Killer yeast

Killer yeast is a type of yeast that can release a substance called killer toxin into its growth medium. This toxin kills other yeasts, which helps killer yeast keep its growing environment in its favor. Yeasts that are affected by killer yeast are called "sensitive yeasts," and they are vulnerable to killer toxin. Yeasts that are not affected by killer yeast and do not kill other yeasts themselves are called "neutral yeasts." In sake brewing, the balance among these yeasts plays an important role in flavor and fermentation characteristics.