Microbial community and volatile metabolites related to the fermentation degree of salted fermented chili peppers

Salted fermented chili pepper (SFCP) is a fermented vegetable with unique flavors, and its flavors vary in different regions of China. However, in-depth investigations of its microbial community and their relationship to the volatile metabolites are scarce. Our work investigated the microbial community and volatile metabolites in 14 SFCP samples from nine regions around China by both culture-dependent and high-throughput sequencing methods. Five samples were dominated by Lactobacillus, Weissella, and Pediococcus, whereas nine of the samples were dominated by Pseudomonas and Enterobacter microbes. Two types of sufficient-fermentation and slight-fermentation were suggested based on the microbial community and water activity (aw). Three samples from Guizhou province were included in the sufficient-fermentation type with aw > 0.75 and culturable lactic acid bacteria, whereas the other 11 samples were intergrated into the slight-fermentation type with aw ≤ 0.75 and unculturable lactic acid bacteria. The Lactobacillaceae, comprised of unclassified Lactobacillaceae, Lactobacillus, and Pediococcus, positively correlated with the characteristic flavor formation. The sufficient-fermentation type showed enriched in valencene, 2-methyl-naphthalene, pentadecanoic acid 3-methylbutyl ester, and acetic acid hexyl ester, generating wood, floral and fruit flavors. These findings help us to select the appropriate functional bacteria for high-quality SFCP.