Impact of ultrasonic irradiation pretreatment of water-soluble cellulose on enzymatic hydrolysis
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Impact of ultrasonic irradiation pretreatment of water‑soluble cellulose on enzymatic hydrolysis Ryo‑ichi Nakayama1 · Momoko Murakami1 · Norikazu Namiki1 · Masanao Imai2 Received: 10 December 2019 / Accepted: 26 March 2020 © Springer Nature Switzerland AG 2020
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. Keywords Ultrasonic irradiation · Carboxymethyl cellulose · Viscosity · Enzymatic hydrolysis · Cellulase List of symbols A Frequency factor (Pa s) c CMC concentration for the measurement of viscosity (g/L) C Glucose concentration (mol/L) E Activation energy (J/mol) Km Michaelis constant (g/L) Ir Ultrasonic irradiation power (W) MWapp Apparent mean molecular weight of CMC (g/ mol) r Reaction rate (mol/L s) R Gas constant [J/(mol K)] = 8.3 [J/(mol K)] T Temperature (K)
Vi Initial reaction rate (mol/L s) Vmax Maximum reaction rate (mol/L s) Subscripts 0 Initial concentration, used in [E0] (g/L) and [S0] (g/L) for the enzymes and the CMC solution, respectively Greek symbols μ Viscosity of sample (Pa s) ⌀ Diameter of ultrasonic device (cylindrical shape) (cm)
* Ryo‑ichi Nakayama, [email protected] | 1Department of Environmental Chemistry and Chemical Engineering, School of Advanced Engineering, Kogakuin University, 2665‑1 Nakano‑machi, Hachioji, Tokyo 192‑0015, Japan. 2Course in Bioresource Utilization Sciences, Graduate School of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa Prefecture 252‑
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