The behavior of dextransucrase from Leuconostoc mesenteroides NRRL-B-512F in the presence of organic solvents was investigated The activity and stability of this enzyme were studied in the presence of various concentrations (% v/v) of dimethysulfoxide (DMSO) dimethylformamide (DMF) ethanol, acetone and acetonitrile. The stability was measured at 4 degrees C and 30 degrees C. Generally the initial velocity of dextransucrase decreases proportionally to solvent concentrations except in water-DMSO mixture. Indeed in 25% DMSO (v/v) 45% of the activity in pure wafer was detected whereas 26% was measured in 10% DMSO (v/v). Moreover the loss of activity is much more considerable in the presence of acetonitrile than in the presence of other solvents. In 20% acetonitrile (v/v) only 11% of the activity was measured. Concerning the stability of the enzyme it appears that it is more stable at 4 degrees C than at 30 degrees C. Surprisingly dextransucrase is more active after a period of contact with some solvents, especially DMSO or ethanol, than in acetate buffer. After 2 days in 20% DMSO (v/v) at 4 degrees C, 300% of the initial activity remained and 250% at 30 degrees C. This increase of activity is also observable after 2 days in 20% ethanol (v/v) where 180% of the initial activity is measured.