Study On Increasing Astragalus Polysaccharide Content And Concentrating Selenium On Polysaccharide By Fermentation

Astragalus is a kind of traditional Chinese medicine used in clinical practice.Its main component,Astragalus polysaccharides?APS?,has a wide range of pharmacological effects.But low content and extraction yield have limited its wide application.With the increasing popularity of traditional Chinese medicines,it will produce a large amount of leftovers during processing which were basically discarded.In fact,there are still many nutrients and Chinese medicines active ingredients in leftovers which are good raw materials used for fermentation.In order to study the feasibility of increasing the content of APS by fermentation.Firstly,optimize the extract conditions of APS and use the APS extraction as sole carbon source to screen strains that could increase APS content.Secondly,optimize composition of fermentation medium and culture conditions.Finally,study the bio-selenylation and anti-tumor activity of APS.The results are as follows:1.The three factors affecting the extraction of APS:extraction temperature,solid-liquid ratio and extraction time were studied by single factor experiment and orthogonal experiment.The best extract method of APS is that Astragalus powder mixed with water by 1:25?g:ml?and refluxing extracted for 120 min at 90?.Under this condition,the content of APS in extraction was?4.870±0.031?g/L.2.Using the APS extraction as sole carbon source.A strain of Aspergillus niger which could increase the content of APS was screened from the strains preserved in laboratory.The content of APS was?1.585±0.094?g/L after fermentation and was 22%higher than before fermentation.There was no major change in the structure of APS before and after fermentation analyzed by infrared spectroscopy.3.Using the Aspergillus niger as starting strain to optimize the composition of fermentation medium and culture conditions by response surface experiment and orthogonal experiment.The optimal fermentation conditions were determined as follows:APS extraction 250 ml/L,peptone20 g/L,NaNO₃ 4.23 g/L,MgSO₄·7H₂O 0.75 g/L,K₂HPO₄ 1.07 g/L,KCl0.58 g/L,fermentation temperature 30?,initial pH 5.0,shaker speed 180r/min for 6 days.Under this condition,the content of APS reached?2.351±0.057?g/L.4.Using the Aspergillus niger as starting strain to study its tolerance and enrichment capacity to inorganic selenium.The maximum selenium tolerance was 14?g/ml and the fermentation time was 7 days.The optimum amount of sodium selenite was determined to be 10?g/ml and selenium content reached?14.572±1.403?mg/kg detected by ICP-MS.There may be Se=O structure in Se-APS analyzed by infrared spectroscopy.So it is inferred that selenium is combined on APS by group of selenium acid.Anti-tumor experiments in tumor-bearing mice demonstrated that Se-APS have the effect of promoting growth and inhibiting tumors,it has better anti-tumor effect and less side effects combined used with 5-FU.