Leucrose, D-glucopyranosyl-a( 1 + 5)-~-fructopyranose, is produced by treatment of sucrose with the a( I + 6)-glucosyltransferase isolated from Leuconostoc mesenteroides, a nonpathogenic, nontoxigenic microorganism. Rats, dogs, and humans metabolize leucrose efficiently and rapidly in the jejunum by enzymatic hydrolysis into its constituent glucose and fructose. Only traces of leucrose appear in plasma and urine of rats and humans, whereas somewhat larger amounts are seen in plasma and urine of dogs. No toxic or other biological effects were detected in 13-week studies in rats and dogs. Leucrose is not teratogenic in rats and rabbits, and is not genotoxic. It is noncariogenic in humans and rats, and resists attack by the microorganisms present in the human oral cavity. Downloaded from SAFETY ASSESSMENT Microbiological ConsiderationsLeuconostoc mesenteroides is a species of the genus Leuconostoc that is nonpathogenic to plants, animals, and humans. The cell wall of dextran-forming strains contains dextran sucrase. The bacteria depend on the presence of a fermentable carbohydrate for growth. Dextran-forming strains occur on sugarcane and sugar beet as spoilage organisms. Leuconostoc mesenteroides forms a characteristic slime of dextran from sucrose. The genus is also nontoxigenic and is not known to form any bacteriocins or antibiotics. The use of this microorganism does not give rise to any microbiological hazards. Toxicological ConsiderationsLeucrose can be considered to be a modified sucrose, and therefore a food, that after digestion is present as glucose and fructose in the systemic circulation. The only structures in the body coming into direct contact with high concentrations of