Aspergillus,genus of fungi in the Fungi Imperfecti (form-class Deuteromycetes). Those species for which the sexual phase is known are placed in the order Eurotiales. A. order Eurotiales (phylum Ascomycota, kingdom Fungi) that exists as asexual forms (or anamorphs) and is pathogenic (disease-causing) in humans. Aspergillus niger causes black mold of foodstuffs; A. flavus, A. niger, and A. fumigatus cause aspergillosis in humans. A. oryzae is used to ferment sake, and A. wentii to process soybeans. Three other genera of the class Ascomycetes have Aspergillus-type conidia (asexually produced spores): Emericella, Eurotium, and Sartorya.