A continuous process of converting D-glucose to D-fructose by glucose isomerase was chosen as a model system to illustrate the optimization of an enzymatic process subjected to deactivation. The optimization involved was selection of optimal operating temperature profile that would maximize the fructose productivity.
In order to determine the three kinetic constants (Km, Vm, and Ke) as a function of temperature kinetic studies were carried out at three different temperatures. At each temperature kinetic parameters were determined by transformation method based on the experimental data with different enzyme loadings. In determining the kinetic parameters it is found that transformation method is more convienient than other graphical or regression method for continuous reactor systems with complex enzymatic reaction kinetics.
Temperature dependence of kinetic parameters was determined from Arrehnius plot, and activation energy was calculated. Among the kinetic constants the maximum reaction rate. Vm, was most sensitive to temperature.
Inactivation studies indicate that first order deactivation model was good for the purpose of this study and that substrate protection effect is significant.
Activation energy of thermal denaturation was higher than those of all kinetic parameters. This means that the temperature sensitivity of the reaction rate is higher than that of the inactivation rate. Therfore we can predict that it is possible to optimize and improve many enzymatic processes as well as glucose isomerase system by optimal temperature policy, if and only if activation energy of the deactivation rate is greater than that of the reaction rate.
The time course of inactivation predicted by operating parameters in which temperature dependences were incorporated agreed well with that of experimental data. These have led us consequently to the simulation studies.
The optimization method used was the control vector iteration method (or modified gradient method) based o...