An adsorption-kinetic model has been proposed to explain beta-galactosidase stability in a recirculation hollow-fibre bioreactor at different temperature. The kinetic constants of the model and its dependence on temperature have been evaluated. In addition, a study has been made of the influence of lactose and enzyme concentration on lactose hydrolysis with hollow-fibre modules made of Cuprophan and Polysulfone. The membrane surface areas assayed were between 1 and 1.95 m(2). The experimental results have been satisfactorily explained with the model proposed in a previous work. This model included the competitive inhibition of the enzyme by galactose and the enzymatic adsorption onto the membrane. The adsorption constants have been calculated, verifying the applicability of the model in the modules used. Within the experimental range analysed, the hollow-fibre module made of Polysulfone provided the least adsorption of the enzyme and therefore was the most suitable for this enzyme and reaction. (c) 2006 Elsevier Inc. All rights reserved.