Study On Immobilization Of D-psicose3-epimerase

D-psicose is a newly found functional factor with many special health care functions, suchas low energy, lower blood sugar,improving intestinal flora, anti-caries and other physiologicalfunctions.D-Psicose3-epimerase(DPE) is an enzyme that catalyzes the reversibleisomerization between D-fructose and D-psicose. In this study,the calcium alginate gels isused as carrier to immobilize the microbial cells with DPE.In addition,different carriers areused to immobilize DPE.The results are as follows:Select alginate as a carrier of immobilized cells and glutaraldehyde as a cross-linkingagent to make microspheres.The results show that the optimum immobilization conditionsare:3.0%sodium alginate,60g/L of embedded cell,2%CaCl2,solidifying time4h,0.01%flutaraldehyde,crosslinking time4h.Under the optimum condition,the recovery rate reaches76%.After8times repeated operations,the recovery rate reaches more than61%,showinggood operational stability. Compared with the free microbial cells with DPE,the optimumtemperature of immobilized DPE raises5degrees,the pH value isn’t changed.Besides,the pHand thermal stabilities of immobilized DPE are better than the free microbial cells.The DPE was immobilized on7kinds of ion-exchange and adsorption resins, in whichD202-Ⅱwas the best material for the immobilization, then the enzyme was immobilized bycross-linkage of glutaraldehyde. The results showed that the optimum immobilizationconditions were:15U/0.5g (activity units/resin), immobilization temperature30℃,andimmobilization time4h.The concentration of the crosslinking agent (glutaraldehyde) was0.05％.The crosslinking time was4h. The remaining activity was more than65%of the primaryenzyme activity after the immobilized enzyme was used repeatedly for7times.Using sol-gel method can make microspheres easily.Dropping the mixed solution ofFe3O4and chitosan into the high concentration of condensate fluid containing sodiumhydroxide can make good magnetic beads with Fe3O4core,chitosan shell and good magneticseparation.Use magnetic beads as the immobilized enzyme carrier, glutaraldehyde ascross-linking agent to immobilize DPE.The optimum immobilization conditions were:2.5%chitosan,the ratio of Fe3O4to chitosan was4:3,20U/g(activity units/resin),immobilizationtemperature40℃,and immobilization time4h. The concentration of the crosslinking agent(glutaraldehyde) was0.01％.The crosslinking time was3h.The immobilized enzyme shows agood operational stability with high activity recovery remaining after repeatedly using for10times.Compared with the free DPE,the optimum temperature of immobilized DPE raises5degrees,the pH value isn’t changed.Besides,the thermal stabilities of immobilized DPE arebetter than the freeDPE.pH stabilities is very different from the freeDPE.