Immobilization and stabilization of cholesterol oxidase on modified sepharose particles.

For the cholesterol oxidase from Brevibacterium sp. M201008 was not stable as free enzyme form, it had been covalently immobilized onto functionalized sepharose particles that were activated with N-ethyl-N'-3-dimethylaminopropyl carbodiimide (EDC).The optimal conditions of enzyme immobilization were determined, and the immobilized enzyme activity was 18.03 U/g of support. The surface morphology and thermal behavior of the immobilized enzyme were observed by scanning electron microscopy and differential scanning calorimetry, respectively. The binding of the enzyme to support was confirmed using Fourier transform infrared spectroscopy. The results demonstrated that the thermal, pH, and storage stabilities of cholesterol oxidase were increased by immobilization. More than 90% of the initial activity of the immobilized enzyme was remained at the points of pH 4.0 and 9.0, and that was much more stable than it was free enzyme form. Under same storage conditions, the free enzyme lost 97.8% of its initial activity after 45 h, whereas the immobilized enzyme only lost its 35.8% activity.