Characteristics Of Cellulase System Of Aspergillus Niger And Its Application In Hydrolysis Of Bagasse

Sugarcane bagasse, the main by-product of sugar industry and an important renewable biomass resource, is the fibrous residue after the sugarcane stalk is crushed to extract its juice. Cellulase complex that can break down cellulose into glucose, mainly includes EC3.2.1.4 (EG), EC3.2.1.9 (CBH) and EC3.2.1.21(BG). These three types of enzymes by synergism can hydrolysis bagasse cellulose into monosaccharides or oligosaccharides that can be used directly, thus providing a sustainable solution to increasing demands of energy and resources, even environmental constraints. The main research contents and results in this study are as follows:Based on the genome information of Aspergillus niger, shake flask fermentation was used for preparations of 33 cellulases which from the genome of Aspergillus niger and were encoded by en4gA,en4gB,en4gC,en4gD,en4gE,en4gF,en4gG,en3gA,en3gB,en3gC,eglA,eglB,eglC,eglD,englA,xengA,xengB, cbhA,cbhB,cbhC, bgA,bgB,bgC,bgE, bgF,bgG, bgH, bgl, bgJ, bgK, bgL, bgM and bgN respectively. The enzymatic properties of cellulase were studied, the analysis of the study contributes to the development of enzymes with new functions, laying the foundation for the application of cellulase systems.The optimum reaction conditions of 17 kinds of endoglucanases were different. The optimum temperature was between 45? and 65?,the optimum pH was between 3.0 and 6.0, and they have good resistance in high temperature and acid, under the condition of 45?60? and pH 4.0?6.0, they can retain 80% enzyme activity. The optimum reaction conditions of the 3 exoglucanases were 50?60?,pH 6.0?7.0. The 3 exoglucanases have good thermal stability and pH stability. The optimum reaction conditions of 13 kinds of?-glucosidases were different, the optimum temperature was between 40? and 60?, and the optimum pH was between 4.0 and 6.0, they can retain 80% enzyme activity at 50?60?and pH 4.0?6.0, but its thermal stability is poor.The best combination cellulose synthase is EnglA, CbhC and BgF that optimum reaction condition was 55?,pH 5.0-6.0 for 15-16 h by screening.Additions of pectinase, protease, hemicellulase, cellulase into the bagasse for sequential reactions were used to evaluate the hydrolysis rate of the various components of bagasse. The results show that hydrolysis rates of pectin, protein, hemicellulose and cellulose were 0.73%, 0.542%, 15.79%, and 11.98% respectively.