Technique evaluates enzyme's potency.

About 45% of sugar in the United States comes from cane. In factory milling stations, these 10-foot-tall plant stalks are pressed and squeezed, their juice heated, clarified, evaporated and crystallized until raw sugar is formed.

But a combination of humidity and cane damage can bring about a microbial feeding frenzy that's capable of inflicting serious economic loss. Leuconostoc mesenteroides are considered by U.S. growers and processors to be the greatest cause of cane deterioration. Any time sugarcane is cut, injured or damaged, Leuconostoc bacteria may invade the cane. They seize on damage caused by the burning of cane that's done to ease harvest or by the freezing weather that occasionally hampers cane-growing regions.

USDA-ARS researchers are helping processing facilities solve one of their most difficult issues: dextran. Dextran is a thick, viscous material that builds up in damaged cane. It's caused by sugar-hungry bacteria that are attracted to the wounds of just-harvested or burned cane. With its thick, gummy nature, dextran can clog the pipes in which cane juice is heated and clarified. For processors, the more dextran there is in cane, the less sucrose there is for turning into sugar.

Dextranases must be used to break down this sticky polysaccharide. But determining which type of dextranase enzyme to use can be a challenge. The enzymes are sold in a broad array of concentrations and units of measurements. The strength and activity levels of commercially available dextranases vary widely. There's about a 20-fold difference in activity among them. And processors may not know where in the process it's most effective to add the enzyme: to the cane juice or syrup--and how much?

Spending the bulk of research time out of the lab and inside sugar processing facilities, ARS scientists developed a solution to the dextran problem. It's a simple test, known as the Eggleston titration method, for evaluating an enzyme's potency at the factory. Now, they are able to advise processors about how and where to apply the dextranase for optimal usage. These research findings are paying off. As much as a 95% reduction in dextran content is being seen in processing factories that have adopted the ARS technology.

Further information. Gillian Eggleston, USDA-ARS Southern Regional Research Center, Commodity Utilization Research Unit, 1100 Robert E. Lee Blvd., New Orleans, LA 70179; phone: [phone]; fax: [phone]; email: [e-mail].