Enzymolysis Preparation Of Nano-crystalline Cellulose And The Controlling Of Reducing Sugar Content

With the rapid consumption of fossil energy, natural and mineral resources, and theemergence of the environmental pollution, the efficient usage of the renewable resources hasbeen paid more and more attention by the researches. The cellulose, one of the renewableresources in the nature, receives the public concerns due to its renewable property and lowerprice. The cellulose can be degraded to Nano-Crystalline Cellulose (NCC), which has beenwidely used in many industrial fields because of its unique physic and chemistry property.This article reported the preparation of NCC from the single and composite enzymolysis ofeucalyptus fiber, and discussed the influence of metal ions on the yield of reducing sugar. Theinfluences of the pretreatment and experimental conditions on the yield of NCC were alsodiscussed.The influence of pretreatment and experimental conditions on the yield of NCC wasinvestigated with fiber analyzer, light microscope (LM), scanning electron microscope (SEM),Raman spectra (RS) and Fourier transform infrared spectroscopy (FTIR), respectively. Theresults indicated that cellulose pretreated with glycerol was swollen and glycerol could berecycled. The NCC, which was prepared from the single cellulase enzymolysis and thecomposite enzymolysis of cellulase and xylanase without adding buffer solution, had noobvious changes in the characteristic peaks of FTIR compared with the untreated cellulose.They remained essentially the same absorption wave, just differentiated in the absorbingintensity and the position of the absorption band, which exhibited that the morphologicalstructure of the cellulose changed after processing. The as-prepared NCC had a goodmonodispersity in the reaction conditions of cellulase concentration200u/mL, reactiontemperature50℃, reaction time5hours and stirring speed350rpm. There were two kinds ofNCC particles in the cellulase enzymolysis, most of them were solid spherical with mean sizeof about20~40nm, and a few of one-dimension rod-like particles with the size of severalnanometers. In addition, NCC particle with mean sizes of20~30nm was prepared by thecomposite enzymolysis. The optimum reaction conditions are enzyme concentration(cellulase: xylanase=9:1)20u/mL, reaction temperature50℃, reaction time5hours and stirring speed350rpm. And the final morphology of the product showed the synergy betweencellulase and xylanase.The influence of metal ions on the yield of reducing sugar indicated that the reducingsugar content could be controlled effectively when adding zinc chloride (ZnCl2) and calciumchloride (CaCl2), especially ZnCl2. The yield of reducing sugar could be controlled when theconcentration of CaCl2was1.11mg/mL and CaCl2not only could lower the reducing sugarcontent but also increase the yield of NCC. Besides, the reducing sugar could be controlled to0.1%when adding1.2mg/mL of ZnCl2. In addition, the adding time of the metal ions alsoaffected the reducing sugar content. The results indicated that not only the amount of theresidual fiber decreased but also the yield of NCC improved when adding Ca2+at thebeginning of the enzymolysis. The delayer adding Ca2+, the lower of the reducing sugarcontent, in which may be due to the inhibition of the enzyme activity.