In vitro chrysene degradation by purified cell free laccase (P-CFL) from Cochliobolus lunatus strain CHR4D in the presence of various redox mediator systems (RMSs) and computational evaluation of their laccase-ligand interactions

An immense progression in global industrialization in recent years has astonishingly elevated the contamination of marine, coastal, aquatic and terrestrial habitats with pervasive pollutants such as polycyclic aromatic hydrocarbons. Despite being discovered early and exploited for the years, laccases — a copper oxidase has a wide spectrum of applications in the fields of toxicological studies, bioremediation and restoration of impacted ecological matrices. The present study focuses on purification of mid-redox potential laccase from marine-derived fungus C. lunatus strain CHR4D, which has very high capacity to degrade chrysene — a four ringed hydrocarbon. The purified laccase (66 kDa) was further used for the in vitro chrysene degradation in non-growth conditions, in the presence of various redox mediator systems (RMSs) containing ABTS, HBT and VA. RMS including ABTS was found the most effective, resulting in 53.30% chrysene degradation in 24 h, followed by HBT (30.99%) and VA (28.98%), when compared to control conditions (27.78%). Laccase-ligand interactions were further explained by computational simulations and docking protocols. It revealed that laccase exhibited the highest binding energy towards chrysene. It also showed hydrophobic interactions with HBT and VA. The study would be helpful to further establish role of laccase in in vitro degradation of HMW PAHs.