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Environment

Small Business Award

by Stephen K. Ritter
October 16, 2014 | A version of this story appeared in Volume 92, Issue 42

Amyris, Emeryville, Calif., for developing farnesane as a renewable drop-in replacement for petroleum-based diesel and jet fuel

First-generation biofuels ethanol and biodiesel (fatty acid methyl esters) provide a green alternative to petroleum-derived fuels to help reduce greenhouse gas emissions. But the fuels have technical issues that limit their use—they can’t completely replace fossil fuels on their own. For example, ethanol has lower energy per volume than petroleum fuels and it’s not fully compatible with existing vehicles and fuel-distribution infrastructure.

Amyris has taken a step toward the next generation of biofuels by engineering baker’s yeast strains to convert sugar into the 15-carbon alkene β-farnesene instead of ethanol. The technology is built on synthetic biology concepts originating in Jay D. Keasling’s laboratory at the University of California, Berkeley.

GREEN FLIGHT
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Credit: Amyris
Amyris partnered with Brazilian airline GOL on the first commercial airline flight with farnesane jet fuel on July 30, a trip from Orlando, Fla., to Sao Paulo.
Photo shows a seat on the Brazilian airline GOL.
Credit: Amyris
Amyris partnered with Brazilian airline GOL on the first commercial airline flight with farnesane jet fuel on July 30, a trip from Orlando, Fla., to Sao Paulo.

Amyris scientists sifted through metabolic pathways in bacteria that lead to hydrocarbons, homing in on the isoprenoid pathway that produces farnesene and other terpenes. The researchers then plugged farnesene-producing genes into yeast, which are more robust for industrial fermentations than bacteria, explains Joel Velasco, a senior vice president at Amyris. The company also developed an economical method to hydrogenate the multiple unsaturated bonds in farnesene to make farnesane, which can serve as a drop-in replacement for petroleum diesel or vegetable-oil-based biodiesel. Farnesane also can serve as an ingredient for making jet fuel. As a long-chain hydrocarbon, the molecule has a much higher energy density than ethanol, Velasco says, and its branched structure offers good cold-weather fuel performance.

“This innovation by Amyris addresses renewability and reduction in greenhouse gases while also delivering improved performance in engine operation and eliminating other emissions such as sulfur dioxide,” comments David J. C. Constable, director of the American Chemical Society’s Green Chemistry Institute, which helps administer the awards process with EPA. “Sugar is unquestionably the new carbon source for many future chemicals and fuels, and its direct fermentation to farnesene is a great model for other companies to emulate.”

Amyris operates a biorefinery in Brazil producing farnesene from sugarcane syrup, Velasco says. The company also has a business venture with French oil company Total to produce and market farnesane for diesel and jet fuel, which is being used in buses in Brazil and commercial aircraft globally.

Besides biofuels, farnesene is being used as a biobased feedstock to make ingredients for lubricants, cosmetics, tire rubber, and more, Velasco says. With farnesene production on the upswing and production cost coming down, the company anticipates starting to turn a profit for the first time by the end of this year. “Farnesene is a nice building block hydrocarbon for us,” Velasco says. “When we first looked at farnesene, it was a dream on a PowerPoint. And now it’s a reality.”

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