study, multi-omics was used to investigate the Bacillus community from the perspectives of genus, species and genes. Under the influence of fermentation process and interspecific interactions, Daqu samples from different areas will form regional Bacillus “fingerprints”. The succession process and enrichment efficiency of Bacillus in high-temperature Daqu were mainly regulated by moisture. In the high-temperature fermentation environment, Bacillus community mainly contributed to baked aroma (pyrazines), creamy aroma (acetoin) and sauce aroma (guaiacol), but each Bacillus species metabolized different biomarkers and formed different sensory characteristics. The flavor contribution of Bacillus was influenced by both internal genes and external environment: Some strains have a deletion of the acoA/B gene, which reduces their ability to synthesize 2,3-butanediol; Bacillus subtilis had relatively lower GC content of the alsD (43.4 %), padC (39.3 %) and tdh (45.8 %) genes than other species, resulting in weaker stability under high-temperature environmental stress. This study offers novel insights into the distribution pattern and flavor contribution characteristics of different Bacillus species, while establishing a critical reference for the refined utilization of Bacillus bioresource. • Diverse Bacillus “fingerprints” exist in different types/regions of Baijiu Daqu . • “Moisture regulation hypothesis” explains conditions for Bacillus enrichment. • Different Bacillus species showed different volatile metabolic characteristics. • Distribution of flavor genes affects flavor metabolism in each Bacillus species.