Effect of copper ion and soil humic acid on biodegradation of decabromodiphenyl ether (BDE-209) by Pseudomonas aeruginosa

A critical review on BDE-209: Source, distribution, influencing factors, toxicity, and degradation

As the most widely used polybrominated diphenyl ether, BDE-209 is commonly used in polymer-based commercial and household products. Due to its unique physicochemical properties, BDE-209 is ubiquitous in a variety of environmental compartments and can be exposed to organisms in various ways and cause toxic effects. The present review outlines the current state of knowledge on the occurrence of BDE-209 in the environment, influencing factors, toxicity, and degradation. BDE-209 has been detected in various environmental matrices including air, soil, water, and sediment. Additionally, environmental factors such as organic matter, total suspended particulate, hydrodynamic, wind, and temperature affecting BDE-209 are specifically discussed. Toxicity studies suggest BDE-209 may cause systemic toxic effects on living organisms, reproductive toxicity, embryo-fetal toxicity, genetic toxicity, endocrine toxicity, neurotoxicity, immunotoxicity, and developmental toxicity, or even be carcinogenic. BDE-209 has toxic effects on organisms mainly through epigenetic regulation and induction of oxidative stress. Evidence regarding the degradation of BDE-209, including biodegradation, photodegradation, Fenton degradation, zero-valent iron degradation, chemical oxidative degradation, and microwave radiation degradation is summarized. This review may contribute to assessing the environmental risks of BDE-209 to help develop rational management plans.

Interactions between Humic Substances and Microorganisms and Their Implications for Nature-like Bioremediation Technologies

The state of the art of the reported data on interactions between microorganisms and HSs is presented herein. The properties of HSs are discussed in terms of microbial utilization, degradation, and transformation. The data on biologically active individual compounds found in HSs are summarized. Bacteria of the phylum Proteobacteria and fungi of the phyla Basidiomycota and Ascomycota were found to be the main HS degraders, while Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes were found to be the predominant phyla in humic-reducing microorganisms (HRMs). Some promising aspects of interactions between microorganisms and HSs are discussed as a feasible basis for nature-like biotechnologies, including the production of enzymes capable of catalyzing the oxidative binding of organic pollutants to HSs, while electron shuttling through the utilization of HSs by HRMs as electron shuttles may be used for the enhancement of organic pollutant biodegradation or lowering bioavailability of some metals. Utilization of HSs by HRMs as terminal electron acceptors may suppress electron transfer to CO2, reducing the formation of CH4 in temporarily anoxic systems. The data reported so far are mostly related to the use of HSs as redox compounds. HSs are capable of altering the composition of the microbial community, and there are environmental conditions that determine the efficiency of HSs. To facilitate the development of HS-based technologies, complex studies addressing these factors are in demand.

Legacy Polybrominated Diphenyl Ethers (PBDEs) Trends in Top Predator Fish of the Laurentian Great Lakes (GL) from 1979 to 2016: Will Concentrations Continue to Decrease?

Polybrominated diphenyl ethers (PBDEs) were widely used as fire retardants and have been detected throughout the Great Lakes (GL) ecosystem. The concentration trends (after fish age normalization) of PBDEs in top predator fish (lake trout and walleye) of the GLs were determined from 1979 to 2016, which includes most of the period when PBDEs were manufactured and used in this region. The fish samples were collected by two national (U.S. and Canada) long-term monitoring and surveillance programs. Trends in total concentrations (age-normalized) of the five major PBDE congeners (BDE-47, 99, 100, 153, and 154) found in fish across all five lakes have varied over time. Significant increases were observed from 1990 to 2000 (16.3% per year). Rapidly decreasing concentrations (-19.5% per year) were found from 2000 to 2007. Since 2007, the decreasing trend has become smaller (less than -5.5% per year) and relatively unchanged from 2011 to 2015. BDE-47, the congener with the highest concentrations in lake trout, has decreased continuously (ranging from -6.7% to -16.2% per year) in all lakes except Lake Erie. This decrease can be associated with the voluntary and regulatory phase out of production and/or usage of PBDEs since 2000. However, it has been offset by recent (since 2007) increasing trends of the other four higher brominated BDE congeners, especially BDE-100 and 154. Production and usage of commercial penta- and octa- BDE mixtures containing primarily the five major PBDE congeners was discontinued in 2004 in the U.S.A. and 2008 in Canada. These results indicate increasing fish uptake and bioaccumulation of higher brominated BDE congeners may be related to the transformation of BDE-209 to lower brominated BDE compounds in the GL environment or food web. Considering the abundance of BDE-209 in existing products and sediment in GL region, the duration of the unchanging total PBDE concentration trend in GL fish could be longer than expected.

Biomineralization of 2'2'4'4'-Tetrabromodiphenyl ether in a Pseudomonas putida and Fe/Pd nanoparticles integrated system

Polybrominated diphenyl ethers (PBDEs) are widely used as flame retardants and challenges for water treatment due to their persistence and toxicity. In this study, the reduction of 2'2'4'4'-tetrabromodiphenyl ether (BDE-47) was investigated in a nano-bio-integrated system. Results showed that the introducing of P. putida could markedly accelerate the demineralization of BDE-47 in nZVI/Pd-P.p system; the continuous generation of acidic metaboliates by P. putida could decrease pH, which could alleviate the surface passivation to some extent, resulting in the releasing of Fe²⁺ and high generation of H₂O₂, the shift in reactive oxygen species from Fe(IV) to •OH. The BDE-47 was firstly debrominated to the DE by the highly reductive [Pd·2H] generated by nZVI/Pd, then oxidized to bromophenol and phenol, catechol as well as hydroquinone via the P. putida strain and the Fenton-like system. The toxicity assays confirmed the combined system could avert generation of nocuous intermediates, and could be an alternative strategy for complete remediation of recalcitrant POPs.

Effect of copper ion and soil humic acid on biodegradation of decabromodiphenyl ether (BDE-209) by Pseudomonas aeruginosa

Pseudomonas aeruginosa is a good environmental microorganism capable of degrading decabromodiphenyl ether (BDE‐209). This paper studied the effect of Cu²⁺ and humic acid (HA) extracted from e‐waste contaminated soils on biodegradation of BDE‐209 by P. aeruginosa. The adsorption isotherms of Cu²⁺ on HA, the crude enzyme activity, cell surface morphology, and biodegradation pathway were also investigated. The results showed that BDE‐209 biodegradation by P. aeruginosa was inhibited at Cu²⁺ concentrations above 5 mg L⁻¹, but exhibited the best effect at the condition of 40 mg L⁻¹ Cu²⁺ + 3 g L⁻¹ HA. At the condition of 40 mg L⁻¹ Cu²⁺ + 3 g L⁻¹ HA, 97.35 ± 2.33% of the initial BDE‐209 was degraded after 5 days, debromination efficiency was 72.14 ± 1.89%, crude enzyme activity reached the maximum of 0.519 ± 0.022U g⁻¹ protein, cell surface of P. aeruginosa was smooth with normal short‐rod shapes, and biodegradation pathway mainly include debromination, hydroxylation, and cleavage of the diphenyl ether bond. It was suggested that soil HA could eliminate the toxic effect of high Cu²⁺ concentrations and biodegradation of BDE‐209 was improved by synergistic effect of HA and Cu²⁺.