Cell disruption for product recovery MCQs With Answer

Introduction: Cell disruption is a critical step in recovering intracellular and periplasmic pharmaceutical products such as recombinant proteins, enzymes, and vaccines. For M.Pharm students, understanding the principles, mechanisms, advantages and limitations of different disruption techniques—mechanical (high-pressure homogenization, bead milling, sonication), chemical (detergents, chaotropes), enzymatic, and physical (freeze–thaw, osmotic shock)—is essential for designing robust downstream processes. This quiz set focuses on method selection, scale-up issues, process parameters, and impacts on product quality (denaturation, proteolysis, endotoxin release). The questions emphasize practical considerations for product recovery, contamination control, and preservation of biological activity during cell breakage and subsequent purification.

Q1. What is the primary objective of cell disruption in downstream processing?

• To sterilize the culture broth
• To release intracellular or periplasmic product into the process stream
• To increase cell biomass
• To reduce dissolved oxygen

Correct Answer: To release intracellular or periplasmic product into the process stream

Q2. Which cell disruption method is most suitable and commonly used for large-scale bacterial processing?

• Probe sonication
• High-pressure homogenization
• Repeated freeze–thaw cycles
• Manual Dounce homogenizer

Correct Answer: High-pressure homogenization

Q3. What is the dominant mechanical mechanism by which bead milling disrupts microbial cells?

• Chemical solubilization of membranes
• Shear and impact forces from collisions between beads and cells
• Electrostatic destabilization
• Osmotic gradient formation

Correct Answer: Shear and impact forces from collisions between beads and cells

Q4. What is a major drawback of high-pressure homogenization for sensitive protein products?

• It cannot be scaled up
• It always eliminates endotoxin
• Heat generation and extreme shear can denature proteins
• It is ineffective for bacteria

Correct Answer: Heat generation and extreme shear can denature proteins

Q5. Sonication disrupts cells primarily through which physical phenomenon?

• Osmotic swelling
• Mechanical cutting by blades
• Cavitation-induced microjets and shock waves
• Freeze-induced crystal formation

Correct Answer: Cavitation-induced microjets and shock waves

Q6. Lysozyme is most effective against which class of microorganisms when used alone?

• Gram-negative bacteria
• Yeast
• Gram-positive bacteria
• Mammalian cells

Correct Answer: Gram-positive bacteria

Q7. What is the main mechanism by which freeze–thaw cycles disrupt cells?

• Enzymatic digestion of the cell wall
• Shear by high-pressure flow
• Ice crystal formation that ruptures membranes
• Detergent-mediated solubilization

Correct Answer: Ice crystal formation that ruptures membranes

Q8. For recovering a recombinant intracellular protein that is heat- and shear-sensitive, the most critical selection criterion for a disruption method is:

• Operator familiarity with equipment
• Product sensitivity to heat and shear
• Lowest capital cost
• Ability to work at high cell density only

Correct Answer: Product sensitivity to heat and shear

Q9. Lysis of Gram-negative bacteria commonly releases which contaminant that complicates downstream purification?

• Chitin
• Endotoxin (lipopolysaccharide)
• Cellulose
• Lignin

Correct Answer: Endotoxin (lipopolysaccharide)

Q10. Which disruption method is especially effective for yeast cells with tough cell walls at industrial scale?

• Osmotic shock
• Bead milling
• Gentle nitrogen cavitation
• Lysozyme alone

Correct Answer: Bead milling

Q11. The French press disrupts cells primarily by:

• Enzymatic cleavage of peptidoglycan
• Pressure drop across a narrow valve causing shear and cavitation
• Magnetic field oscillation
• Detergent-mediated lysis

Correct Answer: Pressure drop across a narrow valve causing shear and cavitation

Q12. Addition of DNase after cell disruption is used to:

• Prevent endotoxin release
• Reduce viscosity by degrading released DNA
• Increase particle size for filtration
• Inhibit proteases

Correct Answer: Reduce viscosity by degrading released DNA

Q13. Which operational condition during cell disruption is most likely to cause protein denaturation and loss of activity?

• Maintaining low temperature
• Prolonged or intense sonication causing local heating and radicals
• Addition of protease inhibitors
• Performing disruption at neutral pH

Correct Answer: Prolonged or intense sonication causing local heating and radicals

Q14. Which disruption technique is readily operated as a continuous, high-throughput unit operation suitable for industrial manufacture?

• High-pressure homogenizer
• Freeze–thaw cycles
• Probe sonication in batch tubes
• Manual Dounce homogenizer

Correct Answer: High-pressure homogenizer

Q15. Osmotic shock is primarily used to release which cellular fraction in Gram-negative bacteria?

• Cytosolic proteins
• Periplasmic proteins
• Nuclear proteins
• Membrane lipids only

Correct Answer: Periplasmic proteins

Q16. Inclusion bodies formed during recombinant expression typically consist of:

• Soluble, correctly folded protein complexes
• Insoluble aggregates of misfolded recombinant protein
• Cell wall fragments only
• Lipid droplets

Correct Answer: Insoluble aggregates of misfolded recombinant protein

Q17. In a high-pressure homogenizer, which change generally increases the extent of cell disruption per pass?

• Decrease the operating pressure
• Increase the operating pressure
• Reduce the number of passes through the valve
• Raise the processing temperature intentionally

Correct Answer: Increase the operating pressure

Q18. Which gentle disruption technique is often chosen to preserve intact organelles for subcellular fractionation in eukaryotic cells?

• Probe sonication at maximum power
• Nitrogen (N2) cavitation
• Bead milling with small beads at high speed
• Repeated freeze–thaw at high rates

Correct Answer: Nitrogen (N2) cavitation

Q19. A critical downstream issue immediately following cell disruption that can degrade target protein is:

• Proteolysis by released intracellular proteases
• Increase in cell growth rate
• Enhanced oxygen transfer
• Spontaneous refolding into native structure

Correct Answer: Proteolysis by released intracellular proteases

Q20. Which operational control is most effective to limit heat build-up and thermal damage during intensive mechanical disruption?

• Operate continuously at maximum duty without cooling
• Use cooling (jacket/heat exchanger) and intermittent duty cycles
• Increase input solids concentration to trap heat
• Avoid adding protease inhibitors

Correct Answer: Use cooling (jacket/heat exchanger) and intermittent duty cycles

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