Structural details of the Polyelectrolytic Exopolysaccharide (APE), the stabilizing component of the Acinetobacter venetianus RAG-1 emulsan complex

Emulsan is a polysaccharide complex, secreted from Acinetobacter venetianus RAG-1, that has been studied extensively for its ability to effectively stabilize oil-in-water emulsions. In previous research, the active emulsion stabilizing component of the emulsan complex was isolated and termed Acinetobacter Polyelectrolytic Exopolysaccharide (APE). In the research presented here, both native and O-deacetylated APE were studied by H-1 and C-13 NMR spectroscopy, including 1D H-1 and C-13 and 2D ge-DQF COSY, TOCSY, NOESY, and ge-HSQC experiments. The native polysaccharide was found to contain 6-O-acetyl-2-acetamido-2-deoxy-alpha-D-galactopyranose, 2-acetamido-2-deoxy-alpha-D-galactopyranosyluronic acid, and 2-acetamido-4-(3-hydroxybutyramido)-2,4,6-trideoxy-alpha-D-glucopyranose residues. The sequence of the linear trisaccharide repeating unit of the polysaccharide APE was determined to be -> 4)-alpha-D-GalpNAc-6-OAc-(1 -> 4)-alpha-D-GalpNAcA-(1 -> 3)-alpha-D-QuipNAc4NHb-(1 ->. (C)2011 Elsevier Ltd. All rights reserved.