Microbial community of Nongxiangxing daqu during storage: microbial succession, assembly mechanisms and metabolic functions.

Background: The storage process of Nongxiangxing daqu is closely related to the quality of the daqu. The role of storage in daqu manufacture remains unclear, and most actual production relies on previous production experience.

Results: With the extension of daqu storage over a period of time, saccharifying activity, liquefying activity, fermenting activity, and esterifying activity reached a peak when stored for 3 to 4 months. Analysis of the flavor compounds showed that 87 flavor components were detected in daqu, and esters and alcohols were the main flavor compounds found. Microbial community analysis suggested that Weissella was the dominant bacterial genus with relative abundance increasing during storage, while Thermomyces was dominant fungal genus with abundance decreasing during storage. Analysis of assembly processes revealed that bacterial assembly was primarily influenced by stochastic processes during storage, whereas fungal assembly was predominantly shaped by deterministic processes. The interactions among microbiota, flavor compounds, and physicochemical parameters were elucidated, suggesting that saccharifying activity was positively correlated with Weissella, Lactobacillus, Kodamaea and Wickerhamomyces, and most of esters were positively correlated with Pediococcus and Clavispora. Microbial community functions were also predicted, highlighting enzymes involved in carbohydrate degradation, flavor formation, and ethanol fermentation. Finally, simulated baijiu fermentation was performed by adding daqu stored for different times, and the results showed that daqu stored for 3 to 4 months was appropriate for baijiu brewing.

Conclusion: The results presented in this study may enhance understanding of the impact of storage on daqu quality and, consequently, help to improve it. © 2025 Society of Chemical Industry.