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Question #46576
The Question
In a sparged stirred-tank bioreactor, a high-density culture of recombinant aerobic bacteria is being cultivated for protein production. As the cell density reaches its peak, the yield of the desired recombinant protein drastically declines, accompanied by a rapid accumulation of acidic metabolites in the broth. Which of the following is the most scientifically accurate explanation for this observation?
Options
- A.
The dissolved oxygen demand of the culture exceeded the oxygen mass transfer capability of the bioreactor, forcing a metabolic shift towards anaerobic fermentation.
- B.
The flat-bladed impeller generated excessive shear forces, causing mechanical lysis of the bacterial cells and the subsequent release of acidic lysosomes.
- C.
The sparger facilitated excessive oxygen dissolution, leading to the generation of reactive oxygen species (ROS) that directly denatured the recombinant protein.
- D.
The continuous addition of sterile air through the sparger displaced dissolved carbon dioxide, which is strictly required as a terminal electron acceptor in aerobic bacteria.
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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|BOD (Biochemical Oxygen Demand) Logic|Activated Sludge Inoculum
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Understanding the physical limitations of bioreactor aeration (oxygen mass transfer rate) and its direct impact on microbial metabolic pathways.
Students often assume a sparger guarantees sufficient oxygen, failing to realize that high cell density creates an oxygen demand that outpaces the gas-to-liquid transfer rate.
Additionally, Option B tests a fundamental taxonomic concept (prokaryotes lack lysosomes) disguised within a complex biotechnology scenario.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Microbes in Human Welfare - Class 12 |
| Concept | BOD (Biochemical Oxygen Demand) Logic |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |