What microorganism is yeast?

Yeast is widely distributed in nature, and there are many kinds, and there are hundreds of known ones. In fact, yeast is not a taxonomic term, but a unicellular fungus. It is difficult to define yeast accurately because of its complex species, diverse forms, great differences in metabolic characteristics and different phylogenetic status. However, it is generally believed that yeast has the following basic characteristics: individuals generally exist in a single cell state; Most of them reproduce by budding, and some divide or produce ascospores; Can ferment a variety of sugars; Cell walls often contain mannan; I like to grow in an environment with high sugar content and acidity.