Discussion
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- Question
During fermentation, the saturation concentration of oxygen was reduced from 7 ppm. to 1 ppm. Which one of the following conclusions can be drawn?
Options- A. Microbial growth is oxygen limited since the oxygen concentration is lesser than the saturation concentration
- B. Microbial growth is not oxygen limited since the oxygen concentration is lesser than the saturation concentration
- C. Experimental error leads to the reduction
- D. No conclusion can be drawn
- Correct Answer
- No conclusion can be drawn
- 1. For aerated mixing vessels in an aqueous solution, the mass transfer coefficient (kL) co-relating power consumption (Pm) and fermenter volume (V) can be expressed as
Options- A. kL ? (Pm/V)0.33
- B. kL ? (Pm/V)0.66
- C. kL ? (Pm/V)0.50
- D. kL ? (Pm/V) Discuss
- 2. Flooding is a condition/phenomenon which occur in a bioreactor when
Options- A. The air escapes without being distributed by the agitator
- B. The fermenter medium spills out the reactor due to foaming
- C. The volume of foam is more than the volume of broth
- D. None of the above Discuss
- 3. Which of the following is correct for the off-centre impellers?
Options- A. Off-centre impellers can be used with any size reactor
- B. Off-centre impellers should only be used with reactors with volumes less than 10 m3
- C. The impeller should never be placed in an off-centre position
- D. Off-centre impellers can be used when volume is greater than 10 m3 Discuss
- 4. A cylindrical reactor fitted with Rushton Turbine has a liquid volume of 100,000 litres. It has an aspect ratio (the ratio of the channel height to the width) of 2:1. The diameter of the impeller should be approximately:
Options- A. 1.3 m
- B. 3.3 m
- C. 5.3 m
- D. 7.3 m Discuss
- 5. Pure oxygen, if used instead of air will increase oxygen transfer rates because
Options- A. the saturation concentration of oxygen is higher
- B. the bubble size is smaller
- C. the oxygen transfer coefficient is larger
- D. the partial pressure of oxygen in the gas phase is lower Discuss
- 6. A fermentation system has a KLa of 3 s-1 and a C0* of 5 ppm of O2. If the bulk liquid is completely depleted of oxygen, then the oxygen transfer rate will be equal to
Options- A. zero
- B. 15 mg.l-1.s-1
- C. 10 mg.l-1.s-1
- D. 5 mg.l-1.s-1 Discuss
- 7. Impeller damage can be minimized by
Options- A. using specially designed axial flow impellers
- B. using radial flow impellers
- C. using Intermig impellers
- D. all of the above Discuss
- 8. In aerobic microorganisms cultures radial flow impellers are used because
Options- A. they provide energy efficient high turbulent mixing conditions
- B. they provide low shear mixing conditions
- C. they provide high shear mixing conditions
- D. they ensure that bubble size is maximized leading to high oxygen transfer rates Discuss
- 9. A fermentation system has a KLa of 3 s-1 and a C0* of 5 ppm of O2. If the bulk liquid is saturated with oxygen then the oxygen transfer rate will be equal to
Options- A. zero
- B. 3 mg.l-1.s-1
- C. 5 mg.l-1.s-1
- D. 15 mg.l-1.s-1 Discuss
- 10. If the stirrer speed is too slow, bubbles will accumulate and coalescese under the impeller. This phenomenon is known as a
Options- A. coalesced impeller
- B. flooded impeller
- C. river impeller
- D. dry impeller Discuss
Agitation and Aeration problems
Search Results
Correct Answer: kL ? (Pm/V)0.33
Correct Answer: The air escapes without being distributed by the agitator
Correct Answer: Off-centre impellers should only be used with reactors with volumes less than 10 m3
Correct Answer: 1.3 m
Correct Answer: the saturation concentration of oxygen is higher
Correct Answer: 15 mg.l-1.s-1
Correct Answer: using specially designed axial flow impellers
Correct Answer: they provide high shear mixing conditions
Correct Answer: zero
Correct Answer: flooded impeller
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