| Marine microorganisms produce extracellular polysaccharide with novel structure,unique functions,and rich in activity,is an important resource to development of polysaccharide marine functional foods.Changes of fermentation carbon source may affect the microbial composition of extracellular polysaccharide and lead to differences in their physical properties and biological activities.In this paper,three fermentation production of marine Pseudomonas PT-8 as the research object,the synthesis,purification,physical and chemical properties and structural characteristics of them was systemic studied.The structure-activity relationship of active polysaccharides was discussed.The results of the study are as follows:Marine Pseudomonas PT-8 as sugar producing strains,using different carbon sources(glucose,sucrose,maltose)for the fermentation of extracellular polysaccharide.The obtained three microbial extracellular polysaccharide(EPSs,EPSG,EPSM)production rate were:6.98,6.35 and 5.93g/L respectively.The physical and chemical properties of extracellular polysaccharide was Analysis shows that three types of EPS mainly contains carbohydrates,also contains a certain amount of protein,sugar,uronic acid and sulfate.Through the ultraviolet spectrum analysis showed that does not contain proteins and nucleic acids;Infrared spectrum analysis are present the characteristic peak of polysaccharide.But waveform,the characteristic absorption band,wave intensity has some differences.Through high performance liquid chromatography(HPLC)analysis,three kinds of polysaccharide was prove with high purity,and their molecular weight are 7.3kDa,17.8kDa and 19.2kDa.GC-MS analysis showed that EPSs-2-1,EPSG-2-1 and EPSM-2-1 molar ratio of monosaccharide composition respectively:Rha:Ara:Xyl:Man:Glc:Gal=1.62:1:1.31:1.37:3.29:1.34;Fuc:Xyl:Man:Glc:Gal =3.28:3.23:1:3.18:2.09;Fuc:Man:Glc:Gal =6.71:1:3.4:3.96.Scanning electron microscopy(SEM)shows the solid-state morphology difference of extracellular polysaccharide,showed filamentous,flaky and flocculent structure respectively.By measuring physical characteristics of EPSs,EPSG and EPSM,we found three kinds of polysaccharides showed non Newton fluid behavior.When the solution concentration is 1%,the viscosity of EPSM 80.15mPa·S,their values significantly higher than that of EPSs and EPSG;and EPSM emulsification and emulsion stability is the best;EPSs,EPSG,EPSM respectively in 8mg/mL,6mg/mL and 4mg/mL to achieve the best flocculation rate.When the EPSM is in the pH 8 and Ca2+ as flocculation of kaolin coagulant conditions yield reached the maximum of 86.21%.In vitro antioxidant activity of EPSs,EPSG,EPSM were studied,and compared with the positive control Vc.The results show that,both of them showed strong scavenging hydroxyl free radical,superoxide anion free radicals and has certain DPPH free radical scavenging and reducing power.Antioxidant capacity was EPSs>EPSG>EPSM.The results show that,the carbon source changes in the composition of polysaccharides of influence of Pseudomonas PT-8 extracellular,and caused the difference of the physical properties and physiological activities. |
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