Application of Immobilized Laccase on Polyurethane Foam for Ex-Situ Polycyclic Aromatic Hydrocarbons Bioremediation

摘要

There is growing concern about developing treatment technologies for the hazardous Polycyclic Aromatic Hydrocarbons (PAHs), because the rising levels of these compounds in the environment by human activities. The application of laccases has been evaluated as one of the most promising treatments. Thus, laccase immobilization on polyurethane foam (PUF)-low-cost material-was evaluated for bioremediation in batch mode of simulated groundwater using a combination of 16 polycyclic aromatic hydrocarbons as model pollutants. Conditions closer to a real contaminated site (non-optimal) were considered on our experimental design, leading to the formation of new degradation intermediaries, even more degraded than the usual ones. The bioremediation of PAH (mg L-1) using immobilized laccase on PUF reached 92.35% of removal for anthracene (Ant) and 97% for benzo(a)pyrene (BaP). After the treatment, the biodegradation products were identified as diisooctyl phthalate and tetradecane. The biodegradation mechanism was proposed, where PAHs oxidation processes and aromatic ring fission led to quinone and diethyl phthalate formation. Then, through the latter processes besides, polymerization and methylation, lead to the identified biodegradation product formation. The immobilized enzyme improvement in the removal yield of 8 of the other 14 PAHs tested in mu g L-1, compared to the free counterpart. Laccase immobilized on PUF achieved final anthracene concentration of 0.95 mg L-1, up to 38 mu g L-1 of chrysene (77% removal) and 98 mu g L-1 of pyrene (32% removal), under the intervention limits of environmental protection policies. Thus, laccase immobilized on PUF for use in bioreactors can be considered a potential approach for PAHs bioremediation for an ex-situ treatment.