Enhancing the enzymatic digestibility of sugarcane bagasse through the application of an ionic liquid in combination with an acid catalyst

Various ionic liquids have been identified as effective pretreatment solvents that can enhance the cellulose digestibility of lignocellulose by removing lignin, one of the main factors contributing to the recalcitrant nature of lignocellulose. 1‐Butyl‐3‐methylimidazolium methylsulfate ([BMiM]MeSO4) is a potential delignification reagent, hence its application as a pretreatment solvent for sugarcane bagasse (SB) was investigated. The study also evaluated the benefit of an acid catalyst (i.e., H2SO4) and the effect of pretreatment conditions, which varied within a time and temperature range of 0–240 min and 50–150°C, respectively. The use of an acid catalyst contributed to a more digestible solid and a higher degree of delignification. However, the [BMiM]MeSO4‐H2SO4 combination failed to produce a fully digestible solid, as a maximum cellulose digestibility of 77% (w/w) was obtained at the optimum pretreatment condition of 125°C for 120 min. Furthermore, up to half of the lignin content could be extracted during pretreatment, while simultaneously extensive, sometimes complete, removal of xylan, the presence of which, also hampers cellulose digestibility. Hence, [BMiM]MeSO4 has been identified an effective pretreatment solvent for SB as the application thereof both significantly improved digestibility, and simultaneously removed two of the main factors contributing to the recalcitrant nature of lignocellulose. As xylan and lignin have potential value as precursor chemicals, the existing process may in future be extended toward substrate fractionation, a biorefinery concept where value is added to all feedstock constituents. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2012