Characterization, Production, and Application of Antifungal Metabolites from Probiotic Levilactobacillus and Lactiplantibacillus Strains Isolated from Fermented Olives

In this study, the characterization, production, and application of antifungal metabolites obtained from the Levilactobacillus (L. brevis S27) and two Lactiplantibacillus (L. pentosus S42 and L. plantarum S62) strains were evaluated. The lactic acid bacteria (LAB) cells showed antifungal activity against molds. The cell-free supernatant (CFS) of Levilactobacillus and Lactiplantibacillus presented antimicrobial activity against fungi and foodborne pathogenic bacteria, and the antifungal activity was significantly (p < 0.05) higher than that of the antibacterial activity. Moreover, the antifungal metabolites were characterized as proteinaceous compounds that remained stable under both high and low temperatures and demonstrated activity across a broad pH range. Additionally, metabolite production was significantly higher (p < 0.05) at an initial pH of 5 when incubated at either 25 °C or 37 °C. All strains and their CFSs exhibited strong bio-preservative effects against Penicillium digitatum in yogurt and against Aspergillus niger on orange fruit. Consequently, these Lactobacilli strains and their antifungal metabolites represent a novel approach to biocontrol in the agri-food industry and agricultural products.