Scientists Engineer Baker’s Yeast to Eat Plant Fats

Common baker's yeast, Saccharomyces cerevisiae, is best known for helping ferment beer and leaven bread. Now, Agricultural Research Service scientists are working to expand on its applications.

At the ARS Southern Regional Research Center in New Orleans, La., scientists have altered the yeast’s metabolism with plant genes for converting vegetable oil fats (lipids) into value-added byproducts. Eventually, harnessing the yeast’s metabolism on an industrial scale could help open new market outlets for oilseed crops such as soybeans, cotton and linseed, according to John Dyer, a chemist at the ARS center’s Commodity Utilization Research Unit.

Ordinarily, baker's yeast has little need for lipids except to reinforce cell walls or store energy. It's a diet of sugars and carbohydrates that really gets the yeast going--and producing the carbon dioxide and alcohol that bakers and brewers so desire.

But when modified with desaturase enzymes from plants, including Arabidopis, and then "fed" a diet of vegetable oil fatty acids, the altered yeast's lipid storage increases up to sevenfold. Depending on which desaturases are activated, and the growth conditions scientists create, the yeast's metabolism converts the lipids into valuable byproducts such as alpha eleostearic acid--a main tung oil component--and alpha linolenic acid. The latter byproduct is an omega 3 fatty acid that’s been shown to protect against heart disease and cancer.

Refining the procedures further should allow for larger-scale production of these valuable lipid compounds in yeasts, according to Dyer. For tung oil, this eventually could mean a way to supplement U.S. imports from China and South America. Amid fluctuating prices and quality, such imports supply most of the 1 million pounds of tung oil now used in U.S. paints, resins, inks and wood finishes. Damage caused to tung tree orchards in the southern United States by Hurricane Camille in 1969 virtually crippled America’s domestic supply.

ARS is the U.S. Department of Agriculture's main scientific research agency.