It has long been known that certain types of bacteria are able to synthesize aliphatic hydrocarbons, which makes them promising sources of the enzymes needed to convert lignocellulose into advanced biofuels. However, until recently, little was known about the bacterial biosynthesis of non-isoprenoid hydrocarbons beyond a hypothesis that fatty acids are precursors. JBEI researchers in the Fuels Synthesis Division, which is headed by co-author Keasling, are using the tools of synthetic biology, and mathematical models of metabolism and gene regulation to engineer new microbes that can quickly and efficiently produce advanced biofuel molecules. E.coli is one of the model organisms being used in this effort because it is a well-studied microbe that is exceptionally amenable to genetic manipulation.
"We chose to work with M. luteus because a close bacterial relative was well-documented to synthesize alkenes and because a draft genome sequence of M. luteus was available," Beller says. "The first thing we did was to confirm that M. luteus also produces alkenes."
Beller and his colleagues worked from a hypothesis that known enzymes capable of catalyzing both decarboxylation and condensation should be good models for the kind of enzymes that might catalyze alkene synthesis from fatty acids. Using condensing enzymes as models, the scientists identified several candidate genes in M. luteus, including Mlut_13230. When expressed in E. coli together with the two adjacent genes - Mlut_13240 and 13250 - this trio of enzymes catalyzed the synthesis of alkenes from glucose. Observations were made both in vivo and in vitro.
"This group of enzymes can be used to make aliphatic hydrocarbons in an appropriate microbial host but the resulting alkenes are too long to be used d
|Contact: Lynn Yarris|
DOE/Lawrence Berkeley National Laboratory