Study On The Extracellular Polysaccharide Produced By Paenibacillus Polymyxa HY96-2

Paenibacillus polymyxa HY96-2 is a biocontrol strain which was separated from the tomato rhizosphere by author's laboratory.A series of microbial pesticide was successfully developeded with HY96-2 as the active ingredient.For the functions and structure of the polysaccharide,and the rules of polysaccharide produced by HY96-2 in the culture process were not clear,this paper firstly studied the thermal protective effect on Bacillus marinus and the suspensibility improvement on preparation by polysaccharide produced by HY96-2,then explored the purification and the structure of the polysaccharide;Finally,the rules of the polysaccharide produced by HY96-2 and the optimization for producing polysaccharide were carried out.The extracellular polysaccharide from HY96-2 has a significant thermal protective effect on the Bacillus marinus B-9987.Under the same conditions,the addition of 0.5%polysaccharide can improve the survival rate of B-9987 cells and spores,the increased rates were 14.06%and 15.68%,respecctively.Before spraying,the addition of 0.5%polysaccharide can also improve the bacteria population in the preparation of Bacillus marinus,and the increase ratio was 30.43%.The suspensibility of the preparation can be improved by adding 25%polysaccharide into the uncrushed and crushed preparation of Bacillus marinus,and the increased rates were 3.21%and 18.79%,respectively.Before spraying,the addition of 0.5%polysaccharide can also improve the suspensibility of the preparation,and the increased rate was 5.81%.By ethanol precipitation,Sevag method to remove protein,dialysis and DEAE-52 anion exchange column chromatography,the extracellular polysaccharide of HY96-2 has been purified.The purity of fraction B is 91.39%.The molecular weight of fraction B is 1.22 × 106 daltons which was measured by GPC,GC analysis.The monosaccharide composition of fraction B was analyzed,it contains 5 glycosylations:rhamnose,xylose,mannose,galactose,and glucose,the molar ratio is 2.52:0.25:1:1.61:2.24.Scaled up by 5L,500L and 5000L fermenters progressively,the production of polysaccharide reached to 6.8g/L,8.2g/L and 8.6g/L,respectively.In order to improve the production of polysaccharide,the cultivation conditions have been optimized by the single factor experiment and orthogonal experiment.The optimized conditions are as follows:2%for glucose,1%for peanut powder and the temperature is 32?.Validated with the 5L fermenter,the production of polysaccharides is 19.86g/L,which is 1.91 times higher than before.