Structure determination of an exopolysaccharide from an alkaliphilic bacterium closely related to Bacillus spp.

An exopolysaccharide obtained from an alkaliphilic bacterium closely related to Bacillus spp. was found to contain D-galactopyranuronic acid (GalpA), 2,4-diacetamido-2,4,6-trideoxy-D-glucopyranose (QuipNAc4NAc), 2-acetamido-2-deoxy D-mannopyranuronic acid (ManpNAcA) and one uncommon unit of D-galactopyranuronic acid with the carboxyl group amide-linked to glycine [GalpA(Gly)]. The polysaccharide was studied by one-dimensional and two-dimensional H-1-NMR and C-13-NMR spectroscopy both on native polysaccharide and on monosaccharides and oligosaccharides obtained from methanolysis and from anhydrous HF solvolysis, The following linear structure of the repeating unit was established: -->3)-alpha-D-GalpA(Gly)-( 1-->4)-beta-D-ManpNAcA-(1-->4)-alpha-D-GalpA-(1-->3)-alpha-D-QuipNAc4NAc-(1-->. A preliminary phylogenetic assignment for the bacterium is also reported.