A sweetener sourced from corn.

A low-calorie sweetener-xylitol-may someday be sourced from corn. Makers of some specialty brand sugarless chewing gums now pay about $3/lb for xylitol, which gives their product a minty-cool taste. New developments may drive production costs down and the volume up, according to USDA/ARS researchers (National Center for Agricultural Utilization Research, 1815 N. University St., Peoria, IL 61604).

Scientists are developing a way to derive the sweetener from corn fiber left over from ethanol production. Currently, U.S. 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 using a chemical process. The process requires high pressure and temperature, an expensive catalyst and costly steps to remove byproducts.

A biotechnological approach involving corn fiber should be less costly. Expecting that beet and cane sugar will remain much cheaper than xylitol made from the xylose in corn fiber, scientists believe 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 insulin.

Researchers in the United States and abroad showed that 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 sugars-the ones associated with tooth decay.

ARS scientists began to brighten the prospects for making xylitol in the United States from corn nearly 10 years ago. They found that one strain of Aureobasidium yeast, during hydrolysis, released up to 20% of the xylose from corn fiber that was treated with alkaline hydrogen peroxide. Since then, they've found a mixture of Aureobasidium enzymes that releases up to 70%.

They also have developed a process using a strain of another yeast, Pichia guilliermondii, to convert the xylose into xylitol. To overcome a problem, glucose repression, in which glucose slows or shuts down some microbial metabolism, the scientists used two versions of P. guilliermondii. The first version gobbled up all the glucose, its first choice in food, in the fermentation vat. Then the next focused on consuming xylose to produce xylitol.

Chemists identified another promising strain of xylitol-producing yeast, Candida peltata. In spite of glucose repression, they achieved a 56% yield of xylitol from xylose in the mixture. They found that a xylose-related sugar, arabinose, induced no repression of xylitol production. The scientists envision a genetic engineering process that might enable the yeasts to produce xylitol from arabinose as well as from xylose.

Researchers are still optimizing their process and expect it will be a few years before the technique is commercially viable. They are interested in discussing possibilities with industry.

Further information. Timothy Leathers; phone [phone]; fax: [phone].