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The conditions for immobilization of the partially purified β-galactosidase form Bacillus subtilis HP-4 and the properties of the immobilized enzyme have been investigated. The crude enzyme precipitated with cold acetone was purified about 68-fold through DEAF-cellulose and sephadex G-100 chromatography and its recovery was 19.9%. The optimal conditions for immobilization of enzyme were obtained in 2%(w/v) sodium alginate, 15%(v/v) enzyme solution and 2%(w/v) calcium chloride, and also the optimal stirring thme was 2 hours on the above conditions. The optimum temperature and pH values for immobilized enzyme were 55℃ and 6.5, respectively. Its residual activity was show 25% after heat treatment for an hour at 65℃, and found its high stability in pH 6.0 to 8.0. The enzyme activity was not affected by EDTA, 2-mercaptoethanol, KCN, protective agents, and other methal ions except Hg ion and Cu ion. The K_m and V_(max), values of the immobilized enzyme on ONPG were 1.82 X 10^(-2)M and 3.57X10^(-8)mole/min, whereas those on lactose were 2.94X10²M and 1.68X10^7 mole/min, respectively. The remained enzyme activity for the immobilized enzyme was 95% of original activity after storage of 40 days at 4℃, and when reused for 5 times was 81%. When skim milk(4.8% lactose) and 5% lactose solution were reacted with the immobilized enzyme(250 units/g) of lactose were 51% and 43%, respectively.
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