Stability Studies on Immobilized Glucose Oxidase Usingan Amperometric Biosensor – Effect of Protein Based Stabilizing Agents

A simple amperometric biosensor was used to study the stability of glucose oxidase (GOD) immobilized with different protein based stabilizing agents (PBSA) against temperature, pH and urea concentrations. Lysozyme as PBSA showed signi®cant increase in the stability of soluble as well as immobilized GOD compared to BSA and gelatin. At pH 6.0, the transition temperature (Tm) of the GOD immobilized with lysozyme was found to be 74.9 �C whereas that of GOD immobilized with gelatin and BSA were 66.1 �C and 63.8 �C, respectively. GOD immobilized with lysozyme retained more than 50% activity in 8M urea solution whereas with BSA and gelatin most of the activity was lost. More than 3-fold increase in the stability of soluble GOD was observed in presence of lysozyme in 50mM phosphate buffer, pH 6.0 and at 60 �C. A strong adverse in¯uence on stabilization of soluble GOD in presence of 0.2M NaCl indicates that ionic interaction between GOD and lysozyme may be playing a crucial role in the stabilization.

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