Zymosan is a difficult-to-dissolve carbohydrate derived from the cell wall of yeast, and is especially used in the immunoassay of immune proteins. Zymosan Right! Zymosan is a difficult-to-dissolve carbohydrate derived from the cell wall of yeast, and is especially used in the immunoassay of immune proteins. Zymosan zymosan [5zaimEsAn] Zymosan