Revealing the microbial contributions in chili paste fermentation by inoculating in situ microbiome

Fermented chili paste, a widely used food and condiment, has a pleasant flavor due to the action of microorganisms that spontaneously enriched. However, the exact contribution of microorganisms to flavor compounds during chili paste fermentation is not clear yet. In this study metagenomic sequencing was employed to analyze microbial composition, functionality, and their correlation with flavor substances during fermentation. In particular, in vitro chili paste fermentation by inoculating in situ microbiome from different stages was conducted to confirm the functionality of key microorganisms. The results showe that the primary bacteria involved in chili paste fermentation include Pantoea, Lactobacillus, Lactococcus, Leuconostoc, Weissella, and Pediococcus, while the primary fungi include Zygosaccharomyces, Pichia, Saccharomyces, Starmerella, and Debaryomyces. There are high correlations between Lactobacillus, Pediococcus, Weissella, and Pichia with various organic acids and flavor compounds during the chili paste fermentation process, indicating them the key functional microorganisms. In situ validation further confirmed that Pediococcus, Lactobacillus, Weissella, Zygosaccharomyces, and Pichia are the core microorganisms behind flavor compound production. These findings provide new insights into how microorganisms influence flavor characteristics and support the discovery of essential indigenous functional microorganisms. This knowledge is valuable for the regulation of the chili paste fermentation process.