Organosolv fractionation of spruce bark using ethanol-water mixtures: Towards a novel bio-refinery concept

The aim of this study was to assess the effect of hot water extraction followed by organosolv pretreatment on the enzymatic hydrolysability of spruce bark biomass. To this end, samples were pretreated at five different temperatures in the presence or not of acid catalyst. The cellulose content of pretreated biomass reached 49.6% w/w. During the enzymatic hydrolysis trials with 3% w/w dry solids, the final hydrolysis yield reached up to 70.1%, which corresponded to the release of 7.8 g/L of glucose. Whereas, the final hydrolysis yield obtained during the high-gravity enzymatic hydrolysis reached up to 43.5%. The concentration of released glucose was in range of 33.3 - 40.0 g/L with a hemicellulose sugars in a range of 5.5 - 6.6 g/L. These values are suitable for downstream bioconversion processes and represent a significant improvement over existing steam pretreatment methods.