Stability studies on immobilized glucose oxidase using an 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 significant 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 degreesC whereas that of GOD immobilized with gelatin and BSA were 66.1 degreesC and 63.8 degreesC, respectively. GOD immobilized with lysozyme retained more than 50% activity in 8 M 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 50 mM phosphate buffer, pH 6.0 and at 60 degreesC. A strong adverse influence on stabilization of soluble GOD in presence of 0.2 M NaCl indicates that ionic interaction between GOD and lysozyme may be playing a crucial role in the stabilization.