Present study reports the biodegradation of chlorpyrifos by Synechocystis sp. Biodegradation of the insecticide by the cyanobacterium is significant as it can be biologically removed from the environment. The cyanobacterium may be used for bioremediation of chlorpyrifos-contaminated soils.

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.

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Exopolysaccharides of the cyanobacterium Oscillatoria formosa have been physico-chemically characterized and kinetics of their production studied. The organism produced 334.8 lg EPS per ml culture in 24 days with the maximum rate of production obtained during initial days of growth. HPLC analysis of the EPS hydrolysate revealed that besides three unidentified sugars, EPS contained ribose, mannose, and galacturonic acid. FT-IR spectrum of EPS revealed the presence of methyl, carboxyl and C-N groups. Elemental analysis indicated the presence of 4.7% nitrogen in EPS. The organism produced 75.6% more EPS when incubated at 35°C compared to cultures at 28°C. Under varied nutritional conditions, though the growth of the organism was less yet it produced enhanced amounts of EPS. Aqueous dispersions of EPS showed nonNewtonian, pseudoplastic behaviour. The viscosity of the aqueous solution of EPS was quite stable over a wide range of pH and temperature but it was observed to be affected by CaCl 2.

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