bioreactor studies of heterologous protein production by ...

The finai giucoamyiase concentration in the ALR (153 unitsk) was much higher
than that in ihe STR (66 unitSn,) although the nnal ceii concentrations in both bioreactors
were nearly the same (Fignre 4.3). This result may be related to the difference in the
specifc growth rate in the suxind growth phase. It appears that the recombinant protein
yield decreased with increasing specific gmwth rate of the recombinant yeast The
relatiowhip between the recombinant protein yield and specitic growth rate will be further
discussed in the next section.
4.2.3. Effect of Specific Growth Rate on Recombinant Protein Yield
Figures 4.3 and 4.4 demonstrated that dissolved oxygen tension in the bioreactor affects
the specific growth rate, and the recombinant protein production was directiy related to
the specific growth rate. In order to Mer test this phenornenon. a batch culture
fementation was performed in the STR bioreactor ushg lower aeration rate (0.4 VVM).
Due to decreased dissolved oxygen in the bioreactor. the batch fermentation was
prolonged but the final glucoamylase concentration increased h m 61 to 91 uniW. Thus,
the enhanced combinant protein yield due to die slower growth rare was shown again.
The specific growth rates for both exponential phases were determined hm the
semilogacithmic plots of celi concentration versus the as shown in Figure 4.5. The
giucoamylase yields were evaluated from hear regression of glucoamylase concentrations
to c d concentrations as show in Figure 4.6. The parameter estimates are iisted in Table
4.1. Table 4.1 shows that the speciîïc pwth rates in the fint growth phase (on glucose)