Alkali-peroxide extraction of xylan from sugar cane bagasse: Characteristics and film forming capacity

Abstract

This work analyzes the main characteristics of hemicellulose alkali and peroxide/alkali extracted from sugar cane bagasse and precipitated by 1:1 ethanol/liquor ratio and studies the influence of the chemical charge on these characteristics. It also evaluates the film forming capacity of these hemicelluloses when they are combined in a polyelectrolyte complex with chitosan. Extraction conditions were determinant of the glucuronic acid to xylose ratio and arabinose to xylose ratio. The charge density of xylan, determined by polyelectrolyte titration at pH 7.0, showed a linear relation with the glucuronic acid content. Xylans with low polydispersity and acceptable molecular weight were obtained in all cases. Hemicellulose-based films (70% of xylan) without the addition of plasticizer or crosslinking agent, obtained through the controlled formation of the polyelectrolyte complexes, were flexible with acceptable mechanical properties. The film with the highest stress and strain at break (19.1 MPa and 10.7%, respectively) corresponded to hemicellulose with the highest molecular weight, extracted with the highest alkali charge and no peroxide addition.