Purification and characterization of an endoinulinase from Xanthomonas campestris pv. phaseoli KM 24 mutant

Abstract

An extracellular endoinulinase from Xanthomonas campestris pv. phaseoli KM 24 mutant was purified to homogeneity by gel filtration chromatography and showed a specific activity of 119 U/mg. The optimum pH and temperature of the purified enzyme were found to be 6.0 and 50 °C, respectively. The enzyme was stable up to 60 °C, retaining 60 % of residual activity for 30 min, but inactivated rapidly above 60 °C. The enzyme was found to be stable at pH=6-9 when it retained 100 % of its residual activity. The Lineweaver-Burk plot showed that the apparent K m and υ max values of the inulinase when using inulin as a substrate were 1.15 mg/mL and 0.15 μM/min, respectively, whereas the k cat value was found to be 0.145 min -1. The calculated catalytic efficiency of the enzyme was found to be 0.126 (mg·min)/mL. The purified inulinase can be used in the production of high fructose syrups.