Introduction
Configuration and application of bioreactors MCQs With Answer is designed for M.Pharm students to deepen understanding of bioreactor types, design features, and operational strategies used in pharmaceutical bioprocessing. This set of focused multiple-choice questions covers key topics such as stirred-tank, airlift, packed-bed and single-use systems, oxygen transfer (kLa), mixing, sparging, scale-up criteria, perfusion and immobilized cell reactors, sensors, and sterilization practices. Each question is rooted in practical application and control considerations encountered in drug development and manufacturing. Use these MCQs to test conceptual knowledge, prepare for exams, and reinforce problem-solving skills relevant to bioprocess engineering and regulatory expectations.
Q1. What is the primary purpose of a bioreactor in pharmaceutical bioprocessing?
- To store sterile media for later use
- To provide a controlled physiochemical environment for biological reactions
- To filter and package the final drug product
- To synthesize chemical catalysts for reactions
Correct Answer: To provide a controlled physiochemical environment for biological reactions
Q2. Which bioreactor configuration is most commonly used for bacterial and yeast fermentations at laboratory and industrial scale?
- Bubble column reactor
- Airlift reactor
- Stirred-tank reactor (STR)
- Packed-bed reactor
Correct Answer: Stirred-tank reactor (STR)
Q3. The volumetric mass transfer coefficient (kLa) is best described as:
- The rate of biomass production per liter per hour
- The coefficient representing volumetric oxygen transfer rate from gas to liquid phase
- The ratio of gas flow rate to liquid flow rate
- The diffusion coefficient of oxygen in cells
Correct Answer: The coefficient representing volumetric oxygen transfer rate from gas to liquid phase
Q4. Which bioreactor is most suitable for shear-sensitive mammalian cell cultures commonly used in biologics production?
- High-speed stirred-tank reactor with Rushton turbines
- Disposable wave (rocking) bioreactor
- Bubble column with coarse sparger
- Packed-bed reactor with rigid packing
Correct Answer: Disposable wave (rocking) bioreactor
Q5. When scaling up a fermentation process where oxygen transfer is critical, which scale-up criterion is most appropriate to maintain similar oxygen availability?
- Maintain constant impeller tip speed
- Maintain constant mixing time
- Maintain constant volumetric power input per unit volume (P/V)
- Maintain constant kLa
Correct Answer: Maintain constant kLa
Q6. Which type of sparger typically produces the finest bubbles and therefore can enhance kLa in aerobic fermentations?
- Open pipe sparger
- Porous (sintered) sparger
- Single-orifice ring sparger
- Overflow sparger
Correct Answer: Porous (sintered) sparger
Q7. What is a primary drawback of using chemical antifoam agents in bioreactors?
- They increase oxygen transfer coefficient (kLa)
- They often inactivate enzymes in the broth
- They reduce oxygen transfer efficiency and can coat sensors/membranes
- They sterilize the culture and reduce productivity
Correct Answer: They reduce oxygen transfer efficiency and can coat sensors/membranes
Q8. Which statement best describes a perfusion bioreactor operation?
- Batch operation with no medium exchange
- Fed-batch with intermittent nutrient boluses
- Continuous replacement of culture medium while retaining cells to maintain high cell density
- Plug flow of cells through a tubular reactor with no retention
Correct Answer: Continuous replacement of culture medium while retaining cells to maintain high cell density
Q9. Which reactor type exhibits near plug-flow residence time distribution (narrow RTD) suitable for minimizing back-mixing?
- Continuous stirred-tank reactor (CSTR)
- Plug flow (tubular) reactor
- Bubble column reactor
- Well-mixed chemostat
Correct Answer: Plug flow (tubular) reactor
Q10. Membrane bioreactors in pharmaceutical cell culture are primarily used for:
- Removing volatile impurities from the gas phase
- Cell retention to enable continuous perfusion culture
- Providing additional aeration through membranes
- Packing immobilized enzymes in a fixed bed
Correct Answer: Cell retention to enable continuous perfusion culture
Q11. A common disadvantage of packed-bed bioreactors for immobilized cell processes is:
- Excessive mixing and homogenization
- Channeling and mass transfer limitations within the bed
- High shear that damages cells
- Inability to operate at high cell densities
Correct Answer: Channeling and mass transfer limitations within the bed
Q12. Which impeller type is typically recommended for low-shear axial flow suitable for fragile eukaryotic cells?
- Rushton turbine
- Pitched-blade (marine) impeller
- High-shear turbine with flat blades
- Anchor scraper impeller for viscous fluids
Correct Answer: Pitched-blade (marine) impeller
Q13. The oxygen uptake rate (OUR) from the gas phase to the culture can be expressed as which of the following relationships?
- OUR = kLa × (Cbulk + Csaturation)
- OUR = kLa × (Csaturation − Cbulk)
- OUR = kLa / (Csaturation − Cbulk)
- OUR = Csaturation − (kLa × Cbulk)
Correct Answer: OUR = kLa × (Csaturation − Cbulk)
Q14. One major advantage of single-use (disposable) bioreactors in pharmaceutical manufacture is:
- Unlimited operating temperature range
- Reduced cleaning, sterilization validation and lower cross-contamination risk
- Improved oxygen transfer compared with stainless steel at all scales
- They eliminate the need for process sensors
Correct Answer: Reduced cleaning, sterilization validation and lower cross-contamination risk
Q15. In designing photobioreactors for algal cultivo, the most critical design requirement is:
- Minimizing liquid viscosity
- Maximizing mechanical agitation speed
- Uniform light distribution combined with efficient gas exchange
- Using opaque walls to prevent light penetration
Correct Answer: Uniform light distribution combined with efficient gas exchange
Q16. For in-place sterilization of large stainless-steel bioreactors in pharmaceutical facilities, which method is standard?
- Autoclaving the entire vessel externally
- Steam-in-place (SIP) using pressurized steam
- Gamma irradiation of the assembled vessel
- Dry-heat sterilization at ambient pressure
Correct Answer: Steam-in-place (SIP) using pressurized steam
Q17. Which scale-up criterion is typically chosen when the primary objective is to limit increases in shear stress experienced by cells?
- Maintain constant power input per unit volume (P/V)
- Maintain constant impeller tip speed
- Maintain constant volumetric mass transfer coefficient (kLa)
- Maintain constant Reynolds number
Correct Answer: Maintain constant impeller tip speed
Q18. Compared with a simple bubble column, an airlift reactor offers which advantage for sensitive cell cultures?
- Higher shear from impellers
- Better liquid circulation with lower shear stress
- Greater packing for immobilized cells
- Reduced gas-liquid contact area
Correct Answer: Better liquid circulation with lower shear stress
Q19. Which dissolved oxygen (DO) sensor technology is preferred in modern bioprocessing due to low oxygen consumption and long-term stability?
- Polarographic (Clark-type) electrode
- Galvanic oxygen cell
- Optical (luminescent) DO sensor
- Infrared oxygen analyzer inserted into liquid
Correct Answer: Optical (luminescent) DO sensor
Q20. A chemostat operated as a continuous stirred-tank culture maintains steady-state by controlling which operational parameter?
- Impeller tip speed
- Dilution rate (flow rate of fresh medium relative to vessel volume)
- Intermittent feeding schedule
- Periodic harvest intervals only
Correct Answer: Dilution rate (flow rate of fresh medium relative to vessel volume)
