Applying β-cyclodextrin to amaranth inoculated with white-rot fungus for more efficient remediation of soil co-contaminated with Cd and BDE-209

Investigation of the effects of different substrates on the promotion of the soil microbial consortium, encompassing bacteria and fungi, in the bioremediation of decabromodiphenyl ether (BDE-209)

Decabromodiphenyl ether (BDE-209) is recognized as an emerging and hazardous pollutant in numerous ecosystems. Despite this, only a few studies have concurrently investigated the biodegradation of BDE-209 by a microbial consortium comprising both bacteria and fungi. Consequently, the interactions between bacterial and fungal populations and their mutual effects on BDE-209 degradation remain unclear. Our main objective was to concurrently assess the changes and activity of bacterial and fungal communities during the biodegradation of BDE-209 in a real soil matrix. In the present study, various organic substrates were employed to promote soil biomass for the biodegradation of BDE-209. Soil respiration and molecular analysis were utilized to monitor biological activity and biomass community structure, respectively. The findings revealed that the use of wheat straw in the soil matrix resulted in the highest soil respiration and microbial activity among the treatments. This approach obviously provided suitable habitats for the soil microflora, which led to a significant increase in the biodegradability of BDE-209 (49%). Biomass survival efforts and the metabolic pathway of lignin degradation through co-metabolism contributed to the biodegradation of BDE-209. Microbial community analysis identified Proteobacteria (Alphaproteobacteria-Betaproteobacteria), Firmicutes, Bacteroides (bacterial phyla), as well as Ascomycota and Basidiomycota (fungal phyla) as the key microorganisms in the biological community involved in the biodegradation of BDE-209. This study demonstrated that applying wheat straw can improve both the biological activity and the biodegradation of BDE-209 in the soil of polluted sites.

20 years of polybrominated diphenyl ethers on toxicity assessments

Polybrominated diphenyl ethers (PBDEs) serve as brominated flame retardants which continue to receive considerable attention because of their persistence, bioaccumulation, and potential toxicity. Although PBDEs have been restricted and phased out, large amounts of commercial products containing PBDEs are still in use and discarded annually. Consequently, PBDEs added to products can be released into our surrounding environments, particularly in aquatic systems, thus posing great risks to human health. Many studies and reviews have described the possible toxic effects of PBDEs, while few studies have comprehensively summarized and analyzed the global trends of their toxicity assessment. Therefore, this study utilizes bibliometrics to evaluate the worldwide scientific output of PBDE toxicity and analyze the hotspots and future trends of this field. Firstly, the basic information including the most contributing countries/institutions, journals, co-citations, influential authors, and keywords involved in PBDE toxicity assessment will be visualized. Subsequently, the potential toxicity of PBDE exposure to diverse systems, such as endocrine, reproductive, neural, and gastrointestinal tract systems, and related toxic mechanisms will be discussed. Finally, we conclude this review by outlining the current challenges and future perspectives in environmentally relevant PBDE exposure, potential carriers for PBDE transport, the fate of PBDEs in the environment and human bodies, advanced stem cell-derived organoid models for toxicity assessment, and promising omics technologies for obtaining toxic mechanisms. This review is expected to offer systematical insights into PBDE toxicity assessments and facilitate the development of PBDE-based research.

Low-Arsenic Accumulating Cabbage Possesses Higher Root Activities against Oxidative Stress of Arsenic

Cabbage grown in contaminated soils can accumulate high levels of arsenic (As) in the edible parts, posing serious health risks. The efficiency of As uptake varies drastically among cabbage cultivars, but the underlying mechanisms are not clear. We screened out low (HY, Hangyun 49) and high As accumulating cultivars (GD, Guangdongyizhihua) to comparatively study whether the As accumulation is associated with variations in root physiological properties. Root biomass and length, reactive oxygen species (ROS), protein content, root activity, and ultrastructure of root cells of cabbage under different levels of As stress (0 (control), 1, 5, or 15 mg L^-1) were measured As results, at low concentration (1 mg L^-1), compared to GD, HY reduced As uptake and ROS content, and increased shoot biomass. At a high concentration (15 mg L^-1), the thickened root cell wall and higher protein content in HY reduced arsenic damage to root cell structure and increased shoot biomass compared to GD. In conclusion, our results highlight that higher protein content, higher root activity, and thickened root cell walls result in lower As accumulation properties of HY compared to GD.

Fungal bioproducts for petroleum hydrocarbons and toxic metals remediation: recent advances and emerging technologies

Petroleum hydrocarbons and toxic metals are sources of environmental contamination and are harmful to all ecosystems. Fungi have metabolic and morphological plasticity that turn them into potential prototypes for technological development in biological remediation of these contaminants due to their ability to interact with a specific contaminant and/or produced metabolites. Although fungal bioinoculants producing enzymes, biosurfactants, polymers, pigments and organic acids have potential to be protagonists in mycoremediation of hydrocarbons and toxic metals, they can still be only adjuvants together with bacteria, microalgae, plants or animals in such processes. However, the sudden accelerated development of emerging technologies related to the use of potential fungal bioproducts such as bioinoculants, enzymes and biosurfactants in the remediation of these contaminants, has boosted fungal bioprocesses to achieve higher performance and possible real application. In this review, we explore scientific and technological advances in bioprocesses related to the production and/or application of these potential fungal bioproducts when used in remediation of hydrocarbons and toxic metals from an integral perspective of biotechnological process development. In turn, it sheds light to overcome existing technological limitations or enable new experimental designs in the remediation of these and other emerging contaminants.

Chemicals/materials of emerging concern in farmlands: sources, crop uptake and potential human health risks

Certain chemicals/materials that are contaminants of emerging concern (CECs) have been widely detected in water bodies and terrestrial systems worldwide while other CECs occur at undetectable concentrations. The primary sources of CECs in farmlands are agricultural inputs, such as wastewater, biosolids, sewage sludge, and agricultural mulching films. The percent increase in cropland area during 1950-2016 was 30 and the rise in land use for food crops during 1960-2018 was 100-500%, implying that there could be a significant CEC burden in farmlands in the future. In fact, the alarming concentrations (μg kg^-1) of certain CECs such as PBDEs, PAEs, and PFOS that occur in farmlands are 383, 35 400 and 483, respectively. Also, metal nanoparticles are reported even at the mg kg^-1 level. Chronic root accumulation followed by translocation of CECs into plants results in their detectable concentrations in the final plant produce. Thus, there is a continuous flow of CECs from farmlands to agricultural produce, causing a serious threat to the terrestrial food chain. Consequently, CECs find their way to the human body directly through CEC-laden plant produce or indirectly via the meat of grazing animals. Thus, human health could be at the most critical risk since several CECs have been shown to cause cancers, disruption of endocrine and cognitive systems, maternal-foetal transfer, neurotoxicity, and genotoxicity. Overall, this comprehensive review provides updated information on contamination of chemicals/materials of concern in farmlands globally, sources for their entry, uptake by crop plants, and their likely impact on the terrestrial food chain and human health.

Response of physiological characteristics of ecological restoration plants to substrate cement content under exogenous arbuscular mycorrhizal fungal inoculation

INTRODUCTION

In order to solve the inhibition of alkaline environment on plants growth at the initial stage of Eco-restoration of vegetation concrete technology, introducing AMF into vegetation concrete substrate is an effective solution.

METHODS

In this study, Glomus mosseae (GM), Glomus intraradices (GI) and a mixture of two AMF (MI) were used as exogenous inoculation agents. Festuca elata and Cassia glauca were selected as host plants to explore the relationship between the physiological characteristics of plants and the content of substrate cement under exogenous inoculation of AMF.

RESULTS

The experiment showed that, for festuca elata, the maximum mycorrhizal infection rates of inoculation with GM, MI were when the cement contents ranged 5-8% and that of GI inoculation was with the cement contents ranging 5-10%. Adversely, for Cassia glauca, substrate cement content had little effect on the root system with the exogenous inoculation of AMF. Compared with CK, the effects of AMF inoculation on the physiological characteristics of the two plants were different. When the cement content was the highest (10% and 8% respectively), AMF could significantly increase(p<0.05) the intercellular CO₂ concentration (Ci) of Festuca elata. Moreover, for both plants, single inoculation was more effective than mixed inoculation. When the cement content was relatively low, the physiological characteristics of Cassia glauca were promoted more obviously by the inoculation of GI. At higher cement content level, inoculation of GM had a better effect on the physiological characteristics of the two plants.

CONCLUSION

The results suggest that single inoculation of GM should be selected to promote the growth of Festuca elata and Cassia glauca in higher alkaline environment.

Role of plant growth-promoting rhizobacteria in boosting the phytoremediation of stressed soils: Opportunities, challenges, and prospects

Soil is considered as a vital natural resource equivalent to air and water which supports growth of the plants and provides habitats to microorganisms. Changes in soil properties, productivity, and, inevitably contamination/stress are the result of urbanisation, industrialization, and long-term use of synthetic fertiliser. Therefore, in the recent scenario, reclamation of contaminated/stressed soils has become a potential challenge. Several customized, such as, physical, chemical, and biological technologies have been deployed so far to restore contaminated land. Among them, microbial-assisted phytoremediation is considered as an economical and greener approach. In recent decades, soil microbes have successfully been used to improve plants' ability to tolerate biotic and abiotic stress and strengthen their phytoremediation capacity. Therefore, in this context, the current review work critically explored the microbial assisted phytoremediation mechanisms to restore different types of stressed soil. The role of plant growth-promoting rhizobacteria (PGPR) and their potential mechanisms that foster plants' growth and also enhance phytoremediation capacity are focussed. Finally, this review has emphasized on the application of advanced tools and techniques to effectively characterize potent soil microbial communities and their significance in boosting the phytoremediation process of stressed soils along with prospects for future research.

Current progress in degradation and removal methods of polybrominated diphenyl ethers from water and soil: A review

The widespread of polybrominated diphenyl ethers (PBDEs) in the environment has caused rising concerns, and it is an urgent endeavor to find a proper way for PBDEs remediation. Various techniques such as adsorption, hydrothermal and thermal treatment, photolysis, photocatalytic degradation, reductive debromination, advanced oxidation processes (AOPs) and biological degradation have been developed for PBDEs decontamination. A comprehensive review of different PBDEs remediation techniques is urgently needed. This work focused on the environmental source and occurrence of PBDEs, their removal and degradation methods from water and soil, and prospects for PBDEs remediation techniques. According to the up-to-date literature obtained from Web of Science, it could be concluded that (i) photocatalysis and photocatalytic degradation is the most widely reported method for PBDEs remediation, (ii) BDE-47 and BDE-209 are the most investigated PBDE congeners, (iii) considering the recalcitrance nature of PBDEs and more toxic intermediates could be generated because of incomplete degradation, the combination of different techniques is the most potential solution for PBDEs removal, (iv) further researches about the development of novel and effective PBDEs remediation techniques are still needed. This review provides the latest knowledge on PBDEs remediation techniques, as well as future research needs according to the up-to-date literature.

Response of Trametes hirsuta to hexavalent chromium promotes laccase-mediated decolorization of reactive black 5

The recalcitrant azo dyes combined with heavy metals constitute a major challenge for the bioremediation of industrial effluents. This study aimed to investigate the effect and mechanism of action of a white-rot fungus Trametes hirsuta TH315 on the simultaneous removal of hexavalent chromium [Cr(VI)] and azo dye (Reactive Black 5, RB5). Here, this study discovered that toxic Cr(VI) (1 mM) greatly promoted RB5 decolorization (from 57.15% to 83.65%) by white-rot fungus Trametes hirsuta with high Cr(VI)-reducing ability (>96%), resulting in the simultaneous removal of co-contaminants. On the basis of transcriptomic and biochemical analysis, our study revealed that the oxidative stress in co-contaminants mainly caused by Cr(VI), and a number of dehydrogenases and oxidases showed up-regulation in response to Cr(VI) stress. It was noteworthy that the oxidative stress caused by Cr(VI) in co-contaminants can both significantly induce glutathione S-transferase and laccase expression. Glutathione S-transferase potentially involved in antioxidation against Cr(VI) stress. Laccase was found to play a key role in RB5 decolorization by T. hirsuta. These results suggested that the simultaneous removal of co-contaminants by T. hirsuta could be achieved with Cr(VI) exposure. Overall, the elucidation of the molecular basis in details will help to advance the general knowledge about the fungus by facing harsh environments, and put forward a further possible application of fungi on environmental remediation.

Aqueous extracts from the selected hyperaccumulators used as soil additives significantly improve accumulation capacity of Solanum nigrum L. for Cd and Pb

The effects of soil treatment with aqueous extracts from three hyperaccumulators on Cd and Pb accumulation by Solanum nigrum L. were determined. The stem (S-RG) and leaf extracts (L-RG) of Rorippaglobosa (Turcz.) Thell., and stem extract (S-BP) of Bidens pilosa L. significantly enhanced Cd and Pb total accumulation capacity of S. nigrum compared to control (by 44 %, 47 %, and 29 % for Cd and by 28 %, 28 % and 21 % for Pb, respectively), while EDTA caused its 9 % and 15 % decrease due to the plant biomass reduction (by 33 %). The leaching experiments reflected affinity of additives to metal mobilization in soils. The concentrations of total organic acid in S-RG, L-RG and S-BP were the highest among studied extracts, which besides the beneficial effect on the soil environment (microbe number and enzyme activities), may be partial reasons of strong promotion of S. nigrum accumulation capacity for Cd and Pb. It was shown that hyperaccumulation properties of a plant are not a prerequisite of enhancing effect of the plant-based soil additive on the metal accumulation capacity of the target living hyperaccumultor. The plant-based chelators were found to be promising candidates for EDTA and other chemicals replacement in promoting efficient and environmentally safe phytoremediation.

AM fungi increase uptake of Cd and BDE-209 and activities of dismutase and catalase in amaranth (Amaranthus hypochondriacus L.) in two contaminants spiked soil

Soil co-contaminated with cadmium (Cd) and decabromodiphenyl ether (BDE-209) is a widespread environmental problem, especially in electronic waste contaminated surroundings. Accumulation of Cd and BDE-209 in crops has possibly harmful effects on local human health. In order to assess the potential of arbuscular mycorrhizal (AM) fungi and amaranth (Amaranthus hypochondriacus L.) in remediation of soil co-contaminated with Cd and BDE-209, pot trials were performed to investigate interactive effects of AM fungi, Cd and BDE-209 on growth of amaranth, uptake of Cd and BDE-209, distribution of chemical forms of Cd and activities of antioxidant enzymes in shoots and dissipation of BDE-209 in soil. The present results showed that shoot biomass of non-mycorrhizal plants was significantly inhibited by increasing of Cd addition (5-15 mg kg^-1), but were only slightly declined with BDE-209 addition (5 mg kg^-1). The interaction of Cd and BDE-209 reduced the proportions of ethanol- and d-H₂O-extractable Cd in shoots, consequently alleviated Cd toxicity to plants and enhanced root uptake of Cd and BDE-209. Inoculation of AM fungi resulted in significantly greater shoot biomass as well as higher concentrations of Cd and BDE-209 compared with non-mycorrhizal treatment. Moreover, AM fungi played a beneficial role in relieving oxidative stress on amaranth by increasing the activities of dismutase (SOD) and catalase (CAT) in shoots and significantly improved the dissipation of BDE-209 in soil. The present study suggested that combination of AM fungi and amaranth may be a potential option for remediation of Cd and BDE-209 co-contaminated soils.

Investigating the biodegradation of sulfadiazine in soil using Enterobacter cloacae T2 immobilized on bagasse

The application of the antibiotic sulfadiazine (SD) in veterinary medicine has created serious environmental issues due to its high mobility and non-degradability. A novel immobilized cell system has been developed and showed significant SD biodegradation potential in soil.

Cell changes and differential proteomic analysis during biodegradation of decabromodiphenyl ether (BDE-209) byPseudomonas aeruginosa

BDE-209 is a persistent organic pollutant. To promote microbial biodegradation of BDE-209 and gain further insight into its mechanism, cell changes and differential proteomic analysis ofP. aeruginosaduring biodegradation were studied.