Direct Extraction of Uniform Lignin Microspheres from Bamboo Using a Polyol-Based Deep Eutectic Solvent

Conventional preparation of lignin micro-/nano-particles(LMNPs)often needs multiple steps accompanied by high cost, low efficiency,and low yield. Herein, this study established a polyhydric alcohol-baseddeep eutectic solvent (PA-DES) fractionation for direct LMNP assemblyfrom raw lignocellulose. The results indicated that lignin was significantlyextracted by 41.55-70.33% depending on the PA-DES varieties.With lignin removal, the substrate showed high glucan enzymatic saccharificationfrom 70.44 to 100%. Specially, over 90% lignin could be recoveredin each PA-DES, and the obtained LMNPs showed quite uniform sphericalmorphology with a tunable size of 550-3254 nm and narrow polydispersityindex (PDI) of 0.295-0.398. The proposed DES showed a neartheoretical recovery yield, which still featured excellent fractionationperformance even after three cycles of reuse. The findings highlightthe simultaneous utilization of cellulose and lignin in a one-potbiomass fractionation under mild conditions with sugars and LMNPsas the coproducts. PA-DESsyielded uniform lignin microspheres in a one-potprocess using bamboo as the starting material.