Step 1: Citric acid production overview:
- Citric acid finds extensive application in the food and pharmaceutical sectors. Its production is a crucial biotechnological process, typically facilitated by fungi under aerobic conditions.
- While various microorganisms can produce citric acid, Aspergillus niger, a fungus, is the most prevalent choice.
Step 2: Option analysis:
- Option (A) Aspergillus niger: This microorganism is the industry standard for citric acid production due to its high efficiency in fermentation.
- Option (B) Lactobacillus sp.: These bacteria are associated with lactic acid, not citric acid, production.
- Option (C) Clostridium butylicum: This bacterium produces butyric acid, not citric acid.
- Option (D) Saccharomyces cerevisiae: This yeast is primarily utilized for ethanol production, not citric acid.
Step 3: Conclusion:
The microorganism predominantly used for the commercial and industrial production of citric acid is Aspergillus niger. Therefore, option (A) is the correct selection.