Isolation and characterization of exopolysaccharides produced by the cyanobacterium Limnothrix redekei PUPCCC 116

Limnothrix redekei PUPCCC 116, a filamentous cyanobacterium, has been identified through 16S rRNA gene sequencing. Exopolysaccharides (EPS) of this organism have been isolated and characterized chemically, and its rheological properties were compared with commercial xanthan. The organism produced 304 microg EPS/ml culture in 21 days. The rate of EPS production was maximum (313 microg EPS/mg protein/day) during the initial days of growth, and it decreased to 140 microg EPS/mg protein/day during 18-21 days of growth. Chemical analysis of EPS revealed the presence of glucose/mannose, ribose, rhamnose, and uronic acid. Fourier transformed infrared spectrum of EPS further revealed the presence of methyl and carboxyl groups besides C-N groups indicating the presence of peptidyl moieties. Elemental analysis of EPS showed the presence of 4.97% N. The organism under continuous light produced 102% more EPS compared to when grown under a light/dark cycle of 14/10 h. The rheological properties of EPS were comparable with commercial xanthan gum.