Microbes may bolster production of natural sweetener.

Genetically engineered bacteria that eat hemicellulose in corn fiber and other sources could set the stage for a new, biobased method of making xylitol, a mint-flavored sweetener used in chewing gum, toothpaste, mouthwash and other products.

USDA-ARS chemists and collaborators developed the modified bacteria--patent-pending strains of Escherichia coli--through a cooperative agreement with zuChem Inc., Chicago, IL, and the Biotechnology Research and Development Corp., Peoria, IL.

Xylitol is produced naturally by many fruits and vegetables, and even to some degree by the human body. It is used as a sugar substitute because it imparts fewer calories, has a cool mint flavor, helps fight cavity-causing bacteria, and can pass through the human gut without involving insulin. Because xylitol is only slowly absorbed and partially utilized, a reduced calorie claim is allowed: 2.4 calories per gram or 40% less than other carbohydrates. Xylitol use reduces tooth decay rates both in high-risk groups (high caries prevalence, poor nutrition and poor oral hygiene) and in low-risk groups (low caries incidence using all current prevention recommendations).

Commercial-scale quantities are derived primarily from birchwood fibers that have been subjected to a combination of acids, high pressure and temperature, chemical catalysts and a series of separation and purification steps. But the process is expensive, and the resulting xylitol must be imported, primarily from Finland and China.

In studies at the USDA-ARS Fermentation Biotechnology Research Unit, scientists used metabolic pathway engineering to retool the enzyme-making machinery of E. coli bacteria so that they could convert two hemicellulose sugars--xylose and arabinose--into xylitol. At the laboratory scale, the bacteria were kept inside special biofermentors and fed a broth of corn fibers or other sources of hemicellulose. The xylitol they excreted was later purified from the broth as a white crystalline powder.

Under the cooperative agreement, ARS researchers are helping zuChem develop a commercial-scale process that could cut xylitol's production costs and open the door to its manufacture in the United States from corn and other homegrown crops. The company is targeting 2007 for both manufacturing scale-up and commercial product launch.

Further information. Badal Saha, USDA-ARS National Center for Agricultural Utilization Research, Fermentation Biotechnology Research, Room 3316, 1815 N. University St., Peoria, IL 61604; phone: [phone]; fax: [phone]; email: [e-mail]. Rajni Aneja, Vice President, Corporate Development, zuChem, Inc., 2201 W. Campbell Park Dr., Suite 215, Chicago, IL 60612; phone: [phone]; fax: [phone]; email: [e-mail].