Question

Which parameter is not commonly monitored in a bioreactor?

• A. Dissolved oxygen
• B. Carbon dioxide concentration
• C. Ambient light intensity
• D. Cell density

Hint:

• Common parameters monitored in bioreactors: Temperature, pH, Dissolved Oxygen (DO), agitation speed, aeration rate, substrate levels, product levels, cell density/biomass, off-gas composition (O\(_2\), CO\(_2\)).
• Light intensity is critical for photobioreactors but not for most other types of bioreactors.

Answer 1

The Correct Option is C

In bioreactors, several parameters are commonly monitored and controlled to optimize cell growth and product formation.

• (a) Dissolved oxygen (DO): Crucial for aerobic fermentations. Monitored using DO probes to ensure cells have sufficient oxygen.
• (b) Carbon dioxide concentration: Can be monitored in the off-gas (exit gas) as an indicator of metabolic activity and respiration rate. Sometimes dissolved CO\(_2\) is also monitored as high levels can be inhibitory.
• (d) Cell density: Monitored to track growth, often using optical density (turbidity), cell counting, or online biomass sensors.

Other commonly monitored parameters include temperature, pH, substrate concentration, product concentration, agitation speed, and gas flow rates. (c) Ambient light intensity:

• For most microbial fermentations (bacteria, yeast, fungi, animal cells) that are not photosynthetic, ambient light intensity is generally not a critical parameter to monitor or control, and bioreactors are often opaque or shielded from ambient light unless specific light-sensitive compounds are involved.
• For photobioreactors used to cultivate photosynthetic organisms (e.g., algae, cyanobacteria), light intensity (from an artificial source or sunlight) is a very critical parameter and is carefully monitored and controlled.

Since the question asks "not commonly monitored in a bioreactor" without specifying a photobioreactor, it implies general bioreactors for non-photosynthetic organisms. In that context, ambient light intensity is not a standard monitored parameter. \[ \boxed{\text{Ambient light intensity}} \]