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PubMed2005

Removal of enteric bacteria in constructed treatment wetlands with emergent macrophytes: a review.

Domestic and municipal sewage contains various pathogenic or potentially pathogenic microorganisms which, depending on species concentration, pose a potential risk to human health and whose presence must therefore be reduced in the course of wastewater treatment. The removal of microbiological pollution is seldom a primary target for constructed treatment wetlands (CWs). However, wetlands are known to act as excellent biofilters through a complex of physical, chemical and biological factors which all participate in the reduction of the number of bacteria. Measurement of human pathogenic organisms in untreated and treated wastewater is expensive and technically challenging. Consequently, environmental engineers have sought indicator organisms that are (1) easy to monitor and (2) correlate with population of pathogenic organisms. The most frequently used indicators are total coliforms, fecal coliforms, fecal streptococci and Escherichia coli. The literature survey of 60 constructed wetlands with emergent vegetation around the world revealed that removal of total and fecal coliforms in constructed wetlands with emergent macrophytes is high, usually 95 to > 99% while removal of fecal streptococci is lower, usually 80-95%. Because bacterial removal efficiency is a function of inflow bacteria number, the high removal effects are achieved for untreated or mechanically pretreated wastewater. Therefore, the outflow numbers of bacteria are more important. For TC and FC the outflow concentrations are usually in the range of 10(2) to 10(5) CFU/ 100 ml while for FS the range is between 10(2) and 10(4) CFU/ 100 ml. Results from operating systems suggest that enteric microbe removal efficiency in CWs with emergent macrophytes is primarily influenced by hydraulic loading rate (HLR) and the resultant hydraulic residence time (HRT) and the presence of vegetation. Removal of enteric bacteria follows approximately a first-order relationship.

Biodegradation, Environmental↗

PubMed2003

The University of Minnesota Biocatalysis/Biodegradation Database: post-genomic data mining.

The University of Minnesota Biocatalysis/Biodegradation Database (UM-BBD, http://umbbd.ahc.umn.edu/) provides curated information on microbial catabolism and related biotransformations, primarily for environmental pollutants. Currently, it contains information on over 130 metabolic pathways, 800 reactions, 750 compounds and 500 enzymes. In the past two years, it has increased its breath to include more examples of microbial metabolism of metals and metalloids; and expanded the types of information it includes to contain microbial biotransformations of, and binding interactions with many chemical elements. It has also increased the ways in which this data can be accessed (mined). Structure-based searching was added, for exact matches, similarity, or substructures. Analysis of UM-BBD reactions has lead to a prototype, guided, pathway prediction system. Guided prediction means that the user is shown all possible biotransformations at each step and guides the process to its conclusion. Mining the UM-BBD's data provides a unique view into how the microbial world recycles organic functional groups. UM-BBD users are encouraged to comment on all aspects of the database, including the information it contains and the tools by which it can be mined. The database and prediction system develop under the direction of the scientific community.

Biodegradation, Environmental↗

PubMed1999

Environmental fate of synthetic pyrethroids during spray drift and field runoff treatments in aquatic microcosms.

The aquatic fate and persistence of synthetic pyrethroids under spray drift and field runoff treatment regimens were determined in outdoor pond microcosms. In this paper, the experimental design and construction of outdoor microcosms is presented, as well as the aquatic fate of tralomethrin and deltamethrin. Tralomethrin is rapidly degraded to deltamethrin, with a half-life of 12.7 hours under spray drift conditions. Degradation profiles of tralomethrin in water indicated rapid conversion of deltamethrin and to less active isomers and then to decamethrinic acid (BR2CA). After 24 hours, the percent radioactivity of tralomethrin was 25% of the test material in the water column. In sediment, tralomethrin was immediately converted to deltamethrin. Deltamethrin is rapidly degraded with a half-life of 8 to 48 hours, depending on mechanisms of introduction into water. Degradation profiles of deltamethrin in water indicated rapid conversion of deltamethrin to decamethrinic acid (BR2CA), comprising approximately 90% of the radioactivity in the aqueous phase at 168 hours. Extraction and analysis of fathead minnows (Pimephales promelas) after 96 hours revealed that tissue residues contained parent compounds and metabolites alpha-R-deltamethrin, trans-deltamethrin and Br2CA. Fish residues are directly related to aqueous concentrations, thus bioavailability under field runoff regimes were an order of magnitude lower than tissue residues under spray drift conditions. Plant tissue was found to significantly accumulate pyrethroids.

Animals↗

PubMed1999

Reduction of the nitrogen and carbon content in swine waste with algae and bacteria.

Animal waste causes environmental problems like eutrophication of ground and surface water or the pollution of the atmosphere because of its high NH4+ content. The aim of our study was to fix the nitrogen of swine waste as biomass. Therefore, an isolated alga, Chlorella sp., and bacteria naturally living in liquid manure were grown in batch cultures (containing diluted swine waste supplied with a nutrient solution) and continuous cultures (undiluted liquid manure) to achieve reduction of NH4+ and total organic carbon (TOC) contents. For continuous cultivation, a photobioreactor of our own design was used. The batch cultivation of Chlorella sp. and bacteria in swine waste resulted in good growth of both groups of organisms and in a reduction of 25% NH4+ and 80% TOC. In the continuous cultivation a steady state was not achieved owing to a change in the composition of the bacterial population. NH4+ was totally removed, but NO2- (up to 100 mM) was transiently released. NO3- was not detected. These effects might be explained by the presence of heterotrophic nitrifiers, which are able to oxidize NH4+ to NO2- and to reduce NO2- to gaseous compounds.

Animal Husbandry↗

PubMed2005

Dissolution and removal of PAHs from a contaminated soil using sunflower oil.

This study reports on the feasibility of remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soils using sunflower oil, an environmentally-friendly solvent. Batch experiments were performed to test the influence of oil/soil ratio on the remediation of PAH contaminated soil, and to test the mass transfer behaviors of PAHs from soil to oil. An empirical model was employed to describe the kinetics of PAH dissolution and to predict equilibrium concentrations of PAHs in oil. PAH containing oil was regenerated using active carbon. Results show that dissolution of PAHs from a Manufactured Gas Plant (MGP) soil at oil/soil ratios of one or two were almost the same. Nearly all PAHs (81-100%) could be removed by sunflower oil dissolution. Mass transfer coefficients for low molecular PAHs namely fluoranthene, phenanthrene and anthracene were one or two orders of magnitude higher than those for high molecular PAHs with 4-6 rings. Ninety milliliters of PAH containing oil could be regenerated by 10 g active carbon in a batch reactor. Such a remediation procedure indicates that sunflower oil is a promising agent for the removal of PAHs from MGP soils. However, further research is required before the method can be used for in situ remediation of contaminated sites.

Biodegradation, Environmental↗

PubMed2001

Phytoremediation potential of willow trees for aquifers contaminated with ethanol-blended gasoline.

Ethanol-blended gasoline has been used in Brazil for 20 years and, probably, is going to be more widely used in North America due to the MtBE environmental effects on groundwater. The potential impacts caused by the presence of ethanol in UST spills are related to the co-solvency effect and the preferential degradation of ethanol over the BTEX compounds. These interactions may increase the length of dissolved hydrocarbon plumes and the costs associated with site remediation. This study investigates the advantages of phytoremediation to overcome the problems associated with the presence of ethanol in groundwater contaminanted with gasoline-ethanol mixtures. Experiments were performed under lab conditions with cuttings of Willow tree (Salix babylonica) cultivated hydroponically. Results showed that the cuttings were able to reduce ethanol and benzene concentrations by more than 99% in less than a week. The uptake of both contaminants was confirmed by blank controls and was significantly related to cuttings transpiration capacity. Sorption onto roots biomass also markedly affected the behavior of contaminants in solution. Experiments to evaluate plants' toxicity to ethanol indicated that plants were only affected when aqueous ethanol concentration reached 2000mgl(-1). Results suggest that phytoremediation can be a good complement to intrinsic remediation in shallow aquifer sites contaminated with ethanol-blended gasoline spills.

Absorption↗

PubMed2003

Bioremediation of crude oil polluted soil by the white rot fungus, Pleurotus tuberregium (Fr.) Sing.

Bioremediation has become an attractive alternative to physicochemical methods of remediation of polluted sites. White rot fungi (WRF) are increasingly being investigated and used in bioremediation, because of their ability to degrade an extremely diverse range of very persistent or toxic environmental pollutants. The white rot fungus, Pleurotus tuberregium, was examined for its ability to ameliorate crude oil polluted soil. This was inferred from the ability of the polluted soil to support seed germination and seedling growth in Vigna unguiculata, at 0, 7 and 14 days post treatment. Results obtained from the present study showed that bioremediation of soil contaminated with crude oil was possible, especially when the fungus had been allowed to establish and fully colonize the substrate mixed with the soil. There were significant improvements in % germination, plant height and root elongation values of test plants, when seeds were planted 14 days post soil treatment. At 1 to 5% crude oil pollution, % germination values were comparable with the values in control plants in the 14 days treatment, and significantly higher than values obtained in the day 0 treatment. Also, at the highest level of crude oil pollution (15%), there was about 25% improvement in % germination value over the 0 day treatment. This trend of improvement in values was also observed for plant height, root elongation and biomass accumulation as well as decreased total hydrocarbon content.

Biodegradation, Environmental↗

PubMed2001

Rapid identification of Ralstonia eutropha strain CH34 using monoclonal antibodies.

Ralstonia eutropha strain CH34 (formerly Alcaligenes eutrophus CH34) is an aerobic Gram-negative and facultative chemolithotrophic bacteria with plasmid-bound resistance to heavy metals. The presence of Ralstonia eutropha strain CH34 is an indication of environmental heavy metals pollution. The major purpose of this work was to produce monoclonal antibodies (MAbs) against the metal transport outer membrane proteins. In this way, bacteria outer membranes, grown with or without iron, were purified. The electrophoretic pattern of the outer membrane revealed that, in iron starvation conditions, at least four proteins were overexpressed. These outer membranes were used to immunize mice to produce MAbs. About 200 hybridomas were tested by enzyme-linked immunoadsorbent assay (ELISA). Most of these hybridomas exhibited cross reactions with Escherichia coli and Klebsiella aerogenes. Two hybridomas, AE5/7 and AE5/9, produced MAbs that detected specifically Ralstonia eutropha strain CH34. Analysis by Western blotting showed that these MAbs recognized a protein with a molecular weight of about 41 kDa. Moreover, the presence of the two megaplasmids was required for the full expression of the 41-kDa protein, as demonstrated by screening of the derivatives strains by ELISA. These MAbs could be used for a specific and rapid detection of Ralstonia eutropha strain CH34, using direct immunological methods.

Animals↗

PubMed2006

Contamination levels and preliminary assessment of the technical feasibility of employing natural attenuation in 5 priority areas of Presidente Bernardes Refinery in Cubatão, São Paulo, Brazil.

Five priority areas of potential impact by contaminants (API) were investigated at the Presidente Bernardes Refinery in Cubatão, São Paulo, Brazil with the following aims: (i) to identify both organic and inorganic contaminants present in soil and groundwater; (ii) to define the environmental conditions relevant for microbial activity at the site and (iii) to evaluate the feasibility of employing natural attenuation for treatment of the hydrocarbon contamination. One area (API 1) was an uncontrolled landfill, where waste materials from the refinery were deposited between 1954 and 1986, and four areas (API 4, 5, 7 and 11) were located in the operational section of the refinery. Soil contamination by regulated BTEX compounds (benzene, toluene, total xylenes) was restricted to two samples from API 1. Nonregulated ethylbenzene was detected in one soil sample from API 4, one from API 5 and two from API 1. No soil contained regulated PAH above threshold levels. Several nonregulated PAHs were found in 6 soil samples from API 1, 3 soil samples from API 4 and 1 soil sample from API 5. Site soils contained very high aluminium concentrations, but metal contamination was restricted to one soil sample from API 1, which contained nickel above threshold limits. BTEX contamination of groundwater was due mostly to benzene. Of the 17 PAH molecules tested, only naphthalene and 2-methylnaphthalene occurred in groundwater. The sum of total BTEX and total PAH exceeded 200 microg/L in only a few monitoring wells in API 4, 5 and 11 and was always below 2.640 microg/L. Be, Cd, Cr, Cu, Hg, Ni, Se, Ag, Tl and Zn were not detected in groundwater, which was contaminated in a few locations by aluminium (mostly below 1 mg/L), lead (<0.066 mg/L) and arsenic (<0.056 mg/L). S, K, Ca, Mg and Fe were present in groundwater in excess of physiological requirements for microbial growth, but low concentrations of N and P could become growth limiting. However, BTEX were efficiently degraded in saturated and unsaturated zone microcosms and nutrient amendments did not stimulate biodegradation rates measurably. The inorganic carbon pool in groundwater was up to one order of magnitude larger than the organic carbon pool. Total inorganic carbon (TIC) in API groundwater exceeded TIC of clean groundwater by factors of 2 (API 4), 6 (API 5, 7 and 11) or 10 (API 1). Most of the inorganic carbon incorporated into groundwater beneath the refinery originated from biodegradation in the unsaturated soil, which contained a microbiota (10(6) cells/g on average) capable of growth with most of the pure (benzene, toluene, ethylbenzene and xylene) and mixed hydrocarbons tested (diesel oil, gasoline, naphtha, condensate, aromatic residue and fuel oil). A viscous hydrocarbon paste uncovered in API 1 was insoluble in water but dissolved in dichloromethane. Many organic components of this paste were biodegradable as evidenced by weight reduction of the hydrocarbon paste and by the growth of suspended and attached biomass in saturated zone microcosms, where the paste was the only carbon source. This study indicates that monitored natural attenuation may be a technically feasible and efficient means for plume control in API 1, 4 and 5, provided the plumes in API 4 and 5 are not expanding. This technique is not suitable for contaminant reduction in API 11.

Biodegradation, Environmental↗

PubMed2005

Identification of a homogentisate-1,2-dioxygenase gene in the fungus Exophiala lecanii-corni: analysis and implications.

Exophiala lecanii-corni is a dimorphic fungus capable of degrading several volatile organic compounds (VOCs) including ethylbenzene, which has been classified as a hazardous air pollutant by the Environmental Protection Agency. In contrast to bacterial species, little is known about the mechanisms of fungal degradation of VOCs. The results described herein suggest a potential pathway for ethylbenzene degradation in E. lecanii-corni via styrene, phenylacetate and homogentisate. Consistent with this proposed pathway, a full-length homogentisate-1,2-dioxygenase gene (ElHDO) has been identified, cloned and sequenced. The nucleotide sequence of ElHDO consists of a 1,452-bp open reading frame encoding a protein with 484 amino acids. The expression of the gene product increases when grown on ethylbenzene, further suggesting that it could be involved in ethylbenzene degradation and may be responsible for the aromatic ring cleavage reaction. In addition, a 907-bp fragment isolated upstream from this gene shares 78% sequence identity at the amino acid level with the amino acid sequences of two fungal phenylacetate hydroxylase genes. This observation suggests that the genes responsible for ethylbenzene degradation may be clustered. This research constitutes the first step towards a better understanding of ethylbenzene degradation in E. lecanii-corni.

Amino Acid Sequence↗

PubMed2005

Degradation of chlorophenols using pentachlorophenol-degrading bacteria Sphingomonas chlorophenolica in a batch reactor.

Chlorophenols are common environmental contaminants that have been used as the major component in wide-spectrum biocides in industry and agriculture. Many chlorophenols tend to persist in the environment and may become public health hazards. This research studied the ability of the pentachlorophenol (PCP)-degrading bacterium Sphingomonas chlorophenolica to degrade and dechlorinate other chlorophenols. In addition, the characteristics of S. chlorophenolica were also investigated. When S. chlorophenolica cells were preincubated with PCP, the lag phase PCP degradation periods became shorter and the PCP concentrations that could be removed became higher. S. chlorophenolica was able to completely degrade 2,3,6-trichlorophenol (2,3,6-TCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), and PCP within 38.1, 15.1, 11.8, and 11.8 h, and to release concentrations of 50.1, 60.9, 63.7, and 58.5 mg/L chloride at the same period of time. In the presence of supplementary carbon sources, the PCP removal efficiency increased with the presence of glucose or pyruvate. However, the removal efficiency of 75 mg/L 2,4-dichlorophenol did not increase with supplemental carbon sources.

Biodegradation, Environmental↗

PubMed2026

Bioprospecting Chromobacterium violaceum for bioremediation: an alternative to environmental lead pollution.

Lead pollution is a major environmental concern, but current decontamination technologies remain limited due to high costs. Therefore, alternative biotechnological processes have been successfully developed and applied due to their reduced cost and lower aggressiveness in the environment. The remarkable adaptive versatility of Chromobacterium violaceum in metal-contaminated environments makes this bacterium a promising candidate for Pb bioremediation. Therefore, the reference strain C. violaceum ATCC 12,472 and the environmental isolate C. violaceum SCV1, the first strain of this species isolated from a Brazilian area with natural Pb occurrence, were evaluated for Pb resistance under different Pb concentrations and exposure times. Pb biosorption was assessed by scanning electron microscopy, while strain-specific protein profiles were characterized using tandem mass spectrometry-based proteomic analysis. The results obtained revealed the potential of C. violaceum to perform lead bioremediation. Scanning electron microscopy analysis confirmed the biosorption of lead by C. violaceum strains. C. violaceum SCV1 was able to remove up to 40% more lead concentration when compared to ATCC 12,472 which suggested adaptation through natural selection process of C. violaceum SCV1. Proteome analysis revealed 1531 proteins, of which several are candidates for lead bioremediation. This is the first study on the resistance proteomics of C. violaceum against lead. The acclimatization of the bacteria linked to the identification of several proteins related to: biosorption; efflux and ionic uptake (bioaccumulation); biomolecule transport; and biomethylation, point out to this organism as a potential lead bioremediation agent.

Chromobacterium↗

PubMed2005

Effect of processing route and acetone pre-treatment on the biostability of pellethane materials used in medical device applications.

Thermoplastic polyurethanes, such as Pellethane 2363 80A (Pel80A) and Pellethane 2363 55D (Pel55D) are widely used in the medical device industry because of their biological and mechanical properties. However, premature failure in such devices has been observed and attributed to environmental stress cracking (ESC). The current work investigates the possibility of reducing ESC via bulk morphology manipulation. This can be achieved through various processing routes such as solvent-casting (SC) and hot-press quenching (HPQ). The effect of stress on the bulk morphology of Pel55D and Pel80A was evaluated using small-angle X-ray scattering (SAXS) in conjunction with tensile testing. SC samples exhibited greater phase separation compared with HPQ samples. Alignment of hard segment domains became apparent around the point of yield. Onset of ESC with respect to SC and HPQ routines was determined using the Zhao-Stokes glass-wool test with optical (OM) and environment scanning electron microscopy (ESEM). Improvement in biostability of Pel80A was found in HPQ samples compared to those that were SC. A secondary objective of this work was to investigate the effect of acetone pre-treatment on surface morphology. High resolution imaging of acetone treated and untreated SC Pel80A showed significant differences in surface morphology.

Acetone↗

PubMed2003

Chemical and biological regeneration of HDTMA-modified montmorillonite after sorption with phenol.

Hexadecyltrimethylammonium (HDTMA)-modified montmorillonite (HMM) has recently been recognized as a potential sorbentto remove organic contaminants from environmental systems. Potential applications of this material highly depend on the efficiency of regenerating contaminant-sorbing HMM. In this study, we investigated a chemical (NaOH solution) and a biological (yeast Pityrosporum sp.) method to regenerate phenol-sorbing HMM. Our results showed that the sorption coefficient of phenol to HMM is not a linear function of the ratio of the substitution of HDTMA in HMM. Chemical regeneration of HMMs (0-0.7 times of its cation exchange capacity (CEC)) proved the existence of a phenol residual amount of about 3 mg x g(-1) in the HMMs tested when aqueous pH is maintained above 11. In addition, the obvious deductions in the sorption capacity of the chemically regenerated HMMs were observed after four cycles of sorption-regeneration. However, the sorption capacities of intermediate substituted HMMs (0.3-0.7 CEC) can be completely restored by bioregeneration with yeast for extended cycles of reuse. The results imply that the bioregeneration method with yeast could be a promising technique for in-situ bioremediation of phenol-contaminated groundwater in the subsurface or for treatment of phenol containing wastewater.

Adsorption↗

PubMed2004

Mesophilic aerobic degradation of a metal lubricant by a biological consortium.

The metal-forming industries require the use of greases to lubricate metal surfaces during manufacturing operations, and the residues of these lubricants must be removed prior to finishing processes to protect and improve the appearance of the final product. An aqueous, biological metal-cleaning process operating under mild conditions (pH 9, 42 degrees C) eliminates the use of environmentally unfriendly cleaning materials such as chlorinated solvents by employing microorganisms to degrade greases and oils naturally. This process was characterized in terms of initial degradation rates of a representative metal lubricant and by phylogenetic identification of the active bacteria. The metal lubricant in a surfactant solution was degraded by a bacterial consortium, and its concentration was determined by a novel gas chromatography assay. The maximum degradation rate Vmax and the apparent Km were obtained as 45 mg/(day mg protein) and 24 g/l on cellular basis, and 4.6 g/(day l) and 33 g/l on a volumetric basis, respectively. Mineralization of the metal lubricant was shown by analyzing the evolved CO2 and Cl-, and the bacterial consortium utilized the metal lubricant as a sole carbon and energy source (micro=0.05+/-0.01 h(-1) at 0.5 vol% lubricant concentration). The active bacteria in the biological metal-cleaning process were identified as Bacillus licheniformis for the higher lubricant concentrations (3, 5, and 7.5 vol%), Bacillus cereus at 1 vol%, and Pseudomonas aeruginosa, Rhizobiaceae strain M100, and Achromobacter sp. LMG 5431 at 0.3 vol%.

Achromobacter↗

PubMed2005

Formation and release of non-extractable 14C-Dicamba residues in soil under sterile and non-sterile regimes.

The role of native soil microorganisms in the formation and release of non-extractable (14)C-residues, previously treated with (14)C-Dicamba, was investigated to examine their significance to the longer-term environmental effects on non-extractable pesticide residues. A 90 d study compared the fate of Dicamba under sterile and non-sterile regimes. In addition, soils were aged for 30 d and repeatedly extracted with a 0.01 M CaCl(2) solution, to an extraction end point, to produce non-extractable residues. The extracted soil containing non-extractable residues was mixed with clean soil that had been freshly spiked with non-labeled Dicamba at 0.2 mg kg(-1) to increase the bulk volume of the soil and stimulate microbial activity. Sub-samples were then introduced into microcosms to compare the extent of microbially facilitated release and mineralisation with release rates in sterile microcosms. The results show that microorganisms play a significant role in the formation and release of non-extractable Dicamba residues. The release of (14)C-activity in sterile microcosms was linked to physical mixing of the extracted soil with field soil prior to the beginning of the incubations. The released (14)C-activity may be further mineralized, reincorporated into humus, or taken up by plants or other soil inhabiting biota.

Biodegradation, Environmental↗

PubMed2002

[Influence of environmental factors on the decomposition of organic carbon in agricultural soils].

To quantitatively investigate the effects of environmental factors on organic carbon decomposition, CO2-C was measured from the incubation of wheat and rice straw as well as their roots mixed with a paddy soil over a 90-day period. Results showed that decomposition of the straw carbon was faster than that of the roots. Amount of CO2-C released from the organic matter decomposition was quantitatively related to its properties of C/N ratio. Increase of temperature within a lower temperature range enhanced greatly the decomposition while such an enhancement weakened within a higher temperature range. Under the moist condition, the temperature coefficient of organic carbon decomposition declined exponentially with the incubation time. The temperature coefficient did not significantly decrease with the time for the submerged condition after one-week incubation. The effect of water status showed that the decomposition at the water contents of 300 g.kg-1 and 500 g.kg-1 was faster than that under the treatments of 200 g.kg-1 and the submerged. Within the first month period of incubation, carbon amount released from the incubation of wheat straw was negatively related to the clay fraction of the soils.

Agriculture↗

PubMed1998

Directed evolution of new enzymes and pathways for environmental biocatalysis.

Biocatalysis is important in both natural and engineered environments. The major global reactions in the biospheric cycling of carbon, nitrogen, and other elements are catalyzed by microorganisms. The global carbon cycle includes millions of organic compounds that are made by plants, microorganisms, and organic chemists. Most of those compounds are transformed by microbial enzymes. Degradative metabolism is known as catabolism and yields principally carbon dioxide, methane, or biomass. Microbial catabolic enzymes are a great resource for biotechnology. They are the building blocks for engineering novel metabolic pathways and evolving improved enzymes in the laboratory. Two multicomponent bacterial oxygeneases, cytochrome P450cam and toluene dioxygenase, catalyze the dechlorination of polyhalogenated C2 compounds. Seven genes encoding those functional enzyme complexes were coexpressed in a Pseudomonas and shown to metabolize pentachloreothane to nonhalogenated organic acids that were metabolized further to carbon dioxide. In another example, the enzyme catalyzing the dechlorination of the herbicide atrazine was subjected to iterative DNA shuffling to produce mutations. By using a plate screening assay, mutated atrazine chlorohydrolase that catalyzed a more rapid dechlorination of atrazine was obtained. The mutant genes were sequences and found to encode up to 11 amino acid changes. Atrazine chlorohydrolase is currently being used in a model municipal water treatment system to test the feasibility of using enzymes for atrazine decontamination. These data suggest that the natural diversity of bacterial catabolic enzymes provides the starting point for improved biocatalytic systems that meet the needs of commercial applications.

Biodegradation, Environmental↗