Mechanochemical Fractionation of Straw Biomass to Maximize Biorefinery Value Using Alkaline Deep Eutectic Solvents at Room Temperature

Thoughtful utilization of the entire lignocellulose is important to achieve sustainable and cost-effective biorefineries. However, there is a trade-off between efficiently utilizing carbohydrates and stabilizing the lignin aryl ether structure due to the recalcitrance and heterogeneity of biomass. This work proposed the ball-milling-assisted alkaline deep eutectic solvents (quaternary ammonium hydroxides with monoethanolamine) mechanochemical fractionation process to extract high-value amphiphilic lignin-carbohydrate complexes (LCCs) by preserving the phenyl glycosidic bonds while coproducing high-quality cellulose and Xylan. Results showed that high cellulose saccharification efficiency (74.2–96.4%) was achieved with nearly 100% cellulose recovery. The resulting LCCs and Xylan were not subjected to undesired chemical structural modifications, exhibiting extremely high β-O-4 bond contents (48.8/100 Ar) and favorable carbohydrate properties, respectively. It was calculated that 100 g of original straw could produce 31.1 g of glucose, 9.6 g of LCCs, and 12.3 g of Xylan in a cascade using this process route. It was proposed that mechanochemical effects could enhance the selective destruction of lignocellulose hydrogen-bonding networks, which allowed the subsequent cascade fractionation of the three value-added products by adjusting solution properties. In short, this work provided a mild and efficient mechanochemical fractionation process for whole-component utilization of lignocellulose, which has great potential in sustainable biorefinery applications.