Hydrolysis of Lactose in a Fluidized Bed of Zeolite Pellets Supporting Adsorbed ß - Galactosidase

Abstract

The purpose of this work is to verify the possibility of using a simple physical adsorption technique to improve enzyme efficiency in performing lactose hydrolysis. Immobilization experiments of ß -galactosidase on zeolite pellets showed that this process is fairly slow and can be accomplished with contact times shorter than few hours. Comparison between homogeneous and heterogeneous hydrolysis experiments in mixed batch reactors indicates that the enzyme distribution within the zeolite pellets is concentrated in a thin shell under the pellet surface. Continuous conversion experiments were carried out on a purposely-built fluidization column. Results were fitted with a mathematical model for fluidized bed conversion without the use of any further adjustable parameter than those used in the heterogeneous batch conversion. Furthermore, no change of the parameter values was necessary. Scale-up predictions given by the model showed that fluidized columns few meters high of pellets supporting b-galactosidase are sufficient for an industrially suitable process of lactose hydrolysis. which can be performed on columns of few meters and, therefore, these are applicable to relatively small process scales as those found in traditional Italian cheese making factories.