Isolation and Identification of Wild Strains of Lactic Acid Bacteria for Yoghurt Preparation from Indigenous Dahi

Lactic acid bacteria are commonly found in fermented dairy products. Their role in the production of value added products of milk like yoghurt, cheese and butter etc has got great significance. In this study thirty-five samples of dahi were collected randomly from the local markets of Rawalpindi. A total of 69 isolates were identified phenotypically and divide into three genera Lactococcus (36 isolates), Lactobacillus (15 isolates) and Streptococcus (18 isolates). Out of 69 isolates 26% were of S. thermophilus followed by 22% L. bulgaricus, 16% L. acidophilus, 9% L. lactis and 9% L. casei, respectively. After identification, potential of strains for lactic acid production after 6 hrs, 12 hrs and 24 hrs were also determined. In addition to acid production diacetyl production was also observed at 37oC for 8 hrs with two hours intervals. There were generally increasing trend for diacetyl production. The study showed that there was a variety of lactic acid bacteria in our environment which has potential to produce quality yoghurt.