Isolation and identification of proteolytic psychrotrophic sporeforming bacteria from raw milk supplies at an experimental dairy in India

Of 51 samples of raw milk produced at the National Dairy Research Institute, 65% were found to contain proteolytic psychrotrophic sporeforming bacilli. The protease activity of 50 isolates selected ranged from 20 to 480 units/ml. Twenty/four per cent (12) of the total isolates exhibited enzyme activity in the range 51–100 units/ml, while 20% (10) had protease activity of more than 300 units/ml. Of the 50 isolates, 36% were Bacillus cereus, 20% B. polymyxa, 14% each B. laterosporus and B. circulans. 10% B. pumilus. 4% B. subtilis and 2% were identified as B. coagulans.