Milk-clotting enzyme from Bacillus licheniformis 5A1 was immobilized on Amberlite IR-120 by ionic binding. Almost all the enzyme activity was retained on the support. The immobilized milk-clotting enzyme was repeatedly used to produce cheese in a batch reactor. The production of cheese was repeated 5 times with no loss of activity. The specific activity calculated on a bound-protein basis was slightly higher than that of free enzyme. The free and immobilized enzyme were highly tolerant to repeated freezing and thawing. The optimum temperature for milk-clotting activity was 70 pC with the free enzyme whereas, it was ranged from 70 to 80 pC with the immobilized milk-clotting enzyme. The activation energy (E A) of the immobilized milk-clotting enzyme was lower than the free enzyme (E A = 1.59 and 1.99 Kcal mol-p# respectively). The immobilized milk-clotting enzyme exhibited great thermal stability. The milk-clotting optimum pH was 7.0 for both free and immobilized enzyme. The Michaelis constant K m of the immobilized milk-clotting enzyme was slightly lower than the free enzyme.
展开▼
