Immobilization of glucose oxidase: A comparison of entrapment and covalent bonding

Glucose oxidase was immobilized onto poly(2‐hydroxyethyl methacrylate) (pHEMA) membranes by two methods: by covalent bonding through epichlorohydrin and by entrapment between pHEMA membranes. The highest immobilization efficiency was found to be 17.4% and 93.7% for the covalent bonding and entrapment, respectively. The K m values were 5.9 mmol dm −3 , 8.8 mmol dm −3 and 12.4 mmol dm −3 for free, bound and entrapped enzyme, respectively. The V max values were 0.071 mmol dm −3 min −1 , 0.067 mmol dm −3 min −1 and 0.056 mmol dm −3 min −1 for free, bound and entrapped enzyme. When the medium was saturated with oxygen, K m was not significantly altered but V max was. The optimum pH values for the free, covalently‐bound and entrapped enzyme were determined to be 5, 6, and 7, respectively. The optimum temperature was 30°C for free or covalently‐bound enzyme but 35°C for entrapped enzyme. The deactivation constant for bound enzyme was determined as 1.7 × 10 −4 min −1 and 6.9 × 10 −4 min −1 for the entrapped enzyme.