Escherichia coli K5胞外多糖硫酸酯衍生物的制备及其体外抗氧化活性研究

对Escherichia coliK5菌株进行发酵培养,发酵液上清经超滤、醇沉、Sevage法脱蛋白、透析冻干,再经DEAE琼脂糖柱、G75葡聚糖柱分离纯化后得到K5多糖（K5）。以三氧化硫吡啶为硫酸酯化剂,对K5多糖N位进行了硫酸酯化,制备了K5多糖的硫酸酯衍生物（NS-K5）,二糖分析结果显示,N位硫酸酯化率达到57%。并对硫酸酯化前后的K5多糖的抗氧化性能进行了研究,结果显示,一定浓度范围内,NS-K5多糖还原力较K5高,当K5和NS-K5浓度达到1mg/mL时,对羟基自由基的清除率分别达到17.7%、25.6%,对DPPH自由基的清除率分别达到26.1%、45%。实验结果表明,NS-K5的抗氧化活性要高于K5。 

Preparation and antioxidant activities of a sulfated derivative of exopolysaccharide from Escherichia coli K5

Escherichia coli K5 strain was cultivated by fermentation,the supernatant was treated by ultrafiltration,exopolysaccharide(EPS) was extracted by ethanol precipitation,and then purified by Sevage method,dialysis,freeze-dried,DEAE-Sepharose and Sephadex G-75 column,finally high-purity K5 polysaccharide(K5) was obtained. N site of the K5 polysaccharide was chemically sulfated by Sulfur trioxide pyridine complex,NS-K5 polysaccharide(NS-K5) was prepared,and disaccharide analysis revealed that N-sulfation rate was up to 57%. The antioxidant capacity of K5 polysaccharideand N-sulfated K5 polysaccharide was investigated,the results showed that:within a certain concentration range,the reducing activity of NS-K5 was powerful over K5,when the concentration of K5 and NS-K5 was up to 1mg/mL,the hydroxyl radical scavenging rates were 17.7%,25.6%,and DPPH radical scavenging rates were 26.1%,45%,respectively. The result indicated that NS-K5 showed stronger antioxidant activity than K5.