Production and characterization of a novel exopolysaccharide from $Ramlibacter \tataouinensis

Desislava Jivkova (1) , Ganesan Sathiyanarayanan (1) , Mourad Harir (2, 3) , Norbert Hertkorn (2) , Philippe Schmitt-Kopplin (2, 3) , Ghislain Sanhaji (4) , Sylvain Fochesato (1, 5) , Catherine Berthomieu (6) , Alain Heyraud (7) , Wafa Achouak (1, 5) , Catherine Santaella (1, 5) , Thierry Heulin (1, 5)

1 LEMIRE - Laboratoire d'Ecologie Microbienne de la Rhizosphère et d'Environnements Extrêmes
2 BGC - Research Unit Analytical BioGeoChemistry
3 Chair of Analytical Food Chemistry
4 ARD - White Biotechnology departement, Pomacle
5 ECCOREV - Ecosystèmes continentaux et risques environnementaux
6 IPM - Interactions Protéine Métal
7 CERMAV - Centre de Recherches sur les Macromolécules Végétales

The current study examines the desiccation-resistant $Ramlibacter \tataouinensis$ TTB310$^T$ as a model organism for the production of novel exopolysaccharides and their structural features. This bacterium is able to produce dividing forms of cysts which synthesize cell-bound exopolysaccharide. Initial experiments were conducted on the enrichment of cyst biomass for exopolysaccharide production under batch-fed conditions in a pilot-scale bioreactor, with lactate as the source of carbon and energy. The optimized medium produced significant quantities of exopolysaccharide in a single growth phase, since the production of exopolysaccharide took place during the division of the cysts. The exopolysaccharide layer was extracted from the cysts using a modified trichloroacetic acid method. The biochemical characterization of purified exopolysaccharide was performed by gas chromatography, ultrahigh-resolution mass spectrometry, nuclear magnetic resonance, and Fourier-transform infrared spectrometry. The repeating unit of exopolysaccharide was a decasaccharide consisting of ribose, glucose, rhamnose, galactose, mannose, and glucuronic acid with the ratio 3:2:2:1:1:1, and additional substituents such as acetyl, succinyl, and methyl moieties were also observed as a part of the exopolysaccharide structure. This study contributes to a fundamental understanding of the novel structural features of exopolysaccharide from a dividing form of cysts, and, further, results can be used to study its rheological properties for various industrial applications.

Mots clés: $Ramlibacter\ tataouinensis$; exopolysaccharide; biosynthesis; optimization; bioreactor; characterization; GC; NMR; FT-ICR-MS; FTIR

Domaines: Biochimie [q-bio.BM]

Desislava Jivkova, Ganesan Sathiyanarayanan, Mourad Harir, Norbert Hertkorn, Philippe Schmitt-Kopplin, et al.. Production and characterization of a novel exopolysaccharide from $Ramlibacter \tataouinensis. Molecules, 2022, 27 (21), pp.7172. ⟨10.3390/molecules27217172⟩. ⟨cea-03861333⟩