Isolation of Expolysaccharide producing Streptococcus sp organism from available dahi in Chittagong, Bangladesh.

Abstract

The present study was conducted to isolate the exopolysaccharide (EPS) producing Streptococcus sp organism from the available dahi in Chittagong area and development of pure culture in laboratory. A total of 100 sample (25 of each brand) were collected from 4 different brands namely A, B, C, D (Food plaza, Banoful, Fulkoli, Genuine respectively). All the samples were subsequently cultured in nutrient agar for detecting live bacterial growth followed by MRS agar to isolate streptococcus sp and finally Ruthenium red milk plate for the isolation of exopolysaccharide producing Streptococcus sp. After that a new fermented product (yoghurt) was prepared using the isolated organism and sensory evaluation was done by a panel of judges. The study reveals 36% of the Brand C dahi were Streptococcus sp positive where 44.44% cases were exopolysaccharide (EPS ) producing while 16% cases of the Brand D dahi were Streptococcus sp positive and 20% of the positive case of the Brand B were exopolysaccharide (EPS) producing. In sensory evaluation, the newly fermented dairy product (yougurt) made by using the isolated organism was well acceptable regarding taste, appearance, acidity, flavor etc. It achieved on average 87% acceptability regarding the selected criteria. In conclusion, the isolated Streptococcus sp might be a good seed for preparing yoghurt having excellent probiotic capability.