Microbial Interactions and Flavor Modulation in Cabbage Fermentation: Roles of Lactiplantibacillus plantarum and Rhodotorula mucilaginosa

Fermented cabbage is a globally popular food, whose distinctive flavor is largely determined by microbial metabolism and interspecies interactions. To understand the roles of Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) and Rhodotorula mucilaginosa in regulating microbial community structure and flavor formation during cabbage fermentation, natural fermented cabbage was compared with that inoculated with L. plantarum, R. mucilaginosa and both strains. The results showed that cabbage inoculated with either strain accelerated fermentation, with the fastest acidification observed in the co-inoculated group. Additionally, cabbage inoculated with R. mucilaginosa exhibited a relatively higher total amino acid content (481.50 ± 7.75 g/kg), and the levels of sweet, bitter, and umami amino acids were significantly higher than in the other groups. At the final fermentation stage, 15 differential odor-active compounds (ROAV ≥ 0.1, VIP ≥ 0.5) were identified, contributing mushroom, floral, fruity, malty, buttery, fatty, citrus, soapy, and green notes. Microbial succession analysis revealed that L. plantarum dominated bacterial community restructuring during fermentation and showed antagonistic relationships with the other lactic acid bacteria, including Lactococcus and Weissella. In contrast, R. mucilaginosa mainly influenced fungal community succession and indirectly modulated flavor formation by regulating the abundance of flavor-associated microorganisms, including Lactiplantibacillus, Lactococcus, Staphylococcus, Debaryomyces, and Candida. Correlation analysis further suggested that L. plantarum functioned as a major flavor-driving microorganism; whereas, R. mucilaginosa acted primarily as a microbial community modulator that enhanced flavor complexity through interspecies interactions. These findings highlight the importance of microbial interactions in shaping the flavor characteristics of fermented cabbage and provide insights for improving fermented vegetable flavor through targeted microbial regulation.