Interfacial processes and mechanisms of synergistic degradation of dichlorobiphenyl by white rot fungi and magnetite nanoparticles

The rapid increase in the artificial syntheses of organic pollutants has raised widespread concern. However, the mechanisms by which fungi degrade these new organic pollutants in the environment and adapt to environmental stressors remain unclear. In this study, Phanerochaete chrysosporium, a model white rot fungus, was used to explore the interfacial processes and mechanisms for synergistic degradation of 4,4 & PRIME;-dichlorobiphenyl (PCB15) with magnetite nanoparticles. The results showed that after 3 and 5 days of cultivation with Phanerochaete chrysosporium alone, the rates for PCB15 degradation were 32% and 65%, respectively, indicating that the white rot fungus itself was able to degrade the organic pollutant. Moreover, the addition of magnetite nanoparticles significantly enhanced the degradation of PCB15 by Phanerochaete chrysosporium. After cocultivation for 3 and 5 days, the rates for PCB15 degradation increased to 42% and 84%, respectively. Synchrotron radiation-based Fourier transform infrared spectromicroscopy (SR-FTIR) showed that the magnetite particles were tightly adhered to the fungal hyphae and were unevenly distributed on the hyphal surfaces. Furthermore, cocultivation of the fungus and magnetite nanoparticles significantly enhanced the nanozymatic activity of magnetite. A linear regression model provided a significantly negative correlation (r=-0.96, p<0.001) between the nanozymatic activity of the magnetite and the concentration ratio of the PCB15, supporting the hypothesis that white rot fungi degraded the PCB15 by enhancing the nanozyme activity of magnetite. High-resolution X-ray photoelectron spectroscopy (XPS) revealed that the nanozymatic activity of magnetite was mainly governed by oxygen vacancies on the mineral surfaces rather than the iron valence. Together, these findings increase our understanding of the powerful capabilities of fungi in terms of stress resistance and adaptation to extreme environments and provide new insights into fungal-mediated degradation of organic pollutants for soil remediation in contaminated sites.