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Experimental and modeling studies of competitive Pb (II) and Cd (II) bioaccumulation by Aspergillus niger

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Abstract

Co-existence of toxic metals causes complex toxicity to microorganisms during bioremediation in water and soil. This study investigated the immobilization of Pb2+ and Cd2+ by fungus Aspergillus niger, which has been widely applied to environmental remediation. Five treatments were set, i.e., CK (no toxic metals), Pb2+ only, Cd2+ only, Pb2+/Cd2+ = 1:1(molar ratio), and Pb2+/Cd2+ = 2:1. Cadmium induced strong toxicity to the fungus, and maintained the high toxicity during incubation. However, as Pb/Cd ratio increased from 0 to 2, the removal rates of Cd2+ by A. niger were raised from 30 to 50%. The elevated activities of pyruvate dehydrogenase (PDH) and citrate synthetase (CS) enzymes confirmed that Pb addition could stimulate the growth of A. niger. For instance, citric acid concentrations and CS activities were 463.22 mg/L and 78.37 nmol/min/g, respectively, during 3-day incubation as Pb/Cd = 1. However, these two values were as low as ~ 50 with addition of only Cd. It was hence assumed that appropriate co-existence of Pb2+ enhanced microbial activity by promoting TCA cycle of the fungus. Moreover, the SEM analysis and geochemical modeling demonstrated that Pb2+ cations were more easily adsorbed and mineralized on A. niger with respect to Cd2+. Therefore, instead of intensifying metal toxicity, the addition of appropriate Pb actually weakened Cd toxicity to the fungus. This study sheds a bright future on application of A. niger to the remediation of polluted water with co-existence of Pb and Cd.

Key points:

• Cd2+ significantly inhibited P consumption, suggesting its high toxicity to A. niger.

• Pb2+ stimulated the growth of A. niger by promoting TCA cycle in the cells.

• Cd2+ removal by A. niger were improved with co-existence of Pb2+.

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Acknowledgements

We thank Dr. Juan Li and Dr. Jiani Chen at Nanjing University for the SEM and TEM assistance.

Funding

This work was supported by National Key R&D Program of China (2020YFC1808000).

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Contributions

Z.L. conceived and designed this study. J.Q. and X.S. carried out the experiments and analyzed the data. S.L., B.Z., and Y.C. contributed to the analysis of the biochemical analysis. L.Z. help to prepare the revisions to the manuscript. All the authors read and approved the manuscript.

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Correspondence to Zhen Li.

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This article does not contain any studies with human participants or animals performed by any of the authors.

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The authors declare no competing interests.

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Qiu, J., Song, X., Li, S. et al. Experimental and modeling studies of competitive Pb (II) and Cd (II) bioaccumulation by Aspergillus niger. Appl Microbiol Biotechnol 105, 6477–6488 (2021). https://doi.org/10.1007/s00253-021-11497-3

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  • DOI: https://doi.org/10.1007/s00253-021-11497-3

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