This question has been regraded.

Which 3-unit-operation sequence is NOT consistent with Figure 3.10 (Common Harvest and Clarification Schemes for Large Scale Mammalian Cell Culture Fermentation Processes)

Question

This question has been regraded.

Which 3-unit-operation sequence is NOT consistent with Figure 3.10 (Common Harvest and Clarification Schemes for Large Scale Mammalian Cell Culture Fermentation Processes)

BlackTom AI · Accepted Answer

Centrifugation is the primary coarse-solids removal step in large-scale mammalian cell culture clarification, followed by depth filtration for polishing and then membrane filtration for final particle and molecule separation.

Relevant concepts:
- Centrifugation: high-throughput, high-capacity removal of intact cells and large particulates by density separation; typically applied first to reduce solids load.
- Depth filtration: fibrous/porous media that traps residual particulates and colloids; used after coarse removal to polish the fluid.
- Membrane filtration (micro/ultra/normal flow): tight pore-size separation for final clarification, sterile filtration, or concentration; sensitive to high solids load.

Step-by-step reasoning:
1. Starting with cell broth containing high solids (cells, debris), the logical first step is centrifugation to remove the bulk of cells. This reduces particulate load by orders of magnitude.
2. The partially clarified supernatant then passes through depth filtration to capture remaining fine particulates, cell debris, and colloids. Depth filters act as a polishing stage and protect downstream membranes.
3. Finally, membrane filtration provides fine particle removal, sterile filtration, or concentration/diafiltration with minimal fouling risk because upstream steps have removed most solids.

Why Depth Filtration --> Centrifugation --> Membrane Filtration is inconsistent:
- Placing depth filtration before centrifugation would expose the depth filter to the highest solids concentration, causing rapid clogging, excessive pressure drop, and reduced throughput. Depth filters are not designed to handle the bulk solids load that centrifuges remove effectively.
- Running a centrifuge after a clogged or loaded depth filter is operationally inefficient and defeats the purpose of sequence design (coarse removal first, polishing second).
- Membrane filtration is best as a final, low-solids-stage operation; having it after centrifugation is fine, but only if centrifugation comes before depth filtration.

Why other typical sequences are correct:
- Centrifugation -> Depth Filtration -> Membrane Filtration aligns with the functional roles of each unit and is standard in Figure 3.10.
- Depth Filtration -> Membrane Filtration (without centrifuge) can be used for lower-solids feeds but not in the typical large-scale case.

Conclusion: therefore the sequence "Depth Filtration --> Centrifugation --> Membrane Filtration" is NOT consistent with Figure 3.10, matching the provided correct answer.

This question has been regraded. Which 3-unit-operation sequence is NOT consistent with Figure 3.10 (Common Harvest and Clarification Schemes for Large Scale Mammalian Cell Culture Fermentation Processes)单项选择题

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