Antimicrobial Activity and Probiotic Potential of Lactic Acid Bacteria Isolated from São Jorge Cheese

Six lactic acid bacteria isolated from São Jorge PDO cheese were characterised for technological, safety, antimicrobial, and probiotic properties. All isolates fermented a broad range of carbohydrates and lacked lipolytic activity, while SJC115 and SJC119 showed proteolysis. Safety profiling (γ-haemolysis, no DNase or gelatinase activity, and generally favourable antibiotic susceptibility) is promising, but tetracycline resistance warrants caution and genomic confirmation. L. paracasei and L. brevis isolates inhibited a wide range of foodborne pathogens (Listeria monocytogenes, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, Bacillus spp.) and spoilage fungi (Penicillium and Aspergillus spp.). Notably, two isolates (SJC117 and SJC120) exhibited antibacterial activity in neutralized cell-free supernatants, indicating putative bacteriocin-like inhibitory substances (BLIS). The isolates survived intestinal conditions above the probiotic threshold, yet only SJC117 and SJC120 tolerated gastric acidity (pH 2.5, 1 h) with >5 log CFU/mL. Despite low hydrophobicity, strains showed good autoaggregation and pathogen coaggregation. All isolates produced exopolysaccharides (EPS) and angiotensin-converting enzyme (ACE) inhibitory peptides, whereas some exhibited moderate conjugated linoleic acid (CLA) production and glutamate decarboxylase (GAD) activity. L. paracasei SJC117 stood out by combining BLIS/antifungal activity, superior gastric tolerance, and an exceptional bioactive profile, making it a promising candidate for biopreservation and functional food applications that warrants further in vivo validation to confirm its efficacy and safety.