Multiphase Bioreactor Design

Table 4.4 Reactor performance equations for

immobilised biocatalysts

Reactor performance equation

Kinetic form Kinetic
equation

CSTR PFR, BSTR

Michaelis-Menten

Reversible Michaelis-Menten

Substrate inhibition

(^)
Product inhibition
(competitive)
Comparison of immobilised enzyme reactors
When the biochemical reactions are kinetically controlled, it can be seen that the BSTR
and PFR are described by the same design equations and show a better performance than
the CSTR in most cases, except for substrate inhibition kinetics. Figure 4.10 compares
the substrate conversion degrees obtained in a PFR and a CSTR with the same
normalised residence time in both types of reactors, for the Michaelis-Menten kinetics.
For zero order, both reactors show the same performance:
(53)
For first-order reaction rates the PFR displays a higher performance than the CSTR:

(54)

Effect of mass transfer on the performance of immobilised biocatalyst

reactors

The design equations previously described are only valid when there are no factors which
modify the kinetics of the immobilised biocatalyst (partition effects, heat and mass
transfer effects and decay of biological activity) and the hydrodynamic characteristics of
the reactor (back-mixing). Thus the kinetic constants, Kmi and k2i and the activity of the

Multiphase bioreactor design 116