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

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Jivkova, Desislava | Sathiyanarayanan, Ganesan | Harir, Mourad | Hertkorn, Norbert | Schmitt-Kopplin, Philippe | Sanhaji, Ghislain | Fochesato, Sylvain | Berthomieu, Catherine | Heyraud, Alain | Achouak, Wafa | Santaella, Catherine | Heulin, Thierry

Edité par CCSD ; MDPI -

International audience. 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.

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