Assessment of the in-vitro probiotic efficacy and safety of Pediococcus pentosaceus L1 and Streptococcus thermophilus L3 isolated from Laban, a popular fermented milk product

Probiotics are beneficial microorganisms, mostly lactic acid bacteria (LAB), that offer health benefits to the host when consumed in adequate amounts. This study assessed the probiotic efficacy and safety of LAB strains isolated from Laban, a traditional fermented milk product. Seven primarily selected Gram-positive, catalase-negative, non-spore-forming isolates were examined for their antimicrobial activity against the bacterial pathogens Bacillus cereus, Salmonella typhi, Staphylococcus aureus, and Vibrio cholera, and the fungal pathogen Candida albicans. Two isolates, identified as Pediococcus pentosaceus L1 and Streptococcus thermophilus L3, which showed antimicrobial activity against all pathogens, were further evaluated for their probiotic competence. The selected isolates demonstrated strong resistance to low pH, bile salts, and phenol, indicating their potential for gastric endurance. They also exhibited high cell surface hydrophobicity to various hydrocarbons, autoaggregation, and coaggregation properties, demonstrating strong adhesion abilities. In addition, both isolates showed strong antioxidant activity and were non-hemolytic. Although the isolates had some resistance to certain antibiotics, they were generally susceptible to commonly used antibiotics. The two LAB strains also exhibited promising technological properties, such as milk coagulation and exopolysaccharide production, indicating their potential to enhance the quality of dairy products. The results suggest that the LAB strains isolated from Laban have strong potential as probiotics, and due to their food origin, they are highly likely to exhibit maximal efficacy in food and pharmaceutical products for human consumption.