Macromolecular features of lignin, hemicellulose and cellulose fractions from biphasic organosolv fractionation of diverse biomasses: A comparative study

Abstract

Understanding lignocellulosic biomass (LB) fractionation is crucial for integrated valorization pathways. Eucalyptus (EW), pine (PW), hazelnut shells (HS) and vine pruning (VP) were selected as representative LB for “onestep” fractionation in biphasic media of water and 1-butanol or 1-pentanol by microwave heating. Owing to the limited water solubility of these alcohols, the reaction media was constituted by an aqueous phase (hemicellulose-derived products), an organic phase (mainly lignin) and a solid (mainly cellulose). Equivalent operational conditions enabled the evaluation of LB types and solvents based on phase composition and yields. EW exhibited the highest fractionation efficiency and high cellulose recoveries, and almost complete hemicellulose solubilization were consistently achieved in processed solids. 1-pentanol systems yielded higher recoveries of hemicellulose-derived saccharides in the aqueous phase, compared to 1-butanol. Oppositely, lower delignification was observed for LB in 1-pentanol systems, highlighting the solvent’s role. Lignins extracted with 1-pentanol preserved a higher proportion of β-O-4 interunit linkages and lower molecular weights compared with 1-butanol. Consequently, phenylcoumaran and resinol interunit linkages are present in higher abundance in 1-butanol lignins. This comparative study highlights the role of solvent-feedstock interactions in determining the recovery and features of cellulose, hemicellulose and lignin, contributing to a rational design of integrated biorefinery strategies.