Fractionation of Acacia Wood and Sugarcane Bagasse by Levulinic Acid–Choline Chloride Deep Eutectic Solvent Treatment Followed by Alkaline Washing

Deep eutectic solvents (DESs) are versatile media for lignocellulosic biomass fractionation, but their practical relevance depends on whether they remain effective across feedstocks of very different structure and composition. In this study, DESs composed of levulinic acid and choline chloride (LA:ChCl) at molar ratios of 2:1 and 3:1 were applied to two structurally distinct lignocellulosic sources, Acacia wood and sugarcane bagasse, to assess the applicability of the same solvent system to feedstocks of contrasting structure rather than its performance on a single substrate. Extractions were performed at 120, 140, and 160 °C for 1, 2, 4, 6, and 8 h, and process performance was assessed through recovered solid yield and total lignin content in the recovered solid fraction obtained after DES treatment followed by alkaline washing. The combined DES treatment and subsequent alkaline washing resulted in substantial lignin removal from both feedstocks, although the individual contribution of each treatment step could not be determined. For Acacia wood, recovered solid yields of up to 89.20 ± 0.07% and lignin contents as low as 0.94 ± 0.21% were achieved, while for sugarcane bagasse a 67.48 ± 0.15% recovered solid yield and 1.32 ± 0.77% total lignin content were obtained at a 3:1 ratio, 140 °C, and 6 h. A four-factor multivariate analysis revealed a significant Feedstock × Ratio × Time × Temperature interaction, indicating that, although the solvent was effective for both types of biomass, the operational window that maximizes its performance must be tuned to the specific feedstock: Acacia wood exhibited a pronounced trade-off between solid recovery and lignin removal, whereas sugarcane bagasse allowed relatively high recovered solid yields and low lignin contents to be achieved simultaneously. Overall, these results demonstrate the applicability of the LA:ChCl-based fractionation process, including subsequent alkaline washing, to the two structurally distinct feedstocks investigated, while highlighting the need to determine the individual contribution of each treatment step.