Daqu is a fermentation starter commonly used in the Chinese Baijiu-making process and it prominently influences the quality of Chinese Baijiu. To reveal the succession of microbial community structure and physicochemical changes of medium-high-temperature Daqu during the starter-making process, second-generation sequencing technology (Illumina NovaSeq 6000) was used to analyze the bacterial and fungal communities involved in the starter-making process of Daqu for strong-flavor Baijiu. The physical, chemical, and biochemical properties of Daqu, such as water content, reducing sugar content, and liquefaction power, were measured to analyze the relationship of microbial communities and Daqu function. The results showed that the fungi in Daqu mainly belonged to 8 phyla and 255 genera, while the bacteria were classified to 10 phyla and 262 genera. The major fungal genera were Issatchenkia (28.12% of total sequences), Thermoascus (16.16%), Trichocladium (14.14%), Rhizopus (7.15%), Aspergillus (6.44%), and Rhizomucor (5.43%); the dominant bacterial genera were Weissella (39.60%)and Lactobacillus (17.43%). Correlation analysis revealed that temperature was the primary environmental factor influencing the microbial community structure in Daqu. Rhizopus, Rhizomucor, Weissella, and Lactobacillus were identified as the major microbial taxa contributing to the function of Daqu. During the starter-making process, the liquefaction power and saccharification power of Daqu reached their maximum levels of 0.27 U and 582.00 U at 28 d, respectively;the esterification power reached a peak value of 465.54 U at 13 d; and the fermentation power reached up to 1.6 U at 7 d. This study indicated that the microbial community structure evolved dynamically in medium-high-temperature Daqu during the starter-making process, thereby altering the functional properties of the starter for Chinese Baijiu.
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