Engineer Bakers Yeast to Eat Plant Fats
December 5, 2001
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
yeasts metabolism with plant genes for converting vegetable oil fats
(lipids) into value-added byproducts. Eventually, harnessing the yeasts
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 centers
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 thats 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 Americas domestic supply.
ARS is the U.S. Department of
Agriculture's main scientific research agency.