Purification and Characterization of an Endoinulinase from Xanthomonas campestris pv. phaseoli KM 24 Mutant 


Kameshnee Naidoo^§, Ajit Kumar^§, Vikas Sharma, Kugen Permaul and Suren Singh*


Department of Biotechnology and Food Technology, Faculty of Applied Sciences, Durban University of Technology,
P.O. Box 1339, Durban 4001, Republic of South Africa



Article history:
Received September 18, 2014
Accepted February 23, 2015



Key words: 
Xanthomonas campestris pv. phaseoli KM 24 mutant, inulinases, endoinulinases, exoinulinases, fructooligosaccharides, inulin

Summary:
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 v_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.

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^§Both authors contributed equally to this work