(735b) On the Molecular Origin of Cellulose Recalcitrance

Decomposing lignocellulosic biomass by catalytic or enzymatic means presents a potential route for producing fuels from renewable sources. However, the recalcitrance of cellulose, the major component of biomass, needs to be overcome. To develop a molecular basis for improving the current technologies of biomass decomposition, we use all-atom molecular dynamics simulations and coarse-grain modeling to quantify the structure-property relationships of both I_β and I_α types of cellulose microfibrils. To probe solvent effects on the structures and mechanical properties of cellulose, simulations are performed in water as well as in the ionic liquid 1-butyl-3-methyl-imidazolium (BMIM) chloride, which is known to dissolve cellulose. We characterize the spatial dependence of the strength of the complex network of hydrogen bonds within cellulose, as well as the solvation structures at the different surfaces of a cellulose microfibril. We found that intrachain and interchain hydrogen bonds are disrupted appreciably due to surface exposure and interactions with solvent molecules, but intersheet interactions are persistent throughout the material. These results indicate that the often-overlooked intersheet hydrogen bonds are in fact an essential element of biomass recalcitrance.