Screening of lactobacilli and Leuconostoc spp. from São Jorge PDO cheese reveals notable antimicrobial activity against foodborne pathogens and potential probiotic traits

Twenty lactic acid bacteria isolated from São Jorge PDO cheese were characterized for technological properties, safety, antimicrobial activity, and probiotic potential. Four Lacticaseibacillus paracasei isolates (SJC88, SJC99, SJC107, SJC108) and Leuconostoc mesenteroides SJC113 exhibited notable inhibitory activity against Listeria monocytogenes, Salmonella enterica, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Clostridium perfringens , and the spoilage fungi Mucor racemosus and Aspergillus caesiellus . All strains showed favourable safety profiles (no haemolysis, DNase, gelatinase, or histamine production), good tolerance to simulated gastrointestinal transit, high cell surface hydrophobicity (up to 88%), and notable gamma-aminobutyric acid production (up to 5.67 g/L). Technological traits included acidification, proteolysis, diacetyl production, and exopolysaccharide formation. These autochthonous strains represent potential adjunct or protective cultures for dairy applications, supporting food safety, functional food development, and valorisation of traditional cheese microbiota.