Predicting the packed-bed reactor performance with immobilized lactase

MAMMARELLA, ENRIQUE J; REGENHARDT, SILVINA A; ZORRILLA, SUSANA E; RUBIOLO, AMELIA C

Rio das Pedras, RJ, Brasil

Congreso; 4rd Mercosur Congress on Process Systems Engineering and 2nd Mercosur Congress on Chemical Engineering; 2005

Universidade Federal de Rio de Janeiro

Packed-bed reactors are frequently used for reaction systems with product inhibition. The use of these reactors in biological processes could solve environmental problems such as permeate whey elimination in dairy industries. This technological process would offer the possibility to hydrolyze the lactose present in whey permeate to obtain a more sweet mixture. Lactose hydrolysis process to form specific products useful in food application requires an appropriate catalyst and it can be economically feasible only with immobilized enzyme.  A continuous packed-bed reactor was used for lactose hydrolysis with b-galactosidase entrapped into polysaccharide gels. In this study, as in many cases for immobilized enzyme reactors, it is not possible to use a plug-flow model due to potentially disturbing effects such as mass transfer limitations, axial dispersion and bypassing, can not be eliminated. Therefore, realistic analysis of the packed-bed enzymatic reactor including some fundamental aspects of the process such as liquid-solid mass transfer, intrinsic kinetic parameters, and reactor hydrodynamics, was applied. These physical considerations determined a mathematical model for the substrate behavior in the reactor as function of operational conditions. A numerical method was applied to solve the partial differential equations of an isothermal packed-bed reactor model for enzymatic lactose hydrolysis with axial dispersion, Michaelis-Menten kinetics with competitive product inhibition, and an enzyme lost rate of the biocatalyst. The performance of immobilized enzyme reactor in the lactose hydrolysis at various operational conditions was experimentally and theoretically obtained. Lactose conversion at different time was determined to control the efficiency of the process. The obtained model predicted the experimental data with errors less than 5%.