(603h) Xanthan Gum Polysaccharide in Aqueous Solutions: Conformation and Dynamics

Biopolymers derived from renewable resources such as plants, seaweeds, animals, and bacterial fermentation, including xanthan gum, guar gum, dextran, and cellulosics, are versatile materials with broad applications due to their inherent physicochemical properties. [1-4] Among biopolymers, the anionic polysaccharide xanthan gum (XG) finds widespread applications in food, cosmetics, pharmaceutical, and petroleum industries. In water, xanthan gum exhibits conformational transitions from helices (characterized by rigid chains and low viscosity) to random coils (with more flexible chains and higher viscosity) in response to changes in solution pH, ionic strength, shear rate, and temperature. However, the influence of salts and temperature on the physicochemical properties of xanthan gum in aqueous solutions remains a subject of exploration. We have investigated the fundamental properties of xanthan gum in plain water and in aqueous solutions with inorganic salts or ionic liquids at varying temperatures. [4-6] We have demonstrated that as the salt valency and concentration increased, the XG coil radius decreased, illustrating the effect of shielding the intermolecular and intramolecular XG anionic charge, which leads to XG structural contraction. Increasing temperatures, however, caused chain expansion, which enhanced intermolecular interactions and counteracted the salt effect. Furthermore, we have shown the utility of fluorescence spectroscopy in providing insight into the behavior of the XG solution from the perspective of the sensitive solute molecule. [7] These findings offer valuable insights into how various factors affect the rheological properties, structural characteristics, and microenvironmental effects of XG solutions.

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