Optimization, characterization, and flow properties of exopolysaccharides produced by the cyanobacteriumLyngbya stagnina

The exopolysaccharides produced by the cyanobacterium Lyngbya stagnina have been characterized. Maximum amounts of EPS (142.4 µg EPS ml(-1) culture) were obtained during the stationary phase of growth and rate of EPS production was maximum during late phase of growth. When medium was supplemented with 85 mM NaCl, the organism produced three times more EPS compared to EPS produced by control cultures. TLC and HPLC analysis of the EPS hydrolysate revealed heteropolysaccharide nature with presence of four neutral sugars and galacturonic acid. Presence of high amounts of galacturonic acid in EPS indicated its polyanionic character. Aqueous dispersions of EPS showed non-Newtonian, pseudoplastic behavior and its viscosity was found to be quite stable with time. The viscosity data of aqueous dispersions of EPS at different temperatures (20-50 °C) were fitted into rheological models. The viscosity of EPS varied with pH, being highest at pH 10 and lowest at pH 6. Both divalent and monovalent cations caused increase in viscosity of EPS solution. The results suggest that EPS of this organism may find application in food industry.