A levanbiose-accumulating levanase from Pseudomonas sp. No. 43 was purified to a homogeneous state by (NH4)2SO4 fractionation and by chromatography on DEAE-Toyopearl 650 M and phenyl-Toyopearl 650 M columns. The molecular mass and isoelectric point of the enzyme were estimated to be 36 kDa and 5.7 respectively; the optimal pH and temperature for the enzyme reaction were pH 7.0 and 40 degrees C respectively. The purified enzyme was stable in the pH range 6.0-8.0 at 20 degrees C and stable up to 50 degrees C at pH 7.0. The enzyme's activity was inhibited by MnCl2, CoCl2, AlCl3, EDTA and potassium permanganate. The levanase was specific towards the 2, 6-beta-D-fructosidic linkages of levan and did not hydrolyse other polysaccharides among those examined. The enzyme is an exohydrolase of levan and produced levanbiose as a sole product; the limits of hydrolysis of levans from Zymomonas mobilis and Serratia sp. were 65% and 80% respectively.