Fermentation media, equipment and sterilization methods MCQs With Answer

Introduction:

Fermentation media, equipment and sterilization methods are core subjects for B.Pharm students studying bioprocessing and pharmaceutical biotechnology. This topic covers formulation of fermentation media (carbon, nitrogen, trace elements, buffers), design and operation of fermenters (spargers, baffles, agitators, sensors), oxygen transfer (kLa), and contamination control. You will learn practical sterilization methods—autoclaving, dry heat, filtration, SIP/CIP, chemical and radiation sterilants—and validation tools like biological indicators and integrity tests. Understanding media preparation, aseptic technique and equipment sterilization ensures reproducible product quality and regulatory compliance. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the primary purpose of fermentation media?

• To provide nutrients and an optimal environment for microbial growth
• To sterilize the bioreactor
• To act as an antifoam agent
• To measure dissolved oxygen

Correct Answer: To provide nutrients and an optimal environment for microbial growth

Q2. Which compound is most commonly used as a primary carbon source in microbial fermentation media?

• Glucose
• Calcium carbonate
• Sodium chloride
• Magnesium sulfate

Correct Answer: Glucose

Q3. Which of the following is a common complex nitrogen source in fermentation media?

• Yeast extract
• Sodium hydroxide
• Polysorbate 80
• Activated carbon

Correct Answer: Yeast extract

Q4. Which trace element is frequently required in micro-molar amounts for enzyme cofactors in fermentation?

• Iron
• Sucrose
• Glycerol
• Polystyrene

Correct Answer: Iron

Q5. What is the primary role of a buffer (e.g., phosphate buffer) in fermentation media?

• Maintain stable pH during microbial metabolism
• Provide carbon for cell growth
• Increase foam formation
• Act as a sterilant

Correct Answer: Maintain stable pH during microbial metabolism

Q6. Which sterilization method is best for heat-sensitive vitamins and antibiotics in media?

• Sterile filtration through a 0.22 µm membrane
• Autoclaving at 121°C for 15 minutes
• Dry heat at 160°C for 2 hours
• Gamma irradiation at high dose

Correct Answer: Sterile filtration through a 0.22 µm membrane

Q7. Typical standard autoclave conditions for media sterilization are:

• 121°C, 15 psi, 15 minutes
• 100°C, atmospheric pressure, 60 minutes
• 160°C, 2 hours
• 200°C, 30 minutes

Correct Answer: 121°C, 15 psi, 15 minutes

Q8. Dry heat sterilization is especially suitable for which items?

• Glassware and metal instruments
• Sterile media containing heat-sensitive vitamins
• Disposable plastic filters
• Bioreactor stainless-steel seals

Correct Answer: Glassware and metal instruments

Q9. What is the typical particle size efficiency specification for HEPA filters in cleanrooms?

• 0.3 µm
• 5 µm
• 10 µm
• 50 µm

Correct Answer: 0.3 µm

Q10. For final sterilization of a liquid media to remove bacteria, which pore size membrane filter is routinely used?

• 0.22 µm
• 1.0 µm
• 5.0 µm
• 10.0 µm

Correct Answer: 0.22 µm

Q11. What does SIP (Steam-In-Place) accomplish in a fermentation facility?

• Sterilizes the interior surfaces of fermenters and piping using steam
• Removes particulate matter by filtration
• Measures oxygen transfer coefficient
• Adds antifoam automatically

Correct Answer: Sterilizes the interior surfaces of fermenters and piping using steam

Q12. CIP stands for Clean-In-Place and is primarily used to:

• Remove residues and soils from equipment without disassembly
• Sterilize media containing spores
• Measure pH online
• Filter air into the headspace

Correct Answer: Remove residues and soils from equipment without disassembly

Q13. Which biological indicator organism is commonly used to validate steam (moist heat) sterilization?

• Geobacillus stearothermophilus spores
• Saccharomyces cerevisiae cells
• Escherichia coli vegetative cells
• Penicillium spores

Correct Answer: Geobacillus stearothermophilus spores

Q14. Which test is commonly used to check integrity of sterilizing membrane filters after use?

• Bubble point test
• pH titration
• Optical density reading
• Gram staining

Correct Answer: Bubble point test

Q15. What is the main purpose of adding antifoam agent to a fermentation?

• Reduce excessive foam that impedes oxygen transfer
• Increase cell growth rate
• Raise media pH
• Sterilize the culture

Correct Answer: Reduce excessive foam that impedes oxygen transfer

Q16. In a fermenter, the sparger is used to:

• Disperse air or oxygen as fine bubbles into the liquid
• Stir the culture mechanically
• Measure temperature
• Control pH automatically

Correct Answer: Disperse air or oxygen as fine bubbles into the liquid

Q17. Baffles installed in a stirred tank fermenter primarily improve:

• Mixing efficiency and oxygen transfer
• Sterility of incoming media
• Chemical sterilant concentration
• Membrane filter pore size

Correct Answer: Mixing efficiency and oxygen transfer

Q18. The parameter kLa in bioprocessing represents:

• Volumetric oxygen mass transfer coefficient
• Foam formation rate
• Sterilization temperature
• Carbon source concentration

Correct Answer: Volumetric oxygen mass transfer coefficient

Q19. Which statement best describes batch fermentation?

• No fresh substrate is added during the run; system is closed
• Continuous removal and addition of medium maintains steady state
• Substrate is continually fed while culture is removed
• Cells are immobilized on a solid matrix only

Correct Answer: No fresh substrate is added during the run; system is closed

Q20. Fed-batch fermentation is characterized by:

• Adding substrate during cultivation without removing culture
• Continuous input and output maintaining steady state
• Instant sterilization of product stream
• Use of only defined media components

Correct Answer: Adding substrate during cultivation without removing culture

Q21. In continuous (chemostat) fermentation the system maintains:

• Steady state by continuous addition of medium and removal of culture
• Closed conditions with no additions
• Intermittent sterilization cycles
• Only solid substrates

Correct Answer: Steady state by continuous addition of medium and removal of culture

Q22. Which observation is an early indication of contamination in a fermentation run?

• Unexpected turbidity increase or sudden pH change
• Stable dissolved oxygen readings
• Expected product titer rise
• Proper bubble formation at the sparger

Correct Answer: Unexpected turbidity increase or sudden pH change

Q23. Ethylene oxide gas sterilization is particularly useful for:

• Heat-sensitive medical devices and equipment
• Final sterilization of sterile liquids
• Sterilizing large volumes of media
• Removing endotoxins from solutions

Correct Answer: Heat-sensitive medical devices and equipment

Q24. Gamma irradiation is most commonly used to sterilize:

• Disposable plastics and prepackaged equipment
• Sterile fermenter stainless steel parts in place
• High-volume liquid media
• Autoclave biological indicators

Correct Answer: Disposable plastics and prepackaged equipment

Q25. Tyndallization refers to which sterilization concept?

• Intermittent boiling over successive days to inactivate spores
• High-pressure steam sterilization at 121°C
• Sterile filtration through 0.22 µm filters
• Dry heat sterilization at 200°C

Correct Answer: Intermittent boiling over successive days to inactivate spores

Q26. Which organism is commonly used as a biological indicator for dry heat sterilization validation?

• Bacillus atrophaeus spores
• Geobacillus stearothermophilus spores
• Saccharomyces cerevisiae cells
• Escherichia coli K12 cells

Correct Answer: Bacillus atrophaeus spores

Q27. What type of filter is used as a prefilter to remove high particulate load before final sterilizing filtration?

• Depth filter
• 0.22 µm membrane filter
• HEPA filter
• Nanofiltration membrane

Correct Answer: Depth filter

Q28. For aseptic sampling from a fermenter during operation, which device is most appropriate?

• Sterile sampling valve with septum
• Open pipette sampling through the top hatch
• Non-sterile tubing transfer
• Room air venting

Correct Answer: Sterile sampling valve with septum

Q29. Heat penetration time during autoclaving depends mainly on:

• Container size and composition
• Media color
• Type of stirrer used in fermenter
• pH of the solution

Correct Answer: Container size and composition

Q30. To remove viruses from a liquid by filtration, which approximate pore size is required?

• 0.02 µm (20 nm)
• 0.22 µm
• 0.45 µm
• 1.0 µm

Correct Answer: 0.02 µm (20 nm)

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com