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

Abstract

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.