Characterization and antioxidant activity of exopolysaccharide secreted by nostoc carneum

The physico-chemical characterization of the cyanobacterium Nostoc carneum extracellular polysaccharide (EPS) was studied. Two sugars moieties glucose (105.5 mg g^-1 EPS) and xylose (215.2 mg g^-1 EPS) were involved in the polysaccharide composition as well as the presence of sulfate, uronic acids and protein. The in vitro antioxidant assays (reducing power and DPPH) showed that N. carneum EPS possess antioxidant activity. Fourier Transformed Infrared (FT-IR) spectra of EPS showed a specific absorbance of O-H and –NH stretching, asymmetrical-symmetrical C-H stretching, Presence of sulfur containing functional groups and carboxylic acids. The thermal gravimetric and differential scanning calorimetric analyses confirmed that polysaccharide thermal stability was around 237°C. Nostoc carneum exopolymer showed pseudoplastic non-Newtonian fluid behavior in the aqueous solutions as well as increasing viscosity with increasing concentration.