3.Pleurotus ostreatus is in nature found in temperate zones of the Northern Hemisphere, such as Europe, North Africa, Asia and North America (Singer, 1986) because it forms fruit-bodies at relatively low temperature compared to other Pleurotus species. The macroscopic morphologic features of this wood-rotting fungus and the microscopic characteristics of the spores, basidia, cheilocystidia and pleurocystidia of the mushroom is summarized by OECD (2005). Figure 1 show P. ostreatus growing on a tree.