High-performance hydrolysis of cellulose using mixed cellulase species and ultrasonication pretreatment

Abstract

Effective approaches to a practical high-performance enzymatic hydrolysis of cellulose were investigated using a ultrasonic irradiation as a pretreatment and a combination of cellulases from Trichoderma viride and Aspergillus niger. Their efficacy on enhancement of reactivity was discussed based on the kinetic parameters, i.e. Michaelis constant K m, maximum reaction rate V max and initial reaction rate, correlating with ultrasonic conditions and enzyme combination, respectively. A relatively high-weight fraction of A. niger cellulase in the mixed-enzyme system afforded rapid initiation of the hydrolysis reaction, while a kinetic analysis revealed that a T. viride cellulase weight fraction of ca. 0.3 was optimal in enhancing V max without increasing K m. Pretreatment of the cellulose fibers with ultrasonic irradiation prior to initiating the enzyme reaction further improved the reaction rate. Enhancement of V max by ultrasonication was effective in greater weight fraction of T. viride used system. The correlation between the ultrasonic irradiation time required to obtain a desired initial reaction rate and the irradiation power employed was examined, and it was found that the time needed for effective degradation could be markedly reduced by increasing the irradiation power. This finding is considered to support the possibility of applying ultrasonication pretreatment in a practical cellulose saccharification process.