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

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

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。

Escherichia coil 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 lmg/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.