| Summary: | 碩士 === 國立臺灣大學 === 生物科技研究所 === 105 === Ginkgo biloba is known as the ginkgo tree. The tree is widely cultivated in northeast Asia and its fruit has various uses in traditional medicine. Ginkgo biloba leaf extract also have been proved to have wide biological activities. However, ginkgolic acid is a toxic compound in the leaf and the fruit of Ginkgo biloba and it should be less than 5 ppm in the ginkgo product in the guide of Commission E.
Laccase was immobilized on solid carriers by crosslinking reaction for the degradation of ginkgolic acid in this study. The binding ratio of laccase could reached 88% on the carrier. In SEM image, carriers with immobilized treatment had significant difference compared with carriers before immobilized in surface morphology. ESCA image also shown that the signal of C=N double bond appeared after carrier with immobilized treatment. These results proved that laccase immobilized on the carriers after crosslinking reaction.
Degradation efficiency of immobilized laccase was also well researched in this study. The activity of immobilized laccase could be 25.0 ± 3.06 compared with free laccase (27.5 ±1.67). Moreover, the Km value of immobilized laccase is 0.06 compared with free laccase (0.10). The complete reaction can be less than 1 hour and the reusability and storage stability were also further verified. The enzymatic system can be used more than 25 cycles and 10 weeks which still retained 73.8% of enzyme activity. The results indicated that the immobilized laccase system exhibited a significant efficiency for ginkgolic acid degradation in Ginkgo biloba leaf extract. It is capable of being further applied to prepare large scale of ginkgolic acid free ginkgo product.
Key words : ginkgolic acid, enzyme immobilization, laccase and enzyme kinetic.
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