Study On Enzymatic Hydrolysis Mechanism Of P-toluenesulfonic Acid Pretreated Bagasse And Preparation Of Cellulose Nanofibrils Using It As Raw Material

Lignocellulose can not only obtain clean ethanol through biological refining,but also produce high-performance nano-cellulose,which was significant mean for the sustainable development of the environment.In order to realize the high-value utilization of lignocellulose,this study uses bagasse as a substrate and uses a new pretreatment method in recent years-p-toluenesulfonic acid pretreatment method(p-Ts OH)to destroy the natural anti-degradation barrier of lignocellulose.The enzymatic hydrolysis efficiency of p-Ts OH pretreated bagasse and the properties of the prepared cellulose nanofibrils were discussed.This study can provide some theoretical basis for the high value utilization of lignocellulose.The main research contents and results of this study are as follows:1.The chemical composition and enzymatic hydrolysis efficiency of bagasse before and after p-Ts OH pretreatment were compared.It was found that p-Ts OH could effectively remove lignin,retain cellulose,increase cellulose content and improve enzymatic hydrolysis efficiency,but the enzymatic hydrolysis efficiency of bagasse pretreated by p-Ts OH was still low.In order to analyze the reason why the enzymatic hydrolysis efficiency of bagasse pretreated by p-Ts OH was improved but still low,the differences of the surface morphology,specific surface area,total pore volume and crystallinity of bagasse before and after p-Ts OH pretreated were compared by scanning electron microscope(SEM),specific surface and pore size analysis(BET),and X-ray diffraction(XRD).The results showed that p-Ts OH could effectively remove the amorphous area of bagasse surface,make the bagasse surface smooth and dense,reduce the original pore structure,reduce the specific surface area and total pore volume,and increase the substrate crystallinity.The higher crystallinity was the reason for the lower enzymatic hydrolysis efficiency.In order to further analyze the reasons for the improvement of the enzymatic hydrolysis efficiency of bagasse after p-Ts OH pretreatment,the experiments of adsorption and desorption were carried out at the temperature conducive to enzymatic hydrolysis(50℃)and adsorption(4℃).The results showed that p-Ts OH pretreatment bagasse could absorb more cellulase,and more cellulase and p-Ts OH pretreatment bagasse were combined with a strong force.2.In order to study the effect of cellulose crystal form on enzymatic hydrolysis efficiency,the chemical composition and enzymatic hydrolysis efficiency before(S-P)and after(S-P-N)treatment of p-Ts OH bagasse with sodium hydroxide were compared.It was found that sodium hydroxide can effectively remove hemicellulose and improve the enzymatic hydrolysis efficiency.In order to further analyze the reason for the difference in enzymatic hydrolysis efficiency,the differences in surface morphology,cellulose crystal form,crystallinity,interplanar spacing,and grain size of p-Ts OH and p-Ts OH-N bagasse were compared and analyzed using SEM and XRD.The results showed that sodium hydroxide destructed lignocellulose by removing hemicellulose,so that the cellulase was accessible to cellulose,sodium hydroxide converted cellulose I crystal form(p-Ts OH pretreated bagasse)into the cellulose Ⅱ crystal form(p-Ts OH-N)was obtained.The cellulose Ⅱ crystal form had a larger interplanar spacing than the cellulose Ⅰ crystal form,and thus had a weaker hydrophobic action,Which was benefical to improve cellulase accessibility to cellulose.3.Based on p-Ts OH pretreatment bagasse enzyme hydrolysis efficiency was low and had the characteristics of high cellulose proportion,high crystallinity.After bleaching bagasse pretreated with p-Ts OH,two kinds of bagasse cellulose nanofibers(F-CNF and H-CNF)were prepared by using formic acid(organic acid)and hydrochloric acid(inorganic acid)combined with high pressure homogenization.In order to analyze the performance characteristics of CNF,such as the surface morphology,crystallinity,particle size,thermal stability and so on,SEM,transmission electron microscopy(TEM)and XRD,Fourier transform infrared spectroscopy(FTIR)and particle size distribution and Zeta potential,thermogravimetric analysis(TGA)were used.The results showed that F-CNF and H-CNF have higher crystallinity(F-CNF and H-CNF crystallinity were 78.73 and 81.46% respectively).4.In order to simplify the preparation process of bagasse cellulose nanofibers,and make the performance of lignin to reflect in bagasse cellulose nanofibers.Two kinds of unbleached bagasse nanofilms(F-LCNF and H-LCNF)were prepared without bleaching by using the combination of formic acid(organic acid)and hydrochloric acid(inorganic acid)with high pressure homogenization.In order to analyze the performance characteristics of LCNF,the surface morphology,crystallinity,particle size,thermal stability,and hydrophobicity were analyzed by using SEM,TEM,XRD,FTIR,particle size distribution and Zeta potential,TGA,water contact angle analysis(WCA).The results show that both F-LCNF and H-LCNF have higher water dispersibility(still stable for 30 days,F-LCNF was more stable),and both have higher thermal stability(F-LCNF and H-LCNF maximum pyrolysis temperature is 350.00℃ and 341.67℃ respectively),F-LCNF has higher hydrophobic performance.By analyzing the physical and chemical properties,desorption and adsorption regularity of bagasse before and after p-Ts OH pretreatment,this study revealed the reason why p-Ts OH pretreatment of bagasse can improve the enzymatic hydrolysis efficiency.Based on the advantages of high proportion of cellulose in p-Ts OH pretreatment bagasse and high crystallinity,the bleached or unbleached bagasse cellulose nanofilaments were prepared.This study can provide a theoretical basis for the rational application of p-Ts OH pretreatment of bagasse.