Effects of Diffusion within Immobilized Enzyme Particles

3 Effects of Diffusion within Immobilized Enzyme Particles 

Enzymes, when immobilized in spherical particles or in films made from various polymers and porous materials, are referred to as immobUized enzymes. Enzymes can be immobilized by covalent bonding, electrostatic interaction, crosslinking of the enzymes, and entrapment in a polymer network, among other techniques. In the case of batch reactors, the particles or films of immobilized enzymes can be reused after having been separated from the solution after reaction by physical means, such as sedimentation, centrifugation, and filtration. Immobilized enzymes can also be used in continuous fixed-bed reactors, fluidized reactors, and membrane reactors. 

Apparent reaction rates with immobilized enzyme particles also decrease due to the mass transfer resistance of reactants (substrates). The Thiele modulus of spherical particles of radius R for the Michaelis-Menten type reactions is given as 

Immobilized enzyme beads of 0.6 cm diameter contain an enzyme that converts a substrate S to a product P by an irreversible unimolecular enzyme reaction with K = 0.012 kmol m and the maximum rate 

Determine the effectiveness factor and the initial reaction rate, when the substrate concentration is 0.6 kmol m .  

3 Effects of Diffusion Within Immobilized Enzyme Particles 

Immobilized enzyme beads of 0.6 cm diameter contain an enzyme which converts a substrate S to a product P by an irreversible, unimolecular enzyme reaction with Km =0.012 kmol m 3 and a maximum rate Vmax=3.6 x 10 7 kmol (kg-bead) s. The density of the beads and the effective diffusion coefficient of the substrate in the catalyst beads are 1000kg m-3 and 1.0 x 10 6cm2s, respectively. 

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