Controlled Production of Exopolysaccharides from Enterobacter A47 as a Function of Carbon Source with Demonstration of Their Film and Emulsifying Abilities

The bacterium Enterobacter A47 has demonstrated the ability to synthesise distinct exopolysaccharides (EPS) as a function of the substrate used. The culture's performance was evaluated in experiments using either glucose or xylose, as single carbon sources, and compared with the substrate (glycerol) used in previous studies. The highest EPS production (13.23 g L-1) was obtained in the glucose fed assay, with a volumetric productivity of 3.38 g L-1 day(-1). The use of xylose resulted in lower productivity (1.39 g L-1 day(-1)). The synthesised polymers have the same main sugar monomers (fucose, glucose, galactose and glucuronic acid), but their relative proportion varied with the substrate used. The acyl groups' content and composition were also affected by the substrate used. The polymers produced from glycerol (EPS-s) and glucose (EPS-g) had identical shear-thinning behaviour and good emulsion-stabilising capacity and their films had similar mechanical and water vapour properties. However, the emulsions stabilised with EPS-g were less stable and destabilised within short periods of time or when subjected to heat and freezing/thawing procedures. On the other hand, the polymer produced from xylose had little emulsion-stabilising capacity and lower apparent viscosity than EPS-s and EPS-g, but its films were considerably more elastic.