Characterizing the Contribution of Strain Specificity to the Microbiota Structure and Metabolites of Muqu and Fresh High-Temperature Daqu

In this study, the differences in physicochemical properties, microbial community structure, and metabolic characteristics between various fortified <i>Muqu</i> and their corresponding high-temperature <i>Daqu</i> (HTD) were investigated using multiphase detection methods. The results demonstrated that the physicochemical properties, community structure, dominant bacterial composition, and metabolic components varied significantly among the different types of fortified HTD. The differences between HTDs became more pronounced when fortified HTD was used as <i>Muqu</i>. Compared to HTD, <i>Muqu</i> exhibited a more complex volatile profile, while HTD contained higher levels of characteristic non-volatile components. The cultivable bacteria count in <i>Muqu</i> was significantly higher than that in HTD, while the cultivable fungi count was slightly lower than that in HTD. The fungal profiles in HTD were primarily associated with starch hydrolysis and ethanol synthesis, while bacterial activity was more prominent in <i>Muqu</i>. Additionally, pyrazine synthesis was mainly attributed to fungi in <i>Muqu</i> and bacteria in HTD. Source Tracker analysis indicated that 8.11% of the bacteria and 26.76% of the fungi originated from <i>Muqu</i>. This study provides a theoretical foundation for the controlled production of HTD, contributing to improvements in its quality and consistency.