Aspergillus oryzae
Japanese: 麹菌（Aspergillus oryzae）
A filamentous fungus essential for brewing miso, soy sauce, and sake. It produces abundant enzymes that break down starches and proteins, and was designated Japan's national mold in 2006.
Koji mold quietly extends its hyphae over steamed rice or barley, building microscopic factories. These factories produce enzymes like amylase and protease—masters of decomposition that convert starches into sugars and proteins into amino acids.
Miso, soy sauce, and sake would not exist without koji's enzymes. It is the deepest foundation of Japan's fermentation culture.
Its scientific name is Aspergillus oryzae. Though it is a type of mold, it has been carefully selected over centuries as a safe organism that does not produce harmful aflatoxins.