Keywords: Sol-gel; covalent immobilization; α-glucosidase; glucose oxidase; maltose hydrolysis

Abstract

A hybrid sol-gel nano-biosensor has been developed to determine maltose produced by starch hydrolysis in the presence of α-amylase. Glucose oxidase (GOx) and glucosidase (GD) were covalently immobilized on the sol-gel sensor via carbodiimide reaction. The kinetic study confirmed a successful immobilization of the enzymes. Immobilization conditions such as the amount of enzyme, immobilization time; and pH in working buffer were optimized. The biosensor showed the maximum response at glucose oxidase concentration of 20 U/ml and immobilization time of 90 minutes. The optimum pH of the working buffer was pH 7 at 45oC. From the Lineweaver-Burk plot, the Km value for the immobilized enzymes was 12.72 mM which was much lower than enzyme activity in solution (24.6 mM). The biosensor showed a linear response to maltose hydrolysis in the range of 0.5 - 5 mM. The sensitivity and correlation coefficient of the sensor were 29.15 μA/mM/cm2 and 0.9975, respectively.