Effect And Mechanism Study On Enzymatic Hydrolysis Of Rice Straw By Surfactant-assisted Ionic Liquid Pretreatment

With the rapid development of world economy,we face with the challenges of the shortages of resoures and issues of environment.Cellulose material is inexhaustible renewable resoures in nature.If cellulose waste energy utilization is expected to alleviate a shortage of energy in our country.Much attention has been paid to biological energy source,owig to its advantages of its great potentiality of raw material and low cost and so on.Cellulose is surrounded with hemicellulose and lignin,forming highly compact structure in the cell walls of lignocellulosic biomass.The highly compact structure impedes the cellulosic ethanol development.Moreover,pretreatment is not only a key step for enhancing enzymatic hydrolysis,but also a crucial procedure for lignocellulosic materials to produce biofuel ethanol.The pretreatments of lignocellulosic materials are important to enhance the enzymatic saccharification.In this study,the rice straw was used as raw materials and pretreatment by surfactant-assisted ionic liquid.Effects of pretreatment temperature,time,and adding proportion of different kinds surfactants on the enzymatic hydrolysis of rice straw was investigated;This study used rice straws as raw materials to investigate the effect of combining different types of surfactants(e.g.,cationic,anionic,nonionic,biosurfactants)to ionic liquids on lignocellulosic material conversion rate and hydrolysis initial rate.Different surfactants-assisted ionic liquid pretreatment of rice straw was verified by Fourier transform infrared(FTIR)analysis,Scanning electron microscopy(SEM),X-ray diffraction(XRD)and Atomic force microscope(AFM);Under the optimum pretreatment conditions,the effect of single cellulase system,single ?-glucosidase system,and mixed cellulase/?-glucosidase system on reducing sugar were determined the optimal cellulase/?-glucosidase.Based on the optimal cellulase/?-glucosidase combination,the effect and kinetics of different types of surfactants/ionic liquid combination on the enzymatic hydrolysis of rice straw were studied.The factors of rice straw pretreatment were optimized by single factor test.As a result,the optimal condition for enzymatic hydrolysis of rice straw were 110 ? for 60 min with 1% surfactants.Compared with untreated rice straw,cellulose conversion was increased,distinctly,and it revealed that the effects of ionic liquid pretreatment in the presence of surfactants were enhanced.Physic-chemical properties study of rice straw by different surfactants(e.g.,cationic,anionic,nonionic,biosurfactants)-assisted ionic liquid pretreatment.The results showed that compared with rice straw pretreatments using a single ionic liquid,those that used ionic liquids combined with surfactants elevated the rice straw conversion rates.The effectiveness of the surfactant-ionic liquid combinations,listed in descending order,is as follows: biosurfactant-ionic liquids,nonionic surfactant-ionic liquids,anionic surfactant-ionic liquids,and cationic surfactant-ionic liquids.Infrared spectroscopic spectra(FTIR)and X-ray diffraction(XRD)analysis show that the processed rice straw crystallization index fell,the crystal size is smaller,that after the pretreatment can effectively reduce the degree of crystallinity,improve the effect of the combination of cellulose with enzyme.SEM microscope were found after processing of straw lose original rod-shaped skeleton,is greatly damaged,with cellulose enzyme increased accessibility.Under the optimal conditions,enzymatic kinetics of rice straw by surfactant-assisted ionic liquid pretreatment,these results showed that cellulase mixed with ?-glucosidase exhibited a high synergistic effect.Under the optimal system,surfactants/ionic liquid combination pretreatment,rice straw after 48 h enzymatic hydrolysis exhibited improved conversion compared with untreated rice straws(40%~85%)and treated using single ionic liquids(10%~31%).And different surfactants-assisted ionic liquid pretreatment can improve the enzyme reaction rate.Research results can provide certain theoretical guidance for practical digestion process,improve the enzyme effect.