The size and shape of three water-soluble, non-ionic polysaccharides produced by lactic acid bacteria: A comparative study

• Three non-ionic polysaccharides produced by lactic acid bacteria studied by aqueous multi-detector SEC.
• RG-M and [η]-M relationships indicate random coil behaviour in all cases.
• Estimated persistence lengths in the range 5–10 nm.
• Lowest persistence length (5 nm) attributed to 1,6-linkage in the main chain.

Three water-soluble, non-ionic extracellular polysaccharides (EPS) obtained from lactic acid bacteria (S. thermophilus THS, L. helveticus K16 and S. thermophilus ST1) were subjected to a comparative study by means of multidetector size-exclusion chromatography, providing distributions and averages of molar masses, radii of gyration and intrinsic viscosities. All polysaccharides displayed random coil character. Further analysis of the data reveals differences in chain stiffness and extension that could be well correlated to structural features. The calculated persistence lengths ranged from 5 to 10 nm and fall within the range typical for many single-stranded bacterial or plant polysaccharides. The ST1 polysaccharide had the highest molar mass but the lowest persistence length, which is attributed to the presence of the flexible (1 → 6)-linkage in the main chain.