Date of Award

Winter 12-15-2016

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Molecular Microbiology & Microbial Pathogenesis)

Degree Name

Doctor of Philosophy (PhD)

Degree Type



Branched-chain fatty acids (BCFAs) are key advanced biofuel precursors with improved cold-flow properties compared to straight chain fatty acids (SCFA). Previous efforts in engineering type II fatty acid synthase (FAS) for BCFA production suffered from low titers and the co-production of SCFAs, complicating efficient BCFA isolation. Through extensive strain characterization, I identified that insufficient lipoylation of 2-oxoacid dehydrogenases is a key bottleneck in BCFA production. Consequently, I complemented the lipoylation defect by engineering two lipoylation pathways, which not only restored protein lipoylation, but allowed for the highest BCFA titer reported (over 276 mg/L), with BCFA production comprising over 85% of total free fatty acids. The high percentage of BCFA achieved facilitates downstream conversions and purification. Colleagues and I then fine-tuned BCFA branch positions by engineering the upstream pathway to control the supply of various branched-chain acyl-CoAs, demonstrating tight control of chain structure, with over 93% of BCFA corresponding to the input chain structure. We then applied the same BCFA platform to generate branched-chain fatty acid ethyl esters, alcohols, and alkanes, all in high percentages- demonstrating the utility of the platform to generate high quality advanced biofuels and chemicals.


English (en)

Chair and Committee

Fuzhong Zhang

Committee Members

Scott Hultgren, Gautam Dantas, Petra A. Levin, Yinjie Tang


Permanent URL: https://doi.org/10.7936/K74X566V

Available for download on Tuesday, December 15, 2116