Hydrolysis of pectin by a polygalacturonase (PG) enzyme was studied and it was found that strong product inhibition occurs. The process could be described by a competitive mechanism and the inhibition constant determined was K-1 = 3.13 g/l. A thermostated, flatsheet membrane bioreactor was applied for the reaction to avoid product inhibition and enhanced (more than 40% higher) productivity was achieved compared to the batch system. (c) 2005 Elsevier Ltd. All rights reserved.