Tailored one-pot lignocellulose fractionation to maximize biorefinery toward controllable producing lignin nanoparticles and facilitating enzymatic hydrolysis

To achieve the global bio-based recycling economy with lignocellulosic biomass as feedstock, the additional value must be gained from both carbohydrates and lignin. In this study, a tailored one-pot lignocellulose fractionation, which was driven by ultrafast and recyclable microwave-assisted ternary deep eutectic solvent (DES, choline chloride: ethylene glycol: AlCl3) pretreatment, was developed to significantly reduce the natural "biomass recalcitrance", promoting the production of lignin nanoparticles and facilitating enzymatic saccharification of cellulose. Confocal Raman microscopy (CRM) was applied to visually monitor the delignification in different cell walls during the DES pretreatments. Under the optimal condition (110 degrees C, 10 min), the glucose yield of the pretreated poplar via enzymatic saccharification reached 95.4 %, which was 5.8 times higher than that of the control. Advanced NMR characterizations of the DES lignin and control lignin fractions demonstrated that lignin polymers in the poplar wood had undergone the following structural changes, such as dehydration, depolymerization, condensation, and modification. Results showed that the regenerated DES lignin were nanosized lignin, exhibiting the low molecular weights, narrow distribution (1.28<PDI<1.38) with controllable size (<100 nm), and excellent antioxidant activity. In short, the tailored one-pot DES fractionation will improve the enzymatic digestibility and facilitate the lignin valorization, which will further promote the economic and overall benefits of biorefinery.