Supramolecular Structure and Renaturation of a (1 -> 3)-beta-D-Glucan Compared with Curdlan and Scleroglucan

A (1 -> 3)-beta-D-Glucan produced by Lactobacillus suebicus CUPV221 strain was investigated by tapping mode atomic force microscopy (TM-AFM), to compare its supramolecular structure and conformation with two commercial polysaccharides: curdlan and scleroglucan. It was found that the beta-D-Glucan was a (1 -> 3)(1 -> 2)-beta-D-Glucan and at room temperature formed three-dimensional networks by entanglements between strands, as does scleroglucan. However, (1 -> 3)(1 -> 2)-beta-D-Glucan strands seemed to be more stiff than those of scleroglucan. It was also observed that curdlan samples deposited from 5 mM NaOH aqueous solution showed supermolecular assemblies, recognized in the literature as micelles, which are controlled by hydrophobic hydration. The (1 -> 3)(1 -> 2)-beta-D-Glucan in alkaline aqueous solutions produced different supramolecular structures depending on pH, and at 0.4 M NaOH (pH 13.16), denaturation took place. After neutralizing the alkaline solution with HCl, the formation of short linear, circular, and hairpin structures was observed.