Structural analysis of the O-polysaccharide of the lipopolysaccharide from Azospirillum brasilense Jm6B2 containing 3-O-methyl-d-rhamnose (d-acofriose)

Two types of neutral O-polysaccharides were obtained by mild acid degradation of the lipopolysaccharide isolated by phenol–water extraction from the asymbiotic diazotrophic rhizobacterium Azospirillum brasilense Jm6B2. The following structure of the major O-polysaccharide was established by composition and methylation (ethylation) analyses, Smith degradation, and 1D and 2D 1H and 13C NMR spectroscopy:Figure optionsDownload full-size imageDownload as PowerPoint slidewhere a non-stoichiometric (∼60%) 3-O-methylation of d-rhamnose is indicated by italics.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Polysaccharides were isolated from the Azospirillum brasilense lipopolysaccharide. ► The major polysaccharide was studied by chemical methods and NMR spectroscopy. ► It was found to contain l-fucose, d-xylose and partially 3-O-methylated d-rhamnose. ► A branched trisaccharide-repeat structure of the polysaccharide was established.