RESUMEN
Bifidobacteria are one of the most important probiotic bacteria and their benefits have been known since many years ago. Probiotic organisms are required to be safe, viable and metabolically active within the gastrointestinal tract and to show enough resistance against bile and gastric juice. In this research, the ability of growth and survival of 42 strains, isolated from Iranian subjects, were studied in MRS3 containing 0, 0.25, 0.5, 1 and 2% of bile salts and simulated gastric juice with pH 3. The cultured strains were incubated under anaerobic condition and at 37°C for 48 h and then the survival/growth rates were examined at 3, 6, 12 and 24 hrs. The results demonstrated that some strains had significantly high tolerance against bile salts and simulated gastric juice. The strains with high tolerance are suggested as Iranian strains for future work especially in preparing Iranian starter and bifidus products