Research Of Extracellular Polymer Produced By Bacillus Amyloliquefaciens SQ-2

With the continuous development of sugar engineering,people have realized that exopolysaccharides have important properties and have broad application prospects in many fields.In this paper,exopolysaccharide isolated from commercial tofu were studied.The strain was identified as amyloid bacillus SQ-2 by morphological observation,physiological and biochemical characteristics identification,16S r DNA sequence alignment and management gene sequence analysis.Through the single factor optimization test,the optimum fermentation medium was determined as sodium chloride 10g/L,peptone 10g/L,yeast powder 5g/Land sucrose 20g/L.the optimum culture conditions were p H 8.5,culture time 42h and inoculation amount 4%.The optimized yield was 642%EPS-1 was prepared from fermentation broth by centrifugation,ethanol precipitation,proteinization and freeze-drying.The crude extracellular polysaccharide Eps-2 was purified by DEAE-cellulose ion exchange column and Sephadex G100 gel filtration column.The extracellular polysaccharide produced by Bacillus amylosum was analyzed by gel permeation chromatography and the molecular weight was 45.51 KDa.The contents of total carbohydrate,protein and lipid were 81.50%,6.41%and 5.33%respectively.L’analyse CLHP a montréque le Polysaccharide extracellulaireétait composéde88,35%de glucose et de 7,53%de Glucosamine.HPLC analysis showed that the extracellular polysaccharide was composed of88.35%glucose and 7.53%glucosamine;UV scanning shows that it does not contain or contains little protein and nucleic acid,and the purity is high;The infrared chromatogram shows that the extracellular polysaccharide contains functional groups such as acetylamino group,carbonyl group and sulfate group.NMR showed that the polysaccharide was a glucan with side chain structure.Thermogravimetric analysis determined that the degradation temperature was 140.43℃.SEM and AFM showed that the surface of extracellular polysaccharide was smooth,with fine pore structure,chain shape and circular structure.SEM and AFM showed that the surface of extracellular polysaccharide was smooth,with fine pore structure,chain shape and circular structure.The extracellular polysaccharide has certain antioxidant properties.With the increase of concentration,its antioxidant capacity is also increasing,and the concentration is positively correlated with its antioxidant capacity.When the concentration of extracellular polysaccharide was 10 mg/ml,the free radical scavenging rate of 1,1-diphenyl-2-trinitrophenylhydrazyl（DPPH）was 81%,the hydroxyl radical scavenging rate was 31%,and the H₂O₂ scavenging rate was 72%,indicating that this kind of extracellular polysaccharide can be used as a better natural antioxidant.Experiments show that it also has good water solubility and water holding capacity.Cell experiments showed that the exopolysaccharide had almost no cytotoxicity on normal cell L929,and inhibited the proliferation of breast cancer cell MCF-7,human lung cancer cell A549 and cervical cancer cell Hela.Exopolysaccharide with selective cytotoxicity could be regarded as a promising cancer treatment drug.