The activity and stability of a cross-linked enzyme aggregate of Candida antarctica lipase B (CLEA-Calb) in supercritical carbon dioxide (SC-CO2) have been studied. The model reaction used is the esterification of isoamyl alcohol with acetic acid. The catalytic performance of CLEA-Calb is evaluated both in batch and in continuous experiments, with a focus on the effect of water production upon reaction. The results of the batch experiments show a decreasing initial activity of the CLEA-Calb with an increase in pressure. Moreover, CLEAs appear to be highly stable in supercritical carbon dioxide and also remain active during continuous reactions. Suggestions for improved process designs are given for which the optimal design depends on the specific reaction requirements. (c) 2006 Elsevier B.V. All rights reserved.