Extracting value-added products before pulping: Hemicellulosic ethanol from Eucalyptus globulus wood

Abstract

Abstract Xylose solutions have been produced from Eucalyptus globulus wood by autohydrolysis (with hot, compressed water) and post-hydrolysis (in presence of sulfuric acid). This two-stage process led to solids enriched in cellulose and lignin (suitable as a substrate for pulping) and liquors containing xylose as the major component. The liquid phase from post-hydrolysis also contained other sugars (glucose, arabinose) and acetic acid. Neutralized liquors (as obtained, or after membrane concentration), were employed (directly or after detoxification by ion exchange) as fermentation media for the production of hemicelluosic bioethanol with the yeast Pichia stipitis CECT 1922T. Under the best conditions assayed (fermentation of neutralized, concentrated and detoxified two-stage hydrolysis liquors), bioconversion took place at nearly stoichiometric yield, with a volumetric productivity of 0.37 g l-1·h-1.