Tuesday, May 3, 2011
Ionic liquids (ILs) are promising solvents for the pretreatment of biomass as certain ILs are able to completely solubilize lignocellulose. The cellulose can readily be precipitated with an anti-solvent for further hydrolysis to glucose, but the anti-solvent must be removed for the IL to be recovered and recycled. In this work, the effect of different pretreatment conditions on the rate and final conversion of enzymatic hydrolysis is studied. Avicel and Miscanthus are pretreated with ILs to understand the difference between pretreatment strategies for pure cellulose and lignocellulose. While Avicel serves as a model for enzyme-cellulose interactions, this work shows that optimized pretreatment strategies towards Avicel do not necessarily yield the best conditions for Miscanthus, reinforcing the importance of the hydrolyses performed on pretreated lignocellulosic substrates. A process is developed for recycling the IL and hydrolyzing the cellulose using a phase separation. A higher and faster conversion of cellulose to glucose is reached with the phase separation system compared to biomass pretreated with only IL. The addition of basic salt during the phase separation allows for partial delignification of the biomass, which makes the substrate more accessible and further accelerates the enzymatic hydrolysis. The time-course hydrolyses show in detail how cellulase kinetics can be affected by different IL pretreatment strategies, and serve as a basis for better understanding enzyme-substrate interactions and pretreatment effectiveness.