Abstract
Microbial bioremediation is a promising technology to treat heavy metal-contaminated soils. However, the efficiency of filamentous fungi as bioremediation agents remains unknown, and the detoxification mechanism of heavy metals by filamentous fungi remains unclear. Therefore, in this study, we investigated the cell morphology and antioxidant systems of Penicillium chrysogenum XJ-1 in response to different cadmium (Cd) concentrations (0–10 mM) by using physico-chemical and biochemical methods. Cd in XJ-1 was mainly bound to the cell wall. The malondialdehyde level in XJ-1 cells was increased by 14.82–94.67 times with the increase in Cd concentration. The activities of superoxide dismutase, glutathione reductase (GR), and glucose-6-phosphate dehydrogenase (G6PDH) peaked at 1 mM Cd, whereas that of catalase peaked at 5 mM Cd. Cd exposure increased the glutathione/oxidized glutathione ratio and the activities of GR and G6PDH in XJ-1. These results suggested that the Cd detoxification mechanism of XJ-1 included biosorption, cellular sequestration, and antioxidant defense. The application of XJ-1 in Cd-polluted soils (5–50 mg kg-1) successfully reduced bioavailable Cd and increased the plant yield, indicating that this fungus was a promising candidate for in situ bioremediation of Cd-polluted soil.
Highlights
The toxicity of heavy metals to living organisms has attracted considerable attention because some toxic metals can transport and contaminate water and agricultural systems
We proposed the Cd detoxification mechanism of P. chrysogenum XJ-1 at the cellular level for the first time and provided a potential candidate bioremediation agent for Cdpolluted soil
Compared with the treatment of 1 mM Cd, the treatments of 5 and 10 mM Cd significantly increased the proportion of tightly bound Cd, but markedly decreased the fractionation of intracellular-bound Cd
Summary
The toxicity of heavy metals to living organisms has attracted considerable attention because some toxic metals can transport and contaminate water and agricultural systems. According to the reports by World Health Organization, cadmium (Cd) is a metal of immediate concern among all hazardous heavy metals (Zafar et al, 2007). It is necessary to develop remediation strategies for Cd-contaminated soil to protect public health and the environment (Deng et al, 2014). In situ immobilization of heavy metals by microbial remediation is more eco-friendly and economically efficient than conventional methods (Siripornadulsil and Siripornadulsil, 2013). This microbial remediation approach is a good alternative to inhibit the bioavailability of heavy metals to living organisms
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