Glucose oxidase was conjugated to the biopolymer chitosan using carbodiimide conjugation. Gel beads were formed from the enzyme-biopolymer complex, and the activity of the immobilized enzyme was compared to the method of encapsulating the enzyme in chitosan. The activity of the immobilized enzyme was found to increase with increasing carbodiimide concentration and time of incubation, to a maximum. Enzyme activity decreased with time as the beads were air-dried. The pH optima of the immobilized enzyme was shifted to a more acidic value compared to that of the free enzyme. The use of carbodiimide chemistry to conjugate glucose oxidase to a chitosan gel was demonstrated. This technique holds promise for the development of immobilized enzymes for applications in medicine, biosensors, and bioprocessing. (C) 2003 Wiley Periodicals, Inc.