Abstract: In this study, the probiotic properties of lactic acid bacteria (LAB) isolated from Tibetan kefir grain (TKG) were evaluated. Twenty LAB strains were screened for their tolerance to acid and simulated gastrointestinal fluid, 11 of which were tolerant to pH 3.0 and 2.5 in medium and eight of which showed viable counts of greater than 106 CFU/mL after culture in simulated gastrointestinal fluid. The results of hydrophobicity, self-aggregation, antioxidant capacity and bacteriostatic activity showed that Lactobacillus paracasei KF2-5 and Lactobacillus rhamnosus RG had high hydrophobicity and the highest bacteriostatic activity. Strain RG showed high self-aggregation and antioxidant capacity. The results of antibiotic resistance showed that KF2-5 and RG were susceptible to erythromycin, kanamycin, chloramphenicol and tetracycline, and resistant to cefotaxime and vancomycin. No hemolysis was observed in the two strains. It was concluded that both KF2-5 and RG had probiotic properties suggesting potential application in prebiotic products.

Key words: Tibetan kefir grain; lactic acid bacteria; probiotics; Lactobacillus paracasei; Lactobacillus rhamnosus