A deep eutectic solvent with a lignin stabilization and functionalization for lignocellulosic biomass pretreatment

This study synthesized a functional deep eutectic solvent (DES) using betaine and glyoxylic acid (GA) for lignocellulosic biomass pretreatment. The Betaine/GA DES pretreatment resulted a high delignification efficiency of 81.89% and xylan removal of 83.25% while preserving most of cellulose. During pretreatment, lignin was stabilized by GA, preventing its condensation and introducing carboxyl groups onto its molecular backbone. The GA stabilized lignin (GASL), with a high beta-O-4 linkage content of 62.92%, was depolymerized for phenolic monomer production with a bio-oil yield of 55.40%. Additionally, the functional lignin was used as a surfactant for GASL-based O/W emulsion (GA-O/W emulsion) preparation. With 0.5% of lignin addition and an optimal O/ W ratio of 6:4, the resulting GA-O/W emulsion exhibited a high cream index value of 100% and excellent storage stability without any phase transition or emulsion aggregation. When using the lignin to prepare curcuminencapsulated microcapsules, a cumulative curcumin remaining of 74.19% under UV radiation and an extraordinary encapsulation efficiency of 62.86% were achieved. Furthermore, this DES pretreatment promoted enzymatic saccharification of the pretreated cellulose substrate, resulting in a glucose yield of 91.49%. After adding 15 wt% of the fibers in soft wood pulp for papermaking, the tear index, ring crush strength index, and tensile index of the produced paper-sheets reached 112.04%, 98.58%, and 83.55% of those of the pure softwood pulp papers, respectively.