Cloning And Expression Of Xylanase And Its Preliminary Application Study

Xylanase is the hydrolase families which can cleave polysaccharide Xylaninto Xylooligosaccharide and Xylose. Also, it can be used to catalyze theendohydrolysis of1,4-β-D-xylosidic linkages in xylan and mass of whose hydrolyzateare Xylanase and other oligosaccharide. In this study two pares were carried out. I:The expression of Xylanase gene in two expression systems, E. coli BL21（DE3）andPichia pastoris. Xylanase gene was obtained from Aspergillus niger. The recombinantplasmids were linearized by SacI, then transformed into E. coli BL21(DE3) andPichia pastoris.. Adding IPTG and methanol to induce the expression of Xylanase（E.C3.2.1.8）.The induced production was analyzed by SDS-PAGE to evaluate themolecular weight of the target protein assayed by DNS to detect the enzyme activity.The results come out that the two expression systems can express Xylanaserespectively. The Xylanase expressed in prokaryotic expression has no activity. Whilethe Xylanase expressed in eukaryotic expression has natural activity. However, themolecular weight of the product is larger than predicted. Part II: Application ofXylanase as a prebleachin agent on pulps. The Xylanase was obtained from solid stateleavening of Aspergillus niger C3486. The crude product was purified and extractedby DNS detecting the activity of the enzyme. Finally, the bleaching ability of the kraftpulp was studied by pre-treating the Xylanase. The optimal bleaching condition waspH value4.5~5.0,40~50℃,1~2h,30~40IU/g. Under these technologicalconditions the brightness of the papers treated by H2O2bleaching increased by6.5%ISO, tearing index decreased by1.6Kpa.m2/g, bursting index increased by20.68N.m/g. Therefore, the experimental results showed that bleaching ability of the pulp isimproved and its physical ability is also enhanced by Xylanase pretreatment.