Which of the following yields citric acid :

Options

A. Penicillium citricum
B. Aspergillus niger
C. Saccharomyces
D. Azospirilium

Answer

To determine which organism yields citric acid, we will analyze the options provided:

1. **Penicillium citricum**: This fungus is known for its ability to produce citric acid. It is often used in the fermentation process to produce citric acid, but it is not the most widely used organism for this purpose.

2. **Aspergillus niger**: This is a well-known fungus that is extensively used in the industrial production of citric acid. It is the most common organism used for commercial citric acid production due to its high yield and efficiency.

3. **Saccharomyces**: This genus includes yeast species, such as Saccharomyces cerevisiae, which are primarily used in baking and brewing. They do not produce citric acid in significant amounts.

4. **Ajo spirulum**: This is a type of blue-green algae (cyanobacteria) and is not known for citric acid production.

Based on the analysis of the options, the organism that yields citric acid most effectively is:

**Answer: Aspergillus niger**

### Step-by-Step Solution:
1. **Identify the organisms listed**: Look at the names provided in the question.
2. **Research the production capabilities**: Understand which organisms are known for producing citric acid.
3. **Evaluate each option**:
- Penicillium citricum: Produces citric acid but not as widely as others.
- Aspergillus niger: Known for high yield of citric acid; widely used in industry.
- Saccharomyces: Primarily used for fermentation in baking/brewing, not citric acid.
- Ajo spirulum: Not known for citric acid production.
4. **Select the best answer**: Based on the evaluation, Aspergillus niger is the correct answer.