Laccase-mediated degradation of petroleum hydrocarbons in historically contaminated soil.

Laccases (EC1.10.3.2) have attracted growing attention in bioremediation research due to their high reactivity and substrate versatility. In this study, three genes for potential novel laccases were identified in an enrichment culture from contaminated field soil and recombinantly expressed in E. coli. Two of them, designated as PlL and BaL, were biochemically characterized regarding their optimal pH and temperature, kinetic parameters, and substrate versatility. In addition, lacasse PlL from Parvibaculum lavamentivorans was tested on historically contaminated soil. Treatment with PlL led to a significantly higher reduction of total petroleum hydrocarbons (83% w/w) compared to the microbial control (74% w/w). Hereby, PlL was especially effective in degrading hydrocarbons > C17. Their residual concentration was by 43% w/w lower than in the microbial treatment. In comparison to the laccase from Myceliophthora thermophila (MtL), PlL treatment was not significantly different for the fraction > C17 but resulted in a 30% (w/w) lower residual concentration for hydrocarbons < C18. In general, PlL can promote the degradation of petroleum hydrocarbons. As a consequence, it can be applied to reduce remediation time by duly achieving remediation target concentrations needed for site closure.