Designing jet fuels of the future

Date posted: February 3, 2012

Drs. Heike Sederoff and Amy GrundenRoger Winstead photoDrs. Heike Sederoff and Amy Grunden look to extremophile genes to enhance oil production in marine algae and an oilseed crop.

Using micro-organisms able to survive in some of the most extreme environments on Earth, two CALS researchers are working to turn plants and algae into oil-producing factories efficient enough to help solve the problem of the world’s diminishing petroleum reserves.

Drs. Amy Grunden and Heike Sederoff have spent the past two years working on ways to make the microscopic marine algae Dunaliella produce more fatty acids that can be processed into fuels, and they recently won a grant to find ways to make camelina, an oilseed crop, more suitable for North Carolina’s growing conditions.

With federal stimulus funding awarded through the National Science Foundation, Grunden, associate professor in the Department of Microbiology, and Sederoff, an associate research professor in the Department of Plant Biology, have worked for two years with collaborators in the College of Engineering to find ways to make Dunaliella an economically viable biofuel source.

Algae are seen as promising fuel sources because they produce oil quickly and can be grown in areas unsuitable for agriculture. Marine algae are of particular interest because they grow in saltwater and therefore won’t compete for freshwater supplies so valuable to people, businesses and food production.

The researchers chose to focus on Dunaliella because it can double its mass every 30 hours; because it’s already being commercially produced for food for farm-raised salmon and shrimp; and because it has a cell membrane but no cell wall, which makes it easier to extract oils from the cells.

While the engineers focus on how to extract oils and convert them into fuel that can be used in place of conventional jet fuels, plant biologist Dr. JoAnn Burkholder studies different Dunaliella species to see which work best under various growth conditions.

At the same time, Grunden and Sederoff are genetically modifying Dunaliella so that it turns more sunlight and carbon dioxide into fatty acids. Algae produce oil mostly when they are stressed – when they have enough carbon dioxide and light but not enough nitrogen.

When algae are deprived of nitrogen, they store carbon in the form of oils that can be used when enough nitrogen is available. But in this state, the algae don’t grow.

Rather than inhibiting algae growth, Grunden and Sederoff hope to trick the algae into producing more oils by inserting synthetic genes derived from lipid biosynthesis in the bacteria Chromohalobacter salexigens. This bacterium is an extremophile that, like Dunaliella, can grow in high salt. The idea, Grunden says, is that the algae won’t necessarily be able to turn off the bacterial lipid synthesis genes.

“So what we are trying to do is actually put in a fatty acid pathway from a high-salt bacteria to try to force more of the carbon into lipid production,” she says. “So we are giving it, basically, an extra pathway to make lipids with.

“We hope they at least double the oil production,” she says. “And if this works, I think that’s a realistic goal.”

As Grunden and Sederoff work to boost Dunaliella’s oil production, they are also looking at ways to modify the algae so that at the same time it produces oil, it can produce enzymes that can be used in industrial processes under certain conditions. Good examples, they say, are enzymes that work in laundry detergents to remove oil stains in clothes washed either in hot or cold water.

A new North Carolina company, AvJet Biotech Inc. of Pinehurst, has licensed the technology that the scientists are developing. The company’s chief executive officer Don Evans calls the extremozymes Grunden and Sederoff are working on “high-value products which (can) contribute to increased productivity and product enhancement in many industries.” Avjet Biotech has made promising contacts, he says, with two leading manufacturers who are interested in the developments.

Meanwhile, Grunden and Sederoff are just beginning a $3.7 million U.S. Department of Energy-funded project involving camelina. Once used to make lamp oil, this relative of canola is now seen as a promising biofuel feedstock.

“Camelina-derived jet fuel is liquid at cold temperatures, in contrast to ethanol,” Sederoff says, so the oilseed crop is considered a possible replacement for petroleum-based fuels used to power aircraft. The U.S. Air Force has successfully tested fuel from camelina in a jet, and the first transatlantic flight powered by a camelina-based biofuel took place last summer.

Growers in some northern states have begun producing camelina for biofuel, and one North Carolina grower, with the help of North Carolina Cooperative Extension, grew a winter crop last year. CALS scientists also tested the crop and included information about it at a May 2011 canola field day at the College’s Williamsdale Farm in Duplin County.

One of the things that makes camelina attractive, Sederoff says, is that it can grow on marginal soils and requires little water and little fertilizer. But it’s not as productive as corn, and it doesn’t do well in the kind of heat found in North Carolina, she adds.

Sederoff and Grunden hope to get around those drawbacks through genetic engineering. Camelina is a relative of Arabidopsis thaliana, which is one of the world’s most-studied plants and the first to have its entire genome sequenced. It’s also used to understand genetic mechanisms in plants.

Grunden and Dr. Wendy Boss, a CALS plant biologist, previously showed that it was possible to transfer genes from the extremophile microbe Pyrococcus furiosus into Arabidopsis, making the plant better able to tolerate warmer temperatures. Grunden wants to try the same thing with camelina.

Meanwhile, Dr. Deyu Xie, a “Jet Camelina” team member and associate professor in the Department of Plant Biology, will focus on taking certain genes out of citrus and putting them into camelina so that the camelina can produce limonene. Limonene is a terpene, a class of chemicals needed in jet fuel production to prevent leaks in tank linings and engine gaskets.

Grunden and Sederoff are excited about the camelina project because it could help fill three important needs – the need for jet fuels that aren’t petroleum-based, the need for new markets for North Carolina farmers and the need for lower-cost animal feeds that will help the state’s large hog industry compete with the Midwest, where corn and other grains are more plentiful and less expensive.

They are working with faculty members from a number of CALS departments: Dr. Ron Qu from the Department of Crop Science will help generate the transgenic camelina; Xie will perform the metabolic analyses of the new camelina lines; Dr. Matt Veal from the Department of Biological and Agricultural Engineering will help improve and test production practices; and Dr. Kelly Zering from the Department of Agricultural and Resource Economics will help determine what will make the crop profitable for farmers.

To convert the oil and terpenes extracted from camelina into jet fuel that can be used by the U.S. Air Force, the team includes Drs. Henry Lamb and William Roberts from the College of Engineering, who have developed new technologies for this process.

The team will also work with Avjet Biotech and with N.C. hog industry leaders who want to know if meal made with ground camelina – a byproduct of the oil extraction process – could become a lower-cost alternative to current feed formulations.

“This project bridges the basic and applied sciences and is an example of what the College does best,” Grunden says. “We are really excited about the potential it has to not only make an economic impact here in North Carolina but also to address one of the biggest challenges that is currently facing the world – which is fuel production and the limits of existing petroleum.”

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