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A New Sweetener from Ethanol Waste

Corn fiber that’s left over from ethanol production could be turned into a high-value, low- calorie sweetener for niche markets, based on a process being developed by Agricultural Research Service scientists.

The sweetener is a white crystalline powder called xylitol. Makers of some specialty brand sugarless chewing gums now pay about $3 per pound for xylitol, which gives their product a minty-cool taste. By comparison, industry now sells the ethanol leftovers as cattle feed for only a few pennies per pound.

The scientists found that certain strains of the yeast Pichia guilliermondii can excel at making xylitol, but that process can be hindered by glucose, another of the leftover sugars from fermented corn fiber. The problem: When P. guilliermondii comes in contact with both glucose and xylose in fermenting corn fiber, it “prefers” the glucose and--like a child who would rather gorge on ice cream than spinach--it spends its energy on gobbling the glucose, which leaves the yeast relatively ineffective for carrying out the xylose-to-xylitol transformation. The solution devised by ARS scientists: Send in the “B” team. The scientists add an initial batch of P. guilliermondii to the fermenting fibers to devour the glucose. Then they mix in more P. guilliermondii to tackle the task of transforming the xylose into xylitol.

Xylitol has one-third fewer calories than sugar and about the same sweetening power. It’s currently made in Finland in a chemical process by treating acid-treated fibers of birch wood. It’s now a $28 million market in foods for special dietary uses, mouthwashes, toothpastes and chewing gums.

Biological conversion of xylose should help make xylitol more economic to produce, according to the researchers, because it requires less energy than chemical conversion. This could drive production costs down and the market volume up.

An article about the research appears in the July issue of Agricultural Research magazine and online at:

http://www.ars.usda.gov/is/AR/archive/jul00/xylit0700.htm

Scientific contact: Timothy D. Leathers and Badal C. Saha, ARS National Center for Agricultural Utilization Research, Peoria, Ill., phone (309) 681-6377 (Leathers), (309) 681-6276 (Saha); fax (309) 681-6686, leathetd@mail.ncaur.usda.gov and sahabc@mail.ncaur.usda.gov.