| Cellulose is one of the most abundant natural resources in the world. The efficient utilization or transformation of cellulose into biobased chemicals is of great significance. At present, the application of ionic liquids (ILs) in cellulose research generally revolves around dissolving cellulose in ILs and subsequential sarccharification of cellulose brought out by ILs pretreatment. However, the two-step process is painstaking and time consuming work and the use of organic regenerating reagents might lead to serious environmental pollutions. In order to overcome these problems and further improve cellulose conversion, intensive studies were made to achieve more efficient utilization of cellulosic materials.In this study, Three kinds of imidazolium ionic liquids of alkylphosphate ([Emim] DEP)、acetate ([Emim]Ac) and chloride ([Bmim]C1) were synthesized through simple method. Their chemical structures were confirmed by1H-NMR and FT-IR. The physical and chemical properties of three ionic liquids were analyzed. The different solubility of sugarcane bagasse cellulose in three ionic liquids under microwave radiation was studied. Then, the effect of three ionic liquids on cellulase were investigated. Both the original and regenerated cellulose were characterized by X-ray diffraction(XRD), infrared spectroscopy(FT-IR), thermogravimetric analysis(TG) and scanning electron microscopy(TEM). Then, High pressure homogenization was used to produce cellulose nanoparticles in the homogeneous system of [Emim]DEP and sugarcane bagasse cellulose, then in situ enzymatic hydrolysis of sugarcane bagasse cellulose was carried out in ionic liquids with cellulase. During the process, The optimum dissolution condition was confirmed by the orthogonal experiment, and the effect of high pressure homogenization (HPH) process on enzymatic hydrolysis was studied. The supermolecular structure of cellulose was characterized by XRD, particle size analysis, TEM and the molecular weight analysis. Finally, The optimum in situ enzymatic hydrolysis condition was confirmed by analyzing the factors. After enzymatic hydrolysis, neutral alumina column chromatography was used to separate the cellulose hydrolysis products. The structure and solubility properties of recovery and original ILs were characterized.The results are as follows:[Emim]DEP was chosen as an environment-friendly solvent for enzymatic in situ saccharification in view of its biocompatibility and excellent solubility of cellulose. The results of characterizations indicated that regenerated cellulose was of great benefit to the subsequent downstream processes, such as enzymatic hydrolysis. In the case of pretreatment step, The optimal condition was confirmed to be lwt%Sugarcane bagasse cellulose dissolved in ionic liquid [Emim]DEP at110℃with microwave power of400W, then homogeneous solution was prepared by HPH process at a certain pressure with20cycles after dissolved. According to the results of characterizations, the CI, size and molecular weight changes caused by HPH process resulted in cellulose accessibility to enzymatic hydrolysis, which enhanced the conversion of cellulose. Finally, The optimal enzymatic hydrolysis condition was confirmed. Homogeneous solution was prepared by HPH process, concentration of ionic liquid [Emim]DEP was7.5%after adding buffer, and concentration of cellulase was1.745FPU/ml, then enzymatic hydrolysis was carried out at50℃for24h. According to the results of characterizations, recovery ILs can be reused and its structure and properties is unaffected.In conclusion, the pretreatment of homogeneous solution by HPH process was applied into pretreatment and in situ enzymatic hydrolysis of sugarcane bagasse cellulose. The HPH process enhances the in situ enzymatic hydrolysis efficiently, which may provide a new way for the production of cellulosic ethanol (one of the second generation biofuel) and also the theoretical basis for the efficient development and utilization of agricultural scrap cellulose. |
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