Towards a wheat straw biorefinery: Combination of Organosolv and Liquid Hot Water for the improved production of sugars from hemicellulose and lignin hydrolysis

Abstract

One major challenge of sustainable biorefineries relies on valorizing hemicellulose and lignin simultaneously. However, a single pretreatment will unlikely render high sugar and lignin yields. Liquid-Hot-Water (LHW) and Organosolv (OS) highlight as technologies to solubilize these components (in different proportions). A combined pretreatment may hydrolyze lignin and hemicellulose into different fractions, with higher overall yield and leaving cellulose available for further processing. Hence, it must be determined the stages' order to maximize hemicellulose/lignin hydrolysis. We performed both configurations (OS → LHW and LHW → OS) using wheat straw and determined sugar and lignin concentration and the dissolved lignin's molar-mass distributions. Both configurations reached similar sugar concentrations (~12 g/L), but LHW → OS reached a 1.6-times higher lignin extraction (7 to 11 g/L in the OS-stage). The extracted lignin molar mass in LHW → OS had lower polydispersity and molar-mass averages, favoring colloidal particle production. These results bring us closer to a sustainable biorefinery valorizing the different feedstock fractions.