Immobilization of β-xylosidase from Trichoderma reesei QM 9414 on nylon powder

beta-xylosidase was isolated and partially purified from Trichoderma reesei QM 9414 grown on wheat straw as the sole carbon source. The enzyme was attached covalently to nylon powder and the optimal conditions for the immobilization procedure were determined. The optimum pH value (4.0) was conserved but the optimal temperature for catalysis (55 degrees C) decreased 5 degrees C after immobilization; the activation energy and thermal stability also decreased. Kinetics towards xylobiose and synthetic substrates in batch demonstrated that no saturation was reached using the immobilized derivative with the optimal protein retention, whereas saturation with p-nitrophenyl beta-xylopyranoside (pNPX) was reached in a reactor loaded with a low protein 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 reactor 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.