Production, Partial Purification and Some Bio-physicochemical Properties of EPS Produced by<i>Halomonas xianhensis</i>SUR308 Isolated from a Saltern Environment

Abstract

AbstractA moderately halophilic bacterium, Halomonas SUR308, an efficient extracellular polymeric substance (EPS) producing strain was isolated from a multi-pond solar saltern of Odisha, India. The strain was identified as Halomonas xianhensis SUR308 (Genbank Accession No. KJ933394) based on 99 % similarity of 16S rRNA gene sequences of H. xianhensis. Kinetics of growth revealed that the isolate produced 2.56 g/L of EPS during mid-stationary phase when grown under continuous shaking (120 rpm). Chemical analysis of the partially purified SUR308-EPS has been shown to contain 97 % neutral sugar but no protein and uronic acid. Aqueous solution of EPS was highly viscous and displayed pseudoplastic and thixotropic behavior. It was also able to emulsify several hydrophobic substrates like oils and hydrocarbons efficiently. The scavenging effect of SUR308-EPS was correlated well with increasing concentrations and showed about 73 % DPPH radical scavenging at a concentration of 1 mg/ml. Effect of the EPS on human hepatocyte cells revealed no significant cytotoxic effect.Key words: Halomonas xianhensissolar salternsmoderately halophilic bacteriumextracellular polymeric substancesneutral sugarDPPH radical scavengingcytotoxicitypseudoplastic AcknowledgementThis study was financially supported by grants from University Grants Commission, India (Sanction No. F.14-2(SC)/2008 (SA-III), 31 March, 2009) under the scheme of Rajiv Gandhi National Fellowship. The authors are grateful to Dr. Dipankar Chattopadhyay, Department of Polymer Science and Technology and Dr. B. Chaubey, Department of Botany, University of Culcutta for rheological and cytotoxicity tests of the EPS respectively.