Efficient Pretreatment of Rice Straw by Combination of Screw Press and Ionic Liquid to Enhance Enzymatic Hydrolysis

Abstract

The increasing value of lignocellulose-based biorefining has attracted interest from research and development organizations worldwide to find an efficient pretreatment method for dissociating the recalcitrated structure of lignocellulosic biomass. Nowadays, different pretreatment processes have been developed, including chemical, physical or biological processes. In this study, the effects of pretreatment by a combination of screw-press and four different types of ionic liquids (ILs) to enhance the saccharification efficiency were observed to select the best IL. The inhibition effects of ILs were monitored based on the relative cellulase activities, and the results showed that each IL had a different inhibition degree. Based on pretreatment efficiency and inhibition properties, 1-allyl-3-methylimidazolium chloride, [AMIM]Cl, was selected for the optimization experiment using response surface methodology with a three-factor Box-Behnken design (consisting of ionic liquid concentration, reaction temperature and retention time). Under the best conditions (150 °C reaction temperature, 50% concentration), 68.26% of recovered sugar could be achieved from the pretreated rice straw. A mathematical model represented the statistically significant (P < 0.05) effects of two treatment parameters (temperature and concentration) on the saccharification efficiency with a coefficient of determination of 0.7460.