Pleurotus ostreatus: A Biofactory for Lignin-Degrading Enzymes of Diverse Industrial Applications

Mushrooms have been used since centuries as food and medicine in many ancient cultures. This is based on their high content of carbohydrates, proteins, minerals, and many bioactive ingredients. Of different types of mushrooms, Pleurotus ostreatus is widely used and becomes nowadays the third important type in terms of worldwide production. P. ostreatus have been cultivated historically on tree logs, wood chops, and many other lignocellulosic biomass residues. This is based on the high capacity of mushroom to degrade complex organic lignin materials and convert them to utilizable carbohydrates. Therefore, this mushroom has been considered as high potential source for the production of lignin-degrading enzymes such as laccases, manganese peroxidases, veratryl alcohol oxidases, versatile peroxidases, heme-thiolate peroxidases, and many other biocatalysts. However, the production of these enzymes is regulated by different genes, and the enzyme yield is highly dependent on the type of substrate used, cultivation conditions, and addition of some minerals which act as enzyme cofactors. This chapter will provide up-to-date information about the enzyme system of P. ostreatus which is used for the degradation of lignocellulosic materials to support mushroom growth. Furthermore, these enzymes have a wide range of potential applications in different industries. Therefore, these types of enzymes can be used individually or in the form of enzyme cocktail in bleaching of pulp, removal of toxic phenolic compounds and toxic dyes from wastewater, biorefinery for biofuel production, and many other applications. In addition, as this type of mushroom is considered as Generally Regarded As Safe (GRAS) according to the Food and Drug Administration (FDA), thus, the produced enzyme has no limitations in terms of safety issues for application in food and feed industries.