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

The neutral exopolysaccharide (NPS) of Lactobacillus delbrueckii subsp. bulgaricus strain OLL1073R-1 was purified and characterized. The molecular mass was 5.0 x 10(6) 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, H-1 and C-13 nuclear magnetic resonance, and mass spectrometry of the NPS or of its specifically modified products allowed determining the repeating unit sequence: {2) Glc(alpha 1-3)Glc(beta 1-3)[Gal(beta 1-4)]Gal(beta 1-4)Gal(alpha 1-}(n). The structure is compared to that of exopolysaccharides produced by other Lactobacillus bulgaricus strains. (C) 2015 Published by Elsevier Ltd.