Study on degradation of polycyclic aromatic hydrocarbons by crude enzymes from laccase-produced mushrooms

Key words: 
• mushroom /
• crude enzymes /
• polycyclic aromatic hydrocarbons /
• degradation

Abstract: Laccase is a polyphenol oxidase which could transform a wide range of persistent organic pollutants, including polycyclic aromatic hydrocarbons (PAHs). However, the high cost of pure laccase limited its utilization in environmental remediation. In our study, two crude enzymes were obtained from P. ostreatus and C. comatus by both submerged and solid-state fermentation, and the PAHs degradation and detoxification by crude enzymes by solid-state fermentation were also investigated. The results showed that no activity of lignin peroxidase and manganese peroxidase but only activity of laccase was detected in crude enzymes, moreover, laccase activity obtained by solid-state fermentation was higher than that by submerged, and it was stronger in crude enzymes of P. ostreatus than C. comatus. Both fungal crude enzymes by solid-state fermentation could degrade and detoxify PAHs, and the PAHs degradation and detoxification rate of crude enzymes from P. ostreatus, with lower laccase activity, was higher than that from C. comatus, probably due to more natural mediators was secreted by P. ostreatus. The degradation rate of anthracene, benzo［a］pyrene, benzo［a］ anthracene and acenaphthylene by solid-state fermentation crude enzymes from P. ostreatus were all higher than 50%. However, naphthalene, the most bio-available PAHs, was most recalcitrant for enzymatic oxidation, suggesting that the profile of PAHs degradation by laccase might relate to the ionization potentials (IPs).