A simple stirred tank bioreactor has all of the following properties, except

Options

A. It is usually cylindrical or with a curved base to facilitate the mixing of the reactor contents
B. The stirrer facilitates even mixing and oxygen availability throughout the bioreactor
C. Foam control system is present
D. Sterile air bubbles are sparged into the simple stirred tank bioreactor

Answer

To solve the question regarding the properties of a simple stirred tank bioreactor, we will analyze each of the options provided and determine which one does not belong to the characteristics of a simple stirred tank bioreactor.

### Step-by-Step Solution:

1. **Understanding the Bioreactor**:
- A bioreactor is a large vessel where biological processes occur, converting raw materials into products or enzymes. It provides optimal conditions for microbial growth and product formation.

2. **Identifying the Types of Bioreactors**:
- There are two main types of bioreactors:
- Simple stirred tank bioreactors
- Sparged stirred tank bioreactors

3. **Analyzing Each Option**:
- **Option A**: "It is usually cylindrical or with a curved base to facilitate the mixing of the reactor contents."
- This is true for a simple stirred tank bioreactor, as its design aids in effective mixing.

- **Option B**: "The stirrer facilitates even mixing and oxygen availability."
- This is also true, as the stirrer is essential for maintaining uniform conditions within the bioreactor.

- **Option C**: "Foam control system is present."
- A foam control system is often included in bioreactors to manage foam formation, which can be an issue during fermentation processes. This can be true for both types of bioreactors.

- **Option D**: "Sterile air bubbles are sparged into the simple stirred tank bioreactor."
- This statement is incorrect. Sterile air bubbles are characteristic of sparged stirred tank bioreactors, not simple stirred tank bioreactors.

4. **Conclusion**:
- The option that does not apply to a simple stirred tank bioreactor is **Option D**. Therefore, the answer is **D**.