Which is not a bacterial action?

Options

A. Nitrogen fixation
B. Emulsification of fat
C. Sewage disposal
D. Ripening of cream.

Answer

To determine which option is not a bacterial action, we can analyze each option provided in the question step by step.

### Step-by-Step Solution:

1. **Identify the Options**: The options given are:
- A) Nitrogen fixation
- B) Emulsification of fat
- C) Sewage disposal
- D) Ripening of cream

2. **Analyze Option A: Nitrogen Fixation**:
- Nitrogen fixation is a process where certain bacteria, such as Rhizobium, convert atmospheric nitrogen into a form that plants can use. This is a well-known action of bacteria.
- **Conclusion**: This is a bacterial action.

3. **Analyze Option B: Emulsification of Fat**:
- Emulsification of fat refers to the process of breaking down fats into smaller droplets, which is primarily facilitated by enzymes like lipases. This process does not involve bacteria directly.
- **Conclusion**: This is NOT a bacterial action.

4. **Analyze Option C: Sewage Disposal**:
- In sewage disposal, bacteria play a crucial role in breaking down organic matter. Aerobic bacteria are commonly used in sewage treatment processes.
- **Conclusion**: This is a bacterial action.

5. **Analyze Option D: Ripening of Cream**:
- The ripening of cream involves the action of certain bacteria, such as Lactococcus, which help in the fermentation process and contribute to the flavor and texture of dairy products.
- **Conclusion**: This is a bacterial action.

6. **Final Conclusion**:
- After analyzing all the options, the only process that is not directly associated with bacterial action is **B) Emulsification of fat**.

### Answer:
The correct answer is **B) Emulsification of fat**.