Stable Polyphenol Oxidase Produced by Pleurotus pulmonarius from Fermented Peach-Palm and Cocoa Wastes.

Pleurotus pulmonarius is an economically important edible mushroom well known for the production of several lignocellulolytic enzymes, including polyphenol oxidase (PPO), EC 1.14.18.1. This enzyme can oxidize and hydrolyze phenolic compounds directly associated with the organoleptic and nutritional properties of foods. Thus, the aim of this paper is to produce and characterize the PPO of P. pulmonarius 21 (CCB21). The fungus was able to produce PPO using peach-palm waste and cocoa bean shell as substrates under solid-state fermentation (SSF) in 5 days of cultivation at 90% humidity (3066 ± 232 U/gds). PPO was partially purified with 60% ammonium sulfate and showed a purification rate of 2.1 times and a yield of 53.92%. The enzyme showed an optimum temperature above 45 °C, an optimum pH in the range of 5.5 to 6.5, and proved quite stable, maintaining 86–88% of its activity for up to 120 min under these conditions. PPO had reduced activity in the presence of β-mercaptoethanol, while EDTA, SDS, Al3+, Cu4+, Li4+, and Mg2+ ions increased their activity. The enzyme presented a Vmax of 4166.65 U/min and a Km of 4.16 mM for pyrocatechol. The results obtained suggest that, due to its thermostability and little influence in the presence of ions and reagents tested, the PPO of P. pulmonarius CCB21 can be an alternative for application in different biotechnological and industrial processes. [ABSTRACT FROM AUTHOR]