Halotolerant laccases from Chaetomium sp., Xylogone sphaerospora, and Coprinopsis sp. isolated from a Mediterranean coastal area

Laccases (EC 1.10.3.2) are phenoloxidases involved in the transformation of the recalcitrant fraction of organic matter in soil. These enzymes are also able to transform certain aromatic pollutants such as polycyclic aromatic hydrocarbons (PAHs) and are known to be inhibited by chloride ions. This study aims to test the potential of some fungal strains newly isolated from natural environments subjected to high osmotic pressure such as coastal ecosystems, to produce chloride tolerant laccases. Three strains were identified as Chaetomium sp., Xylogone sphaerospora (two Ascomycota), and Coprinopsis sp. (a Basidiomycota) and the laccases produced by these fungi were weakly inhibited by chloride ions compared with previous data from literature. Moreover, we tested their reactivity towards various PAHs which are widespread anthropic pollutants. They were able to transform anthracene to 9,10-anthraquinone and we determine 7.5 eV as the threshold of ionization potential for PAH oxidation by these laccases.