General properties of extracellular bacterial inulinase

The extracellular inulinase system of a strain of Arthrobacter sp. consists of a β -fructofuranosidase active on inulin raffinose and sucrose with a relative rate inulin/sucrose (I/S) of 0.2.
Crude enzyme preparations were obtained by fractionation of the liquid culture at stationary phase of growth with ammonium sulphate. Purification was carried out by DEAE cellulose chromatography and ultrogel ACA 34. Only one protein band was observed by electrophoresis. The enzyme was stable at high temperatures and was active at neutral or slightly alkali pH. Fructose is liberated as the sole reaction product of inulin hydrolysis, suggesting that the enzyme was an exoinulinase. The Michaelis constant (calculated at 40°C and pH 6) was 0.25 × 10^-2 mol/l for the inulin and 0.12 × 10^-2 mol/l for sucrose.
The enzyme was suitable for fructose production from root extracts of plants rich in polyfructosans or sucrose.