Protic ionic liquids as effective agents for pretreatment of cotton stalks at high biomass loading

This work demonstrated the performances of different protic ionic liquids (PILs) with respect to their effects on the pretreatment of cotton stalks at a relatively high biomass loading. Among the investigated PILs, 1-butylimidazolium hydrogen sulfate (HBIMHSO4) employed in the presence of 20% (w/w) water at 15% biomass loading and 120 °C for four hours resulted in significant structural changes in the biomass. The lignin content of the cotton stalks was reduced by 35% and the cellulose content increased from 36% to 55% through HBIMHSO4 pretreatment. Enzymatic hydrolysis of the biomass was enhanced almost 5-fold despite an increase in the biomass crystallinity. Morphological changes in the cotton stalks observed through SEM analysis verified the differences in the composition and enzymatic accessibility of the biomass samples subjected to PIL pretreatment. The results successfully revealed the potential of the PIL, HBIMHSO4 for the valorization of cotton stalks, as a significant industrial crop waste, for the first time in the literature.