Problem 4 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 So 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: U = US K X +S a. Derive an expression for S in terms of D. um.. K., and X for a steady-state CFSTR (chemostat). b. Derive an equation for S as a function of So. D. Ka. Y's, and u,. c. If So increases twofold, by how much will S increase