This paper describes the enzymatic hydrolysis of haemoglobin in a continuous membrane bioreactor which was equipped with either a microfiltration membrane (Carbosep M14) with an average pore diameter of 0.14 mu m or an ultrafiltration membrane (Carbosep M5) with 10 kDa molecular weight cut-off. These membranes gave similar performances indicating that the virgin porosity was modified by adsorption of proteins and enzymes, and by the formation of a dynamic membrane on the mineral membranes. Practically both membranes presented identical optimum parameters corresponding to an average transmembrane pressure of 1.25 bars and a tangential velocity of 0.7 m s(-1). A simple theoretical kinetic model based on the Michaelis-Menten relation and the substrate mass balance was successfully used for the enzymatic hydrolysis of the haemoglobin in a continuous membrane bioreactor. (C) 2000 Elsevier Science S.A. All rights reserved.