Cell disruption methods: Which option is NOT a physical method for rupturing microbial or mammalian cells in downstream processing?

Difficulty: Easy

Correct Answer: Enzymatic digestion (e.g., lysozyme)

Explanation:


Introduction:
Cell disruption liberates intracellular products before purification. Methods fall into physical (mechanical) and non-physical (chemical/enzymatic) categories. Selecting an approach depends on scalability, cost, product stability, and downstream compatibility.


Given Data / Assumptions:

  • Objective: break cell envelopes to release intracellular contents.
  • Downstream steps expect intact product and manageable debris.
  • We classify according to the primary disruption mechanism.


Concept / Approach:
Physical methods apply shear, impact, or cavitation: bead mills grind cells between beads; homogenizers force slurries through narrow orifices, generating extreme shear and pressure drop; ultrasonication creates microjets and shock waves from bubble collapse. Enzymatic digestion uses biochemical reactions (e.g., lysozyme on peptidoglycan) and is not a physical method.


Step-by-Step Solution:
List physical mechanisms: shear/impact (bead mill), pressure-induced shear (homogenizer), cavitation (ultrasound).Contrast with enzymatic hydrolysis of cell walls which relies on catalysis, not mechanics.Therefore, enzymatic digestion is not a physical method.


Verification / Alternative check:
Pilot-scale runs often compare bead milling or homogenization to enzyme-assisted lysis; documentation consistently categorizes enzymes as chemical/biochemical disruption aids, not physical techniques.


Why Other Options Are Wrong:
Milling, homogenization, and ultrasonication all rely on mechanical energy input and are classic physical methods.


Common Pitfalls:

  • Assuming enzyme treatment is “gentle mechanical” because mixing is used; the primary mechanism is biochemical.
  • Overlooking that enzyme residues can complicate downstream chromatography or regulatory filings.


Final Answer:
Enzymatic digestion (e.g., lysozyme)

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