Abstract
The kinetics of oxidation of D-glucose in the presence of glucose oxidase and catalase was studied in a stirred-tank reactor. Experiments were performed using free or immobilized enzyme in 0.1 M acetate buffer solution (pH=5.5) at atmospheric pressure and 25°C. The immobilized enzyme catalyst, which consisted of both glucose oxidase and catalase supported on activated carbon, was prepared by the carbodiimide method. The initial rate of reaction was determined from the amount of oxygen consumed in the absence of external mass transfer resistances. Using free enzyme, the existence of competitive product inhibition by δ-D-gluconolactone was confirmed from Lineweaver-Burk plots, and our results could be well explained by the single substrate mechanism. The effect of mutarotation on the rate of reaction was also taken into account. The activity of immobilized enzyme catalyst was reduced to about 30% of that of the free enzyme. However, the Michaelis and product inhibition constants were not appreciably changed by immobilization. The time-course data were well explained by the proposed kinetic model.
