bioreactor studies of heterologous protein production by ...

Enyme collcentration m the t>ioreactor achieved its maximum Mhie after 36 hom and
remained constant for about 30 hous before decrmsnig. The maximum enzyme concentration
in the immobilizd al systern was 60% higher than tbat of the corzesponding k e cd system.
The decb m the enzyme concenaatioa was due to plasniid loss rather than the htaùihy of
the enzyme. The enzyri concentration would tend to reach a constant steady state value evui
i€ the enzyme were unstabk In adan, batch cultures in stationary phare gave nearly
constant enzyme mivity for 12 hou or more under gmwih conditions. No excraceiîular
protearas that would adversely affect giucoamylase were found in suains of S. cerevisiae
(Bilinski et al, 1990).
Using the se-d süain, contmuous fermentation war, ah canied out in ixnmobilized-
œil-hlm abairlift bioreactor. The typicai results were shown m Figure 6.3. The fmnfation tirne
course with the selected suain was similar to that with the ongmal arain. However, with the
seiected main the enzyme concentration doubied enn though the cell concentrations were
nearly the same for both strains. As in fne suspension cube, the selected strain also showed
better production performance than the ongllial arain in the irmnobiljzed ceil system.
As controls, continuous fk suspension cultuns were pe~orrned in the airlift
bioreactor (without the Cotton cages) in order to make a cornparison between l5e-e ceQ and
immobïktbn systems. The cnlture medium and condaions were exactiy the same as m the
immobilized-çeil-film bioreactor. Cornparison of the enzyme cormcentrations between the fiee
and immobilized cell systems for both the ongiaal and selecDed mains are presented m Fignrc