Koji, known scientifically as Aspergillus oryzae, is a type of mold used in the brewing of sake. Rather than having a direct role in the fermentation of sake, koji performs the role of the mash enzymes in the beer brewing process, converting the starch found in rice into sugar that can be fermented by sake yeasts
Technically, koji' describes the converted rice with the mold growing on it; the mold organism itself is known as koji-kin.
