Characteristics of unbuffered gel-immobilized urease particles. II. Overall rate of reaction

The overall rates of reaction of unbuffered gel-immobilized urease particles have been investigated with the aid of a packed-bed differential recycle reactor. Both substrate and enzyme concentrations have received attention. Cylindrical gel particles contained within impermeable tubelets were used to provide the physical strength necessary for the packed-bed arrangement and a one dimensional diffusion path to aid understanding of the complex interactions between substrate and product diffusion, and their effect on the reactions taking place. The experimental data have been interpreted with the aid of an enzyme rate equation (ERE) which relates the free solution characteristics of the enzyme to the conditions within a diffusion limited particle. The internal hydrogen ion profiles have been accommodated by a lumped parameter, the apparent pH (pH_app). Two methods have been suggested for the calculation of pH_app and the loss of activity on particle preparation, these methods are based on the use of the ERE in conjunction with experimental data.