Study of proteolysis by Micrococcus caseolyticus isolated from refrigerated milk
Syed Nisar Ahmed, Mohammad Shakir
Psychrotrophic bacterium produces thermo resistant enzymes that induce casein degradation and is the main cause of refrigerated raw milk spoilage. In the current investigation Micrococcus caseolyticus was isolated from refrigerated milk by serial dilution method and plate count was taken. psychrotrophic count was between 70-94 ×102 CFU/ml. Among the bacterial isolates, Micrococcus caseolyticus was obtained and were further confirmed by using Bergey’s manual of Determinative bacteriology (9th edition) and 16 S rRNA sequencing. Micrococcus caseolyticus showed highest proteolytic(0.237 mg/ml) at room temperature and it goes on decreasing with increase in temperature as well as at lower temperature. In the present study, the effect of EDTA was determined which proved to be the inhibitor of the enzymes produced by Micrococcus caseolyticus. The enzyme activity in the presence of EDTA was also maximum at room temperature (0.184) but significantly less compare to without EDTA. In conclusion, the prolonged refrigeration of milk at the dairy farm or at the dairy plant degrade the quality of milk due to proteolytic activity of psychrotrophic bacteria.