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Metabolic Engineering of Central Carbon Metabolism for Production of Isobutanol and other Higher Alcohol Biofuels in Saccharomyces cerevisiae Open Access


Other title
Metabolic Engineering
Type of item
Degree grantor
University of Alberta
Author or creator
Ofuonye, Ebele Josephine
Supervisor and department
Dr. David Stuart
Examining committee member and department
Dr. Michael Ellison (Biochemistry)
Dr. Joel Weiner (Biochemsitry)
Dr. David Bressler (Agricultural, Food and Nutritional Science)
Department of Biochemistry

Date accepted
Graduation date
Master of Science
Degree level
The yeast Saccharomyces cerevisiae was engineered for production of high-value alcohols including isobutanol and isopentanol. This strategy uses the host’s highly active valine amino acid biosynthetic pathway and diverts its 2-ketoacid intermediate for alcohol synthesis. A 2-ketoacid decarboxylase from lactococcus lactis (kdcA) efficiently utilizes the branched chain precursor 2-ketoisovalerate to produce isobutyraldehyde, which can then be converted to isobutanol by alcohol dehydrogenase. In the presence of high concentration of valine, overexpression of kdcA and the E. coli yqhD alcohol dehydrogenase leads to increased isobutanol production of 15mg/g of valine. The valine biosynthetic pathway was also engineered for efficient production of alcohols from glucose by overexpressing the genes involved in valine biosynthesis (ILV2, ILV6, ILV3 and ILV5 genes) in addition to kdcA and yqhD. This strain produced ~150mg/liter of isobutanol; a yield of 1.88mg/g of glucose. Deletion of LEU4, LEU9 and BAT1 genes involved in competing reactions was not beneficial for isobutanol production.
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