title: Structure determination of the exopolysaccharide produced by Lactobacillus rhamnosus strains RW-9595M and R.
abstract: Exopolysaccharides (EPSs) were isolated and purified from Lactobacillus rhamnosus strains RW-9595M, which has been shown to possess cytokine-stimulating activity, and R grown under various fermentation conditions (carbon source, incubation temperature and duration). Identical (1)H NMR spectra were obtained in all cases. Molecular masses were determined by gel permeation chromatography. The primary structure was elucidated using chemical and spectroscopic techniques. Organic acid, monosaccharide and absolute configuration analyses gave the following composition: pyruvate, 1; D-glucose, 2; D-galactose, 1; and l-rhamnose, 4. Methylation analysis indicated the presence of three residues of 3-linked rhamnose, and one residue each of 2,3-linked rhamnose, 2-linked glucose, 3-linked glucose and 4,6-linked galactose. The EPS was submitted to periodate oxidation followed by borohydride reduction. Monosaccharide analysis of the resulting polysaccharide gave the new composition: rhamnose, 4; and glucose, 1. Methylation analysis confirmed the loss of the 2-linked glucose and 4,6-linked galactose residues. On the basis of one- and two-dimensional (1)H and (13)C NMR data, the structure of the native EPS was consistent with the following heptasaccharide repeating unit: [3Rha alpha-3Glc beta-3[Gal4,6(R)Py alpha-2]Rha alpha-3Rha alpha-3Rha alpha-2Glc alpha-](n) where Rha corresponds to rhamnose (6-deoxymannose) and Py corresponds to pyruvate acetal. Complete (1)H and (13)C assignments are reported for the native and the corresponding pyruvate-hydrolysed polysaccharide. Electrospray MS and MS/MS data are given for the oligosaccharide produced by Smith degradation.
authors.affiliation: Centre de recherche et de développement sur les aliments, Agriculture et Agroalimentaire Canada, 3600 boulevard Casavant Ouest, Saint-Hyacinthe, Québec, Canada J2S 8E3. vancalsteren@em.agr.ca
authors.forename: Marie-Rose
authors.initials: MR
authors.lastname: Van Calsteren
authors.forename: Corinne
authors.initials: C
authors.lastname: Pau-Roblot
authors.forename: André
authors.initials: A
authors.lastname: Bégin
authors.forename: Denis
authors.initials: D
authors.lastname: Roy
mesh_terms: D002240:Carbohydrate Sequence; D005285:Fermentation; D019344:Lactic Acid / Q000378:metabolism; D007778:Lactobacillus / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008745:Methylation; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000737:chemistry* / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011773:Pyruvates / Q000378:metabolism; D013045:Species Specificity; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D011134:Polysaccharides; D011773:Pyruvates; D019344:Lactic Acid