Preparation of Icariin by Hydrolyzing Epimedin C with Immobilized α-L-Rhamnosidase
OBJECTIVE To prepare t he immobilized α-L-rhamnosidase on SBA 15 mesoporous silica to promote the efficient conversion of epimedin C to icariin.METHODS SBA-15 was modified through amination and aldehydeylation,and the α-L-rhamnosi-dase was covalently coupled onto SBA-15.The immobilization conditions were optimized using the enzyme loading capacity and relative enzyme activity as evaluation index.X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),N2 adsorption-desorp-tion analysis,scanning electron microscopy(SEM)and transmission electron microscope(TEM)were used to characterize the physico-chemical properties of immobilized α-L-rhamnosidase.Using epimedin C as substrate and free α-L-rhamnosidase as control,the optimal enzymatic hydrolysis conditions,enzymatic kinetic parameters and recyclability of the immobilized α-L-rhamnosidase were investigated.RESULTS The optimal pH was 3.5,the optimal temperature was 35 ℃,the optimal immobilization time was 4 h and the optimal α-L-rh-amnosidase concentration was 8 mg·mL-1.The immobilized α-L-rhamnosidase showed a well-retained activity of 198.6 μmol·h-1·g-1 as well as a high enzyme loading capacity of 256.9 mg·g-1 support.The optimum hydrolysis conditions were as follows:pH 4.5,conversion temperature 50 ℃,substrate concentration 0.5 mg·mL-1,and transformation time 12 h.The and Km of the immobilized α-L-rhamnosi-dase was 0.505 μg·min-1 and 0.787 mmol·L-1,respectively.After four cycles of reuse,the residual relative enzyme activity of the immo-bilized α-L-rhamnosidase was more than 65％,which showed good stability.CONCLUSION The immobilized α-L-rhamnosidase has a high enzyme loading capacity,strong enzyme activity and good reusability,which can be used for efficient conversion of epimedin C to icariin.
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维普
