Characterization of manganese-dependent peroxidase isoenzymes from the ligninolytic fungus Phanerochaete flavido-alba.

Phanerochaete flavido-alba is able to decolorize and detoxify olive oil wastewater (OMW) in a process in which simple and polymeric phenols are removed. An unusual acidic MnP is accumulated during the degradation course. This microorganism produces two families of MnPs. MnP1 has an apparent molecular weight of 45 kDa and is secreted as a mixture of isoenzymes with pI ranging from 5.6 to 4.75. MnP2, which is produced as an unique isoenzyme, has an apparent molecular weight of 55.6 Mr and an unusual acidic pI lower than 2.8. The higher specific peroxidase activity for purified MnP2 was for Mn2+ oxidation. Hydroquinone and methylhydroquinone oxidation by MnP2 was Mn2+ dependent, in reaction mixtures without exogenous H2O2. Conversely, ABTS oxidation was Mn2+ independent. Two different DNA fragments (mnpA and mnpB), amplified by PCR, using MnP2 N-terminal sequence and oligonucleotides deduced from two conserved sequences of other MnPs, code for MnPs that belong to the P. chrysosporium mnp2 subfamily on the basis of intron position. The structure of mnpA and mnpB seems to be related to known manganese peroxidase genes, but mnpA encodes an Alanine instead of a Serine (Ser168) regarded as invariant within typical MnPs.

Effect of olive oil mill wastewater on extracellular ligninolytic enzymes produced by Phanerochaete flavido-alba.

Our previous results have demonstrated that Phanerochaete flavido-alba decoloration, dephenolization and detoxification of olive oil mill wastewater (OMW) were associated with changes in the ligninolytic major exoenzymes accumulated in the cultures. This paper describes the effect of the two main OMW components (monomeric aromatic compounds and a major brownish polymeric pigment), on extracellular P. flavido-alba ligninolytic enzymes. Laccase was the sole ligninolytic enzyme detected in cultures containing monomeric aromatic compounds. Laccase and an acidic manganese-dependent peroxidase (MnPA, pI<2.8) were accumulated in cultures with OMW or polymeric pigment. Also, modified manganese-dependent peroxidases were observed mainly in OMW-supplemented cultures. Laccase was more stable to the effect of OMW toxic components and was accumulated in monomeric aromatic-supplemented cultures, suggesting a more important role than manganese-dependent peroxidases in OMW detoxification. Alternatively, MnPA accumulated in cultures containing the polymeric pigment seems to be more essential than laccase for degradation of this recalcitrant macromolecule by P. flavido-alba.