产胞外多糖菌株的筛选及胞外多糖结构分析

Screening of Exopolysaccharide-producing Strains and Structural Analysis of the Exopolysaccharides

筛选产胞外多糖菌株,探究胞外多糖流变学特性,并分析其结构。从土壤中筛选产胞外多糖菌株,通过形态特征观察及16S r DNA序列鉴定菌株。使用黏度计测定不同条件下胞外多糖溶液黏度变化,研究其流变学特性。通过乙醇沉淀、Sevag法和透析分离纯化多糖,再利用气相色谱、红外光谱和核磁共振等手段分析多糖结构。结果显示,筛选到一株产胞外多糖菌株,鉴定为肠杆菌WL113(Enterobacter sp.WL113)。所产胞外多糖黏度随质量浓度升高呈指数增大,浓度为10 g/L时黏度比1 g/L时提高约33倍;该多糖对温度敏感,100℃时黏度比25℃时降低了89.8%;但此多糖在酸性、中性和弱碱性条件下黏度相对稳定,对Na^+、K^+、Mg^(2+)和Ca^(2+)等金属盐离子耐受性能良好。结构分析表明,该多糖主要由阿拉伯糖、甘露糖和葡萄糖组成,摩尔比阿拉伯糖∶甘露糖∶葡萄糖=1.63∶3.16∶2.38,含有α型和β型吡喃糖,存在糖醛酸。

This study aims to screen and identify strains producing exopolysaccharides（EPSs）,to study the rheological properties of EPSs,and to analyze the structure of EPSs. The strains producing EPSs were screened from soil,and were identified based on their morphology and 16 S r DNA gene sequencing. The viscosity changes of EPSs in different conditions were determined by viscometer to study its rheological properties. Then,GC,IR and NMR were used to analyze the structure of EPSs isolated and purified by ethanol precipitation,Sevag method and dialysis. As a result,a strain producing EPSs was identified as Enterobacter sp. WL113. The viscosity of the EPSs exponentially increased with the concentration of EPSs,i.e.,viscosity increased about 33 times when concentration of EPSs from 1 g/L to 10 g/L. The EPSs were sensitive to temperature,and viscosity decreased 89.8% when temperature from 25 ℃ to 100 ℃. The viscosity of EPSs remained relatively stable under the condition of acid,neutral and weak alkaline. The EPSs also well tolerated with metal ions such as Na^＋、K^＋、Mg^2＋ and Ca^2＋. The analysis of EPSs by GC,IR,and NMR indicated that the EPSs consisted of arabinose,mannose and glucose in a molar ratio of 1.63：3.16：2.38,also containing α-pyranose,β-pyranose and uronic acid.