In this study, antibacterial substances were extracted and identified from the mycelia of Eurotium cristatum FS-1, and evaluated for antibacterial activity against Pseudomonas putida LP-3. The underlying mechanism was investigated by microscopic observations, LP-3 cell content analysis, and metabolomic analysis. The results showed that the half maximal inhibitory concentration (IC₅₀) of the ethyl acetate extract (FSEAE) from the mycelia of Eurotium cristatum FS-1 on P. putida LP-3 (1 × 10⁴ CFU/mL) was 8 mg/mL. As observed by scanning electron microscopy (SEM), FSEAE destroyed the cell membrane of P. putida LP-3. The K⁺ content in the culture supernatant of P. putida, the activity of oxidative stress enzymes in the cell metabolic pathway (superoxide dismutase, glutathione peroxidase, and catalase) and the content of malondialdehyde (MDA) were measured, showing that the antibacterial effect of FSEAE mainly in the logarithmic growth period of P. putida LP-3 (8–16 h). Non-targeted metabonomics was used to analyze FSEAE treated samples and control samples (treated by dimethyl sulfoxide), and a total of 124 metabolites were obtained, of which 30 metabolites were significantly different between the two groups. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that FSEAE affected the growth and metabolism of P. putida mainly by interfering with the tricarboxylic acid cycle. The results from this study can provide a theoretical reference for the development and utilization of Saccharomyces coronatus and its metabolites.

This study aimed to investigate microbial succession and metabolic dynamics during the traditional fermentation of Hongqu aged vinegar, and explore the core functional microbes closely related to the formation of flavor components. Microbiome analysis demonstrated that Lactobacillus, Acetobacter, Bacillus, Enterobacter, Lactococcus, Leuconostoc and Weissella were the predominant bacterial genera, while Aspergillus piperis, Aspergillus oryzae, Monascus purpureus, Candida athensensis, C. xylopsoci, Penicillium ochrosalmoneum and Simplicillium aogashimaense were the predominant fungal species. Correlation analysis revealed that Acetobacter was positively correlated with the production of tetramethylpyrazine, acetoin and acetic acid, Lactococcus showed positive correlation with the production of 2-nonanone, 2-heptanone, ethyl caprylate, ethyl caprate, 1-hexanol, 1-octanol and 1-octen-3-ol, C. xylopsoci and C. rugosa were positively associated with the production of diethyl malonate, 2,3-butanediyl diacetate, acetoin, benzaldehyde and tetramethylpyrazine. Correspondingly, non-volatile metabolites were also detected through ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. A variety of amino acids and functional dipeptides were identified during the traditional brewing of Hongqu aged vinegar. Correlation analysis revealed that Lactobacillus was significantly associated with DL-lactate, indolelactic acid, D-(+)-3-phenyllactic acid, pimelic acid, pregabalin and 3-aminobutanoic acid. This study is useful for understanding flavor formation mechanism and developing effective strategies for the suitable strains selection to improve the flavor quality of Hongqu aged vinegar.