Unveiling the microbiota of sauce-flavor Daqu and its relationships with flavors and color during maturation

Abstract

This study investigated the microbial community in three-color sauce-flavor <i>Daqu</i> (black, yellow, and white) throughout their maturation processes, together with their physicochemical factors, culturable microbes, flavor components, and fermenting vitalities. Results from high-throughput sequencing revealed distinct microbial diversity, with more pronounced variations in bacterial community than in fungal community. Firmicutes and Ascomycota emerged as the most dominant bacterial and fungal phyla, respectively, during maturation. Genus-level analysis identified <i>Kroppenstedia</i>, <i>Virgibacillus</i>, and <i>Bacillus</i> as dominant bacteria in black <i>Daqu</i>, yellow <i>Daqu</i>, and white <i>Daqu</i>, severally, while <i>Thermoascus</i> was shared as the core dominant fungi for these <i>Daqu</i>. Physicochemical factors, particularly acidity, were found to exert a significant impact on microbial community. <i>Kroppenstedtia</i> was the key bacteria influencing the color formation of these <i>Daqu</i>. Furthermore, correlations between dominant microbes and flavor compounds highlighted their role in <i>Daqu</i> quality. Molds (<i>Aspergillus</i>, <i>Rhizomucor</i>, and <i>Rhizopus</i>), excepting <i>Bacillus</i>, played a crucial role in the formation of pyrazine compounds. Consequently, this study offers innovative insights into the microbial perspectives on color and pyrazine formation, establishing a groundwork for future mechanized <i>Daqu</i> production and quality control of sauce-flavor baijiu.