[Effects of different fermentation conditions on microbial community and chemical composition of Huafengdan Yaomu]

To investigate the effects of different fermentation conditions on the microbial community structure and chemical composition of Huafengdan Yaomu, this study compared the physicochemical properties, microbial composition, and chemical composition under fermentation with controlled temperature and humidity with those under natural fermentation. The results show the darkening of Yaomu color, significant pH changes, and decreases in the contents of total alkaloids and total flavonoids after fermentation(P<0.05). Microbial community analysis reveals that the number of bacterial amplicon sequence variants(ASVs), abundance, and diversity are significantly increased under fermentation with controlled temperature and humidity, with dominant genera including Ligilactobacillus, Levilactobacillus, and Pichia. In contrast, the natural fermentation group is dominated by Levilactobacillus, Lactiplantibacillus, and Pichia. 584 differential components are screened from 3 003 compounds by metabolomic analysis, including 40 alkaloids and 31 flavonoids. The fermentation group with controlled temperature and humidity exhibits the highest number of differential compositions, with the number of 25 alkaloids including hydropeimine and deltaline significantly increasing, 15 alkaloids including neoline significantly decreasing, 18 flavonoids including loquatoside increasing, and 13 flavonoids including kaempferol decreasing. Natural fermentation is conducive to the production of flavonoid compositions such as kaempferol and quercetin, whereas its effect on reducing toxic alkaloids is less pronounced compared to the fermentation with controlled temperature and humidity. Correlation analysis further indicates that alkaloid compositions are positively correlated with bacterial genera such as Lactiplantibacillus, while flavonoid compositions are positively correlated with fungal genera such as Wickerhamomyces. In conclusion, fermentation conditions significantly affect the chemical composition of Yaomu by regulating the microbial community structure. Fermentation with controlled temperature and humidity demonstrates greater advantages in reducing toxic components, providing a scientific basis for optimizing traditional fermentation processes and improving the quality control of TCM.