Unraveling the microbial community and succession during zha-chili fermentation and their relationships with flavor formation.

Zha-chili is a popular traditional fermented food among people in central and southwest China for its nice flavor. It is produced from grain and fresh chili undergoing spontaneously anaerobic fermentation. In this study, the high-throughput sequencing (HTS), high-performance liquid chromatography (HPLC), and head-space solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC-MS) were applied to systematically study the dynamic of microbial community and flavor substances during zha-chili fermentation. Simultaneously, the physicochemical factors were investigated to decode the core factors affecting the microbial succession. Results showed that Lactobacillus and Kazachstania were the most dominant bacterium and fungus, respectively, and lactic acid bacteria (LAB), acetic acid bacteria (AAB), and yeasts dominated the whole fermentation. Besides, acidity, ethanol, and temperature were the core factors that shifted the microbial succession. Herein, the acidity and ethanol drove the bacterial succession from Weissella to Lactobacillus, then temperature affected the succession that Lactobacillus was partially replaced by Acetobacter. Meanwhile, acidity and ethanol actuated the fungal succession that Gibberella was superseded by Kazachstania. Moreover, Lactobacillus, Acetobacter, Kazachstania, Wickerhamomyces, Kluyveromyces, and Cyberlindnera were the core microbes associated with the formation of flavor substances including lactic acid, acetic acid, ethanol, ethyl lactate, ethyl acetate, and umami free amino acids. These findings will be helpful to unravel the formation of flavor substances based on microbial community and succession during zha-chili fermentation, providing a solid foundation for the process optimization and quality control of zha-chili.