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Title:Production of 1-butanol and butanol isomers by metabolically engineered Clostridium beijerinckii and Saccharomyces cerevisiae
Author(s):Seo, Seungoh
Director of Research:Blaschek, Hans P.; Jin, Yong-Su
Doctoral Committee Chair(s):Miller, Michael J.
Doctoral Committee Member(s):Lu, Ting
Department / Program:Food Science & Human Nutrition
Discipline:Food Science & Human Nutrition
Degree Granting Institution:University of Illinois at Urbana-Champaign
Clostridium beijerinckii
Saccharomyces cerevisiae
Metabolic engineering
Abstract:The overall goal of my thesis research is to produce four-carbon alcohols such as 1-butanol and 2,3-butanediol, and isobutanol as advanced biofuels and chemicals from microorganisms through metabolic engineering, systems biology, and synthetic biology approaches. Biobutanol is an attractive renewable biofuel and intermediate chemical that has been produced from the ABE (acetone-butanol-ethanol) fermentation by solventogenic clostridia such as Clostridium beijerinckii. Although the ABE fermentation is considered as a promising process for butanol production, current drawbacks in the ABE fermentation include low titer, yield, and productivity of solvent production that needs to be improved to achieve an economically viable process. Therefore, the first goal of my thesis study was to improve the ABE fermentation by C. beijerinckii for production of butanol and its derivatives. This first objective involved four approaches. First, optimization of ABE fermentation condition was conducted to maximize butanol production in a small-scale standard platform. Second, product diversification in the ABE fermentation producing butyl esters was carried out through simultaneous ABE fermentation, condensation, and extraction to compensate the low yield of butanol. Third, oxygen-independent fluorescence reporter protein (FbFP) was employed for evaluating protein expression in C. beijerinckii under strict anaerobic conditions. With the FbFP reporter, screening of mutant, analysis of cell population, and metabolic engineering of C. beijerinckii were achieved. Lastly, evolutionary engineering of C. beijerinckii was performed to increase cell growth on lignocellulosic hydrolysate which is a potential feedstock for industrial butanol production. The second goal of my thesis study was to produce butanol isomers including 2,3-butanediol (2,3-BD) and isobutanol by industrial yeast S. cerevisiae strain. For this purpose, evolutionary engineering and metabolic engineering of pyruvate decarboxylase (Pdc)-negative S. cerevisiae were performed to increase the production of butanol isomers by eliminating ethanol production. The metabolically engineered Pdc-negative S. cerevisiae containing heterologous 2,3-BD biosynthetic pathway successfully produced 2,3-BD at high titer, yield and productivity without ethanol production. Isobutanol production was also significantly increased through identification of metabolic limitations and optimization of metabolic pathways in the recombinant Pdc-negative S. cerevisiae harboring a cytosolic isobutanol biosynthetic pathway. Overall, this study has broad implications for the sustainable biological production of higher-chain alcohols as advanced biofuels and chemicals which can replace the use of fossil fuel and petroleum. Moreover, findings and tools obtained in this study can be applied to synthetic biology and metabolic engineering of other solventogenic clostridia and yeast strains toward increased production of value-added bioproducts.
Issue Date:2017-04-20
Rights Information:Copyright 2017 Seungoh Seo
Date Available in IDEALS:2017-08-10
Date Deposited:2017-05

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