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

• Author / Creator

  Ofuonye, Ebele Josephine

• 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.

• Subjects / Keywords

  • Biofuels
  • Metabolic Engineering

• Graduation date

  Fall 2012

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3MM3S

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.