Physiological fluxes and antioxidative enzymes activities of immobilized Phanerochaete chrysosporium loaded with TiO2 nanoparticles after exposure to toxic pollutants in solution

Abstract

Immobilized Phanerochaete chrysosporium loaded with TiO2 nanoparticles (PTNs) are novel high-value bioremediation materials for adsorbing cadmium and for degrading 2,4-dichlorophenol (2,4-DCP). The real-time changes in H+ and O2 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 0.5mM Cd2+ (−351.25pmolcm−2s−1) than to 0.1mM Cd2+ (−107.47pmolcm−2s−1). The removal of Cd2+ by the PTNs increased more after treatment with the 0.5mM exposure solution (27.6mgg−1) than with the 0.1mM exposure solution (3.49mgg−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 6.5Ug−1 FW and 9.7Ug−1 FW, respectively, after exposure to 0.25mM Cd2+. The activity of superoxide dismutase (SOD) increased gradually in solutions containing 0.1–0.6mM Cd2+, and eventually reached a maximum (68.86Ug−1 FW). These results illustrate how the antioxidative defense system and the physiological fluxes of PTNs respond to the stress caused by toxic pollutants.