ABSTRACT
b-D-Galactosidase (EC 3.2.1.23) from Lactobacillus bulgaricus (1373) was immobilized in a Polyacrylamide gel lattice in the presence of dithiothreitol, glutathione, cysteine, bovine serum albumin, casein, lactose and glucono-δ-lactone. Cysteine, bovine serum albumin, and lactose were found very effective in preserving the activity. With cysteine, bovine serum albumin and lactose, the activity yields were 61, 60 and 66% respectively, as compared to 31% without protective agents. The yield improved upto 85% when all the three protective agents, cysteine, bovine serum albumin and lactose were added during immobilization. The addition of protective agents did not have any effect on optimum pH, optimum temperature, kinetic constants and pH stability when compared with β-galactosidase immobilized without the use of protective agents; however the heat and storage stabilities were found to increase.
ABSTRACT
β-D-galactosidase (EC 3.2.1.23) from Lactobacillus bulgaricus (1373) was immobilized by entrapment in a Polyacrylamide gel lattice. The enzymatic properties of the immobilized β-galactosidase were compared with those of the native enzyme. The temperature and pH optima were not affected by the immobilization. After entrapment of the enzyme no significant change was observed in its thermostability. The pH stability of the immobilized enzyme was higher than that of the native enzyme on the acidic side. The Km values for the immobilized and native β-galactosidase with both lactose and o-nitrophenyl-β-D-galactoside as substrates were comparable. The immobilized enzyme could be repeatedly used 12 times without any loss of activity. No loss in the activity of the immobilized β-galactosidase was found after its storage for 30 days at 4°C and for 20 days at 25°C.