Big holes in Swiss cheese are made by a

Options

A. a machine
B. a bacterium that produces methane gas
C. a bacterium producing a large amount of carbon dioxide
D. Pseudomonas

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks what causes the big holes in Swiss cheese. This indicates a need to explore the fermentation process involved in cheese production.

2. **Identifying the Options**: The options provided are:
- A machine
- A bacterium that produces methane gas
- A bacterium producing a large amount of carbon dioxide
- Pseudomonas

3. **Recognizing the Role of Microorganisms**: Swiss cheese is made from pasteurized milk that undergoes fermentation. During this process, specific bacteria are responsible for the production of gases.

4. **Identifying the Key Bacterium**: The bacterium responsible for the formation of holes in Swiss cheese is **Propionibacterium shermanii**. This bacterium ferments lactic acid and produces propionic acid and carbon dioxide.

5. **Understanding the Fermentation Process**: During the fermentation process, the lactic acid bacteria convert lactose in the milk to lactic acid. Propionibacterium shermanii then converts the lactic acid into propionic acid and carbon dioxide. The carbon dioxide gas forms bubbles, which create the characteristic holes in Swiss cheese.

6. **Conclusion**: Based on the fermentation process and the role of Propionibacterium shermanii, the correct answer to the question is that the big holes in Swiss cheese are made by a bacterium producing a large amount of carbon dioxide.

7. **Final Answer**: The correct option is **C: a bacterium producing a large amount of carbon dioxide**.

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