Study Of Microwave And Ultrasound Assisted Ionic Liquid Pretreatment Of Eucalyptus For Enhancing Enzymatic Saccharification

With the depletion of fossil source and increasing environmental issues brought by using them,it is badly in need of renewable and green energy.Owing to the large amount of storage and renewability,lignocellulosic biomass has attracted significant attention for several years.Extensive studies have focused on the transformation of lignocellulosic biomass to bio-ethanol.Pretreatment technology of lignocellulosic biomass is one of the key process which can significantly enhance the enzymatic hydrolysis efficiency.Cost-efficient and environment-friendly pretreatment technologies need to be developed due to the high cost and low efficiency of most current pretreatment technologies.In this paper,Eucalyptus samples were pretreated by microwave-assisted ionic liquid tetrabutylammonium hydroxide?[TBA][OH]?and ultrasound-assisted ionic liquid[TBA][OH],respectively.The mechanisms of how the microwave-assisted[TBA][OH]and ultrasound-assisted[TBA][OH]act on hard wood Eucalyptus and the effect of two pretreatment technologies on enzymatic hydrolysis of Eucalyptus were investigated.The objective of this paper is to develop cost-efficient and environment-friendly pretreatment strategy which can overcome the present disadvantages.The pretreatment technology of microwave-assisted[TBA][OH]was optimized.The highest reducing sugar yield of 410.67 mg/g was obtained when the Eucalyptus was radiated at the power of 375 W in[TBA][OH]with 50%content of water for 6min.The Fourier Transform Infrared Spectroscopy?FTIR?analysis and ¹³C Nuclear magnetic resonance(¹³C-NMR)analysis suggested that lignin in Eucalyptus was degraded significantly.The X-ray diffraction analysis suggested that part of crystalline area in cellulose was broken.The scanning electron microscope analysis suggest that the surface of Eucalyptus was destroyed and cellulose was exposed after pretreatment.In addition,ultrasound-assisted[TBA][OH]and ultrasound-assisted alkaline was compared systematically in terms of enzymatic saccharification.The initial enzymatic rate and reducing sugar yield were enhanced significantly after ultrasound-assisted[TBA][OH]pretreatment.The maximum initial enzymatic rate and reducing sugar yield of Eucalyptus were 79.39 mg/g/h and 426.6 mg/g,respectively.The structure and composition of pretreated Eucalyptus samples were characterized by FTIR,¹³C-NMR,XRD,SEM and chemistry composition analysis.In conclusion,microwave and ultrasound assisted inexpensive ionic liquid pretreatment technologies in this paper are expected to achieve cost-efficient and environment-friendly effect.This paper may provide new research ideas for efficient use of lignocellulosic biomass in the field of bio-refinery.