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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 o C, 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.

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Electropolymerization processes and electrochemical properties of polypyrrole as electroactive polymer have been studied by cyclic voltammetric technique. Pyrrole was electropolymerized to form polypyrrole in water-based solvent containing sodium perchlorate as supporting electrolyte in several pH values. The pH of the solutions were varied by using Britton Robinson buffer. The results showed that oxidation potential limit of electropolymerization processes of pyrrole was 1220 mV vs Ag/AgCl reference electrode. It can be seen that cyclic voltammetric respon of polypyrrole membrane that was prepared by electropolymerization processes of pyrrole at the scanning rate of 100 mV/s was stable. While the processes of pyrrole electropolymerization carried out at the variation of pH showed that the best condition was at the pH range of 2 - 6.   Keywords: polypyrolle, electropolymer, voltammetric technique