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Bacterium Tapped to Make Low-Calorie Sweetener for Candies, Gums

Mannitol's not a household name, but you've probably consumed this clean-tasting sugar alcohol as a powdery coating on chewing gum hard candies and chewable tablets.

Now Agricultural Research Service chemist Badal Saha in Peoria, Ill., reports success using the bacterium Lactobacillus intermedius to make mannitol. Saha credits the bacterium's powerful metabolic enzymes with enabling it to produce mannitol from high-fructose corn syrup, glucose and other carbohydrates.

According to Saha, at ARS' National Center for Agricultural Utilization Research in Peoria, commercial manufacturers now use a process that subjects a 50-50 mixture of fructose and glucose to a nickel catalyst and high-pressure hydrogenation, or HPH. In addition to generating chemical wastes, HPH only converts 25 to 30 percent of the mixture to mannitol, now selling for about $3.32 a pound. What's left is mostly sorbitol, a sugar alcohol worth just 73 cents a pound.

Laboratory trials show the Lactobacillus bacterium is more efficient. In fact, when grown on a broth containing 100 grams of fructose and 50 grams of glucose, it converts as much as 100 percent of the fructose to mannitol. The Lactobacillus strain NRRL B-3693 also outperformed 11 other mannitol-producing organisms.

Seen microscopically, mannitol appears as white, needlelike crystals. It is slightly less sweet than sucrose, has half as many calories per gram (1.6 versus 4), and doesn't contribute to tooth decay. Besides granulated powders, mannitol is used as a bodying agent for food, a shelf-life extender, low-calorie sweetener for diabetics, and as an osmotic diuretic. Certain plants naturally produce it, though not enough to satisfy commercial needs. That may change if a company now consulting with Saha can exploit Lactobacillus' back-to-nature appeal as a commercial reality.

A longer story about Saha's work appears in this month's issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.