Structural Understanding of Key Physical Processes in the Pretreatment and Enzyme Hydrolysis of Biomass

Lignocellulosic biomass is a complex biological composite material that shows significant recalcitrance towards the structural deconstruction and enzymatic hydrolysis into sugars that is necessary for fermentation to bioethanol. This talk will summarize developments in the “Dynamic Visualization of Lignocellulose Degradation by Integration of Neutron Scattering Imaging and Computer Simulation” for multiple-length scale, real-time imaging of biomass during pretreatment and enzymatic hydrolysis. By combining multiple probes of structure, sensitive to different length scales, with molecular dynamics simulations, we reveal the fundamental physical processes responsible for the morphological changes in biomass during steam explosion pretreatment. We show that the basic driving forces are the same in other leading pretreatments, such as dilute acid pretreatment. The compensation between the entropy and enthalpy of hydration drives the cell wall components over kinetic barriers, destabilizing them, and causing changes that render cellulose more accessible to hydrolytic enzymes. We also utilized neutron scattering to probe cellulase enzyme structure while hydrolyzing deuterated bacterial cellulose. These show new insights into structural changes of lignin and cellulose during dilute acid pretreatment and cellulose-cellulase interactions.