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References to other databases: GTC:G66584GU, GlycomeDB:25365
Structural formula & atomic coordinates
Sweet-II 3D model
Show glycosyltransferases

Rheological studies have confirmed that the bacterial polysaccharide P2, a genetically modified variant of the Acetobacter xylinum polysaccharide acetan, undergoes synergistic gelation with either of the plant polysaccharides carob or konjac mannan. X-ray fibre diffraction data shows that P2 can form a 5-fold helical structure of pitch 4.7nm and an axial rise per disaccharide repeat of 0.92nm. Optical rotation data demonstrate that P2 undergoes a coil-helix transition in solution and that deacylation enhances the stability of the helical structure in solution. Studies made on mixtures prepared at different temperatures and ionic strengths suggest that denaturation of the P2 helix favours interaction and gelation. Deacetylation of P2 enhances gelation. X-ray diffraction data for oriented fibres prepared from deacetylated P2-konjac mannan mixed films reveal a 6-fold helical structure of pitch 5.54nm with an axial rise per disaccharide repeat also of 0.92nm. This mixed helix provides direct evidence for binding between the two polysaccharides. P2 contains two sites of acetylation: one on the backbone and one on the sidechain. The former site of acetylation inhibits helix formation for P2. It is suggested that this site of acetylation also inhibits formation of the mixed helix, explaining the enhanced gelation of mixtures on deacetylation.

Bacterial polysaccharide, Rheology, Konjac mannan, Mixtures, Carob

NCBI PubMed ID: 15337451
Journal NLM ID: 0043535
Publisher: Elsevier
Correspondence: geoff.brownsey@bbsrc.ac.uk
Institutions: Institute of Food Research, Food Material Science, Norwich Research Park, Colney, Norwich, UK
Methods: X-ray, optical rotation measurement

Acetan is a bacterial polysaccharide produced by Acetobacter xylinum NRRL B42. Chemical mutagenesis of A.xylinum allowed selection of a mutant strain which produced a new polysaccharide, CR1/4. 2D NMR methods have been used to assign the 1H and 13C spectra of the two polysaccharides and to determine that CR1/4 has the structure shown below. The total number of O-acetyl groups is slightly less than two per repeating unit. [formula: see text] The pentasaccharide side chain of acetan is truncated to a disaccharide unit in CR1/4, but the structures are otherwise identical. In particular, the degree of acetylation is about the same and the O-acetyl groups are located at the same position in both polysaccharides.

NMR, structure, Bacterial, strain, polysaccharide, mutant, Bacterial polysaccharide, Acetobacter, extracellular, acetan, Acetobacter xylinum

NCBI PubMed ID: 7780996
Journal NLM ID: 0043535
Publisher: Elsevier
Institutions: Institute of Food Research, Norwich Laboratory, Norwich Research Park, Colney, Norwich, NR4 7UA United Kingdom
Methods: NMR-2D, NMR, de-O-acetylation

The usage of polysaccharides as biodegradable polymers is of growing interest in the context of a sustainable and ecofriendly economy. For this, the production of exopolysaccharides (EPS) by Gluconacetobacter sp. was investigated. Glycerol as carbon source revealed to be beneficial compared to glucose. In addition, pure glycerol could be substituted by a crude glycerol waste stream from biodiesel production. Systematic analysis of the peptone and phosphate concentrations in glycerol-based media indicated a strong effect of peptone. Optimized parameters resulted in a titer of 25.4 ± 2.4 g/L EPS with a productivity of 0.46 ± 0.04 g*(L*h)-1. With decreasing peptone, a variation in the monomer ratios was observed. An accompanying change in molecular size distribution indicated the production of two different polysaccharides. Intensified analysis revealed the main polysaccharide to be composed of glucose (Glc), galactose (Gal), mannose (Man) and glucuronic acid (GlcA), and the minor polysaccharide of Gal, Man, ribose (Rib).

exopolysaccharide, optimization

NCBI PubMed ID: 34823788
Publication DOI: 10.1016/j.carbpol.2021.118769
Journal NLM ID: 8307156
Publisher: Elsevier
Correspondence: V. Sieber
Institutions: Chair of Chemistry of Biogenic Resources, Technical University of Munich, Campus for Biotechnology and Sustainability, 94315 Straubing, Germany, Fraunhofer IGB, Branch BioCat, 94315 Straubing, Germany, Catalysis Research Center, Technical University of Munich, 85748 Garching, Germany, The University of Queensland, School of Chemistry and Molecular Biosciences, 68 Cooper Road, St. Lucia 4072, Australia
Methods: sugar analysis, GPC, fermentation, media composition, preculture preparation, UHPLC-UV-ESI-MS/MS, crude glycerol analysis

References to other databases: GTC:G11877YH, GlycomeDB:16444
Structural formula & atomic coordinates
Sweet-II 3D model
Show glycosyltransferases

Journal NLM ID: 7909578
Publisher: Butterworth-Heinemann

Journal NLM ID: 7503050