Fungal-bacterial interactions at species and strain-level influence γ-aminobutyric acid and ethyl esters accumulation...

How microbial interactions at the species and strain-level regulate the accumulation of γ-aminobutyric acid (GABA) and ethyl esters in fermented meat systems remains poorly understood. This study investigated how Debaryomyces hansenii interacts with lactic acid bacteria and coagulase-negative staphylococci (CNS) in a simulated sausage fermentation system to modulate these metabolites. Results showed that interactions between D. hansenii and Lactobacillus plantarum led to strain-specific differences in GABA accumulation. L. plantarum LP-2 significantly increased GABA accumulation (P < 0.001), whereas L. plantarum LP-6 showed a suppressive effect. For ethyl esters, interactions between D. hansenii and CNS strains showed distinct species-specific effects. Co-culture with Staphylococcus xylosus significantly increased ethyl esters accumulation (P < 0.05), whereas Staphylococcus equorum exhibited a suppressive effect. Mechanistic inferences based on metabolic profiling suggested that D. hansenii D1 may have promoted the growth of L. plantarum LP-2 and S. xylosus JH-3 via the release of amino acids, and potentially facilitated the conversion of key substrates (glutamate, 2-methylbutanoic acid, and 3-methylbutanoic acid), thereby contributing to the enhanced biosynthesis of GABA and ethyl esters. Based on functional complementarity at the strain level, a synthetic microbial consortium composed of L. plantarum LP-2, S. xylosus JH-3, and D. hansenii D1 exhibited synergistic advantages in the co-accumulation of GABA and ethyl esters. These findings provide a basis for targeted modulation of bioactive compounds and flavor metabolites in fermented food systems.