Obligate anaerobe (Hensei kenkisei kin)

Obligate anaerobes (hensei kenkisei kin) are a group of microorganisms that cannot grow in the presence of oxygen. These microbes avoid oxygen and are adapted to living in oxygen-free conditions. Well-known examples include butyric acid bacteria and acetone-butanol bacteria, which can play an important role in fermentation processes. In sake brewing, obligate anaerobes can also have a significant influence, although the activity of the yeast and lactic acid bacteria used in sake making is generally central. When suitable conditions are in place, obligate anaerobes become active and can be one factor in producing particular flavors and aromas.