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Question #45947
The Question
In industrial biotechnology, scaling up an aerobic microbial culture in a simple stirred-tank bioreactor often results in a premature shift from the exponential (log) phase to the stationary phase, despite an adequate supply of liquid nutrients. To counter this metabolic bottleneck, a sparged stirred-tank bioreactor is utilized. Which of the following best explains the biophysical constraint encountered during scale-up and the mechanism of its resolution?
Options
- A.
As bioreactor volume increases, the surface area-to-volume ratio decreases, limiting the Oxygen Transfer Rate (OTR); sparging introduces bubbles that significantly increase the interfacial surface area for oxygen dissolution.
- B.
As bioreactor volume increases, the surface area-to-volume ratio increases, causing rapid heat dissipation; sparging provides thermal insulation to maintain optimal microbial growth temperatures.
- C.
Large volumes induce excessive mechanical shear stress from the agitator, lysing cells; sparging completely replaces mechanical agitation to provide gentle, stress-free mixing.
- D.
Large volumes lead to the rapid accumulation of toxic liquid secondary metabolites; sparging acts as a continuous downstream processing mechanism to extract these metabolites.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Bioreactor Geometry|Absolute vs Relative Growth
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the NCERT line that 'sparged stirred-tank bioreactors have increased surface area for oxygen transfer' but fail to understand the underlying biophysical necessity: the mathematical drop in the surface area-to-volume ratio as absolute volume increases during scale-up.
This question tests the synthesis of geometric scaling laws with microbial metabolic phases.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Plant Growth and Development - Class 11 |
| Concept | Absolute vs Relative Growth |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |