Structural studies of the capsular polysaccharide produced by Leuconostoc mesenteroides ssp. cremoris PIA2.

The structure of the capsular polysaccharide (CPS) produced by Leuconostoc mesenteroides ssp. cremoris PIA2 has been determined using component analysis and NMR spectroscopy. (1)H and (13)C resonances were assigned using 2D NMR experiments, and sequential information was obtained by (1)H,(1)H-NOESY and (1)H,(13)C-HMBC experiments. The CPS consists of linear pentasaccharide repeating units with the following structure: →3)-ß-D-Galf-(1→6)-ß-D-Galf-(1→2)-ß-D-Galf-(1→6)-ß-D-Galf-(1→3)-ß-D-Galp-(1→, in which four out of the five sugar residues have the furanoid ring form, a structural entity found in bacteria but not in mammals. The analysis of the magnitude of the homonuclear three-bond coupling constants of the anomeric protons for the five-membered sugar rings indicates that the sugar residues substituted at a primary carbon atom show one kind of conformational preferences, whereas those substituted at a secondary carbon atom show another kind of conformational preferences.

Structural analysis of the exopolysaccharide produced by Streptococcus thermophilus ST1 solely by NMR spectroscopy.

The use of lactic acid bacteria in fermentation of milk results in favorable physical and rheological properties due to in situ exopolysaccharide (EPS) production. The EPS from S. thermophilus ST1 produces highly viscous aqueous solutions and its structure has been investigated by NMR spectroscopy. Notably, all aspects of the elucidation of its primary structure including component analysis and absolute configuration of the constituent monosaccharides were carried out by NMR spectroscopy. An array of techniques was utilized including, inter alia, PANSY and NOESY-HSQC TILT experiments. The EPS is composed of hexasaccharide repeating units with the following structure: --> 3)[alpha-D-Glcp-(1 --> 4)]-beta-D-Galp-(1 --> 4)-beta-D-Glcp-(1 --> 4)[beta-D-Galf-(1 --> 6)]-beta-D-Glcp-(1 --> 6)-beta-D-Glcp-(1 -->, in which the residues in square brackets are terminal groups substituting backbone sugar residues that consequently are branch-points in the repeating unit of the polymer. Thus, the EPS consists of a backbone of four sugar residues with two terminal sugar residues making up two side-chains of the repeating unit. The molecular mass of the polymer was determined using translational diffusion experiments which resulted in Mw = 62 kDa, corresponding to 64 repeating units in the EPS.

Structural studies of an exopolysaccharide produced by Streptococcus thermophilus THS.

The structure of an extracellular polysaccharide (EPS) from Streptococcus thermophilus THS has been determined. A combination of component analysis, methylation analysis and NMR spectroscopy shows that the polysaccharide is composed of pentasaccharide repeating units. Sequential information was obtained by two-dimensional (1)H,(1)H-NOESY and (1)H,(13)C-HMBC NMR experiments. NMR data indicate different mobility within the EPS with a stiffer backbone and a more flexible side-chain.

Structural studies of the exopolysaccharide produced by Lactobacillus rhamnosus strain GG (ATCC 53103).

The structure of the extracellular polysaccharide (EPS) from Lactobacillus rhamnosus strain GG has been investigated. In combination with component analysis, NMR spectroscopy shows that the polysaccharide is composed of hexasaccharide repeating units. Sequential information was obtained by two-dimensional (1)H,(1)H-NOESY, and (1)H,(13)C-HMBC NMR techniques. The structure of the repeating unit of the EPS from Lactobacillus rhamnosus strain GG was determined as: [carbohydrate structure: see text]

Antimicrobial Activity of 2-Pyrrolidone-5-Carboxylic Acid Produced by Lactic Acid Bacteria.

Thirteen Lactobacillus and five Pediococcus strains were shown to produce an antimicrobial agent, 2-pyrrolidone-5-carboxylic acid (PCA). PCA inhibited many spoilage bacteria, particularly Enterobacter cloacae 1575, Pseudomonas fluorescens KJLG, and P. putida 1560-2. The antimicrobial activity of PCA did not change at higher temperatures. However, the activity was destroyed rapidly by neutralization with ammonium hydroxide. PCA showed slightly lower antimicrobial activity than lactic acid.