Studying On Immobilization Of Xylanase From Aspergillus Niger On Chitosan Grafting Dialdehydle The Starch

The enzyme because the different of its structure and the characteristic are not all same,therefore the immobilized carrier and the fixed method also respectively have the difference.It is important to look for good characteristic carrier and the best immobilized method,thesedays,people still commit themselves to develop new type carriers and the new pattern.As for the xylanase enzyme,as a result of substrate some limits,the enzyme usually immobilized by the adsorption or covalent. The paper selected the best carrier from two layer inorganic materials(layered Double Hydroxide andα-Zirconium phosphate)and natural polymer- Chitosan,The conditions for immobilization were optimized.The immobilized enzymes were further characterized in terms of their catalytic activity,kinetic parameters and thermal stability, etc.The main results were as follow:1.Developing an ideal carrier is one of the important topics of immobilization study. Chitosan grafting Dialdehydle the Starch which was selected from three kinds of different materials showed good immobilization effect on the xylanase from Aspergillus niger-25.The optimal condition for xylanase immobilization were as follow: Dialdehydle the Starch(the oxidized degree is 90%),1.0g;the time pretreated Chitosan at 70℃,16h;the amount xylanase used,4ml(0.2M,pH5.6 acetic- sodium acetic buffer);the temperature and time for immobilization,30℃and 8h,respectively. The activity yield was 63%.2.Compared to the free enzyme,Immobilization of xylanase from Aspergillus niger-25 on Chitosan grafting Dialdehydle the Starch and Chitosan showed that:both of the optimum pH were 4.6,pH stability did not change significantly by the immobilization, and was stable at pH 4.6～8.6,however,the immobilization effect by Chitosan grafting Dialdehydle the Starch was better than the Chitosan.The optimum temperature of the immobilized enzyme by Chitosan grafting Dialdehydle the Starch and Chitosan increased from 50℃to 55℃and 60℃,respectively,the thermalstability of the immobilized enzyme increased significantly and for Chitosan grafting Dialdehydle and Chitosan immobilized enzyme at 50℃which their half life were 2.35 and 1.51 times compared to the free enzyme,respectively.The storage stability in 4℃refrigerator was improved after immobilization.,the relativity activity was retained at 85%while the free enzyme was 60%after storaged 76 days.To the both immoblized enzymes,the affect of all ions used in the experiments were different,the metal irons K,Mg and EDTA had activation the immobilized enzyme by the Chitosan grafting Dialdehydle the Starch,but to the Chitosan immobilized enzyme which were inhibited.The other irons could not enhance the activity of the xylanase except Ag iron.For Chitosan grafting Dialdehydle the Starch and Chitosan immobilized enzyme,the K_m values for birch xylan slightly increased from 1.14 mg/ml to 1.39 and 1.17 mg/ml,respectively,which was indicated immobilization of xylanase essentially conserved the affinity of the enzyme towards its substrate.Increases in V_maxupon immobilization are generally not observed.However,V_maxvalues of the immobilized enzyme by Chitosan grafting Dialdehydle the Starch was slightly enhanced in this study.3.Immobilized xylanase by the Chitosan grafting Dialdehydle the starch carrier hydrolyzed the Birchwood xylan,the component of the hydrolyzed solution by the HPLC analysed indicated a good result.