Multiphase Bioreactor Design

Figure 7.9 Representation of different

models and their correlation to the

experimental results. (From Carvalho

et al., 2001b)

Accordingly, in the design and analysis of biological reactors for process optimisation,
the sequence of reactors plays an important role. Most of the applications described in the
literature are related to fermenters. To obtain high final cell concentrations, the best
reactor combinations are always multiple fermenters connected in series (Lee, 1992).
Bailey and Ollis (1977) and Levenspiel (1972) also discussed the efficiency of reactor
sequences, and concluded that a CSTR-PFR sequence or a cascade of two CSTR
maximise product yield and are suitable for a wide variety of process kinetics and design
objectives.

Analysis of stability on a series of twa CSTRs

From the aforementioned, the stability may be determined for the two CSTRs cascade.
The determination of half-life time is again based on the conversion degree obtained in
the retentate and permeate. The enzyme on the membrane surface (i.e. using the retentate
conversion degree evolution) has a faster deactivation (4.3 times faster) than that
observed for the enzyme entrapped in the pores (Carvalho et al., 2001b) The explanation
for this is based on the exposition conditions of the two portions of enzyme. The cutinase
adsorbed onto the surface of the membrane supports high shear forces caused by the
recirculated fluid, which accelerates the denaturing process. This may be better
understood by the calculation of the linear velocity at the membrane surface and in the
membrane pores (Equations 64 and 65).

Multiphase bioreactor design 226