2.3 DES pretreatment
Sorghum stover was loaded to a reactor containing DES at a 1:10 (w/w) biomass-to-solvent ratio. A vortex mixer was used to rigorously mix the biomass and DES before the reaction. The mixtures were processed at 120–140 °C for 3 h in an oil bath with continuous stirring at 500 rpm. Upon the end of the pretreatment, the reaction was quenched by adding ethanol/water 1:1 (v/v) solution and acetone. The solid fraction was washed with ethanol/water solution 1:1 (v/v). Further solvent washing was conducted to completely recover the fractionated lignin from the pretreated biomass.