Comparative Study On The Structure-activity Relationship Of Selenium-enriched Exopolysaccharide Produced By Pseudomonas PT-8

Selenium(Se)is a necessary trace element of human beings.Organic selenium can be better absorbed and has less toxicity compared with inorganic.The structure of Se-EPS differs from other ordinary polysaccharides as it contains a special bond between selenium atom and oxygen atom.Se-EPS has many physiological functions,such as resisting heavy metal poisoning and reactive oxygen injury.Nowadays,the selenylation biotransformation to enriched-selenium exopolysaccharides becomes popular in research of enriched-selenium exopolysaccharides.Pseudomonas PT-8 can produce large amounts of exopolysaccharides.Se-EPS containing mycelium of Pseudomonas PT-8 could be obtained by bios transformation.The mycelium was extracted by evaporation concentration and centrifugation.Then residual protein and pigment were removed from Se-EPS.The purified enriched-selenium exopolysaccharides was loaded on a column of anion-exchange(DEAE-52),gel-permeation chromatography(Sephadex G-100)and HPLC methods.And the activity and structure of enriched-selenium exopolysaccharides was investigated.The main results were shown as follows:Preparation of Enriched-Selenium ExopolysaccharideThe growth curve and Se-EPS yield were monitored to investigate the time which selenium added and the concentration of Na2SeO3.Se-added time 6th was chosen as the ideal time of adding selenite and 20?g/mL Na2SeO3 was chose as optimal concentration of selenium added in the medium.The maximum Se-EPS level was 7.18g/L.Structural Analysis of Enriched-Selenium ExopolysaccharideThe purified exopolysaccharide was concentrated,dialyzed and lyophilized,loaded on a column of anion-exchange(DEAE-52)and gel-permeation chromatography(Sephadex G-100).Finally compound obtained was named Se-SPS-2.The ultraviolet spectrum showed that Se-EPS had not been absorbed at 260nm and 280nm,and it meaned that there was no proteins and nuclear acids in Se-EPS.The structural characteristics was analysed by FTIR?HPLC and GC methods.The atom Se of Se-EPS may exist in chemical band Se=O or Se-O-C by infrared spectrum.The GC results showed Se-EPS was made up of rhamnose,arabinose,mannose,glucose,galactose.Its molecular weight is about 3.54kDa.And EPS was made up of rhamnose,arabinose,xylose,mannose,glucose and galactose.Its molecular weight was about 19.18kDa.Study on the Antioxidant Activity of Enriched-Selenium ExopolysaccharidesIn vitro antioxidant activity of Se-EPS and EPS were studied,and compared with the EPS and Vc.The results showed that,both of them showed strong scavenging hydroxyl free radicals,superoxide anion free radicals and had certain DPPH free radical scavenging and reducing power.The antioxidant effect of Se-EPS was better than that of EPS.In vivo antioxidant activity of Se-EPS and EPS were studied,the catalase activity(CAT),superoxide dismutase(SOD)and malondialdehyde(MDA)of EPS and Se-EPS in the blood and liver of mice were studied.Compare with EPS,Se-EPS(0.1 mg/g)of activities of superoxide dismutase(SOD)and catalase activity(CAT)of mice blood and liver were 24.25±1.1b U/mL and 90.42±6.97 cU/mL,CAT were 41.93±1.2 b,c and 15.49±0.84 d U/mL higer than EPS,and malonaldehyde(MDA)level was 1.27 ± 0.71 b U/mL and 2.3 8±0.01 aU/mL lower than EPS.