Complete degradation of anthracene by Manganese Peroxidase in organic solvent mixtures

Abstract

The goal of this study is the development of a system based on the use of the ligninolytic enzyme Manganese Peroxidase (MnP) for the degradation of polycyclic aromatic hydrocarbons (PAHs), of which anthracene was selected as an example. A main problem of these compounds is their poor solubility in aqueous media. Therefore, the addition of different water miscible organic solvents (acetone, methyl-ethyl-ketone, methanol and ethanol) was considered as a previous step to increase the bioavailability of anthracene. Due to the maximal solubilisation of anthracene and the minimum loss of MnP activity, acetone was selected as the optimal cosolvent, allowing to enhance 140-fold the anthracene solubility for an acetone concentration of 36% (v/v). The in vitro degradation of anthracene by MnP was investigated for different concentrations of the main cofactors and substrates that affect the catalytic cycle of MnP (Mn2+, H2O2 and organic acids) as well as for other environmental parameters (temperature, air/oxygen atmosphere and light source). The system attained a nearly complete degradation of anthracene, around 100%, after 6 h of operation under optimal conditions.