| Panax quinquefolius,belongs to the Panax genus in the Araliaceae family,the efficacy and appearance of which are similar to traditional ginseng.Ginseng root is a kind of medicinal materials with high economic value and a long history of application in the traditional Chinese herbs for its being rich in active ingredients,exhibiting diverse pharmacological activities such as norishing yin and invigorating qi,anti-aging,anti-fatigue,anti-inflammatory and anti-tumors.Panax quinquefolius was listed as the material production and operation pilot for both food and traditional Chinese medicine in2019.Pharmacological research has indicated that ginsenosides are the main physiological active components,therefore,how to increase the content of ginsenosides and transform rare ginsenosides has become a hot research topic for many years.The ginsenosides are classified into three groups: dammarane-type,oleanoid-type and octilonol-type.The main ginsenosides are dammarane tetracyclic triterpenoids.The dammarane saponins can be divided into protopanaxadiol(PPD)and protopanaxatiol(PPT)by comparing the different sugars linked to C-3,C-6 and C-20 position.The biotransformation of ginsenosides is that modifying the glucosyl at the C-3 and C-20 position of PPD ginsenosides or the glucosyl at the C-6 and C-20 position of PPT ginsenosides by the usage of relative enzymes produced by microorganisims,in this method,the major ginsenosides could be hydrolyzed and then converted into minor ginsenosides.What's more,this biotransformation method is characteristic of no-pollution and low-cost.In this study,a strain that could convert ginsenoside Rb1 into Compound K was isolated from Panax quinquefolius rhizosphere soil.The DNA was amplified and the phylogenetic tree was established for the molecular biological classification of this stain,and then,the fermentation and transformation conditions of the strain were optimized to improve the transformation efficiency,the research results are as follows:1.This stain was Bacillus sp.strain AU3b4(MF612187.1)by analyzing the 16 s rDNA and phylogenetic tree.2.The crude enzyme liquid containing ?-glucosidase,which can specially convert ginsenoside Rb1 into Compound K,was isolated from strain Bacillus sp.strain AU3b4(MF612187.1)and the enzyme activity was determined by measuring the amount of pNP released after the enzymatic hydrolysis of pNPG through UV-visible spectrophotometer,the enzyme activity of which was 667U/mL.3.The crude enzyme solution was then used to optimize the transformation temperature,pH and transformation time.The transformation results were tested by TLC and HPLC,respectively.The appropriate transformation conditions were determined:When the addition amount of saponins was 1 mg/mL,the transformation temperature was25 ?,pH 7.0,then transformed 6 days according to above,the transformation rate can reach 41%.4.?-glucosidase from strain Bacillus sp.strain AU3b4(MF612187.1)exploits hydrolysis pathway Rb1?Rd?F2?Compound K analyzed by TLC and HPLC.Therefore,the Bacillus subtilis strain that could be used to specially transform ginsenoside Rb1 into rare ginsenoside Compound K was screened out in this study,which provided a new pathway and reference for the converting of ginsenoside Rb1 into ginsenoside Compound K. |
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