Pretreatment of energy cane bagasse with recycled ionic liquid for enzymatic hydrolysis.

A previous study revealed that energy cane bagasse (ECB) pretreated with ionic liquid (IL), 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]), exhibited significantly higher enzymatic digestibility than untreated or water-treated ECB due to delignification and reduction of cellulose crystallinity. This study evaluated the effect of multiple recycled IL on the pretreatment of ECB for enzymatic hydrolysis. ECB was pretreated with [EMIM][OAc] (5% (w/w)) at 100 °C or 120 °C for 0.5 h up to 4 h followed by hydrolysis with commercially available enzymes. The post-pretreatment IL-containing liquid was evaporated at 100 °C for 12 h to remove water and then reused during pretreatment without any further purification. The enzymatic digestibility decreased as the number of pretreatment recycles increased. Decreasing pretreatment temperatures from 120 °C to 100 °C and extending the residence times from 0.5 h to 2 h brought significant improvement to the pretreatment efficiency of recycled [EMIM][OAc] on ECB.