Interactions between polysaccharides in aqueous solution: Development of an innovative methodology to characterize them at the molecular level
Abstract
Xanthan (X) is a bacterial polysaccharide composed of a main chain of glucose units and a trisaccharide lateral chain which can be chemically modulated according to fermentation conditions. Depending of their vegetal origin, galactomannans such as Locust Bean Gum (LBG) or Guar Gum (GG), also present a chemical variability and their Mannose/Galactose ratios (M/G) may vary from 3-4 to around 1.6. These two types of polysaccharides were selected for our study because of the synergy they exhibit when they are mixed in specific conditions. This phenomenon has been widely studied at the macroscopic scale but hardly at
the molecular scale. To clarify the role of each molecular interaction (dipole-dipole, H-bonds, hydrophobic interactions, etc.) in the synergy, we developed a methodology based on fluorescence spectroscopy. Specific fluorescent probes were selected for their ability to sense the local development of molecular interactions. The methodology was also used to monitor the kinetic of these polysaccharide-polysaccharide interactions starting from a totally disordered system. Our results would reveal the first connection between macroscopic properties of the system and the molecular interactions since we observed structuration phenomena at both macroscopic, through rheological measurements, and molecular scales.