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Synthetic Biology

[Due to the increasing size of the archives, each topic page now contains only the prior 365 days of content. Access to older stories is now solely through the Monthly Archive pages or the site search function.]

New engineered metabolic pathways in yeast enable efficient fermentation of xylose from biomass

March 05, 2015

Researchers with the Energy Biosciences Institute (EBI), a partnership that includes Berkeley Lab and the University of California (UC) Berkeley, have introduced new metabolic pathways from the fungus Neurospora crassa into the yeast Saccharomyces cerevisiae to increase the fermentative production of fuels and other chemicals from biomass. An open access paper on the work is publised in the journal eLife.

While S. cerevisiae is the industry mainstay for fermenting sugar from cornstarch and sugarcane into ethanol, it requires substantial engineering to ferment sugars derived from plant cell walls such as cellobiose and xylose. The new metabolic pathways enable the yeast to ferment sugars from both cellulose (glucose) and hemicellulose (xylose)—the two major families of sugar found in the plant cell wall—efficiently, without the need of environmentally harsh pre-treatments or expensive enzyme cocktails.

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Engineered yeast produces ethanol from three important cellulosic biomass components simultaneously; higher yields, lower cost

February 11, 2015

A team led by researchers from the University of Illinois at Urbana−Champaign has, for the first time, integrated the fermentation pathways of both hexose and pentose sugars from biomass as well as an acetic acid reduction pathway into one strain of the yeast Saccharomyces cerevisiae using synthetic biology and metabolic engineering approaches.

The engineered strain co-utilized cellobiose, xylose, and acetic acid to produce ethanol with a substantially higher yield and productivity than the control strains. The results showed the unique synergistic effects of pathway coexpression, the team reported in a paper in the journal ACS Synthetic Biology.

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Researchers discover bacteria could be rich source of terpenes

December 24, 2014

Researchers at Kitasato University in Japan, Brown University in the US, and colleagues in Japan have found that bacteria could be a rich source of terpenes—natural compounds common in plants and fungi that can be used to make drugs, food additives, perfumes, and other products, including advanced fuels (earlier post, earlier post).

Terpenes are responsible for the essential oils of plants and the resins of trees. Since the discovery of terpenes more than 150 years ago, scientists have isolated some 50,000 different terpene compounds derived from plants and fungi. Bacteria and other microorganisms are known to make terpenes too, but they’ve received much less study. The new research, published in an open access paper in the Proceedings of the National Academy of Sciences, shows that the genetic capacity of bacteria to make terpenes is widespread.

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DOE JBEI team boosts methyl ketone production from E. coli 160-fold; advanced biofuel or blendstock

December 02, 2014

In 2012, researchers at the US Department of Energy’s Joint BioEnergy Institute (JBEI) engineered Escherichia coli (E. coli) bacteria to overproduce from glucose saturated and monounsaturated aliphatic methyl ketones in the C11 to C15 (diesel) range from glucose. In subsequent tests, these methyl ketones yielded high cetane numbers, making them promising candidates for the production of advanced biofuels or blendstocks. (Earlier post.)

Now, after further genetic modifications of the bacteria, they have managed to boost the E.coli’s methyl ketone production 160-fold. A paper describing this work is published in the journal Metabolic Engineering.

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Researchers successfully engineer E. coli to produce renewable propane; proof-of-concept

September 03, 2014

Researchers from the University of Turku in Finland, Imperial College London and University College London have devised a synthetic metabolic pathway for producing renewable propane from engineered E. coli bacteria. Propane, which has an existing global market for applications including engine fuels and heating, is currently produced as a by-product during natural gas processing and petroleum refining. A paper on their work is published in Nature Communications.

The new pathway is based on a thioesterase specific for butyryl-acyl carrier protein (ACP), which allows native fatty acid biosynthesis of the Escherichia coli host to be redirected towards a synthetic alkane pathway. ​Although the initial yields were low, the team was able to identify and to add essential biochemical components in order to boost the biosynthesis reaction, enabling a the E. coli strain to increase propane yield, although the amounts are still far too low for commercialization.

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UGA-led team engineers bacterium for the direct conversion of unpretreated biomass to ethanol

June 03, 2014

A team led by Dr. Janet Westpheling at the University of Georgia has engineered the thermophilic, anaerobic, cellulolytic bacterium Caldicellulosiruptor bescii, which in the wild efficiently uses un-pretreated biomass—to produce ethanol from biomass without pre-treatment of the feedstock. A paper on the work is published in Proceedings of the National Academy of Sciences (PNAS).

In January, Dr. Westpheling and her colleagues reported in the journal Science their discovery that an enzyme (the cellulase CelA) from C. besciia can digest cellulose almost twice as fast as Cel7A, the current leading component cellulase enzyme on the market. (Earlier post.)

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Synthetic biology company launches JV to commercialize gas-to-liquids bioconversion; isobutanol first target

March 28, 2014

Synthetic biology company Intrexon Corporation has formed Intrexon Energy Partners (IEP), a joint venture with a group of external investors, to optimize and to scale-up Intrexon’s gas-to-liquids (GTL) bioconversion platform. IEP’s first target product is isobutanol for gasoline blending.

Intrexon’s natural gas upgrading program is targeting the development of an engineered microbial cell line for industrial-scale bioconversion of natural gas to chemicals, lubricants and fuels, as opposed to employing standard chemical routes. Intrexon says it has already achieved initial proof of concept with an engineered microbial host converting methane into isobutanol in a laboratory-scale bioreactor.

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Scientists synthesize first functional designer chromosome in yeast

An international team of scientists led by Dr. Jef Boeke, director of NYU Langone Medical Center’s Institute for Systems Genetics, has synthesized the first functional chromosome in yeast, an important step in the emerging field of synthetic biology—designing microorganisms to produce novel medicines, raw materials for food, and biofuels. A paper on the accomplishment is published in the journal Science.

Over the last five years, scientists have built bacterial chromosomes and viral DNA, but this is the first report of an entire eukaryotic chromosome built from scratch. Researchers say their team’s global effort also marks one of the most significant advances in yeast genetics since 1996, when scientists initially mapped out yeast’s entire DNA code, or genetic blueprint.

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Researchers progress with engineering E. coli to produce pinene for biosynthetic alternative to rocket fuel

March 16, 2014

Master.img-001
Energy density of petroleum-based fuels and advanced biofuels. Shown is the heating value of petroleum-based fuels (black) and advanced biofuels (green) as a function of density. Pinene dimers (red) have density and heating value similar to that of JP-10. Credit: ACS, Sarria et al. Click to enlarge.

Recent progress in engineering microbes has resulted in the production of biosynthetic alternatives to gasoline, diesel, and diesel precursors. However, the development of microbial platforms for the production of high-energy density fuels—i.e., tactical fuels for use in aircraft and aircraft-launched missiles—has lagged behind. Existing biosynthetic jet fuels lack the volumetric energy content required to replace high-energy density fuels such as the tactical fuels JP-10, tetrahydrodicy-clopentadiene, and RJ-5.

A team from Georgia Tech, University of California, Berkeley, and the Joint BioEnergy Institute at Lawrence Berkeley National Laboratory has now engineered Escherichia coli bacteria to produce pinene, the immediate precursor to pinene dimers, a biosynthetic alternative to JP-10. Although their work produced a significant increase in yield from earlier attempts, the yield will need to be some 26-times larger for commercial viability, they calculated.

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