Physical Characterization and Structure Elucidation of Exopolysaccharide from Marine Halotolerant Bacterium Enterobacter cloacae VHP-34

Abstract

An exopolysaccharide (EPS)-producing bacterium, Enterobacter cloacae VHP-34, was isolated from a coastal area of Umargam, Gujarat. Water-soluble EPS produced by Enterobacter cloacae VHP-34 was recovered with the organic solvent acetone and then purified. Carbohydrate and protein content were measured by the phenol sulphuric method and the Folin-Lowry method, Carbohydrate and protein content were 40% and 0.002%, respectively. Acid hydrolysis was done to check the monosaccharide linkage within the EPS polymer. Strong acids like HCl and trifluoroacetic acid (TFA) were used to hydrolyze the EPS. Filtered hydrolysate was used to determine monosaccharide by thin layer, paper and HPLC techniques. It was found that the repeating unit of EPS consisted of glucose and galactose as main monosaccharide components. Purified EPS was checked for functional groups and for structural elucidation by FTIR and NMR. SEM was done to check porous structure of EPS of Enterobacter cloacae VHP-34. Based on the results of NMR and FTIR, the obtained EPS structure has monosaccharide fragments with backbones of α-D-Glcp (1 → 4)-α-D-Glcp-(1 → 6)-α-D-Galp, respectively.