STRUCTURAL CHARACTERIZATION OF THE EXOCELLULAR POLYSACCHARIDE PRODUCED BY STREPTOCOCCUS-THERMOPHILUS OR-901

The exocellular polysaccharide of Streptococcus thermophilus OR 901, i solated from partially deproteinised whey, is a heteropolymer of D-gal actopyranose and L-rhamnopyranose residues in the molar ratio 5:2. The structure was established by methylation analysis and 1D and 2D NMR s pectroscopy of the native polysaccharide, in combination with characte risation of oligosaccharide fragments, obtained by partial acid hydrol ysis, using methylation analysis and ID H-1 NMR spectroscopy. The poly saccharide has a branched heptasaccharide repeating unit with the foll owing structure: beta-D-Gal(p)-(1-6)-beta-D-Gal(p)-(1-4) 1-->3)-alpha- L-Rha(p)-(1-->2)alpha-L-Rha(p)-(1-->. (C) 1997 Elsevier Science Ltd.