bioreactor studies of heterologous protein production by ...

handle. excess glucose is femented to ethanol and the oxidative enzymes an attenuated to
restrict glucose oxidation (Cappella and Dhujati, 1990; Sonnleitner and Kappeii, L 986).
The effects of glucose flux (q~) on the activities of the pacing enzyme pools cm be
described according to the foiiowing expressions:
Ut) is incorporated to consider the adaptive characteristics in the modes of control and
regdation of the enzyme activities* The values of CI and C2 are normaiized and Vary
between O and 1. The fonns of the above two equations were adapted fiom van Dedem
and Moo-Young (1973). Function L(t) represents the time lag of the transient state
between inoculation and the onset of exponential growth. Based on the experimental
observation of the sigrnoidal increase in specific growth rate during the lag phase. L(t) is
approximated by the foiiowing exponential function:
where tb is hg the, which depends on the recombinant strain, medium used and
inoculum conditions.
As glucose is depleted Ui batch cdnire, ethanol and acetaldehyde dehydrogenases
are induced graduaiiy and ethanol is metabolized by progressive oxidation to acetaldehyde