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Effect of Organic Solvent on the Characteristics of Free and Immobilized Inulinase from Kluyveromyces marxianus ATCC 16045

Fernanda V. A. Risso1, Marcio A. Mazutti1,2, Helen Treichel2*, Fátima Costa1, Francisco Maugeri1 and Maria Isabel Rodrigues1

1Department of Food Engineering, Faculty of Food Engineering, University of Campinas (UNICAMP), P.O. Box 6121, CEP 13083-862, Campinas, SP, Brazil
2Department of Food Engineering, Regional Integrated University, Campus de Erechim (URI), P.O. Box 743, CEP 99700-000, Erechim, RS, Brazil

Article history:
Received July 7, 2009
Accepted February 1, 2010

Key words:
organic solvent, inulinase, stability, kinetic parameters

Summary:
The aim of this work is to evaluate the effects of the butyl acetate concentration on the characteristics of free and immobilized inulinase from Kluyveromyces marxianus ATCC 16045. The mass fractions of organic solvent (OS) in sodium acetate buffer (0.1 M) were studied in the range from 25 to 70 %. The characteristics of both free and immobilized enzymes were not significantly affected by the OS mass fraction. The optimal temperature for the free enzyme was 55 °C at all OS mass fractions studied, whereas for the immobilized enzyme the optimum was 55 °C at 70 % of butyl acetate, and in the range from 50 to 60 °C at 25 and 50 % of OS. The optimum pH values, at all OS mass fractions, were 4.8 and 4.4 for the free and immobilized enzymes, respectively. The immobilized enzyme showed more stability at 50 °C and pH=4.8 for the whole range of OS mass fractions, since its stability was improved about 3 times. The kinetics parameters were calculated using Lineweaver-Burk plots. For the free enzyme, the vmax values were 12.5, 58.5 and 37.6 U/mL and the Km values 17.5, 280.7 and 210.4 mM at butyl acetate mass fractions of 25, 50 and 70 %, respectively. Similarly, for the immobilized enzyme, the vmax values were 38.9, 59.5 and 72.5 U/mL and the Km values 3.1, 5.4 and 14.0 mM at the same butyl acetate mass fractions, respectively.

 


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