Acceleration of nonylphenol and 4-tert-octylphenol degradation in sediment by Phragmites australis and associated rhizosphere bacteria

Structure–Biodegradability Relationship of Nonylphenol Isomers in Two Soils with Long-Term Reclaimed Water Irrigation

Nonylphenol (NP), as one of the typical endocrine disrupter chemicals (EDCs), has a high detection concentration and frequency in reclaimed water. This research focused on the degradation of NP isomers in two typical reclaimed water irrigation fields in Daxing, China, and Florida, USA. The results showed that the half-lives of NP isomer degradation in the soil of China and Florida were 2.03–8.66 d and 5.16–11.83 d, respectively. The degradation of NP isomers was structure-specific. Isomers of NP5, NP2, NP11, and NP3 had the highest degradation rates in the two soils; NP12, NP7, and NP6 were the isomers with medium degradation rates; and NP4, NP1, NP10, NP9, and NP8 had the slowest degradation rates. Steric hindrance and mean information index for the magnitude of distance (IDWbar) were found to be the better indexes for measuring the degradation of NP isomers compared with the length of the side chain, the type of the substitute, and the molecular connectivity. This study offers insights into the characteristics of NP isomers and two reliable indicators for measuring the degradation of NP isomers, which could provide data support for the environmental fate and the health risk assessment of NP in the future.

Manganese oxides in Phragmites rhizosphere accelerates ammonia oxidation in constructed wetlands

Phragmites reeds are widely used in constructed wetlands (CWs) for treating wastewater. The enrichment of microorganisms and Fe/Mn plaque in Phragmites rhizospheres largely contributes to pollutant removal. However, their interactions and potential synergistic roles in water purification are poorly understood. To address the issue, we first compared the microbial community traits in the Phragmites rhizosphere and adjacent bulk soil in six long-term operated CWs. Results showed that enriched microbes and functional genes in the Phragmites rhizosphere were largely involved in Mn oxidation, resulting in a two to three times enrichment of Mn oxides in the rhizosphere. In turn, the enriched Mn oxides played significant roles in driving microbial community composition and function. To further understand the biological manganese oxidation in the rhizosphere, we identified Mn-oxidizing bacteria using genome-centric analysis and found that 92% of identified Mn-oxidizing bacteria potentially participated in nitrogen cycling. We then conducted relationships between Mn-oxidizing genes and different nitrogen cycling genes and found Mn-oxidizing gene abundance was significantly correlated with ammonia oxidation gene amoA (R = 0.65). Remarkably, complete ammonia oxidation (comammox) Nitrospira, accounting for 39.11% of ammonia oxidizers, also positively correlated with Mn-oxidizing microbes. Based on the above observations, we inferred that the use of Mn oxides as a substrate in CWs may enhance ammonia oxidation. To apply this to actual engineering, we explored treatment performance in a pilot-scale Mn-amending CW. As expected, ammonia removal capacity improved by 23.34%, on average, in the Mn-amending CW. In addition, the abundance of amoA genes increased significantly in the Mn-amending CW, indicating improved biological processes rather than chemical reactions.

Stigmasterol root exudation arising from Pseudomonas inoculation of the duckweed rhizosphere enhances nitrogen removal from polluted waters

Rhizospheric microorganisms such as denitrifying bacteria are able to affect 'rhizobioaugmention' in aquatic plants and can help boost wastewater purification by benefiting plant growth, but little is known about their effects on the production of plant root exudates, and how such exudates may affect microorganismal nitrogen removal. Here, we assess the effects of the rhizospheric Pseudomonas inoculant strain RWX31 on the root exudate profile of the duckweed Spirodela polyrrhiza, using gas chromatography/mass spectrometry. Compared to untreated plants, inoculation with RWX31 specifically induced the exudation of two sterols, stigmasterol and β-sitosterol. An authentic standard assay revealed that stigmasterol significantly promoted nitrogen removal and biofilm formation by the denitrifying bacterial strain RWX31, whereas β-sitosterol had no effect. Assays for denitrifying enzyme activity were conducted to show that stigmasterol stimulated nitrogen removal by targeting nitrite reductase in bacteria. Enhanced N removal from water by stigmasterol, and a synergistic stimulatory effect with RWX31, was observed in open duckweed cultivation systems. We suggest that this is linked to a modulation of community composition of nirS- and nirK-type denitrifying bacteria in the rhizosphere, with a higher abundance of Bosea, Rhizobium, and Brucella, and a lower abundance of Rubrivivax. Our findings provide important new insights into the interaction of duckweed with the rhizospheric bacterial strain RWX31 and their involvement in the aquatic N cycle and offer a new path toward more effective bio-formulations for the purification of N-polluted waters.

Occurrence, potential ecological risks, and degradation of endocrine disrupter, nonylphenol, from the aqueous environment

Nonylphenol (NP) is considered a potential endocrine-disrupting chemical affecting humans and the environment. Due to widespread occurrence in the aquatic environment and neuro-, immuno, reproductive, and estrogenic effects, nonylphenol calls for considerable attention from the scientific community, researchers, government officials, and the public. It can persist in the environment, especially soil, for a long duration because of its high hydrophobic nature. Nonylphenol is incorporated into the water matrices via agricultural run-off, wastewater effluents, agricultural sources, and groundwater leakage from the soil. In this regard, assessment of the source, fate, toxic effect, and removal of nonylphenol seems a high-priority concern. Remediation of nonylphenol is possible through physicochemical and microbial methods. Microbial methods are widely used due to ecofriendly in nature. The microbial strains of the genera, Sphingomonas, Sphingobium, Pseudomonas, Pseudoxanthomonas, Thauera, Novosphingonium, Bacillus, Stenotrophomonas, Clostridium, Arthrobacter, Acidovorax, Maricurvus, Rhizobium, Corynebacterium, Rhodococcus, Burkholderia, Acinetobacter, Aspergillus, Pleurotus, Trametes, Clavariopsis, Candida, Phanerochaete, Bjerkandera, Mucor, Fusarium and Metarhizium have been reported for their potential role in the degradation of NP via its metabolic pathway. This study outlines the recent information on the occurrence, origin, and potential ecological and human-related risks of nonylphenol. The current development in the removal of nonylphenol from the environment using different methods is discussed. Despite the significant importance of nonylphenol and its effects on the environment, the number of studies in this area is limited. This review gives an in-depth understanding of NP occurrence, fate, toxicity, and remediation from the environments.

From Laboratory Tests to the Ecoremedial System: The Importance of Microorganisms in the Recovery of PPCPs-Disturbed Ecosystems

The presence of a wide variety of emerging pollutants in natural water resources is an important global water quality challenge. Pharmaceuticals and personal care products (PPCPs) are known as emerging contaminants, widely used by modern society. This objective ensures availability and sustainable management of water and sanitation for all, according to the 2030 Agenda. Wastewater treatment plants (WWTP) do not always mitigate the presence of these emerging contaminants in effluents discharged into the environment, although the removal efficiency of WWTP varies based on the techniques used. This main subject is framed within a broader environmental paradigm, such as the transition to a circular economy. The research and innovation within the WWTP will play a key role in improving the water resource management and its surrounding industrial and natural ecosystems. Even though bioremediation is a green technology, its integration into the bio-economy strategy, which improves the quality of the environment, is surprisingly rare if we compare to other corrective techniques (physical and chemical). This work carries out a bibliographic review, since the beginning of the 21st century, on the biological remediation of some PPCPs, focusing on organisms (or their by-products) used at the scale of laboratory or scale-up. PPCPs have been selected on the basics of their occurrence in water resources. The data reveal that, despite the advantages that are associated with bioremediation, it is not the first option in the case of the recovery of systems contaminated with PPCPs. The results also show that fungi and bacteria are the most frequently studied microorganisms, with the latter being more easily implanted in complex biotechnological systems (78% of bacterial manuscripts vs. 40% fungi). A total of 52 works has been published while using microalgae and only in 7% of them, these organisms were used on a large scale. Special emphasis is made on the advantages that are provided by biotechnological systems in series, as well as on the need for eco-toxicological control that is associated with any process of recovery of contaminated systems.

Biodegradation of the endocrine disrupter 4-t-octylphenol by the non-ligninolytic fungus Fusarium falciforme RRK20: Process optimization, estrogenicity assessment, metabolite identification and proposed pathways

4-t-octylphenol (4-t-OP), a well-known endocrine disrupting compound, is frequently found in various environmental compartments at levels that may cause adverse effects to the ecosystem and public health. To date, most of the studies that investigate microbial transformations of 4-t-OP have focused on the process mediated by bacteria, ligninolytic fungi, or microbial consortia. There is no report on the complete degradation mechanism of 4-t-OP by non-ligninolytic fungi. In this study, we conducted laboratory experiments to explore and characterize the non-ligninolytic fungal strain Fusarium falciforme RRK20 to degrade 4-t-OP. Using the response surface methodology, the initial biomass concentration and temperature were the factors identified to be more influential on the efficiency of the biodegradation process as compared with pH. Under the optimized conditions (i.e., 28 °C, pH 6.5 with an initial inoculum density of 0.6 g L^-1), 25 mg L^-1 4-t-OP served as sole carbon source was completely depleted within a 14-d incubation; addition of low dosage of glucose was shown to significantly accelerate 4-t-OP degradation. The yeast estrogenic screening assay further confirmed the loss of estrogenic activity during the biodegradation process, though a longer incubation period was required for complete removal of estrogenicity. Metabolites identified by LC-MS/MS revealed that strain RRK20 might degrade 4-t-OP as sole energy source via alkyl chain oxidation and aromatic ring hydroxylation pathways. Together, these results not only suggest the potential use of non-ligninolytic fungi like strain RRK20 in remediation of 4-t-OP contaminated environments but may also improve our understanding of the environmental fate of 4-t-OP.

Evaluation of the Rhizosphere Contribution to the Environmental Fate of the Herbicide Prometryn

Plant protection products (PPPs) undergo rigorous regulatory assessment to ensure that they do not pose unacceptable risks to the environment. Elucidation of their fate and behavior in soil is an integral part of this environmental risk assessment. The active substance degradation in soil of PPPs is first assessed in laboratory studies (typically following Organisation for Economic Co-operation and Development [OECD] test guideline 307). Conditions in guideline laboratory studies are far removed from those occurring under agricultural use, and the contribution of crop roots has currently not been assessed. We integrated viable plant root systems, representative of 3 different crop types, into the OECD test guideline 307 design to assess their impact on the dissipation of the herbicide prometryn. Significantly faster decline of parent residue and higher formation of nonextractable residues were observed in all 3 planted systems. This led to a reduction in the time required for 50% of the compound to dissipate (DT50) of approximately one-half in the presence of rye grass and hot pepper and of approximately one-third in the presence of red clover. These findings imply that plants and their associated root networks can have a significant influence on PPP dissipation. Based on these data, greater environmental realism could be added to the standardized laboratory study design by the inclusion of plant root systems into higher tier studies, which, in turn, could serve to improve the environmental risk assessment process. Environ Toxicol Chem 2020;39:450-457. © 2019 SETAC.

Environmental Water Pollution, Endocrine Interference and Ecotoxicity of 4-tert-Octylphenol: A Review

4-tert-Octylphenol is a degradation product of non-ionic surfactants alkylphenol polyethoxylates as well as raw material for a number of industrial applications. It is a multimedia compound having been detected in all environmental compartments such as indoor air and surface waters. The pollutant is biodegradable, but certain degradation products are more toxic than the parent compound. Newer removal techniques from environmental waters have been presented, but they still require development for large-scale applications. Wastewater treatment by plant enzymes such as peroxidases offers promise in total removal of 4-tert-octylphenol leaving less toxic degradation products. The pollutant's endocrine interference has been well reported but more in oestrogens than in any other signalling pathways through which it is believed to exert toxicity on human and wildlife. In this paper we carried out a review of the activities of this pollutant in environmental waters, endocrine interference and relevance to its toxicities and concluded that inadequate knowledge of its endocrine activities impedes understanding of its toxicity which may frustrate current efforts at ridding the compound from the environment.

Occurrence, fate and toxic effects of the industrial endocrine disrupter, nonylphenol, on plants - A review

Nonylphenol (NP) and its detrimental effects on the environment, humans, wildlife, fish and birds is an increasingly important global research focus. The number of investigations on the toxicity and metabolic fate of NP in plants is however limited. This paper reviews the prevalence and source of NP in plants and the effect it has on its morphological, physiological and ultrastructural status. Fruit and vegetables have been found to contain levels of NP that is twenty-fold exceeding the no observable effect level (NOEL) of freshwater algae. Apart from the potential risk this poses to the health of consumers, it can overburden the plant's natural defence system, leading to growth disorders. Plants exposed to NP show signs of overall growth reduction, changes in organelle structure and oxidative damage. These adverse effects may exacerbate the food security dilemma faced by many countries and impede their progress towards attaining the sustainable development goals.

"Duckweed-Microbe Co-Cultivation Method" for Isolating a Wide Variety of Microbes Including Taxonomically Novel Microbes

We herein described a new microbial isolation method using the interaction between the floating aquatic plant, duckweed, and microbes. We harvested microbial cells from Japanese loosestrife roots and co-cultivated these cells with aseptic duckweed using artificial inorganic medium for the plant for four weeks. During the co-cultivation, some duckweeds were collected every week, and the roots were used for microbial isolation using a low-nutrient plate medium. As a result, diverse microbial isolates, the compositions of which differed from those of the original source (Japanese loosestrife root), were obtained when the roots of duckweed were collected after 2 weeks of cultivation. We also successfully isolated a wide variety of novel microbes, including two strains within the rarely cultivated phylum, Armatimonadetes. The present study shows that a duckweed-microbe co-cultivation approach together with a conventional technique (direct isolation from a microbial source) effectively obtains more diverse microbes from a sole environmental sample.

Biotransformation of Sulfluramid (N-ethyl perfluorooctane sulfonamide) and dynamics of associated rhizospheric microbial community in microcosms of wetland plants

Although the use of Sulfluramid (N-ethyl perfluorooctane sulfonamide (N-EtFOSA)) has been restricted by the Stockholm Convention, it is still frequently detected in the environmental matrices and in use in some countries. Employing constructed wetlands as treatment systems requires understanding of the biodegradation process in the rhizosphere and the effect of contaminants on the microbes of wetlands. This study aimed to investigate the interactions between the microbial community and N-EtFOSA under aerobic and anaerobic conditions. Aerobic biotransformation of N-EtFOSA occurred with a half-life of 0.51 day and yielded 85.1 mol% PFOS of after 91 days. Kinetic modelling revealed that cleavage of the SN was the rate-limiting degradation step. Biotransformation was not observed under anaerobic and anoxic conditions, suggesting that N-EtFOSA is recalcitrant to biodegradation without dissolved oxygen. Under aerobic condition, the presence of N-EtFOSA and its biotransformation products decreased the microbial richness and diversity and exerted selective pressure on the microbial community. Enrichment of Methylocaldum was significant (49%) in the presence of N-EtFOSA compared to unexposed conditions (11%), suggesting that Methylocaldum is relatively tolerant to N-EtFOSA and potentially degrading N-EtFOSA. Under anaerobic conditions, the microbial richness and diversity were not significantly altered by the presence of N-EtFOSA. Only Methanomethylovorans increased significantly in the spiked microcosm (30% vs. 20%). These findings provide knowledge for comprehending the contribution of N-EtFOSA to other PFASs in various environmental conditions, information about microbial community changes in response to PFASs and robust microbial species which can degrade N-EtFOSA in the environment.

Migration and health risks of nonylphenol and bisphenol a in soil-winter wheat systems with long-term reclaimed water irrigation

Reclaimed water reuse has become an important means of alleviating agricultural water shortage worldwide. However, the presence of endocrine disrupters has roused up considerable attention. Barrel test in farmland was conducted to investigate the migration of nonylphenol (NP) and bisphenol A (BPA) in soil-winter wheat system simulating reclaimed water irrigation. Additionally, the health risks on humans were assessed based on US EPA risk assessment model. The migration of NP and BPA decreased from the soil to the winter wheat; the biological concentration factors (BCFs) of NP and BPA in roots, stems, leaves, and grains all decreased with their added concentrations in soils. The BCFs of NP and BPA in roots were greatest (0.60-5.80 and 0.063-1.45, respectively). The average BCFs of NP and BPA in winter wheat showed negative exponential relations to their concentrations in soil. The amounts of NP and BPA in soil-winter wheat system accounted for 8.99-28.24% and 2.35-4.95%, respectively, of the initial amounts added into the soils. The hazard quotient (HQ) for children and adults ranged between 10^-6 and 1, so carcinogenic risks could be induced by ingesting winter wheat grains under long-term reclaimed water irrigation.

Purification of eutrophic water containing chlorpyrifos by aquatic plants and its effects on planktonic bacteria

In this study, the removal of nutrients and chlorpyrifos as well as shifts of planktonic bacterial communities in constructed microcosms were investigated to evaluate the influence of Phragmites australis, Nymphaea alba, and Myriophyllum verticillatum, and their combination, on the restoration of eutrophic water containing chlorpyrifos. Plant-treated groups showed a higher pollutant removal rate than did no-remediation controls, indicating that treatment with plants is effective at remediation of eutrophic water containing chlorpyrifos. Different plants showed different performance on the remediation of eutrophic water, e.g., P. australis manifested stronger capacity for removal of sediment chlorpyrifos. This finding indicated that an appropriate plant combination is needed to deal with complex wastewater. During the treatments, the planktonic bacterial communities were influenced by the concentrations of nutrients and pollutants. The changes of composition of bacterial communities indicated a strong correlation between the bacterial communities and the concentrations of pollutants. The plants also influenced the planktonic bacterial communities, especially at the early phase of treatments. For example, P. australis increased the abundance of Limnohabitans and Nevskia significantly and decreased the abundance of Devosia, Luteolibacter, Methylibium, and Caulobacter significantly. The abundance of Hydrocarboniphaga significantly increased in N. alba-treated microcosms, whereas in M. verticillatum-treated microcosms, the abundance of Limnohabitans and Bdellovibrio significantly increased. Our results suggest that the planktonic bacterial communities may be altered during phytoremediation, and the functions of the affected bacteria should be concerned.

Enrichment, isolation, and biodegradation potential of long-branched chain alkylphenol degrading non-ligninolytic fungi from wastewater

4-t-Octylphenol (4-t-OP) has become a serious environmental concern due to the endocrine disruption in animals and humans. The biodegradation of 4-t-OP by pure cultures has been extensively investigated only in bacteria and wood-decaying fungi. In this study we isolated and identified 14 filamentous fungal strains from wastewater samples in Taiwan using 4-t-OP as a sole carbon and energy source. The isolates were identified based on sequences from different DNA regions. Of 14 fungal isolates, 10 strains grew effectively on solid medium with a wide variety of endocrine disrupting chemicals as the sole carbon and energy source. As revealed by high-performance liquid chromatography analysis, the most effective 4-t-OP degradation (>70%) in liquid medium was observed in Fusarium falciforme after 15days. To our knowledge, this is the first report on the degradation of 4-t-OP as a sole carbon and energy source by non-ligninolytic fungi.

Salinity and macrophyte drive the biogeography of the sedimentary bacterial communities in a brackish water tropical coastal lagoon

Brackish water coastal lagoons are least understood with respect to the seasonal and temporal variability in their sedimentary bacterial communities. These coastal lagoons are characterized by the steep environmental gradient and provide an excellent model system to decipher the biotic and abiotic factors that determine the bacterial community structure over time and space. Using Illumina sequencing of the 16S rRNA genes from a total of 100 bulk surface sediments, we investigated the sedimentary bacterial communities, their spatiotemporal distribution, and compared them with the rhizosphere sediment communities of a common reed; Phragmites karka and a native seagrass species; Halodule uninervis in Chilika Lagoon. Spatiotemporal patterns in bacterial communities were linked to specific biotic factors (e.g., presence and type of macrophyte) and abiotic factors (e.g., salinity) that drove the community composition. Comparative assessment of communities highlighted bacterial lineages that were responsible for segregating the sediment communities over distinct salinity regimes, seasons, locations, and presence and type of macrophytes. Several bacterial taxa were specific to one of these ecological factors suggesting that species-sorting processes drive specific biogeographical patterns in the bacterial populations. Modeling of proteobacterial lineages against salinity gradient revealed that α- and γ-Proteobacteria increased with salinity, whereas β-Proteobacteria displayed the opposite trend. The wide variety of biogeochemical functions performed by the rhizosphere microbiota of P. karka must be taken into consideration while formulating the management and conservation plan for this reed. Overall, this study provides a comprehensive understanding of the spatiotemporal dynamics and functionality of sedimentary bacterial communities and highlighted the role of biotic and abiotic factors in generating the biogeographical patterns in the bacterial communities of a tropical brackish water coastal lagoon.

Bisphenol A Removal by Submerged Macrophytes and the Contribution of Epiphytic Microorganisms to the Removal Process

Bisphenol A (BPA), a typical endocrine disruptor, has been found in global aquatic environments, causing great concern. The capabilities of five common submerged macrophytes to remove BPA from water and the contributions of epiphytic microorganisms were investigated. Macrophytes removed 62%-100% of total BPA (5 mg/L) over 12 days; much higher rates than that observed in the control (2%, F = 261.511, p = 0.000). Ceratophyllum demersum was the most efficient species. C. demersum samples from lakes with different water qualities showed no significant differences in BPA removal rates. Moreover, removal, inhibition or re-colonization of epiphytic microorganisms did not significantly change the BPA removal rates of C. demersum. Therefore, the contributions of epiphytic microorganisms to the BPA removal process were negligible. The rate of BPA accumulation in C. demersum was 0.1%, indicating that BPA was mainly biodegraded by the macrophyte. Hence, submerged macrophytes, rather than epiphytic microorganisms, substantially contribute to the biodegradation of BPA in water.

Biodegradation of the endocrine disrupter 4-tert-octylphenol by the yeast strain Candida rugopelliculosa RRKY5 via phenolic ring hydroxylation and alkyl chain oxidation pathways

4-(1,1,3,3-tetramethylbutane)-phenol (4-tert-OP) is one of the most prevalent endocrine disrupting pollutants. Information about bioremediation of 4-tert-OP remains limited, and no study has been reported on the mechanism of 4-tert-OP degradation by yeasts. The yeast Candida rugopelliculosa RRKY5 was proved to be able to utilize 4-methylphenol, bisphenol A, 4-ethylphenol, 4-tert-butylphenol, 4-tert-OP, 4-tert-nonylphenol, isooctane, and phenol under aerobic conditions. The optimum conditions for 4-tert-OP degradation were 30°C, pH 5.0, and an initial 4-tert-OP concentration of 30mgL^-1; the maximum biodegradation rate constant was 0.107d^-1, equivalent to a minimum half-life of 9.6d. Scanning electron microscopy revealed formation of arthroconidia when cells were grown in the presence of 4-tert-OP, whereas the cells remained in the budding form without 4-tert-OP. Identification of the 4-tert-OP degradation metabolites using liquid chromatography-hybrid mass spectrometry revealed three different mechanisms via both branched alkyl side chain and aromatic ring cleavage pathways.

Composting of 4-nonylphenol-contaminated river sediment with inocula of Phanerochaete chrysosporium

A composting study was performed to investigate the degradation of 4-nonylphenol (4-NP) in river sediment by inoculating Phanerochaete chrysosporium (Pc). Pc was inoculated into composting Reactor A, C and D, while Reactor B without inocula was used as control. The results showed that composting with Pc accelerated the degradation of 4-NP, increased the catalase and polyphenol oxidase enzyme activities in contaminated sediment. The dissipation half-life (t_1/2) of 4-NP in Reactor A, C and D with inocula of Pc were 2.079, 2.558, 2.424days, while in Reactor B without inocula of Pc it was 3.239days, respectively. Correlation analysis showed that the contents of 4-NP in sediment in Reactor A and D were negatively correlated with the actives of laccase, whereas no obvious correlation was observed in Reactor B and C. All these findings also indicated that Pc enhanced the maturity of compost, and the best composting C/N ratio was 25.46:1.

The nonylphenol biodegradation study by estuary sediment-derived fungus Penicillium simplicissimum

Nonylphenols (NPs) are persistent organic pollutants (POPs) with estrogenic properties that can perform endocrine-disrupting activities. By using high-concentration NP as environmental selection pressure, one NP biodegradation strain named NPF-4 was isolated and purified from estuary sediment of the Moshui River. It was identified as Penicillium simplicissimum (PS1) by appearance and 18S rDNA analysis. In different culture situations, the strain mass growth and biodegradation ability were evaluated. Within 4-n-nonylphenol (4-n-NP) initial concentration of 20 mg L(-1), it could be degraded 53.76, 90.08, and 100.00 % at 3, 7, and 14 days, respectively. In feeding experiments, it showed that NPF-4 could use 4-n-NP as a sole carbon source. Based on seven products/intermediates detected with GC and LC-MS, a novel biopathway for 4-n-NP biodegradation was proposed, in which sequential hydroxylation, oxidation, and decarboxylation at terminal β-C atom may occur for 4-n-NP detoxification, even complete mineralization in the end.

Fate and metabolism of the brominated flame retardant tetrabromobisphenol A (TBBPA) in rice cell suspension culture

Tetrabromobisphenol A (TBBPA) is the brominated flame retardant with the highest production volume and its bioaccumulation in environment has caused both human health and environmental concerns, however the fate and metabolism of TBBPA in plants is unknown. We studied the fate, metabolites, and transformation of (14)C-labeled TBBPA in rice cell suspension culture. During the incubation for 14 days, TBBPA degradation occurred continuously in the culture, accompanied by formation of one anisolic metabolite [2,6-dibromo-4-(2-(2-hydroxy)-propyl)-anisole] (DBHPA) (50% of the degraded TBBPA) and cellular debris-bound residues (46.4%) as well as mineralization (3.6%). The cells continuously accumulated TBBPA in the cytoplasm, while a small amount of DBHPA (2.1% of the initially applied TBBPA) was detectable inside the cells only at the end of incubation. The majority of the accumulated residues in the cells was attributed to the cellular debris-bound residues, accounting for 70-79% of the accumulation after the first incubation day. About 5.4% of the accumulation was associated with cell organelles, which contributed 7.5% to the cellular debris-bound residues. Based on the fate and metabolism of TBBPA in the rice cell suspension culture, a type II ipso-substitution pathway was proposed to describe the initial step for TBBPA degradation in the culture and balance the fate of TBBPA in the cells. To the best of our knowledge, our study provides for the first time the insights into the fate and metabolism of TBBPA in plants and points out the potential role of type II ipso-hydroxylation substitution in degradation of alkylphenols in plants. Further studies are required to reveal the mechanisms for the bound-residue formation (e.g., binding of residues to specific cell wall components), nature of the binding, and toxicological effects of the bound residues and DBHPA.

Aerobic degradation of estrogenic alkylphenols by yeasts isolated from a sewage treatment plant

Long-chain alkylphenols including octylphenol (OP) are well-known toxic pollutants prevailing in the environment due to the massive demand of these chemicals in industry and have been identified as endocrine disrupting chemicals (EDCs).

Degradation and toxicity reduction of the endocrine disruptors nonylphenol, 4-tert-octylphenol and 4-cumylphenol by the non-ligninolytic fungus Umbelopsis isabellina

Nonylphenol (NP), 4-tert-octylphenol (4-t-OP) and 4-cumylphenol (4-CP) are pollutants that are known as endocrine disruptors mainly due to their estrogen-mimicking activity. These phenolic substances are used in a wide range of industrial and commercial applications. In the present study, biodegradation of tNP, 4-t-OP and 4-CP using the non-ligninolytic fungus Umbelopsis isabellina was investigated. After 12h of incubation, more than 90% of initially applied tNP, 4-t-OP and 4-CP (25mgL(-1)) were eliminated. GC-MS analysis revealed several derivatives mainly (hydroxyalkyl)phenols. Moreover, xenobiotic biotransformation led to the formation of intermediates with less harmful effects than the parent compounds. For all xenobiotics, a decrease in growth medium toxicity was observed, using Artemia franciscana and Daphnia magna as bioindicators. The results indicate that U. isabellina has potential in the degradation and detoxification of contaminants with endocrine activity. Moreover, this is the first report demonstrating that a microorganism is capable of effective 4-CP elimination.

Application of Rice-Straw Biochar and Microorganisms in Nonylphenol Remediation: Adsorption-Biodegradation Coupling Relationship and Mechanism

Biochar adsorption presents a potential remediation method for the control of hydrophobic organic compounds (HOCs) pollution in the environment. It has been found that HOCs bound on biochar become less bioavailable, so speculations have been proposed that HOCs will persist for longer half-life periods in biochar-amended soil/sediment. To investigate how biochar application affects coupled adsorption-biodegradation, nonylphenol was selected as the target contaminant, and biochar derived from rice straw was applied as the adsorbent. The results showed that there was an optimal dosage of biochar in the presence of both adsorption and biodegradation for a given nonylphenol concentration, thus allowing the transformation of nonylphenol to be optimized. Approximately 47.6% of the nonylphenol was biodegraded in two days when 0.005 g biochar was added to 50 mg/L of nonylphenol, which was 125% higher than the relative quantity biodegraded without biochar, though the resistant desorption component of nonylphenol reached 87.1%. All adsorptive forms of nonylphenol (f_rap, f_slow, f_r) decreased gradually during the biodegradation experiment, and the resistant desorption fraction of nonylphenol (f_r) on biochar could also be biodegraded. It was concluded that an appropriate amount of biochar could stimulate biodegradation, not only illustrating that the dosage of biochar had an enormous influence on the half-life periods of HOCs but also alleviating concerns that enhanced HOCs binding by biochar may cause secondary pollution in biochar-modified environment.

Poly-3-hydroxybutyrate (PHB) production from alkylphenols, mono and poly-aromatic hydrocarbons using Bacillus sp. CYR1: A new strategy for wealth from waste

In the present study five different types of alkylphenols, each of the two different types of mono and poly-aromatic hydrocarbons were selected for degradation, and conversion into poly-3-hydroxybutyrate (PHB) using the Bacillus sp. CYR1. Strain CYR1 showed growth with various toxic organic compounds. Degradation pattern of all the organic compounds at 100 mg/l concentration with or without addition of tween-80 were analyzed using high pressure liquid chromatography (HPLC). Strain CYR1 showed good removal of compounds in the presence of tween-80 within 3 days, but it took 6 days without addition of tween-80. Strain CYR1 showed highest PHB production with phenol (51 ± 5%), naphthalene (42 ± 4%), 4-chlorophenol (32 ± 3%) and 4-nonylphenol (29 ± 3%). The functional groups, structure, and thermal properties of the produced PHB were analyzed. These results denoted that the strain Bacillus sp. CYR1 can be used for conversion of different toxic compounds persistent in wastewaters into useable biological polyesters.

Nonylphenol biodegradation, functional gene abundance and bacterial community in bioaugmented sediment: effect of external carbon source

Nonylphenol (NP) biodegradation in river sediment using Stenotrophomonas strain Y1 and Sphingobium strain Y2 were proved to be an effective strategy to remediate NP pollution in our earlier study. The purpose of this study is to investigate the influence of glucose addition on their ability to degrade NP in both liquid cultures and sediment microcosms. The shift in bacterial community structure and relative abundance of NP degraders in sediment microcosms were characterized using terminal restriction fragment length polymorphism analysis. The proportion of NP-degrading alkB and sMO genes was assessed using quantitative polymerase chain reaction (PCR) assay. The growth of Stenotrophomonas strain Y1 and its NP biodegradation efficiency were inhibited by glucose supplementation, while the relative abundance of alkB gene increased. However, NP degradation, as well as the growth of added degraders and proportion of sMO gene, was enhanced in the glucose-amended sediment microcosms inoculated with Sphingobium strain Y2. Moreover, external glucose addition altered bacterial community structures in bioaugmented sediment microcosms, depending on the level of glucose dosage.

Anaerobic biodegradation of nonylphenol in river sediment under nitrate- or sulfate-reducing conditions and associated bacterial community

Nonylphenol (NP) is a commonly detected pollutant in aquatic ecosystem and can be harmful to aquatic organisms. Anaerobic degradation is of great importance for the clean-up of NP in sediment. However, information on anaerobic NP biodegradation in the environment is still very limited. The present study investigated the shift in bacterial community structure associated with NP degradation in river sediment microcosms under nitrate- or sulfate-reducing conditions. Nearly 80% of NP (100 mg kg(-1)) could be removed under these two anaerobic conditions after 90 or 110 days' incubation. Illumina MiSeq sequencing analysis indicated that Proteobacteria, Firmicutes, Bacteroidetes and Chloroflexi became the dominant phylum groups with NP biodegradation. The proportion of Gammaproteobacteria, Deltaproteobacteria and Choloroflexi showed a marked increase in nitrate-reducing microcosm, while Gammaproteobacteria and Firmicutes in sulfate-reducing microcosm. Moreover, sediment bacterial diversity changed with NP biodegradation, which was dependent on type of electron acceptor.

Spirodela polyrhiza stimulates the growth of its endophytes but differentially increases their fenpropathrin-degradation capabilities

In situ remediation of organic contaminants via physical, chemical, and biological approaches is a practical technique for cleansing contaminated water and soil. In the present study, we showed that the three bacterial strains Pseudomonas sp. E1, Klebsiella terrigena E42, and Pseudomonas sp. E46, which can infect and colonize the aquatic plant Spirodela polyrhiza, utilize fenpropathrin as the sole carbon source for growth. S. polyrhiza helped enhance fenpropathrin degradation by E46 by 17.5%, only slightly improved fenpropathrin degradation by E42, and had no effect on strain E1. The application of plant exudates and extracts from fenpropathrin-unexposed/induced plants stimulated bacterial growth of the three strains, but resulted in differential fenpropathrin degradation, suggesting that not all plants and their endophytic bacteria are suitable for coupling phytoremediation and microbial-remediation. Moreover, addition of soil sediments to a microcosm not only stimulated the growth of strain E46 but also increased the rate of fenpropathrin degradation.

Variation of nonylphenol-degrading gene abundance and bacterial community structure in bioaugmented sediment microcosm

Nonylphenol (NP) can accumulate in river sediment. Bioaugmentation is an attractive option to dissipate heavy NP pollution in river sediment. In this study, two NP degraders were isolated from crude oil-polluted soil and river sediment. Microcosms were constructed to test their ability to degrade NP in river sediment. The shift in the proportion of NP-degrading genes and bacterial community structure in sediment microcosms were characterized using quantitative PCR assay and terminal restriction fragment length polymorphism analysis, respectively. Phylogenetic analysis indicated that the soil isolate belonged to genus Stenotrophomonas, while the sediment isolate was a Sphingobium species. Both of them could almost completely clean up a high level of NP in river sediment (150 mg/kg NP) in 10 or 14 days after inoculation. An increase in the proportion of alkB and sMO genes was observed in sediment microcosms inoculated with Stenotrophomonas strain Y1 and Sphingobium strain Y2, respectively. Moreover, bioaugmentation using Sphingobium strain Y2 could have a strong impact on sediment bacterial community structure, while inoculation of Stenotrophomonas strain Y1 illustrated a weak impact. This study can provide some new insights towards NP biodegradation and bioremediation.

Degradation and metabolism of tetrabromobisphenol A (TBBPA) in submerged soil and soil-plant systems

Contamination by tetrabromobisphenol A (TBBPA), the most widely used brominated flame retardant, is a matter of environmental concern. Here, we investigated the fate and metabolites of (14)C-TBBPA in a submerged soil with an anoxic-oxic interface and planted or not with rice (Oryza sativa) and reed (Phragmites australis) seedlings. In unplanted soil, TBBPA dissipation (half-life 20.8 days) was accompanied by mineralization (11.5% of initial TBBPA) and the substantial formation (60.8%) of bound residues. Twelve metabolites (10 in unplanted soil and 7 in planted soil) were formed via four interconnected pathways: oxidative skeletal cleavage, O-methylation, type II ipso-substitution, and reductive debromination. The presence of the seedlings strongly reduced (14)C-TBBPA mineralization and bound-residue formation and stimulated debromination and O-methylation. Considerable radioactivity accumulated in rice (21.3%) and reed (33.1%) seedlings, mainly on or in the roots. While TBBPA dissipation was hardly affected by the rice seedlings, it was strongly enhanced by the reed seedlings, greatly reducing the half-life (11.4 days) and increasing monomethyl TBBPA formation (11.3%). The impact of the interconnected aerobic and anaerobic transformation of TBBPA and wetland plants on the profile and dynamics of the metabolites should be considered in phytoremediation strategies and environmental risk assessments of TBBPA in submerged soils.

Analysis, toxicity, occurrence and biodegradation of nonylphenol isomers: a review

Over the last two decades, nonylphenols (NPs) have become to be known as a priority hazardous substance due primarily to its estrogenicity and ubiquitous occurrence in the environment. Nonylphenols are commonly treated as a single compound in the evaluation of their environmental occurrence, fate and transport, treatment or toxicity. However, technical nonylphenols (tNPs) are in fact a mixture of more than 100 isomers and congeners. Recent studies showed that some of these isomers behaved significantly differently in occurrence, estrogenicity and biodegradability. The most estrogenic isomer was about 2 to 4 times more active than tNP. Moreover, the half lives of the most recalcitrant isomers were about 3 to 4 times as long as those of readily-biodegradable isomers. Negligence of NP's isomer specificity may result in inaccurate assessment of its ecological and health effects. In this review, we summarized the recent publications on the analysis, occurrence, toxicity and biodegradation of NP at the isomer level and highlighted future research needs to improve our understanding of isomer-specificity of NP.

Nonylphenol biodegradation in river sediment and associated shifts in community structures of bacteria and ammonia-oxidizing microorganisms

Nonylphenol (NP) is one of commonly detected contaminants in the environment. Biological degradation is mainly responsible for remediation of NP-contaminated site. Knowledge about the structure of NP-degrading microbial community is still very limited. Microcosms were constructed to investigate the structure of microbial community in NP-contaminated river sediment and its change with NP biodegradation. A high level of NP was significantly dissipated in 6-9 days. Bacteria and ammonia-oxidizing archaea (AOA) were more responsive to NP amendment compared to ammonia-oxidizing bacteria (AOB). Gammaproteobacteria, Alphaproteobacteria and Bacteroidetes were the largest bacterial groups in NP-degrading sediment. Microorganisms from bacterial genera Brevundimonas, Flavobacterium, Lysobacter and Rhodobacter might be involved in NP degradation in river sediment. This study provides some new insights towards NP biodegradation and microbial ecology in NP-contaminated environment.

Impacts of Macondo oil from Deepwater Horizon spill on the growth response of the common reed Phragmites australis: a mesocosm study

We investigated impacts of Macondo MC252 oil from the Deepwater Horizon (DWH) spill on the common reed Phragmites australis (Cav.) Trin. ex Steud., a dominant species of the Mississippi River Delta. In greenhouse experiments, we simulated the most common DWH oiling scenarios by applying weathered and emulsified Macondo oil to aboveground shoots at varying degrees of coverage (0-100%) or directly to marsh soil at different dosages (0-16 Lm(-)(2)). P. australis exhibited strong resistance to negative impacts when oil was applied to shoots alone, while reductions in above- and belowground plant growth were apparent when oil was applied to the soil or with repeated shoot-oiling. Although soil-oiling compromised plant function, mortality of P. australis did not occur. Our results demonstrate that P. australis has a high tolerance to weathered and emulsified Macondo oil, and that mode of exposure (aboveground versus belowground) was a primary determinant of impact severity.

Effects of organochlorines on microbial diversity and community structure in Phragmites australis rhizosphere

This study investigated the impacts of an organochlorine (OC, γ-hexachlorocyclohexane and chlorobenzenes) mixture on microbial communities associated to Phragmites australis rhizosphere. Seventy-eight distinct colony morphotypes were isolated, cultivated and analysed by 16S rDNA sequence analysis. Toxicity tests confirmed sensitivity (e.g. Hevizibacter, Acidovorax) or tolerance (e.g. Bacillus, Aeromonas, Pseudomonas, Sphingomonas) of isolates. Rhizosphere analysis by pyrosequencing showed the microbial adaptation induced by OC exposure. Among the most abundant molecular operational taxonomic units, 80 % appeared to be tolerant (55 % opportunist, 25 % unaffected) and 20 % sensitive. P. australis rhizosphere exposed to OCs was dominated by phylotypes related to α-, β- and γ-Proteobacteria. Specific genera were identified which were previously described as chlorinated organic pollutant degraders: Sphingomonas sp., Pseudomonas sp., Devosia sp. and Sphingobium sp. P. australis could be suitable plants to maintain their rhizosphere active microbial population which can tolerate OCs and potentially improve the OC remediation process in part by biodegradation.