Question

A recombinant protein is secreted extracellularly in soluble form by an E. coli culture. Which of the following downstream processes is/are involved in the purification of the extracellular secreted protein?

• A. Cell disruption
• B. Membrane ultrafiltration
• C. Solubilisation of inclusion bodies
• D. Liquid chromatography

Hint:

For proteins secreted into the extracellular space, ultrafiltration and liquid chromatography are commonly used to purify the protein from the culture medium.

Answer 1

The Correct Option is B, D

Step 1: Understand the downstream processes for recombinant protein purification.
When a recombinant protein is secreted extracellularly in soluble form, it is already present in the extracellular space and not trapped within the bacterial cells. Therefore, the purification process focuses on separating the protein from the culture medium.

Step 2: Analyze the options.
Cell disruption (A): Not necessary for extracellular proteins, as it is used to release intracellular proteins.
Membrane ultrafiltration (B): Used to concentrate and separate proteins from smaller molecules in the culture medium. Suitable for extracellular protein purification.
Solubilisation of inclusion bodies (C): Applicable only to insoluble intracellular proteins forming aggregates (inclusion bodies). Not needed for soluble, secreted proteins.
Liquid chromatography (D): Essential for fine purification, helping separate proteins based on size, charge, or affinity.

Step 3: Conclusion.
Since the recombinant protein is secreted in soluble form into the culture medium, the relevant downstream purification methods are membrane ultrafiltration and liquid chromatography.

Final Answer:
The correct answer is \( \boxed{(B), (D)} \).