Bioprocess Engineering 2nd Edition by Fikret Kargi,Michael Shuler

Exercise 18

In a chemostat you know that if a culture obeys the Monod equation, the residual substrate is
independent of the feed substrate concentration. You observe that in your chemostat an in-
crease in causes an increase in the residual substrate concentration. Your friend suggests
that you consider whether the Contois equation may describe the situation better. The Contois
equation (eq. 6.36) is:
a. Derive an expression for S in terms of
and X for a steady-state CFSTR
(chemostat).
b. Derive an equation for S as a function of

c. If
increases twofold, by how much will S increase?