Extracellular Polysaccharides of the cyanobacterium- Leptolyngbya tenuis: Structural characterization and its compositional changes during stress exposure

Economically important and widespread marine cyanobacterium Leptolyngbya tenuis produces significant amount of extraellular polysaccharidic material (EPS).This prokaryotic biopolymer has vast significance in understanding of different interesting activities like biofilm formation, bio-remediation of metal wastes etc. Biotechnology industries like food, cosmetic and medicine industries are positively influenced by this type of polymer. The ability of this polymer to change its chemical composition due to stress exposure is another fascinating feature. To understand these properties better, bound exopolysaccharides produced by cyanobacterial strain Leptolyngbya tenuis has been analysed by Gas chromatography, 2D nuclear magnetic resonance spectroscopy (NMR) and Mass spectrometry. Analysis of monosaccharidic composition of EPS was done from the biomass in control condition, as well as subjected to stress conditions like, variations in nitrate, phosphate and salinity level of the growth medium. The results indicated the presence of six sugars (fucose, galactose, glucose, mannose, rhamnose) showing glucose as predominant one in normal growth medium, but in stress exposed biomass synthesis of ‘new’ (not present in control) pentose sugar arabinose was observed and rhamnose disappeared in all stress exposed conditions.NMR studies for structure determination revealed three fractions, of which, partial structure of two were determined in this study by 2D NMR and ESI-MS analysis.