Novel control of fractionation–depolymerization for rapid dissociation of lignin-associated xylan: toward complete lignocellulosic biomass valorization in lignin-first biorefinery

Abstract

Harvesting sustainable aromatic chemicals from lignocellulosic biomass is a critical part of a bio-based economy. Ideal whole-biomass utilization strategies have been developed for lignin valorization via solvent fractionation followed by catalytic hydrogenolysis. However, the limited understanding of the lignin/hemicellulose structure and the lack of a control strategy for the side reactions have seriously hindered the applicability of these novel biorefinery techniques. To overcome these challenges, this study integrated various solution- and solid-state nuclear magnetic resonance (NMR) techniques with 66 biorefinery and hydrogenolysis experiments, aiming to construct a novel Pretreatment Depolymerization Factor (PDF) model for simulating the hydrolysis kinetics of hemicelluloses, including xylans in different conformations and arabinose residues. The PDF model successfully simulated the delignification dynamics, lignin integrities, and monolignol yields with 90.9% accuracy, leading to a new discovery of an unexplored C_β–C_γ lignin bond cleavage initiated by C_γ–OH activation. The monolignol yield increased by over 30% through a PDF-assisted sequencing batch fractionation strategy without requiring additional solvent, energy, or chemicals, and exceeded the theoretical monomer yield attainable by batch pretreatment. This effective preservation of both carbohydrates and aromatic products highlights the economic and environmental benefits of smart fractionation control in complete lignocellulose utilization.