Biosynthesis of levan and a new method for the assay of levansucrase activity.

The polysaccharide levan was synthesized in a solidified agar medium containing sucrose as a source of fructose. The biosynthesis was achieved by the enzyme levansucrase (2,6-fructan-d-glucose 6-fructosyltransferase, EC 2.4.1.10), a small quantity of which was placed in circular wells cut in the agar gel. The enzyme slowly diffused through the agar-sucrose medium and the synthesis of levan was observed as circular white areas, the size of which was dependent on the time of incubation and the concentration of enzyme used.