Physicocehmical and rheological properties of a novel emulsifier, EPS-R, produced by the marine bacterium Hahella chejuensis

Abstract

The rheological properties of an exopolysaccharide, EPS-R, produced by the marine bacterium Hahella chejuensis strain 96CJ10356 were investigated. The E24 of 0.5% EPS-R was 89.2%, which was higher than that observed in commercial polysaccharides such as xanthan gum (67.8%), gellan gum (2.01%) or sodium alginate (1.02%). Glucose and galactose are the main sugars in EPS-R, with a molar ratio of ~1:6.8, xylose and ribose are minor sugar components. The average molecular mass, as determined by gel filtration chromatography, was 2.2 x 103 KDa. The intrinsic viscosities of EPS-R were calculated to be 16.5 and 15.9 dl/g using the Huggins and Kraemer equations, respectively, with a 2.3 dl/g overlap. In terms of rigidity, the conformation of EPS-R was similar to that of caboxymethyl cellulose (5.0 x 10-2). The rheological behavior of EPS？R dispersion indicated that the formation of a structure intermediate between that of a random-coil polysaccharide and a weak gel. The aqueous dispersion of EPS-R at concentrations ranging from 0.25% to 1.0% (w/w) showed a marked shear-thinning property in accordance with Power-law behavior. In aqueous dispersions of 1.0% EPS-R, the consistency index (K) and flow behavior index (n) were 1,410 and 0.73, respectively. EPS-R was stable to pH and salts.