In this study, a simple and effective technique for characterizing Michaelis-Menten type kinetics with competitive product inhibition in packed-bed re-circulated immobilized enzyme reactors is presented, where the use of nonlinear regression techniques for multi-parameter estimation are not required. In order to demonstrate the new technique introduced in this work, enzymatic conversion of lactose in a recycling packed-bed reactor is envisaged where beta-galactosidase (lactase, EC 3.2.1.23) enzyme is immobilized on a weak base ion exchanger resin (Duolite A 568). For the experimental conditions used in this research, the total competitive inhibition by product (galactose) model is sufficient to represent the lactose hydrolysis kinetics in a packed-bed reactor. (C) 2002 Elsevier Science B.V. All rights reserved.