Biodegradation of chrysene and benzo[a]pyrene and removal of metals from naturally contaminated soil by isolated Trametes versicolor strain and laccase produced thereof

Abstract

The objective of this study was to assess the degradation rates of chrysene and benzo[a]pyrene, as well as the removal of aluminium and iron from contaminated soil collected in the upper layer (030 cm) in Lagos, Southwest Nigeria. Trametes versicolor was isolated from this soil and used in degradation experiments, with plantain peels as support. After 8 weeks, 82.0% of chrysene degradation was achieved by T. versicolor, and by adding support this increased to 91.0%. Benzo[a]pyrene was less degradable, with 38.0% and 49.1% of degradation, respectively. Trametes versicolor was also capable of accumulate 46.1% of aluminium and 57.2% of iron. By adding plantain peels, these amounts increased to 48.2% and 61.8%, respectively. At the same time, laccase was produced by Trametes versicolor on plantain peels, achieving 37.8 U/g of crude laccase during SSF at 30 °C for 3 weeks. Laccase degradation experiments were set up in packed-bed reactor (PBR), with a constant feed of 21.6 mL/day of laccase, with and without mediators. In 35 days, 75.9% degradation of chrysene was achieved by laccase. The highest degradation was observed with ABTS (2,2-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid diammonium salt) as mediator, 87.9%. Benzo[a]pyrene degradation with laccase reached 35.6%, raising to 38.8 % with ferulic acid as mediator. In addition, 99.2% of iron and 99.6% of aluminium was removed by laccase, being the treatment for this last mediated with ABTS.