Physicochemical characterization and emulsifying properties of a novel exopolysaccharide produced by haloarchaeon Haloferax mucosum.

The physicochemical characterization and emulsifying functional properties of a novel exopolysaccharide (EPS) produced by haloarchaea Haloferax mucosum (DSM 27191) were investigated. This biopolymer has a high molecular weight of 152 kDa and important protein content of 10%. Different culture media compositions were investigated taking the ATCC 2185 medium as a base and supplementing with varying concentrations of yeast extract and glucose or sucrose as carbon sources to produce the EPS in a liquid medium. The highest EPS production (7.15 ± 0.44 g/L) was obtained at 96 h. EPS aqueous dispersions showed a non-Newtonian rheological behavior which was well fitted to the Cross equation. The EPS (at 0.32% w/w) was capable of stabilizing water-in-oil emulsions with different nonpolar solvents, including n-hexane, kerosene, chloroform, castor oil and mineral oil. EPS retained its emulsifying activity after to be incubated for one hour in a wide range of temperatures (25, 40, 70 and 100 °C), pH (4, 6.5, 7 and 12) and NaCl concentrations (0, 2.0 and 4.0 M). The viscoelastic behavior and stability of hexane-in-water emulsion were examined through oscillatory shear measurements.