Physiological Response Mechanism Of Composite Nano-biomaterial Phanerochaete Chrysosporium In The Wastewater

Bioremediation using white-rot fungi has been largely employed for removing the toxic pollutants in wastewaters. As a model strain of white-rot fungi, Phanerochaete chrysosporium can tolerate cadmium and 2,4-DCP to some extent after the activation of antioxidant enzymes. However, some of the disadvantages include a longer incubation time for P. chrysosporium and limited resistance to pollutants. In this study, nitrogen-doped Ti O₂ nanoparticles were successfully loaded onto P. chrysosporium, and immobilized with sodium alga acid to enhance the degradation efficiency and resistance towards toxic pollutants in aqueous solutions.Until now, not much was known about the influence of cadmium and 2,4-DCP on PTNs. In order to study the response of PTNs to cadmium-polluted organic pollutants, we measured the instantaneous fluxes of H⁺, O₂, and Cd²⁺. The activities of three enzymes（SOD, CAT, and the NADH oxidase） were evaluated in an attempt to explore the antioxidant mechanisms of PTNs.The real-time changes in H⁺,O₂ and Cd²⁺ fluxes were measured using the noninvasive microtest technique（NMT）. The H⁺ influx increased after the addition of 2,4-DCP, and shifted to efflux following the addition of Cd²⁺. The O₂ flux decreased after the addition of both 2,4-DCP and Cd²⁺. A larger Cd²⁺ flux was immediately observed after exposure to 0.5 m M Cd²⁺（-351.25 pmol cm-2 s-1） than to 0.1 m M Cd²⁺（-107.47 pmol cm-2 s-1）. The removal of Cd²⁺ by the PTNs increased more after treatment with the 0.5 m M exposure solution（27.6 mg g-1） than with the 0.1 m M exposure solution（3.49 mg g-1）.The enzyme activities were analyzed to review the antioxidative defense system of PTNs in a solution containing various concentrations of Cd²⁺. The activities of the coenzyme nicotinamide adenine dinucleotide（NADH） oxidase as well as the enzyme catalase（CAT） plateaued at 6.5 U g-1 FW and 9.7 U g-1 FW, respectively, after exposure to 0.25 m M Cd²⁺. The activity of superoxide dismutase（SOD） increased gradually in solutions containing 0.1–0.6 m M Cd²⁺, and eventually reached a maximum（68.86 U g-1 FW）.Significant changes in the H⁺, O₂, and Cd²⁺ fluxes were the manifestations of an early cellular stress response to 2,4-DCP and Cd²⁺. PTNs exhibit resistance towards Cd²⁺ because of their antioxidant functions. The antioxidative enzymes SOD, CAT, and NADH oxidase protect PTNs from the oxidative damage induced by Cd²⁺ and 2,4-DCP. The resistance of PTNs to the toxic pollutants present in aqueous solutions is due to their efficient response to oxidative stress. However, the antioxidative defense system was damaged upon exposure to high concentration of toxic pollutants.