Science & Technology

Engineered E. coli Produces Key Precursors of High-Octane Biofuels

By rerouting the metabolic pathway that makes fatty acids in E. coli micro organism like these, Wyss Institute researchers have devised a brand new technique to produce a gasoline-like biofuel. Credit score: Wyss Institute, Harvard College

A brand new research from scientists on the Wyss Institute particulars engineered micro organism that may make key precursors of high-octane biofuels.

New traces of engineered micro organism can tailor-make key precursors of high-octane biofuels that might in the future substitute gasoline, scientists on the Wyss Institute for Biologically Impressed Engineering at Harvard College and the Division of Programs Biology at Harvard Medical College report in the June 24 online edition of Proceedings of the National Academy of Sciences.

The identical traces can even produce precursors of prescription drugs, bioplastics, herbicides, detergents, and extra.

“The large contribution is that we have been in a position to program cells to make particular gas precursors,” stated Pamela Silver, Ph.D., a Wyss Institute Core College member, Professor of Programs Biology at Harvard Medical College, and senior creator of the research.

New biofuels are wanted for automobiles and different autos. Ethanol, the preferred biofuel available on the market, packs solely two-thirds the power of gasoline, and ethanol-containing fuels additionally corrode pipes, tanks, and different infrastructure used to move and retailer gasoline. In the meantime, burning gasoline itself provides large quantities of carbon dioxide to the ambiance, and depends on the world’s dwindling provide of oil.

But gasoline produces extra power than present biofuels when burned in an inner combustion engine, and stays liquid in temperatures starting from a Texas warmth wave to a North Dakota chilly snap. Furthermore, lots of of hundreds of thousands of automobiles worldwide are constructed to run on it.

Silver and her workforce are in search of new methods to make gasoline-like biofuels that could possibly be saved at fuel stations and used to gas the automobiles we have already got. To develop these, they enlisted the enduring laboratory bacterium E. coli to assist make gasoline precursors referred to as fatty acids—energy-packed molecules containing chains of carbon atoms flanked with hydrogen atoms that may be simply transformed into fuels.

Particularly, they’re specializing in medium-chain fatty acids—these with chains between 4 and 12 carbons lengthy. Fatty acids with shorter chains don’t retailer sufficient power to be good fuels they usually are inclined to vaporize simply, whereas these with chains longer than 12 carbons are too waxy. However medium-length fatty acids are simply the fitting size to be reworked into an energy-packed liquid gas for internal-combustion engines.

At this time oil refineries produce medium-chain-length compounds from crude oil. However “as a substitute of utilizing petroleum merchandise, you may have microbes or different dwelling organisms do it for you,” Silver stated.

To perform that, Joe Torella, Ph.D., and Tyler Ford, Harvard Medical College Programs Biology graduate college students in Silver’s laboratory and the paper’s lead coauthors, tweaked an E. coli metabolic pathway that produces fatty acids. Particularly, they mass-produced an eight-carbon fatty acid referred to as octanoate that may be transformed into octane.

On this pathway, carbon from sugar, which the bacterium eats, flows by way of the pathway like a river, rising longer because it flows. Downstream, it exits as a long-chain fatty acid.

Torella and Ford first partially dammed the river and constructed an irrigation ditch utilizing a drug that blocks enzymes that stretch fatty-acid chains. This precipitated medium-chain fatty acids to pool behind the dam, whereas nonetheless permitting sufficient of the river to circulation by for the micro organism to construct their membranes and keep alive. The technique elevated octanoate yields, however the drug is just too costly for the method to be scaled up.

For that purpose, the scientists tried a second technique that could possibly be scaled up extra readily. They let the cells develop up, then dammed the river utilizing a genetic trick. In addition they genetically altered a second enzyme that usually builds long-chain fatty acids such that it extends fatty acids to eight carbons and not.

This two-pronged technique—plus another genetic nips and tucks to maintain the river from being diverted in different methods–gave the scientists the very best yields of octanoate but reported.

“We discovered if we cease up the river—if we sluggish fatty acid elongation—we inspired the creation of medium-chain fatty acids,” Torella stated.

“Sustainability is one of the most important issues we face as we speak, and growing potent biofuels to exchange gasoline is a serious problem within the subject,” stated Don Ingber, M.D., Ph.D., Wyss Institute Founding Director. “Utilizing ingenious synthetic-biology methods to engineer microbes in order that they’ll produce octane, Pam’s workforce has taken a large step towards assembly this problem.”

Subsequent, the scientists plan to engineer E. coli to transform octanoate and different fatty acids into alcohols, potential gas molecules themselves, and only one chemical step away from octane.

This work was funded by the Division of Vitality’s Superior Analysis Challenge Company-Vitality (ARPA-E), by the Nationwide Science Basis, and by the Wyss Institute for Biologically Impressed Engineering. Along with Silver, Torella, and Ford, the analysis workforce included Scott Kim and Amanda Chen, college students on Silver’s workforce, and Jeffrey Method, Ph.D., a Senior Employees Scientist on the Wyss Institute.

Publication: Joseph P. Torella, et al., “Tailor-made fatty acid synthesis through dynamic management of fatty acid elongation,” PNAS, June 24, 2013; doi: 10.1073/pnas.1307129110

Picture: Wyss Institute, Harvard College

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