Stochastic and deterministic processes shape microbiota and flavors of strong-flavor Daqu made from different wheat varieties during fermentation.

Abstract

Wheat serves as the primary raw material for Daqu production, and variety-specific characteristics directly influence the microbial community structure and fermentation efficacy of Daqu. Currently, there remain deficiencies in the research about the mechanisms of microbial community formation and their association with volatile taste compounds during the fermentation of various wheat varieties. This study selected the primary varieties of Jiangyou in Sichuan (Mianmai 902, Chuanmai 93, and Zhongke Mai 47) to analyze their physical and chemical properties as well as microbial composition under uniform cultivation conditions, and systematically examined the microbial succession and changes in volatile compounds during the fermentation of Daqu. The results indicated considerable disparities in the physical and chemical qualities, as well as the initial microbial communities, among various wheat varieties, which subsequently influenced the fermentation characteristics of Daqu. Sixteen biomarkers were found in various Daqu samples utilizing the random forest technique. Co-occurrence network analysis indicates that Mianmai 902 exhibits the highest degree of community-based bacterial network, while Chuanmai 93, possesses the most intricate fungal network, identifying 44 keystone species. Moreover, 23 distinct volatile flavor compounds were found. The ICAMP model demonstrated that both random and deterministic processes influenced microbial community assembly during Daqu fermentation, revealing a "binary differentiation" phenomenon in bacterial-fungal assembly (bacterial random/fungal deterministic). Distinct disparities existed in the assembly proportions among various varieties, with ecological drift prevailing in the stochastic assembly process of Daqu bacterial communities. Homogeneous propagation influences the deterministic assembly of Daqu fungus. The wheat endophytic bacteria Paenibacillus and Pseudomonas significantly influenced the formation of the Daqu bacterial c