http://www.examiner.com/article/biodiesel-produced-on-demand-by-modified-e-coli-bacteria
Biodiesel produced on demand by modified E. coli bacteria
Science April 23, 2013
By: Andrew Kincaid
Science Daily reported yesterday that a team from the University of
Exeter, supported by Shell, has developed a method to make E. coli
bacteria produce diesel fuel on demand.
Biodiesels generally have a disadvantage, in that they differ chemically
from petroleum fuels in some ways. So, they often have to be blended
with petroleum products. However, the fuel produced by the Exeter team's
modified E. coli bacteria is a so-called "drop-in" fuel, which means
that it need not be modified. It is, for all intents and purposes, the
same as diesel derived from fossil fuels. That means it can be used in
existing vehicles and infrastructure, making it an attractive potential
alternative to traditional diesel.
E. coli has been used in commercial production before, especially in the
pharmaceutical industry. The bug converts sugar into fats that it uses
in its cell membranes; put short, the researchers hijacked the process
in order to produce hydrocarbons for fuel. It remains to be seen whether
the process can be commercialized, but if the new fuel can be
manufactured in a large scale, it could give a carbon neutral
alternative to traditional fuels, which could help cut carbon emissions
and meet growing energy demand.
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http://www.scientificamerican.com/article.cfm?id=gut-microbe-makes-diesel-biofuel
Gut Microbe Makes Diesel Biofuel
Reconfiguring the genetics of the food pathogen E. coli produces
hydrocarbons indistinguishable from those burned in trucks
By David Biello
Welding bits and pieces from various microbes and the camphor tree into
the genetic code of Escherichia coli has allowed scientists to convince
the stomach bug to produce hydrocarbons, rather than sickness or more E.
coli. The gut microbe can now replicate the molecules, more commonly
known as diesel, that burn predominantly in big trucks and other
powerful moving machines.
"We wanted to make biofuels that could be used directly with existing
engines to completely replace fossil fuels," explains biologist John
Love of the University of Exeter in England, who led the research into
fuels. "Our next step will be to try to develop a bacterium that could
be deployed industrially." Love’s work was published April 22 in
Proceedings of the National Academy of Sciences.
That means harnessing E. coli's already high tolerance for harsh
conditions, such as the high acidity and warmth of the human digestive
tract. That hardiness also seems to be helping the bacterium survive its
own production of such longer-chain hydrocarbons, which could have
proved toxic to the microbes, in the way brewer's yeast cells are killed
off by the alcohol they ferment. The engineered E. coli used genetic
code from the insect pathogen Photorhabdus luminescens and from the
cyanobacterium Nostoc punctiforme as well as soil microbe Bacillus
subtilis to make the fuel molecules from fatty acids, along with a gene
from the camphor tree—Cinamomum camphora—to cut the resulting
hydrocarbon to the right length.
The E. coli are currently fed on sugar and yeast extract, which suggests
that the resulting fuel would be expensive compared with the kind
refined from oil found in the ground. "We are hopeful that we could
change their diet to something less valuable to humanity," Love
suggests. "For example, organic wastes from agriculture or even sewage."
Exactly how the E. coli microbes expel the diesel fuel molecules is
unknown at this point. The researchers have found them floating in the
growth medium, suggesting the microbes are somehow secreting the
hydrocarbons from their cells once produced. "We don't know how they get
there yet," Love admits. But that may solve a problem posed to other
would-be biofuels produced in microbes; algal oils have proved difficult
to extract cheaply and effectively from inside the algae themselves,
among other challenges.
Besides a better grasp of the process itself, fine-tuning the genetic
engineering may one day yield other useful hydrocarbons, such as jet
fuel or even gasoline (a short-chained hydrocarbon). Similar work at the
University of California, Berkeley, has tinkered with E. coli genetics
to allow the bacteria to digest the inedible parts of plants known as
cellulose and turn them into microbial diesel that can be used in place
of fossil-fuel diesel or other useful hydrocarbons. And E. coli has been
harnessed in the past to make specialty oils for cosmetics; the company
Amyris makes the moisturizing oil known as squalane from E. coli fed
sugarcane and grown in vats in Brazil. The synthetic biologists at
Amyris have also coaxed yeast to produce the antimalarial drug
artemisinin, a technology that is currently being commercialized with
drugmaker Sanofi.
Regardless, industrial-scale fuel production from microbes remains a
much tougher proposition than making specialty oils or medicines, given
the low cost and high volumes required to compete with the fuels made
from fossil sources. "Fuel is actually a lot cheaper than artemisinin,
so it has to be made in significantly larger quantities," Love notes.
"That in itself is a challenge."
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