KINETIC-STUDIES ON GLUCOAMYLASE WITH MALTODEXTRIN AS SUBSTRATE

In this study, the kinetics of the hydrolysis of maltodextrin solutions by glucoamylase were investigated. In order to simulate the industrial process, a 35 wt% maltodextrin solution was adopted and the reactions were carried out at three different temperatures. In developing a kinetic model for the reaction, three basic assumptions were used. Firstly, that the irreversible hydrolysis of the maltooligosaccharides follow simplified Michaelis-Menten kinetics, based on a multichain mechanism, and reversible hydrolysis of maltose. Secondly, that D-glucose is an inhibitor of the reaction (product competitive inhibition). Thirdly, that enzyme deactivation obeys the inverted linear decay model. These assumptions were based on experimental observations. A method was then developed for the determination of the kinetic parameters for the resultant model. In terms of glucose (product) concentration, the kinetic model was found to be in total agreement with the experimental data but only with the addition of a remarkable step change in value of one of the reaction rate constants during the reaction. This change was attributed to the decrease in mean molecular weight of the maltodextrin molecules during the course of the hydrolysis.