Question

Which one of the following can NOT be a limiting substrate if Monod's growth kinetics is applicable?

• A. Extracellular carbon source
• B. Extracellular nitrogen source
• C. Dissolved oxygen
• D. Intracellular carbon source

Hint:

Monod's growth kinetics apply to scenarios where microbial growth is dependent on the concentration of external limiting substrates, not on internal reserves.

Answer 1

The Correct Option is D

Monod's growth kinetics describe microbial growth in relation to the concentration of a limiting substrate. The key assumption is that the rate of growth is dependent on the concentration of a substrate that is available in the external environment, not on internal stores of nutrients.

(1) Extracellular Carbon Source (Option 1):
- This can be a limiting substrate for microbial growth. For example, in a carbon-limited environment, the growth rate of the microorganism will be limited by the availability of the carbon source in the medium.

(2) Extracellular Nitrogen Source (Option 2):
- This is another potential limiting nutrient. Nitrogen is essential for the synthesis of amino acids and nucleotides, so its availability can limit microbial growth.

(3) Dissolved Oxygen (Option 3):
- Oxygen is crucial for aerobic organisms, and its availability can be limiting in some environments, especially in large-scale bioreactors or anaerobic conditions.

(4) Intracellular Carbon Source (Option 4):
- Intracellular carbon sources are internal stores within the cell and are not considered in Monod's growth kinetics. Monod's model focuses on external nutrients that influence the growth rate of microorganisms.

Conclusion: Intracellular carbon sources cannot be a limiting factor in Monod’s growth kinetics, as the model pertains to external, available substrates.