Biochem - Fermentation Reactors [S2]

Question 1

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

Answer 1

1. 0.5/h

Question 2

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

Answer 2

2. The continuous cultures are very useful for the production of pharmaceuticals

Question 3

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

Answer 3

3. Are located near entrance of feed

Question 4

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

Answer 4

4. All of the above

Question 5

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

Answer 5

5. Be zero

Question 6

6. A fed-batch reactor containing 2 liters of medium and 0.1 g/L of biomass is fed with a medium containing 1 g/L of substrate at 1 liter per hour. If after 10 hours, the concentration of biomass in the reactor was 0.2 g/L, then the biomass produced during the 10-hour period is

Answer 6

6. 2.2 g

Question 7

7. Which of the following organisms will continue their metabolism at high substrate concentrations?

Answer 7

7. Saccharomyces cerevisiae

Question 8

8. Yeast is typically produced in fed batch reactors because

Answer 8

8. All of the above

Question 9

9. Two continuous bioreactors containing the same organisms, fed with the same feed at the same dilution rate were compared. Reactor 1 started with an initial concentration of glucose of 10 g/L, while reactor 2 contained 0.1 g/L of glucose at the start of the process then at steady state

Answer 9

9. The concentration of glucose in reactor 1 would be equal to reactor 2

Question 10

10. In a fluidized bed reactor mixing is achieved by

Answer 10

10. Upward movement of the incoming feed

Question 11

11. The production of an amylase from starch by Aspergillus niger is often performed in a fed-batch fermenter. This is due to the reason that

Answer 11

11. Fed-batch reactor can be used to minimize starch concentrations and thus reduce the viscosity of the medium

Question 12

12. The fastest route of NADH reoxidation is

Answer 12

12. Fermentation

Question 13

13. In fed batch bioreactor modelling, the rate of change in the bioreactor volume is assumed to be equal to

Answer 13

13. Flow rate

Question 14

14. Monoclonal antibodies are typically produced in fed batch reactors because

Answer 14

14. Hybridoma cells yield higher lactate at high glucose concentrations

Question 15

15. In plug flow tubular reactor, the axial velocity profile on cross-section will be

Answer 15

15. Constant

Question 16

16. Production of organic acids in batch culture is generally growth associated phase followed by non-growth associated production. The probable reason for this is that

Answer 16

16. Organic acids uncouple catabolism from anabolism

Question 17

17. The concentration of biomass in a continuous stirred tank reactor is 20 g dry weight per liter. What would be the concentration of biomass in the effluent?

Answer 17

17. Approximately 20 g dry weight per liter

Question 18

18. The ideal tubular-flow fermenter without radial variations is called

Answer 18

18. Plug flow fermenter

Question 19

19. Pseudo-steady state in a continuous reactor refers to a reactor in which

Answer 19

19. Concentration oscillate around a mean value

Question 20

20. The toxicity of organic acids to cells

Answer 20

20. Enhances as the pH falls

Question 21

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

Answer 21

21. Penicillin

Question 22

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

Answer 22

22. Ferment in the presence of high concentrations of sugar and dissolved oxygen

Question 23

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

Answer 23

23. Growth associated

Question 24

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

Answer 24

24. X, and P will be zero while S is equal to the substrate concentration in feed

Question 25

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

Answer 25

25. Less than 0.8/h

Question 26

26. Saccharomyces cerevisiae when grown in high glucose concentration medium, the cells activity depends on which of the following?

Answer 26

26. No effect of dissolved oxygen

Question 27

27. Continuous culture has an advantage over to a batch cultures as

Answer 27

27. All of the above

Question 28

28. In a batch-fed mode, substrate will be added

Answer 28

28. Periodically throughout the fermentation process

Question 29

29. When Escherichia coli grown in a well aerated medium, which of the following will occur?

Answer 29

29. Fructose di-phosphate accumulation inside the cells leading to fermentation