One hundred and forty lactic acid bacteria were isolated from seven popular dahi products collected from Dhaka, Mymensingh, Tangail, Comilla Barisal and Bogra. The organisms were identified on the basis of their morphological, cultural and biochemical characteristics. The organisms were treated with different physical and chemical agents to determine their tolerance. One hundred per cent species of Lactobacillus and Streptococcus were found to grow at 37oC and at pH 4.5 to 5.5 and 7.5, respectively. Seventy isolates of Streptococcus and Lactobacillus were identified as Streptococcus thermophilus, S. lactis, S. cremoris, S. faecalis, and Lactobacillus bulgaricus, L. helveticus, L. acidophilus and L. plantarum, respectively. Of these S.thermophilus and L. bulgaricus were frequently found in all dahi samples. The latter organisms also exhibited longer viability than the other species.
