Exploration of Microbial Community Diversity and Bioactive Substances during Fermentation of Mulberry Jiaosu, an Edible Naturally Fermented Mulberry Product

Mulberry Jiaosu, derived from natural fermentation using fresh mulberry fruit as a raw material, refers to an edible product containing specific bioactive substances. However, the dynamic changes in the bioactive substances of organic acids, amino acids and polyphenols as well as the species and function of microorganisms in mulberry Jiaosu are still not clear. Herein, the whole fermentation process of mulberry Jiaosu was comprehensively researched by analyzing the microbial community structure and bioactive substances. The results showed that the change in physicochemical parameters mainly happened within 30 days of fermentation. The total organic acids and total polyphenols presented upward trends. Total amino acids were partly consumed during the fermentation. A total of 173 fungal genera and 295 bacterial genera were detected in mulberry Jiaosu, mainly including Torulaspora, Zygosaccharomyces and Lactobacillus, whose abundance can be influenced by changes in the fermentation environment. During the fermentation of mulberry Jiaosu, 8 organic acids, 17 amino acids and 9 polyphenols were observed, which could be regulated by the metabolism of microorganisms. Zygosaccharomyces exhibited positive correlations with the majority of the organic acids, amino acids and polyphenols, presenting a great influence on the formation of bioactive substances. Compared with fungi, bacteria contributed more to the synthesis of organic acids, free amino acids and polyphenols. This study revealed the bioactive substances and microbial diversity during the fermentation of mulberry Jiaosu, which are findings that will contribute to the precise regulation of the fermentation process and improvement of the product quality.