Impact of ultrasonic irradiation pretreatment of water-soluble cellulose on enzymatic hydrolysis

Abstract

This study investigated the effects of ultrasonic irradiation on the enzymatic hydrolysis of water-soluble cellulose. Two types of cellulases (from Aspergillus niger and Trichoderma reesei) were employed for the enzymatic hydrolysis of carboxymethyl cellulose (CMC). An assay of the enzymatic hydrolysis of water-soluble cellulose was evaluated based on the production of glucose. The optimum set of operating conditions for ultrasonic irradiation involved an ultrasonic irradiation power and time of 116 W and 30 min, respectively. The initial reaction rate of enzymatic hydrolysis of CMC was increased with ultrasonic pretreatment (116 W) compared to that of the ultrasonication-free system. The kinetic parameters (Michaelis–Menten constant; Km and maximum reaction rate; Vmax) were examined to evaluate the reactivity. As a result of ultrasonic irradiation, the value of Km was decreased to 0.2 times its original value in the system employing A. niger, and to 0.6 times its original value in the system employing T. reesei. Ultrasonication increased the value of Vmax to 1.3 times its original value for both cellulases. Moreover, the viscosity of the CMC solution was decreased by ultrasonic irradiation, decreasing the activation energy of the reaction and increasing its frequency factor. Ultrasonic irradiation can therefore be employed in process design to control viscosity and achieve high-performance enzymatic hydrolysis of water-soluble cellulose. Ultrasonication is an effective application for accelerating enzymatic hydrolysis of cellulose and design lower energy industrial processes for cellulose degradation.