Microbiological aspects of the removal of chlorinated hydrocarbons from air

Dolfing, Jan; Wijngaard, Arjan J. van den; Janssen, Dick B.

doi:10.1007/bf00695974

Cited by 72 publications

(47 citation statements)

References 122 publications

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“…The doubling time on cDCE calculated from the protein data was 74 Ϯ 8 h at 20°C (data not shown). The growth rate and yield with cDCE are (8), probably due to the lower incubation temperature used in this study and the lower energy content of cDCE (4). The stoichiometry of chloride production ( Fig.…”

Section: Resultsmentioning

confidence: 85%

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Biodegradation of cis -Dichloroethene as the Sole Carbon Source by a β-Proteobacterium

Coleman

Mattes

Gossett

et al. 2002

Appl Environ Microbiol

197

152

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An aerobic bacterium capable of growth on cis-dichloroethene (cDCE) as a sole carbon and energy source was isolated by enrichment culture. The 16S ribosomal DNA sequence of the isolate (strain JS666) had 97.9% identity to the sequence from Polaromonas vacuolata, indicating that the isolate was a ␤-proteobacterium. At 20°C, strain JS666 grew on cDCE with a minimum doubling time of 73 ؎ 7 h and a growth yield of 6.1 g of protein/mol of cDCE. Chloride analysis indicated that complete dechlorination of cDCE occurred during growth. The half-velocity constant for cDCE transformation was 1.6 ؎ 0.2 M, and the maximum specific substrate utilization rate ranged from 12.6 to 16.8 nmol/min/mg of protein. Resting cells grown on cDCE could transform cDCE, ethene, vinyl chloride, trans-dichloroethene, trichloroethene, and 1,2-dichloroethane. Epoxyethane was produced from ethene by cDCE-grown cells, suggesting that an epoxidation reaction is the first step in cDCE degradation.The extensive use of chloroethenes as solvents and synthetic feedstocks has resulted in widespread environmental contamination (22), which is of concern due to the toxicity and carcinogenicity of such compounds. Microbial metabolism is an important factor in determining the fate of chloroethenes in the biosphere (14). Several anaerobic bacteria use tetrachloroethene (perchloroethene) and trichloroethene (TCE) as electron acceptors, producing cis-1,2-dichloroethene (cDCE), vinyl chloride (VC), and ethene as end products (10,15,16,17). Under aerobic conditions, ethene and VC can serve as carbon and energy sources for bacterial growth (3, 8), but thus far, no conclusive evidence exists for aerobic growth on any of the dichloroethenes (cis-dichloroethene, trans-dichloroetheneBecause cDCE accumulation is often a limiting factor in the biodegradation of chloroethenes in subsurface ecosystems, aerobic bacteria capable of growth on cDCE would provide a crucial missing link in the chain of microbial metabolism for this class of compounds. Thermodynamic calculations suggest that cDCE contains sufficient energy to support aerobic growth (4), and enzymes active on cDCE are known in hydrocarbonoxidizing bacteria (5,6,13,20,24,25). In addition, aerobic oxidation of cDCE to CO 2 has been observed in microcosm and enrichment culture studies (2, 12). Encouraged by the facts described above, we hypothesized that aerobic growth on cDCE was possible and searched at a variety of contaminated sites for microorganisms able to use this compound as a sole source of carbon and energy. MATERIALS AND METHODSChemicals and media. cis-Dichloroethene (97%), tDCE (98%), TCE (99.5%), and 1,2-dichloroethane (1,2-DCA) (99.8%) were obtained from Sigma-Aldrich. VC (99.5%) was obtained from Fluka, and ethene (99.5%) was obtained from Scott. All other chemicals were reagent grade. A minimal salts medium (MSM) based on that of Hartmans et al. (9) was used for enrichment cultures, with the following modifications: the phosphate concentration was reduced to 20 mM, the ammonium concentration was red...

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Section: Resultsmentioning

confidence: 85%

“…Thermodynamic calculations suggest that cDCE contains sufficient energy to support aerobic growth (4), and enzymes active on cDCE are known in hydrocarbonoxidizing bacteria (5,6,13,20,24,25). In addition, aerobic oxidation of cDCE to CO 2 has been observed in microcosm and enrichment culture studies (2,12).…”

mentioning

confidence: 99%

Biodegradation of cis -Dichloroethene as the Sole Carbon Source by a β-Proteobacterium

Coleman

Mattes

Gossett

et al. 2002

Appl Environ Microbiol

197

152

View full text Add to dashboard Cite

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“…The choice of sites here was based on the investigation of the active site of EchA and structural Table II (46). e Determined via gas chromatography by monitoring 1,2-epoxyhexane degradation using whole cells (5 mM initial concentration).…”

Section: Discussionmentioning

confidence: 99%

Active Site Engineering of the Epoxide Hydrolase from Agrobacterium radiobacter AD1 to Enhance Aerobic Mineralization of cis-1,2-Dichloroethylene in Cells Expressing an Evolved Toluene ortho-Monooxygenase

Rui

Chen

et al. 2004

Journal of Biological Chemistry

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Chlorinated ethenes are the most prevalent groundwater pollutants, and the toxic epoxides generated during their aerobic biodegradation limit the extent of transformation. Hydrolysis of the toxic epoxide by epoxide hydrolases represents the major biological detoxification strategy; however, chlorinated epoxyethanes are not accepted by known bacterial epoxide hydrolases. Here, the epoxide hydrolase from Agrobacterium radiobacter AD1 (EchA), which enables growth on epichlorohydrin, was tuned to accept cis-1,2-dichloroepoxyethane as a substrate by accumulating beneficial mutations from three rounds of saturation mutagenesis at three selected active site residues, Phe-108, Ile-219, and Cys-248 (no beneficial mutations were found at position Ile-111). The EchA F108L/I219L/C248I variant coexpressed with a DNA-shuffled toluene ortho-monooxygenase, which initiates attack on the chlorinated ethene, enhanced the degradation of cis-dichloroethylene (cis-DCE) an infinite extent compared with wildtype EchA at low concentrations (6.8 M) and up to 10-fold at high concentrations (540 M). EchA variants with single mutations (F108L, I219F, or C248I) enhanced cis-DCE mineralization 2.5-fold (540 M), and EchA variants with double mutations, I219L/C248I and F108L/C248I, increased cis-DCE mineralization 4-and 7-fold, respectively (540 M). For complete degradation of cis-DCE to chloride ions, the apparent V max /K m for the recombinant Escherichia coli strain expressing the EchA F108L/ I219L/C248I variant was increased over 5-fold as a result of the evolution of EchA. The EchA F108L/I219L/C248I variant also had enhanced activity for 1,2-epoxyhexane (2-fold) and the natural substrate epichlorohydrin (6-fold).

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“…For toluene oxidation, 2 ml of a concentrated cell suspension (OD 600 , 5) in Tris-HNO 3 buffer was sealed in a 15-ml serum vial, and 300 M toluene was added to the vial with a syringe, calculated as if all the substrate was in the liquid phase (the actual initial liquid concentration was 109 M based on a Henry's Law constant of 0.27 [9]). The inverted vial was shaken at room temperature at 300 rpm.…”

Section: Chemicalsmentioning

confidence: 99%

Altering Toluene 4-Monooxygenase by Active-Site Engineering for the Synthesis of 3-Methoxycatechol, Methoxyhydroquinone, and Methylhydroquinone

et al. 2004

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Wild-type toluene 4-monooxygenase (T4MO) of Pseudomonas mendocina KR1 oxidizes toluene to p-cresol (96%) and oxidizes benzene sequentially to phenol, to catechol, and to 1,2,3-trihydroxybenzene. In this study T4MO was found to oxidize o-cresol to 3-methylcatechol (91%) and methylhydroquinone (9%), to oxidize m-cresol and p-cresol to 4-methylcatechol (100%), and to oxidize o-methoxyphenol to 4-methoxyresorcinol (87%), 3-methoxycatechol (11%), and methoxyhydroquinone (2%). Apparent V max values of 6.6 ؎ 0.9 to 10.7 ؎ 0.1 nmol/min/ mg of protein were obtained for o-, m-, and p-cresol oxidation by wild-type T4MO, which are comparable to the toluene oxidation rate (15.1 ؎ 0.8 nmol/min/mg of protein). After these new reactions were discovered, saturation mutagenesis was performed near the diiron catalytic center at positions I100, G103, and A107 of the alpha subunit of the hydroxylase ( . Variant I100L produced 3-methoxycatechol from o-methoxyphenol four times faster than wild-type T4MO, and G103S/A107T produced methylhydroquinone (92%) from o-cresol fourfold faster than wild-type T4MO and there was 10 times more in terms of the percentage of the product. Variant G103S produced 40-fold more methoxyhydroquinone from o-methoxyphenol than the wild-type enzyme produced (80 versus 2%) and produced methylhydroquinone (80%) from o-cresol. Hence, the regiospecific oxidation of o-methoxyphenol and o-cresol was changed for significant synthesis of 3-methoxycatechol, methoxyhydroquinone, 3-methylcatechol, and methylhydroquinone. The enzyme variants also demonstrated altered monohydroxylation regiospecificity for toluene; for example, G103S/ A107G formed 82% o-cresol, so saturation mutagenesis converted T4MO into an ortho-hydroxylating enzyme. Furthermore, G103S/A107T formed 100% p-cresol from toluene; hence, a better para-hydroxylating enzyme than wild-type T4MO was formed. Structure homology modeling suggested that hydrogen bonding interactions of the hydroxyl groups of altered residues S103, S107, and T107 influence the regiospecificity of the oxygenase reaction.

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Microbiological aspects of the removal of chlorinated hydrocarbons from air

Cited by 72 publications

References 122 publications

Biodegradation of cis -Dichloroethene as the Sole Carbon Source by a β-Proteobacterium

Biodegradation of cis -Dichloroethene as the Sole Carbon Source by a β-Proteobacterium

Active Site Engineering of the Epoxide Hydrolase from Agrobacterium radiobacter AD1 to Enhance Aerobic Mineralization of cis-1,2-Dichloroethylene in Cells Expressing an Evolved Toluene ortho-Monooxygenase

Altering Toluene 4-Monooxygenase by Active-Site Engineering for the Synthesis of 3-Methoxycatechol, Methoxyhydroquinone, and Methylhydroquinone

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