This is a review paper, not an experimental study with new results. It compiled existing research on how citric acid is industrially produced using a fungus called Aspergillus niger — the microorganism responsible for most citric acid in cosmetics today. The review covers production methods, genetic engineering techniques, and applications across industries.

The authors reviewed and summarized published literature on citric acid production, fermentation techniques, genetic modification methods, and industrial applications. This is a literature review, not original research with new data.

Funding not disclosed in abstract