Fermentation Reactors – Section 2

1. In a glucose-yeast extract medium, Lactococcus lactis has a maximum specific growth rate (um) of 1.23 h-1 What would be the specific growth rate of this organism at a steady state in a 4-liter reactor being fed at 2 liters per hour?

A. 0.5 h-1
B. 1.2 h-1
C. 2.4 h-1
D. 4 h-1

Correct Answer: A. 0.5 h-1

2. Which of the following is not correct with regards to continuous cultures?

A. The major industrial-scale application of continuous cultures is in wastewater treatment
B. Mutation and contamination present a major risk to the operation of continuous cultures for the production of metabolites
C. The continuous cultures is very useful for the production of pharmaceuticals
D. Continuous cultures have an advantage that they do not need to shut down as regularly as batch culture reactor

Correct Answer: C. The continuous cultures is very useful for the production of pharmaceuticals

3. In a plug flow reactor, the highest concentration of substrates is exposed to the cells that

A. are near the effluent or exit of the reactor
B. are in the midway along the reactor
C. are located near the entrance of feed
D. are near the wall of the reactor

Correct Answer: C. are located near the entrance of feed

4. In an activated sludge process, the biomass is recycled to

A. increase the efficiency of the process
B. reduce sludge volumes
C. increase the concentration of cells
D. all of the above

Correct Answer: D. all of the above

5. A strain of Escherichia coli has a maximum specific growth rate of 0.8 h-1 on a glucose-based medium. If this organism is being grown in a chemostat with a dilution rate of 1.2 h-1, then at steady state the concentration of E. coli in the same medium will

A. increase
B. be zero
C. change randomly
D. decrease

Correct Answer: B. be zero

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