(Adapted from Figure 4–20 of Aiba et al.) Mixed cultures of bacteria can develop into pred...

(Adapted from Figure 4–20 of Aiba et al.) Mixed cultures of bacteria can develop into predator–prey relationships. Such a system might be cultures of Alcaligenes faecolis (prey) and Colpidium compylum (predator). Consider two different cells X1 and X2 in a chemostat. Cell X, only feeds on the substrate and cell X2 only feeds on cell X-1.

The growth laws are

(a) For a dilution rate of D = 0.04 h−1, an entering substrate concentration of 250 mg/dm3, initial concentrations of cells of Xu = 25 mg/dm3, X2i= 1 mg/dm3 and of substrate Csi- = 10 mg/dm3, plot CX1 , Cx2, r-gX1 , rgX2 , and Cs as a function of time.

(b) Vary D between 0.01 h−1and 0.1 h−1, and describe what you find.

(c) Vary CS0and CSi- from the base case and describe what you find.

(d) List ways you can work this problem incorrectly.

(e) How could you make this problem more difficult?

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