Biodegradation of tributyl phosphate using Klebsiella pneumoniae sp. S3

OPFR removal by white rot fungi: screening of removers and approach to the removal mechanism

The persistent presence of organophosphate flame retardants (OPFRs) in wastewater (WW) effluents raises significant environmental and health concerns, highlighting the limitations of conventional treatments for their remotion. Fungi, especially white rot fungi (WRF), offer a promising alternative for OPFR removal. This study sought to identify fungal candidates (from a selection of four WRF and two Ascomycota fungi) capable of effectively removing five frequently detected OPFRs in WW: tributyl phosphate (TnBP), tributoxy ethyl phosphate (TBEP), trichloroethyl phosphate (TCEP), trichloro propyl phosphate (TCPP) and triethyl phosphate (TEP). The objective was to develop a co-culture approach for WW treatment, while also addressing the utilization of less assimilable carbon sources present in WW. Research was conducted on carbon source uptake and OPFR removal by all fungal candidates, while the top degraders were analyzed for biomass sorption contribution. Additionally, the enzymatic systems involved in OPFR degradation were identified, along with toxicity of samples after fungal contact. Acetate (1.4 g·L-1), simulating less assimilable organic matter in the carbon source uptake study, was eliminated by all tested fungi in 4 days. However, during the initial screening where the removal of four OPFRs (excluding TCPP) was tested, WRF outperformed Ascomycota fungi. Ganoderma lucidum and Trametes versicolor removed over 90% of TnBP and TBEP within 4 days, with Pleorotus ostreatus and Pycnoporus sanguineus also displaying effective removal. TCEP removal was challenging, with only G. lucidum achieving partial removal (47%). A subsequent screening with selected WRF and the addition of TCPP revealed TCPP's greater susceptibility to degradation compared to TCEP, with T. versicolor exhibiting the highest removal efficiency (77%). This observation, plus the poor degradation of TEP by all fungal candidates suggests that polarity of an OPFR inversely correlates with its susceptibility to fungal degradation. Sorption studies confirmed the ability of top-performing fungi of each selected OPFR to predominantly degrade them. Enzymatic system tests identified the CYP450 intracellular system responsible for OPFR degradation, so reactions of hydroxylation, dealkylation and dehalogenation are possibly involved in the degradation pathway. Finally, toxicity tests revealed transformation products obtained by fungal degradation to be more toxic than the parent compounds, emphasizing the need to identify them and their toxicity contributions. Overall, this study provides valuable insights into OPFR degradation by WRF, with implications for future WW treatment using mixed consortia, emphasizing the importance of reducing generated toxicity.

Novel method for rapid monitoring of OPFRs by LLE and GC-MS as a tool for assessing biodegradation: validation and applicability

Organophosphate flame retardants (OPFRs) are high-production volume chemicals widely present in environmental compartments. The presence of water-soluble OPFRs (tri-n-butyl phosphate (TnBP), tris(2-butoxyethyl) phosphate (TBEP), tris(2-chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCPP), and triethyl phosphate (TEP)) in water compartments evidences the struggle of conventional wastewater treatment plants (WWTPs) to effectively eliminate these toxic compounds. This study reports for the first time the use of white-rot fungi as a promising alternative for the removal of these OPFRs. To accomplish this, a simple and cost-efficient quantification method for rapid monitoring of these contaminants' concentrations by GC-MS while accounting for matrix effects was developed. The method proved to be valid and reliable for all the tested parameters. Sample stability was examined under various storage conditions, showing the original samples to be stable after 60 days of freezing, while post-extraction storage techniques were also effective. Finally, a screening of fungal degraders while assessing the influence of the glucose regime on OPFR removal was performed. Longer chain organophosphate flame retardants, TBP and TBEP, could be easily and completely removed by the fungus Ganoderma lucidum after only 4 days. This fungus also stood out as the sole organism capable of partially degrading TCEP (35% removal). The other chlorinated compound, TCPP, was more easily degraded and 70% of its main isomer was removed by T. versicolor. However, chlorinated compounds were only partially degraded under nutrient-limiting conditions. TEP was either not degraded or poorly degraded, and it is likely that it is a transformation product from another OPFR's degradation. These results suggest that degradation of chlorinated compounds is dependent on the concentration of the main carbon source and that more polar OPFRs are less susceptible to degradation, given that they are less accessible to radical removal by fungi. Overall, the findings of the present study pave the way for further planned research and a potential application for the degradation of these contaminants in real wastewaters.

Treatment of tributyl phosphate by fenton oxidation: Optimization of parameter, degradation kinetics and pathway

In nuclear industry, tributyl phosphate (TBP) is used as organic extracting solvent to separate uranium and plutonium. The spent TBP is finally discarded as the radioactive organic waste, which should be treated due to its potential risk. In this study, TBP degradation by Fenton oxidation was investigated in detail, including the optimization of operational conditions, degradation kinetics and degradation products. The optimal conditions for TBP degradation (per 10 ml) by Fenton oxidation was: 95 °C, pH 2, 150 ml 30% H₂O₂, and 105 ml 0.2 M Fe(II). H₂O₂ was continuously added with the flow rate of 0.5 ml/min, Fe(II) was intermittently added with the flow rate of 3 ml/10 min. The oil phase volume decreased with time and completely disappeared at the third hour. In contrast, the COD in water phase increased firstly and then decreased. At the end of the experiments, the COD achieved 23.8 g/L. The detection of phosphorus in water phase further confirmed the decomposition of TBP. Mono-butyl phosphate and di-butyl phosphate were identified as the intermediate products of TBP degradation. In addition, other four degradation products with the same m/z of 154 were identified, which may be derived from the hydroxylation of mono-butyl phosphate and di-butyl phosphate. Based on the degradation products, the degradation pathway of TBP was proposed. This study could provide an insight into the TBP degradation by Fenton oxidation, and an potential strategy for treating the spent radioactive organic solvent.

Adsorption behavior of hierarchical porous biochar from shrimp shell for tris(2-chloroethyl) phosphate (TCEP): Sorption experiments and DFT calculations

Tris(2-chloroethyl) phosphate (TCEP) as a new type of flame retardant exists in various water environments, causing great risks to humans and the environment. In this study, shrimp shell was used to prepare an economical and environmental-friendly adsorbent for the efficient removal of TCEP. The systematic studies including characterization, removal performance, and adsorption mechanism of shrimp shell biochar toward TCEP were carried out. Adsorption kinetics and thermodynamics showed that fast equilibrium reached within 30 min, the maximum adsorption capacity q_m was 108 μmol g^-1 at 298 K, and the adsorption process is spontaneous and exothermic. The environmental factor, such as temperature, pH, inorganic anions and organic matter hardly affected the adsorption performance. Structural characterization indicated that the hierarchical porous structure of shrimp shell biochar is the key to excellent adsorption performance. The adsorption mechanisms were further revealed using density functional theory (DFT) calculations, and the hydrogen bond, van der Waals interactions, Cl-H interactions, and pi-H interactions were identified as potential interaction mechanisms between TCEP and specific biochar structures. The calculated binding energy between TCEP and simplified biochar structure suggested that oxygen-containing groups especially carboxyl, hydroxyl and aldehyde facilitate the adsorption. Our work not only provides a novel strategy for the quick remediation of organophosphate-contaminated water environments but also offers new opportunities for crustacean waste biomass valorization.

Mechanisms of flame retardant tris (2-ethylhexyl) phosphate biodegradation via novel bacterial strain Ochrobactrum tritici WX3-8

Tris (2-ethylhexyl) phosphate (TEHP) is a common organophosphorus flame retardant analog with considerable ecological toxicity. Here, novel strain Ochrobactrum tritici WX3-8 capable of degrading TEHP as the sole C source was isolated. Our results show that the strain's TEHP degradation efficiency reached 75% after 104 h under optimal conditions, i.e., 30 °C, pH 7, bacterial inoculum 3%, and Collapse

Key Words

• Biodegradation
• Metabolic pathway
• Ochrobactrum tritici
• Organic pollutants

Collapse

MESH Headings Collapse

Grants Collapse

Affiliation(s)

Jiamei He College of Environment, Zhejiang University of Technology, Hangzhou, 310032, China
Zeyu Wang Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou, 310015, China
Fengzhen Zhen College of Biological and Environmental Engineering, Zhejiang Shuren University, Hangzhou, 310015, China
Zhaoyun Wang College of Environment, Zhejiang University of Technology, Hangzhou, 310032, China
Zhongdi Song Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou, 310015, China
Jun Chen Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou, 310015, China.
Dzmitry Hrynsphan Research Institute of Physical and Chemical Problems, Belarusian State University, Minsk, 220030, Belarus
Savitskaya Tatsiana Research Institute of Physical and Chemical Problems, Belarusian State University, Minsk, 220030, Belarus

Collapse

Efficient removal of organophosphate esters by ligand functionalized MIL-101 (Fe): Modulated adsorption and DFT calculations

Organophosphate esters (OPEs) are a new class of flame retardants present in diverse waters. The study focused on the removal of aqueous OPEs using functionalized MIL-101(Fe), which was a representative of the metal-organic frameworks (MOFs). Adsorption kinetics of tris(2-chloroethyl) phosphate (TCEP), tributyl phosphate (TnBP), and triphenyl phosphate (TPhP) were investigated. Additionally, TCEP was selected as the model contaminant to study the adsorption isotherms, thermodynamics, and effect of solution matrix properties. Adsorption mechanisms obtained from the experiments were confirmed using density functional theory (DFT) calculations. Adsorption kinetics indicated that functionalized MOFs provided a significant enhancement to the removal of TCEP. The maximum adsorption capacities q_m of MIL-101(Fe), MIL-101(Fe)-NH₂, MIL-101(Fe)-OH, and MIL-101(Fe)-CH₃ at 298 K for TCEP were 76.040, 282.940, 119.680, and 181.274 μmol/g, respectively. By comparing the adsorption behavior of functionalized MOFs, MIL-101(Fe)-NH₂ was proved to be most efficient for TCEP removal. Based on the adsorption experiments and DFT calculations, TCEP removal was dominated by physical adsorption. The van der Waals (vdW) interactions and hydrogen bonding were assumed to be involved in the adsorption. This work proves that appropriate ligand functionalization is promising for the removal of aqueous OPEs, which also provides a new insight for the control of OPEs pollution.

Mining the diversity and functional profile of bacterial symbionts from the larvae of Chironomus circumdatus (bloodworms)

Chironomids are the most abundant aquatic insects in freshwater habitats that can survive in extreme conditions. In this study, as the microbiome provides extended genotype to the host to perform various functions, we explored the microbiota of the Chironomus circumdatus larvae to find out the putative role played by the symbiotic bacteria for the host. The metabarcoding analyses of the larvae revealed that the insect harbors 1771 phylotypes. Out of the various microbial communities found, the majority corresponded to the phyla Proteobacteria (52.59%) and Actinobacteria (20.56%), respectively. The midges also harbored Klebsiella (2.57%), Enterobacter (1.32%), Bacillus (2.29%), and Acinetobacter (2.13%) genera that are involved in detoxification of xenobiotics present in the water. The presence of radiation-resistant genera like Deinococcus, including bacterial species like radiodurans, a highly radiation-resistant bacterium, indicates its potential to support the host's ability to sustain in adverse environments. The functional profiling of the bacteria showed the relative abundance of many enzyme groups, such as transferases (40.62%), oxidoreductases (23.49%), and hydrolases (3.77%). The results indicate that the larvae harbor a considerable variety of bacteria that help the host adapt and survive in the polluted waters. The present study provides thorough insights into the microbiome of the C. circumdatus larvae that can be exploited for the bioremediation of certain pollutants through biomimetic strategies. It also gives us a wake-up call to take a good look at the guts of these disease-carrying insects' inabilities to spread deadly human diseases.

Degradation of the mixed organic solvents of tributyl phosphate and n-dodecane by heterogeneous Fenton-like oxidation using nanoscale zero-valent iron as the catalyst

The treatment and disposal of spent radioactive organic solvents, i.e., tributyl phosphate (TBP) and diluent (such as kerosene, n-dodecane, etc.), produced in the reprocessing of spent fuel in the closed cycle are crucial for the sustainable development of the nuclear industry. In this study, the synthesized nanoscale zero-valent iron (nZVI) was used as the heterogeneous Fenton-like catalyst to promote the generation of hydroxyl radicals (•OH) by reacting with H₂O₂ to degrade the mixed organic solvents of TBP and n-dodecane. nZVI was characterized by scanning electron microscopy (SEM), nitrogen adsorption/desorption isotherms, and X-ray photoelectron spectroscopy (XPS) to investigate the micro-morphology, nano-particle size, and surface valence state. The change of Fe²⁺/Fe³⁺ concentration ratio during the reaction was measured to clarify the performance of nZVI. The effects of temperature, catalyst dosage, H₂O₂ dosage, and acidifier concentration on the degradation of TBP and n-dodecane were studied, and the results were complemented by the COD of the aqueous solution and the volume reduction rate of the organic phase. The mixed organic solvents of TBP and n-dodecane containing Co²⁺ were used to simulate the spent radioactive organic solvents and to study the distribution of nuclides after the reaction. The results showed that most of the radioactivity was in the residual solution, and the condensate contained almost no radioactivity. The degradation of TBP and n-dodecane was carried out separately, which showed that n-dodecane was more difficult to degrade. Density functional theory (DFT) calculations were applied to determine the adsorption energy of organic solvents and nZVI. According to the Fourier transform infrared spectra (FTIR) and their corresponding DFT calculations, liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) of the sample after the reaction, the possible intermediates were analyzed, and the degradation mechanism was speculated.

Carbamazepine at environmentally relevant concentrations caused DNA damage and apoptosis in the liver of Chinese rare minnows (Gobiocypris rarus) by the Ras/Raf/ERK/p53 signaling pathway

To assess genetoxicity and the underlying mechanisms of carbamazepine (CBZ) toxicity in fish, adult Chinese rare minnows (Gobiocypris rarus) were exposed to 1, 10, and 100 μg/L CBZ for 28 d. Comet assays indicated that hepatic DNA damage was significantly increased in groups of minnows exposed to CBZ at all concentrations in a dose-dependent manner compared to those of the control groups (p < 0.05). Liver levels of 8-hydroxydeoxyguanosine (8-OHdG) were significantly increased at 10 and 100 μg/L CBZ (p < 0.05). TUNEL assays indicated that the average apoptotic rates of the livers of female and male minnows were significantly increased following exposure to CBZ at all concentrations for 28 d (p < 0.05). Significant increases in caspase 3 and 9 activities after CBZ exposure at all concentrations and caspase 8 at 10 and 100 μg/L CBZ exposure reflected the presence of mitochondrial apoptosis (p < 0.05). The mRNA levels of gadd45a, mdm2, casp3 and casp9 in female and male minnows exposed to CBZ at all concentrations were significantly increased compared with those in the control groups (p < 0.05). Significant increases in the levels of p21 in female minnows exposed to 1 and 100 μg/L CBZ, p53 in female minnows at all CBZ treatments and bcl2 in male minnows exposed to 1 and 100 μg/L CBZ were observed, indicating p53 pathway activation. The inhibition of ras levels in females and males exposed to CBZ at all concentrations and increased levels of raf1 in males exposed to CBZ at all concentrations indicated Ras/Raf1/MAPK (ERK) activation. Therefore, the present study demonstrates that CBZ at environmentally relevant levels induces DNA damage and apoptosis in Chinese rare minnows by the Ras/Raf/ERK/p53 signaling pathway.

Comparison of the Toxicity Effects of Tris(1,3-dichloro-2-propyl)phosphate (TDCIPP) with Tributyl Phosphate (TNBP) Reveals the Mechanism of the Apoptosis Pathway in Asian Freshwater Clams (Corbicula fluminea)

To compare the toxicities of a chlorinated and a nonchlorinated organophosphorus flame retardant (OPFR) in this study, adult calms (Corbicula fluminea) were exposed to tris(1,3-dichloro-2-propyl)phosphate (TDCIPP) and tributyl phosphate (TNBP) at 20, 200, and 2000 μg/L for 30 days. Toxicity screening using transcriptomics indicated that the apoptosis pathway was significantly affected in the groups exposed to 2000 μg/L TDCIPP and TNBP (p ≤ 0.05), and this finding was further confirmed by the protein interaction network. The terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay suggested that TDCIPP and TNBP can cause apoptosis. The significant (p ≤ 0.05) increases in the activities of caspases 3 and 8 obtained with all treatments and in that of caspase 9 obtained with 2000 μg/L exposure treatments indicated the presence of mitochondria-dependent and mitochondria-independent apoptosis. Interestingly, a noticeable dose-dependent increase in DNA damage was observed in all treatments, resulting in apoptosis. Therefore, our results demonstrate that TDCIPP and TNBP induce DNA damage and apoptosis in C. fluminea, which indicates that these chemicals pose an ecological risk to benthic organisms. Moreover, through a similar mechanism of action in apoptosis, TDCIPP induced more serious toxicity than TNBP, which indicated that chlorination or differences in structure-specific metabolism could be key factors influencing toxicity.

In vitro toxicological evaluation of ionic liquids and development of effective bioremediation process for their removal

The present study deals with the cyto-genotoxicological impact of ionic liquids, 1-butyl-3-methylimidazolium bromide, trihexyl tetradecylphosphonium dicyanamide, 1-decyl-3-methylimidazolium tetrafluoroborate, benzyldimethyltetradecylammonium chloride, and 1-butyl-4-methylpyridinium chloride, on animal cells and their biodegradation. The long alkyl chain containing ionic liquids were found to be more toxic whereas benzene functional group in benzyldimethyltetradecylammonium chloride enhances its toxicity. Aerobic bacterial granules, a bacterial consortium, were developed that have promising ability to break down these organic pollutants. These aerobic bacterial granules have been applied for the biodegradation of ionic liquids. The biological oxygen demand (5 days) and chemical oxygen demand parameters confirmed that the biodegradation was solely due to aerobic bacterial granules which further decreased the time period needed for regular biodegradation by biological oxygen demand (28 days). The high resolution mass spectrometry analysis further approved that the degradation of ionic liquids was mainly via removal of the methyl group. Elevated N-demethylase enzyme activity supports the ionic liquids degradation which may be occurring through demethylation mechanism. The amplicon sequencing of aerobic bacterial granules gives insight into the involvement of the bacterial community in the biodegradation process.

Elucidating the biodegradation mechanism of tributyl phosphate (TBP) by Sphingomonas sp. isolated from TBP-contaminated mine tailings

Tributyl phosphate (TBP) is recognised as a global environmental contaminant because of its wide use in floatation reagents, nuclear fuel reprocessing and plasticisers. This contaminant is hardly degraded by hydrolysis in the environment due to its special physicochemical properties. In this study, one TBP-degrading strain was isolated from TBP-contaminated abandoned mine tailings, and 16S rRNA identification revealed that the strain belonged to the genus Sphingomonas. Results validated that the strain could utilise TBP as the sole carbon source, and vitamin was not the essential factor for its growth. Liquid chromatography time-of-flight mass spectrometry analysis identified di-n-butyl phosphate (DnBP) and mono-n-butyl phosphate (MnBP) as the intermediate metabolites for TBP biodegradation. No obvious change in carbon and hydrogen isotope composition was observed in biodegradation processes (cell suspension and crude extract degradation), which indicated that the first irreversible bond cleavage did not involve carbon or hydrogen. Hence, the TBP degradation scheme by Sphingomonas sp. proposed that the first irreversible step of TBP transferred to DnBP would lead to PO bond cleavage. This study combined the identification of products and isotope fractionation in substrates to investigate the transformation mechanism, thereby providing an eco-friendly and cost-effective way for the in situ bioremediation of TBP-contaminated sites by the isolated TBP degradation strain.

Metabolism of tri-n-butyl phosphate in earthworm Perionyx excavatus

Tri-n-butyl phosphate (TBP) is widely used in various industrial processes and has been detected in all environmental matrices. So far, little work has been done regarding the metabolism of TBP on terrestrial invertebrates. We investigated the metabolism of TBP in the earthworm, Perionyx excavatus, after acute exposure to TBP for one and two days in filter paper contact test, as well as after chronic exposure for 28 days in soil experiment. Biotransformation products were identified by using liquid chromatography coupled with quadrupole time-of-flight mass spectrometry, and by exploiting the information dependent acquisition in tandem mass spectrometry. TBP exhibited low accumulation in earthworm-soil ecosystem at 10 mg/kg and 50 mg/kg. The presence of earthworms significantly enhanced TBP degradation at 50 mg/kg in soil. Dibutyl phosphate and hydroxylated TBP were the major phase I metabolites. Three novel phase II metabolites were identified: ethanol dibutyl phosphate and its sulfate conjugate, and the phosphate conjugate of hydroxylated TBP. Hydroxylation and further phosphorylation dominated metabolism in chronic exposure. An extensive metabolic pathway of TBP in earthworm was proposed. This is the first report of TBP metabolism in terrestrial invertebrates and highlights the necessity to identify metabolites of contaminants when evaluating their bioaccumulation and toxicity.

Whole metagenome sequencing reveals links between mosquito microbiota and insecticide resistance in malaria vectors

In light of the declining global malaria burden attained largely due to insecticides, a deeper understanding of the factors driving insecticide resistance is needed to mitigate its growing threat to malaria vector control programs. Following evidence of microbiota-mediated insecticide resistance in agricultural pests, we undertook a comparative study of the microbiota in mosquitoes of differing insecticide resistance status. The microbiota of wild-caught Anopheles albimanus, an important Latin American malaria vector, that were resistant (FEN_Res) or susceptible (FEN_Sus) to the organophosphate (OP) insecticide fenitrothion were characterized and compared using whole metagenome sequencing. Results showed differing composition of the microbiota and its functions between FEN_Res and FEN_Sus, with significant enrichment of OP-degrading bacteria and enzymes in FEN_Res compared to FEN_Sus. Lower bacterial diversity was observed in FEN_Res compared to FEN_Sus, suggesting the enrichment of bacterial taxa with a competitive advantage in response to insecticide selection pressure. We report and characterize for the first time whole metagenomes of An. albimanus, revealing associations between the microbiota and phenotypic resistance to the insecticide fenitrothion. This study lays the groundwork for further investigation of the role of the mosquito microbiota in insecticide resistance.

Tributylphosphate (TBP) and tris (2-butoxyethyl) phosphate (TBEP) induced apoptosis and cell cycle arrest in HepG2 cells

The purpose of this study was to investigate the cytotoxic effects of tributylphosphate (TBP) and tris (2-butoxyethyl) phosphate (TBEP) and to explore the underlying molecular mechanism focusing on oxidative stress, apoptosis, and cell cycle arrest. The results showed that TBP and TBEP could inhibit cell proliferation, induce cellular reactive oxidative stress, and suppress the mitochondrial membrane potential in HepG2 cells. TBP and TBEP could induce both mitochondrial and p53 mediated apoptosis through different mitogen-activated protein kinase (MAPK) signal pathways. TBP activated the c-Jun N-terminal kinase (JNK) and extracellular regulated protein kinase (ERK1/2) pathways, while TBEP activated the JNK pathway. Furthermore, TBP and TBEP caused a concentration-dependent decrease of cyclin D1 expression and an increase of cyclin-dependent kinase (CDK) inhibitor proteins such as p21 and p27, resulting in significant cell cycle arrest in the G0/G1 phase. Taken together, the toxicity of TBP and TBEP on the HepG2 cells was associated with apoptosis and cell cycle arrest induced by oxidative stress.

Toxicity study of ionic liquid, 1-butyl-3-methylimidazolium bromide on guppy fish, Poecilia reticulata and its biodegradation by soil bacterium Rhodococcus hoagii VRT1

This study deals with the toxic effect of ionic liquid, 1-butyl-3-methylimidazolium bromide (BMImBr) on guppy fish, Poecilia reticulata. The fishes were exposed to various concentrations of ionic liquid for 96h. The activity of antioxidant enzymes viz. catalase, glutathione S-transferase and superoxide dismutase were found to be increased with increase in concentration. The BMImBr resistant bacterium were isolated from garden soil by enrichment method and identified as Rhodococcus hoagii VRT1 by 16S rDNA sequencing. An isolated bacterium was effective in biodegradation of compound in 8 days which was analyzed by changes in BOD and COD and later on confirmed by HRMS analysis. Higher concentrations of compound induced DNA damage in liver cells while degraded product did not show adverse impact on the DNA integrity.

Sugarcane bagasse as support for immobilization of Bacillus pumilus HZ-2 and its use in bioremediation of mesotrione-contaminated soils

The degrading microorganisms isolated from environment usually fail to degrade pollutants when used for bioremediation of contaminated soils; thus, additional treatments are needed to enhance biodegradation. In the present study, the potential of sugarcane bagasse as bacteria-immobilizing support was investigated in mesotrione biodegradation. A novel isolate Bacillus pumilus HZ-2 was applied in bacterial immobilization, which was capable of degrading over 95 % of mesotrione at initial concentrations ranging from 25 to 200 mg L(-1) within 4 days in flask-shaking tests. Scanning electron microscope (SEM) images showed that the bacterial cells were strongly absorbed and fully dispersed on bagasse surface after immobilization. Specially, 86.5 and 82.9 % of mesotrione was eliminated by bacteria immobilized on bagasse of 100 and 60 mesh, respectively, which indicated that this immobilization was able to maintain a high degrading activity of the bacteria. Analysis of the degradation products determined 2-amino-4-methylsulfonylbenzoic acid (AMBA) and 4-methylsulfonyl-2-nitrobenzoic acid (MNBA) as the main metabolites in the biodegradation pathway of mesotrione. In the sterile soil, approximately 90 % of mesotrione was degraded after supplementing 5.0 % of molasses in bacteria-bagasse composite, which greatly enhanced microbial adaptability and growth in the soil environment. In the field tests, over 75 % of mesotrione in soil was degraded within 14 days. The immobilized preparation demonstrated that mesotrione could be degraded at a wide range of pH values (5.0-8.0) and temperatures (25-35 °C), especially at low concentrations of mesotrione (5 to 20 mg kg(-1)). These results showed that sugarcane bagasse might be a good candidate as bacteria-immobilizing support to enhance mesotrione degradation by Bacillus p. HZ-2 in contaminated soils.

Effects of Simulated Rare Earth Recycling Wastewaters on Biological Nitrification

Increasing rare earth element (REE) supplies by recycling and expanded ore processing will result in generation of new wastewaters. In some cases, disposal to a sewage treatment plant may be favored, but plant performance must be maintained. To assess the potential effects of such wastewaters on biological treatment, model nitrifying organisms Nitrosomonas europaea and Nitrobacter winogradskyi were exposed to simulated wastewaters containing varying levels of yttrium or europium (10, 50, and 100 ppm), and the extractant tributyl phosphate (TBP, at 0.1 g/L). Y and Eu additions at 50 and 100 ppm inhibited N. europaea, even when virtually all of the REE was insoluble. Provision of TBP with Eu increased N. europaea inhibition, although TBP alone did not substantially alter activity. For N. winogradskyi cultures, Eu or Y additions at all tested levels induced significant inhibition, and nitrification shut down completely with TBP addition. REE solubility was calculated using the previously developed MSE (Mixed-Solvent Electrolyte) thermodynamic model. The model calculations reveal a strong pH dependence of solubility, typically controlled by the precipitation of REE hydroxides but also likely affected by the formation of unknown phosphate phases, which determined aqueous concentrations experienced by the microorganisms.

Biodegradation of tributyl phosphate, an organosphate triester, by aerobic granular biofilms

Tributyl phosphate (TBP) is commercially used in large volumes for reprocessing of spent nuclear fuel. TBP is a very stable compound and persistent in natural environments and it is not removed in conventional wastewater treatment plants. In this study, cultivation of aerobic granular biofilms in a sequencing batch reactor was investigated for efficient biodegradation of TBP. Enrichment of TBP-degrading strains resulted in efficient degradation of TBP as sole carbon or along with acetate. Complete biodegradation of 2mM of TBP was achieved within 5h with a degradation rate of 0.4 μmol mL(-1) h(-1). TBP biodegradation was accompanied by release of inorganic phosphate in stoichiometric amounts. n-Butanol, hydrolysed product of TBP was rapidly biodegraded. But, dibutyl phosphate, a putative intermediate of TBP degradation was only partially degraded pointing to an alternative degradation pathway. Phosphatase activity was 22- and 7.5-fold higher in TBP-degrading biofilms as compared to bioflocs and acetate-fed aerobic granules. Community analysis by terminal restriction length polymorphism revealed presence of 30 different bacterial strains. Seven bacterial stains, including Sphingobium sp. a known TBP degrader were isolated. The results show that aerobic granular biofilms are promising for treatment of TBP-bearing wastes or ex situ bioremediation of TBP-contaminated sites.