Deep eutectic solvent-based biorefining of bamboo residues for enhanced polysaccharide recovery: Optimization via response surface methodology.

Abstract

Deep eutectic solvents (DES) have emerged as promising green alternatives to ionic liquids for lignocellulosic biomass pretreatment, owing to their low cost, biodegradability, and tunable physicochemical properties. However, synergistic effects of DES composition and processing parameters on biomass fractionation remain insufficiently explored. In this study, six DES systems composed of choline chloride (ChCl) as hydrogen bond acceptor and various hydrogen bond donors (glycerol, Gly; ethylene glycol, EG; monoethanolamine, MEA; urea, U; lactic acid, LA; and formic acid, FA) were systematically investigated for their effectiveness in pretreating bamboo residues (BR). Among them, ChCl/LA exhibited superior delignification capacity (65%) and significantly enhanced the total sugar yield (up to 49%) compared to untreated BR. Structural and physicochemical analyses using X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy revealed pronounced deconstruction of the lignocellulosic matrix after ChCl/LA pretreatment. To further optimize the process, response surface methodology was employed, identifying optimal pretreatment conditions of 117 °C, a ChCl/LA molar ratio of 1:4, and 121 min. Under these conditions, glucose yield increased by 59% relative to the unoptimized treatment. These findings demonstrate that ChCl/LA-based DES pretreatment effectively enhances enzymatic hydrolysis of BR, offering a robust and eco-efficient strategy for lignocellulosic biomass valorization in sustainable biorefinery processes.