Characterization of polyphenol oxidase application as phenol removal in extracts of rejected white oyster mushrooms (pleurotus ostreatus)

Abstract

Postharvest browning of edible mushrooms is related to oxidation of phenolic compounds by endogenous enzymes. Polyphenol oxidase (PPO) was isolated from rejected white oyster mushrooms (Pleurotus ostreatus) as a crude PPO extract using 50 mM of citrate buffer at pH 7 and 20 oC, which is active against phenol and catechol as substrates. PPO activity was 79.23 U/mL (0.3 mM phenol) and 49.14 U/mL (0.2 mM catechol) at initial rates measured using UV-Vis spectrophotometry. Protein content (using the Biuret method) in crude PPO extract was 3.15 mg/mL, and the specific activity of PPO was 25.15 U/mg (0.3 mM phenol) and 15.60 U/mg (0.2 mM catechol). PPO extract was effective in reducing phenol content by 10.63 to 12.07% for each 5 mL of crude PPO extract added to an artificial solution containing 10.00 mg/L of phenol. In addition, Fourier transform infrared spectra of pure and crude PPO were analyzed based on protein functional groups. We conclude that white oyster mushroom PPO extracts may have a potential for removal of phenolic compounds in bioremediation and in the food and drug industries.