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Corn Fungus Tapped for Carotenoid Production

By Jan Suszkiw
March 29, 2004

A fungus may hold the key to unlocking new, value-added uses for corn fiber and distiller's dry grains with solubles (DDGS) – the "leftovers" of making ethanol. That's the hope of Agricultural Research Service scientists, who modified the fungus Fusarium sporotrichioides with genes for making lycopene and other carotenoids.

Lycopene, a pigment that makes tomatoes red, is considered a "nutraceutical" for its purported health benefits. Some research suggests lycopene helps prevent certain cancers in people who routinely consume foods containing the carotenoid. Supplements are available for consumers who can't or don't want to eat these foods, but still desire lycopene's benefits, notes geneticist Timothy Leathers, at the ARS National Center for Agricultural Utilization Research, Peoria, Ill.

In the modified fungus, Leathers sees a potential way to mass-produce lycopene from ethanol co-products like corn fiber rather than extract and purify the carotenoid from tomatoes. Corn fiber is ideal because it's abundant and costs about five cents a pound. The U.S. ethanol industry generates four million tons of the fiber annually, and sells it as livestock feed to avoid disposal fees. The same applies for DDGS, notes Leathers, at the ARS center's Fermentation Biotechnology Research Unit.

Proof-of-concept studies at the Peoria center showed that when cultured in lab flasks, the modified fungus produced 0.5 milligram of lycopene per gram of dry weight within six days. The plan now is to scale up the studies by culturing the fungus in fermenters on a growth medium containing the corn fiber or DDGS.

To equip F. sporotrichioides for the job, the team first "short-circuited" the metabolic pathways by which it makes natural trichothecene toxins. Then, using a patented recombinant technique (6,372,479), the team "re-wired" the fungus with new genes for making lycopene. ARS patented the microbe on Feb. 24 (6,696,282). Leathers' colleagues are James Jones of Northwestern University and Thomas Hohn of Syngenta. Both are former ARS scientists.

ARS is USDA's chief scientific research agency.