Milk clotting enzyme from bacillus stearothermophilus

ABSTRACT

A large number of thermophilic bacilli were screened for their ability to produce extracellular milk clotting enzyme as well as protease activity. A potent strain exhibited high milk clotting activity with lower protease formation was identified and characterized as Bacillus stearothermophilus NRC 41. Optimum temperature and pH for milk clotting enzyme activity was found to be 65-70 degrees and 6.1 respectively. Maximum enzyme activity was obtained when CaCl2 was added to skim milk at a concentration of 125 mg/l. Maximum yield of enzyme was obtained after 48 hr of incubation at an initial pH of 7.0. From all carbon and nitrogen sources tested, lactose and NH4NO3 respectively were found to be the most suitable for enzyme formation. On the other hand, the presence of glucose, sucrose, fructose or raffinose as well as [NH4]2SO4, [NH4]3PO4 or NH4Cl in the medium resulted in suppressing enzyme formation