Simultaneous catalysis and product separation by cross-linked enzyme crystals

Crystalline cross-linked xylose isomerase (CLXI, EC 5.3.1.5) and xylanase ( CLX, EC 3.2.1.8) were studied in a packed-bed reactor for simultaneous cata lytic reaction and separation of substrates from reaction products. Streptomyces rubiginosus xylose isomerase catalyzed a slow isomerization of L-arabinose to L-ribulose and an epimerization to L-ribose. In equilibrium the reaction mixture contained 52.5% arabinose, 22.5% ribulose, and 25% ri bose. In a packed-bed column filled with CLXI, a simultaneous reaction and separa tion resulted in fractions where arabinose concentration varied between 100 -0%, ribulose between 0-55%, and ribose between 0-100%. Trichoderma ressei xylanase II hydrolyzed and transferred xylotetraose mainly to xylotriose an d xylobiose. In a packed-bed column filled with CLX, xylotetraose rapidly r eacted to xylobiose and xylose by a mechanism that is not yet fully underst ood. (C) 2001 John Wiley & Sons, Inc.