Efficient separation of uncondensed lignin and high-quality cellulose from bamboo using reactive deep eutectic solvents for versatile valorization

Abstract

The complete valorization of lignocellulosic biomass is pivotal to realizing the economic viability and environmental sustainability of next-generation biorefineries. Herein, we developed a sustainable and highly selective fractionation strategy for bamboo using a glyoxylic acid-mediated deep eutectic solvent (DES) composed of tetrabutylammonium bromide and glyoxylic acid monohydrate (TBAB-GA). Treatment with the DES at 130 °C efficiently removed 79.62% of lignin, yielding carboxyl-enriched lignin while retaining 84.33% of cellulose in the solid residue. Notably, the incorporation of 30 wt% water allowed the process to be conducted at a reduced temperature (110 °C) while further enhancing the delignification efficiency from 60.76% to 85.94%. Critically, the extracted lignin exhibited an exceptionally high content of β-O-4 linkages (34.51/100Ar; 77.46% retention), indicating minimal structural condensation. This well-preserved β-O-4 content directly enabled efficient catalytic hydrogenolysis, affording aromatic monomers in a high yield of 25.45%. Leveraging the intact biopolymers, we further fabricated uniform cellulose nanofibers (CNFs) and lignin nanoparticles (LNPs), which were subsequently incorporated into alginate-based composite gel beads. These beads demonstrated an excellent protein adsorption capacity (1283 mg g⁻¹) and pronounced selectivity toward positively charged proteins, highlighting their potential for sustainable bioseparation technologies. This work establishes a mild, efficient, and fully integrated DES-based platform that enables the concurrent production of high-purity cellulose and structurally intact lignin from raw biomass, thereby advancing the paradigm of holistic lignocellulose valorization in alignment with green chemistry principles.