Comparison of ultrasound-assisted ionic liquid and alkaline pretreatment of Eucalyptus for enhancing enzymatic saccharification

Two ultrasound-assisted pretreatment technologies, ultrasound-assisted alkaline and ultrasound-assisted aqueous ionic liquid tetrabutylammonium hydroxide ([TBA][OH]), are compared systematically in regard to enzymatic saccharification. Pretreated Eucalyptus samples were characterized by powder X-ray diffraction, ¹³C cross polarization/magic-angle spinning solid state NMR spectroscopy, Fourier transform infrared spectroscopy, Scanning electron microscope (SEM) and chemistry composition analysis. These results not only explain the enzymatic saccharification difference between samples from the microstructure level, but also provide helpful information for relevant pretreatment research. Ultrasound-assisted [TBA][OH] pretreatment acquired a significant enhancement in the initial enzymatic rate of cellulose (79.39 mg/g/h), and a reducing sugar yield of 426.6 mg/g at 48 h. The pretreatment combining inexpensive aqueous ionic liquid and ultrasound may provide a promising strategy in the field of bio-refinery because of its unique advantages.