Common plant holds key to healthier oil, greener fuel
AgBioResearch scientist leads effort to find new sources of plant oils that produce higher value food crops and bioproducts.
September 11, 2012
A plant that is common in residential landscapes and is prevalent on the MSU campus, called burning bush or Euonymus alatus, because it turns brilliant red in the fall, may help researchers find new sources of oil.
MSU University Distinguished Professor and AgBioResearch scientist John Ohlrogge has spent a good part of his career studying oilseed crops to help create products for the chemical industry, including plastics, polymers and oils.
"If we can create plants that produce more oil or oil with special properties, it gives everyone more options," he said. "Farmers can grow higher value crops, and manufacturers will have alternatives to crude oil."
For the past several years, Ohlrogge has been working with MSU plant biology research associate Timothy Durrett and visiting plant biology professor Michael Pollard, both with the Great Lakes Bioenergy Research Center, to isolate a useful gene from the seeds of the burning bush plant.
"Dr. Pollard realized that the burning bush seeds produce an unusual oil that might have a number of valuable uses," Ohlrogge said. "The special component of these oils is a group of compounds called acetyl glycerides, or acTAGs. Though acTAGS are related to vegetable oils that are the basis of the world's oilseed industry, they have different characteristics – including lower viscosity (i.e., a thinner oil)."
Despite this special oil production, burning bush isn't a suitable oil crop, so the scientists set out to isolate a gene from burning bush that is responsible for the production of acTAGs. Pollard first studied the biochemistry of the seeds to understand what type of enzyme was involved in this biosynthesis. With this information, Durrett used new DNA sequencing technology to identify the gene responsible for the plant's production of the novel, high-quality oil.
From the DNA information, Durrett was able to identify the correct gene. To prove that the gene could be used in other plants, he inserted the burning bush gene into Arabidopsis – common mustard weed and a cousin of canola – and succeeded in producing acTAGs in the seeds of the transgenic plants.
"The high viscosity of most plant oils prevents their direct use in diesel engines, so the oil must be chemically converted to biodiesel," Durrett said. "The lower viscosity acTAGs could possibly be used as a direct-use biofuel for some diesel engines." The acTAGs also are expected to perform better at low temperatures than regular vegetable oils, and that may also make them suitable for conversion into diesel fuel.
In addition to possible use as fuel, the acTAGs also have potential in the food industry. Because acTAGs contain fewer calories than other vegetable oils, they may be able to be used as a reduced-calorie food oil.
Durrett is now working to boost the amount of acTAGs produced by the modified Arabidopsis. Purity levels have been as high as 70 percent. "However, although Arabidopsis is an ideal model oilseed plant for genetics and proof of concept studies, its small size precludes it from being useful for scale up to produce the larger amounts of oil we will need for future studies on potential end uses," Pollard said.
So, the researchers are also applying the technology to larger oilseeds that can be readily grown and harvested in the field. This will allow for the production of greater amounts of oil enriched in acetyl glycerides. As with most research, it will take time to transform the plants, select the best transformants in terms of oil composition, and grow out the plants through several generations.
However, Pollard sees the potential. "With the basic genetics defied and the technical risk greatly reduced, the way is open to produce and assess this novel oil in food and nonfood applications."