Microwave-assisted recovery of monomeric sugars from an acidic steam treated wood hydrolysate

Fractionation of components from bio-refinery wastes streams is complicated by the presence of both oligomer and lignin fractions. Microwave-assisted acid hydrolysis was used in this study to convert oligomer sugars in an industrial prehydrolysis liquor (PHL) to monomeric sugars. A total of 19.6 g/L monomeric sugars was obtained at a combined severity factor (CSF) of 3.2. Furthermore, it was found that xylan linked to lignin in a lignin-carbohydrate complex (LCC) could be liberated, resulting in lignin with a relatively low dispersity (3.12) and average molecular weight (1718 g/mol) that has high commercial value in the phenol–formaldehyde resin industry. This study presents for the first time a relatively inexpensive method for recovery of 100% of available sugars in the PHL without apparent loss in monomeric sugar as well as 50% removal of lignin as a valuable by-product. Application of this method can significantly improve the economic sustainability of forest-based biorefineries.