Supercritical carbon dioxide combined with 1-butyl-3-methylimidazolium acetate and ethanol for the pretreatment and enzymatic hydrolysis of sugarcane bagasse

Abstract

The use of green solvents for the partial delignification of milled sugarcane bagasse (1mm particle size) and for the enhancement of its susceptibility to enzymatic hydrolysis was demonstrated. The experiments were carried out for 2h using 40 g of supercritical carbon dioxide combined with 1-butyl-3-methylimidazolium acetate and 15.8 g of ethanol. The effects of temperature (110-180 °C), pressure (195-250 bar) and IL-to-bagasse mass ratio (0:1-1:1) were investigated through a factorial design in which the response variables were the extent of delignification and both anhydroglucose and anhydroxylose contents in the pretreated materials. The highest delignification degree (41%) led to the best substrate for hydrolysis, giving a 70.7 wt% glucose yield after 12h using 5 wt% and Cellic CTec2® (Novozymes) at 10 mg g(-1) total solids. Hence, excellent substrates for hydrolysis were produced with a minimal IL requirement, which could be recovered by ethanol washing for its downstream processing and reuse.

Keywords: Enzymatic hydrolysis; Ionic liquid; Pretreatment; Sugarcane bagasse; Supercritical organosolv.