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

•Strain OLL1073R-1 produces a high-molecular-weight exopolysaccharide.•The repeating unit is a branched pentasaccharide composed of Glc and Gal.•The structure is compared to that of other strains of the same species.

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–}n. The structure is compared to that of exopolysaccharides produced by other Lactobacillus bulgaricus strains.

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