Depolymerization of xylan-derived products in an enzymatic membrane reactor

Rice husks were subjected to aqueous processing to obtain liquors containing xylan-derived products, which were assayed for composition. Liquors were dialittered using 1 kDa ceramic membrane for purification purposes, and the retentate was concentrated using the same membrane. The molecular weight distribution of xylan-derived products in concentrated liquors was assayed by gel permeation chromatography. In order to achieve the one-step conversion of soluble, high molecular weight xylan-derived products into low molecular weight arabino-xylooligosaccharides (AXOS) and the recovery of low molecular weight AXOS, concentrated liquors were treated in a continuous enzymatic membrane reactor (EMR) with a commercial endoxylanase (Shearzyme 2X). Two operational modes were studied: in the first one, both enzymatic reaction and membrane operation began at the same time, whereas in the second case, permeation started when the reaction achieved a given conversion. Both operational modes are compared in terms of productivity. (C) 2008 Elsevier B.V. All rights reserved.