STRUCTURAL CHARACTERIZATION OF THE EXOPOLYSACCHARIDE PRODUCED BY LACTOBACILLUS-DELBRUCKII SUBSPECIES BULGARICUS RR GROWN IN SKIMMED-MILK

The exopolysaccharide of Lactobacillus delbruckii subsp. bulgaricus rr, isolated from skimmed milk, is a heteropolymer of D-plactopyranosyl, D-glucopyranosyl, and L-rhamnopyranosyl residues in the molar ratio 5:1:1. The structure was established by linkage analysis and 1D and 2D NMR spectroscopy of the native polysaccharide, in combination with characterisation of oligosaccharide fragments, obtained by Smith degradation and partial acid hydrolysis, using methylation analysis, EIMS, and 1D and 2D H-1 NMR spectroscopy. The polysaccharide has a branched heptasaccharide repeating unit with the following structure: --> 2)-[beta-D-Galp-(1 --> 3)]-alpha-D-Galp-(1 --> 3)-beta-D-Glcp-(1 --> 3)-[beta-D-Galp-(1 --> 4)]-beta-D-Galp-(1 --> 4)-[alpha-L-Rhap-(1 --> 3)]-alpha-D-Galp-(1 -->.