| Flexible immobilization has interested many researchers these years sinceimmobilization was developed fifty years ago. Supports are grafted with hydrophilicchain, the flexible chain, where enzymes are immobilized and flexible immobilization isconducted. The flexible chain makes it more flexible and affinitive, and collision forceof enzymes is declined. Thus the technology benefits enzymes by remaining naturalconformation, degree of freedom and homogeneous catalytic activity.Ethylenediamine, hexamethylenediamine and decamethylenediamine were graftedto the crosslinked chitosan microsphere. Then the glucose oxidase （GOD） wasimmobilized on each of them.Taking into account the effects of inner diffusional limitation （effectiveness factors,De）, carrier size （r0） and substrate concentration （s0）, the kinetic model of theimmobilized GOD were investigated. The larger the effectiveness factors, the easier. Asthe carrier size increases, on the other hand, the substrate diffusion declined. The valueof s0shows its influence slightly, and the higher substrate concentration makes thereactive rate higher and the productive coste lower.The immobilization process for each support was investigated. The pH7.0wassuitable for almost all of them. Molar ratio between GOD and amino groups of supports,glutaraldehyde concentration and crosslinking time were different with each other.When the CCH was used, molar ratio and glutaraldehyde concentration were the highest(2.1×10-4,0.35mol/L), and the crosslinking time was2.1h, the smallest value.Fluorescence images of the immobilized GOD showed that the highest relative activityfor the CCH owned to the largest specific surface area and the best distributed porousstructure.The GOD enzyme immobilized in CCH system could maintain88.1%of itsoriginal activity after240days’ storage at4℃, where84.9,81.8and80.5%are achievedrespectively for CCE, CC and CCD system. Reuse stability, acidoresistance andthermotolerance of the enzymes are both strengthened. |
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