Aspergillus Niger is a fungus and one of the most common species of the genus Aspergillus. It causes a disease called black mold on certain fruits and vegetables such as grapes, onions, and peanuts, and is a common contaminant of food. It is ubiquitous in soil and is commonly reported from indoor environments, where its black colonies can be confused with those of Stachybotrys (species of which have also been called "black mold").
Aspergillus Niger represents the most efficient, highest yielding bioprocess for the production of citric acid in practice. This process is a model for other filamentous fungal fermentation processes