Determination of the structure of the exopolysaccharide produced by Lactobacillus sake 0-1

Structure of an extracellular polysaccharide produced by Lactobacillus rhamnosus strain C83

The extracellular polysaccharide produced by Lactobacillus rhamnosus strain C83 was found to be composed of D-glucose and D-galactose in a molar ratio of 2:3. The primary structure of the polysaccharide was shown by sugar analysis, methylation analysis, FABMS, partial acid hydrolysis and nuclear magnetic resonance (NMR) spectroscopy to consist of a pentasaccharide repeating unit having the following structure: -->3)-alpha-D-Glcp-(1-->2)-beta-D-Galf-(1-->6)-alpha-D-Galp-(1-->6 )-alpha-D -Glcp-(1-->3)-beta-D-Galf-(1-->

Mutational analysis of exopolysaccharide biosynthesis by Lactobacillus sakei 0-1

Lactobacillus sakei strain 0-1 produces an exopolysaccharide (EPS) consisting of glucose and rhamnose in a ratio of 3:2. As part of a biochemical and molecular analysis of the EPS biosynthetic pathway in L. sakei strain 0-1, we have isolated a random set of EPS-negative mutants. Following treatment of cells with the mutagen ethylmethane sulfonic acid, a total of 10 mutants were identified that lacked the clear ropy appearance of wild-type colonies on agar plates. Their characterization revealed that eight mutants had completely lost the ability to synthesize the normal EPS. Six of these mutants lacked activities of enzymes involved in the biosynthesis of dTDP-rhamnose, required for EPS production. Only mutant strains 12 and 20 were directly affected in EPS synthesis. Strain 12 synthesized EPS with a different sugar composition, however. Interestingly, strain 12 showed temperature-dependent EPS synthesis, with the highest amounts synthesized at 12 degrees C, and low amounts at the optimal temperature for growth (30 degrees C). Two mutants were in fact EPS-positive, producing the normal EPS, but displayed a different cell morphology (elongated cells), indicating a modification in cell wall synthesis.

The exopolysaccharides produced by Streptococcus thermophilus Rs and Sts have the same repeating unit but differ in viscosity of their milk cultures

The polysaccharides produced by Streptococcus thermophilus Rs and Sts in skimmed milk consist of D-Gal and L-Rha in a molar ratio of 5:2. Linkage analysis and 1D/2D NMR (1H and 13C) studies revealed that both polysaccharides have the same branched heptasaccharide repeating unit: [formula: see text] Remarkably, the two strains differ in their effects on the viscosity of stirred milk cultures. The milk culture of S. thermophilus Rs is non-ropy and affords 135 mg/L polysaccharide with an average molecular mass of 2.6 x 10(3) kDa. In contrast, the milk culture of S. thermophilus Sts is ropy and produces 127 mg/L polysaccharide with an average molecular mass of 3.7 x 10(3) kDa. Permeability measurements of non-stirred milk cultures of both strains suggest that both strains have a similar effect on the protein-polysaccharide network. Therefore, the only clear difference between both strains, which may cause the difference in ropiness of the milk cultures, is the difference in molecular mass of the polysaccharide.

Acceptor specificity of cellobiose phosphorylase from Cellvibrio gilvus: synthesis of three branched trisaccharides

Cellobiose phosphorylase from Cellvibrio gilvus was examined for its acceptor specificity in the synthetic reaction with glucose-1-phosphate, using substrates in which the C-6 substituent of D-Glc had been altered. A range of disaccharides were also tested for acceptor specificity but only those with (1-->6)-linkages were successful acceptors. Melibiose, gentiobiose, isomaltose and also the monosaccharide glucuronamide were found to react with cellobiose phosphorylase and glucose-1-phosphate giving beta-D-Glcp-(1-->4)-[alpha-D-Galp-(1-->6)]-D-Glcp, beta-D-Glcp-(1-->4)-[beta-D-Glcp-(1-->6)]-D-Glcp, beta-D-Glcp-(1-->4)-[alpha-D-Glcp-(1-->6)]-D-Glcp and beta-D-Glcp-(1-->4)-D-GlcUNp, respectively. These products were purified using a range of chromatographic methods and characterised by NMR and FAB-MS. This is the first time cellobiose phosphorylase has been shown to synthesise trisaccharides.

Structural characterization of the exocellular polysaccharides produced by Streptococcus thermophilus SFi39 and SFi12

We investigated the structures of the exopolysaccharides (EPSs) produced by Streptococcus thermophilus SFi39 and SFi12. Both polymers were found to have molecular masses of greater than 2 x 10(6) Da. The SFi39 EPS consisted of D-glucose and D-galactose in a molar ratio of 1:1, whereas the SFi12 EPS was composed of D-galactose, L-rhamnose, and D-glucose in a molar ratio of 3:2:1. Methylation analysis of and nuclear magnetic resonance spectra recorded from the native polysaccharide, as well as oligosaccharides released by partial acid hydrolysis, allowed the complete structural determination of the SFi39 EPS, which consists of the following tetrasaccharide repeating unit: [formula: see text] Similar spectra recorded only from the native polysaccharide were sufficient to allow the structural determination of the SFi12 EPS, which consists of the following hexasaccharide repeating unit: [formula: see text] This study shows that the texturizing properties of different S. thermophilus ropy strains are based on the production of EPSs exhibiting chemical similarities but structural differences.

Structural characterisation of the exocellular polysaccharide produced by Streptococcus thermophilus OR 901

The exocellular polysaccharide of Streptococcus thermophilus OR 901, isolated from partially deproteinised whey, is a heteropolymer of D-galactopyranose and L-rhamnopyranose residues in the molar ratio 5:2. The structure was established by methylation analysis and 1D and 2D NMR spectroscopy of the native polysaccharide, in combination with characterisation of oligosaccharide fragments, obtained by partial acid hydrolysis, using methylation analysis and 1D 1H NMR spectroscopy. The polysaccharide has a branched heptasaccharide repeating unit with the following structure: [sequence: see text]

Predicting helical structures of the exopolysaccharide produced by Lactobacillus sake 0- 1

The viscous exopolysaccharide (EPS) produced by Lactobacillus sake 0- 1 is a high molecular mass polymer (Mm 6 x 10(6) Da) consisting of pentasaccharide repeating units with a composition of D-glucose, L-rhamnose, and sn-glycerol 3-phosphate in molar ratios of 3:2:1. One of the rhamnose residues in the repeating unit is partially 2-O-acetylated. The O-deacetylated, deglycerophosphorylated EPS has been investigated by molecular mechanics calculations. A complete conformational analysis of each of the constituent disaccharide fragments has been performed using the flexible residue approach with the MM3(92) force field. Furthermore, using the same force field, CICADA analyses were accomplished on hexa- and octasaccharide substructure of the polysaccharide. Based on these analyses, insight was obtained into nine conformational minima for the polysaccharide. The low energy conformations found by CICADA were extrapolated to regular polysaccharide structures using a polysaccharide builder program. The generated helices exhibit either 2-fold or 3- or 4-fold right-handed chiralities, and in each case the helices are highly extended.

Structural characterization of the exopolysaccharide produced by Lactobacillus acidophilus LMG9433

The exopolysaccharide produced by Lactobacillus acidophilus LMG9433 in a semi-defined medium was found to be a charged heteropolymer, with a composition of D-glucose, D-galactose, D-glucuronic acid, and 2-acetamido-2-deoxy-D-glucose in molar ratios of 2:1:1:1. By means of methylation analysis, uronic acid degradation, de-N-acetylation/deamination, partial acid hydrolysis, and 1D/2D NMR studies the polysaccharide was demonstrated to consist of repeating units with the following structure: [Table: see text]

Structural studies of the exopolysaccharide produced by Lactobacillus paracasei 34-1

The exopolysaccharide produced by Lactobacillus paracasei 34-1 in a semi-defined medium was found to be a heteropolymer, composed of D-galactose, 2-acetamido-2-deoxy-D-galactose, and sn-glycerol 3-phosphate in molar ratios of 3:1:1. By means of deglycerophosphorylation, methylation analysis, and 1D/2D NMR studies (1H, 13C, and 31P) the polysaccharide was shown to consist of repeating units with the following structure: [formula: see text].

Identification and characterization of the eps (Exopolysaccharide) gene cluster from Streptococcus thermophilus Sfi6

We report the identification and characterization of the eps gene cluster of Streptococcus thermophilus Sfi6 required for exopolysaccharide (EPS) synthesis. This report is the first genetic work concerning EPS production in a food microorganism. The EPS secreted by this strain consists of the following tetrasaccharide repeating unit:-->3)-beta-D-Galp-(1-->3)-[alpha-D-Galp-(1-->6)]-beta-D- D-Galp-(1-->3)-alpha-D-Galp-D-GalpNAc-(1-->. The genetic locus The genetic locus was identified by Tn916 mutagenesis in combination with a plate assay to identify Eps mutants. Sequence analysis of the gene region, which was obtained from subclones of a genomic library of Sfi6, revealed a 15.25-kb region encoding 15 open reading frames. EPS expression in the non-EPS-producing heterologous host, Lactococcus lactis MG1363, showed that within the 15.25-kb region, a region with a size of 14.52 kb encoding the 13 genes epsA to epsM was capable of directing EPS synthesis and secretion in this host. Homology searches of the predicted proteins in the Swiss-Prot database revealed high homology (40 to 68% identity) for epsA, B, C, D, and E and the genes involved in capsule synthesis in Streptococcus pneumoniae and Streptococcus agalactiae. Moderate to low homology (37 to 18% identity) was detected for epsB, D, F, and H and the genes involved in capsule synthesis in Staphylococcus aureus for epsC, D, and E and the genes involved in exopolysaccharide I (EPSI) synthesis in Rhizobium meliloti for epsC to epsJ and the genes involved in lipopolysaccharide synthesis in members of the Enterobacteriaceae, and finally for eps K and lipB of Neisseria meningitidis. Genes (epsJ, epsL, and epsM) for which the predicted proteins showed little or no homology with proteins in the Swiss-Prot database were shown to be involved in EPS synthesis by single-crossover gene disruption experiments.

The structure of the exopolysaccharide produced by Lactobacillus helveticus 766

The exopolysaccharide produced by Lactobacillus helveticus 766 in skimmed milk was found to be composed of D-glucose and D-galactose in a molar ratio of 2:1. Linkage analysis and 1D/2D NMR studies (1H and 13C) performed on the native polysaccharide, and on oligosaccharides obtained from a partial acid hydrolysate, showed the polysaccharide to consist of hexasaccharide repeating units with the following structure: [formula: see text]