Insights into the roles of Ligilactobacillus, Tetragenococcus and Levilactobacillus in flavor metabolite formation during low-salt Doubanjiang fermentation: Pathways and mechanisms

To address health risks of traditional high-salt Doubanjiang , reduced-salt fermentation has been adopted, often accompanied by enrichment of specific lactic acid bacteria (LAB) including Ligilactobacillus , Tetragenococcus and Levilactobacillus . Nevertheless, their key roles and potential molecular mechanisms in flavor formation remain incompletely elucidated. This study aimed to clarify the flavor formation mechanisms driven by the three LAB strains in low-salt Doubanjiang . First, sterilized low-salt Doubanjiang (10 %, w /w) was individually inoculated with our laboratory-isolated Ligilactobacillus acidipiscis YQ11, Tetragenococcus halophilus YQ19 and Levilactobacillus brevis YQ20 for axenic fermentation. Then, physicochemical analyses showed all strains significantly reduced pH and increased total acid by 12.3 %–21.5 %. Next, metabolomic profiling revealed the inoculation raised volatile flavor compounds from 9 to 34–40 types, with 23 key differential metabolites identified (VIP ≥ 1, p  < 0.05). Each strain had distinct traits: YQ11 accumulated lactic acid (7.80 mg/g) and acetic acid (15.38 mg/g); YQ19 produced smoky 4-ethylphenol and the highest benzyl alcohol (18.06 mg/kg); YQ20 excelled in ester synthesis and specifically accumulated umami L-aspartic acid. Furthermore, whole-genome sequencing and metabolic pathway analysis of the strains were conducted. Finally, integrated genomic and metabolomic analysis uncovered core flavor-related genes, revealing potential molecular mechanisms. This study clarifies the distinct roles of enriched LABs in low-salt Doubanjiang flavor development, providing core microbial resources for rational strain selection and theoretical support for precisely modulating low-salt fermented food flavor.