Pretreatment of Pennisetum sinese Roxb. with the hydrous deep eutectic solvent

Efficient pretreatment is crucial for overcoming lignocellulose recalcitrance and improving enzymatic saccharification. Deep eutectic solvents (DESs), commonly used for lignocellulose pretreatment, face challenges such as high cost, viscosity, and difficult separation. Adding water to DESs can reduce costs and viscosity, but the mechanisms and effects are not well understood. In this study, the p-toluenesulfonic acid/choline chloride (p-TsOH/ChCl) DES system was used to pretreat Pennisetum sinese Roxb. (P. sinese) biomass. Increasing water content above 30 % improved cellulose retention but reduced hemicellulose and lignin removal. A 50 % water-added DES showed a 98.9 % reduction in viscosity, preventing lignin precipitation and increasing its removal from 6.1 % to 83.4 %. Despite reduced carbohydrate solubility, cellulose retention increased, and enzymatic hydrolysis yield rose from 39.3 % to 87.8 %. Notably, the pretreatment efficiency of the hydrous DES remained stable even after four recycling cycles. This study verifies the advantages of aqueous DES in treating P. sinese-a plant with high biomass yield and strong stress tolerance, which is conducive to promoting the green and efficient acquisition of the biomass sugar platform.