A UF/DF step before Protein A is most justified when:

Question

BlackTom AI · Accepted Answer

Low product titer (low mg/mL) or an unacceptable dynamic binding capacity (DBC) is the key reason to insert an ultrafiltration/diafiltration (UF/DF) step upstream of Protein A.

1) Relevant knowledge points and concepts
- UF/DF: concentrates product and performs buffer exchange, reducing feed volume and increasing target concentration.  
- Protein A capture: throughput is governed by column residence time, flow rate, and DBC (mass of product the resin binds per unit resin volume under dynamic conditions). DBC is a function of operating residence time and the feed concentration/ driving force for binding. Low feed concentration forces longer loading volumes and long cycle times to capture the same mass of product.

2) Step‑by‑step reasoning
- If titers are low, the harvest volume required to deliver a target mass of monoclonal antibody (mAb) is very large. Loading that large volume directly onto Protein A results in long load times and poor facility throughput.  
- Concentrating the feed via UF/DF reduces the load volume and increases the concentration delivered to the column, increasing the instantaneous mass loaded per unit time and improving effective utilization of DBC.  
- If measured DBC is unacceptable (i.e., the resin binds too little under current conditions), increasing feed concentration can raise the apparent DBC at a practical residence time and make the capture step viable.

3) Calculation example (intermediate steps)
- Example: harvest titer = 0.2 g/L, harvest volume = 100 L → total mAb = 0.2 g/L × 100 L = 20 g.  
- Protein A DBC (target) = 30 g/L resin → required resin = 20 g / (30 g/L) = 0.667 L resin.  
- However loading 100 L at a practical flow rate gives long load time. If UF concentrates feed to 5 g/L, new load volume = 20 g / 5 g/L = 4 L. Load time reduced by factor 25, improving throughput and DBC utilization.

4) Why the correct answer is correct
- UF/DF directly addresses low titers and poor DBC by increasing product concentration and reducing load volume, thereby improving column productivity and making Protein A capture feasible and efficient.

5) Why the other options are incorrect
- "Titers are high and DBC is excellent": no need for UF/DF before Protein A; it would be redundant.  
- "Elution is performed at neutral pH": this concerns downstream elution conditions after capture, not a reason to prefractionate the feed.  
- "When resin pressure–flow limitations prevent running the desired loading flow rate": UF/DF reduces volume but does not change resin pressure–flow characteristics; pressure limitations are addressed by column sizing/flow distribution, not UF/DF.

6) Conclusion
UF/DF before Protein A is most justified when titers are low and/or DBC is unacceptable — this matches the provided correct answer: "Titers are low and/or DBC is unacceptable."

A UF/DF step before Protein A is most justified when:Single choice

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A UF/DF step before Protein A is most justified when:Single choice

Similar Questions

A UF/DF step before Protein A. Which statement is NOT correct?

In an alternative placement described in Chapter 11.4, precipitation is introduced to replace polishing steps, but it has challenges. Which statement is NOT consistent with Chapter 11.4?

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As cell-culture titers increase, which statement is NOT consistent with the passage?

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More Practical Tools for Students Powered by AI Study Helper

Making Your Study Simpler

You run a gel after a purification experiment. This gel is shown above: The lane that most likely represents your completed purification is lane This lane would correlate with a in specific activity.