Oyster mushroom is regarded as one of the commercially important edible mushrooms throughout the world. It consists of a number of different species including Pleurotus ostreatus, Pleurotus sajor-caju, Pleurotus cystidiosus, Pleurotus cornucopiae, Pleurotus pulmonarius, Pleurotus tuber-regium, Pleurotus citrinopileatus and Pleurotus flabellatus. They thrive on most of all hardwoods, wood by-products such as sawdust, paper, pulp sludge, all the cereal straws, corn and corn cobs, coffee residues such as coffee grounds, hulls, stalks, and leaves, banana fronds, and waste cotton often enclosed by plastic bags and bottles. The oyster mushroom is the second most important mushroom in production in the world, accounting for 25% of total world production of cultivated mushrooms. Oyster mushroom is grown worldwide, and China is the major producer. P. ostreatus was first cultivated in the USA in 1900 and several other species of the oyster mushroom such as Pleurotus sajor-caju were initially cultivated in India after the late of 1940s. The oyster mushroom has been regarded as one of the most profitable cash crops in Korea, accounting for 65% of total domestic mushroom production.