Research On The Immobilization Of Xylanase By Ion-exchange Resin And Its Enzymolysis Kinetics

Xylanase was immobilized with porous anion exchange resin to produce xylooligosaccharides.The preparation of free enzyme,selection of carrier, optimization of immobilization,properties of immobilized enzyme and continuous production of xylooligosaccharides were mainly investigated in this thesis.The main results were as follows:1.Developing an ideal cartier is one of the important topics of immobilization study,anion exchange resin resin D280 was selected from 15 kinds of resins as good carrier to immobilize xylanase.2.The optimal conditions of absorption and crosslinking were studied with glutaraldehyde as crosslinlting agent and anion exchange resin D280 as carder.The results were as follows:270 U enzyme per g wet resin was immobilized for 5 h at 20℃and pH 5.3,then crosslinked with 0.5%(final concentration)glutaraldehyde for 1 h at20℃.The enzyme activity reached 85U/g(carrier)and the activity yield was 31.48%.3.The test of immobilized enzyme indicated that the optimal temperature of the immobilized enzyme was 60℃,which was lower than that of the soluble enzyme by 5℃.Thermal stability of the xylanase was enhanced by immobilizing treatment.The optimal pH of xylanase removed to acidity by immobilization,pH stability were improved by immobilization comparing with the free enzyme.The K_m value was 3.4 mg·ml^-1,which was a little higher than that(2.15 mg·ml^-1)of the free enzyme.This indicated that the affinity between enzyme and substrate decreased significantly.The metal ions Ca²⁺,Zn²⁺,Fe³⁺,NH⁴⁺,Cu²⁺had different inhibition on immobilized enzyme.Ag⁺,Pb²⁺ions de-activate the enzyme completely,Na⁺,K⁺,Mg²⁺,Co²⁺,EDTA had activation on immobilized enzyme,Ba²⁺,Mn²⁺had no inhibition and activation on soluble and immobilized enzyme.The storage stability in 4℃refrigerator was more enhanced after immobilization.The immobilized enzyme demonstrated a good reusability for it was able to maintain 80%of itsactivity after six cycles of reaction.Under the condition of pH5.3,55℃,the half-life of the immobilized enzyme was only 30 days.4.The comcob xylan was enzymatic hydrolyzes into crude xylooligosaccharides with immobilized xylanase.A good result was observed with the hydrolysis of the 2%(corncob xylan)using 240 U/g of immobilized enzyme for 12 hours.Immobilized xylanase can be made by absorption and crosslinking with anion exchange resin with high activity yield and good practical stability,having the industrial prospect to synthesize.