Immobilization of beta-xylosidase from Trichoderma reesei QM 9414 on nylonpowder

beta-xylosidase was isolated and partially purified from Trichoderma reesei QM 9414 grown on wheat straw as the sole carbon source. The enzyme was att ached covalently to nylon powder and the optimal conditions for the immobil ization procedure were determined. The optimum pH value (4.0) was conserved but the optimal temperature for catalysis (55 degrees C) decreased 5 degre es C after immobilization; the activation energy and thermal stability also decreased. Kinetics towards xylobiose and synthetic substrates in batch de monstrated that no saturation was reached using the immobilized derivative with the optimal protein retention, whereas saturation with p-nitrophenyl b eta-xylopyranoside (pNPX) was reached in a reactor loaded with a low protei n retention derivative, giving K-M = 1 mM pNPX and V-max = 0.35 mu mol/min/ mg protein. We investigated the operating conditions under which the reacto r must work to reach the highest specific activity and this corresponds to 37.6% substrate conversion. A theoretical calculus will allow us to design a reactor in order to reach higher conversions.