Date of Award:

5-2013

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Chemistry and Biochemistry

Committee Chair(s)

Lance C. Seefeldt

Committee

Lance C. Seefeldt

Committee

Scott A. Ensign

Committee

Joan M. Hevel

Committee

Sean J. Johnson

Committee

Jixun Zhan

Abstract

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 (fat) content of cellular feedstocks, improve extraction efficiencies of lipids, and to understand the pathways involved in the production of fatty alcohols and triacylglycerides, compounds commonly used in many industrial processes, from microbial feedstocks. This work has been done in an attempt to increase the overall economic viability of microbial biofuels production.

The production of biofuels from microalgae used as a feedstock allows for the conversion of a waste gas, carbon dioxide, into a renewable biofuels source. As part of this research, the diatom Cheatoceros gracilis, was grown at small and large scale to determine optimal growing conditions. It is generally accepted that an essential nutrient must be withheld from the organism to cause them to produce the fat compound triacylglyceride, however, this trigger does not appear to be present with this microalgae. A follow-up to this project demonstrated that high intensity light may be the trigger that this organism requires for fat production.

A major difficulty in the production of biofuels from microorganisms including algae, yeast, and bacteria 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. This process utilizes a single organic solvent (exe. chloroform) 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 microbial biofuels production associated with the removal of water from microbial feedstocks.

Triacylglycerides and fatty alcohols are oleochemicals (chemicals that are derived from a biological source) that are commonly used in industrial, pharmaceutical, and consumable processes. The understanding of how these chemicals are produced in different microorganisms was a focus as part of this work. An enzyme has been found in the bacterium Marinobacter aquaeolei VT8 that is responsible for producing fatty alcohols. This is the first enzyme of this type found in a bacterial organism.

The production of triacylglycerids in microorganisms is fairly well understood, however, the control of the cellular machinery that produces triacylglycerides has not been fully explored. As part of this research, the model yeast organism, Yarrowea lipolytica, is used to work toward determining genes that are necessary for citrate, a triacylglyceride precursor in the cell, transport. The removal or chemical manipulation of these genes/enzymes should result in an increase in microbial lipid production. This understanding could thus be used to increase the overall lipid production of a microbial feedstock for biofuels production.

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