Functional Traits, Safety Assessment, and In Situ Storage Stability of Probiotic Candidate Lactic Acid Bacteria from Traditional Beyaz Cheese

This study evaluated the probiotic, technological, and safety properties of 124 lactic acid bacteria isolated from traditional Beyaz cheese, and the in situ survival of selected strains in fermented milk. Eighteen isolates showing over 80% tolerance in simulated gastric juice (pH 3.0) were subjected to further characterization. On the basis of 16S rRNA gene sequencing, most isolates belong to Lacticaseibacillus paracasei and Lactiplantibacillus plantarum, while Lactobacillus helveticus, Lentilactobacillus kefiri, and Limosilactobacillus fermentum were also identified. L. plantarum EH140 showed the greatest resistance to the simulated gastric environment (pH 2.0), whereas L. paracasei EH131 exhibited the highest bile salt tolerance. L. plantarum EH106 demonstrated strong auto-aggregation, and L. fermentum EH132 displayed notable hydrophobicity. Nine isolates exhibited bile salt hydrolase activity, but none showed γ-hemolysis, gelatinase, or DNase activity. All the isolates were susceptible to ampicillin, erythromycin, clindamycin, and chloramphenicol. Organic acid analysis revealed lactic acid as the major metabolite, followed by acetic acid. Virulence gene screening identified the efaAfs gene only in L. paracasei strains, and no biogenic amine genes were detected. The selected isolates maintained viability above 6 log CFU/mL in milk during storage. Overall, L. plantarum EH106, EH109, EH140, and EH141 were identified as the most promising candidates because of their safety and superior probiotic potential.