Which option is not a noncovalent (physical) method of enzyme immobilization among the choices listed?

Introduction:
Immobilization methods are commonly categorized as physical (noncovalent) or chemical (covalent) approaches. Physical methods rely on weak interactions or physical barriers to retain the enzyme, often preserving activity and allowing milder processing conditions.

Given Data / Assumptions:

• Options include adsorption, entrapment, and microencapsulation.
• Question asks which is not a physical method.
• Covalent methods are not listed among the options.

Concept / Approach:
Adsorption uses noncovalent binding to surfaces. Entrapment physically confines enzymes within gels or fibers without direct bonding to the matrix. Microencapsulation encloses enzymes within semi-permeable membranes or capsules. All three are physical methods by definition, so none of them is a non-physical method in this list.

Step-by-Step Solution:

Verification / Alternative check:
Standard bioprocess texts list these three under physical methods, contrasting with covalent attachment and cross-linking (for example, CLEAs) under chemical methods.

Why Other Options Are Wrong:

• Each named method is indeed physical; selecting any would misclassify it.

Common Pitfalls:
Confusing cross-linking of adsorbed enzymes (a chemical stabilization step) with adsorption itself. The base immobilization mode here remains physical.

Final Answer:
None of these