Biotransformation and bioreactors for pilot and large-scale plant cell culture MCQs With Answer

Introduction: This MCQ collection on Biotransformation and Bioreactors for Pilot and Large-Scale Plant Cell Culture is tailored for M.Pharm students preparing for exams and practical applications in Medicinal Plant Biotechnology. The questions focus on enzymatic conversion of substrates in plant cells, strategies to enhance secondary metabolite production via biotransformation, and the engineering principles of bioreactors used at pilot and industrial scale. Emphasis is placed on reactor types (stirred tank, airlift, perfusion), scale-up parameters (kLa, mixing, shear, oxygen transfer), process control, immobilization, elicitation and downstream considerations. Answers are provided for rapid self-assessment and concept reinforcement.

Q1. What is biotransformation in the context of plant cell cultures?

• Abiotic chemical modification of a drug by industrial catalysts
• Enzymatic conversion of a substrate by plant cells into new metabolites
• Physical breakup of cell aggregates during agitation
• Genetic modification of plants to express new enzymes

Correct Answer: Enzymatic conversion of a substrate by plant cells into new metabolites

Q2. Which phase I reaction is most commonly associated with plant cell biotransformation?

• Glucuronidation
• Oxidation
• Sulfation
• Methylation

Correct Answer: Oxidation

Q3. Phase II biotransformation reactions in plant cells typically involve:

• Hydrolysis of glycosides to aglycones only
• Conjugation of polar groups like glycosylation or glutathione addition
• Direct decarboxylation of metabolites
• Spontaneous oxidation by air

Correct Answer: Conjugation of polar groups like glycosylation or glutathione addition

Q4. Which plant cell culture system is most suited for continuous biotransformation at pilot scale?

• Shake-flask batch culture
• Stirred-tank reactor with continuous feeding and perfusion
• Static callus culture on solid media
• Small microtiter plate culture

Correct Answer: Stirred-tank reactor with continuous feeding and perfusion

Q5. What is the main advantage of immobilizing plant cells for biotransformation?

• Prevents nutrient uptake so cells stay inactive
• Allows repeated or continuous use of biocatalyst while reducing shear damage
• Automatically increases oxygen solubility in medium
• Guarantees monoclonal populations

Correct Answer: Allows repeated or continuous use of biocatalyst while reducing shear damage

Q6. Which parameter is most critical to scale-up when maintaining similar oxygen transfer between pilot and large-scale bioreactors?

• Impeller diameter only
• Power per unit volume (P/V) and volumetric mass transfer coefficient (kLa)
• Ambient room temperature
• pH of the feed solution only

Correct Answer: Power per unit volume (P/V) and volumetric mass transfer coefficient (kLa)

Q7. Airlift reactors are often preferred for plant cell cultures because they:

• Create high shear and strong mixing to dissociate aggregates
• Provide low-shear circulation with efficient gas exchange and gentle mixing
• Require complex impellers and high maintenance
• Are best for immobilized bacteria only

Correct Answer: Provide low-shear circulation with efficient gas exchange and gentle mixing

Q8. Elicitation in plant cell cultures is used to:

• Sterilize the culture medium
• Stimulate secondary metabolite production by mimicking stress signals
• Increase cell lysis for easier downstream processing
• Decrease substrate uptake rates

Correct Answer: Stimulate secondary metabolite production by mimicking stress signals

Q9. Which monitoring parameter is essential for avoiding oxygen limitation during large-scale plant cell culture?

• Conductivity only
• Dissolved oxygen (DO) concentration
• Optical density at 600 nm only
• Color of the medium

Correct Answer: Dissolved oxygen (DO) concentration

Q10. Foam control in large-scale plant cell bioreactors is important because uncontrolled foam can:

• Enhance oxygen transfer dramatically and overload cells
• Cause contamination, block filters, and lead to cell loss
• Sterilize the reactor surface
• Solidify medium components

Correct Answer: Cause contamination, block filters, and lead to cell loss

Q11. Which of the following is a common scale-up strategy to maintain similar hydrodynamic conditions?

• Keep geometric similarity and maintain constant tip speed
• Maintain constant Reynolds number only
• Ensure equal reactor volumes only
• Use identical impeller models with no parameter adjustment

Correct Answer: Keep geometric similarity and maintain constant tip speed

Q12. Hairy root cultures are particularly valuable for biotransformation because they:

• Are bacterial cultures mistaken for plant cells
• Provide high stability, genetic fidelity, and often high secondary metabolite productivity
• Cannot be scaled beyond shake flasks
• Require no oxygen or nutrient supply

Correct Answer: Provide high stability, genetic fidelity, and often high secondary metabolite productivity

Q13. Which downstream challenge is unique to plant cell culture biotransformation products?

• Separation of low-molecular-weight fermentation byproducts only
• Removal of plant cell debris, pigments, and complex glycosylated conjugates
• Evaporation losses typical of volatile solvents
• Filtration is unnecessary for pure extracts

Correct Answer: Removal of plant cell debris, pigments, and complex glycosylated conjugates

Q14. Which factor most directly affects aggregate size in suspended plant cell cultures?

• Ambient laboratory lighting
• Agitation intensity and hydrodynamic shear
• pH meter brand
• Concentration of inert salts only

Correct Answer: Agitation intensity and hydrodynamic shear

Q15. Biotransformation yields in plant cell cultures can be improved by:

• Suppressing enzyme expression through cold shock
• Optimizing precursor feeding, cofactor regeneration, and elicitation timing
• Completely eliminating oxygen from the system
• Using only distilled water as medium

Correct Answer: Optimizing precursor feeding, cofactor regeneration, and elicitation timing

Q16. In a pilot-scale stirred-tank reactor, the primary purpose of a sparger is to:

• Mix liquid by mechanical agitation
• Introduce and distribute gas (air/oxygen) as bubbles into the liquid
• Provide sterilization through heating
• Support the impeller shaft structurally

Correct Answer: Introduce and distribute gas (air/oxygen) as bubbles into the liquid

Q17. kLa (volumetric mass transfer coefficient) depends on which of the following?

• Only the chemical composition of the substrate
• Agitation, aeration rate, bubble size distribution, and medium properties
• Time of day when culture was inoculated
• Number of operators in the facility

Correct Answer: Agitation, aeration rate, bubble size distribution, and medium properties

Q18. Which reactor type is usually avoided for delicate plant cells due to high shear?

• Airlift reactor
• Wave bioreactor
• High-speed stirred-tank reactor with multiple Rushton turbines
• Packed-bed reactor for immobilized cells

Correct Answer: High-speed stirred-tank reactor with multiple Rushton turbines

Q19. A critical regulatory consideration for large-scale production of plant-derived biotransformation products is:

• Using non-pharmaceutical grade reagents is allowed without record
• Demonstrating batch-to-batch consistency, impurity profiling, and validated cleaning/sterility
• Regulatory authorities do not require documentation for plant-based products
• Only raw material origin matters, not processing controls

Correct Answer: Demonstrating batch-to-batch consistency, impurity profiling, and validated cleaning/sterility

Q20. Which control strategy helps maintain product quality during scale-up of a plant cell biotransformation process?

• Ignoring metabolic markers and focusing only on biomass
• Implementing PAT (process analytical technology) for real-time monitoring of metabolites, DO, pH and adjusting feeds
• Switching media composition randomly between batches
• Turning off aeration intermittently to reduce costs

Correct Answer: Implementing PAT (process analytical technology) for real-time monitoring of metabolites, DO, pH and adjusting feeds

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