Dynamic analysis Caffeic acid production driven by the key physicochemical factor and microbial community succession in Baijiu Daqu: A multi-microorganism fermentation of solid-state fermentation system

Daqu is a saccharifying fermenting agent in the solid-state fermentation process of Strong aromatic Baijiu, providing important raw materials, microorganisms and enzymes for the fermentation of Baijiu, however, a little information about organic acids production in Daqu until now. This work analyzed the correlation among microbial community succession, physicochemical factors and caffeic acid-producing metabolic pathways in key fermentation time-point of strong aromatic Baijiu Daqu, and the results showed that the main functional communities of caffeic acid metabolism were Staphylococcus, Klebsiella, Lactobacillus and Pichia, respectively. The correlation results showed that in the fermentation stage of the Daqu, caffeic acid was mainly influenced by miosture and reducing sugar. Co-occurrence network analysis showed that microbial interactions were stronger in days 0-8 than in days 10-27. The PICRUSt2 marker gene sequence was used to predict information on the function and abundance of enzymes related to different fermentation stages of Daqu, and combined with the related enzymes involve in caffeic acid metabolism, the results indicated that the microbial community in the pre-fermentation 0-8 days had the potential to produce caffeic acid. The results provide a theoretical basis for the analysis of the formation mechanism of phenolic acids in the multi-bacterial co-fermentation system of Daqu fermentation.