Coffee-derived lactic acid bacteria postbiotics: strain-specific antimicrobial, redox and Caco-2 immunomodulation readouts

Coffee-associated lactic acid bacteria (LAB) are a promising source of bioactive metabolites with diverse health-promoting functions, including antimicrobial and antioxidant activities. This study investigated the antimicrobial, antioxidant, nitric oxide (NO)-scavenging, hemocompatibility, cytotoxic and immunomodulatory properties of coffee-associated LAB cell-free supernatants, including Lactiplantibacillus plantarum (strains B3, B6, B9, B10), Limosilactobacillus pentosus (B17), and Weissella confusa (B19). Antimicrobial screening revealed marked strain-dependent inhibition patterns, with B6 and B10 exhibiting the strongest activity, particularly against Gram-positive bacteria. Antioxidant assays identified B3, B6, and B9 as the most active samples, while distinct metabolite profiles were observed among strains. B3 and B6 were characterized by elevated phenolic acid levels, whereas B9 contained higher flavonoid and stilbene contents. The NO-scavenging assay demonstrated stronger activity for B3 and B6 relative to the other CFS. Hemocompatibility and anti-hemolytic analyses confirmed good blood compatibility and protective effects against oxidative hemolysis, particularly for B3 and B6. Cytotoxicity assessment on Caco-2 intestinal epithelial cells indicated high biocompatibility for B3 and B6, maintaining >90% cell viability, whereas B9 and B19 induced comparatively higher cytotoxic responses. Immunomodulatory analyses further demonstrated substantial strain-dependent variability, ranging from tolerogenic to more activating cytokine profiles. The results identify Lpb. plantarum B6 as the most promising candidate for further development as a postbiotic ingredient for food and nutraceutical applications. The marked intra-species variability observed among Lpb. plantarum strains further emphasizes the importance of strain-level functional characterization.