Characterisation and probiotic potential of lactic acid bacteria isolated from Iranian traditional yogurts

Probiotics beneficially affect human health by improving the balance of intestinal microbiota and mucosal defence against pathogens. Many probiotic bacteria, mostly belong to the genera Lactobacillus, are used in commercial probiotic fermented milks throughout the world. The aim of this study was to investigate the probiotic potential of lactic acid bacteria (LAB) isolated from various Iranian traditional yogurts. During an 18-month study from October 2013 to May 2014, 96 samples were equally collected from traditional yogurts produced from goat, sheep and cow milk in Yazd Providence, Iran. Samples were transferred into MRS broth for enrichment and then subcultured on MRS agar. Isolates were studied for morphological and biochemical characteristics, using Gram staining and catalase test. The ability to tolerate acidic pH and resistance to bile salts were used as restrictive criteria for probiotic potential. Selected LAB were further identified using 16S rDNA sequence analysis. Of 96 yogurt samples, 47 LAB were isolated; from which 12 were candidates for probiotics. Six probiotic isolates belonged to Pediococcus acidilacticii and other six isolates to Lactobacillus plantarum, L. brevis, L. fermentum and L. kefiri. In summary, LAB strains isolated from Iranian traditional yogurts were considered as viable candidates of probiotics, based on their properties such as acid and bile tolerance.