Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Chemistry and Biochemistry

Committee Chair(s)

Lance C. Seefeldt


Lance C. Seefeldt


Scott A. Ensign


Joan M. Hevel


Sean J. Johnson


Jixun Zhan


The continued increase in the demand for fossil fuels combined with their ever dwindling supply has prompted the search for a suitable alternative fuel. The research contained within this dissertation seeks to increase the lipid content of cellular feedstocks, improve extraction efficiencies of lipids, and understand the pathways involved in the production of fatty alcohols and triacylglycerides from microbial feedstocks. As part of this research the diatom, Cheatoceros gracilis, was grown at small and large scale to determine optimal growing conditions. No apparent nutrient stress trigger was required to initiate the accumulation of the biodiesel precursor triacylglyceride, unlike other documented algal strains. A follow-up to this project demonstrated that the microalga C. gracilis may utilize light intensity as a trigger for lipid production. A major difficulty in the production of biofuels from microorganisms is the expensive process of dewatering, drying, and extracting the lipid compounds from the cells. As part of this research, a process has been developed that allows for lipid extraction to occur in the presence of water at a point as low as 2 percent solids or 98 percent water. This process utilizes a single organic solvent that mixes well with microbial lipids, but poorly with water allowing for efficient extraction of lipids and fast solvent to water separation. This process greatly decreases the cost of the microbial biofuels production associated with the removal of water from cell slurries. Triacylglycerides and fatty alcohols are oleochemicals that are commonly used in industrial, pharmaceutical, and consumable processes. A predicted fatty acyl CoA reductase enzyme was cloned into an E. coli vector, expressed, characterized and shown to be active as a dual reductive enzyme reducing a fatty acyl CoA to its respective fatty alcohol, constituting the first enzyme of this type discovered in a bacterium. The process of triacylglyceride production in microbes is fairly well understood; however, the process that regulates this production has not yet been fully explored. As part of this research, the model yeast organism, Yarrowea lipolytica, is utilized to identify essential genes for citrate transport that if removed could result in increasing triacylglyceride production in vivo.



Included in

Biochemistry Commons