Ionic liquid pretreatment of yellow pine followed by enzymatic hydrolysis and fermentation.

In this study, it was aimed to enhance the enzymatic hydrolysis of recalcitrant yellow pine wood and subsequently to produce ethanol efficiently through the application of 1-ethyl-3-methylimidazolium acetate (EMIMAc) ionic liquid. The effect of biomass particle size (<2.5 mm, 500-850 μm, 363-500 μm, and <363 μm) prior to pretreatment and pretreatment time (15, 30, and 45 min) on the structural properties and enzymatic hydrolysis yield of EMIMAc pretreated pine wood were also investigated. In general, EMIMAc functioned more efficiently at larger biomass particle sizes compared to smaller ones. Dissolution of solids by pretreatment, amount of lignin extracted from biomass as well as biomass to glucose yield was increased with increasing pretreatment time. The conversion of biomass to glucose was 56% under the selected optimum conditions (500-850 μm particle size; 5% biomass concentration and 140°C-45 min EMIMAc pretreatment). The biomass samples pretreated at the optimal conditions were subjected to simultaneous saccharification and fermentation (SSF) and separate hydrolysis and fermentation (SHF) which resulted in ethanol yields of 86 and 96%, respectively. The results presented in this study give a general framework for reducing the recalcitrance of pine to enzymatic saccharification and microbial fermentation by EMIMAc pretreatment without need for long pretreatment times and size reduction.