Adsorption of Cu2+ by exopolysaccharide from Rhodococcus sp. HX-2

Abstract:

[Background] At present, the physicochemical properties of exopolysaccharide (EPS) produced by microorganisms and their application in heavy metal adsorption have been widely concerned. [Objective] The physicochemical properties of exopolysaccharide produced by Rhodococcus sp. HX-2 was studied and the adsorption of heavy metals by exopolysaccharide was investigated. [Methods] The crude exopolysaccharide was purified by ion exchange and gel chromatography. Sugar content was measured by phenol-sulfuric acid method. Protein content was determined by using the Bradford kit. Lipid content was measured by methanol extraction method. Monosaccharide composition was analyzed by high performance liquid chromatography (HPLC). The surface morphology was observed by scanning electron microscopy (SEM). The adsorption effect of exopolysaccharide on heavy metals was studied by isothermal adsorption model and kinetic model. [Results] The total sugar content, protein content and lipid content of the EPS-G-1 produced by HX-2 were 78.43%, 8.31% and 8.22%, respectively. After purification, the monosaccharide of exopolysaccharide was composed of glucose, mannose, galactose, glucuronic acid and fucose; the mass ratio was 27.31:26.67:24.83:15.85:4.80, respectively. The maximum adsorption capacity of exopolysaccharide produced by HX-2 to Cu2+ was 144.93 mg/g by isothermal adsorption model fitting. [Conclusion] The exopolysaccharide produced by HX-2 has favourable adsorption effect on Cu2+ in water and can be used for the treatment of heavy metal ions in industrial wastewater.

Key words:Rhodococcus sp., Exopolysaccharide, Adsorption, Cu2+