(6ce) Multiscale Modeling to Make Cellulosic Biofuels More Abundant and Affordable

As recognized by the 2013 Nobel Prize in Chemistry, “computer models mirroring real life have become crucial for most advances made in chemistry today.”[1]The focus of my research is the application of theoretical and computational methods for uncovering reaction mechanisms that convert non-food biomass into renewable fuels and chemicals. Specifically, my PhD work examines two approaches to cellulose deconstruction: thermochemical and enzymatic processes. In the thermochemical portion of my work, I use quantum mechanics to investigate the elementary steps in cellulose depolymerization under fast pyrolysis conditions. For example, competing mechanisms, specifically homolytic vs. heterolytic, had been debated for many years. Experiments designed to test each hypothesis have been inconclusive. Using computational chemistry, specifically quantum mechanics, I modeled both pathways and discovered a more likely mechanism that better matches for experimental results. My latest work examines the effects of inorganic ions on reaction kinetics, to help understand how these naturally-occurring biomass components change product yield. Additionally, my work has revealed mechanisms that provide targets for catalyst design. The results from this part of my dissertation enable more accurate, mechanistic modeling of biomass pyrolysis that can be used to improve cellolosic biofuel process design and efficiency.

In contrast to biomass fast pyrolysis, which relies on high temperatures to break cellulose’s strong bonds, enzymes manipulate cellulose to allow depolymerization at ambient temperatures. Many of the details of how enzymes perform these feats remain unclear. Structural biology has revealed the three-dimensional structures of many enzymes, with and without a substrate present. Molecular simulations allow us to investigate an enzyme's action in the fourth dimension, tracking catalysis over time. These efforts are computationally challenging due both to the system size and the high level of accuracy needed to accurately capture what can be profound stereoelectronic effects resulting from small perturbations in atomic and electronic structure.

Sustainable energy will remain the focus of my future research, and I will continue applying and expanding my expertise in multiscale modeling to make renewable energy more abundant and affordable.