In adsorption-based enzyme immobilization, which of the following is a key disadvantage that can compromise stability during operation?
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AIt is possible to separate and purify the enzymes while being immobilized
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BThe enzymes are not usually deactivated by adsorption
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CThe adsorption is a reversible process
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DState of immobilization is very sensitive to solution pH, ionic strength and temperature
Answer
Correct Answer: State of immobilization is very sensitive to solution pH, ionic strength and temperature
Explanation
Introduction:Adsorption immobilization relies on noncovalent interactions such as electrostatics, hydrophobic forces, and hydrogen bonding to attach enzymes to surfaces. While this method is simple and gentle, its noncovalent nature can make the immobilization state labile under changing process conditions.
Given Data / Assumptions:
- Enzyme binding is reversible and depends on surface and solution conditions.
- Process conditions may vary in pH, ionic strength, and temperature.
- Operational stability and leaching risk are concerns.
Concept / Approach:Small changes in pH alter enzyme and surface charge, weakening electrostatic attraction. Increased ionic strength screens charges, promoting desorption. Temperature shifts can disrupt hydrophobic and hydrogen-bond networks. Together these effects raise the risk of enzyme leaching and performance drift, a major disadvantage relative to covalent attachment or entrapment.
Step-by-Step Solution:
1) Recognize adsorption depends on weak, reversible interactions.2) Evaluate how pH, salt, and temperature alter these interactions.3) Predict increased leaching or activity loss with condition changes.4) Consider stabilizing strategies: cross-linking after adsorption or operating at controlled conditions.5) Conclude sensitivity to solution conditions is the key disadvantage.Verification / Alternative check:Repeated cycle tests often show activity decline due to enzyme desorption when ionic strength or pH drifts. Post-adsorption cross-linking (for example, with glutaraldehyde) can mitigate but not always eliminate this issue.
Why Other Options Are Wrong:
- Separation during immobilization: Can be an advantage, not a disadvantage.
- Not usually deactivated: True and actually a benefit of gentle adsorption.
- Reversibility: Describes a characteristic, but the operationally critical drawback is sensitivity to conditions causing desorption.
Common Pitfalls:Assuming adsorption is robust across pH and salt swings. Skipping support pretreatment or blocking steps can increase nonspecific binding and instability.
Final Answer:State of immobilization is very sensitive to solution pH, ionic strength and temperature