Probiotic Potential and Safety Evaluation of Lactic Acid Bacteria Isolated from Colostrum

Probiotics are live microorganisms that, when consumed in sufficient quantities, show obvious health effects on the consumer. Probiotics mainly belong to the Lactic Acid Bacteria (LAB) group, which can be isolated from traditional dairy sources. Therefore, this study aimed to isolate, identify and investigate the probiotic properties of LAB strains from Colostrum in Kermanshah Province. Tolerance of strains under simulated gastrointestinal conditions including low pH (pH 2.5 for 3 h), high bile salt (0.3% (w/v) for 4 h), and enzymatic conditions (5% pepsin (w/v) and pancreatin 0.1% (w/v) for 2-3 hours) was assessed and then their antagonistic activity was evaluated against 8 Gram-positive and Gram-negative pathogens. Hemolytic activity, adhesion capacity to the hydrophobic phase, and potential binding to intestinal epithelial cells were investigated. On the other hand, the efficiency of cholesterol removal from the culture medium and the ability of auto- and co-aggregation were investigated. Finally, the presence of virulence genes encoding ten pathogens and assessing antibiotic susceptibility to nine important and widely used antibiotics were performed. The results revealed that Lactococcus lactis A11, and L. lactis A21 are safe and showed higher tolerance to low pH and bile salt in gastrointestinal conditions, favorable anti-pathogenic activity, acceptable cell surface hydrophobicity, high cell adhesion, higher cholesterol uptake, ideal auto- and co-aggregation, and acceptable antibiotic susceptibility; so they could be considered as novel candidates of probiotics for use in the food industry.