bioreactor studies of heterologous protein production by ...

device. Littie infornation exisÛ on the use of airIift devices in large sale culture of
recombinants, even though airlift bioreactors are thoroughly proven in the fermentation
Uidustry (Chisti, 1989). Although mer saidies are needed, immobilized celi bioreactos
seem to be very pmmising for the production of recombinant products as discussed in the
following sections.
23. Plasmid Stability in Immobilized CeOs
2.3.1. Effect of Xmmobilization
E. coli. was the ikt immobiiized recombinant organisrn studied. Moes et ai. (1983)
reported that a sipnincantly higher ce11 concentration and consequently higher productivity
of plasrnid coded gene product can be obtained in a hollow fiber membrane bioreactor.
Similarly, Dhulster et aL(1984) immobilued recombinant E. coli BZ18IpTG 201 tells in
Kappa-carrageenan gel beads and obtained high ceil densities in the cavities of gel. They
pointed out the potential of gel immobilUation system and that the immobilUaton might
have an effect on plasmid stability. This effect was investigated by De Taxis du Poet et
ai. (1986). Plasmid (pTG201)-harboring E. coli were immobilizcd in K-carrageenan
beads, and plasmid maintenance was snidied for both fiee and immobüized ceUs in a
chernosrat Gel immobilization was seen to have a stabilizing effect on piasmid stability;
but once the ce& were released h m the beads, their plasmid-los fkquency was the same
as for fne cek A theoreticd analysis based on compartmentaliliition resulting from the
immobilized growth was proposed (De Taxis du Poet et al., 1986); but the plasmid
stability predicted by this mode1 was inferior to that actuaiIy observed This suggested