Stirring ensures uniform distribution in fermentation

Steps:

• Fermentation for penicillin uses Penicillium mold, which requires aerobic conditions.
• Oxygen and nutrients must reach all cells for efficient growth and antibiotic production.
• Without stirring, settling occurs, limiting access to essentials.
• Stirring maintains suspension and circulation for optimal yield.

Why A is correct:

• In aerobic fermentation, stirring distributes dissolved oxygen and nutrients evenly, as per the principle of mass transfer in bioreactors, preventing nutrient gradients.

Why the others are wrong:

• B: Stirring prevents settling, not promotes it to the bottom.
• C: It avoids concentration at the top, ensuring even distribution.
• D: No chemical reaction with walls occurs; stirring addresses biological needs.

Final answer: A