Milk is fermented or curdled by

Options

A. Rhizobium
B. Lactobacillus
C. Azotobacter
D. Clostridium

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which microorganism is responsible for fermenting or curdling milk.

2. **Identifying the Options**: The options provided are:
- Rhizobium
- Lactobacillus
- Azotobacter
- Clostridium

3. **Analyzing Each Option**:
- **Rhizobium**: This bacterium is known for forming nodules in leguminous plants and is involved in nitrogen fixation. It does not play a role in curdling milk.
- **Lactobacillus**: This is a gram-positive bacterium that is well-known for its role in the dairy industry. It ferments lactose (the sugar in milk) into lactic acid, which leads to the curdling of milk. This process is essential for making yogurt and cheese.
- **Azotobacter**: Similar to Rhizobium, Azotobacter is involved in nitrogen fixation in the soil and does not contribute to milk fermentation.
- **Clostridium**: This is another gram-positive bacterium, but it is associated with diseases like botulism and tetanus. It does not curdle milk.

4. **Conclusion**: Based on the analysis, the correct answer is **Lactobacillus**. It is the microorganism responsible for fermenting or curdling milk.

5. **Final Answer**: Milk is fermented or curdled by **Lactobacillus**.

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