Lipase from Candida rugosa was immobilized on Cuprophane membrane in a hollow-fibre module for possible application for oil hydrolysis. A simple immobilization technique was applied and 154.8 mg m(-2) lipase was immobilized with approximately 40% mass yield. The reactor operating regime was investigated with respect to flow patterns in reactor zones, lipase desorption and hydrolysis rates. Flow pattern studies in the experimental system revealed nearly plug flow with a stagnant region in the reactor lumen and significant flow channeling in the shell zone. Mass transfer limitations were apparent in the lumen zone at flow rates below 15 cm(3) min(-1). Higher flow rates up to 50 cm(3) min(-1) in the lumen zone and in the range 2.5-26 cm(3) min(-1) in the shell side had no apparent influence on hydrolysis rates. At the enzyme load employed in this study, loss of enzyme activity due to desorption had little effect on reactor stability and oil hydrolysis. (C) 2003 Elsevier Ltd. All rights reserved.