Oxygen management in cell culture: Excessively high dissolved oxygen (DO) levels in mammalian culture media are toxic. What downstream effects can occur?

Introduction / Context:
While oxygen is essential, too much dissolved oxygen can generate reactive oxygen species (ROS), leading to oxidative stress. Bioreactor control of DO is therefore critical to protect cells and product quality.

Given Data / Assumptions:

• We consider mammalian cells in agitated/aerated systems.
• High DO elevates ROS formation.
• Cells and media components are susceptible to oxidation.

Concept / Approach:
ROS attack nucleic acids (causing DNA damage), lipids (causing peroxidation), and proteins. Oxidation of media components and elevated respiration can also accelerate nutrient turnover, creating imbalances and additional stress.

Step-by-Step Solution:

Verification / Alternative check:
Guidelines recommend moderate DO setpoints (for example, 30–50% air saturation) and careful aeration/antifoam use, reflecting the risks listed.

Why Other Options Are Wrong:

Common Pitfalls:
Over-aeration when trying to avoid oxygen limitation; better to combine moderate DO with efficient mixing and appropriate feed strategies.

Final Answer:
All of the above.