application WO/2007/136762; Friedman and Rude, patent application WO 2008/113041).
Here, the overproduced free fatty acids were extracted from culture and catalytically
decarboxylated to alkanes. Coupling the microbial fermentation to a scalable existing
chemical technology precludes the need to heterologously express a new in vivo pathway to
convert the fatty acids to a useful liquid product, which even if properly balanced could
reduce the overall yield of fatty acids owing to increased cellular metabolic burdens.
Decarboxylation is a preferable conversion because alkanes have more desirable properties,
such as higher energy density and lower viscosity, than corresponding esters that would be
produced by catalytic esterification of fatty acids. Furthermore, the final medium chain
alkane product can be recycled for reuse as an extractant of fatty acids from the culture
medium and as the solvent for the catalytic decarboxylation. E. coli has been selected
because of its ease of genetic manipulation, well-understood physiology (especially with
regards to fatty acid biosynthesis), and rapid growth rate. Because all prokaryotic and
eukaryotic organisms possess the ability to produce fatty acids as part of membrane lipid
biosynthesis, small modifications to the methods presented should be broadly applicable to
other industrial microorganisms.