A kinetic study on enzymatic hydrolysis of a variety of pulps for its enhancement with continuous ultrasonic irradiation

The enzymatic hydrolyses of various pulps as a type of cellulosic materials were examined in a stirred flask reactor to establish a simplified kinetic model for the complicated process. To enhance the saccharification of a pulp with cellulase, the reaction was also carried out in a stirred tank reactor with continuous ultrasonic irradiation. The kinetic model was proposed by regarding the reaction system as a pseudo-homogeneous one, in which sugars would be produced from a hypothetical soluble substrate whose initial concentration would correspond to the concentration of total sugar produced ultimately. The validity of the model developed was confirmed by its successful simulation of the time courses of the total sugar and glucose during the saccharification either with or without ultrasonic irradiation. It was found that the variation in property of pulp as well as the intensity of ultrasonic irradiation exerted an effect on the apparent rate constant and ultimate conversion of substrate, but no effect on the apparent Michaelis and competitive product inhibition constants. The saccharification of the pulp called NUKP under the ultrasonic irradiation proceeded as a two-stage reaction, suggesting an almost complete conversion of the pulp to sugar. A mechanism was proposed for such an enhancement effect of the ultrasonic irradiation on enzymatic hydrolysis of cellulose. (C) 2004 Elsevier B.V. All rights reserved.