SCIENCE & TECHNOLOGY
FISH NO MORE
genes that allow algae to synthesize omega-3 fatty acids. Oceans can’t support our current level of fish consumption, so land-based plants may be more sustainable sources of these valuable fatty acids. Omega-3 fatty acids are a class of polyunsaturated fatty acids in which the first double bond is located at the third carbon from the methyl group at the end of the carbon chain. Because humans cannot synthesize omega-3s from scratch and they are needed nutritionally, they are classified as essential fatty acids. The core omega-3 fatty acid for humans—and the one most frequently consumed in the average American diet—is α-linolenic acid (ALA), which contains 18 carbons and three double bonds. Many plant oils, such as canola, soybean, and flaxseed, contain large quantities of ALA. Our bodies can make a variety of other longer chain omega-3 fatty acids from ALA on a limited basis through condensation reactions via an acetyl-coenzyme A intermediate. Longer chain omega-3 fatty acids include eicosapentaenoic acid (EPA; 20 carbons and five double bonds) and docosahexaenoic acid (DHA; 22 carbons and
ISTOC K
Scientists are engineering plantbased sources of the omega-3 fatty acids found in fish oil supplements.
FISH OUT OF WATER Plunging salmon populations mean ‘heart healthy’ FISH OIL COMPOUNDS may soon be in your veggies CARRIE ARNOLD, C&EN WASHINGTON
HEART DISEASE. Macular degeneration.
Neuropathy. Rheumatoid arthritis. It’s hard to find an illness or syndrome that doesn’t claim some relief from omega-3 fatty acid supplements. Given their ability to lower triglyceride levels and blood pressure, reduce the risk for heart attack, and possibly decrease inflammation, “omega-3 fatty acids” have become some of the most popular medical buzzwords. Fatty fish, such as salmon and albacore tuna, are considered the optimal dietary source of these “heart healthy” omega-3s. But most Americans don’t eat nearly the amount recommended by the American Heart Association. For a person without any coronary heart disease, the association recommends two servings of fatty fish each week, or 4 to 6 g of omega-3s. To meet these levels, Americans would have to quadruple their fish intake. This has caused many people to turn instead to fish oil nutritional supplements to boost their intake of omega-3 fatty acids.
As demand for omega-3-rich fish oil supplements continues to increase, wild salmon populations—the primary source of this precious oil—are plunging as a result O of overfishing, disease, and pollution HO (C&EN, June 16, 𝛂-Linolenic acid O page 14). Because of the limited supply HO and increasing deEicosapentaenoic acid mand, economists O fear a dramatic HO rise in the price of Docosahexaenoic acid omega-3-rich fish oil supplements. six double bonds). Although both EPA and So some scientists have begun to wonder: DHA have received the moniker “heart Is it possible to get the benefits of fish oil healthy,” the majority of health benefits apwithout any fish? pear to come from DHA. Both of these fatty In fact, fish don’t make these omega-3 acids are only found naturally in fatty fish fatty acids themselves; the compounds and the algae they consume. come from the algae the fish consume. Armed with that knowledge, scientists have begun to transplant into plants the RESEARCHERS AT Dow AgroSciences, in collaboration with Martek Biosciences, have turned to algae as a potential new source of EPA and DHA for the human diet. Rather than extracting the EPA and DHA from the algae to make supplements, researchers at Dow have inserted the algae genes required to make DHA into canola seeds. The en-
To make a long-chain fatty acid with double bonds in specific positions would be “extremely expensive and inefficient.” WWW.C E N- ONLI NE .ORG
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SCIENCE & TECHNOLOGY
Because of the limited supply and increasing demand, economists fear a dramatic rise in the price of omega-3-rich fish oil supplements.
O HO Stearidonic acid
FOR MONSANTO, soybean plants were
an obvious choice for enrichment. Besides being one of the three major plants in the company’s portfolio (the others are corn and cotton), soybeans are one-fifth oil—an oil that borders on ubiquitous in foods on supermarket shelves. By working with Solae Co.—an alliance between DuPont
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thing is to make the component of omega-3 fatty acids that is most beneficial,” he says. Besides their strong odor, omega-3 fatty acids such as DHA are very unstable and oxidize rapidly because they contain a large number of carbon atoms and double bonds. To prevent oxidation, these compounds must be kept away from light, heat, and oxygen. By combining reactive DHA with more stable canola oil, researchers at Dow AgroSciences hope to combine the best of both products to create an affordable, shelf-stable product for use throughout the food industry.
Monsanto is taking a slightly different approach to creating a plant-based substitute for marine-based omega-3 fatty acids. Rather than enriching plant oil with EPA or DHA, researchers at Monsanto genetically engineered a soybean plant enriched in stearidonic acid (SDA). SDA is a short-chain omega-3 fatty acid, one humans can use as a precursor to make longer chain omega-3 fatty acids such as EPA and DHA. Researchers at Monsanto searched their proprietary library of plant and fungal genes and found two that code for enzymes that enable soybeans to produce SDA. Ernie Sanders, director of the omega-3 collaboration at Monsanto, says the company decided to target SDA because it is “more stable than fish oil and has an excellent taste profile.”
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and Bunge Ltd.—Monsanto hopes to put the SDA-enriched soybean oil in items such as salad dressings, yogurt smoothies, and granola bars. But look on any supermarket shelf and you may already find products enriched in omega-3 fatty acids (C&EN, July 28, page 30). Although products from the Dow and Monsanto ventures aren’t likely to appear in stores for several years, Martek Biosciences has developed a DHA additive that’s already used in foods from infant formula to Crisco. Martek isolates DHA from two species of microalgae that produce very large amounts of the fatty acid. Scientists grow them in large vats, using a fermentation process similar to beer-making. After fermentation, the oil M ONSA NTO
zymes these algae genes produce allow the canola plant to synthesize DHA from arachidonic acid via a condensation-desaturation pathway. Such plants produce canola oil that is enriched with DHA. David Dzisiak, commercial leader in oils at Dow AgroSciences, says that his company ultimately chose to focus solely on DHA because the compound provides so many health benefits to consumers. “The best
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is extracted. “What we end up with is a very highly concentrated omega-3 vegetarian oil,” says Joseph Pfeifer, associate director of fermentation sciences at Martek. Although this oil can be added to foods directly, Martek has engineered a microencapsulated DHA compound that protects the DHA from oxidation and degradation. Using a proprietary process,
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scientists at Martek Monsanto’s suspend the DHA in soybeans, which a matrix. The final have been modified product, a powder to produce that is dry to the stearidonic acid, look and hopefully touch, can be added taste like the directly to food duroriginal. ing processing. With all of the engineering and processing that goes into producing these plant-based sources of omega-3 fatty acids, it might seem like it would be easier to synthesize them in the lab. Not so, says Ruben Abril, director of ingredient formulation and technical support at Martek. Synthesizing these fatty acids from scratch is possible, he says, but to make a long-chain fatty acid with double bonds in specific positions would be “extremely expensive and inefficient.” That leaves researchers to rely on Mother Nature for omega-3s. Whether from canola, soybeans, or microalgae, the distance between salmon and their hearthealthy omega-3 fatty acids is likely to only get larger. ■
