酵母 is read as こうぼ (koubo) and means yeast.
こうぼ
koubo
こうぼきん
yeast fungus
こうぼあえん
zinc yeast
こうぼえきす
yeast extract
しゅつがこうぼ
budding yeast (esp. Saccharomyces cerevisiae)
てつこうぼ
iron yeast
えいようこうぼ
nutritional yeast
あかがねこうぼ
copper yeast
ぱんこうぼ
baker's yeast (Saccharomyces cerevisiae)
きらーこうぼ
killer yeast
びーるこうぼ
brewer's yeast
こうそ
enzyme
おば
aunt