Evidence of Enantioselective Degradation of α-Hexachlorocyclohexane in Groundwater

Law, Sheryl A.; Bidleman, Terry F.; Martin, Michael; Ruby, Michael V.

doi:10.1021/es030508c

Cited by 27 publications

(38 citation statements)

References 28 publications

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“…Preferential removal of the (+) enantiomer was detected in a mid-latitude estuary (Padma et al 2003) and the removal rate of (+)-a-HCH exceeded that of the ()) enantiomer in bench-scale studies using anoxic sewage sludge (Buser & Muller 1995). In contrast, groundwater samples from a pesticide reformulating site in Florida showed preferential degradation of the ()) enantiomer (Law et al 2004).…”

Section: Physical Properties and Persistence Of Hchsmentioning

confidence: 91%

Biodegradation of hexachlorocyclohexane (HCH) by microorganisms

Seech²,

et al. 2005

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The organochlorine pesticide Lindane is the gamma-isomer of hexachlorocyclohexane (HCH). Technical grade Lindane contains a mixture of HCH isomers which include not only gamma-HCH, but also large amounts of predominantly alpha-, beta- and delta-HCH. The physical properties and persistence of each isomer differ because of the different chlorine atom orientations on each molecule (axial or equatorial). However, all four isomers are considered toxic and recalcitrant worldwide pollutants. Biodegradation of HCH has been studied in soil, slurry and culture media but very little information exists on in situ bioremediation of the different isomers including Lindane itself, at full scale. Several soil microorganisms capable of degrading, and utilizing HCH as a carbon source, have been reported. In selected bacterial strains, the genes encoding the enzymes involved in the initial degradation of Lindane have been cloned, sequenced, expressed and the gene products characterized. HCH is biodegradable under both oxic and anoxic conditions, although mineralization is generally observed only in oxic systems. As is found for most organic compounds, HCH degradation in soil occurs at moderate temperatures and at near neutral pH. HCH biodegradation in soil has been reported at both low and high (saturated) moisture contents. Soil texture and organic matter appear to influence degradation presumably by sorption mechanisms and impact on moisture retention, bacterial growth and pH. Most studies report on the biodegradation of relatively low (< 500 mg/kg) concentrations of HCH in soil. Information on the effects of inorganic nutrients, organic carbon sources or other soil amendments is scattered and inconclusive. More in-depth assessments of amendment effects and evaluation of bioremediation protocols, on a large scale, using soil with high HCH concentrations, are needed.

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Section: Physical Properties and Persistence Of Hchsmentioning

confidence: 91%

Biodegradation of hexachlorocyclohexane (HCH) by microorganisms

Seech²,

et al. 2005

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“…Suar et al (167) were able to show that LinA1 from strain B90A preferentially dehydrochlorinates the (ϩ)-␣-HCH enantiomer, whereas LinA2 from this strain preferentially dehydrochlorinates the (Ϫ)-␣-HCH enantiomer. Different chiral preferences in the degradation of ␣-HCH enantiomers have in fact been observed for different soil samples (24,56,57,78,131).…”

Section: Variants Of Linamentioning

confidence: 95%

Biochemistry of Microbial Degradation of Hexachlorocyclohexane and Prospects for Bioremediation

Lal

Pandey

Sharma

et al. 2010

Microbiol Mol Biol Rev

350

338

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SUMMARY Lindane, the γ-isomer of hexachlorocyclohexane (HCH), is a potent insecticide. Purified lindane or unpurified mixtures of this and α-, β-, and δ-isomers of HCH were widely used as commercial insecticides in the last half of the 20th century. Large dumps of unused HCH isomers now constitute a major hazard because of their long residence times in soil and high nontarget toxicities. The major pathway for the aerobic degradation of HCH isomers in soil is the Lin pathway, and variants of this pathway will degrade all four of the HCH isomers although only slowly. Sequence differences in the primary LinA and LinB enzymes in the pathway play a key role in determining their ability to degrade the different isomers. LinA is a dehydrochlorinase, but little is known of its biochemistry. LinB is a hydrolytic dechlorinase that has been heterologously expressed and crystallized, and there is some understanding of the sequence-structure-function relationships underlying its substrate specificity and kinetics, although there are also some significant anomalies. The kinetics of some LinB variants are reported to be slow even for their preferred isomers. It is important to develop a better understanding of the biochemistries of the LinA and LinB variants and to use that knowledge to build better variants, because field trials of some bioremediation strategies based on the Lin pathway have yielded promising results but would not yet achieve economic levels of remediation.

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“…With these criteria, an EF > 0.489 or <0.483 was considered to be significantly nonracemic. 13 In the course of degradation in solutions of pH 5.0, 7.0, and 9.0, the EF values showed a much higher variation, indicating that the degradation process was enantioselective. The enantioselectivity followed the order of pH 7.0 > pH 9.0-pH 5.0, as indicated by EF (Fig.…”

Section: Enantioselectivity In Biodegradation Of Dcppmmentioning

confidence: 95%

Enantioselective separation and degradation of the herbicide dichlorprop methyl in sediment

Wen

et al. 2008

Chirality

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Chiral pesticides currently constitute about 50% of all pesticides dosage used in China, and this ratio is increasing as more complex structures are introduced. Dichlorprop methyl (DCPPM) is a chiral herbicide consisting of a pair of enantiomers. In this study, the enantiomeric separation of DCPPM was investigated by gas chromatography (GC) and high-performance liquid chromatography (HPLC) using chiral stationary phases (CSPs), and its enantiomeric degradation was characterized using a DCPPM-degrading bacterial strain isolated from an activated sludge from a textile-printing wastewater treatment plant. Baseline separation by both GC and HPLC was achieved. Incubation with DCPPM-degrading bacteria in different pH solutions showed that the R enantiomer was preferentially degraded over the S enantiomer of DCPPM. The degradation rate constant decreased with increasing pH in the order of k(pH5) approximately k(pH7) >k(pH9). In comparison, the enantioselectivity as indicated by EF followed the order of pH 7 > pH 9-pH 5.

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Evidence of Enantioselective Degradation of α-Hexachlorocyclohexane in Groundwater

Cited by 27 publications

References 28 publications

Biodegradation of hexachlorocyclohexane (HCH) by microorganisms

Biodegradation of hexachlorocyclohexane (HCH) by microorganisms

Biochemistry of Microbial Degradation of Hexachlorocyclohexane and Prospects for Bioremediation

Enantioselective separation and degradation of the herbicide dichlorprop methyl in sediment

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