紫云英根瘤菌107菌株酸性胞外多糖的分离纯化及结构分析

Isolation, Purification and Structure Analysis of Acidic Exopolysaccharide from Rhizobium astragali Strain 107

用化学沉淀法和柱层析法，分高纯化了紫云英根瘤菌野生型107菌株、胞外多糖合成缺陷型变种NA02及其回复子NA02（R'－11）产生的酸性胞外多糖（EPS）。结构组成分析表明：菌株107与NA02（R＇－11）产生的EPS糖组分均由葡萄糖、半乳糖、核糖和葡萄糖醛酸构成；而变种NA02产生的EPS只含葡萄糖、半乳糖和葡萄糖醛酸，与野生型显著不同。3个菌株的EPS均有乙酰基取代，而无其它形式的取代基。EPS的酸性来自葡萄糖醛酸。1H－NMR分析表明，野生型菌株107和回复子NA02（R＇－11）的EPS糖残基通过α和β糖苷键方式连接，而变种NA02EPS的糖链中均为α连接方式。

The acidic exopolysaccharides(EPS) of R. astragali wild type 107, itsExo-mutant NA02 and R'-plasmidtransconjugant NA02 (R'-11) wereisolated and purified by acetone precipitation and chromatography (Fig. 1).Their composition and structure werealso studied using 1H-NMR, infraredspectrum, gas choromatography, TCL(Figs. 2-4). The EPS of R. astragalicontained only a high-molecular-weightfraction of EPS, and no low-molecular-weight oligosaccharides were detected. Strain 107 and NA02(R'-11) produce identical EPS which consists ofglucose, galactose, ribose and glucuronic acid and links with a and plinkages. In contrast, the EPS secretedby mutant NA02 lacks in ribose and thesugar residues were linked by the samep linkages (Table 2). All of the EPSscontain only acetyl substitutent, andthe EPSs' acidic nature comes from theuronic acid.