This set of Fermentation Technology Multiple Choice Questions & Answers (MCQs) focuses on “Batch Sterilization”.
1. Which of the following is not a type of sterilization?
a) Batch
b) Continuous
c) Filter
d) Submerged
View Answer
Explanation: The types of sterilizations are Batch sterilization, Continuous sterilization, Filter sterilization. Submerged is a type of fermentation where microorganisms are grown in the liquid medium.
2. What do you mean by sterilization?
a) Purification of products
b) Recovery of products
c) Elimination of contamination
d) Formulation of media
View Answer
Explanation: Sterilization is the process of removal of unwanted organisms like bacteria, fungi, etc. from the fermentation medium. Purification and recovery of products are part of downstream processing and formulation of media is the preparation of the fermentation media.
3. Which of the following instrument works on the principle of batch sterilization?
a) Incubator
b) Autoclave
c) Centrifuge
d) LAF
View Answer
Explanation: Autoclave is an instrument that works on the principle of batch sterilization. It is used to kill germs which invade the fermentation media. The incubator provides optimum conditions for the growth of microorganisms. Laminar Air Flow (LAF) prevents the contamination of biological samples. A centrifuge is used in the separation of liquids or gases.
4. The highest feasible temperature for batch sterilization is ________
a) 124°C
b) 120°C
c) 122°C
d) 121°C
View Answer
Explanation: The highest temperature, which appears to be feasible for batch sterilization is 121°C so the procedure should be designed such that exposure of the medium to this temperature is kept to a minimum. The nutrients might get depleted if there is a long exposure.
5. The destruction of microorganisms by moist heat is described by ______________
a) Zero-order reaction
b) First-order reaction
c) Third-order reaction
d) Second-order reaction
View Answer
Explanation: The destruction of microorganisms by moist heat or stream is described by First-order reaction and may be represented by the equation, -dN/dt = kN, where N is the number of viable organisms, t is the time of sterilization and reaction rate constant.
6. The contamination can be avoided by sterilizing the fermenter vessels only.
a) True
b) False
View Answer
Explanation: The contamination can be avoided by sterilizing the fermenter, using pure inoculum to start the fermentation, sterilizing the medium, sterilizing all the components of the fermenter, and maintaining the aseptic conditions.
7. If the foreign microorganism invades the fermentation, which of the following is not likely to occur?
a) The medium will not allow the growth of contaminant
b) The contaminant may outgrow the production organism
c) The contaminant may contaminate the final product
d) The contaminant may degrade the final product
View Answer
Explanation: If the foreign microorganism invades the fermenter, the medium will allow the growth of the contaminant along with the production organism. In case, it may outgrow the production organism and contaminate or degrade the final product of the fermenter.
8. Which of the following reaction occurs during the sterilization which results in browning of media?
a) Sandmeyer reaction
b) Maillard reaction
c) Cannizzaro reaction
d) Gattermann reaction
View Answer
Explanation: Maillard reaction is the most common reaction which occurs during the sterilization process. It results in the browning of the medium as well as the nutrient quality is degraded. The other three- Sandmeyer, Cannizzaro, Gattermann- are the types of organic chemical reactions.
9. The long exposure of batch sterilization may lead to ____________
a) Purification of media
b) Recovery of media
c) Degradation
d) Good quality of product
View Answer
Explanation: The long exposure of batch sterilization may lead to degradation of the medium. The medium may lose all its nutritional quality. The heat labile components like proteins, vitamins get degraded due to overheating.
10. Which scientists introduced the term ‘Del factor’?
a) Deindoerfer and Humphrey
b) Jacob and Monod
c) Banks and Corbett
d) Richards
View Answer
Explanation: The ‘Del Factor’ was introduced by Deindoerfer and Humphrey as a design criterion for sterilization. It is also called the Nabla factor, sterilization criterion and is represented by the term ∇.
11. What is the advantage of batch sterilization over continuous sterilization?
a) Superior maintenance of medium quality
b) Ease of scale-up
c) Automatic control
d) Lower equipment costs
View Answer
Explanation: The advantage of batch sterilization over continuous sterilization is that it has lower capital of equipment costs. Whereas the medium quality, automatic control, ease of scale-up are the advantages of continuous sterilization.
12. The equation for Del factor is _____________
a) ∇ = ln (N0/Nt)
b) ∇ = ln (Nt/N0)
c) ∇ = ln (N0)
d) ∇ = ln (N0Nt)
View Answer
Explanation: The Del Factor is expressed as, ∇ = ln (N0/Nt), where N0 is the number of viable organisms present initially at the time of sterilization treatment and Nt is the number of viable organisms after the treatment.
13. The Del Factor decreases as the initial number of organisms _____________
a) Decreases
b) Increases
c) Remains constant
d) Becomes zero
View Answer
Explanation: The Del factor decreases as the initial number of viable organisms decreases. This happens because the Del factor is directly proportional to the initial number of viable organisms and is inversely proportional to the viable organisms after the sterilization treatment. That is why it decreases.
14. How long does it take for the autoclave to complete its cycle?
a) 30-35 minutes
b) 50 min to 1 hr
c) 15-20 minutes
d) 10-15 minutes
View Answer
Explanation: The autoclave completes its cycle within 15-20 minutes at 121°C. An autoclave is similar to a pressure cooker that uses steam to kill the germs. An autoclave can sterilize solids, liquids, etc.
15. The Del factor increases with an increase in the size of the fermenter.
a) True
b) False
View Answer
Explanation: The Del factor is directly proportional to the number of viable organisms at the start of the sterilization process. Thus, if the size of fermenter increases, the number of starting organisms will also increase and this leads to an increase in the Del factor.
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