Mass transfer effects on the kinetic behavior and on the performance of immobilized glucose isomerase column reactor system

Abstract

Using the immobilized glucose isomerase, the effect of diffusional limitation on the observed kinetics of immobilized enzyme system were studied. The specific activity of this enzyme was determined as 150 units per gram of enzyme matrix, the thermal inactivation of this enzyme follows the first order decay, and the decay constant was determined as 0.00080 $hr^{-1}$, which corresponds to the half life of about 36 days at 65 ±0.5 ℃. The steady state conversion was examined as a function of the space time in the packed bed reactor. The apparent Michaelis constant, Km(app), in the differential reactor system was determined as 0.42 M, which was more than 15 times greater than the value in the batch system. And the maximum reaction rate, Vm(app), was 0.19 Mol/l-min, which is about 20 times lower than the value in the batch system. These data suggest that this immobilized glucose isomerase may be highly diffusion controlled. Therefore, the effect of superficial velocity on the apparent kinetic behavior of this enzyme was studied. The results showed that the apparent Michaelis constant of the forward reaction, i.e. Kmf(app) and Vmf(app) varied significantly with the change of superficial velocity, while the kinetic constants for the reverse reaction slightly varied only. Using these data, computer simulation was carried out and we found that the overall reaction rate of this enzyme was significantly affected by the change of superficial velocity in the packed bed reactor. Recognizing the importance of these data, several packed bed reactors were designed. These reactors have different ratio of height to diameter, H/D, but packed with the same amount of immobilized enzyme and 1.0 M of substrate solution was passed with same space time at the flow rate of 0.6 - 1.25 ml/min. The performance of these reactors, usually expressed as the productivity, were examined as a function of varying H/D ratio. As was expected from the simulation data, the productivity of this reactors ...