Microbial composition and dynamic succession during the Daqu production process of Northern Jiang-flavored liquor in China

The microbial community structure and succession regularity of six key periods during high-temperature Daqu production were revealed using high-throughput sequencing to explore the factors affecting the flavor formation of Northern Jiang-flavored Baijiu technology. The results showed that among the six Daqu samples, the bacteria mainly included Firmicutes, Actinobacteriota, and Proteobacteria, of which Proteobacteria was the most dominant. The primary fungus was Ascomycota. At the genus level, the primary bacterial groups were Lactobacillus, Weissella, Bacillus, Delftia, Achromobacter, Saccharopolyspora, Thermoactinomyces, Scopulibacillus, Pseudomonas, and Stenotrophomonas. The main fungal groups in the Daqu were Wickerhamomyces, Saccharomycopsis, Thermoascus, and Thermomyces. During the initial stage of Daqu production, the dominant bacteria were Lactobacillus (20.07%) and Weissella (48.30%). As the fermentation temperature of the Daqu increased, Achromobacter, Stenotrophomonas, and Delftia became the dominant bacteria during the first Daqu flipping period, the second Daqu flipping period, and the dry-fire period. During these three periods, many bacteria were eliminated, decreasing the bacterial diversity, while a decline in temperature was evident during the Daqu exit period. After adapting to the high-temperature environment, the accumulation of Saccharopolyspora (22.07%), Thermoactinomyces (16.73%), Scopulibacillus (27.13%), Kroppenstedtia (9.03%), and Bacillus (6.97%) increased the bacterial diversity during the Daqu exit period. Wickerhamomyces (83.47%) represented the main dominant fungus during the initial production stage but were eliminated with increased temperature. Furthermore, a higher temperature increased the abundance of Saccharomycopsis and Thermoascus, while Thermomyces gradually accumulated in the D, E, and F samples. Thermomyces (79.90%) and Thermoascus (13.83%) became the dominant fungi during the Daqu exit period. In this study, high-throughput sequencing technology was used to reveal the microbial diversity during the high-temperature Daqu production process of Northern Jiang-flavored Baijiu. This provided a scientific basis for improving the production process of this product in the future. Therefore, understanding the formation of the flavor substances and the related microorganisms in Northern Jiang-flavored Baijiu can provide guidance for using them to manipulate the preparation process while implementing microbial control and improving the production procedures.