Analysis of the microbial community in Yongchuan douchi and the screening and application of core fermentation strains

Abstract

This research article focuses on the natural fermentation of Yongchuan douchi, investigating microbial community diversity, dominant microorganisms, changes of physicochemical parameters, and formation of flavor compositions. Utilizing high-throughput sequencing, cultivable method, physicochemical analysis, GC-MS and HPLC, the study comprehensively examines microbial community composition and changes during fermentation. It explores the potential relationship between dominant microbes, flavor components, and physicochemical parameters, ultimately developing co-culture starters that mimics natural fermentation conditions while enhancing flavor quality. High-throughput sequencing results were highly homogeneous with traditional culture methods, and throughout the fermentation process of Yongchuan tempeh, the core microorganisms in bacteria were Staphylococcus, Pantoea, and Pseudomonas, and the core microorganisms in fungi were Aspergillus, Wickerhamyces, Penicillium and Mucor. In addition, a pathogenic bacterium, Fusarium has been identified, which, together with the toxins it produces, can contaminate foodstuffs, leading to food safety problems and posing a great threat to human health. The total count of bacterial colonies exceeded that of fungi. Correlation analysis showed that dominant microorganisms have a great contribution to the accumulation of flavor compositions and play a major role in physicochemical parameters. Four dominant strains (CZ-1-M5, CZ-6-M2, CZ-7-M3, CZ-3-M3) were identified with suitable enzyme activity for use as co-culture starters. Co-culture starters was designed to replicate natural fermentation and was applied in the douchi fermentation process. Results demonstrated that the co-culture starters not only improved the flavor of the douchi but also maintained its safety.