Isolation and characterization of Streptococcus thermophilus from traditionally prepared Misti dahi samples

Abstract

Total, 14 cocci isolate of lactic acid bacteria were isolated by pour plate by plating on milk sucrose agar media with suitable dilution for 42 °C/24-48 h. Separated colonies based on colony morphology were cultured in milk sucrose media for 42 °C/8-10 h. The purity of cultures was checked by evaluating morphology by simple staining, Gram's staining property and catalase test. Cocci isolates were further confirmed by different phenotypic tests. All the cocci isolates are negative for their growth in Modified enterococcus agar. The cultures were further checked to determine the quality of Misti dahi in skim milk with added sugar (20 and 22.5, 25 %) and shop prepared Misti dahi mix in terms of acidity, body, and texture. Characterization of Lactic acid bacteria was done based on sugar fermentation pattern. According to the sugar fermentation profile the identified organism for cocci isolate was Streptococcus thermophilus.