Koji-kin (Aspergillus oryzae) is grown on cooked grains (normally rice) or beans is Koji.
Koji-kin is a type of fungus and there are different types of Koji-kin: Aspergillus oryzae, Aspergillus soja, Aspergillus luchuensis, Aspergillus luchuensis mut. kawachii.
It is the key starter for many traditional Japanese fermented food, such as Miso, Soy source, Sake, Rice vinegar, and Mirin. Basically, without Koji, Japanese food culture is almost nothing.
The relationship between Koji and Japanese people are very very long. They appeared first time in written material back in the 8th century. However, Koji seemed to be used a long way back and Japanese people used to believe that “the changes” by Koji-kin was created by gods or spirits. It was mysterious and magical.
There are many sillier ferment food cultures exist in all over Asia, such as Tempeh (Indonesia) and Makgeolli (Korea). However, they use different types of fungi, which is called Rhuzipus. Modern food culture hasn’t got any boundaries anymore. Historically speaking, almost any fermented food by Koji-kin wasn’t anywhere but only in Japan.
Koji-kin has created more than 200 different types of amino acids, minerals, vitamins, enzymes etc. It has been discovered just only 100 types of enzymes inside. More to come!