Isolation and characterization of a polycyclic aromatic hydrocarbons-degrading enzyme from Xylaria regalis

Twenty-one fungal species were screened for capability of removing pyrene and benzo(a)pyrene in culture. Xylaria regalis was found to show the highest activity. An PAHs-degrading enzyme was purified to homogeneity from the culture mycelium of X. regalis. The crude enzyme was subjected to a series of purification procedures, including QAE Sephadex A-25 anion exchange column, hydrophobic interaction phenyl 650M column and Fractogel HW-55 column chromatography, respectively. The enzyme was purified 70.5 fold, giving a 45% yield. The specific activity was 4690 U/mg. The molecular mass of the purified PAHsdegrading enzyme estimated by SDS-PAGE was approximately 29 kDa. The optimal pH of the purified enzyme was 8.5 and the enzyme was stable between pH 8.0–9.0. The optimal temperature of the enzyme was 30°C and it’s activity was still stable at higher temperatures. The enzyme was found stable within 2 h at 100°C and retained 60% of activity after 8 h incubation.