The feasibility of using a hollow-fibre membrane reactor for the lipase-catalysed interesterification reaction of triglycerides and fatty, acids in a microaqueous n-hexane system was investigated The enzyme used in this study was surfactant-modified lipase with 1,3-positional specificity. This modified lipase catalysed predominantly tire interesterification reaction in a stirred-tank reactor as well as in a hollow-fibre membrane reactor system. The membrane reactor system was operated both batchwise and continuously. In a four-run batch experiment, biocatalyst activity loss was observed after the first run, which was probably caused by permeation of the free surfactant through the membrane. However, there was no observed activity loss in the three subsequent runs. The modified lipase retained its original activity for more than 70 h in continuous operation, and the membrane module system showed excellent resistance to the hydrophobic organic environment.