Energy Science and Engineering PhD, 2016
Current Employment: AbbVie, Inc
Mentors: Cong T. Trinh
Dissertation Description: The development of a secure and sustainable energy economy is likely to require the production of fuels and commodity chemicals in a renewable manner. The use of biological feedstocks for the production of such chemicals has been used industrially since World War I, but the potential of biological processes has yet to be reached and the investment in such technologies has ebbed with market forces over the last century. There has been renewed interest in biological commodity chemical production recently, in particular focusing on non-edible feedstocks. The fields of metabolic engineering and synthetic biology have arisen in the past 20 years to address the challenge of chemical production from biological feedstocks.
Metabolic modeling is a powerful tool for studying the metabolism of an organism and predicting the effects of metabolic engineering strategies. Various techniques have been developed for modeling cellular metabolism, with the underlying principle of mass balance driving the analysis. The different strategies have advantages and disadvantages which can be leveraged by combining alternative approaches.
In this dissertation, two organisms with industrial prominence and potential were examined for their potential to produce biofuels. First, Saccharomyces cerevisiae was used to create biodiesel in the form of fatty acid ethyl esters through expression of a heterologous acyl-transferase enzyme. Several genetic manipulations of lipid metabolic and / or degradation pathways were rationally chosen to enhance FAEE production, and then culture conditions were modified to enhance FAEE production further. The results were used to identify the rate-limiting step in FAEE production, and provide insight to further optimization of FAEE production.
Next, Clostridium thermocellum, a cellulolytic thermophile with great potential for consolidated bioprocessing but a weakly understood metabolism, was studied for enhanced ethanol production. To accomplish the analysis, two models were created for C. thermocellum metabolism. The core metabolic model was used with extensive fermentation data to elucidate kinetic bottlenecks hindering ethanol production. This was accomplished using Elementary Mode Analysis on a number of genetically modified strains. A genome scale metabolic model was next constructed and tuned using extensive fermentation data as well, and the refined model was used to investigate complex cellular phenotypes with Flux balance Analysis. In particular, the difference in ethanol to acetate ratios between cellobiose and cellulose-grown cultures provide insight into the way that C. thermocellum restructures its metabolism in response to different carbon sources.
This work presented within provide a platform for the continued study of S. cerevisiae and C. thermocellum for the production of valuable biofuels and biochemicals.
PhD in Energy Science and Engineering, University of Tennessee, 2016
Master of Science, Chemistry, Georgia State University, 2011
Bachelor of Science, Biochemistry, Georgia Institute of Technology, 2008
Awards and Recognitions
Graduate Assistant Fellowship, GSU, 2009-2011
GT President's Undergraduate Research Award, 2006
Google Scholar profile: Adam Thompson