Industrial practice — Why are continuous cultures not widely used for many biotechnological products?

Introduction:
Continuous culture (chemostat or perfusion) offers steady-state operation and constant product quality in theory, yet many industrial fermentations remain batch or fed-batch. This question asks which limitation most credibly explains the limited industrial adoption across diverse products.

Given Data / Assumptions:

• Long campaigns increase exposure to contamination risk.
• Microbial evolution and mutation can occur over extended times.
• Regulatory frameworks exist for continuous bioprocessing, though implementation is case-specific.

Concept / Approach:
The principal practical barrier is operational risk: contamination or genetic drift during long continuous runs can collapse productivity or alter product quality. While some secondary metabolites are less amenable to chemostats, the statement that they are universally unsuitable is too strong. Likewise, regulators have approved continuous steps (e.g., perfusion cell culture) under quality systems, so a blanket ban is inaccurate.

Step-by-Step Solution:
Evaluate (a): Some secondary metabolite processes can be adapted (e.g., cell recycle, two-stage systems); not categorically impossible.Evaluate (c): Regulations do not prohibit continuous per se; compliance and control are required.Identify (b) as a widely recognized, overarching risk that constrains adoption.

Verification / Alternative check:
Industry case studies show strict asepsis and strain stability are critical; failures due to contamination/mutation cause costly downtime, explaining preference for finite-duration fed-batch campaigns.

Why Other Options Are Wrong:

• (a) Overgeneralization; some continuous processes make secondary products.
• (c) Factually incorrect; licensing is possible with proper control.
• (d) Not all statements are true, so “all of the above” is wrong.
• (e) Many organisms reach steady state; that is the basis of chemostats.

Common Pitfalls:
Assuming technical feasibility equals operational desirability; ignoring cell-line instability over long times at constant selective pressure.

Final Answer:
Contamination or mutation can have a disastrous effect on a long-running operation.