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

A (1→3)-β-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 β-D-Glucan was a (1→3)(1→2)-β-D-Glucan and at room temperature formed three-dimensional networks by entanglements between strands, as does scleroglucan. However, (1→3)(1→2)-β-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)-β-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.This study was supported by grants AGL2009-12998-C03 and AGL2012-40084 from the Spanish Ministry of Science and Innovation, and IT335-10 from the Basque Government. Ana Isabel Puertas acknowledges the “Gobierno Vasco, Dpto. Agricultura, Pesca y Alimentación” for the fellowship