Ionic liquids assisted alkaline fractionation enhanced triploid poplar bioconversion for bioethanol production
In this case, [Amim]Cl, [Bmim]Cl and [Emim]Ac were used to dissolve ball-milled triploid poplar, and the cellulose-rich preparations were subsequently recovered via incubation in 5 % NaOH aqueous solution and filtration. After the stepwise pretreatments, the carbohydrate content in the cellulosic residues increased to 73.3, 73.6 and 79.0 %, respectively, from 66.1 % in that with sole alkali fractionation. In comparison, the treatment with [Emim]Ac incurred transformation of cellulose I to II, which was favorable to enhance the alkaline fractionation for lignin extraction and disruption of biomass intact structure. After reconstitution, the digestibility of the three cellulosic preparations was all improved, yielding 1.3-fold higher fermentable sugars than that without IL pretreatment (67.2 %). These results indicated that the stepwise pretreatment with ionic liquid and alkali was effective for disrupting the intact structure of plant cell wall, and improving the productivity of bioethanol from lignocellulose biomass.