Exploring the Successions in Microbial Community and Flavor of Daqu during Fermentation Produced by Different Pressing Patterns

Abstract

Daqu can be divided into artificially pressed daqu (A-Daqu) and mechanically pressed daqu (M-Daqu) based on pressing patterns. Here, we compared the discrepancies in physicochemical properties, volatile metabolites, and microbiota features between A-Daqu and M-Daqu during fermentation and further investigated the factors causing those differences. A-Daqu microbiota was characterized by six genera (e.g., Bacillus and Thermoactinomyces), while five genera (e.g., Bacillus and Thermomyces) dominated in M-Daqu. The flavor compounds analysis revealed that no obvious difference was observed in the type of esters between the two types of daqu, and M-Daqu was enriched with more alcohols. The factors related to differences between the two types of daqu were five genera (e.g., Hyphopichia). The functional prediction of microbial communities revealed that the functional discrepancies between the two types of daqu were mainly related to ethanol metabolism and 2,3-butanediol metabolism. This study provided a theoretical basis for understanding the heterogeneity of daqu due to the different pressing patterns.