Hemicellulose biorefineries: a review on biomass pretreatments

Biomass pretreatment (BP) plays a crucial role in a lignocellulose feedstock-based biorefinery (LCFBR) for processing of three major output streams (cellulose, hemicelluloses and lignin) into chemicals and biofuels. BP includes processing of lignocellulosic material (LCM) under aqueous, dilute acid or alkaline media to obtain a cellulosic fraction, which is then fermented to produce bioethanol. Hemicellulose is usually treated as a secondary stream due to lack of efficient fermentation of hemicellulosic sugars to ethanol. This review provides BPs assuming that hemicellulose stream should be integrated in LCFBR as a primary fraction for converting into value-added compounds other than bioethanol. Different LCM treatments are analyzed foreseeing bio-based products possible to obtain from hemicellulose path.