Figure 6.9 Schematic diagram of a
single-pass diffusion membrane
reactor (•—enzyme, S—substrate, P—
product, —membrane)
Figure 6.10 Schematic diagram of a
diffusion membrane reactor with
recycle (•—enzyme, S—substrate, P—
product, —membrane)
the system, enabling measurement and control (pH, temperature, mixing, sampling, etc.).
A recent publication describes a reactor of this type for the coupled transcription/
translation from a PCR (polymerase chain reaction) product using T7 RNA polymerase
and an Escherichia coli S30 extract with a hollow fibre module (Nakano et al., 1999).
Multiphase Membrane ReactorsMultiphase membrane reactors promote an interfacial contact between enzyme and
substrates at the membrane matrix. The membrane usually acts as a support for the
enzyme and for the interface between two immiscible liquid phases (hydrophilic and
hydrophobic). These constitute reservoirs where substrates and products may be
solubilised (Figure 6.11). Diffusion is again the dominant transport mechanism together
with interfacial transport. If the membrane material/structure is carefully chosen, the
hydraulic pressure caused by the circulation of the two phases is usually sufficient to
maintain a good phase separation at the membrane (Pronk et al., 1988). Eventually, a
Enzymatic membrane reactors 157