Analysis of microbial community changes and their correlation with volatile flavouring substances during autonomous fer-mentation of Yi suancai in western Sichuan based on high-throughput sequencing

Yi suancai in western Sichuan nets a group of highly functional microorganisms in the alpine and high-altitude ecological environment, together with the unique salt-free fermentation process, it demonstrates the characteristics of nutritious richness and crispy taste. Six periods were estab-lished during fermentation: Day0, 0 d; Day2, 2 d; Day5, 5 d; Day8, 8 d; Day11, 11 d; Day14, 14 d. The results showed that the antioxidant capacity and organic acid content increased with the fermen-tation process, while the pH decreased gradually, indicating that the late suancai is the best edible period for the human body to supplement acid substances and eliminate free radicals. Twenty-six flavour compounds were identified, including alcohols, esters, ketones and acids, etc. Ethyl alcohol, 3-methyl-1-butanol, ethyl methanoate and acetic acid were the main contributors to the flavour, imparting floral and fruity notes to the suancai. Six dominant bacterial genera (Lactobacillus, Leuconostoc, Weissella, norank__f__norank__o_Chloroplast, Klebsiella, and unclassified_o__Lactobacillales) were identified by high-throughput sequencing in the fermentation process; nine dominant fungal genera (Dipodascaceae_gen_Incertae_sedis, Mucor, Pichia, unclassified__f__Dipodascaceaet, Cyberlindnera, Diutina, Trichosporon, Saccharomycopsis and Wickerhamomyces). Correlation analysis showed that antioxidant capacity was positively correlated with genera such as Lactobacillus, Mucor and Alter-naria, indicating that these microorganisms have an important influence in enhancing the anti-oxidant properties of suancai. Meanwhile, some genera such as norank_f_Mitochondria, Microbacte-rium, Herbaspirillum, Mortierella, and Sampaiozyma have a promoting role in the synthesis of alcohols, esters, acids, and ketones. This study revealed the interactions between microorganisms and metabolites during the fermentation of Yi suancai in western Sichuan, and provided a scientific basis for further understanding the fermentation mechanism of traditional suancai and improving the fermentation process.