This set of Fermentation Technology Multiple Choice Questions & Answers (MCQs) focuses on “Fermenter Design – Aeration and Agitation”.
1. The purpose of aeration is to provide ___________
a) The medium to organisms
b) The carbon dioxide to organisms
c) The oxygen to organisms
d) The water to organisms
View Answer
Explanation: The main function or purpose of aeration is to provide oxygen to the microorganisms for metabolic requirements. It is the major process of the fermentation process.
2. The Aeration is mainly provided to organisms present in _______
a) Submerged culture
b) Solid State culture
c) Surface culture
d) Batch culture
View Answer
Explanation: The aeration is mainly provided to the microorganisms present in submerged culture. The microorganisms in the submerged culture grow beneath the fermentation media and thus are in less contact with oxygen. Therefore, aeration system is required.
3. The non-agitated fermentations are carried out in vessels of a height/diameter ratio of ________
a) 1:2
b) 5:1
c) 3:2
d) 4:1
View Answer
Explanation: The non-agitated fermentations are carried out in vessels of a height/diameter ratio of 5:1. In such vessels, aeration is sufficient enough to produce high disruption but a tall column of liquid requires greater input energy in compressed air production.
4. The agitator is required to _________
a) Provide air
b) Mixing objectives
c) Purify the product
d) Sterilize the media
View Answer
Explanation: The agitator is required to achieve a number of mixing objectives, e.g. oxygen transfer, heat transfer, fluid and gas-mixing, and maintaining a uniform environment throughout the vessel contents.
5. Which of the following is not the component of aeration and agitation system?
a) Impeller
b) Baffles
c) Stirrer gland and bearing
d) Thermometer
View Answer
Explanation: The structural components of the fermenter involved in aeration and agitation are Impeller or agitator, Baffles, Stirrer glands and bearing, and the sparger or the aeration system.
6. Which of the following agitator consists of vanes in a vertical plane around the circumference?
a) vaned discs
b) disc turbines
c) variable pitch turbines
d) marine propeller
View Answer
Explanation: The disc turbines are the type of agitators that consists of a series of rectangular vanes arranged in a vertical plane or fashion around the circumference of the discs. The disc turbines rotate at a very high speed.
7. Which of the following agitator consists of vanes attached vertically inside?
a) vaned discs
b) disc turbines
c) variable pitch turbines
d) marine propeller
View Answer
Explanation: The vaned discs are the type of agitators that consists of rectangular vanes attached vertically to the underside. Whereas the disc turbines include a series of rectangular vanes attached around the circumference of the discs.
8. Which of the following agitator consists of blades directly attached to a boss on agitator shaft?
a) vaned discs
b) disc turbines
c) rectangular turbines
d) marine propeller
View Answer
Explanation: The blades in the marine propeller are attached directly to a boss on the agitator shaft. In this type of agitator, air bubbles do not initially hit any surface before dispersion by blades.
9. Which of the following is not the type of modern agitator?
a) SCABA
b) Prochem Maxflo
c) Lightning A315
d) New Brunswick Scientific
View Answer
Explanation: The modern agitators include SCABA 6SRGT, Prochem Maxflo T, Lightning A315, Ekato Intermig. A Rushton disc turbine is also a type of disc turbine. New Brunswick Scientific is a type of glass fermenter.
10. Which of the following seal assembly has not been used in stirrer glands and bearings?
a) Stuffing box
b) Bush seal
c) Electric drive
d) Mechanical seal
View Answer
Explanation: The four basic types of seal assembly used in stirrer glands and bearings are the stuffing box or packed-gland seal, the simple bush seal, the mechanical seal, and the magnetic drive. The stirrer shaft can enter from the top, bottom, side of the fermenter vessel.
11. Which of the following is not the use of baffles?
a) Increase the effect of agitation
b) Improve aeration efficiency
c) Improve cooling capacity
d) Improve the fermenter capacity
View Answer
Explanation: The Baffles are metal strips about one-tenth of vessel diameter attached to the wall. They prevent vortex and improve aeration efficiency. Agitation effect is also increased using wider baffles. The cooling coils are attached to the baffles to increase the cooling capacity.
12. Which of the following sparger is made of ceramic or metals?
a) Porous sparger
b) Orifice sparger
c) Nozzle sparger
d) Combined sparger-agitator
View Answer
Explanation: The porous spargers are made up of sintered glass, ceramics, or metals. The size of the bubble produced by it is usually larger than the pore size. It is used in non-agitated vessels.
13. Who developed the combined-agitator sparger?
a) Herbert
b) Rivett
c) Johnson
d) Peterson
View Answer
Explanation: The combined sparger-agitator was developed by Herbert et al. in 1965. The air is introduced via agitator shaft and is emitted through holes drilled in discs between the blades.
14. The nozzle sparger does not get blocked.
a) True
b) False
View Answer
Explanation: The nozzle sparger is a partially closed pipe used to provide a stream of air bubbles. It normally causes low-pressure loss and does not get blocked.
15. The use of flat disc in the turbine is to ensure the bulk of energy consumption occurs at blades.
a) True
b) False
View Answer
Explanation: The Rushton turbine has a flat disc which is useful in the consumption of energy. The size, number of blades, the speed of agitator, and power input in a turbine plays an important role in energy consumption.
Sanfoundry Global Education & Learning Series – Fermentation Technology.
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