Characterization of two thermostable inulinases from NRRL 2710.

Two inulinases (Inu2 and Inu3) were purified from NRRL 2710 by chromatography on DEAE-Sepharose and Sephacryl S-200 columns. The molecular weight of Inu2 and Inu3 were determined to be 76 and 30 kDa, respectively. Inu2 and Inu3 had the same pH optimum at 5.0, temperature optimum at 50 and 60 °C, and thermal stability up to 60 and 70 °C for 1 h, respectively. Inu2 and Inu3 had low km values (0.93 and 0.70 mM, respectively) indicating the high affinity toward inulin. Mg, Ca, Zn and EDTA did not significantly influence the enzyme activity. Ni, Cu, Fe and Co showed a partial inhibitory effect, and Hg had a strong inhibitory effect. -Chloromercuribenzoate had a partial inhibitory effect on Inu2. From these findings, inulinases can be beneficial enzymes for industrial enzymatic production of high fructose syrup.