| Summary: | 碩士 === 大同大學 === 生物工程學系(所) === 97 === D-Amino acid oxidase from Rhodosporidium toruloides was expressed by E. coli and immobilized onto glutaraldehyde activated magnetic nanoparticles. Approximately four enzyme molecules were attached to one magnetic nanoparticle when the weight ratio of the enzyme to the support was 0.12. After immobilization, the Tm increased from 45oC of the free form to 55oC, indicating the thermal stability was improved. At the presence of 20 mM hydrogen peroxide, the immobilized form retained 93% of its activity after 300 min while the free form was completely inactivated after 210 min, suggesting the oxidative stability against hydrogen peroxide was also improved. Although the stability was enhanced through immobilization, the catalytic efficiency (kcat/KM) was decreased by 3.5 fold. The immobilized enzyme could be recycled, 15% of the initial activity was retained after 10 reaction cycles.
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