Optimization of parameters for anaerobic co-metabolic degradation of TBBPA

Impacts of cefalexin on nitrite accumulation, antibiotic degradation, and microbial community structure in nitrification systems

The intensive use of various antibiotics for clinical and agricultural purposes has resulted in their widespread use in wastewater treatment plants. However, little research has been conducted on the effects of antibiotics on nitrite accumulation, antibiotic degradation pathways, or the microbial community structure in nitrification systems. In this study, a laboratory-scale sequencing batch reactor was used to treat wastewater containing cefalexin (CFX) at different doses (5, 10, 15, and 20 mg/L). The results showed that the nitrification performance was gradually inhibited with increasing CFX concentration. Ammonia-oxidizing bacteria (AOB) are more tolerant to CFX than nitrite-oxidizing bacteria (NOB). Under 15 mg/L of CFX, NOB were completely suppressed, whereas AOB were partially inhibited, as evidenced by an ammonium removal efficiency of 60 % and a 90 % of nitrite accumulation ratio. The partial nitritation was achieved. CFX can be degraded into 2-hydroxy-3phenylpyrazine and cyclohexane through bacterial co-metabolism, and CFX degradation gradually diminishes with decreasing nitrification performance. The abundance of Nitrospira gradually decreased with increasing CFX concentration. Ferruginibacter, Hydrogenophaga, Thauera, and Pseudoxanthomonas were detected at relative abundances of 13.2 %, 0.4 %, 0.9 %, and 1.3 %, respectively, indicating their potential roles in antibiotic degradation. These findings provide insight into the interactions between antibiotics and microbial communities, which are beneficial for a better understanding of antibiotic degradation in nitrification systems.

Characterization and low-temperature biodegradation mechanism of 17β-estradiol-degrading bacterial strain Rhodococcus sp. RCBS9

Steroidal estrogens residues in the environment can be a serious hazard to humans and animals and has been listed as group 1 carcinogens by World Health Organization (WHO). Microbial degradation is one of the effective strategies for the removal of such contaminants. In this study, a low-temperature degrading bacterial strain (Rhodococcus sp. RCBS9) was isolated from the soil of a dairy farm for 17β-estradiol (E2) degradation. The strain RCBS9 exhibited an efficient degradation potential at low temperatures. To lean how different factors influence E2 degradation, we have found a major role of intracellular enzymes in E2 degradation. Genomic and metabolomic analyses have suggested potential degradation genes and four metabolic pathways. These findings provide valuable strain resources for the low temperature bioremediation of E2 contamination and insights into E2 biodegradation mechanism.

Role of Gastrointestinal Microbiota from Crucian Carp in Microbial Transformation and Estrogenicity Modification of Novel Plastic Additives

Ingestion is a major exposure route for hydrophobic organic pollutants in fish, but the microbial transformation and estrogenic modification of the novel plastic additives by the gut microbiota of fish remain obscure. Using an in vitro approach, we provide evidence that structure-related transformation of various plastic additives by the gastric and intestinal (GI) microbiota from crucian carp, with the degradation ratio of bisphenols and triphenyl phosphate faster than those of brominated compounds. The degradation kinetics for these pollutants could be limited by oxygen and cometabolic substrates (i.e., glucose). The fish GI microbiota could utilize the vast majority of carbon sources in a Biolog EcoPlate, suggesting their high metabolic potential and ability to transform various organic compounds. Unique microorganisms associated with transformation of the plastic additives including genera of Citrobacter, Klebsiella, and some unclassified genera in Enterobacteriaceae were identified by combining high-throughput genetic analyses and metagenomic analyses. Through identification of anaerobic transformation products by high-resolution mass spectrometry, alkyl-cleavage was found the common transformation mechanism, and hydrolysis was the major pathway for ester-containing pollutants. After anaerobic incubation, the estrogenic activities of triphenyl phosphate and bisphenols A, F, and AF declined, whereas that of bisphenol AP increased.

Characterization and Degradation Pathways of Microbacterium resistens MZT7, A Novel 17β-Estradiol-Degrading Bacterium

Due to the ecotoxicity of 17β-estradiol (E2), residual E2 in the environment poses potential risks to human and animal health and ecosystems. Biodegradation is considered one of the most effective strategies to remove E2 from the environment. Here, a novel, efficient E2-degrading bacterial strain Microbacterium resistens MZT7 was isolated from activated sludge and characterized. The genome of strain MZT7 contained 4,011,347 bp nucleotides with 71.26% G + C content and 3785 coding genes. There was 86.7% transformation efficiency of 10 mg/L E2 by strain MZT7 after incubation for 5 d at optimal temperature (30 °C) and pH (7.0). This strain was highly tolerant to ranges in pH (5.0-11.0), temperature (20-40 °C), and salinity (2-8%). Adding sources of carbon (glucose, maltose, sucrose, or lactose) or nitrogen sources (urea, peptone, or beef extract) promoted the degradation of E2 by strain MZT7. However, when yeast extract was added as a nitrogen source, the degradation efficiency of E2 was inhibited. Metabolites were analyzed by LC-MS and three metabolic pathways of E2 degradation were proposed. Further, the intermediates dehydroepiandrosterone and androsta-1,4-diene-3,17-dione were detected, as well as identification of kshB and fadD3 genes by KEGG, confirming one E2 degradation pathway. This study provided some insights into E2 biodegradation.

Efficient biodegradation of tetrabromobisphenol A by the novel strain Enterobacter sp. T2 with good environmental adaptation: Kinetics, pathways and genomic characteristics

T2, a gram-positive bacterium capable of rapidly degrading tetrabromobisphenol A (TBBPA), and affiliated with the genus Enterobacter, was isolated for the first time from sludge that had been contaminated for several years. The TBBPA degradation data fitted the first-order model well. Under optimal conditions (pH of 7, temperature of 31 °C, TBBPA concentration of 5 mg L^-1, and inoculum size of 5%), 99.4% of the initially added TBBPA was degraded after 48 h. TBBPA degradation fitted the first-order model with the half-life of 3.3 h. These results illustrated that the TBBPA degradation capability of strain T2 was significantly better than that of previously reported bacteria. A total of 17 intermediates were detected, among which five were reported for the first time. Whole-genome sequencing revealed that strain T2 had a chromosome with the total length of 4 854 376 bp and a plasmid with the total length of 21 444 bp. It harbored essential genes responsible for debromination, such as cyp450, gstB, gstA, and HADH, and genes responsible for subsequent complete mineralization, such as bioC, yrrM, Tam, and Ubil. A key protein of haloacid dehalogenases responsible for the biodegradation of TBBPA may also be involved in the regulation of TBBPA degradation in natural environment. In soil bioremediation experiments, strain T2 showed excellent environmental adaptation. It was able to biodegrade TBBPA and its typical intermediate bisphenol A efficiently. Therefore, it could potentially be applied to treat TBBPA-contaminated sites.

Review of the environmental occurrence, analytical techniques, degradation and toxicity of TBBPA and its derivatives

BFRs (brominated flame retardants) are a class of compounds that are added to or applied to polymeric materials to avoid or reduce the spread of fire. Tetrabromobisphenol A (TBBPA) is one of the known BFR used many in industries today. Due to its wide application as an additive flame retardant in commodities, TBBPA has become a common indoor contaminant. Recent researches have raised concerns about the possible hazardous effect of exposure to TBBPA and its derivatives in humans and wildlife. This review gives a thorough assessment of the literature on TBBPA and its derivatives, as well as environmental levels and human exposure. Several analytical techniques/methods have been developed for sensitive and accurate analysis of TBBPA and its derivatives in different compartments. These chemicals have been detected in practically every environmental compartment globally, making them a ubiquitous pollutant. TBBPA may be subject to adsorption, biological degradation or photolysis, photolysis after being released into the environment. Treatment of TBBPA-containing waste, as well as manufacturing and usage regulations, can limit the release of these chemicals to the environment and the health hazards associated with its exposure. Several methods have been successfully employed for the treatment of TBBPA including but not limited to adsorption, ozonation, oxidation and anaerobic degradation. Previous studies have shown that TBBPA and its derivative cause a lot of toxic effects. Diet and dust ingestion and have been identified as the main routes of TBBPA exposure in the general population, according to human exposure studies. Toddlers are more vulnerable than adults to be exposed to indoor dust through inadvertent ingestion. Furthermore, TBBP-A exposure can occur during pregnancy and through breast milk. This review will go a long way in closing up the knowledge gap on the silent and over ignored deadly effects of TBBPA and its derivatives and their attendant consequences.

Tetrabromobisphenol A (TBBPA) anaerobic biodegradation occurs during acidogenesis

This is the first study to bring evidence on the anaerobic biodegradation of TBBPA occurring during acidogenesis in domestic sewage at environmentally relevant concentrations by complex microbial communities. This was accomplished by continuously operating two anaerobic structured bed reactors (ASTBR) for over 100 days under acidogenic (Acidogenic Reactor, AR) and multistep methanogenic (Methanogenic Reactor, MR) conditions. In the AR, the temporal carbohydrates consumption and the acetic acid production were strongly correlated with TBBPA removal by the Pearson's test. The spatial concentration of TBBPA and carbohydrates along the MR and the kinetic degradation profiles corroborate the AR results. It is hypothesized that TBBPA biodegradation in the studied conditions occurs during acidogenesis via the cometabolism supported by non-specific enzymes and the metabolism (dehalorespiration) established by electrons donors such as H₂, which are both produced during the macrocomponents breakdown in the early stages of the anaerobic digestion. The TBBPA mass balance showed that approximately 86.8 ± 0.05% and 97 ± 0.01% of the removed TBBPA was biodegraded in the AR and MR, respectively. Furthermore, TBBPA biodegradation went further than reductive debromination as total phenols were detected in the reactors' effluent.

Insights into the Occurrence, Fate, and Impacts of Halogenated Flame Retardants in Municipal Wastewater Treatment Plants

Halogenated flame retardants (HFRs) have been extensively used in various consumer products and many are classified as persistent organic pollutants due to their resistance to degradation, bioaccumulation potential and toxicity. HFRs have been widely detected in the municipal wastewater and wastewater treatment solids in wastewater treatment plants (WWTPs), the discharge and agricultural application of which represent a primary source of environmental HFRs contamination. This review seeks to provide a current overview on the occurrence, fate, and impacts of HFRs in WWTPs around the globe. We first summarize studies recording the occurrence of representative HFRs in wastewater and wastewater treatment solids, revealing temporal and geographical trends in HFRs distribution. Then, the efficiency and mechanism of HFRs removal by biosorption, which is known to be the primary process for HFRs removal from wastewater, during biological wastewater treatment processes, are discussed. Transformation of HFRs via abiotic and biotic processes in laboratory tests and full-scale WWTPs is reviewed with particular emphasis on the transformation pathways and functional microorganisms responsible for HFRs biotransformation. Finally, the potential impacts of HFRs on reactor performance (i.e., nitrogen removal and methanogenesis) and microbiome in bioreactors are discussed. This review aims to advance our understanding of the fate and impacts of HFRs in WWTPs and shed light on important questions warranting further investigation.

Facile synthesis of polyoxometalate-modified metal organic frameworks for eliminating tetrabromobisphenol-A from water

Removal of tetrabromobisphenol-A (TBBPA) from wastewater is of significance to protect the aquatic life. The present study reports the facile preparation of polyoxometalate-modified metal-organic framework (MOFs) materials for TBBPA removal from water. The polyoxometalate-modified MOFs exhibited significantly higher affinity towards TBBPA than the control MOFs. The experimental data were fitted with the Langmuir, Freundlich and Dubinin-Radushkevich models. The TBBPA adsorption onto modified MOFs fitted the pseudo-second-order kinetic model. The equilibrium adsorption isotherms showed that the adsorption of TBBPA can be fitted by the Langmuir model. The maximum adsorption capacity of adsorbent composites reached 3.65 mg/g, with 95 % removal of TBBPA. The thermodynamic parameters indicated that adsorption was spontaneous. A blue shift of phosphorus peaks obtained from XPS spectra implied the formation of intrinsic chemical bonding between TBBPA and MOFs composites. Moreover, response surface methodology was employed to characterize the TBBPA adsorption in the co-existence of different factors. BPA had strong competition for TBBPA adsorption in a wide range of pH, but not at the middle level of Ca²⁺ concentration. Polyoxometalate-modified MOFs can easily be recycled using a simple organic solvent washing. This study provides a novel strategy for developing cost effective adsorbents to remove TBBPA from contaminated water.

Biodegradation of hexabromocyclododecane by Rhodopseudomonas palustris YSC3 strain: A free-living nitrogen-fixing bacterium isolated in Taiwan

The persistent organic pollutant, brominated flame retardant, hexabromocyclododecane (HBCD), identified as an emerging contaminant has been detected in various environmental matrix. The increased level of this toxic organic compound in the environment has been associated with serious human health risks. The results obtained from this study revealed that various Rhodopseudomonas palustris strains isolated from paddy soil in Taiwan possessed good HBCD biodegradation capability when they were cultured aerobically. Among these strains, YSC3 was considered as one of the most potential isolates for HBCD degradation. The optimum HBCD biodegradation occurred at neutral pH and at 35 °C in all our pH and temperature tests at an initial HBCD concentration of 1 ppm. HBCD degradation kinetics generally decreased with the increase of initial HBCD concentration. The study also suggested that the cultivation temperature played a vital role on YSC3 for its initiation of cellular HBCD degradation. The relative-molar ratio of the released bromide ions during the biodegradation of HBCD was observed in the range between 1 and 3.5, suggesting that the debromination reactions occurred. Concomitant with the loss of HBCD, there was a concurrent production of two metabolites, pentabromocyclododecanol and pentabromocyclododecene, which were determined by liquid chromatography and mass spectrometry techniques. On the basis of the obtained results, the possible biodegradation pathways were also proposed in this study.

Effect of mangrove species on removal of tetrabromobisphenol A from contaminated sediments

The increase levels of tetrabromobisphenol A (TBBPA) in mangrove wetlands is of concern due to its potential toxic impacts on ecosystem. A 93-day greenhouse pot experiment was conducted to investigate the effects of mangrove plants, A. marina and K. obovata, on TBBPA degradation in sediment and to reveal the associated contributing factor(s) for its degradation. Results show that both mangrove species could uptake, translocate, and accumulate TBBPA from mangrove sediments. Compared to the unplanted sediment, urease and dehydrogenase activity as well as total bacterial abundance increased significantly (p < 0.05) in the sediment planted with mangrove plants, especially for K. obovata. In the mangrove-planted sediment, the Anaerolineae genus was the dominant bacteria, which has been reported to enhance TBBPA dissipation, and its abundance increased significantly in the sediment at early stage (0-35 day) of the greenhouse experiment. Compared to A. marina-planted sediment, higher enrichment of Geobater, Pseudomonas, Flavobacterium, Azoarcus, all of which could stimulate TBBPA degradation, was observed for the K. obovata-planted sediment during the 93-day growth period. Our mass balance result has suggested that plant-induced TBBPA degradation in the mangrove sediment is largely due to elevated microbial activities and total bacterial abundance in the rhizosphere, rather than plant uptake. In addition, different TBBPA removal efficiencies were observed in the sediments planted with different mangrove species. This study has demonstrated that K. obovata is a more suitable mangrove species than A. marina when used for remediation of TBBPA-contaminated sediment.

Microbial Transformation of A Sulfonamide Antibiotic Under Various Background Nutrient Conditions

Certain microbes can biotransform antibiotics. Little is known about these microbes or the biotransformation processes. The objective of this study was to determine the effects of background nutrient conditions on a sulfonamide degrading culture and on its biotransformation of sulfadiazine (SDZ) with respect to transformation kinetics and transformation products. The mixed culture capable of degrading SDZ consisted primarily of three genera, Brevibacterium, Castellaniella and Leucobacter. The maximum biotransformation rate was 4.55 mg L^-1 d^-1 in the absence of background nutrients. Among the three background nutrient conditions tested, diluted R2A medium lead to the highest maximum SDZ biotransformation rates, followed by humic acid and glucose. 2-aminopyrimidine was the major SDZ biotransformation product under the background nutrient conditions tested, while another previously reported biotransformation product, sulfanilic acid, was further degraded by the mixed culture. The findings from this study can help improve our estimation of the fate of antibiotics in the environment.

Using high-throughput transcriptome sequencing to investigate the biotransformation mechanism of hexabromocyclododecane with Rhodopseudomonas palustris in water

We discovered one purple photosynthetic bacterium, Rhodopseudomonas palustris YSC3, which has a specific ability to degrade 1, 2, 5, 6, 9, 10-hexabromocyclododecane (HBCD). The whole transcriptome of R. palustris YSC3 was analyzed using the RNA-based sequencing technology in illumina and was compared as well as discussed through Multi-Omics onLine Analysis System (MOLAS, http://molas.iis.sinica.edu.tw/NTUIOBYSC3/) platform we built. By using genome based mapping approach, we can align the trimmed reads on the genome of R. palustris and estimate the expression profiling for each transcript. A total of 341 differentially expressed genes (DEGs) in HBCD-treated R. palustris (RPH) versus control R. palustris (RPC) was identified by 2-fold changes, among which 305 genes were up-regulated and 36 genes were down-regulated. The regulated genes were mapped to the database of Gene Ontology (GO) and Genes and Genomes Encyclopedia of Kyoto (KEGG), resulting in 78 pathways being identified. Among those DEGs which annotated to important functions in several metabolic pathways, including those involved in two-component system (13.6%), ribosome assembly (10.7%), glyoxylate and dicarboxylate metabolism (5.3%), fatty acid degradation (4.7%), drug metabolism-cytochrome P450 (2.3%), and chlorocyclohexane and chlorobenzene degradation (3.0%) were differentially expressed in RPH and RPC samples. We also identified one transcript annotated as dehalogenase and other genes involved in the HBCD biotransformation in R. palustris. Furthermore, the putative HBCD biotransformation mechanism in R. palustris was proposed.

Degradation of tetrabromobisphenol a by ozonation: Performance, products, mechanism and toxicity

This study systematically investigated the performance of ozonation on tetrabromobisphenol A (TBBPA) degradation under different ozone dosages (5.21-83.33 μmoL/L), initial solution pH (3.0-11.0) and temperatures (10-50 °C). At the same time, the generations of inorganic products (bromide ion and bromate) under different experimental conditions were evaluated and the organic products were also identified. Then, the possible mechanism was proposed and verified by the quantum chemical calculation. In addition, variations and controlling of the toxicity were also analyzed, including acute toxicity, chronic toxicity and genotoxicity. Ozonation was proved to be an efficient and promising technology for removing TBBPA from water. TBBPA of 1.84 μmoL/L could be completely degraded within 5 min under the ozone dosage of 41.67 μmoL/L in wide ranges of pH (3.0-11.0) and temperature (10-40 °C). During the degradation of TBBPA, over 65% of the average bromine ion was detected and nine products were identified. The proposed degradation pathways verified that TBBPA might undergo addition and stepwise oxidative debromination, the hydrogen extraction, and the deprotonation. The results of toxicity testing showed that ozonation could effectively control the acute and chronic toxicity of the water samples, although the toxicity increased in the initial reaction stage due to the accumulation of more toxic intermediates.

Tetrabromobisphenol A (TBBPA) inhibits denitrification via regulating carbon metabolism to decrease electron donation and bacterial population

The potential risks of brominated flame retardants (BFRs) like tetrabromobisphenol A (TBBPA) have attracted much attention. However, the influence of TBBPA on functional microbes remains poorly understood, especially with regards to denitrification, which is closely related with the carbon and nitrogen cycles, eutrophication and greenhouse gas emission. Herein, we found that 1.0 mg/L of TBBPA significantly decreased the total nitrogen removal efficiency by 81.7%, but increased the accumulation of NO₂^--N (by 81.5%) and N₂O (by 172-fold). This was found to be underlie by the significant decrease in both the denitrifying capability of denitrifiers and total bacterial population. Further investigation revealed that TBBPA inhibited the pathways of glucolysis and pentose phosphate, and promoted glyoxylate bypass via regulating genes expressions of key enzymes (such as glucose-6-phosphate isomerase, pyruvate dehydrogenase, isocitrate lyase, etc.), then decreased the generation of NADH serving as electron donor for denitrification, and inhibited the denitrifying capability of denitrifiers. Moreover, insufficient NADH stimulated the accumulation of denitrifying intermediates (NO₂^--N and N₂O), which induced the increase of reactive nitrogen species (RNS), whose accumulation decreased proliferation and increased apoptosis of denitrifying bacteria. Finally, the decrease in the denitrifying capability of denitrifier and bacterial population resulted in negative denitrifying performance.

Acetate promotes microbial reductive debromination of tetrabromobisphenol A during the startup phase of anaerobic wastewater sludge bioreactors

The detection of increasing concentrations of tetrabromobisphenol A (TBBPA) in wastewater treatment plants is raising concerns as TBBPA has been identified as a potentially toxic flame retardant. The objectives of this study were to evaluate the effect of acetate biostimulation on TBBPA microbial reductive debromination, and the response of anaerobic sludge associated microbial communities repeatedly exposed to TBBPA. Results indicate that the bulk of the microbial community did not experience significant shifts as a result of TBBPA exposure, and that only a small fraction of the community responded to the presence of TBBPA. Taxa most likely responsible for TBBPA transformation affiliated to Clostridiales and the wastewater sludge group Blvii28. The biostimulating effect of acetate was only observed during reactor startup, when acetogenesis was likely not yet occurring. However, when acetate likely started to be microbially generated in the reactor, acetate addition resulted in a slight but significant inhibiting effect on TBBPA transformation. A significant increase of hydrogenotrophic methanogens in the TBBPA-spiked reactor overtime implies that TBBPA degraders were not in direct competition with methanogens for H₂. These results strongly suggest that TBBPA degrading taxa might have been primarily using acetate as an electron donor for the reductive debromination of TBBPA.

Application of a novel gene encoding bromophenol dehalogenase from Ochrobactrum sp. T in TBBPA degradation

Tetrabromobisphenol-A (TBBPA), a typical brominated flame retardant, leaked from commercial products into the environments has attracted people's attention around the world. Ochrobactrum sp. T capable of degradation and mineralization of TBBPA was isolated in our early work. In this study, the identification of TBBPA-degrading gene from the strain was further carried out by combining whole-genome sequencing with gene cloning and expression procedures. In total, 3877 open reading frames were found within 3.9 Mb genome and seven of them were identified as dehalogenating-relating genes. One gene with a significant ability to degrade TBBPA was designated as tbbpaA. Sequence alignments analysis showed that it shared 100% identity with haloacid dehalogenases. Furthermore, tbbpaA gene was cloned and expressed into E. coli to achieve a constructed strain. Like the original strain, the constructed strain could degrade TBBPA (6 mg L^-1) with 78% of debromination efficiency and 37.8% mineralization efficiency within 96 h. Gene expression study revealed that tbbpaA was up-regulated in the presence of TBBPA. Overall, we report the identification of a functional TBBPA-degrading gene in an aerobe, which can deepen the knowledge of enhancing TBBPA removal by Strain T at the genetic level and facilitate in situ TBBPA bioremediation.

Transformation/degradation of tetrabromobisphenol A and its derivatives: A review of the metabolism and metabolites

Although the abiotic and biotic transformation/degradation (T/D) processes of tetrabromobisphenol A (TBBPA) have been widely investigated in model experiments, few reviews have focused on these processes along with their metabolites or degradation products. In this paper, we summarize the current knowledge on the T/D of TBBPA and its derivatives, including abiotic and biotic T/D strategies/conditions, mechanisms, metabolites and environmental occurrences. Various treatments, such as pyrolysis, photolysis, chemical reactions and biotransformation, have been employed to study the metabolic mechanism of TBBPA and its derivatives and to remediate associated contaminated environments. To date, more than 100 degradation products and metabolites have been identified, dominated by less brominated compounds such as bisphenol A, 2,6-dibromo-4-isopropylphenol, 2,6-dibromo-4-hydroxyl-phenol, 2,6-dibromophenol, isopropylene-2,6-dibromophenol, 4-(2-hydroxyisopropyl)-2,6-dibromophenol, etc. It can be concluded that the T/D of TBBPA mainly takes place through debromination and β-scission. In some environmental media and human and animal tissues, brominated metabolites, glucoside and sulfate derivatives are also important T/D products. Here, the T/D products of TBBPA and its derivatives have been most comprehensively presented from the literature in recent 20 years. This review will enhance the understanding of the environmental behaviors of TBBPA-associated brominated flame retardants along with their ecological and health risks.

Distribution, release and removal behaviors of tetrabromobisphenol A in water-sediment systems under prolonged hydrodynamic disturbances

Since tetrabromobisphenol A (TBBPA) has been increasingly used and found widely in the aquatic environment, it has attracted much attention due to its high toxicity to aquatic organisms. However, less work has been carried out for the TBBPA environmental fate in water-sediment systems. In this paper, the distribution, release and removal of TBBPA in different forms of the water-sediment system were investigated under three typical hydrodynamic conditions using a specialized racetrack-style flume. Three water-sediment systems which are water, suspended particulate matter (SPM) and sediment were taken into account in this study. The results of 34 days experiments showed that the equilibrium of physicochemical parameters was reached under different disturbance conditions within a relatively short period. The distribution ratio of TBBPA in three water-sediment systems will also reach a relatively equilibrium state over time under different disturbance conditions. The fluctuation range in each form was <1.26%. The TBBPA released to the water and SPM, increased remarkably with hydrodynamic enhancement due to adsorption and resuspension processes. Removal efficiency of TBBPA in each form was found to be observably accelerated with hydrodynamic disturbances. The half-lives (T_1/2) in water, SPM and sediment ranged from 10.1 to 12.6 days in strong hydrodynamic condition, comparing to the static control, it ranges from 34.7 to 37.1 days. This phenomenon may result from the increase of dissolved oxygen (DO) and nutrient concentrations in overlying water affected by hydrodynamic force. The results of the experiment demonstrate that hydrodynamic disturbance may be an important driving factor which will influence the TBBPA environmental fate in aquatic environment.

Degradation of tetrabromobisphenol A in a paddy soil during sequential anoxic-oxic incubation: Kinetics, metabolites, and potential pathways

Due to the increasing pollution of tetrabromobisphenol A (TBBPA) in paddy soils, it is of great importance to explore the degradation of TBBPA under repeated anoxic-oxic conditions. In the present study, the degradation of TBBPA (kinetics, metabolites and potential pathways) and the influence of low molecular weight organic acid i.e., lactic acid were investigated in a paddy soil during sequential anoxic-oxic incubations. Under the anoxic condition, TBBPA in the non-sterile soils was efficiently debrominated into three intermediates (including tri-BBPA, di-BBPA and mono-BBPA) and bisphenol A (BPA) with a rate constant (k) of 0.0371 d⁻¹ and a half-life (t_1/2) of 60.8 d. The debromination end product (BPA) steadily accumulated. Next, turning to the oxic conditions, the anaerobically accumulated BPA degraded rapidly, while the intermediates and TBBPA were desorbed from the bound residues and were persistent. The detection of tri-BBPA followed by di-BBPA and mono-BBPA thereafter indicated that the dehalogenation of TBBPA was likely a stepwise removal of bromine atoms. A pathway of TBBPA → tri-BBPA → di-BBPA → mono-BBPA → BPA was thus proposed for TBBPA degradation. The degradation of TBBPA and its metabolites was biologically mediated. Moreover, the biodegradation of TBBPA could be significantly accelerated by the addition of lactic acid as an exogenous carbon source and electron donor, with k being increased to 0.0766 d⁻¹ and t_1/2 being shortened to 31.9 d. The information will improve our understanding of biotic process associated with agronomic practices (such as applying organic fertilizers) contributing to TBBPA attenuation in the natural soil environment.

Debromination of Hexabromocyclododecane by Anaerobic Consortium and Characterization of Functional Bacteria

A microbial consortium which can efficiently remove hexabromocyclododecane (HBCD) under anaerobic condition have been successfully enriched over 300 days. Under the optimal conditions, the degradation efficiency was 92.4% removal after treatment of 12 days with original addition of 500 μg/L HBCD, yielding 321.7 μg/L bromide in total as well. A typical debromination product, dibromocyclododecadiene (DBCD), was detected during the degradation process. The debromination profiles of three main HBCD diastereomers fitted well with first-order model (R²: 0.96–0.99), with the rate constants ranging from 1.3 × 10^-1 to 1.9 × 10^-1. The microbial community analysis by high throughput sequencing showed that the composition of the microbial communities varied dynamically with time and the population of functional bacteria increase sharply after enrichment. The population of Bacteroidetes increased from 5 to 47%. And some bacteria which are relatively minority in population at the beginning, such as Azospira oryzae (OTU2), Microbacterium (OTU13), and Achromobacter insolitus (OTU39) increased more than 22 times after enrichment (from 0.5 to 13%, 12%, and 11%, respectively). However, no reported dehalogenating bacteria were found after enrichment. And the contribution for debromination may come from new dehalogenating bacteria. All in all, the present study provided in-depth information on anaerobic microbial communities for HBCD removal by debromination.

Can Microalgae Remove Pharmaceutical Contaminants from Water?

The increase in worldwide water contamination with numerous pharmaceutical contaminants (PCs) has become an emerging environmental concern due to their considerable ecotoxicities and associated health issues. Microalgae-mediated bioremediation of PCs has recently gained scientific attention, as microalgal bioremediation is a solar-power driven, ecologically comprehensive, and sustainable reclamation strategy. In this review, we comprehensively describe the current research on the possible roles and applications of microalgae for removing PCs from aqueous media. We summarize several novel approaches including constructing microbial consortia, acclimation, and cometabolism for enhanced removal of PCs by microalgae, which would improve practical feasibility of these technologies. Some novel concepts for degrading PCs using integrated processes and genetic modifications to realize algal-based bioremediation technologies are also recommended.

Background Nutrients Affect the Biotransformation of Tetracycline by Stenotrophomonas maltophilia as Revealed by Genomics and Proteomics

Certain bacteria are resistant to antibiotics and can even transform antibiotics in the environment. It is unclear how the molecular mechanisms underlying the resistance and biotransformation processes vary under different environmental conditions. The objective of this study is to investigate the molecular mechanisms of tetracycline resistance and biotransformation by Stenotrophomonas maltophilia strain DT1 under various background nutrient conditions. Strain DT1 was exposed to tetracycline for 7 days with four background nutrient conditions: no background (NB), peptone (P), peptone plus citrate (PC), and peptone plus glucose (PG). The biotransformation rate follows the order of PC > P > PG > NB ≈ 0. Genomic analysis showed that strain DT1 contained tet(X1), a gene encoding an FAD-binding monooxygenase, and eight peroxidase genes that could be relevant to tetracycline biotransformation. Quantitative proteomic analyses revealed that nodulation protein transported tetracycline outside of cells; hypoxanthine-guanine phosphoribosyltransferase facilitated the activation of the ribosomal protection proteins to prevent the binding of tetracycline to the ribosome and superoxide dismutase and peroxiredoxin-modified tetracycline molecules. Comparing different nutrient conditions showed that the biotransformation rates of tetracycline were positively correlated with the expression levels of superoxide dismutase.

Anaerobic co-metabolic biodegradation of tetrabromobisphenol A using a bioelectrochemical system

Tetrabromobisphenol A(TBBPA), a pollutant in industrial wastewaters, needs to be removed due to its high toxicity and persistence. The main biodegradation pathway for TBBPA has been studied, and bisphenol A(BPA), which is toxic to the environment, is recognized as the general terminal product. In this study, we explored a new approach for the anaerobic biodegradation of TBBPA in a bioelectrochemical system (BES) through co-metabolic degradation of TBBPA with glucose. The half-life of TBBPA was significantly reduced to 13.5h^-1 at 25μg/l of TBBPA. With an increase in the concentration of TBBPA, the removal rates of TBBPA rose to more than eighty percent. Based on the analysis of the products, we found that the degradation products of TBBPA were 2,6-dibromo-4-(1-methyl-1-phenylethyl) phenol, (double-benzenes product) and 2,6-dibromo-4-(prop-1-en-2-yl) phenol (single-benzene product), rather than BPA. Simultaneously, we proposed two degradation pathways for TBBPA in a BES system. According to the microbial diversity analysis of the anode biofilm, we speculated that the microorganism responsible for the biodegradation of TBBPA was Azoarcus. Additionally, we briefly analyzed the effect of TBBPA on the performance of BES system to pave the way for the further analysis of the interaction between the TBBPA and the BES system.

Optimization of culturing conditions for isolated Arthrobacter sp. ZXY-2, an effective atrazine-degrading and salt-adaptive bacterium

The isolated strainArthrobactersp. ZXY-2 could biodegrade atrazine effectively with high salinity resistance.

A review of the environmental distribution, fate, and control of tetrabromobisphenol A released from sources

Tetrabromobisphenol A (TBBPA), a high use brominated flame retardant (BFR), raising concerns of widespread pollution and harm to human and ecological health. BFR manufacturing, TBBPA-based product manufacturing, e-waste recycling, and wastewater treatment plants have been identified as the main emission point sources. This paper discusses the occurrence, distribution, and fate of TBBPA from source to the environment. After release to the environment, TBBPA may undergo adsorption, photolysis, and biological degradation. Exposure of humans and biota is also discussed along with the role of treatment and regulations in reducing release of TBBPA to the environment and exposure risks. In general this review found stronger enforcement of existing legislation, and investment in treatment of e-waste plastics and wastewater from emission point sources could be effective methods in reducing release and exposure of TBBPA in the environment.

Characterization and Adaptation of Anaerobic Sludge Microbial Communities Exposed to Tetrabromobisphenol A

The increasing occurrence of tetrabromobisphenol A (TBBPA) in the environment is raising questions about its potential ecological and human health impacts. TBBPA is microbially transformed under anaerobic conditions to bisphenol A (BPA). However, little is known about which taxa degrade TBBPA and the adaptation of microbial communities exposed to TBBPA. The objectives of this study were to characterize the effect of TBBPA on microbial community structure during the start-up phase of a bench-scale anaerobic sludge reactor, and identify taxa that may be associated with TBBPA degradation. TBBPA degradation was monitored using LC/MS-MS, and the microbial community was characterized using Ion Torrent sequencing and qPCR. TBBPA was nearly completely transformed to BPA via reductive debromination in 55 days. Anaerobic reactor performance was not negatively affected by the presence of TBBPA and the bulk of the microbial community did not experience significant shifts. Several taxa showed a positive response to TBBPA, suggesting they may be associated with TBBPA degradation. Some of these taxa had been previously identified as dehalogenating bacteria including Dehalococcoides, Desulfovibrio, Propionibacterium, and Methylosinus species, but most had not previously been identified as having dehalogenating capacities. This study is the first to provide in-depth information on the microbial dynamics of anaerobic microbial communities exposed to TBBPA.

The potential of using low cost naturally available biogenic substrates for biological removal of chlorophenol

This study details the application of naturally available biogenic substrates (NABS) in microbial degradation of 2-chlorophenol (CP). Jatropha deoiled cakes (JDC) and Karanja deoiled cakes (KDC) are used as NABS. The potential of NABS is compared with standard biogenic substrate, glucose. The study was carried out with both acclimatized mixed culture and pure culture, Pseudomonas putida. Microbial activity of the culture was monitored by measuring reduction in chlorophenol concentration, COD, toxicity and Cl(-) ions evolution. The study was carried out for a total of 42days. It was observed that culture having NABS has shown similar chlorophenol reduction but higher COD and toxicity reduction. Amongst NABS, Jatropha deoiled cake (JDC) has shown superior results of 71% COD reduction compared to glucose and KDC. This study is one of the first kind illustrating the potential of these substrates in removing toxic chemicals from wastewaters.

Study of novel pure culture HBCD-1, effectively degrading Hexabromocyclododecane, isolated from an anaerobic reactor

In this study, two pure strains, named HBCD-1 and HBCD-2, were isolated from a continuous anaerobic reactor over 300-days acclimation, which processed high capability of biodegrading Hexabromocyclododecane. Both of the two strains degraded HBCD diastereomers in different extents, especially strain HBCD-1, which interestingly degraded α-HBCD effectively. All of the degrading results were well fitted with the first-order kinetics model. By morphological observation and 16S rRNA gene sequence analysis, the strain HBCD-1 showed highest similarity with Achromobacter sp. Under the optimal culturing conditions of 30°C, pH 7 and the initial HBCD concentration of 500μg/L, the biodegradation rate of HBCD-1 reached 90% after 8days treatment. Moreover, during the biodegradation process by HBCD-1 strain, the concentration of bromide ion was lower than the theoretical value. Finally, 4 metabolites were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS), as well as a biodegradation pathway was proposed.

Co-metabolic degradation of tetrabromobisphenol A by novel strains of Pseudomonas sp. and Streptococcus sp

Three strains capable of rapidly degrading TBBPA by co-metabolism and utilizing formate as the carbon source, named as J-F-01, J-F-02, and J-F-03, respectively, were isolated from enrichment cultures, which have been treated with 0.5mg/L TBBPA for 240 d. Based on morphology and 16S rRNA gene sequence analysis, both J-F-01 and J-F-02 were determined to Pseudomonas sp., while J-F-03 was identified as Streptococcus sp. A shorter half-life (6.1d) of TBBPA was observed in pure culture of J-F-03 when compared with J-F-01 (22.5d) and J-F-02 (13.6d). Surprisingly, the degradation of TBBPA was significantly enhanced by the mixed culture of J-F-02 and J-F-03. The optimal degradation conditions for the mixed cultures were determined. Under the optimal conditions, TBBPA (0.5mg/L) was completely metabolized by the mixed culture within ten days. Moreover, bromide and the metabolisms were detected, and a possible metabolic pathway was deduced from the detection of metabolite production patterns.

Bioremediation of coking wastewater containing carbazole, dibenzofuran, dibenzothiophene and naphthalene by a naphthalene-cultivated Arthrobacter sp. W1

A naphthalene-utilizing bacterium, Arthrobacter sp. W1, was used to investigate the cometabolic degradation of carbazole (CA), dibenzofuran (DBF) and dibenzothiophene (DBT) using naphthalene as the primary substrate. Both the growing and washed cells of strain W1 could degrade CA, DBF, DBT, and naphthalene simultaneously and quickly. Inhibition kinetics confirmed that the presence of CA, DBF and DBT in the growing system would inhibit the cells growth and biodegradability of strain W1. The relationship between ln(C/C0) and time, and specific degradation rate and CA, DBF and DBT concentration could be described well by First-order and Michaelis-Menten kinetics. The treatment of real coking wastewater containing high concentration of phenol, naphthalene, CA, DBF, DBT and NH3-N was shown to be highly efficient by naphthalene-grown W1 coupling with activation zeolite. Toxicity assessment indicated the treatment of the coking wastewater by strain W1 coupling with activation led to less toxicity than untreated wastewater.

Cometabolic degradation of organic wastewater micropollutants by activated sludge and sludge-inherent microorganisms

Municipal wastewaters contain a multitude of organic trace pollutants. Often, their biodegradability by activated sludge microorganisms is decisive for their elimination during wastewater treatment. Since the amounts of micropollutants seem too low to serve as growth substrate, cometabolism is supposed to be the dominating biodegradation process. Nevertheless, as many biodegradation studies were performed without the intention to discriminate between metabolic and cometabolic processes, the specific contribution of the latter to substance transformations is often not clarified. This minireview summarizes current knowledge about the cometabolic degradation of organic trace pollutants by activated sludge and sludge-inherent microorganisms. Due to their relevance for communal wastewater contamination, the focus is laid on pharmaceuticals, personal care products, antibiotics, estrogens, and nonylphenols. Wherever possible, reference is made to the molecular process level, i.e., cometabolic pathways, involved enzymes, and formed transformation products. Particular cometabolic capabilities of different activated sludge consortia and various microbial species are highlighted. Process conditions favoring cometabolic activities are emphasized. Finally, knowledge gaps are identified, and research perspectives are outlined.