BioEngineering Research GroupFood Chem., 95, 77-92 (2006)
Rocha, J. R., Catana, R., Ferreira, B. S., Cabral, J. M. S., Fernandes, P.
The optimal conditions for inulin hydrolysis using a commercial inulinase preparation, either free or immobilised in activated Amberlite were established by factorial design and surface response methodology. The immobilised biocatalyst displayed highest activity at pH 5.5 and 50ºC, whereas the optimum pH for the free form was slightly more acidic (4.5), and the optimum temperature was a little higher (55ºC). The model system estimated optimal pH and temperature values of 5.4 and 52ºC for the immobilised system and 4.9 and 56 ºC for the free system. A Michaelis-Menten type kinetics adequately described both free and immobilised bioconversion systems, which were evaluated under the respective optimal pH and temperature conditions. The use of a non-linear regression method for the determination of the kinetic parameters provided a best fit to the experimental data, as compared to a conventional Lineweaver-Burk linearization. The Km for inulin of the free biocatalyst was 153 gl-1 at 55º C and pH 4.5, whereas the apparent Km for inulin of the immobilised biocatalyst was 108 gl-1 at pH 5.5 and 50ºC. The reutilization of the immobilised biocatalyst throughout consecutive batches was evaluated. A significant decrease of enzyme activity was observed in the first two batches, after which the system exhibited a significant stability.
Keywords: biotransformation; enzyme immobilisation; inulin; inulinase
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