Document Type: Original Article
Associate Professor of Medical Genetics, Department of Medical Genetics, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Associate Professor of Food Biotechnology, Department of Food Biotechnology, Branch for Northwest & West region, Agricultural Biotechnology Research Institute of Iran, Agricultural Research, Education and Extension Organization (AREEO), Tabriz, Iran
Assistant Professor of Medical Bacteriology, Department of Microbiology and Virology, Faculty of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran
Ph.D. Candidate of Medical Biotechnology, Research Center for Pharmaceutical Nanotechnology, Biomedicine Institute, Tabriz University of Medical Sciences, Tabriz, Iran
Assistant Professor of Medical Biotechnology, Dietary Supplements and Probiotic Research Center, Alborz University of Medical Sciences, Karaj, Iran
Background: Traditional dairy products are the main sources for probiotic bacteria. This study aimed to isolate and characterize the potentially probiotic Lactobacillus strains isolated from traditional dairy products in Iran.
Methods: Microbial population of each dairy product was enriched and screened for acid- and bile- resistant strains. The isolates were primarily characterized by conventional phenotypic and biochemical tests. The species were finally identified using restriction analysis and 16S rDNA sequencing. In addition, the antibacterial activity of the four most common species was evaluated against seven gastrointestinal pathogens.
Results: From a total of nine yogurt and cheese samples, 17 acid-resistant Lactobacillus strains were isolated (survival>50% in PBS buffer, pH 2.5 for 3 h). Eight of them also showed high tolerance to bile. Also, the superiority of molecular techniques over phenotypic tests for effective identification of species was observed. Biochemical tests were useful in combination with 16S-amplified ribosomal DNA restriction analysis (ARDRA) technique to discriminate the isolates at species level.
Conclusion: 16S–ARDRA in combination with biochemical tests is suggested as a potentially useful method for accurate identification of Lactobacillus species where the 16S-rDNA sequencing could not discriminate between two closely related species. Considering the acid and bile resistance capacity of isolated strains, traditional dairy products may be used as important sources of probiotic strains.