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Characterization and mechanism of copper biosorption by a highly copper-resistant fungal strain isolated from copper-polluted acidic orchard soil
Citation:
Tu, C., Y. Liu, J. Wei, L. Li, K. Scheckel, AND Y. Luo. Characterization and mechanism of copper biosorption by a highly copper-resistant fungal strain isolated from copper-polluted acidic orchard soil. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH. Springer Berlin - Heidelberg, , Germany, 25(25):24965-24974, (2018).
Impact/Purpose:
As an essential trace element in organisms, copper (Cu) participates in the synthesis of various types of enzymes. However, excessive copper is highly toxic to organisms and inhibits cell growth, metabolism and other processes. Importantly, the application of a large amount of Bordeaux mixture and other copper-containing fungicides results in a substantial accumulation of copper in the orchard soil. In addition, the improper application of fertilizers and pesticides and the orchard soil acidification caused by long-term planting of fruit trees will further enhance the bioavailability of copper in the soil, which increases the risk for fruit trees to absorb the accumulated copper, which results in reduced fruit yield and quality, thus threatening food security. Therefore, it is urgent to develop a green sustainable remediation technique that is economical, efficient and environment-friendly for the acidified orchard soil contaminated with copper. Currently, among numerous remediation techniques, bioremediation has drawn wide attention due to its low cost, excellent performance, environmental friendliness and other advantages when compared with the traditional physical and chemical remediation techniques. Bioremediation includes techniques such as phytoremediation, microbial remediation, as well as their joint remediation. Microorganisms can not only degrade the organic pollutants in the environment, but also immobilize, mobilize or transform the heavy metals in the soil to change their environmental chemical behavior in the soil, thus achieving the purpose of bioremediation. In this study, a fungal strain NT-1, which was highly resistant to both soil acidification and copper contamination, was screened from an orchard soil with long-term apple cultivation and Bordeaux mixture application history, and this strain was characterized by physiological, biochemical and molecular biological techniques. The response characteristics of strain NT-1 to Cu(II) stress were investigated, and the factors affecting the Cu(II) adsorption by NT-1 were explored, with the mechanism of Cu(II) adsorption by NT-1 studied preliminarily. The aim of this paper was to provide a novel and effective fungal resource and key parameters influencing growth and copper removal by this fungus, which will be beneficial to the research and development of bioremediation technology and mechanism of copper polluted acidic orchard soils by indigenous fungus. In this paper, a copper-resistant fungal strain NT-1, which was isolated and preserved from copper-contaminated orchard soil, was identified as Gibberella sp. NT-1 based on the morphological, physiological, biochemical and molecular biological characteristics. The strain could grow in a wide range of relevant soil pH and Cu(II) concentrations; however, a high concentration of Cu(II) could inhibit the growth of NT-1, resulting in the decreases in biomass and colony diameter, the shrinkage and wrinkles on the fungal cell surface, and other physiological responses. It was found that temperature, pH, initial Cu(II) concentration, inoculum dose and other factors could substantially affect Cu(II) removal extent by NT-1. The Cu(II) adsorption by NT-1 followed a quasi-second-order kinetic equation and Langmuir isothermal adsorption model, and was a monolayer adsorption process dominated by surface adsorption. The binding of Cu(II) to NT-1 was mainly achieved by forming polydentate complexes with carboxylate and amide groups and forming Cu-nitrogen-containing heterocyclic complexes through Cu(II)-π interaction. In the future, key parameters and mechanisms obtained from this study will be adopted to guide the implementation soil microcosm experiment and field trial of fungal bioremediation of copper-contaminated acidic soil.
Description:
In this paper, a highly copper-resistant fungal strain NT-1 was characterized by morphological, physiological, biochemical, and molecular biological techniques. Physiological response to Cu(II) stress, effects of environmental factors on Cu(II) biosorption, as well as mechanisms of Cu(II) biosorption by strain NT-1 were also investigated in this study. The results showed that NT-1 belonged to the genus Gibberella, which exhibited high tolerance to both acidic conditions and Cu(II) contamination in the environment. High concentrations of copper stress inhibited the growth of NT-1 to various degrees, leading to the decreases in mycelial biomass and colony diameter, as well as changes in morphology. Under optimal conditions (initial copper concentration: 200 mg L−1, temperature 28 °C, pH 5.0, and inoculum dose 10%), the maximum copper removal percentage from solution through culture of strain NT-1 within 5 days reached up to 45.5%. The biosorption of Cu(II) by NT-1 conformed to quasi-second-order kinetics and Langmuir isothermal adsorption model and was confirmed to be a monolayer adsorption process dominated by surface adsorption. The binding of NT-1 to Cu(II) was mainly achieved by forming polydentate complexes with carboxylate and amide group through covalent interactions and forming Cu-nitrogen-containing heterocyclic complexes via Cu(II)-π interaction. The results of this study provide a new fungal resource and key parameters influencing growth and copper removal capacity of the strain for developing an effective bioremediation strategy for copper-contaminated acidic orchard soils.
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https://link.springer.com/article/10.1007%2Fs11356-018-2563-4