Optimization of processing conditions for the pretreatment of wheat straw using aqueous ionic liquid

Pretreatment of wheat straw with the aqueous ionic liquid, 1-ethyl-3-methylimidazolium acetate, was optimized to maximize fermentable sugars recovery. The optimization process employed a central composite design, where the investigated variables were temperature (130-170°C), time (0.5-5.5h) and ionic liquid concentration (0-100%). All the tested variables were identified to have significant effects (p<0.05) on fermentable sugars recovery. The optimum pretreatment conditions were 158°C, an ionic liquid concentration of 49.5% (w/w), and a duration of 3.6h. Cellulose and xylan digestibility generally increased with increasing temperature, time and ionic liquid concentration; but, the carbohydrates recovered in the washed solids following pretreatment decreased. Thus, the final optimum conditions for maximizing fermentable sugars from the starting biomass were a compromise between greater digestibility and minimal carbohydrates loss during pretreatment.