Structure determination of the neutral exopolysaccharide produced by Lactobacillus delbrueckii subsp. bulgaricus OLL1073R-1

Abstract The neutral exopolysaccharide (NPS) of Lactobacillus delbrueckii subsp. bulgaricus strain OLL1073R-1 was purified and characterized. The molecular mass was 5.0×10⁶ g/mol. Sugar and absolute configuration analyses gave the following composition: d-Glc, 1; d-Gal, 1.5. The NPS was also submitted to periodate oxidation followed by borohydride reduction and Smith degradation. Sugar and methylation analyses, ¹H and ¹³C nuclear magnetic resonance, and mass spectrometry of the NPS or of its specifically modified products allowed determining the repeating unit sequence: {2)Glc(α1-3)Glc(β1-3)[Gal(β1-4)]Gal(β1-4)Gal(α1-}<inf>n</inf>. The structure is compared to that of exopolysaccharides produced by other Lactobacillus bulgaricus strains.