Kinetic model of the hydrolysis of polypeptides catalyzed by Alcalase® immobilized on 10% glyoxyl-agarose

The sequential hydrolysis of cheese whey proteins can improve physical, chemical and organoleptic properties of this dairy by-product, increasing its applications in the food and pharmaceutical industry. The hydrolysis of polypeptides (50 °C, pH 9.5), catalyzed by Alcalase® immobilized on 10% agarose (weight basis), activated with linear aliphatic aldehyde groups (glyoxyl-agarose), is studied here. The reaction substrate (polypeptides) is the product of a previous, sequential hydrolyses of cheese whey proteins by trypsin, chymotrypsin and carboxypeptidase A. A Michaelis-Menten model with product inhibition was fitted to the experimental data after long-term batch assays. Kinetic parameters k, KM and KI were correlated with respect to the degree of hydrolysis of the substrate in the upstream proteolyses, thus providing a general, semi-empirical rate equation. With this approach, the kinetic model may be included in process optimization algorithms, which may span different regions of operation for the proteolytic reactors. Parameters k, KM and KI ranged from 0.005 to 0.029 mmol/min/UBAEE, from 4.0 to 13.7 mM, and from 0.19 to 1.56 mM, respectively, when the previous degree of proteolysis (pre-hydrolysis) changed from 20 to 2%.