Question

Strains of Aspergillus niger are carefully selected for the positive characteristics of ------- yield.

• A. Fumaric acid
• B. Citric acid
• C. Itaconic acid
• D. Kojic acid

Hint:

Industrial citric acid fermentation is almost synonymous with Aspergillus niger.
Iron and trace metal restriction in the media is used to stimulate high citric acid accumulation by the fungus.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Microbial fermentation is used for the large-scale industrial synthesis of organic acids, utilizing highly productive fungal strains.

Step 2: Detailed Explanation:
1. Citric acid is produced on a large commercial scale via submerged or surface fermentation.
2. The filamentous fungus {Aspergillus niger is the primary organism used for this process.
3. Selected industrial strains of A. niger are highly efficient at converting simple sugars (such as sucrose or glucose from molasses) into citric acid, often achieving yields exceeding 70% of the carbon source.
4. While other fungi produce different acids (e.g., Rhizopus for fumaric acid), Aspergillus niger is the standard organism for citric acid production.

Step 3: Final Answer:
Strains of Aspergillus niger are industrially selected to produce high yields of Citric acid.