Study On The Separation And Structrue Of Extracellular Polysaccharides From Dunaliella Salina

The exopolysaccharides were extracted from D.salina. The optimum culture condition for the exopolysaccharides exudation, separation, purification and structure of the exopolysaccharides of D.salina were investigated, and the bioactivity of the exopolysaccharides from D.salina was tested.The crude solution containing extracellular polysaccharide was obtained by centrifugation and ultrafiltration from the Dunaliella salina culture, followed by the ethanol precipitation, washing with acetone and anhydrous ether and freeze drying. The optimal culture condition was studied by the single factor trial and orthogonal array design. The results showed that when NaCl=0.8mol/L, KNO₃=800mg/L, KH₂PO₄=5mg/L and pH=8.5, the yield of the exopolysacharrides was the highest, reached 489mg/L.The addition of EPS at 0.5 g/L could significantly inhibit the oxidation of OH, with the inhibition rate at 87.67% as compared to 63.68% of the ascorbic acid control. By observing the stimulative activity of D.salina exopolysaccharides to beneficial bacteria in vitro, it is found that this exopolysaccharides could effectively promote the growth of the beneficial bacteria and enhance its livability.After the primary purification using the double-enzyme hydrolyzation and the dialysis, two components named as EPS I and EPS II, which were identified using the agarose gel electrophoresis, were purified by cellulose DEAE-52 ion-exchange chromatography. As a result, the polysaccharide contents of EPS I and EPS II were determined to be 61.34% and 52.81%, and their protein contents were 3.97% and 1.35%, respectively, while the nucleic acid contents were lower than 0.025%, indicating a relative high purity. The analysis results from thin layer chromatography and gas chromatography further identified that EPS I was composed of rhamnose, arabinose, xylose, mannose, glucose, galactose and galactose acid with α- glycosidic bonds in the molecule, EPS II was composed of rhamnose, xylose, mannose, galactose and galactose acid with α-glycosidic bonds in the molecule.