Biodegradation of tert-butylphenyl diphenyl phosphate

Primary biodegradation and mineralization of aryl organophosphate flame retardants by Rhodococcus-Sphingopyxis consortium

In this study, the biodegradation towards aryl organophosphate flame retardants (aryl-OPFRs) was investigated by the Rhodococcus-Sphingopyxis consortium, mixture of strain Rhodococcus sp. YC-JH2 and Sphingopyxis sp. YC-JH3. The optimal ratio between the two composition strains was determined as 1:1. Under the optimum condition (pH 8, 35 °C and 0% salinity), the consortium could utilize aryl-OPFRs as sole carbon source and degrade them rapidly with half-life of 4.53, 21.11 and 23.0 h for triphenyl phosphate (TPhP), tricresyl phosphate (TCrP) and 2-ethylhexyl diphenyl phosphate (EHDPP) respectively. The consortium maintained high degrading efficiency under a wide of range of pH (6-10), temperature (20-40 °C) and salinity (0-6%). Besides, the consortium could rapidly degrade high concentration of TPhP and no inhibitory effect towards degradation speed was observed up to 500 mg/L. The effect of metal ions and surfactants was estimated. Most metal ions exhibited significant inhibition, except Zn²⁺ and Pb²⁺, which showed no effect or slight promotion. Ionic surfactants could severely reduce the degrading capacity, while nonionic surfactants showed no effect. With abundant inoculation of the consortium, mineralization higher than 75% could be achieved within a week. This study provides efficient microorganisms for bioremediation of aryl-OPFRs contamination.

Characterization of Individual Isopropylated and tert-Butylated Triarylphosphate (ITP and TBPP) Isomers in Several Commercial Flame Retardant Mixtures and House Dust Standard Reference Material SRM 2585

Since the phase-out of pentaBDE in the early 2000s, replacement flame-retardant mixtures including Firemaster 550 (FM 550), Firemaster 600 (FM 600), and organophosphate aryl ester technical mixtures have been increasingly used to treat polyurethane foam in residential upholstered furniture. These mixtures contain isomers of isopropylated and tert-butylated triarylphosphate esters (ITPs and TBPPs), which have similar or greater neuro- and developmental toxicity compared to BDE 47 in high-throughput assays. Additionally, human exposure to ITPs and TBPPs has been demonstrated to be widespread in several recent studies; however, the relative composition of these mixtures has remained largely uncharacterized. Using available authentic standards, the present study quantified the contribution of individual ITP and TBPP isomers in four commercial flame retardant mixtures: FM 550, FM 600, an ITP mixture, and a TBPP mixture. Findings suggest similarities between FM 550 and the ITP mixture, with 2-isopropylphenyl diphenyl phosphate (2IPPDPP), 2,4-diisopropylphenyl diphenyl phosphate (24DIPPDPP), and bis(2-isopropylphenyl) phenyl phosphate (B2IPPPP) being the most prevalent ITP isomers in both mixtures. FM 600 differed from FM 550 in that it contained TBPP isomers instead of ITP isomers. These analytes were also detected and quantified in a house dust standard reference material, SRM 2585, demonstrating their environmental relevance.

Influence of triethyl phosphate on phosphatase activity in shooting range soil: Isolation of a zinc-resistant bacterium with an acid phosphatase

Phosphatase-mediated hydrolysis of organic phosphate may be a viable means of stabilizing heavy metals via precipitation as a metal phosphate in bioremediation applications. We investigated the effect of triethyl phosphate (TEP) on soil microbial-phosphatase activity in a heavy-metal contaminated soil. Gaseous TEP has been used at subsurface sites for bioremediation of organic contaminants but not applied in heavy-metal contaminated areas. Little is known about how TEP affects microbial activity in soils and it is postulated that TEP can serve as a phosphate source in nutrient-poor groundwater and soil/sediments. Over a 3-week period, TEP amendment to microcosms containing heavy-metal contaminated soil resulted in increased activity of soil acid-phosphatase and repression of alkaline phosphatase, indicating a stimulatory effect on the microbial population. A soil-free enrichment of microorganisms adapted to heavy-metal and acidic conditions was derived from the TEP-amended soil microcosms using TEP as the sole phosphate source and the selected microbial consortium maintained a high acid-phosphatase activity with repression of alkaline phosphatase. Addition of 5mM zinc to soil-free microcosms had little effect on acid phosphatase but inhibited alkaline phosphatase. One bacterial member from the consortium, identified as Burkholderia cepacia sp., expressed an acid-phosphatase activity uninhibited by high concentrations of zinc and produced a soluble, indigo pigment under phosphate limitation. The pigment was produced in a phosphate-free medium and was not produced in the presence of TEP or phosphate ion, indicative of purple acid-phosphatase types that are pressed by bioavailable phosphate. These results demonstrate that TEP amendment was bioavailable and increased overall phosphatase activity in both soil and soil-free microcosms supporting the possibility of positive outcomes in bioremediation applications.

Composition and biodegradation of a synthetic oil spilled on the perennial ice cover of Lake Fryxell, Antarctica

A helicopter crashed in January 2003 on the 5 m-thick perennial ice cover of Lake Fryxell, spilling synthetic turbine oil Aeroshell 500. Molecular compositions of the oils were analyzed by gas chromatography-mass spectrometry and compared to the composition of contaminants in ice, meltwater, and sediments collected a year after the accident. Aeroshell 500 is based on C20-C33 Pentaerythritol triesters (PET) with C5-C10 fatty acids susbstituents and contain a number of antioxidant additives, such as tricresyl phosphates. Biodegradation of this oil in the ice cover occurs when sediments are present PETs with short fatty acids substituents are preferentially degraded, whereas long chain fatty acids seem to hinder esters from hydrolysis by esterase derived from the microbial assemblage. It remains to be seen if the microbial ecosystem can degrade tricresyl phosphates. These more recalcitrant PET species and tricresyl phosphates are likely to persist and comprise the contaminants that may eventually cross the ice cover to reach the pristine lake water.

Solid-state 13C nuclear magnetic resonance spectroscopy of simultaneously metabolized acetate and phenol in a soil Pseudomonas sp

We investigated concentration-dependent primary and secondary substrate relationships in the simultaneous metabolism of the ubiquitous pollutant phenol and the naturally occurring substrate acetate by a Pseudomonas sp. soil isolate capable of utilizing either substance as a sole source of carbon and energy. In addition to conventional analytical techniques, solid-state 13C nuclear magnetic resonance spectroscopy was used to follow the cellular distribution of [1-13C]acetate in the presence of unlabeled phenol. With 5 mM acetate as the primary substrate, Pseudomonas sp. 9S8D2 removed 1 mM phenol (secondary substrate) at a rate of 2 nmol/mg of total cell protein. Although extensive acetate metabolism was indicated by a significant redistribution of the carboxyl label, this redistribution was not affected by the presence of phenol as a secondary substrate. When the primary and secondary substrate roles were reversed, however, the presence of 1 mM phenol altered the metabolism of 0.1 mM acetate, as evidenced by both the two- to fourfold increases in carboxyl label that appeared in terminal methyl and acyl chain methylene carbon resonances and the decrease in label that occurred in the carbohydrate spectral region. These results suggest that, when phenol is present as the primary substrate, acetate is preferentially shuttled into fatty acyl chain synthesis, whereas phenol carbon is funnelled into the tricarboxylic acid cycle. Thus, simultaneous use of a xenobiotic compound and a natural substrate apparently does occur, and the relative concentrations of the two substrates do influence the rate and manner in which the compounds are utilized.(ABSTRACT TRUNCATED AT 250 WORDS)

Naphthalene biodegradation in environmental microcosms: estimates of degradation rates and characterization of metabolites

Naphthalene biodegradation was investigated in microcosms containing sediment and water collected from three ecosystems which varied in past exposure to anthropogenic and petrogenic chemicals. Mineralization half-lives for naphthalene in microcosms ranged from 2.4 weeks in sediment chronically exposed to petroleum hydrocarbons to 4.4 weeks in sediment from a pristine environment. Microbiological analysis of sediments indicated that hydrocarbon-utilizing microbial populations also varied among ecosystems and were 5 to 12 times greater in sediment after chronic petrogenic chemical exposure than in sediment from an uncontaminated ecosystem. Sediment from an ecosystem exposed to agricultural chemicals had a mineralization half-life of 3.2 weeks for naphthalene and showed about a 30-fold increase in heterotrophic bacterial populations in comparison to uncontaminated sediments, but only a 2- to 3-fold increase in hydrocarbon-degrading bacteria. Analysis of organic solvent-extractable residues from the microcosms by high-pressure liquid chromatography detected polar metabolites which accounted for 1 to 3% of the total radioactivity. Purification of these residues by thin-layer chromatography and further analysis by gas chromatography-mass spectrometry indicated that cis-1,2-dihydroxy-1,2-dihydronaphthalene, 1-naphthol, salicylic acid, and catechol were metabolites of naphthalene. These results provide useful estimates for the rates of naphthalene mineralization in different natural ecosystems and on the degradative pathway for microbial metabolism of naphthalene in freshwater and estuarine environments.