Determination of Immobilized Enzyme Apparent Kinetic Parameters in Packed-Bed Reactors: Presentation of a New Methodology
Integration of life sciences & engineering
Design, Analysis & Control of Fermentation Processes (T5-2)
Keywords: Biochemical engineering, Dynamic modelling, Immobilized enzyme kinetics, Packed bed reactors
Determination of Immobilized Enzyme Apparent Kinetic Parameters in Packed-Bed Reactors: Presentation of a New Methodology
Ahmet R. Özdural*, Colin Webb**
*Chemical Engineering Department, Hacettepe University, 06532 Ankara/TR.
**School of Chemical Engineering and Analytical Science, The University of Manchester, Manchester, M60 1QD/UK.
In this work we focus our attention on the extension of a novel methodology, which was introduced by our group and originally used in the membrane separations [1] and later in the first order packed-bed catalytic reactions [2], to the explicit determination of packed-bed immobilized enzyme apparent Michaelis–Menten kinetics parameters. The kinetic parameters for the immobilized enzyme may be different from those of the suspended enzyme because of, among others, diffusional restrictions and interactions with the carrier or deactivation due to immobilization. Furthermore, due to the difference in hydrodynamic conditions, the immobilized enzyme apparent kinetic parameters determined through batch wise stirred reactor experiments usually do not reflect the apparent kinetic parameters of immobilized enzymes in packed-bed reactors. In order to determine the apparent kinetic coefficients in continuous mode operating packed-bed enzymatic reactors, via established techniques, simultaneous measurement of the concentration differences between the substrate inlet and outlet flows are required [3]. Especially for laboratory scale experimental set-ups, it is likely to come across with very small substrate concentration differences between the bed inlet and outlet flows. Thus the measurement of the substrate concentration differences between the inlet and outlet streams can be very difficult and inaccurate. The present method is free from such limitations and, for the model development; a packed-bed immobilized enzyme reactor with a recycle system is envisaged. The maximum reaction rate is retrieved by the technique of Özdural et al. [4]. Once vmax is known, and by making use of Michaelis–Menten kinetics can be approximated by first-order kinetics for low substrate concentrations, the value of Km is calculated through a new explicit equation, which is derived in this study by making use of the methodology explained in our former studies [1-2]. It was concluded that the proposed explicit equation successfully predicts Km values with the use of a single reservoir concentration measurement and the corresponding time data. Furthermore the apparent Km values, calculated for various recirculation rates, were in excellent agreement with those obtained via other techniques [4] that make no reference to the explicit equation proposed here. It is expected that the proposed explicit equation might simplify the dynamic modelling studies of enzymatic processes. The experimental system is composed of a reservoir and a packed-bed immobilized enzyme reactor. The experimental data is gathered for glucose decomposition reaction in a recirculation system with immobilized glucose oxidase on a weak base ion exchanger resin. The Km values were found to be 0.5×10−4 and 0.6×10−4 mMol cm−3 for the recirculation rates of 75 and 25 cm3 min−1 respectively.
References
[1] A.R. Özdural, A. Alkan, Journal of Membrane Science, 223 (2003) 49-57.
[2] A.R. Özdural, A. Alkan, C. Webb, , Chemical Engineering Journal, 118 (2006) 17-22.
[3] M.D. Lilly, W.E. Hornby, E.M. Crook, Biochemical Journal, 100 (1966) 718–723.
[4] A.R. Özdural, D. Tanyolaç, Z. Demircan, I.H. Boyacı, M. Mutlu, C. Webb, , Chemical Engineering Science, 56 (2001) 3483–3490.
Presented Thursday 20, 11:54 to 12:12, in session Design, Analysis & Control of Fermentation Processes (T5-2).
