Microbial transformation of polydatin and emodin-8-β-D-glucoside of Polygonum cuspidatum Sieb. et Zucc into resveratrol and emodin respectively by Rhizopus microsporus
Rhizopus microsporus isolated by our laboratory was able to transform polydatin into resveratrol and emodin-8-β-D-glucoside into emodin, respectively, through the fermentation of Polygonum cuspidatum Sieb. et Zucc. The fermentation products were separated and purified by H1020 resin and silica gel column chromatography. Thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) were used to identify the products and evaluate the transformation efficiency. A variety of parameters of submerged state fermentation, including the growth characteristics, the change of β-glucosidase activity and the amount of polydatin, resveratrol, emodin-8-β-D-glucoside, emodin, and the dissolved oxygen, were monitored simultaneously. The amount of resveratrol yielded increased dramatically from 0.04 g/l at the beginning to the maximum value of 0.34 g/l at 36 h of fermentation, and emodin was from 0.4 g/l to 0.65 g/l at 80 h. The transformation rate of glycosides reached 98% and the purity of both resveratrol and emodin was 95%.