Synergistic valorization of lignocellulose via integrated GVL pretreatment and in-situ dual-functional aldehyde modification

Lignin condensation during biomass pretreatment generates recalcitrant structures that limit both enzymatic saccharification and lignin valorization. Addressing this challenge requires green strategies that simultaneously suppress condensation and enhance lignin reactivity. Herein, we report a γ-valerolactone (GVL) pretreatment incorporating in-situ lignin modification with terephthalaldehyde (TALD) to achieve dual control of lignin structure and functionality. The TALD-assisted process achieved a delignification ratio of 92.9 % and increased the enzymatic hydrolysis yield from 21.6 % to 79.8 % relative to GVL alone. Spectroscopic analyses (2D HSQC, 1 H, and 31 P NMR) revealed incorporation of aldehyde moieties (3.5 mmol/g lignin) and suppression of condensation linkages leading to the occurrence of a depolymerization. The modified lignin was further utilized to fabricate polyvinyl alcohol (PVA) composite films, where acetalization between TALD lignin and PVA imparted a 40.0 MPa increase in tensile strength over neat PVA. This work presents a sustainable, dual-function pretreatment that integrates biomass fractionation with lignin functionalization, advancing closed-loop lignocellulose utilization in green biorefineries.