Purification and Characterization of an Inulin Fructotransferase from Flavobacterium sp. LC-413

A bacterial strain LC-413, producing an extracellular inulin fructotransferase (depolymerizing) which converts inulin into di-D-fructofuranose dianhydride (DFAIII), was isolated from soil. Inulin fructotransferase from the isolate identified as a strain Flabobacterium sp. was purified from the culture broth by ammonium sulfate precipitation, followed by column chromatograpies on DEAE-Toyopearl 650 M and phenyl-Toyopearl 650 M. The purified enzyme gave a single band on an electrophoretic disc-gel. The molecular weight of the enzyme was estimated to be 44, 000 Da by SDS-polyacrylamide gel electrophoresis, and 45, 000 Da by gel filtration, suggesting the monomeric state of the enzyme. The isoelectric point of the enzyme was about pH 4.5. The optimal pH and temperature for the enzyme reaction were 6.0 and $50^{\circ}C$, respectively. The purified enzyme digested inulin into di-D-fructofuranose-l, 2': 2, 3'-dianhydride, confirming the enzyme was an inulin fructotransferase (inulinase II).