A low-calorie sweetener called
xylitol may someday be made from corn.
Makers of some specialty brand sugarless chewing gums now pay about $3 per
pound for xylitol, which gives their product a minty-cool taste.
"New technologies may drive production costs down and the volume
up," says Timothy D. Leathers, an Agricultural Research Service geneticist at
the National Center for Agricultural Utilization Research (NCAUR), Peoria,
Illinois. He's researching a way to derive the sweetener from corn fiber
leftovers of U.S. ethanol production. Currently, industry sells corn fiber and
fermentation coproducts together as cattle feed for a few pennies per pound.
Xylitol, a white crystalline powder termed a sugar alcohol or polyol, is
made in Finland from acid-treated fibers of birch wood by a chemical process.
The process requires high pressure and temperature, an expensive catalyst, and
extensive steps to remove byproducts. A biotechnological approach involving
corn fiber should require less energy, says Leathers.
Expecting that beet and cane sugar will remain much cheaper than xylitol
made from the xylose in corn fiber, Leathers envisions that the future of the
alternative sweetener lies in niche markets. Already xylitol commands a $28
million market in foods for special dietary uses, mouthwashes and toothpastes,
as well as chewing gums.
Xylitol has one-third fewer calories than conventional sugar but about the
same sweetening power. Diabetics process it through the gut without involving
Researchers in the United States and abroad showed children's dental health
improved if their chewing gum included xylitol. The sweetener allows harmless
bacteria to crowd out common mouth microbes that digest normal sugarsthe
ones associated with tooth decay.
Leathers began to brighten the prospects for making xylitol in the United
States from corn nearly 10 years ago. He found that one strain of
Aureobasidium yeast, in a process called hydrolysis, released up to 20
percent of the xylose from corn fiber that was treated with alkaline hydrogen
peroxide. Since then, he's found a mixture of Aureobasidium enzymes that
releases up to 70 percent.
He and his colleagues also developed a process using a strain of another
yeast, Pichia guilliermondii, to convert the xylose into xylitol. To
overcome a distracting problem called glucose repression (in which glucose
slows or shuts down some microbial metabolism), the scientists used two teams
of P. guilliermondii. The first team gobbled up all the glucoseits
first choice in foodin the fermentation vat. Then the next team focused
on consuming xylose to produce xylitol.
NCAUR chemist Badal Saha identified another promising strain of
xylitol-producing yeast, Candida peltata. In spite of glucose
repression, he achieved a 56-percent yield of xylitol from xylose in the
Saha and Leathers found that a xylose-related sugar, arabinose, induced no
repression of xylitol production. The scientists envision genetic engineering
that might enable the yeasts to produce xylitol from arabinose as well as from
xylose. By Ben Hardin,
Agricultural Research Service Information Staff.
The research is part of New Uses, Quality, and Marketability of Plant and
Animal Products, an ARS National Program (#306) described on the World Wide Web
Timothy D. Leathers and
Badal C. Saha are at the
USDA-ARS National Center for
Agricultural Utilization Research, 1815 N. University St., Peoria, IL
61604; phone (309) 681-6377 [Leathers], (309) 681-6276 [Saha], fax (309)