Effects of storage period and season on the microecological characteristics of Jiangxiangxing high-temperature Daqu

Metagenomics, non-targeted metabolomics, and metaproteomics were employed to analyze the microecological succession of high-temperature Daqu during storage, elucidate the adaptation mechanism of the microbial community of Daqu to storage environments, and clarify the microecological characteristics of Daqu during different seasons. During storage, the relative abundances of Bacillus, Oceanobacillus, Staphylococcus, and Aspergillus in Daqu had significantly increased, while those of Kroppenstedtia, Saccharopolyspora, Thermoascus, and Thermomyces had significantly decreased. During the first 3 months of storage, compound metabolism of Daqu was primarily dominated by generation of small molecular substances and then shifted to metabolism of amino sugars. During the storage process, homogeneous selection (15.57 %) and homogeneous diffusion (14.86 %) of the microbial communities of Daqu were much larger than during the fermentation process, while the variable selection assembly (29.43 %) was smaller than during the fermentation process. Among the 2509 proteins identified in the four-season Daqu, bacterial protein expression was 1.46-fold greater than that of fungi. Seasonal factors influenced the function of Daqu by alterations to Bacillus subtilis, Oceanobacillus iheyensis, and Aspergillus nidulans and other microbial functions. Carbon and benzoic acid metabolism of Daqu was relatively increased during the spring, while metabolism of alkaloids and tyrosine was upregulated during the summer, amino acid synthesis and starch metabolism were enriched during the autumn, and peptidoglycan synthesis was relatively greater during the winter. Adjusting the moisture content of Daqu during the storage period was shown to reduce microecological differentiation caused by seasonal temperature variations.