Visualization of Gellan Network Formation in Different Ionic Environment

Abstract

Gellan gum is a bacterial polysaccharide with a negatively charged carboxyl ion in its monomer. It forms thermo-reversible gel due to the formation of a biopolymer network in an aqueous medium under suitable conditions, and its properties depend on the type of necessary cations to form a gel. In this study, the Atomic Force Microscopy (AFM) technique has been used to elucidate cation types effect on gellan network formation. AFM images were obtained for gellan gel samples prepared without and with adding salts of monovalent, divalent, and trivalent cations. It was found that gellan gel with monovalent ion did not show any fiber-like network. Instead, it showed a network formed by the association of globular objects. While with divalent ion, the presence of fiber-like objects was seen, and the network was formed due to the crosslinking of these fibers. The mixture of fibrous and globular structures is realized for the sample with added trivalent ion; however, the fibers are thicker than the gellan gel sample with divalent cations.