[Purification and characterization of extracellular polysaccharides from Nostoc flagelliforme].

The extracellular polysaccharides (EPS) of N. flagelliforme were purified by DEAE anion exchange chromatography and Sephadex G100 gel filtration chromatography. And two main components named NFPS1 and NFPS2 were obtained respectively. The physico-chemical characteristics of NFPS2 were analyzed and compared with NFPS0, which was obtained from field colony of N. flagelliforme. These results showed that both of NFPS2 and NFPSO were composed of four monosaccharides: glucose, xylose, galactose and mannose. The apparent molecular weight of NFPS2 and NFPS0 was estimated to be 2.79 x 10(5), 2.26 x 10(5) respectively. They are non-sulfated polysaccharides, free of protein and nuclear acid. The thermal analysis indicated that there was a decomposition peak at 245 degrees C in thermogravimetric (TG) curves. However, the microstructure analysis showed that they had different porous structures.