Research on transformation of resveratrol and soybean isoflavone by microbic metabolic enzyme / 解放军医学杂志

ABSTRACT

Objective To establish a better and easier method for producing resveratrol and soybean isoflavone from polydatin and genistin by microbic metabolic enzyme. Methods The fungal strain Aspergillus niger S was fermented with solid medium. The enzyme isolated from Aspergillus niger S was purified by precipitation with ammonium sulfate and column chromatography with Q sepharose fast flow and superdex G200. The purified enzyme could be used to transform both resveratrol and soybean isoflavone. An analytical method for all the transformed products was established by the improved RP-HPLC. The HPLC separation was performed using a C18 250mm?4.6mm column and a gradient elution program. The eluent was acetonitrile/0.1% acetic acid in a flow rate of 1ml/min. The wavelength for ultraviolet detection was 280nm. Results The molecular weight of the enzyme isolated from Aspergillus niger S was about 165 kD, which was quite different from other reported glucosidases. The optimal temperature for this enzyme was 50℃, and the enzymatic activity decreased when the temperature dropped below 40℃ or elevated over 60℃. The optimal pH values were 5-10, and the enzyme would lose its activity if the pH was below 4. It was revealed by improved RP-HPLC that the products were polydatin and genistin at 27min and 39min, respectively, before enzyme treatment, while the transformed products at 45min and 64min after the enzyme treatment were resveratrol and genistein, respectively. Conclusions This purified enzyme isolated from Aspergillus niger S can transform both resveratrol and soybean isoflavone from low active form to high active form. It is a convenient and accurate method for the determination of resveratrol and soybean isoflavone. This method may be very useful in industry as well as clinical experimentation.