# Fermentation Technology Questions and Answers – Microbial Growth Kinetics – Continuous Culture

This set of Fermentation Technology Multiple Choice Questions & Answers (MCQs) focuses on “Microbial Growth Kinetics – Continuous Culture”.

1. The Continuous culture is a/an ______ culture system.
a) Open
b) Closed
c) Isolated
d) Semi-closed

Explanation: The Continuous culture is an open culture system where the nutrients are added in a continuous fashion. The batch culture is a closed system with limiting the number of nutrients and fed-batch culture is a semi-closed system.

2. During continuous culture/fermentation, nutrients in the fermenter are utilized at a fast rate.
a) True
b) False

Explanation: In Continuous Fermentation, the nutrients in the fermenter are added continuously and are utilized by microbes at a fast rate whereas, in batch culture, the nutrients are utilized at a slow rate.

3. Which Growth phase is usually longer in continuous culture?
a) Log
b) Exponential
c) Stationary
d) Death

Explanation: Exponential phase is usually longer as the nutrients are added continuously and therefore the microbes show exponential growth. This is the phase of the maximum growth rate where the growth of cells usually increases.

4. What is the dilution rate (D)?
a) D = F/V
b) D = V/F
c) D = µF
d) D = µD

Explanation: The flow of medium into the vessel is called dilution rate, and is defined as,
D = F/V
where V is volume and F is the flow rate.

5. What is the unit of flow rate (F)?
a) dm3 h-1
b) km3 h-1
c) ml3 h-2
d) dm2 h-2

Explanation: Flow rate is the product of dilution rate and volume of the vessel. The unit of dilution rate is h-1 and that of the volume of the vessel is dm3. Therefore, the unit of flow rate is dm3 h-1.
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6. The chemostat and turbidostat are the types of bioreactors that are used in which of the following culture?
a) Batch culture
b) Continuous culture
c) Fed-Batch culture
d) Solid State culture

Explanation: Turbidostat is a microbiological culture device, similar to a chemostat, which has feedback between the turbidity of the culture vessel and the dilution rate. Continuous fermentation is useful in the production of potentially more important products than batch fermentation.

7. Which scientist(s) gave a full kinetic description of external and internal feedback system?
a) Monod
b) Pirt
c) Bull
d) Harte and Webb

Explanation: Pirt in 1975 gave a full description of these feedback systems and he also discussed the kinetics of product of microbial culture.

8. A multistage system is shown below. Label the stages 1 and 2.

a) 1-Medium inlet and 2-culture effluent
b) 1-Mixing chamber and 2-culture effluent
c) 1-Medium inlet and 2-Liquid reservoir
d) 1-Culture effluent and 1-Medium Inlet

Explanation: Multistage system is a chemostat that is separated in different stages where the medium inlet is followed by culture effluent which is followed by effluent collection or subsequent stages.

9. What are the disadvantages of continuous culture?
a) It can rarely be used for other productions
b) The growth rate is higher
c) If contamination occurs, huge volumes of the product may be lost
d) It is very useful for processes involving the production of primary metabolites

Explanation: Continuous culture is an open culture system and therefore, there are very high chances of microbial contamination. Thus, a huge amount of product may be lost. The other three options include the advantages of continuous culture.

10. In continuous culture, the turnover rate is high.
a) True
b) False

Explanation: The turnover rate in continuous culture is higher because the nutrients are added constantly and continuously and thus the products are produced in a high amount.

11. Which of the following is not the type of continuous brewing?
b) Multistage system
c) Tower system
d) Extract brewing

Explanation: The main types of continuous brewing are cascade, multisystem and the tower system. The extract brewing is a type of home brewing. The continuous brewing is useful in converting the wort into beer.

12. All the constituents of medium are excess in _______
a) Chemostat
b) Turbidostat
c) Batch culture
d) Fed-Batch culture

Explanation: In the continuous culture all the constituents of the medium are in excess in the chemostat. The batch and the fed-batch culture contains a limited amount of nutrients in the medium.

13. Which carbon source has great application for SCP production?
a) Cellulose
b) Starch
c) Methanol
d) Methane

Explanation: Cellulose has been investigated as a potential carbon source for SCP production and was reviewed by Callihan et al and Woodward. Cellulose is a compound present in the cell wall of plants. Humans do not have an enzyme that can digest cellulose, therefore cellulose directly gets excreted in the form of roughage.

14. The continuous culture or fermentation can be used to produce _______
a) Biomass
b) Primary metabolites
c) Secondary metabolites
d) Antibodies

Explanation: The continuous culture or fermentation can be used to produce primary metabolites such as amino acids, SCP, organic acids, etc. Biomass, Secondary metabolites, and a few primary metabolites are produced by batch fermentation.

15. Which of the following is NOT correct for Continuous fermentation?
a) Setup is not changed from outside once the fermentation has started
b) Nutrients are added many times
c) Closer to the natural environment
d) The small size of fermenters are required

Explanation: In continuous fermentation, the process operates continuously with a steady flow of nutrients and removal of waste products, maintaining the culture in a steady state. It runs without the need for changing the setup from outside once the fermentation has begun. It is closer to natural environments where conditions are relatively stable. It is not inherently associated with the requirement of small fermenters. The size of the fermenter depends on the desired scale of production and not on nature or type of fermentation process.

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