Mark C. Politz 

Mark C. Politz

Degree Program: Chemical and Biological Engineering
Faculty Supervisor: Brian Pfleger
Phone: (608) 262-8177


Current Research

As the world supply of oil is dwindling, it is necessary to find alternative sources of liquid transportation fuels. Lauric acid, a saturated medium chain free fatty acid (FFA), is a precursor to low melting point biodiesels and may be produced biologically from renewable feedstocks. To overproduce this compound, a strategy was devised whereby a heterologous thioesterase (BTE) specific to the desired chain length was expressed in Escherichia coli. This resulted in a low yield of free fatty acids (~20% of the maximum theoretical). To identify the destination of the carbon used by the thioesterase-expressing strain, chemostat runs were performed and the fraction of carbon present in FFA, biomass, and CO2 was determined. This set of experiments demonstrated that a large fraction of total carbon is being diverted toward the production of CO2, likely through the TCA cycle. Unfortunately, direct manipulation of the levels of TCA cycle enzymes by altering the chromosome would result in a growth defect, while constructing the required knockouts would be lethal. In order to ameliorate this problem while maintaining suitable growth rates, a regulatory strategy that does not require direct manipulation of the chromosome is required. Fortunately, a class of DNA binding proteins known as transcription activator-like effectors (TALEs) can be designed to bind any desired DNA sequence, allowing expression of essential genes to be tuned in an inducible manner without chromosomal manipulation. Reporter gene assays confirmed that TALEs may be used in this manner in E. coli. Future work will use TALEs to knock down, but not knock out, genes implicated in the overproduction of CO2 to boost yields of FFA.

Abstract (PDF)





Biochemistry Department
433 Babcock Drive
Madison, WI 53706-1544

Brian Fox, Director