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

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.