Introduction: The increasing use of industrial dairy products instead of traditional might resulted in elimination of probiotic bacteria. The purpose of this study was isolation and biochemical identification of potentially Probiotic lactic acid bacteria isolated from traditional yogurt produced from milk of goat, cattle and sheep in Yazd province.

Methods:   96 yogurt samples ,33 each from  goats ,sheep and cow were collected from different parts of Yazd province. Samples were enriched in MRS broth, and then cultured on MRS agar.Suspected colonies were primary tested for catalase and gram stain. Lactic acid bacteria with probiotic characteristics were identified with biochemical tests including fermentation of carbohydrates, grown at 15 and 45 ° C, hydrolysis of arginine, gas production from glucose and their probiotic activity were investigated by means of resistance to acid and bile.

Results: In general out of 75 positive samples, 47 were identified as lactic acid bacteria on the bases of phenotype and biochemical tests, in which 24 were resistance to acid and out of these 12, were resistant to bile, which had a probiotics potential. Five of them were identified as Pediococcus acidilacticii, and isolated from Sheep and goat yogurt. Another 6 probiotic isolates belonged to the genus Lactobacillus and included as L. plantarum, L. brevis, L. fermentom and L. kefiri and isolated from goat and sheep yogurt Yazd province.

Conclusion: The findings of this study indicate high diversity of lactic acid bacteria in traditional yogurt in Yazd province