Characterization of extracellular polysaccharides fromNostoc flagelliforme cells in liquid suspension culture

Abstract

Nostoc flagelliforme cells were studied with regard to the physico-chemical characterization of the extracellular polysaccharides (EPS) secreted
in a liquid suspension culture. The hydrolyzed EPS were determined to be composed of four neutral sugars, which were glucose
(43.2%), xylose (20.6%), galactose (29.9%), and mannose (6.3%). The glucuronic acid was the only uronic acid identified in
the residue. The apparent molecular weight was estimated at 2.79×105. The Fourier transform infrared spectra showed that the EPS evidenced characteristics typical of non-sulfated polysaccharides.
The UV spectrum and Bradford reaction indicated that there were no nucleic acids and proteins in them. The thermal analysis
showed a decomposition peak at 245°C on the thermogravimetric (TG) curves. The scanning electron microscope (SEM) analysis
indicated that the EPS possessed a porous structure. The observed microstructural irregularities indicated that the polysaccharide
was a type of amorphous solid. These results showed that the EPS ofN. flagelliforme cells might be ernployed as a substitute for those normally derived from field colonies. The results of this study may prove
to be beneficial to the protection of the natural resource represented byN. flagelliforme.