Effects of external mass transfer and product inhibition on a simulated immobilized enzyme-catalyzed reactor for lactose hydrolysis

A mathematical model has been developed for predicting the performance and simulation of a packed bed immobilized enzyme reactor performing lactose hydrolysis, which follows Michaelis-Menten kinetics with competitive product (galactose) inhibition. The performance characteristics of a packed bed immobilized enzyme reactor have been analyzed taking into account the effects of various diffusional phenomena like axial dispersion and external mass transfer limitations. The model design equations are then solved by Galerkin's method and orthogonal collocation on finite elements. The effects of external mass transfer and axial dispersion have been studied and their effects were shown to reduce the external effectiveness factor. The effects of product inhibition have been investigated at different operating conditions correlated at different regimes using dimensionless moduli (St, y, θ, Da)¹. The product inhibition was shown to reduce the substrate conversion, and, additionally, to decrease the effectiveness factor when Da > Da_XO, however, it increases the effectiveness factor when Da < Da_XO. The effectiveness factor is found to be independent of the product inhibition at a crossover point at which Da_XO is defined. Effects of St and Pe have been investigated at different kinetic regimes and the results show that their effects have a strong dependency on the kinetic parameters θ, y (i.e., K_m/K_p), and Da_XO.