Chemical structure of an acidic polysaccharide produced by serratia piscatorum

The acidic polysaccharide of Serratia piscatorum consists of L-rhamnopyranosyl, D-galactopyranosyl, and D-galactopyranosyluronic acid residues in the molar ratio of 2:1:1. Some of the D-galactopyranosyluronic acid residues are acetylated at O-2 or O-3, or both. Smith degradation and methylation analysis indicated that the L-rhamnopyranosyl, D-galactopyranosyl, and D-galactopyranosyluronic acid residues are substituted with glycosidic linkages at O-3, O-3, and O-4, respectively. Partial acid hydrolysis of the native polysaccharide gave four acidic oligosaccharides, each of which was isolated and characterized, suggesting the following tetrasaccharide repeating unit: →3)-L-Rhap-(1→4)-D-GalAp-(1→3)-L-Rhap-(1→3)-D-Galp-(1→.