Enzymolysis Preparation Of Pure Nano-Crystalline Cellulose

Cellulose belongs to a kind of natural polymer, which has a wide range of sources and abundant production,and the degree of polymerization of cellulose is generally in the range of10,000 to 15,000. It plays a significant role in human’s daily life. However, the use of natural fibers is inefficient and low-costing.Under the appropriate conditions, natural fiber processed by physical method, chemical method, biological method and enzymatic hydrolysis, can be transformed into pure nano-cellulose, which can greatly increase the use of natural cellulose, and greatly improved the performance of pure nano-cellulose, such as the improvement of strength and biological activity, increases of specific surface area, and more sophisticated structures. The discovery of nano-cellulose solves the application problems of the natural cellulose, greatly promoting its use in various fields.Currently,the application of nano-cellulose has been throughout all industrial sectors, and this kind of emerging nanoscale materials has great potential commercial value.In this paper, we have used eucalyptus wood fibers to prepare nano-cellulose. First, we discussed the content of the eucalyptus wood fiber combustion ash and water-soluble substance,respectively,2.38% and 4.064%.Second, we discussed the process of preparing nano-cellulose from eucalyptus wood fiber.Pretreatment conditions with glycerol swelling use room temperature(25 ℃), stirring rate for 250 rpm and stirring time for 3h; the condition of enzymolysis process to prepare nano-cellulose using enzyme concentration 200u/m L,stirring speed 350 rpm, temperature setting 50 ℃. And the problems of preparation of nano-cellulose process,included glycerol swelling process and enzymolsis process, were briefly introduced in this paper.At the same time,nano-cellulose prepared through enzymatic hydrolysis was purified,included removing swelling agent and cellulase in the process of enzyme hydrolysis.Finally,the pure nano-cellulose was obtained,the yield of nano-cellulose reached18.12%After the preparation of pure nano-cellulose. Then use the high resolution field emission transmission electron microscopy(FESEM) and scanning electron microscopy(SEM) to analysis the micro morphology.Through the map of electron microscopy,the data shows that the distribution of nano-cellulose is more uniform, the size distribution of particle is in the range of 20~30nm.As a comparison, eucalyptus wood fiber directly dealt with enzymatic hydrolysis without swelling, the photos of laser particle size analyzer shows that diameter distribution range of cellulose is 300~500nm, we can draw a conclusion that the swelling agent has a great influence on the diameter of nano-cellulose.And swelling agent can infiltrate the crystalline cellulose into crystalline structure,the intermolecular or molecular internal force is destroyed, the crystallization area is easy for enzyme hydrolysis.Finally, the swelling agent and eucalyptus wood fiber with not fully enzymatic hydrolysis were recovered, the results shows glycerol recovery rate can reach 89.53%.At this time,the recycled eucalyptus fiber suffer from a thorough swelling, and after the treatment of cellulase, eucalyptus wood fibers are further refined, conducive to enzymatic treatment; and we can know from the recovery rate of glycerol, more times of glycerol recovery, glycerol recovery rate is low. The recovery rate decreased for two reasons: one is the artificial factors,the other one is swelling agent entering into the internal cellulose,resulting in consumption.The reducing of recovery rate of swelling agent also resulted in the decrease of yield of nano-cellulose; after enzymolysis, residual eucalyptus wood fiber and water solution which contains nano-cellulose were separated, the average recovery rate of eucalyptus wood fiber can reach 61.12%; after 3 times of recovery of the eucalyptus fiber, the eucalyptus fiber were completely transformed into sugar; the recovered eucalyptus wood fiber with the200u/m L cellulase,at about 1.5 hours, the nano-cellulose yield is the highest, reaching13.89%.