Deep Eutectic Solvent Pretreatment to Enhance the Enzymatic Saccharification Efficiency of Cotton Fibers

Cotton fibers constitute one of the most abundant cellulose-rich resources, offering potential as feedstock for bioethanol production through enzyme-catalyzed hydrolysis into fermentable sugars. However, the inherent structural limitations of fibers considerably restrict cellulase accessibility, leading to low saccharification efficiency. To address this limitation, a pretreatment strategy employing a deep eutectic solvent (DES), comprising choline chloride (ChCl) and p-toluenesulfonic acid (TsOH) at a molar ratio of 1:1 and 75% (v/v) concentration, was investigated. Suitable pretreatment conditions, 90 ℃ for 1 h with a solid-liquid ratio of 1:30, effectively enhanced the yield of enzyme-catalyzed hydrolysis by approximately 1.8 times. Additionally, the recyclability assessment indicated sustained pretreatment efficacy over at least three cycles of DES. Moreover, a notable synergistic effect was observed when cellulase and cellobiase were compounded at a volume ratio of 4:1, which further enhanced the yield by around 1.4 times. The integration of DES pretreatment with compound enzyme system resulted in a remarkable 2.4 times increase in saccharification efficiency, achieving within 2 h a hydrolysis yield equivalent to that obtained after 12 h using cellulase alone. This study provides critical insights into efficient and sustainable strategies for enzyme-catalyzed hydrolysis of cotton fibers and demonstrates the promising applicability of DES in cotton biomass valorization.