The Effect Of Ecological Factors On Extraction And Metabolism Of Polysaccharide From Oocystis Borgei

Marine microalgae,in the environment of high pressure,high salt,low temperature and oligotrophic salt,contains some bioactive polysaccharides that terrestrial organisms do not have.These polysaccharides are of unique structure,unique functions and various biological activities.As a result,It has a wide application in food and medical treatment.Oocystis borgei is an industrial culturing microalgae,which is rich in polysaccharide glial cell's coat,and can be used as material for extracting microalgae polysaccharides.However,there are differences in the extraction and metabolism of Polysaccharides from different microalgae.In this experiment,O.borgei was used as the research Object,and the effects of ecological factors on the yield and physicochemical properties of polysaccharides were studied after optimized the extraction conditions of polysaccharides.The main results are as follows: 1.The optimization of extraction conditions of polysaccharide from O.borgeiSingle factor experimental results:The temperature and concentration of sodium hydroxide and extraction time have a great influence on Oocystis polysaccharide extraction rate(p<0.05).The extraction efficiency of oocysts polysaccharide was higher at the extraction temperature of 50 degrees,the sodium hydroxide solution was 0.275 mol/L,and the extraction time was 20~100 min.Response surface experimental results: The effect of various factors on the extraction rate: Sodium hydroxide concentration > extraction temperature > extraction time.The optimum extraction conditions for extracting polysaccharides from hot alkali leaching: The extraction temperature is 58.5,the concentration of Na OH was 0.305 mol/L,the extraction time was 68 min,the extraction rate of polysaccharide was 11.86% which was close to the predicted value of 11.93%.2.Effects of nutritional factors on yield of polysaccharide from O.borgeiNitrogen had a significant effect on the polysaccharide content of O.borgei(P < 0.05).When the nitrogen concentration is 0 mg/L,the accumulation of polysaccharide is 32.82 pg/cell,which is an ideal result.When the nitrogen concentration was 80 mg/L,the specific growth rate and the chlorophyll-a content is higher.The content of polysaccharide is 22.32 pg/cell,which is only 0.62 times higher than that when the nitrogen concentration is 0 mg/L.Effect of phosphorus to oocystis polysaccharide content was significant(p<0.05).When the phosphorus concentration is 8 mg/L,the content of microalgae polysaccharides,higher,is 23.4 pg/cell.When the concentration of phosphorus is 32~128 mg/L,the specific growth rate and the chlorophyll-a content is higher.When the phosphorus concentration is 128 mg/L,the polysaccharide content is only 12.69 pg/cell,and only 0.54 times than that when the phosphorus concentration is 8 mg/L.Effect of iron to Oocystis polysaccharide content is significant(p<0.05).When the iron concentration is 0 mg/L,the content of polysaccharides in microalgae reaches the maximum,is 26.51 pg/cell.At the iron concentration of 16 mg/L,the specific growth rate is higher,while the content of polysaccharides is 17.39 pg/cell,which is only 0.66 times than that at the iron concentration of 0 mg/L.Effect of carbon to Oocystis polysaccharide content is significant(p<0.05).When the carbon concentration was 0.1 g/L,the content of polysaccharides was significantly higher than that of other groups,reaching the maximum 21.13 pg/cell.When the carbon concentration is 1.6 g/L,the specific growth rate and the chlorophyll-a content is higher,while the content of polysaccharides is 15.24 pg/cell,which is only 0.72 times than that when the carbon concentration was 0.1 g/L.Orthogonal experimental results show that,the influence of different factors on Oocystis polysaccharide content is in the order as follow: Iron concentration > carbon concentration > nitrogen concentration > phosphorus concentration.The optimal combination of these factors: The concentration of Na NO3 is 10 mg/L,KH2PO4 2 mg/L,Fe C6H5O7·5H2O 0.5 mg/L,Na HCO? 0.4 g/L.The influence of different factors on the growth of O.borgei is in the order as follow: Carbon concentration > nitrogen concentration > iron concentration.The optimal combination of these factors: the concentration of Na NO3 is 80 mg/L,Fe C6H5O7·5H2O 32mg/L,Na HCO? 3.2g/L.The orthogonal optimum value of the polysaccharide content in this experiment was 32.03 pg/cell.Under the optimum growth conditions,the content of polysaccharides in microalgae was 14.29 pg/cell,which was only 0.45 times higher than that of the highest polysaccharides.Under the condition of f/2 growth,the content of polysaccharide was 18.19 pg/cell,which was 0.57 times of the highest polysaccharide content.Oocystis polysaccharide production and growth have different need for nitrogen,phosphorus,iron and carbon.3.Effects of different nitrogen and phosphorus concentration to the physicochemical properties of O.borgeiGPC analysis results: Under the conditions of nitrogen and phosphorus restriction(OBP-0),phosphorus restriction(OBP-1)and nitrogen restriction(OBP-2),The molecular weight of polysaccharides in oocyst was 6551 KDa,344 KDa and 1510 KDa.Analysis results of high performance liquid chromatography: After oocystis polysaccharide hydrolysis,the percentage of monosaccharide was in turn: rhamnose 13.15~15.16%,mannose 7.03~8.76%,glucose 5.74~8.7%,xylose 2.57~4.10%,fucose 1.19~1.91% and galactose 1.09~1.35%.and the sugar of Arabia has not been detected.The mass percentage of mannose,rhamnose and glucose in group OBP-2 were higher than those in group OBP-1.However,the mass percentage of galactose,xylose and fucose in group OBP-1 is higher than that in OBP-2.Infrared spectrum analysis results: The glycosidic bonds of OBP-0,OBP-1 and OBP-2 are all belong to beta glucan groups.They have a characteristic absorption peak of the sulphuric acid group,as a result,are mucopolysaccharides for sulphuric acid.Near 1259cm-1,the peak of OBP-1 sulfate group is stronger than those of OBP-0 and OBP-2.The content of sulphuric acid group in OBP-1 group was higher than that of OBP-0 and OBP-2.Nitrogen and phosphorus can lead to changes in polysaccharide's molecular weight,monosaccharide composition and functional groups.