Purification, characterization of an extracellular dextranase from an isolated Penicillium sp

Abstract:

Abstract: [Objective] To obtain new fungi producing dextranase, we identified a strain F1001 showing high dextranase activities. [Methods] Morphological and ITS rDNA sequences homology analysis were performed to identify the strain F1001. The enzyme was purified to electrophoretic homogeneity by the steps of ammonium sulfate precipitation and Sepharose 6B column chromatography. We studied the catalytic properties and the mechanism of the dextranase. [Results]The isolated strain F1001 was identi?ed as Penicillium aculeatum precisely by ITS rDNA sequences homology analysis. Its molecular mass was estimated to be about 66 kDa by SDS-PAGE. Activities of dextranase were measured with dextran 70 kDa as substrate, the optimal reaction temperature was 35℃, and the optimum pH was 5.0, it was relatively stable in the condition of pH 4.0 ? 7.0 and under 50℃. The optimum substrate concentration was 3% (w/v). The final dextranase hydrolysis product was isomaltose, it was proved that the enzyme was endodextranase and only had activity with dextran joined mainly by continual α,1-6 glucosidic linkages. The Km for dextranase was calculated to be 3.55×10-5 mol/L, and the Vmax was 4.29×10-2 mol（Glu）/min?L. The enzyme activity was enhanced by Zn2+and Cu2+, and the low concentration of Cu2+ could improve the dextranase activity to 134.7%. However, the enzyme was strongly inhibited by Mn2+. [Conclusion]We isolated a new strain F1001 producing high dextranase activity and the enzyme was relatively stable. These results may provide an important basis for industrial applications.