STABILITY AND PROPERTIES OF A THERMOSTABLE β-GALACTOSIDASE IMMOBILIZED ON CHTTIN

Thermostable β‐galactosidase from an E. coli transformant containing the enzyme gene from P. woesei was immobilized at pH 4.0 and a glutaraldehyde concentration of 10 mM on chitin isolated from shrimp Crangon crangon shells. These preparations had a specific activity of 43,000 U/g of chitin at 85C using ONPG as substrate. The optimum pH and temperature for immobilized β‐galactosidase activity were 5.2 and 93C. Immobilization shifts the optimum pH for the activity of the enzyme by 0.2 units towards the acid side. The immobilized enzyme is stable at temperatures close to the optimal value, and the residual activity for ONPG hydrolysis of the preparations incubated 5 h in 0.1 M phosphate citrate buffer (pH 5.4) at 90C and 100C was 70% and 40% of the initial value, respectively.