bioreactor studies of heterologous protein production by ...

(ranghg h m 1 to 7) on citric acid productivity was examined. They obsewed that the
highest productivity was obtained at the height-to-diameter ratio of 3.
Aïmost dl previous studies involve three-phase sluny airlift reactor with gel
entrapped imrnob~ ceh. For hydrogel ixnmobilized ceiis, the dismption problem still
exists in the airlift reactor. As discossed above, the use of soft and highly porous nanual
or synthetic materiais may ovmorne this. However, sluny three-phase airiift reacfors are
not suitable with these materials due to iheir low density. Even after loading with
biomass. they stül have a density equal to or less than that of the continuous liquid phase.
Whde the particles firculating through the airiift reactor, they tend to block the
downcomer if the particle loading inmases to certain levei, causing the instability of
reactor operation (prelUninary experiment restüt). Besides, liquid-solid mas mfer
limitation may occur in the reactor due to low liquid-soiid slip velocity. Many of these
studies were conducted on a srnail scale. and concemed mainly with the feasibility and
fermentation kinetics rather than biopmess development and transport phenornena. Littie
information is avaüable for airlift design, operation. and scale-up during actuai
fermentation processes. Therefore, mnch work is ttrgently needed in these aspects.
2.5. Modelling of Recombinant Yeast
Interest ui modeliing of piasruid instability kinetics in recombinant ce& has increased with
our better understanding of the mechanism of piasmid uistability. In nirn, such modehg
can provide valuable info~mation about the natore of piasmid instability and give a greater