Microbial Transformation Of Polygonum Cuspidatum Sieb.et Zucc By Rhizopus Sp.

The dry root of Polygonum cuspidatum Sieb. et Zucc is commonly known as P. cuspidaturn, a well-known traditional Chinese medicine officially listed in the Chinese Pharmacopoeia. It is believed that its main active components are stilbenes and anthraquinone, with the former includes polydatin and resveratrol, and latter mainly emodin and its glycoside. Polydatin is the main active compound with the content of about 2% in the dry root of P. cuspidatum. Another bioactive component in P. cuspidatum is resveratrol, which has a variety of activities including antioxidant, anti-platelet aggregation, vaso relaxing, anti-cancer, function as estrogenic, but its content is only about 0.1% - 0.2% in the dry root. It is reported that polydatin could be hydrolyzed by glucosidases, the enzyme that were produced by human intestinal bacteria, to give rise to aglycone. Anthraquinone, another type of active compounds in P. cuspidaturn, includes emodin, physcion and emodin-8-O-β-D-glucoside, among which emodin exhibits the stronger bioactivities like anti-bacteria, diminishing inflammation than emodin-8-O-β-D-glucoside.At present, alkaline hydrolysis has been commonly used on the production of resveratrol and its related compounds from red juices. Emodin-8-O-β-D-glucoside can be hydrolyzed at acidic conditions. A study has explored the possibility of hydrolyzation of polydatin into resveratrol byβ-glucosidase. Microbial transformation of polydatin into resveratrol and emodin-8-O-β-D-glucoside into emodin can be achieved byβ-glucosidase usually happens at mild conditions with rather low cost. Accordingly, microbial transformation may own the advantages of environment friendly and cost efficiency.There are those works as follows in this study.ⅠScreen the strains which can transform polydatin and emodin-8-O-β-D-glucoside into resveratrol and emodin, respectively.ⅡStudy on the optimizing of fermentation conditionsⅢKinetics of fermentation was studied to follow the transformation process in order to optimize the fermentation parameters.ⅣStudy on the purification and identification of resveratrol and emodin.The main results are showed below:ⅠStrain-screening test seted up was used to isolate a strain which can transform polydatin into resveratrol and emodin-8-O-β-D-glucoside into emodin should be attributed to the function ofβ-glucosidase, which is produced during microbial metabolism. The strain isolated was named Rhizopus sp. T-34.ⅡOptimizing of the fermentation conditions of transformation with Rhizopus sp. T-34. Culture medium of the germ: lixivium of corn 50%, lixivium of bran 6%, solution of salt 1%; According to the static method and the technology optimizing disposition of the system factors with all over feedback control, the concentration of resveratrol reached the highest in the following condition: 100 mL of culture medium in a 250 mL flask by adding 10g substrate at 72h, and incubating at 28℃with agitation speed at 140rpm.ⅢThe kinetics of submerged state fermentation, including the growth characteristics in batch culture, the change ofβ-glucosidase activity, together with the amount of polydatin, resveratrol, emodin-8-O-β-D-glucoside and emodin, and the dissolved oxygen, was monitored simultaneously.ⅣH103 resin was used to enrich resveratrol in the fermentation liquor. Twenty-five varieties of resin were screened by static state adsorption test and H103 was chosen out for its strong adsorption capability. Meanwile, the concentration of 0.650 g/l, pH 4 and work speed of 3 BV/h were the optimal conditions. Resveratrol and emodin on H103 resin were eluted with 90% ethanol at 3.2 BV/h speed. The purity of extracted resveratrol could reach 32.5%. This crude extracts were further purified by ethyl acetate, the purity could reached 54%.