Green pretreatment routes using deep eutectic solvents for biopolymer fractionation and cellulose acetate production from agave bagasse

Abstract Lignocellulosic waste biomass can be revalued by fractionating its complex structure into its main biopolymers – lignin, cellulose, and hemicellulose. This study explores the production of cellulose acetate from pretreated agave bagasse using deep eutectic solvents (DES). Optimized delignification was achieved with DES and the material was analyzed using scanning electron microscopy (SEM), Fourier‐transform infrared spectroscopy (FTIR), and crystallinity index (CrI) measurements. Cellulose acetates were produced by heterogeneous acetylation, and the degree of substitution (DS) and esterification (ED) were determined. Acetates were further analyzed by FTIR and thermal analyses, specifically thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Deep eutectic solvent pretreatments, especially using ChCl‐LA and ChCl‐OxA, altered agave bagasse fibers, improving cellulose accessibility. ChCl‐LA DES was the most effective, removing 38.99% of lignin. Scanning electron microscopy images showed fiber roughening, and FTIR confirmed lignin deconstruction. ChCl‐LA reduced polymerization to 718 and ChCl‐OxA reduced it to 326. X‐ray diffraction revealed increased crystallinity in all cases. The acetates reached their highest %ED and DS when choline chloride–lactic acid (ChCl‐LA) was used, with a %ED of 46.11% and a DS of 2.7. ChCl‐Gly, although less effective in structural modification, preserved the degree of polymerization (DP), making it suitable for applications prioritizing polymer retention. Thermal analysis of acetates showed similar results to commercial acetates. These findings highlight the versatility of DES in modifying lignocellulosic materials for industrial application.