The Research Of Fusing CBD₁/CBD₂ To The Xylanase XynⅢ From Aspergillus Niger

Xylanase is the enzyme family that dehydrates xylan into xylose oroligoxylose. Xlyanase has extensive applications in the industries of feed, food, fabric and papermaking. Because of different goals, Xylanase should be have many different zymologic characteristics.XylanaseⅢfrom Aspergillus niger doesn’t work well in the extreme environments such as highly acidic or highly alkalic.So it’s all-important to recontrust the enzyme to fulfill the industrial needs.This study chose the gene, xynⅢobtained from Aspergillus niger A-25 and the gene CBD1/CBD2 which encoding the cellulose binding domain of the XynA obtained from Thermotoga maritime as materials to reconstrust the XynⅢ, and then overexpressed in Escherichia coli to investigate the characterizations of the recombinant proteins,and then research into the function of CBD1/CBD2, respectivly. There were four parts in this study:(1) The optimal pH of recombinant protein xynⅢ-CBD1,xynⅢ,xynⅢ-CBD2 are 4.2、3.8、3.8,respectivly. The recombinant protein xynⅢ-CBD2 is better used in acidic environment than the chimeric enzyme xynⅢ-CBD1 and xynⅢ.(2) The optimal temperature of recombinant protein xynⅢ-CBD1,xynⅢ,xynⅢ-CBD2 are found to be 47℃. After keeping 30min at 54℃, The relative activity of recombinant protein xynⅢ-CBD1,xynⅢ,xynⅢ-CBD2 are 90%,40%,40%,respectivly.(3) Measured Km and Vmax values for the substrate brich xylan , The recombinant protein xynⅢ,xynⅢ-CBD1, xynⅢ-CBD2 are 94ug/ml ,0.72um/ml/min;234ug/ml,1.71um/ml/min; 121ug/ml1.72um/ml/min,respectivly.(4) Measured Km and Vmax values for the substrate oat spelets xylan , The recombinant protein xynⅢ,xynⅢ-CBD1, xynⅢ-CBD2 are 148ug/ml,2.27um/ml/min; 171ug/ml,3.36um/ml/min; 64ug/ml,1.4um/ml/min, respectivly.