Yaust or Yeast: How To spell?

The word Yaust is misspelled against Yeast, a noun meaning "A form of fungus which grows as indvidual rounded cells, rather than in a mycelium, and reproduces by budding; esp. members of the orders Endomycetales and Moniliales. Some fungi may grow both as a yeast or as a mycelium, depending on the conditions of growth."