Doctoral Defense - Christina M. Wark

About the Event

The Department of Chemical Engineering and Materials Science

Michigan State University

Ph.D. Dissertation Defense

May 2, 2025 at 10 am

3540 EB and Zoom

 Contact Department or Advisor for Zoom Information

Abstract

Multiscale Models in Bioelectrochemical Engineering

By: Christina M. Wark

Advisor: Dr. Scott Calabrese Barton

              Future technological progress will increasingly rely on biomaterials and bioinspired mechanisms. We can draw inspiration from nature to meet industrial needs because biological materials and mechanisms are often highly efficient and superior to other synthesized materials. Overall, the work herein strives to advance understanding of bio-inspired materials for a versatile set of engineering challenges and solutions.

              First, we study the highly efficient reaction cascade of the tricarboxylic acid (TCA), or Krebs, cycle, which converts nutrients in food to usable energy in fractions of seconds. Of particular interest in the TCA cycle is the conversion of oxaloacetate (OAA) between malate dehydrogenase (MDH) and citrate synthase (CS). Based on previous experimental and computational studies of recombinant and mutant MDH-CS complexes, a time-dependent finite difference model was developed to predict each complex's transfer efficiency and determine the surface’s reaction pathways. Utilizing the kinetic parameters of recombinant and mutant complexes determined experimentally and surface transition probabilities of OAA from a Markov state model, the lag time of MDH-CS was determined computationally for recombinant and mutant complexes. Additional implications of the reaction path and reversible reaction at MDH are also considered. This model study furthers the understanding of dynamic enzymatic cascades and points toward approaches to cascade design.

              Second, we address the upgrading of bio-oil from pyrolyzed lignocellulosic biomass. Bio-oils yield a complex mixture of organic constituents that can be used as feedstock for valuable chemicals. However, these molecules are often oxygenated with low energy density. Recently, electrocatalytic hydrotreatment (ECH) of bio-oil was used to reduce oxygen content and increase energy density. Mechanistic understanding of interaction effects in mixtures is required for effective process design. Here, the mechanisms by which ECH of bio-oil constituent 4-propylphenol (4-PP) is inhibited by furfural (FF) are studied computationally. Inhibition is elucidated through potential dependent studies of adsorption and reaction mechanisms on a platinum/ruthenium electrocatalyst. Thermodynamic studies suggest that the FF pathways are competitive in adsorption and more favorable in reactions due to fewer barriers and smaller limiting potentials than the 4-PP pathways. Prediction of activation barriers by reaction energy scaling techniques found the FF pathways also to be favored kinetically over the 4-PP pathways. Reaction thermodynamics and kinetics models suggest that FF inhibits 4-PP hydrotreatment because the FF pathways are more favorable than 4-PP pathways on a platinum/ruthenium catalyst.

              Finally, a new biomaterial is evaluated as a high performance substrate in tissue regeneration applications. A biomaterial was previously developed where gelatin was first modified by methacrylic anhydride (GelMA) for stability at physiological conditions, then silver-bioactive glass (Ag-BG) was added for antibacterial properties. Suspension of chemically linked GelMA and Ag-BG (GAB) was hypothesized to exhibit superior structural and cell viability behavior to GelMA in extrusion printed applications, which we seek to validate here. Scaffold printing parameters were optimized for acellular GelMA, GAB, and a GelMA + Ag-BG nanoparticle composite bio-ink. Then, cell-laden media was introduced to the bio-ink to generate scaffolds. The viability of the cells within the scaffold was observed over time after printing. Ultimately, bio-ink performance and cell viability were poor for the selection of materials during cellular printing. These challenges suggest further optimization steps are needed within the material synthesis and printing processes. More recent work on GelMA and GAB synthesis shows promising improvements in the performance of these materials.

Persons with disabilities have the right to request and receive reasonable accommodation. Please call the Department of Chemical Engineering and Materials Science at 355-5135 at least one day prior to the seminar; requests received after this date will be met when possible.