Isolation and characterization of extracellular polymeric substances from micro-algae Dunaliella salina under salt stress

Extracellular polymeric substances (EPSs), produced by Dunaliella salina strain, increase concomitantly with salt concentration and maximum (944 mg/l) were obtained at 5 M NaCl, whereas minimum (56 mg/l) at 0.5 M salinity. Emulsifying activity was measured in terms of strength to retain the emulsion and comparatively 85.76% retention was observed at 0.5 M salinity thereafter it intends to decline. The FT-IR-spectra reveal characteristic functional groups N-H stretching, asymmetrical C-H stretching vibration of aliphatic CH2-group, C-C stretching of aromatic, C-N stretch of aliphatic amine, N-H wag of primary amine and C-X stretch of alkyl-halides with a stretching of C-O-C, C-O corresponding to the presence of carbohydrates. The FT-IR-spectra substantiated the presence of primary amine-group, aromatic-compound, halide-group, aliphatic alkyl-group and polysaccharides. Four monosaccharides (glucose, galactose, fructose and xylose) were also detected by HPLC analysis. Production of EPSs may allow further exploration of D. salina as potential EPSs producer and make it as a promising candidate for biotechnological and industrial exploitation. (C) 2009 Elsevier Ltd. All rights reserved.