Facile and rapid fractionation of bamboo wood with a p-toluenesulfonic acid-based three-constituent deep eutectic solvent

Abstract

Here, we report a strategy with the application of p-toluenesulfonic acid (p-TsOH) based three-constituent deep eutectic solvent (3c-DES) for the efficient fractionation of bamboo wood towards its main components. Three kinds of deep eutectic solvents (DESs), including choline chloride (ChCl)/ ethylene glycol (EG)/p-TsOH, tetrabutylammonium chloride (N4Cl)/EG/p-TsOH and tetrapropylammonium chloride (N3Cl) /EG/ p-TsOH, were facilely prepared and assessed for the pretreatment of bamboo wood. ChCl-EG-p-TsOH (molar ratio of 1:0.5:1) was found to be the most effective, evidenced by more than 93.36% xylan and 90.32% lignin removals with most of the cellulose (86.73%) retained in the pretreated bamboo in a short time of 10 min at 100 °C and a 10 wt. % solid loading, which significantly improved delignification by more than 85% compared with that of using ChCl-EG (molar ratio of 1:2) as a two-constituent at the same conditions. The 3c-DES pretreatment resulted in the desirable deconstruction of the recalcitrant of cell walls in woody biomass, evidenced by the higher glucose yield of 90.2% by the enzymatic hydrolysis of the cellulose-rich substrate, which was nearly four-fold higher than that of the untreated bamboo. The extracted lignin showed high purity (95%) with a moderate and homogeneous molecular weight, showing promising potential applications in the downstream production of biochemicals and biomaterials. Furthermore, the 3c-DES exhibited excellent recoverability by evaluating the fractionation efficiency and enzymatic hydrolysis performance with the recycled DES. The results from this study demonstrated that p-TsOH-based 3c-DES showed practical significance for the fast and effective fractionation of woody biomass for high-quality components.