Immobilization of glucose isomerase onto granular chicken bone

Glucose isomerase was immobilized onto granular chicken bone (BIOBONE) by adsorption. The amount of activity bound relative to an equal amount of free enzyme was 32 +/- 1%, with the estimated specific activity decreasing from 11.1 +/- 0.7 to 3.9 +/- 0.5 U/mg protein with immobilization. Compared with the free enzyme, immobilized glucose isomerase showed a threefold increase in the Km for fructose and a fivefold decrease in Vmax. High operating temperatures were possible (greater than 55 degrees C), but continuous use and long-term storage studies showed gradual losses of activity. Both the binding and the activity of the bone-immobilized enzyme were highly resistant to treatments with detergent, ethanol, and KCl. Studies to determine mass transfer limitation effects on immobilized glucose isomerase showed that these were insignificant for this system.