21. Which of the following is best described as secondary metabolite?

A. Acetic acid produced from the oxidation of ethanol
B. Ethanol from the fermentation of glucose
C. Penicillin
D. Citric acid from the partial oxidation of glucose

22. A microorganism which is subjected to the Crabtree effect is most likely to

A. ferment in the presence of low concentrations of sugar and dissolved oxygen
B. respire in the presence of low sugar and high dissolved oxygen concentrations
C. ferment in the presence of high concentrations of sugar and dissolved oxygen
D. respire in the presence of high sugar and low dissolved oxygen concentrations

23. When the product formation is approximately equal to the rate of cell growth, the pattern of product formation is termed as

A. uncoupled
B. growth associated
C. non-growth associated
D. metabolically uncoupled

24. Which of the following would be correct concerning the concentration of biomass (X). growth-limiting substrate (S) and product (P) in a chemostat when the cells have been washed out?

A. X, S, and P will be zero
B. X, S, and P can not be predicted for the above condition
C. X and P will be zero while S is equal to the substrate concentration in the feed
D. None of the above

25. Pseudomonas aeruginosa has a maximum specific growth rate of 0.8 h^-1 in a medium with glucose as a growth-limiting substrate. To prevent washout, the dilution rate must be set to

A. greater than 0.8 h^-1
B. less than 0.8 h^-1
C. equal to 0.8 h^-1
D. 1.6 h^-1