Stirred-tank bioreactors have been designed for

Options

A. Availability of oxygen throughout the process
B. Ensuring anaerobic conditions in the culture vessel
C. Purification of product
D. Addition of preservatives to the product

Explanation

**Step-by-Step Solution:**

1. **Understanding Stirred-Tank Bioreactors**: Stirred-tank bioreactors are designed to cultivate microorganisms under controlled conditions. They are particularly effective for processes that require mixing and aeration.

2. **Identifying the Type of Microorganisms**: The question mentions that these bioreactors consist of microbes that grow in the absence of oxygen, which indicates that they are designed for anaerobic conditions.

3. **Analyzing the Options**:
- **Option 1**: Availability of oxygen throughout the process. This is incorrect because stirred-tank bioreactors for anaerobic microbes do not provide oxygen.
- **Option 2**: Ensuring anaerobic condition in the culture vessels. This is correct, as these bioreactors are specifically designed to maintain a lack of oxygen for anaerobic microorganisms to thrive.
- **Option 3**: Purification of products. This is not the primary function of the bioreactor; it is used for cultivation.
- **Option 4**: Addition of preservative to the products. This is also incorrect, as the bioreactor itself does not add preservatives.

4. **Conclusion**: The correct answer is the second option: ensuring anaerobic condition in the culture vessels.

**Final Answer**: Stirred-tank bioreactors have been designed for ensuring anaerobic condition in the culture vessels.

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