Zhengjun Zou

Responses of Phanerochaete chrysosporium to Toxic Pollutants: Physiological Flux, Oxidative Stress, and Detoxification

The white-rot fungus Phanerochaete chrysosporium has been widely used for the treatment of waste streams containing heavy metals and toxic organic pollutants. The development of fungal-based treatment technologies requires detailed knowledge of the relationship between bulk water quality and the physiological responses of fungi. A noninvasive microtest technique was used to quantify real-time changes in proton, oxygen, and cadmium ion fluxes following the exposure of P. chrysosporium to environmental toxic (2,4-dichlorophenol and cadmium). Significant changes in H(+) and O(2) flux occurred after exposure to 10 mg/L 2,4-dichlorophenol and 0.1 mM cadmium. Cd(2+) flux decreased with time. Reactive oxygen species formation and antioxidant levels increased after cadmium treatment. Superoxide dismutase activity correlated well with malondialdehyde levels (r(2) = 0.964) at low cadmium concentrations. However, this correlation diminished and malondialdehyde levels significantly increased at the highest cadmium concentration tested. Real-time microscale signatures of H(+), O(2), and Cd(2+) fluxes coupled with oxidative stress analysis can improve our understanding of the physiological responses of P. chrysosporium to toxic pollutants and provide useful information for the development of fungal-based technologies to improve the treatment of wastes cocontaminated with heavy metals and organic pollutants.

Removal of Cd(II), Cu(II) and Zn(II) from aqueous solutions by live Phanerochaete chrysosporium

Living Phanerochaete chrysosporium mycelia were used to remove heavy metals of Cd(II), Cu(II) and Zn(II) in auqeous solution. The uptake of heavy metal by the mycelia was dependent on the environmental conditions. The optimum biosorption conditions of Cd(II), Cu(II), and Zn(II) were pH 5.5–6.5 at 37°C, and 6 h. Under these conditions, the fungal biosorbent removed Cd(II), Cu(II), and Zn(II) rapidly and efficiently with maximum metal removal capacities of 59.77 mg/g, 74.78 mg/g, and 54.12 mg/g, respectively. The pseudo second-order kinetic model was superior to the pseudo first-order kinetic model, which indicated that the change of the surface sorption sites number was proportional to the square of the remaining unoccupied surface sites number. Fourier transform infrared (FT-IR) spectra indicated that hydroxyl and carboxyl groups were relevant to biosorption. Some crystal particles were found on the surface of the P. chrysosporium under scanning electron microscopy. Energy dispersive X-ray analysis and FT-IR revealed that amino acids and proteins were involved in binding metal ions. The results demonstrated that P. chrysosporium was a good potential biosorbent for adsorbing heavy metals.

Coarsening of extracellularly biosynthesized cadmium crystal particles induced by thioacetamide in solution

A novel coarsening route for extracellularly biosynthesized cadmium nanocrystals was investigated for the first time. In this process, the white rot fungus Coriolus versicolor was employed to take up cadmium ions and synthesize extracellular cadmium crystal particles. The coarsening of the particles was induced by thioacetamide under certain conditions. Scanning electron microscopy showed that the formed cadmium crystal particles were coarsened from about 100nm to 2-3μm. The corresponding energy-dispersive X-ray spectra confirmed the presence of proteins in the particles. The maximum removal efficiency of Cd(II) increased from 17% to 87%, and the corresponding sorption capacity of biomass increased from 4 to 24mgg(-1) with the completion of the coarsening process. The properties of the coarsened particles were also examined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD analysis of fungal mycelial pellets embedded with the coarsened particles confirmed the formation of cubic crystalline cadmium sulfide particles. The TEM results suggest that the coarsened particles were composed of clusters of several smaller particles. The changes in the functional groups on the biomass surface were studied through Fourier transform infrared spectroscopy. Based on the results above, a possible mechanism for the formation and coarsening of cadmium crystal particle is also discussed.