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PubMed2004

Genes involved in aniline degradation by Delftia acidovorans strain 7N and its distribution in the natural environment.

Aniline-degraders were isolated from activated sludge and environmental samples and classified into eight phylogenetic groups. Seven groups were classified into Gram-negative bacteria, such as Acidovorax sp., Acinetobacter sp., Delftia sp., Comamonas sp., and Pseudomonas sp., suggesting the possible dominance of Gram-negative aniline-degraders in the environment. Aniline degradative genes were cloned from D. acidovorans strain 7N, and the nucleotide sequence of the 8,039-bp fragment containing eight open reading frames was determined. Their deduced amino acid sequences showed homologies to glutamine synthetase (GS)-like protein, glutamine amidotransferase (GA)-like protein, large and small subunits of aniline dioxygenase, reductase, LysR-type regulator, small ferredoxin-like protein, and catechol 2,3-dioxygenase, suggesting a high similarity of this gene cluster to those in P. putida strain UCC22 and Acinetobacter sp. strain YAA. Polymerase chain reaction (PCR) and sequencing analyses of GS-like protein gene segments of other Gram-negative bacteria suggested that Gram-negative bacteria have aniline degradative gene that can be divided into two distinctive groups.

Aniline Compounds↗

PubMed2005

Model and field studies of the degradation of cross-linked polyacrylamide gels used during the revegetation of slate waste.

Cross-linked polyacrylamide gels are increasingly being used in environmental restoration schemes and horticulture as a means of enhancing water supply to plants. However, the environmental impact of cross-linked polyacrylamide gel deployment in soil remains poorly understood. This study assessed the chemical, physical and biological properties of new and field-conditioned cross-linked polyacrylamide gels. Both monomeric acrylamide (11 microg l(-1)) and acrylic acid (285 microg l(-1)) were observed in new gel; however, the levels of monomers in field-conditioned gels (1-6 years old) were very low (acrylamide <1 microg l(-1); acrylic acid <7 microg l(-1)). Generally, freeze-thaw processes and exposure to UV radiation had little effect on gel acrylic acid and acrylamide concentrations. However, elevated temperatures (35 degrees C) caused a significant release of up to 144 mug l(-1) of acrylamide and 453 microg l(-1) of acrylic acid in new gel and up to 25 microg l(-1) of acrylamide and 157 microg l(-1) of acrylic acid in field-conditioned gels. In contrast, gel water holding capacity was highly dependent upon environmental conditions (UV exposure and freeze/thaw cycles produced the greatest loss of water holding in new gels) and gel age. Optical microscopy revealed that after placement in the field the gels became increasingly colonised over time by fungi and bacteria. In enrichment cultures, we were unable, however, to demonstrate microbial growth when cross-linked polyacrylamide was used as the sole nitrogen source. In summary, under a range of conditions cross-linked polyacrylamide did not release acrylamide above legally permitted limits, with the exception of gel subjected to elevated temperatures. However, their capacity for holding water decreased sharply within 18 months. We therefore conclude that cross-linked polyacrylamide placed in soil is relatively stable with respect to the production of potentially toxic acrylamide, a species with a short half-life, which degrades to the much less toxic acrylic acid. However, the loss of water holding capacity raises questions about its long-term effectiveness in land restoration schemes as this is the main reason it is used in this role.

Acrylic Resins↗

PubMed1996

Oil bioremediation using insoluble nitrogen source.

Oil bioremediation is limited by the availability of nitrogen and phosphorous, which are needed by the bacteria and not present in sufficient amounts in hydrocarbons. The supply of these two essential elements as water-soluble salts presents several problems. These include the rapid dilution of the salts in the large volumes of polluted land or water and their utilization by other bacteria that do not degrade oil. In addition, increasing the concentration of mobile nitrogen creates further environmental problems. The use of hydrophobic sources of nitrogen and phosphorous that have a low water solubility can overcome these problems. We have studied one such compound. F-1, that is not used by most bacteria but serves as a good nitrogen and phosphorous source for those bacterial strains that are capable of utilizing it. We have shown that bacteria using F-1 do not cross-feed other bacterial strains. Moreover, when the concentration of the pollutant is sufficiently reduced, the multiplication of the bacteria slows down until they become a negligible fraction of the bacterial population. Chemical analysis indicated that following a 28-day treatment of Alaskan crude oil, most of the hydrocarbons, including polycyclic aromatics, are degraded to undetectable levels. The C34 and C35 components were also degraded, although their degradation was not completed within this time period. In treatment of a sandy beach that was accidentally polluted with crude heavy oil, about 90% degradation was obtained within about 4 months at an outside average temperature of 5 -10 degrees C.

Biodegradation, Environmental↗

PubMed1975

Environmental factors affecting the degradation of Dyfonate by soil fungi.

The ability of selected fungi to degrade the soil insecticide Dyfonate (O-ethyl S-phenyl ethylphosphonodithioate) into water-soluble, noninsecticidal metabolites was found to be dependent on the supply of nutrients, incubation time, temperature, pH, as well as other factors. With yeast extract as the carbon source (5 g/liter) and ammonium nitrate (1 g/liter) as the nitrogen source, both Rhizopus arrhizus and Penicillium notatum degraded the insecticide to a larger extent than with any other combination of nutrients used. With glucose as the carbon source, concentrations of ammonium nitrate above 5 g/liter inhibited the degradation of Dyfonate by R. arrhizus. Time-course studies on the metabolism of the insecticide indicated that Dyfonate was first absorbed by the fungal mycelium, where it was metabolized followed by the release of water-soluble, noninsecticidal, breakdown products into the culture media. The degradation appeared to involve the breakdown of Dyfonate into ethyl acetate soluble metabolites, such as ethylethoxyphosphonothioic acid, ethylethoxyphosphonic acid, methyl phenyl sulfoxide, and methyl phenyl sulfone. These compounds were then further degraded into water-soluble products. The optimum conditions for the degradation of the insecticide by R. arrhizus were observed at pH 6.0 to 7.0 and at 15-25 degrees C. Aged fungal mycelia were as active as mycelia in the logarithmic growth phase.

Biodegradation, Environmental↗

PubMed2004

Detoxification of organophosphorus compounds by recombinant carboxylesterase from an insecticide-resistant mosquito and oxime-induced amplification of enzyme activity.

Currently, bioremediation is a promising approach to the degradation of environmental pollutants. Here we describe the application of the recombinant insecticide-resistant mosquito carboxylesterase B1 to detoxify organophosphorous compounds. However, this approach has a major limitation: 1:1 stoichiometry of the enzyme detoxification of those organophosphorous compounds containing no carboxyl ester bonds, such as paraoxon, chlorpyrifos etc. To improve the effectiveness of the enzymatic detoxification of organophosphorous compounds, we used a combination of carboxylesterase B1 with the uncharged oxime diacetylmonoxime. It was demonstrated that the repeated addition of 20 times the molar concentration of paraoxon to carboxylesterase B1 every 2 h in the presence of 4 mM diacetylmonoxime did not result in significant inhibition of the enzyme. The stoichiometry of enzyme detoxification was higher than 45:1 and 20:1 for paraoxon and chlorpyrifos, respectively. The kinetic experiments on reactivation of organophosphorus compound-inhibited carboxylesterase B1 showed that the half-life for paraoxon- and chlorpyrifos-inhibited carboxylesterase reactivation is 0.75 and 0.88 h, respectively. Using the recombinant insecticide-resistant mosquito carboxylesterase with oxime is an effective approach for detoxification of organophosphorous compounds.

Animals↗

PubMed2005

Assessment of genotoxic activity of petroleum hydrocarbon-bioremediated soil.

The relationship between toxicity and soil contamination must be understood to develop reliable indicators of environmental restoration for bioremediation. Two bacterial rapid bioassays, SOS chromotest and the umu test with and without metabolic activation (S-9 mixture), were used to evaluate the genotoxicity of petroleum hydrocarbon-contaminated soil following bioremediation treatment. The soil was taken from an engineered biopile at the Czechowice-Dziedzice Polish oil refinery (CZOR). The bioremediation process in the biopile lasted 4 years, and the toxicity measurements were done after this treatment. Carcinogens detected in the soil, polyaromatic hydrocarbons (PAHs), were reduced to low concentrations (2mg/kg dry wt) by the bioremediation process. Genotoxicity was not observed for soils tested with and without metabolic activation by a liver homogenate (S-9 mixture). However, the umu test was more sensitive than the SOS chromotest in the analysis of petroleum hydrocarbon-bioremediated soil. Analytical results of soil used in the bioassays confirmed that the bioremediation process reduced 81% of the petroleum hydrocarbons including PAHs. We conclude that the combined test systems employed in this study are useful tools for the genotoxic examination of remediated petroleum hydrocarbon-contaminated soil.

Biodegradation, Environmental↗

PubMed2003

Atrazine catabolism by a combined bacterial association (KRA30) under carbon- and nitrogen-limitations in a retentostat.

AIMS: Nutrient-limited atrazine catabolism study in continuous cultures with biomass retention to mimic in situ environmental conditions and thus gain insight of the efficacy of biosupplementation/biostimulation to eliminate reduced herbicide bioavailability. METHODS AND RESULTS: Carbon- and nitrogen-limited retentostat (1 and 5 l) cultivation of a combined atrazine (100 mg l-1)-catabolizing association KRA30 was made. As a nitrogen source, through citrate supplementation, increased herbicide catabolism resulted and was complete in the absence of NH4-N. Co-metabolism of the molecule in the presence of succinate was identified. Population characterization by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) indicated component species numerical dominance shifts in response to changes in nutrient limitation, mineral salts composition and biofilm formation, although the total species complement and catabolic potential were retained. CONCLUSIONS: Biomass and catabolic capacity maintenance, through cost-effective biosupplementation/biostimulation, should promote atrazine bioavailability and so ensure successful amelioration. SIGNIFICANCE AND IMPACT OF THE STUDY: All planning, implementation and monitoring of bioremediation programmes should be underpinned by a combination of molecular and (continuous) culture-based methods.

Atrazine↗

PubMed2004

[Study on the biological activity of activated sludge using a rapid biological activity tester].

Based on a Rapid Biological Activity Tester (RBAT), a study was taken on the sludge activity which is one of the most important parameters in the operation of aerated biological treating unit in WWTP to measure the effect of the external environmental conditions on the sludge activity, such as acidity and alkalinity, temperature, toxicity, etc. It is observed that the variety of the activity parameters is limited in 20% for a long time. While pH is deviated from the normal value, the biological activity drops to some degree, and furthermore, the ability of the microorganism to endure the acerbic environment is much higher than that to endure the alkaline environment. Temperature increase can result in the enhancement of the biological activity, and if the temperature is higher than 42.5 degrees C, the biological activity is greatly inhibite, but the endogenous respiring rate is less influenced by high temperature. Toxicity can greatly inhibit the biological activity of the activated sludge, and the inhibition is probably selective. Finally, the biological activity of the activated sludge from a real wastewater treatment plant was tested, and the standard deviation of the result is less than 20%. The results indicate that the RBAT is a promising method to measure biological activity, and the characteristics of activated sludge can be well expressed.

Biodegradation, Environmental↗

PubMed2004

Biological bleaching of chemical pulps.

Use of biotechnology in pulp bleaching has attracted considerable attention and achieved interesting results in recent years. Enzymes of the hemicellulolytic type, particularly xylan-attacking enzymes, xylanases are now used commercially in the mills for pulp treatment and subsequent incorporation into bleach sequences. The aims of the enzymatic treatment depend on the actual mill conditions and may be related to environmental demands, reduction of chemical costs or maintenance or even improvement of product quality. The use of oxidative enzymes from white-rot fungi, that can directly attack lignin, is a second-generation approach, which could produce larger chemical savings than xylanase but has not yet been developed to the full scale. It is being studied in several laboratories in Canada, Japan, the U.S.A. and Europe. Certain white-rot fungi can delignify kraft pulps increasing their brightness and their responsiveness to brightening with chemicals. The fungal treatments are too slow but the enzyme manganese peroxidase and laccase can also delignify pulps and enzymatic processes are likely to be easier to optimize and apply than the fungal treatments. Development work on laccase and manganese peroxidase continues. This article presents an overview of developments in the application of hemicellulase enzymes, lignin-oxidizing enzymes and white-rot fungi in bleaching of chemical pulps. The basic enzymology involved and the present knowledge of the mechanisms of the action of enzymes as well as the practical results and advantages obtained on the laboratory and industrial scale are discussed.

Basidiomycota↗

PubMed2003

Isolation of naphthalene-degrading bacteria from tropical marine sediments.

Oil pollution is a major environmental concern in many countries, and this has led to a concerted effort in studying the feasibility of using oil-degrading bacteria for bioremediation. Although many oil-degrading bacteria have been isolated from different environments, environmental conditions can impose a selection pressure on the types of bacteria that can reside in a particular environment. This study reports the successful isolation of two indigenous naphthalene-degrading bacteria from oil-contaminated tropical marine sediments by enrichment culture. Strains MN-005 and MN-006 were characterized using an extensive range of biochemical tests. The 16S ribosomal deoxyribonucleic acid (rDNA) sequence analysis was also performed for the two strains. Their naphthalene degradation capabilities were determined using gas chromatography and DAPI counting of bacterial cells. Strains MN-005 and MN-006 are phenotypically and phylogenetically different from each other, and belong to the genera Staphylococcus and Micrococcus, respectively. Strains MN-005 and MN-006 had maximal specific growth rates (micro(max)) of 0.082 +/- 0.008 and 0.30 +/- 0.02 per hour, respectively, and half-saturation constants (K(s)) of 0.79 +/- 0.10 and 2.52 +/- 0.32 mg per litre, respectively. These physiological and growth studies are useful in assessing the potential of these indigenous isolates for in situ or ex situ naphthalene pollutant bioremediation in tropical marine environments.

Biodegradation, Environmental↗

PubMed2001

Biological control of leachate from municipal landfills.

Landfilling is still a popular way for municipal solid waste (MSW) treatment. Leachate generated from landfills is becoming a great threat to the surroundings as it contains high concentrations of toxic substances. How to control leachate migration and to protect environmental pollution is now a concern for many environmentalists. In this work, eight effective microorganisms (EMs) were isolated from wastewater, sludge and soil samples by enrichment culturing techniques and used for leachate migration control in columns and pilot experiments. The preliminary experiments reveal that the EMs could remove 25% and 40% of chemical oxygen demand (COD) from leachate in fine sand and sabulous clay columns, respectively. An aquifer system was designed to simulate in-situ control for leachate migration with EMs. The EMs were injected into the simulated aquifer and formed a permeable biological barrier. The experimental results show that the barrier removed 95% of COD and approximately 100% inorganic nitrogen, that is, nitrate-N plus nitrite-N plus ammonia-N, from the migrating leachate. CO2 production, redox potential and microbial number were monitored simultaneously in the aquifer during the experiment to assess the EMs' activities and the effect of the bio-barrier. The data indicate that the EMs isolated in this work had high activities and were effective for organic and nitrogenous contaminant removal throughout the experiment.

Biodegradation, Environmental↗

PubMed2006

[Effects of dissolved organic matter on napropamide adsorption and transport in soil system].

Dissolved organic matter (DOM) can affect the environmental behaviors of herbicides in soil. Batch adsorption and column experiments were conducted to measure the sorption and leaching of napropamide in soils in the presence of DOM derived from green manure (GM) and sewage sludge (SS). DOM reduced sorption of napropamide significantly onto the tested soils, consequently which facilitated the transport of napropamide exhibited by soil column experiment. The sorption inhibition and the increased mobility of napropamide caused by DOM of GM origin were more significant than that of SS origin for the same soil. Within the selected concentration range of the napropamide and DOM in this study napropamide sorption isotherm could be described well by the Freundlich equation. In comparison with the control, DOM of GM and SS origins could reduce napropamide adsorption by 22.9% and 11.3% in the yellow-brown soil and 9.5% and 6.5% in the calcareous soil, respectively. Correspondingly, in the presence of DOM the leaching losses of napropamide in soil column increased by 73.42% and 26.87% in the yellow-brown soil and 43.54% and 28.29% in the calcareous soil, respectively.

Adsorption↗

PubMed2006

Dynamic transformations of nitrogen during mechanical-biological pre-treatment of municipal solid waste.

Mechanical-biological pre-treatment (MBP) of municipal solid waste (MSW) has gained evidence as a practice capable of accomplishing the requirements for environmental sustainable landfilling. In particular, MBP is effective in reducing the ammoniacal nitrogen content in the leachate. However, few data are available on the modifications of the nitrogen forms occurring during MBP and on the role played by processes such as nitrification and generation of refractory organic compounds. The dynamic transformations of nitrogen were investigated during the MBP. MSW was mechanically and biologically pre-treated; samples were collected at different stages of the process and analysed to investigate the evolution of nitrogen forms; batch and column leaching tests were performed as well. The results indicate that nitrification is negligible and volatilization can only partially explain the low ammoniacal nitrogen content in the leachate. Incorporation of ammoniacal nitrogen into a refractory organic form was assessed and is likely to play an important role. The maximum content of refractory organic nitrogen in the solid waste was achieved after about 60 days of aerobic pre-treatment; therefore, the minimal duration of the MBP should be about 8-9 weeks in order to optimize the ammoniacal nitrogen incorporation, unless the waste is characterized by a low C/N ratio.

Ammonia↗

PubMed2001

Use of green fluorescent protein and luciferase biomarkers to monitor survival and activity of Arthrobacter chlorophenolicus A6 cells during degradation of 4-chlorophenol in soil.

The recently isolated novel species Arthrobacter chlorophenolicus A6 is capable of growth on and degradation of high concentrations of 4-chlorophenol (up to 350 microg ml(-1)) as the sole carbon and energy source. This strain shows promise for bioremediation of environmental sites contaminated with high levels of chlorophenols. In this study, green fluorescent protein (gfp) or luciferase (luc) genes were used as biomarkers for monitoring cell number and activity, respectively, during degradation of 4-chlorophenol by A. chlorophenolicus cells. The individual marked strains, Arthrobacter chlorophenolicus A6L (luc-tagged) and Arthrobacter chlorophenolicus A6G (gfp-tagged), were monitored during degradation of 250 microg ml(-1) 4-chlorophenol in pure culture and 175 microg g(-1) 4-chlorophenol in soil microcosms. Both gene-tagged strains were capable of cleaning up the contaminated soil during 9 d incubation. During the bioremediation experiments, the luc-tagged cells were monitored using luminometry and the gfp-tagged cells using flow cytometry, in addition to selective plate counting for both strains. The cells remained at high population levels in the soil (evidenced by GFP-fluorescent cell counts) and the A. chlorophenolicus A6L population was metabolically active (evidenced by luciferase activity measurements). These results demonstrate that the Arthrobacter chlorophenolicus A6 inoculum is effective for cleaning-up soil containing high concentrations of 4-chlorophenol.

Arthrobacter↗

PubMed1997

A bacterial basic region leucine zipper histidine kinase regulating toluene degradation.

The two-component signal transduction pathways in bacteria use a histidine-aspartate phosphorelay circuit to mediate cellular changes in response to environmental stimuli. Here we describe a novel two-component todST system, which activates expression of the toluene degradation (tod) pathway in Pseudomonas putida F1. The todS gene is predicted to encode a sensory hybrid kinase with two unique properties--a basic region leucine zipper dimerization motif at the N terminus and a duplicated histidine kinase motif. Evidence from a synthetic peptide model suggests that TodS binds as a dimer to a pseudopalindromic sequence (5'-TGACTCA), which resembles the recognition sequence of the eukaryotic transcription factors Fos and Jun. These results provide additional evidence that bacteria and eukaryotes share common regulatory motifs. The todT gene product, a response regulator, was overproduced as a fusion protein in Escherichia coli, and the purified protein was found to bind specifically to a 6-bp palindromic DNA structure in the tod control region. The phosphorylated form of TodT appears to be the activator of tod structural genes. This is the first report of a two-component system that regulates aromatic metabolism in bacteria.

Amino Acid Sequence↗

PubMed2003

Metabolism of the soil and groundwater contaminants, ethylene dibromide and trichloroethylene, by the tropical leguminous tree, Leuceana leucocephala.

Ethylene dibromide (EDB; dibromoethane) and trichloroethylene (TCE) are hazardous environmental pollutants. The use of plants to treat polluted sites and groundwater, termed phytoremediation, requires plants that can both effectively remove the pollutant as well as grow in the climatic region of the site. In this paper, we report that the tropical leguminous tree, Leuceana leucocephala var. K636, is able to take up and metabolize EDB and TCE. The plants were grown in sterile hydroponic solution without its symbiont, Rhizobium. EDB and TCE were both metabolized by the plant, as indicated by the formation of bromide ion from EDB and trichloroethanol from TCE. Each plant organ was independently capable of debromination of EDB. L. leucocephala is being used to treat perched groundwater as part of a remedial alternative to address an accidental EDB spill in Hawaii. Bromide levels of plant tissues from the trees grown in the phytoremediation treatment cells at the Hawaii Site were elevated, indicating uptake and degradation of brominated compounds in the trees. This report is the first evidence of a tropical tree effectively metabolizing these common organic pollutants.

Biodegradation, Environmental↗

PubMed2004

[Properties of Pesudomonas sp. DN-1 in reduction of nitric oxide chelate absorption solution].

Metal chelate absorption is deemed as a promising method of NO removal in FGD system, but the difficulty in the regeneration of the absorption solution hinders its further development. An original method with microbial reduction is proposed in this paper. With the adding of Psudomonas sp. DN-1, which was newly isolated from wastewater treatment plant, FeII (EDTA) NO will be reduced to the environmentally benign gaseous product of N2, and thus FeII (EDTA) was regenerated simultaneously. The effects of the types and amount of carbon source, FeII (EDTA) NO concentration, pH, temperature and the biomass inoculation on bio-reduction efficiency were investigated. The results showed that the microorganism exhibited good performance on bio-reduction of FeII (EDTA) NO with the carbon sources of glucose. 250 mg x L(-1) glucose was enough for microorganism to reduce 6.50 mmol x L(-1) FeII (EDTA) NO completely. The rate of FeII (EDTA) NO reduction did not increase with adding a larger amount of carbon source. The bio-reduction could be achieved efficiently among the temperature range of 40 - 45 degrees C and a pH range of 6.9 - 7.2. The bio-reduction rate increased with the increasing of biomass inoculation. When FeII (EDTA) NO concentration is less than 11.8 mmol x L(-1), the reduction rate increased as the concentration increases, while the concentration is over 11.8 mmol x L(-1), the reduction rate keeps constant.

Absorption↗

PubMed2004

Enhanced accumulation of phosphate by Lolium multiflorum cultivars grown in phosphate-enriched medium.

Agricultural and animal husbandry practices combined with soil composition have caused phosphate overloading of farmlands in different parts of the U.S. and Europe. Movement of soluble phosphates (Pi) from phosphorus enriched soils results in degradation of natural aquatic systems, triggering serious environmental problems. Remediation of such sites using plants that tolerate and accumulate high concentrations of Pi in their aerial parts may be an attractive remediation technology. In the present study, Pi transport and accumulation potential of Marshall and Gulf ryegrass (Lolium multiflorum cultivars) were determined using a solution culture of seedlings. Ryegrass seedlings accumulated phosphorus (P) in excess of 2% of dry weight in their aerial parts when supplied with 5 g/L KH2PO4 in medium. Phosphorus accumulation was positively correlated with the concentration of phosphate (0-5 g/L KH2PO4) in medium. Plants grew well on medium containing 5 g/L KH2PO4, but concentrations above 5 g/L caused symptoms of toxicity. Scanning electron microscopy and energy-dispersive X-ray spectroscopy confirmed high P accumulation in different cell types of grass roots and shoots. Phosphate starvation and replenishment experiments point to the unique ability of these grasses to concentrate phosphate in the above-ground parts. It is hypothesized that the unique ability of these ryegrass cultivars may be due to the presence of efficient phosphate transport and sequestration mechanisms.

Agriculture↗