Bacillus subtilis (Kosokin)

Bacillus subtilis (kosokin, 枯草菌) is a type of bacterium found widely in soil and on the surface of plants, and is characterized by secreting high levels of α-amylase. During koji making in sake production, when Bacillus subtilis multiplies on the surface of the koji, the result is a condition called suberi koji (also known as nururi koji, or "slippery" koji). This suberi koji plays an important role in efficiently saccharifying the starch in the rice. Bacillus subtilis is also known as a type of natto bacterium and is sometimes used in the production of fermented foods. However, if Bacillus subtilis multiplies too much, it can affect flavor and aroma, so careful management of koji making is important.