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A Vegetable Oil for the Future?

Scientists have successfully found a way to produce an entirely new kind of vegetable oil.

Rare in nature and combining properties that don’t usually go together, the oil is made from acetyl glycerides and could lead to applications like a very low-calorie cooking oil and a biofuel that can go straight from the plant into your car.       

Scientists have known about this oil’s unique potential ever since the Department of Agriculture discovered it in the 1960s, researcher Michael Pollard at Michigan State University told Livescience.

But its origins from the seeds of the burning bush shrub, also called Euonymus alatus, an invasive species whose seed material contains molecules that resemble toxins, prevented anyone from making use of it.

Now, genetic engineering, in which the scientists inserted genes for making the unique fat into an Arabidopsis plant, has enabled scientists to reach a critical step in the pathway toward making this oil commercially available.

"We have a very good result now of the gene expressed in an Arabidopsis plant," Pollard said.

A direct-use biofuel

Virtually all vegetable oils are made from triglycerides, or long chains of hydrocarbons connected to an organic molecule called glycerol. In contrast, acetyl glycerides are made from medium chains of hydrocarbons connected to acetic acid, the primary ingredient in vinegar.

The "significantly shorter" chains mean the oil naturally flows more like a fluid (opposite of molasses) than other vegetable oils, because the hydrocarbons don’t get tangled up in each other as much. A necessary feature for their use in diesel engines, other vegetable oils require their chains to be chemically broken apart in order to reach this stage. Because the material can skip this processing, it can nearly go straight from the plant to your car.

Also, unlike most short-chained oils, this stays in liquid form even at cooler temperatures, Pollard said.

Because medium-chain fats such as coconut oil are often saturated, they have a waxy consistency and become solid in the refrigerator.

"If you want to use a material as a biofuel, you don’t want it to freeze into a solid in the winter," Pollard said.

A "direct-use" fat

Because of the way that fats are absorbed by the body, the short chains and the acetic acid base of the oil means it also has potential as a very low-calorie vegetable oil.

Due to their long chains, most fatty acids must be slowly broken down by enzymes in the body in order to pass through the intestinal wall.

But the lack of chemical processing required by the burning bush seed oil for industrial use could also carry over to the body, where the normal routes that break down and package fats may be bypassed.

Shorter- and medium-chain fatty acids can enter circulation directly without being broken apart and repackaged, nutritionist Eric Yen at the University of Wisconsin told Livescience.

The body’s more direct use of shorter-chained fatty acids leads to less body fat.

"When the fats are broken down in your gut, they’re re-synthesized and then they’re usually shipped off to the adipose—fatty—tissues, so that’s what makes you fat,” Pollard said. Fats not re-synthesized are burned off and used as energy, a process otherwise known as oxidation.

"There’s reason to think this oil has a tendency to be oxidized rather than deposited [as fat]," said Pollard.

Yen, who was not involved with this research, agreed that oil based on shorter-chain fats held potential for lower-calorie vegetable oil.

Diamond in the rough

"Only a handful" out of tens of thousands of plants across the entire plant kingdom evolved to contain the gene that shuts off the normal route of triglyceride production and switches on the enzyme that codes for short-chained fats. Of those that did, Pollard said, very high levels of the fat are unique to the burning bush shrub, whose seed oil is 98-percent acetyl glycerides.   

"To have a plant that has completely changed its biochemistry like this … is amazing," Pollard said.   

A full understanding of the oil’s appropriate uses—whether as a biofuel, biolubricant, food oil or other use—will require more testing.