Structural studies of the exopolysaccharide consisting of a nonasaccharide repeating unit isolated from Lactobacillus rhamnosus KL37B

A novel structure of exopolysaccharide from the lactic acid bacteria (LAB) Lactobacillus rhamnosus KL37B, from the human intestinal flora, is described. During the structural investigation of the exopolysaccharide it was found that the repeating unit is a nonasaccharide, which is the largest repeating unit found in LAB exopolysaccharides to date. The polysaccharide material was prepared by TCA extraction of a bacterial cell mass, purified by anion-exchange and gel permeation chromatography and characterized using chemical and enzymatic methods. On the basis of monosaccharide and methylation analysis and also 1D and 2D H-1 and C-13 NMR spectroscopy the exopolysaccharide was shown to be composed of the following nonasaccharide repeating unit: -> 4)-alpha-D-Galp-(1 -> 6)-alpha-D-Galp-(1 -> 6)-beta-D-Galp-(1 -> 6)-beta-D-Galf-(1 -> 3)-beta-D-Glcp-(1 -> 6)-beta-D-Galf-(1 -> 6)-beta-D-Galf-(1 -> 3 up arrow 1 alpha-D-Glcp-(1 -> 2)-beta-D-Glcp The physicochemical cell surface study and adhesive properties indicated distinct surface properties of Lactobacillus rhamnosus strain KL37B with high adhesive abilities to Caco-2 cells, hydrophobicity and slime production, in comparison to other Lactobacillus strains used as controls. (C) 2011 Elsevier Ltd. All rights reserved.