This is a very promising
development. It identifies a specific naturally produced molecule as a prospective
diesel fuel replacement and then takes it from there to establish optimized fermentation
production. It is still a ways away from
commercial production but this is surely the pathway to converting agricultural
waste into D2 on the farm itself.
Even it such fuel were in need of
polishing work somewhere else, the biomass itself would be spent the volumes
available then to deal with would be rather small.
The take home today is that it is
likely becoming practical to convert biowaste directly into D2.
In the present rush to
transportation electrification, it is easily overlooked that electrification is
unlikely to ever apply to long haul transport and as critically agricultural
energy needs. For this, D2 is actually an
excellent protocol. Therefore replacing
D2 from hydrocarbon sources with D2 produced from agricultural waste sources
and even wood waste is very desirable.
We can already see electrification
sweeping the country and actually the globe over the next decade. This will slash oil demand just as massive
fresh oil supplies are also coming on stream.
Converting the D2 stream to agro carbon will cut demand hugely again.
Joint BioEnergy Institute Scientists Identify New Microbe-Produced
Advanced Biofuel as an Alternative to Diesel Fuel
SEPTEMBER 27, 2011
Lynn Yarris (510) 486-5375 lcyarris@lbl.gov
News Release
Commercial trucks in the U.S.
Researchers with the U.S Department of Energy (DOE)’s Joint BioEnergy
Institute (JBEI) have identified a potential new advanced biofuel that could
replace today’s standard fuel for diesel engines but would be clean, green,
renewable and produced in the United States. Using the tools of synthetic
biology, a JBEI research team engineered strains of two microbes, a bacteria
and a yeast, to produce a precursor to bisabolane, a member of the terpene
class of chemical compounds that are found in plants and used in fragrances and
flavorings. Preliminary tests by the team showed that bisabolane’s properties
make it a promising biosynthetic alternative to Number 2 (D2) diesel fuel.
“This is the first report of bisabolane as a biosynthetic
alternative to D2 diesel, and the first microbial overproduction of bisabolene
in Escherichia coli and Saccharomyces cerevisiae,” says Taek
Soon Lee, who directs JBEI’s metabolic engineering program and is a project
scientist with Lawrence Berkeley National Laboratory (Berkeley Lab)’s Physical
Biosciences Division. “This work is also a proof-of-principle for advanced
biofuels research in that we’ve shown that we can design a biofuel target,
evaluate this fuel target, and produce the fuel with microbes that we’ve
engineered.”
Lee is the corresponding author of a paper reporting this research in
the journal Nature Communications entitled “Identification and
microbial production of a terpene-based advanced biofuel.” Pamela Peralta-Yahya
is the lead author of this paper. Other co-authors are Mario Ouellet, Rossana
Chan, Aindrila Mukhopadhyay and Jay Keasling
The rising costs and growing dependence upon foreign sources of
petroleum-based fuels, coupled with scientific fears over how the burning of these
fuels impacts global climate, are driving the search for carbon-neutral
renewable alternatives. Advanced biofuels – liquid transportation fuels derived
from the cellulosic biomass of perennial grasses and other non-food plants, as
well as from agricultural waste – are highly touted for their potential to
replace gasoline, diesel and jet fuels. Unlike ethanol, which can only be used
in limited amounts in gasoline engines and can’t be used at all in diesel or
jet engines, plus would corrode existing oil pipelines and tanks, advanced
biofuels are drop-in fuels compatible with today’s engines, and delivery and
storage infrastructures.
“We desperately need drop-in, renewable biofuels that can directly
replace petroleum-derived fuels, particularly for vehicles that cannot be
electrified,” says co-author
Keasling, CEO of JBEI and a leading authority on advanced biofuels. “The
technology we describe in our Nature Communications paper is a
significant advance in that direction.”
From left, Pamela Peralta-Yahya, Taek Soon Lee and Mario Ouellet were
key members of a team at the Joint BioEnergy Institute (JBEI) that demonstrated
the potential of the chemical compound bisabolane to replace D2 diesel. (Photo
by Roy Kaltschmidt, Berkeley
JBEI is one of three Bioenergy Research Centers established by the
DOE’s Office of Science in 2007. Researchers at JBEI are pursuing the
fundamental science needed to make production of advanced biofuels
cost-effective on a national scale. One of the avenues being explored is
sesquiterpenes, terpene compounds that contain 15 carbon atoms (diesel fuel
typically contains 10 to 24 carbon atoms).
“Sesquiterpenes have a high-energy content and physicochemical
properties similar to diesel and jet fuels,” Lee says. “Although plants are the
natural source of terpene compounds, engineered microbial platforms would be
the most convenient and cost-effective approach for large-scale production of
advanced biofuels.”
In earlier work, Lee and his group engineered a new mevalonate pathway
(a metabolic reaction critical to biosynthesis) in both E. coli and S.
cerevisiae that resulted in these two microorganisms over-producing a
chemical compound called farnesyl diphosphate (FPP), which can be treated with
enzymes to synthesize a desired terpene. In this latest work, Lee and his group
used that mevalonate pathway to create bisabolene, which is a precursor to
bisabolane.
“We proposed that the generality of the microbial FPP overproduction
platforms would allow for the biosynthesis of sesquiterpenes,” Lee says.
“Through multiple rounds of large-scale preparation in shake flasks, we were
able to prepare approximately 20 milliliters of biosynthetic bisabolene, which
we then hydrogenated to produce bisabolane.”
This diagram shows the steps for synthesizing bisabolane, an
alternative to D2 diesel, from the chemical hydrogenation of bisabolene, which
is metabolized in microbes via an engineered mevalonate pathway. (Image from
Pamela Peralta-Yahya )
When they began this work, Lee and his colleagues did not know
whether bisabolane could be used as a biofuel, but they targeted it on the
basis of its chemical structure. Their first step was to perform fuel property
tests on commercially available bisabolene, which comes as part of a
mixture of compounds. Convinced they were onto something, the researchers then
used biosynthesis to extract pure biosynthetic bisabolene from microbial
cultures for hydrogenation into bisabolane. Subsequent fuel property tests on
the bisabolane were again promising.
“Bisabolane has properties almost identical to D2 diesel but its
branched and cyclic chemical structure gives it much lower freezing and cloud
points, which should be advantageous for use as a fuel,” Lee says. “Once we
confirmed that bisabolane could be a good fuel, we designed a mevalonate
pathway to produce the precursor, bisabolene. This was basically the same
platform used to produce the anti-malarial drug artemisinin except that we
introduced a terpene synthase and further engineered the pathway to improve the
bisabolene yield both in E. coli and yeast.”
Lee and his colleagues are now preparing to make gallons of bisabolane
for tests in actual diesel engines, using the new fermentation facilities at Berkeley Emeryville ,
California
“Once the complete fuel properties of hydrogenated biosynthetic
bisabolene can be obtained, we’ll be able to do an economic analysis that takes
into consideration production variables such as the cost and type of feedstock,
biomass depolymerization method, and the microbial yield of biofuel,” Lee says.
“We will also be able to estimate the impact of byproducts present in the
hydrogenated commercial bisabolene, such as farnesane and aromatized
bisabolene.”
Ultimately, Lee and his colleagues would like to replace the chemical
processing step of bisabolene hydrogenation with an alkene reductase enzyme
engineered into the E.coli and yeast so that all of the chemistry is
performed within the microbes.
“Enzymatic hydrogenation of this type of molecule is a very challenging
project and will be a long term goal,” Lee says. “Our near-term goal is to
develop strains of E.coli and yeast for use in commercial-scale
fermenters. Also, we will be investigating the use of sugars from biomass as a
source of carbon for producing bisabolene.”
# # #
JBEI is a scientific partnership led by Lawrence
Berkeley National Laboratory (Berkeley
Lab) and including the Sandia National Laboratories, the UC campuses of
Berkeley and Davis, the Carnegie Institution for Science, and the Lawrence Livermore
Lawrence Berkeley National Laboratory addresses the world’s most
urgent scientific challenges by advancing sustainable energy, protecting
human health, creating new materials, and revealing the origin and fate of
the universe. Founded in 1931, Berkeley University of California
manages Berkeley Lab for the U.S.
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