Improved enzymatic hydrolysis and ethanol production by combined alkaline peroxide and ionic liquid‐water mixtures pretreatment of rice straw

BACKGROUND Rice straw (RS), one of the most plentiful lignocellulosic wastes worldwide, has been considered a potential candidate to produce bioethanol. The object of this work was to develop an efficient and feasible pretreatment process for RS with alkaline peroxide combined with ionic liquid (IL)–water mixtures, reveal the mechanism, and achieve biomass valorization. RESULTS Alkaline peroxide pretreatment under mild conditions combined with IL–water mixtures pretreatment at a water content of 30 wt% was established, leading to a maximum lignin removal of 63.8% with an enzymolysis efficiency of 92.1% and a simultaneous saccharification and co‐fermentation efficiency of 91.0%. Furthermore, the recycled IL also showed good performance with the established pretreatment process, resulting in 251.6 g L−1 of reducing sugar and 91.9 g L−1 ethanol at high solid loading. The alkaline peroxide pretreatment enhanced lignin extraction and disrupted the RS structure to facilitate the dissolution of amorphous components by the IL–water mixtures. CONCLUSION A simple and efficient pretreatment was successfully established. The IL was successfully recycled for further pretreatments, and high concentrations of reducing sugars and ethanol were achieved using the pretreated RS. The effectiveness of the pretreatment process suggested potential application in future biorefineries. © 2018 Society of Chemical Industry