Properties of a Milk-Clotting Microbial Enzyme

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Abstract
The clotting and proteolytic properties of a milk-clotting enzyme (microbial rennet) isolated from a culture of Bacillus cereus were investigated and compared to the corresponding properties of calf rennet. The clotting activity of microbial rennet was less sensitive to pH changes of the substrate than calf rennet. The maximum speed of clotting was obtained at 40-45 C and at 75-80 C with calf and microbial rennet, respectively. Specific viscosity measurements indicated the production by both enzymes of casein degradation products of different shape and size. Microbial rennet was more proteolytic than calf rennet and exhibited a specific proteolytic action on [kappa]-casein similar to that obtained with calf rennet. Other casein fractions were degraded continuously and nonspecifically, but [beta]-casein was the fraction most susceptible to hydrolysis.