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

A general 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, internal and external mass transfer limitations. The model design equations are then solved by the method of weighted residuals such as Galerkin's method and orthogonal collocation on finite elements. The effects of intraparticle diffusion resistances, external mass transfer and axial dispersion have been studied and their effects were shown to reduce internal effectiveness factor. The effects of product inhibition have been investigated at different operating conditions correlated at different regimes using dimensionless beta(xo) (St, theta, phi). Product inhibition was shown to reduce substrate conversion and to decrease internal effectiveness factor when beta(s) > beta(xo), however it increases internal effectiveness factor when beta(s) < beta(xo). The effectiveness factor is found to be independent of product inhibition at crossover point at which beta(xo) is defined. Effects of St and Pe have been investigated at different kinetic regimes and the results show their effects have a strong dependence on kinetic parameters thetagamma (i.e. K-m/K-p) and beta(xo). (C) 2004 Elsevier B.V. All rights reserved.