A tubular reactor coupled with UF membrane was used to investigate the enzymatic hydrolysis of rice straw. The results showed that the high substrate concentration could be attained in the tubular reactor, and the rate of hydrolysis, as well as the yield of reducing sugar (RS), was markedly enhanced in the membrane bioreactor due to the continuous removal of inhibitory products. When the substrate concentration was 175 g/l, the production of RS was 436 mg/g (dry weight of rice straw), while the final RS concentration in the product stream still remained a high level, 27.2 g/l. (c) 2005 Elsevier Ltd. All rights reserved.