Kinetic parameters of beta-glucosidase from almond immobilized in a continuous membrane reactor have been studied and compared with free enzyme used in a stirred tank reactor. The enzyme has been immobilized by cross-flow ultrafiltration in asymmetric capillary membranes made of polysulphone having nominal molecular weight cut-off of 30 kDa. The hydrolysis of oleuropein into aglycon and glucose has been used as a reaction system to demonstrate the efficiency of biocatalytic membrane reactors using immobilized beta-glucosidase. The membrane allowed to support the enzyme in a defined microenvironment, the microporous matrix, as well as to control substrate feeding to and product removal from the reaction environment in a single unit operation. Results showed that kinetic parameters of immobilized enzyme are the same as for the free enzyme, meaning that the enzyme immobilized within the membrane did not undergo decrease of activity while maintaining higher stability compared to the free enzyme. This confirms that the common observation of inverse relationship between activity decrease and stability increase for immobilized enzymes is not a general rule. In particular, the catalytic activity of immobilized enzyme can be optimized by the use of high throughput microstructured membrane systems. (C) 2009 Elsevier B.V. All rights reserved.