Stability and properties of a thermostable beta-galactosidase immobilized on chitin

Thermostable beta-galactosidase from an E. coli transformant containing the enzyme gene fi om P, woesei was immobilized at pH 4.0 and a glutaraldehyde concentration of 10 mM on chitin isolated from shrimp Crangon crangon shel ls. These preparations had a specific activity of 43,000 U/g of chitin at 8 5C using ONPG as substrate. The optimum pH and temperature for immobilized beta-galactosidase activity were 5.2 and 93C. Immobilization shifts the opt imum 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 incubat ed 5 h in 0.1 M phosphate citrate buffer (pH 5.4) at 90C and 100C was 70% a nd 40% of the initial value, respectively.