High-temperature Daqu of different colors from the Zibo region of China: Analysis of microbial community structure, physicochemical characteristics, and enzymatic activities.

In this study, PacBio SMRT sequencing technology was employed to analyze the microbial community structure of high-temperature Daqu (HTD) of different colors. Subsequently, the physicochemical characteristics and enzymatic activities of different types of HTD were measured, and the correlation of these factors with microbial communities was analyzed. Compared with White HTD, Black HTD had a significantly higher density, hardness, water content, water activity, etc. (P < 0.05). Sequencing analysis revealed that the key bacterial and fungal groups in Black HTD were Kroppenstedtia sanguinis and Thermoascus crustaceus, with an average relative abundance of 42.97% and 67.32%, respectively. Meanwhile, White HTD was dominated by the bacterium Weissella confusa and fungus Thermoascus aurantiacus, which had an average relative abundance of 18.23% and 35.55%, respectively. Co-occurrence network analysis showed that the microbial community structure of White HTD had higher stability. Subsequently, α- and β-diversity analyses revealed significant differences in the bacterial and fungal community structures of Black and White HTD (P < 0.05). Finally, correlation analysis demonstrated that the relationship between microorganisms and physicochemical characteristics and enzymatic activities was stronger in White HTD. These results offer a scientific basis for the standardization of HTD production.