How many kinds of yeast are there? What is true yeast and what is false yeast?

Yeast is some unicellular fungi. Yeast is the earliest microorganism used in the history of human civilization, which can survive in anoxic environment. At present, there are more than 1000 kinds of yeast. According to the ability to produce spores (ascospores and basidiospores), yeast can be divided into three types: the strains that form spores belong to ascomycetes and basidiomycetes. Those fungi that do not form spores but propagate mainly through budding are called incomplete fungi, or "false yeast" (similar to yeast). At present, it is known that most yeasts are classified as Ascomycetes. Yeast is widely distributed in nature, mainly growing in acidic and humid sugary environment.