The paper presents the analysis of the model of a catalytic membrane with the enzymatic gel layer immobilized on membrane surface. The reaction proceeds in a two-liquid phase system with organic phase serves as the substrate reservoir and water phase as the products receiver. The reaction runs in gel layer where catalyst is concentrated. Influence of enzymatic gel layer parameters on the value of the substrate flux entering this layer and on the conversion degree was studied. The case when the substrate concentration in water phase is zero as well as different than zero was considered. The particular role of the value of Thiele modulus causing directly with the parameters of applied biocatalyst gel layer was shown. For the value higher than 3.5, the values of flux entering the layer reach a plateau and the conversion degree attains the values close to unity. Hence, for a given system there is a boundary value of gel thickness, which when exceeded does not cause a further process intensification and the catalyst is not using completely. (c) 2005 Elsevier B.V. All rights reserved.