Efficacy of Trichoderma fungal species in the removal of α-naphthol from potato dextrose agar media

Alpha-naphthol is a two-ring aromatic hydrocarbon with toxic and mutagenic properties. Bioremediation technology is considered to be an efficient, economical, and environmentally friendly approach to the remediation of the sites contaminated with polycyclic aromatic hydrocarbons. In this study, six fungal species of the Trichoderma genus were cultured in potato dextrose agar (PDA) media containing 10-200 mg/kg of α-naphthol for the adaptation of the fungal strains. The removal of α-naphthol was assessed 30 days after the growth of the adapted fungal colonies at various concentrations of α-naphthol (50, 100, and 150 mg/kg). According to the obtained results, all the fungi could grow in the culture media containing α-naphthol, removing α-naphthol from the media. The highest removal efficiency belonged to T. viridescens, while the lowest removal efficiency belonged to T. koningii. In addition, the growth ability of the fungi was determined based on the colony diameters, and the results indicated the highest and lowest colony diameters in case of T. koningii and T. viridescens, respectively. In other words, an inverse correlation was observed between the fungal growth rate and α-naphthol removal efficiency. On the other hand, the results of enzyme activity assay demonstrated that the activity of peroxidase and catalase increased with higher α-naphthol contamination. The highest enzyme activity was observed in T. viridescens, growing in the media containing 150 mg/kg of α-naphthol, which indicated a marked correlation between α-naphthol removal efficiency and enzyme activity. Therefore, it could be concluded that T. viridescens had the highest enzyme activity and α-naphthol removal efficiency.