A membrane bioreactor containing a supported liquid membrane based on ionic liquids was successfully applied to the kinetic resolution of rac-1-phenylethanol catalysed by a commercial immobilized Candida antarctica lipase B (Novozym 435). Variables affecting the performance of the above bioreactor were studied. First of all, six ionic liquids were tested for use as liquid membrane phase supported in a Nylon membrane for the selective transport of the compounds involved in the reaction. The most suitable liquid membrane phase for the selective separation of the target compounds was [bmim(+)][BF4-]. The effect of the enzyme concentration in the feed compartment on the efficiency of the process was also studied, and it was found that the efficiency increased with increasing concentration of the enzyme within the experimental range assayed. Finally, when the effect of different vinyl esters as acyl-donors was analyzed it was concluded that the efficiency of the overall process was enhanced with increasing alkyl chain length of the vinyl ester. (C) 2007 Elsevier B.V. All rights reserved.