Metabolomics and metatranscriptomics reveal the influence mechanism of endogenous microbe (Staphylococcus succinus) inoculation on the flavor of fermented chili pepper

This study integrated metabolomic and metatranscriptomic techniques to examine how the endogenous microbe, Staphylococcus succinus, influenced the essential flavor of fermented chili peppers. The mechanisms governing spontaneous fermentation and S. succinus-inoculated fermentation were also elucidated. Esters (e.g., ethyl undecanoate, isoamyl acetate, and methyl salicylate), terpenes (e.g., terpinen-4-ol), and alcohols (e.g., α-terpineol, linalool, and 4-methyl-3-heptanol) were found to be the key aroma-active compounds, aspartic acid (Asp) and glutamic acid (Glu) were identified as primary flavoring free amino acids. Notably, during the early stages of S. succinus-inoculated fermentation, the production of these essential metabolites was abundant, while their gradual increase over time was observed in the case of spontaneous fermentation. Metatranscriptomic analysis revealed that S. succinus inoculation could up-regulate genes related to glycolysis, amino acid metabolism, and aroma compound synthesis. These changes sequentially boosted the production of sweet and umami free amino acids, enhanced organic acid levels, increased unique aroma compound generation, and further improved the flavor and quality of the fermented chili peppers. Therefore, S. succinus inoculation can augment the sensory quality of fermented chili peppers, making this strain a promising candidate for Sichuan pickle fermentation starters.