Aerobic bacteria (koki-sei kin)

Aerobic bacteria are a group of microorganisms that require oxygen, and they mainly include acetic acid bacteria and Bacillus subtilis (hay bacillus). These bacteria use oxygen to produce energy and multiply, so they are most active in environments where oxygen is present. In sake brewing, aerobic bacteria play an important role in parts of the fermentation process. Acetic acid bacteria in particular may help bring out flavors suited to rice and other raw materials. However, excessive activity by aerobic bacteria can affect the flavor of the sake, so proper management is important.