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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-rhamnosidase 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-desorption analysis, scanning electron microscopy (SEM) and transmission electron microscope (TEM) were used to characterize the physicochemical 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-rhamnosidase 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 Vmax and Km of the immobilized α-L-rhamnosidase 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 immobilized 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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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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