HAL Id: hal-01984297
https://hal.archives-ouvertes.fr/hal-01984297
Submitted on 16 Jan 2019
HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Structure of hyperbranched heteropolysaccharides of Acacia gum exudates: From speroidal to prolate
ellipsoidal conformation
Michael Nigen, Lizeth Lopez-Torres, Pascale Williams, Thierry Doco, Christian Sanchez
To cite this version:
Michael Nigen, Lizeth Lopez-Torres, Pascale Williams, Thierry Doco, Christian Sanchez. Structure of hyperbranched heteropolysaccharides of Acacia gum exudates: From speroidal to prolate ellipsoidal conformation. 16. Food Colloids Conference, 2016, Wageningen, Netherlands. 2016, Food Colloids Conference. �hal-01984297�
A. senegal
A. seyal
Structure of hyperbranched heteropolysaccharides of Acacia gum exudates:
From spheroidal to prolate ellipsoidal conformation
Michaël NIGEN
1, Lizeth LOPEZ-TORRES
1,
Pascale
WILLIAMS
2, Thierry DOCO
2and Christian SANCHEZ
11 UMR IATE, UM-INRA-CIRAD-SupAgro, 2 place Pierre Viala, 34060 Montpellier, France 2 UMR SPO, UM-INRA-SupAgro, 2 place Pierre Viala, 34060 Montpellier, France
Introduction
Materials & Methods
Results
Conclusions
Acacia gum (GA) is an edible dried gummy exudate obtained from the trunk and branches of Acacia senegal and Acacia seyal trees. GA macromolecules are highly branched hetero-polysaccharides belonging to the arabinogalactan-protein (AGP) family. GA can be defined as a continuum of molecular species differing by their protein to sugar ratio, molar mass, charges and hydrophobicity index. A. senegal and seyal gums especially differ by their chemical composition (sugar composition and protein content) as well as their polysaccharide degree of branching. They are composed of galactose, arabinose, rhamnose, glucuronic acid and a small amount of protein (0.5-3%). In this work, the conformational properties of Acacia senegal and Acacia seyal macromolecules was characterized.
HPSEC experiments were performed using a Shimadzu HPLC system coupled online to a MALS DAWN HELEOS II, a viscometer VISCOSTAR II and a refractive index T-rEX detectors (Wyatt). GA macromolecules were separated on a set of Shodex columns composed of one OHPAK SB-G pre-column followed by four OHPAK SB pre-columns in series (803 HQ, 804 HQ, 805 HQ and 806 HQ). GA macromolecules were eluted with 0.1 M LiNO3 solution containing 0.02% NaN3 at a constant flow rate of 1 ml.min-1 and 30°C.
Fig 1. Molar mass (Mw) distribution of A.
senegal (black) and A. seyal (gray) gums.
Fig 2. Rg conformation plot for A. senegal (black) and A. seyal (gray) gums.
Fig 3. Mark-Houwink-Sakurada plot for A.
senegal (black) and A. seyal (gray) gums.
Fig 4 Radius of gyration (Rg) as a function of hydrodynamic radius (Rh) for A. senegal (black) and A. seyal (gray) gums.
A. senegal A. seyal A. senegal A. seyal A. senegal A. seyal
- A. seyal macromolecules were more structured and compact than A. senegal ones presenting the lowest intrinsic viscosity.
- The conformation of A. seyal macromolecules varied from spheres to oblate ellipsoids while A.
senegal macromolecules varied from oblate ellipsoids to more anisotropic conformations such
as for instance prolate ellipsoids (Fig. 4).
- A. seyal macromolecules displayed higher Mw than A. senegal ones for a same hydrodynamic volume suggesting a more compact structure (Fig. 1).
- A. seyal macromolecules adopted more compact conformation in water than A. senegal ones (Fig. 2 and 3).
- For A. senegal, macromolecules with Mw on the intermediate range displayed larger anisotropy or smaller chain density than in the low and high Mw range (Fig. 3).
- For A. senegal and seyal gums, νg values decreased when increasing the Mw suggesting that larger macromolecules were more compact or/and less anisotropic than smaller ones (Fig. 2).
- A. senegal and seyal gums were a continuum of macromolecules with Mw ranging from 107 to 105 g.mol-1 and 4×107 to 105 g.mol-1, respectively (Fig. 1).
