Tris(2-chloroethyl) Phosphate Degradation Research Articles

Synergistic degradation of Tris (2-Chloroethyl) Phosphate (TCEP) by US/Fenton system: Experimental, DFT calculation and toxicity evaluation.

Organophosphorus esters (OPEs), exemplified by tris (2-chloroethyl) phosphate (TCEP), find extensive application in diverse industries such as construction materials, textiles, chemical manufacturing, and electronics, consequently resulting in an increased concentration of these compounds in industrial wastewater. The fundamental objective of this investigation was to examine the degradation of TCEP through the implementation of US/Fenton oxidation techniques in a solution. The findings revealed that the US/Fenton system effectively facilitated the degradation of TCEP, with the Chan kinetic model precisely elucidating the degradation process. Under optimized reaction conditions, the degradation efficiency of TCEP reached an impressive 93.18%. However, the presence of common co-existing aqueous substrates such as Cl-, HCO3-, H2PO4-, and HA hindered the degradation process. Bursting tests and electron paramagnetic resonance (EPR) studies affirmed ∙OH oxidation as the principal mechanism underlying TCEP degradation. Detailed degradation pathways for TCEP were established through the utilization of density-functional theory (DFT) calculations and GC/MS tests. Moreover, the ecotoxicological evaluation of TCEP and its intermediates was conducted using the Toxicity Estimation Software Tool (T.E.S.T.).

Thermally activated persulfate (TAP)-enhanced tris(2-chloroethyl) phosphate removal in real-world waters based on a response-surface approach as well as toxicological evaluation on its degradation products

As a typical organophosphorus flame retardant, tris(2-chloroethyl) phosphate (TCEP) is refractory in aqueous environment. The application of TAP is a promising method for removing pollutants. Herein, the removal of TCEP using TAP was rigorously investigated, and the effects of some key variables were optimized by the one-factor-at-a-time approach. To further evaluate the interactions among variables, the response surface methodology (RSM) based on central composite design was employed. Under optimized conditions (pH 5, [PS]0: [TCEP]0 = 500:1), the maximum removal efficiency (RE) of TCEP reached up to 90.6%. In real-world waters, the RE of TCEP spanned the range of 56%− 65% in river water, pond water, lake water and sanitary sewage. The low-concentration Cl- (0.1 mM) promoted TCEP degradation, but the contrary case occurred when the high-concentration Cl-, NO3-, CO32-, HCO3-, HPO42-, H2PO4-, NH4+ and humic acid were present owing to their prominently quenching effects on SO4•-. Both EPR and scavenger experiments revealed that the main radicals in the TAP system were SO4•- and •OH, in which SO4•- played the most crucial role in TCEP degradation. GC-MS/MS analysis disclosed that two degradation products appeared, sourcing from the replacement, oxidation, hydroxylation and water-molecule elimination reactions. The other two products were inferred from the comprehensive literature. As for acute toxicity to fish, daphnid and green algae, product A displayed the slightly higher toxicity, whereas other three products exhibited the declining toxicity as compared to their parent molecule. These findings offer a theoretical/practical reference for high-efficiency removal of TCEP and its ecotoxicological risk evaluation.

Dynamic processes in conjunction with microbial response to unveil the attenuation mechanisms of tris (2-chloroethyl) phosphate (TCEP) in non-sanitary landfill soils

Although the environmental and health risks of chlorinated organophosphate esters (OPEs-Cl) have drawn much attention, its environmental behaviors have been insufficiently characterized. As a notable sink of this emerging contaminant, non-sanitary landfills, which may decompose/accumulate OPEs-Cl, is of particular concern. In the present study, the dynamic processes of the typical OPEs-Cl, tris(2-chloroethyl) phosphate (TCEP), in non-sanitary landfill soils were analyzed under anaerobic condition, and the microbial taxa involved in these processes were explored. Our results showed that TCEP could be simultaneously reduced by abiotic and biotic processes, as it was reduced by 73.9% and 65.5% over the 120-day experiment in landfill humus and subsoil, respectively. Notably, the degradation of TCEP was significantly (p < 0.05) enhanced under the stress of a high TCEP concentration (10 μg g−1), while its ecological consequences were found insignificant regarding the microbial diversity and community structure and the typical soil redox processes, including Fe(III)/SO42− reduction and methanogenesis, in both soils. The microbial diversity of subsoil was significantly lower, and acetate was an important factor in changing microbial communities in landfill soils. The microbes in the family Nocardioidaceae and genus Pseudomonas might contribute to in the degradation of TCEP in landfill humus and subsoil, respectively. The metabolism related to sulfur and sulfate respiration were significantly (p < 0.05) correlated with TCEP reduction, and Desulfosporosinus were found as a potentially functional microbial taxon in TCEP degradation in both soils. The results could advance our understanding of the environmental behavior of OPEs-Cl in landfill-like complex environments.

The effects of inorganic anions on degradation kinetics and isotope fractionation during the transformation of tris(2-chloroethyl) phosphate (TCEP) by UV/persulfate

Tris(2-chloroethyl) phosphate (TCEP), as a typical chlorinated flame retardant, is attracting more attention as a carcinogen. Although persulfate-based oxidation exhibits good performance in removing refractory organic pollutants, the kinetics of persulfate-based remediation are affected by inorganic anions, which causes inaccurate remediation efficiency. This study combines steady-state radical concentration modelling with isotope fractionation to investigate the effects of inorganic anions on TCEP degradation by UV/persulfate (UV/PS). In the absence of anions during UV/PS system, the observed degradation rate was (9.7 ± 0.1) × 10−5 s−1, which was approximately 93 % attributed to sulfate radical (SO4−•) oxidation based on radical modelling. Carbon isotope fractionation, coupled with the identification of transformation products by mass spectrometry, suggests a carbon bond split during TCEP degradation with a carbon isotopic fractionation value (ε) of −1.6 ± 0.2 ‰ (± 95 % confidence intervals). With respect to co-existing anions in UV/PS system, the addition of chloride (Cl−) had a negligible effect on degradation rates, while the addition of hydrogencarbonate (HCO3−) caused them to decrease, and the addition of hydrogenphosphate (HPO42−) caused them to increase. Radical modelling suggested that SO4−• was transformed to chlorine radicals (Cl•/Cl2−•), phosphate radicals (HPO4−•), and carbonate radicals (CO3−•). Furthermore, the overlapping 95 % confidence intervals (C.I.) and the statistical tests (p > 0.05) both agree that Cl− and HPO42− gain identical ε values. Nevertheless, when HCO3− coexisted in the UV/PS system, the ε values were distinct. The addition of HCO3− would result in ε variation of TCEP in the UV activated PS process, which should receive more attention when applying remediation.

Rhizobiales as the Key Member in the Synergistic Tris (2-chloroethyl) Phosphate (TCEP) Degradation by Two Bacterial Consortia

Tris(2-chloroethyl) phosphate (TCEP) is of growing concern because of its ubiquitous occurrence, potential toxicity, and persistence in the environment. In this study, two efficient TCEP degradation consortia (AT1 and AT3) were developed and were able to completely hydrolyze TCEP within 20-25 h. Rhizobiales was identified as the key degrader in both consortia, because Rhizobiales-related phosphoesterase genes were enriched by one to two orders of magnitude when the carbon source was changed from acetate to TCEP. In addition, the increase in Rhizobiales abundance was related to the development of TCEP degradation. The isolation of Xanthobacter strains confirmed the efficient TCEP and bis(2-chloroethyl) phosphate (BCEP) degradation of Rhizobiales. The higher abundances of phosphoesterase genes affiliated with Rhizobiales genera (Bradyrhizobium and Ancylobacter), Cytophagales genus (Spirosoma), Sphingobacteriales genus (Pedobacter), and Burkholderia genus (Methylibium), may be related to the faster TCEP degradation in AT3, while the higher abundance of Rhizobiales genus (Hyphomicrobium)-related phosphodiesterase (PDE) genes may contribute to the faster BCEP degradation in AT1. The stepwise hydrolysis of TCEP was likely catalyzed by different bacterial guilds, which was confirmed by the coculture of TCEP- and BCEP-degrading isolates and highlighted the importance of synergistic interactions during TCEP degradation.

Degradation of tris(2-chloroethyl) phosphate (TCEP) by thermally activated persulfate: Combination of experimental and theoretical study

Organophosphorus esters (OPEs), one kind of the emerging contaminants with high frequency of detection, is rather refractory in natural environment, thus posing great threat to human health. This study investigated the feasibility and mechanism of tris(2-chloroethyl) phosphate (TCEP) degradation in thermally activated persulfate (TAP) system. Influence of impact factors, such as PDS dosage, temperature, initial pH, and presence of natural water matrix (Cl−, NO3−, H2PO4−, NH4+, humic acid), were evaluated. Results showed that 100% degradation of TCEP can be achieved in TAP system in 40 min at 60 °C. SO4·− as the dominant oxidant for TCEP degradation was proved by quenching experiment and verified by EPR analysis. Alkaline condition exerted great inhibitory effect by affecting the constituents of oxidative radicals. It is suggested that Cl− and H2PO4− at lower dosages promoted the degradation by stimulating ·OH production and forming oxidative radicals with better selectivity. Intermediates identified by high resolution mass spectrometer was suggested less toxic than TCEP by ECOSAR program. Meanwhile, the illustrated oxidation mechanism mainly involved radical attack at CCl bond and cleavage of CO bond, as further confirmed by frontier electron density calculation and wavefunction analysis. Moreover, cyclic degradation of TCEP indicated the constant release of SO4·− in 450 min, suggesting high efficiency and stability of PDS in TAP system. Four selected OPEs achieved complete removal in TAP system and their degradation discrepancy was further discussed based on the distinctive structures. Altogether, TAP technology can be used as an efficient method in TCEP removal with great potential for application.

Photocatalysis of Tris-(2-chloroethyl) phosphate by ultraviolet driven peroxymonosulfate oxidation process: Removal performance, energy evaluation and toxicity on bacterial metabolism network

Tris(2-chloroethyl) phosphate (TCEP) as a typical chlorinated-organophosphate esters (OPEs) are identified to be contaminants of emerging concern owing to its health risk and resistance to conventional biological remediation in water matrix. Although ultraviolet-driven radical-based advanced oxidation processes exhibited a well performance in terms of removing refractory emerging organic pollutants, residual biotoxicity and potential environment risks induced by their intermediates products have become a new concern. A comprehensive assessment regarding TCEP elimination using UV-activated peroxymonosulfate (PMS) was performed, which was attempted to provide detailed information about security and fesibility of UV/PMS technology for OPEs control. Degradation of TCEP can be described by a pseudo-first order kinetics equation with a apparent rate constant (0.1311 min−1) and three steady degradation products including C4H9Cl2O4P (m/z 222.969), C2H6ClO4P (m/z 160.976), C6H11Cl2O6P (m/z 280.974) were generated via hydroxylation and dechlorination reactions. The removal efficiency was inhibited in presence of inorganic anions (Cl−, CO32− and H2PO4−), moreover, the inhibitory effects induced by Cl− was more powerful than the other two. Compared to intact TCEP, metabolic pathways were up-regulated expression associated with carbohydrate metabolism, lipid biosynthesis, vitamin metabolism, pyrimidine and purine metabolism, whereas oxidative phosphorylation metabolism, biotin metabolism, oxidation stress response were down-regulated in Escherichia coli exposed to intermediates mixture. The proteomics results confirmed that detoxification of TCEP was achieved in case of an incomplete mineralization, and UV/PMS will be employed as a promising treatment method for controlling micro-pollutants from aquatic environment.

Degradation mechanism of tris(2-chloroethyl) phosphate (TCEP) as an emerging contaminant in advanced oxidation processes: A DFT modelling approach

As a typical toxic organophosphate and emerging contaminant, tris(2-chloroethyl) phosphate (TCEP) is resistant to conventional water treatment processes. Studies on advanced oxidation processes (AOPs) to degrade TCEP have received increasing attention, but the detailed mechanism is not yet fully understood. This study investigated the mechanistic details of TCEP degradation promoted by OH by using the density functional theory (DFT) method. Our results demonstrated that in the initial step, energy barriers of the hydrogen abstraction pathways were no more than 7 kcal/mol. Cleavage of the P–O or C–Cl bond was possible to occur, whilst the C–O or C–C cleavage had to overcome an energy barrier above 50 kcal/mol, which was too high for mild experimental conditions. The bond dissociation energy (BDE) combined with the distortion/interaction energy (DIE) analysis disclosed origin of the various reactivities of each site of TCEP. The systematic calculations on the transformation of products generated in the initial step showed remarkable exothermic property. The novel information at molecular level provides insight on how these products are generated and offers valuable theoretical guidance to help develop more effective AOPs to degrade TCEP or other emerging environmental contaminant.

Effect of pH, temperature, and use of synergistic oxidative agents on the ultrasonic degradation of tris-2-chloroethyl phosphate, gemfibrozil, and 17β estradiol in water

The degradation of three contaminants: tris-2-chloroethyl phosphate (TCEP), gemfibrozil (GEM), and 17β estradiol (E2) by ultrasonication (US) was investigated in a 0.6 L batch reactor. The effect of power intensity and temperature on degradation kinetics was quantified. The impact of oxygen (O2), hydrogen peroxide (H2O2), and sodium persulfate (Na2S2O8) on US effectiveness was assessed to determine potential synergism with US. The results illustrated that degradation of contaminants by US followed a first order rate expression and achieved their highest rate of degradation at pH 3, the lowest pH evaluated, except for TCEP which had a relatively constant rate of degradation with respect to solution pH. The maximum rate constants were achieved using US combined with Na2S2O8 and were found to be: 0.0070, 0.039, and 0.033 min–1 for degradation of TCEP, GEM, and E2, respectively. Combining US with H2O2 did not show synergism, while a small degree of synergism was observed when amending with O2. A 20% (average) decrease in the kinetic constant values was observed as the reaction temperature increased from 25°C to 55°C at pH 3. This study has provided a better understanding of the US process applied to the removal of organic contaminants from water.

Biotransformation of Tris(2-chloroethyl) Phosphate (TCEP) in Sediment Microcosms and the Adaptation of Microbial Communities to TCEP

Tris(2-chloroethyl) phosphate (TCEP), a typical chlorinated organophosphate ester (OPE), is an emerging contaminant of global concern because of its frequent occurrence, potential toxic effects, and persistence in the environment. In this study, we investigated the microbial TCEP biotransformation and the development of microbial communities in sediment microcosms with repeated TCEP amendments. The TCEP degradation fitted pseudo-zero-order kinetics, with reaction rates of 0.068 mg/(L h) after the first spike of 5 mg/L and 1.85 mg/(L h) after the second spike of 50 mg/L. TCEP was mainly degraded via phosphoester bond hydrolysis, evidenced by the production of bis(2-chloroethyl) phosphate (BCEP) and mono-chloroethyl phosphate (MCEP). Bis(2-chloroethyl) 2-hydroxyethyl phosphate (TCEP-OH), phosphoric bis(2-chloroethyl) (2-oxoethyl) ester (TCEP-CHO), phosphoric acid bis(2-chloroethyl)(carboxymethyl) ester (TCEP-COOH), and 2-chloroethyl 2-hydroxyethyl hydrogen phosphate (BCEP-OH) were also identified as microbial TCEP transformation products, indicating that TCEP degradation may follow hydrolytic dechlorination and oxidation pathways. Microbial community compositions in TCEP-amended microcosms shifted away from control microcosms after the second TCEP spike. Burkholderiales and Rhizobiales were two prevalent bacterial guilds enriched in TCEP-amended microcosms and were linked to the higher abundances of alkaline and acid phosphatase genes and genes involved in the metabolism of 2-chloroethanol, a side product of TCEP hydrolysis, indicating their importance in degrading TCEP and its metabolites.

Enhanced removal of tris(2-chloroethyl) phosphate using a resin-based nanocomposite hydrated iron oxide through a Fenton-like process: Capacity evaluation and pathways

The effective removal of organophosphorus compounds (OPs) effectively from water environment remains an important but challenging task. In this study, a resin-based nanocomposite of hydrated iron oxide (HD1) was used as Fenton-like catalyst for effectively catalyzing the decomposition of hydrogen peroxide to degrade tris(2-chloroethyl) phosphate (TCEP). The results showed that HD1 was successfully prepared, which had great versatility, catalytic performance and adsorption capacity. Besides, HD1/H2O2 was capable of degrading TCEP completely with less than 0.2 mg/L of inorganic phosphorus (IP) in the effluent at the initial TCEP of 38 mg/L, pH = 4, H2O2 dosage of 20 mM, and the Kobs could result in about 1.0530 min−1 under identical conditions. More attractively, inorganic ions (i.e., Clˉ, CO32ˉ, SO42ˉ, NO3ˉ, HCO3ˉ, Ca2+, and Mg2+) exhibited moderate effect on TCEP degradation. The negative effect of natural organic matters (NOM) (i.e., HA) on the degradation of TCEP was responsible for competition for the active oxygen species. Combined with electron paramagnetic resonance (EPR) spectra, X-ray photoelectron spectroscopy (XPS) and other analytical methods and radical quenching experiments, the possible removal process of TCEP was discussed, including two processes of oxidative degradation and immobilization of IP. Besides, hydroxyl radicals (•OH) was the key active species that contributed to TCEP degradation through hydroxylation-oxidation and C–O bond cracking, and specificity adsorption of HFO on IP was revealed. Furthermore, the results showed that HD1 had desirable acid and alkali resistance. In the continuous running fixed bed column experiment, HD1 showed a satisfactory performance in cycle operations. This work proposed a new enhanced process for removing TCEP in water environment by HD1/H2O2, and the multi-functional material, HD1 was promising in treatment of water containing organic phosphorus pollutants. This will be believed that this study will provide new ideas and new materials for the treatment of organic phosphorus-based organic pollutants, and lay the foundation for further deepening and expanding the application of adsorption resins in the field of water pollution control.

Enhanced photocatalysis using metal-organic framework MIL-101(Fe) for organophosphate degradation in water.

Metal-organic frameworks (MOFs) are attractive novel classes of porous materials with diverse potentiality and easily tailored structures. It is desirable to evaluate the performance of MOFs as photocatalysts for organic contaminant removal in aqueous matrixes. In this study, iron-based MIL-101(Fe) was synthesized and a photo-Fenton reaction system (multiple wavelength light + MIL-101(Fe) + H2O2) was developed for elimination of tris(2-chloroethyl) phosphate (TCEP). Degradation pattern of TCEP followed an S-shape curve, which included a slow induction period and a rapid radical oxidation process. Transport of reactants into MIL-101(Fe) and the activation of electron transport within Fe-O clusters of MIL-101(Fe) may be the dominant mechanisms in the induction period, while a pseudo-first-order kinetics was observed in the hydroxyl radical oxidation process. Removal efficiencies in these two stages highly depended on the reaction conditions. Irradiation at 420 nm and acid condition were conductive, while high temperature and high [H2O2]:[MIL-101(Fe)] mass ratio accelerated the reaction. Before complete mineralization, eleven degradation products were generated, and the dominant degradation pathways included cleavage, hydroxylation, carbonylation, and carboxylation. Under acid condition (pH = 3), only 1% mass loss was observed after 60-min reaction, but the iron leakage was aggravated when pH increased. Furthermore, this MOF-photo-Fenton system demonstrated a robust performance on TCEP degradation in actual wastewater matrixes under acid condition. Generally, the MOF-photo-Fenton system is a potential technology for elimination of organic pollutants in aqueous solution.

Degradation of tris(2-chloroethyl) phosphate (TCEP) in aqueous solution by using pyrite activating persulfate to produce radicals

Organophosphorus esters (OPEs), as one kind of emerging and toxic contaminant are ubiquitous in various environments. This study investigated the degradation of tris(2-chloroethyl) phosphate (TCEP) as a category OPEs by pyrite (FeS2)-activated persulfate (PS). The result shows that near-100% degradation of TCEP was achieved after 120 min in FeS2-PS system. The important role of Fe2+ in the activation mechanism was confirmed by the introduction of Fe2+ into the PS only system. Radical scavengers experiment and electron paramagnetic resonance (EPR) confirmed the presence of SO4·− and ·OH，which revealed that ·OH and SO4·− played major roles in TCEP degradation. The effect of various environmental factors, including pyrite and oxidant dosage, inorganic ions and pH were investigated. The result indicated that Fe3+ and Cl- can accelerate the degradation rate of TCEP and the reaction between TCEP and FeS2-PS favors acidic conditions (pH>9). In addition, due to the acidification of pyrite, this system can be applied with a wide pH range. Besides, two oxidation products, C4H9Cl2O4P and C2H6ClO4P were identified, which suggest that hydroxylation was probably the main mechanism. This study greatly improves our understanding on TCEP removal in FeS2-PS system.

Enhanced photocatalysis degradation of organophosphorus flame retardant using MIL-101(Fe)/persulfate: Effect of irradiation wavelength and real water matrixes

Metal-organic-frameworks (MOFs) are novel classes of porous materials with diverse potentiality and easily tailored structures. Great challenges for the applications of MOF-based heterogeneous photocatalysis still exist, such as its stability and usability for real water bodies. In this study, MIL-101(Fe) was prepared and a MOF/photo/persulfate system was used to degrade tris(2-chloroethyl) phosphate (TCEP). Synthesized MIL-101(Fe) is high-purity regular crystal with a band gap energy at 2.41 eV, indicating that short wavelength visible light (400–520 nm) and ultraviolet light (200–400 nm) can be utilized by this MOF. Mechanism of photocatalysis reaction involved activation of MIL-101(Fe) for the transformation of Fe(III) to Fe(II), which induced further transformation of S2O82− to SO4−, and then TCEP was degraded by radical oxidation. The degradation pattern demonstrated a S-shape curve with two stages, induction period and radical oxidation. The former would be a process involving reactants adsorption and photocatalyst activation, while the later mainly included SO4− and/or OH reactions. Reaction rates of these two stages highly depended on activation wavelength and pH condition. Irradiation at 420 nm and acid condition were conductive to TCEP degradation, while high temperature and S2O82− addition accelerated the reaction. Five degradation products were elucidated, and the dominant degradation pathways included cleavage, hydroxylation, carbonylation and carboxylation. Furthermore, MIL-101(Fe)/420 nm/persulfate system demonstrated a more robust performance than homogeneous ultraviolet/persulfate system for TCEP removal in real water matrixes, implying that it will be a potential technology for elimination of organic pollutants in water.

UV-driven hydroxyl radical oxidation of tris(2-chloroethyl) phosphate: Intermediate products and residual toxicity

Organophosphorus esters (OPEs) are emerging contaminants widely applied as annexing agents in a variety of industrial products, and they are robust against conventional wastewater treatments. Ultraviolet-driven (UV) radical-based advanced oxidation processes have a potential to become cost-effective treatment technologies for the removal of OPEs in water matrix, but residual and newly generated toxicities of degradation products are a concern. This study is a comprehensive attempt to evaluate UV/H2O2 for the degradation of a water dissolved OPE, tris(2-chloroethyl) phosphate (TCEP). In ultrapure water, a pseudo-first order reaction was observed, and the degradation rate constant reached 0.155 min−1 for 3.5 μM TCEP using 7.0 mW cm−2 UV irradiation with 44.0 μM H2O2. Hydroxyl radicals were involved in the oxidative degradation of TCEP, as demonstrated by the quenching of the degradation reaction in the presences of tertiary butanol or ethanol. High resolution mass spectroscopy data showed a partial transformation of TCEP to a series of hydroxylated and dechlorinated products e.g., C4H9Cl2O4P, C6H13Cl2O5P and C2H6ClO4P. Based on proteomics data at molecular and metabolic network levels, the toxicity of TCEP products was reduced obviously as the reaction proceeded, which was confirmed by the up-regulated tricarboxylic acid cycle, fatty acid metabolism and amino acid metabolism in Escherichia coli cells exposed to degradation products mixture. In conclusion, incomplete hydroxylation and dechlorination of TCEP likewise are effective for its detoxification, indicating that UV/H2O2 can be a promising treatment method for OPEs removal.

An atypical phosphodiesterase capable of degrading haloalkyl phosphate diesters from Sphingobium sp. strain TCM1

Sphingobium sp. strain TCM1 can degrade tris(2-chloroethyl) phosphate (TCEP) to inorganic phosphate and 2-chloroethanol. A phosphotriesterase (PTE), phosphodiesterase (PDE) and phosphomonoesterase (PME) are believed to be involved in the degradation of TCEP. The PTE and PME that respectively catalyze the first and third steps of TCEP degradation in TCM1 have been identified. However, no information has been reported on a PDE catalyzing the second step. In this study, we identified, purified, and characterized a PDE capable of hydrolyzing haloalkyl phosphate diesters. The final preparation of the enzyme had a specific activity of 29 µmol min−1 mg−1 with bis(p-nitrophenyl) phosphate (BpNPP) as the substrate. It also possessed low PME activity with p-nitrophenyl phosphate (pNPP) as substrate. The catalytic efficiency (kcat/Km) with BpNPP was significantly higher than that with pNPP, indicating that the enzyme prefers the organophosphorus diester to the monoester. The enzyme degraded bis(2,3-dibromopropyl) phosphate, bis(1,3-dichloro-2-propyl) phosphate and bis(2-chloroethyl) phosphate, suggesting that it is involved in the metabolism of haloalkyl organophosphorus triesters. The primary structure of the PDE from TCM1 is distinct from those of typical PDE family members and the enzyme belongs to the polymerase and histidinol phosphatase superfamily.

Complete detoxification of tris(2-chloroethyl) phosphate by two bacterial strains: Sphingobium sp. strain TCM1 and Xanthobacter autotrophicus strain GJ10

Tris(2-chloroethyl) phosphate (TCEP), a flame retardant, is recently regarded as a potentially toxic and persistent environmental contaminant. We previously isolated TCEP-degrading bacterium, Sphingobium sp. strain TCM1, which, however, produced a toxic metabolite: 2-chloroethanol (2-CE). This study was undertaken to develop a detoxification technique of TCEP using strain TCM1 with a 2-CE-degrading bacterium: Xanthobacter autotrophicus strain GJ10. TCEP degradation by strain TCM1-resting cells was thermally stable for 30 min at 30 °C. It was optimal at 30 °C and at pH 8.5. In the optimum condition, TCM1 cells up to a final cell density of 0.8 at OD(660) in the reaction mixture were unable to hydrolyze the phosphotriester bonds of 10 μM TCEP completely. The addition of 50 μM Co(2+) to reaction mixture enhanced the hydrolysis and caused the complete hydrolysis at the cell density of 0.8. Strain GJ10 resting cells degraded 2-CE only slightly, which might be attributable to lack of coenzyme regeneration of enzymes involved in the degradation. In contrast, the growing cells degraded approximately 180 μM of 2-CE within 24 h. Based on these results, we designed a two-step TCEP detoxification reaction consisting of TCEP hydrolysis to 2-CE by strain TCM1-resting cells and the following degradation of the resulting 2-CE by strain GJ10-growing cells. The combined reaction completely detoxified 10 μM TCEP, and thus opens a way to microbial detoxification of the potential toxic, persistent organophosphorus compound.