Extracellular polymeric substances (EPSs) from Dunaliella salina having antioxidant and immunostimulating activity

Abstract

D. salina is a unique unicellular, biflagellate species of genus Dunaliella which contain no cell wall in saline environments. Dunaliella is known for its growth in wide range of salt concentration where range varies from 0.05 M to 5.0 M and other stress conditions like temperature stress, light intensity stress, nutrient stress etc. Extracellular polymeri c substances are complex high molecular weight biopolymers containing main components like carbohydrates, lipids, proteins, nucleic acids etc. In present work, extracellular polymeric substances EPSs have been extracted from D. salina and its antioxidant and immunostimulating activity were studied.Further, stress conditions of phosphate (2.8mM and 7mM) and nitrate (9.8mM and 24.5mM) were given to D. salina to study its growth, EPSs production and bioactive properties. Normal growth condition of these two parameters was 1.4mM KH2PO4 and 4.9mM KNO3. Cell growth and count was found to be increased at 9.8 mM KNO3as compared to normal conditions. On the other hand phosphate (KH2PO4 ) stress resulted in decrease in cell growth and count. EPSs produced under normal conditions were checked for protein and glucose contents in it and the result confirm the presence of these two components in it. Under stress conditions, protein and carbohydrate concentrations were increased. Antioxidant effect was assessed of EPSs produced under normal conditions and it was found that these effects become more pronounced with concentrations. 1 mg/ml of EPSs (normal condition) has shown the increase in proliferation of Concanavalin A stimulated peripheral blood mononuclear cells (PBMCs). Further, 1mg/ml of EPSs extracted in all stress conditions has shown proliferative response of PBMCs indicating the immunostimulating properties of EPSs. Present results suggest that EPSs produced under normal and stress condition possess bioactive properties which may be used for therapeutic purpose.