Ternary Choline Chloride–Monoethanolamine Based Deep Eutectic Solvent Enhanced Valorization of Bamboo for Concurrent Bioethanol and Carbon Dot Production

Efficient pretreatment is essential for improving the conversion of lignocellulose into fermentable sugars and bioethanol. In this study, choline chloride–monoethanolamine (ChCl-MEA)-based ternary deep eutectic solvents containing H2O2, NaHCO3, Na2S, or ethylene glycol were prepared and applied to pretreatment of Dendrocalamus brandisii. Among the tested systems, ChCl-MEA-Na2S showed the best overall pretreatment performance, achieving 92.8% delignification and 86.1% cellulose retention. It also effectively disrupted lignin–carbohydrate associations, reduced lignin shielding and generated a more accessible cellulose-rich substrate for bioconversion. In the following separation enzymatic hydrolysis and fermentation, 92.2% cellulose in substrate was conversed to glucose and 17.49 g/L ethanol was obtained via the fermentation of enzymatic hydrolysate. Taking the bioconversion of substrate into consideration, the ChCl-MEA-H2O2 and ChCl-MEA-Na2S were recovered for full components utilization. Especially, the carbon dots produced from the degradation compounds in ChCl-MEA-H2O2 DESs had favorable antioxidation and antibacterial performance due to the oxygen-containing group caused by oxidation of H2O2.