Structural features and bioremediation activity of an exopolysaccharide produced by a strain of Enterobacter ludwigii isolated in the Chernobyl exclusion zone

摘要

The bacterium Enterobacter ludwigii Ez-185-17, member of the family Enterobacteriaceae, was isolated from the root nodules of plants harvested in the nuclear power region of Chernobyl. Under batch culture conditions, the bacteria produce a high-molecular-mass exopolysaccharide (EPS). After purification, the structure of this EPS was determined using a combinatory approach including monosaccharide composition (GC-FID, HPAEC-PAD) and branching structure determination (GC-MS), as well as 1D/2D NMR (~1H, ~(13)C) and ES1-MS (HR, MS/MS) studies of oligosaccharides obtained from mild acid hydrolysis. The EPS was found to be a charged hexasaccharide with a repeating unit composed of D-galactose, D-glucose, L-fucose, D-glucuronic acid (2:1:2:1) and substituted with acyl and pyruvyl groups. The metal-binding properties of the exopolysaccharide were then investigated, and the results seem to indicate that the EPS decreased Cd sequestration in flax seeds.