# Fermentation Technology Questions and Answers – Continuous Sterilization

This set of Fermentation Technology Multiple Choice Questions & Answers (MCQs) focuses on “Continuous Sterilization”.

1. Which of the following time is not included in continuous sterilization?
a) Heating time
b) Cooling time
c) Holding time
d) Sterilization time

Explanation: The continuous sterilization includes the time period of heating where the medium is heated, followed by holding time where the medium is held at a certain temperature and finally the cooling period to restore the medium to the fermentation temperature.

2. The holding time at 135°C will be _________
a) 2.44 minutes
b) 51.9 seconds
c) 18.9 seconds
d) 2.7 seconds

Explanation: The Holding time at 135°C will be 51.9 seconds. This temperature time was calculated to give the value of the Del factor. 2.44 minutes was the holding time at 130°C. 2.7 seconds was the holding time at 150°C.

3. Which of the following is a type of continuous sterilizer?
a) Steam Injector
b) Inertial Impaction
c) Electrostatic attraction
d) Interception

Explanation: There are two types of continuous sterilizers- Indirect heat exchanger and Direct Heat exchanger or steam injectors. The inertial impaction, electrostatic attraction, interception are the types of Filter sterilization.

4. What is the function of the holding loop?
a) It heats the medium
b) It sterilizes the medium
c) It holds the medium
d) It cools the medium

Explanation: The function of the holding loop is to sterilize the medium. The heating coil or loop sterilizes the medium and the cooling loop or coil cools the medium to the fermentation temperature. This is the basic process of continuous sterilization.

5. The sterilization in double spiral heat exchanger is done through ___________
a) Countercurrent mechanism
b) Counter mechanism
c) Symporter mechanism
d) Antiporter mechanism

Explanation: The sterilization in a double spiral heat exchanger is done through Countercurrent mechanism where steam is passed through one spiral and the medium is passed through the other spiral.
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6. Which of the following is the main disadvantage of a direct plate exchanger?
a) Foaming occurs
b) High capital cost
c) If the media contains suspended solids, the plate may get blocked
d) High maintenance

Explanation: The main disadvantage of a direct plate exchanger is that if the media contains suspended solid particles, the plate might get blocked and the medium might not get sterilized. In this case, continuous steam injectors are used which does not get blocked due to suspended solids.

7. The fermenter vessel is sterilized at ____________
a) 20 psi
b) 15 psi
c) 5 psi
d) 10 psi

Explanation: The fermenter vessel is sterilized at 15 psi. The jackets or coils of the fermenter are heated in steam for about 20 minutes. The medium which is sterilized is never added directly to the fermenter vessel until the vessel is sterilized. Otherwise, it may lead to contamination of the medium.

8. Which of the following is not a method of sterilization?
b) Chemical Treatment
c) Ultrasonic treatment
d) Cooling

Explanation: The alternative methods of sterilizations includes radiations, chemical treatment, ultrasonic treatment, heating, filtration. The medium which is to be sterilized is exposed to radiations or certain chemicals that will remove the contamination from the medium.

9. Which of the following is not an antimicrobial chemical agent?
a) Cresol
b) Formaldehyde
c) Acetone
d) Iodine

Explanation: The major antimicrobial chemical agents are phenols like cresol, orthophenylphenol and halogens like Iodine, chloramines. Formaldehyde and Ethylene oxide are also used as chemo sterilizers. Acetone is a cleaning agent used in laboratories.

10. Which of the following wavelengths of radiation has the highest bacterial efficiency?
a) 270 nm
b) 280 nm
c) 265 nm
d) 290 nm

Explanation: The wavelengths around 265 nm has the highest bacterial efficiency. The radiation of 265 nm is absorbed by cellular components, leading to DNA damage and cell death. X-rays and Gamma rays are considered to be more lethal.

11. Which of the following organism can grow with or without oxygen?
a) Obligate aerobes
b) Facultative anaerobes
c) Obligate anaerobes
d) Aerotolerant anaerobes

Explanation: Facultative anaerobes grow with or without oxygen. However, they grow better in the presence of oxygen and obtain their energy through aerobic respiration. If oxygen is absent, they utilize fermentation respiration.

12. Which of the following is the most preferable frequency for ultrasonic sterilization?
a) 500 kHz
b) 300 kHz
c) 600 kHz
d) 400 kHz

Explanation: The most preferable frequency for ultrasonic sterilization is 500 kHz. The ultrasonic vibrations are generated which create the cavitation microbubbles and sterilize the medium.

13. Which of the following is an advantage of continuous sterilization over batch sterilization?
a) Solid matter can be used in media
b) Reduction of fermenter corrosion
c) Lower risk of contamination
d) Easier control

Explanation: The advantages of continuous sterilization over batch sterilization is that the corrosion of the fermenter is reduced. This happens due to the usage of stainless-steel materials which prevents corrosion.

14. The steam is injected into the system via a nozzle.
a) True
b) False

Explanation: The steam is injected into the system via a nozzle. The media reaches the holding loop in the meantime and the steam sterilization occurs which removes the contaminants of the medium.

15. Differential media allows the growth of a certain type of organism and will inhibit the growth of certain microorganisms.
a) True
b) False

Explanation: Differential media is mainly used for differentiation of closely related group of organisms whereas the selective media allows the growth of the certain type of organisms and will inhibit the growth of certain microorganisms.

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