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Results for “Biodegradation, Environmental”

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At least 667 records · Page 37Linked to original sources

PubMed2001

Two-phase partitioning bioreactors: a new technology platform for destroying xenobiotics.

Toxic organic compounds (xenobiotics) pose serious environmental and health risks worldwide. Biological treatment of these materials is severely constrained by their toxic and inhibitory nature and great care is required with respect to the rate at which they are provided to cells. The use of a second, distinct, organic phase in a bioreactor has been shown to provide a virtually foolproof means of feeding substrate to cells because this process concept relies only on thermodynamic equilibrium and the cells' own rate of metabolism. This technology can be applied to stockpiled xenobiotics as well as contamination of air, water and soil environments.

Biodegradation, Environmental↗

PubMed2006

Sugarcane cellulose utilization by a defined microbial consortium.

Microorganisms isolated from diverse environmental sources were initially screened for carboxymethylcellulase activity. Nine strains that grew at elevated temperatures and which presented the highest activity were characterized further. Culture supernatants were assayed for potentiation of the enzymatic activity and, based on these results, consortia of four or nine microorganisms were tested for their capacity to grow on, and degrade a sugarcane leaf substrate. As predicted by the supernatant mixes, both consortia assayed were capable of degrading the cellulosic substrate provided. The group comprising of four strains was as efficient as the mix of all nine strains.

Bacteria↗

PubMed2004

Monitoring and evaluation of the environmental dissipation of the marine antifoulant 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) in a Danish Harbor.

The concentration of marine antifoulant 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT; the active ingredient in Sea-Nine 211 Antifouling Agent) leaching into a Danish Harbor from two painted ships was quantitated at varying distances from the ships. Sediment and suspended particulate matter were also analyzed for DCOIT. Water samples were concentrated on-site using C-18 solid phase extraction and subsequently analyzed by gas chromatography-tandem mass spectrometry. A strong decline in DCOIT water concentration as a function of distance from the ships was observed. The highest concentration (maximum 283 ng/l) was measured in the immediate vicinity of the ships and the concentration declined rapidly to less than the limit of detection (5 ng/l) at 400 m from the ships' surfaces. The measured decline curve was compared to that calculated using a one-dimensional model (ECoS). The comparison indicates that the primary mechanism of dissipation of DCOIT is not dilution resulting from dispersion but degradation with a rate constant in the order of 1 h(-1). Thus the field results correlate with the earlier microcosm studies demonstrating that DCOIT biodegrades rapidly in a marine environment.

Biodegradation, Environmental↗

PubMed2001

Photochemical transformation of acifluorfen under laboratory and natural conditions.

Acifluorfen was irradiated in pure water at various excitation wavelengths and pH values. Numerous photoproducts were obtained which were identified by [1H]NMR and/or HPLC-MS/MS. The main reaction pathways were photo-decarboxylation, photo-cleavage of the ether bonding with formation of phenolic compounds, photo-dechlorination and photo-Claisen type rearrangement. Decarboxylation was observed in acidic and neutral media whereas cleavage of the ether bonding dominated in basic media. The photo-Claisen type rearrangement only occurred on excitation at short wavelengths. The quantum yield of photolysis was significantly lower at 313 nm (6.1 x 10(-5)) than at 254 nm (2.0 x 10(-3)). The photoreactivity of acifluorfen was then studied in conditions approaching environmental conditions. Acifluorfen was dissolved in pure water, in water containing humic substances or in a natural water, and exposed to solar light in June at Clermont-Ferrand (latitude 46 degrees N). In pure water, the half-life was estimated at 10 days and photo-decarboxylation accounted for 30% of the conversion. The presence of humic substances (10 mg litre-1) did not affect the rate of photo-transformation. However, the half-life of acifluorfen dissolved in the natural water was only 6.8 days.

Biodegradation, Environmental↗

PubMed2003

Microbial destruction of cyanide wastes in gold mining: process review.

Microbial destruction of cyanide and its related compounds is one of the most important biotechnologies to emerge in the last two decades for treating process and tailings solutions at precious metals mining operations. Hundreds of plant and microbial species (bacteria, fungi and algae) can detoxify cyanide quickly to environmentally acceptable levels and into less harmful by-products. Full-scale bacterial processes have been used effectively for many years in commercial applications in North America. Several species of bacteria can convert cyanide under both aerobic and anaerobic conditions using it as a primary source of nitrogen and carbon. Other organisms are capable of oxidizing the cyanide related compounds of thiocyanate and ammonia under varying conditions of pH, temperature, nutrient levels, oxygen, and metal concentrations. This paper presents an overview of the destruction of cyanide in mining related solutions by microbial processes.

Bacteria↗

PubMed2006

Olive mill wastewater treatment: an experimental study.

Olive oil production, one of the main agro-industries in Mediterranean countries, generates significant amounts of olive mill wastewaters (OMWs), which represent a serious environmental problem, because of their high organic load, the acidic pH and the presence of recalcitrant and toxic substances such as phenolic and lipidic compounds (up to several grams per litre). In Italy, traditional disposal on the soil is the most common way to discharge OMWs. This work is aimed at investigating the efficiency and feasibility of AOPs and biological processes for OMW treatment. Trials have been carried out on wastewaters taken from one of the largest three-phase mills of Italy, located in Quarrata (Tuscany), as well as on synthetic solutions. Ozone and Fenton's reagents applied both on OMWs and on phenolic synthetic solutions guaranteed polyphenol removal efficiency up to 95%. Aerobic biological treatment was performed in a batch reactor filled with raw OMWs (pH = 4.5, T = 30 degrees C) without biomass inoculum. A biomass rich of fungi, developed after about 30 days, was able to biodegrade phenolic compounds reaching a removal efficiency of 70%. Pretreatment of OMWs by means of oxidation increased their biological treatability.

Biodegradation, Environmental↗

PubMed1989

Molecular approaches to problems in biogeochemical cycling.

By using molecular probe techniques in combination with activity and expression measurements, it is possible to estimate bacterial populations in nature. This information can be exploited to study a number of important environmental problems. For instance, it will be possible to study ecosystem perturbation and microbial competition, by altering an ecosystem or a laboratory model of an ecosystem, and assessing corresponding changes in key activities and populations. In addition, regulation of activities in the laboratory can be compared to the response of activities and populations in situ, to develop an understanding of the key parameters that control these processes in nature. These types of approaches are important steps for determining the role of microorganisms in geochemical cycling, in both specific habitats and on a global basis.

Antigens, Bacterial↗

PubMed2001

Microbial decolourisation and degradation of textile dyes.

Dyes and dyestuffs find use in a wide range of industries but are of primary importance to textile manufacturing. Wastewater from the textile industry can contain a variety of polluting substances including dyes. Increasingly, environmental legislation is being imposed to control the release of dyes, in particular azo-based compounds, into the environment. The ability of microorganisms to decolourise and metabolise dyes has long been known, and the use of bioremediation based technologies for treating textile wastewater has attracted interest. Within this review, we investigate the mechanisms by which diverse categories of microorganisms, such as the white-rot fungi and anaerobic bacterial consortia, bring about the degradation of dyestuffs.

Aerobiosis↗

PubMed2003

Vermicomposting of industrially produced woodchips and sewage sludge utilizing Eisenia fetida.

Adult Eisenia fetida were used to vermicompost woodchips (WC) and sewage sludge (SS) that are produced as waste product by platinum mines. The aims of the study were to examine the growth and reproductive success of the worms over 84 days to determine long-term feasibility of large-scale implementation and monitor the bioconcentration of heavy metals and the effects of microorganisms inoculation to quantify possible environmental implications. Results revealed that there were no effects on growth (P>0.05), reproductive success decreased (P<0.05), and aluminum (Al), copper (Cu), and nickel (Ni) were bioconcentrated (P<0.05) in the treatment groups without an inoculate. Earthworms in the treatment group with the microorganism inoculate manifested no effects on growth or reproductive success and did not accumulate Al, Cu, and Ni. It is concluded that the only economically feasible way to bioconvert WC and SS to a potential ameliorant of platinum mine tailings would be with the addition of a microorganism inoculate.

Animals↗

PubMed1989

Biological reductive dechlorination of tetrachloroethylene and trichloroethylene to ethylene under methanogenic conditions.

A biological process for remediation of groundwater contaminated with tetrachloroethylene (PCE) and trichloroethylene (TCE) can only be applied if the transformation products are environmentally acceptable. Studies with enrichment cultures of PCE- and TCE-degrading microorganisms provide evidence that, under methanogenic conditions, mixed cultures are able to completely dechlorinate PCE and TCE to ethylene, a product which is environmentally acceptable. Radiotracer studies with [14C]PCE indicated that [14C]ethylene was the terminal product; significant conversion to 14CO2 or 14CH4 was not observed. The rate-limiting step in the pathway appeared to be conversion of vinyl chloride to ethylene. To sustain reductive dechlorination of PCE and TCE, it was necessary to supply an electron donor; methanol was the most effective, although hydrogen, formate, acetate, and glucose also served. Studies with the inhibitor 2-bromoethanesulfonate suggested that methanogens played a key role in the observed biotransformations of PCE and TCE.

Alkanesulfonates↗

PubMed2006

Influence of high salinity on biofilm formation and benzoate assimilation by Pseudomonas aeruginosa.

Pseudomonas species were used in bioremediation technologies. In situ conditions, such as marine salinity, could limit the degradation of hydrocarbons and aromatic compounds by the bacteria. Biofilm ability to tolerate environmental stress could be used to increase biorestoration. In this report, we used scanning confocal laser microscopy and microtiter dish assay to analyse the impact of hyperosmotic stress on biofilm formation by Pseudomonas aeruginosa. We used benzoate as the sole carbon source and the effect of the stress on its degradation was also studied. Hyperosmotic shock inhibited the biofilm development and decreased the degradation of benzoate. The osmoprotectant glycine betaine partially restored both the biofilm formation and benzoate degradation, suggesting that it could be used as a complement in bioremediation processes.

Benzoates↗

PubMed2005

Influence of mechanical-biological waste pre-treatment methods on the gas formation in landfills.

In order to minimise emissions and environmental impacts, only pre-treated waste should be disposed of. For the last six years, a series of continuous experiments has been conducted at the Institute WAR, TU Darmstadt, in order to determine the emissions from pre-treated waste. Different kinds of pre-treated waste were incubated in several reactors and various data, including production and composition of the gas and the leachate, were collected. In this paper, the interim results of gas production and the gas composition from different types of waste after a running time of six years are presented and discussed.

Biodegradation, Environmental↗

PubMed1976

Environmental and toxicological aspects of insect growth regulators.

Insect growth regulators (IGRs) are a class of new chemicals that interfere with maturation and reproduction in insects. Proposed hypotheses on the biochemical mechanism of action are presented herein. The environmental aspects as metabolism in soils, plants, insects, and animals suggest strongly that these chemicals undergo rapid degradation and metabolism to innocuous metabolites. The toxicological properties determined for registration of the IGR methoprene, isopropyl (E,E)-11-methoxy-3,7,11-trimethyl-2,4-dodecadienoate, reflected no significant effects against any of the species tested. Toxicological evaluations in swine, sheep, hamsters, rats, dogs, rabbits, guinea pigs, and cattle revealed no clinical signs of toxicosis. Additionally, teratological studies in swine, sheep, hamsters, rats, and rabbits also resulted in no observable effects in the animals at the levels administered.

Animals↗

PubMed2001

[Decomposition processes of Tilia amurensis leaves in the Changbai Mountain forest ecosystem].

A 4-year field experiment was carried out in the Changbai Mountain to study the decomposition process of Tilia amurensis leaf and its affecting environmental factors. The results reveal that the decomposition process of Tilia amurensis leaves could be expressed by an exponent equitation. With the increase of elevation and the change of vegetation types, the decomposition rate in 1-5 standard experimental fields was -0.391, -0.339, -0.257, -0.198 and -0.125, respectively, indicating that the decomposition rate was decreased with ascending elevation. The maximum decomposition took place when the environment was in the shadow of 60%-80%. The leaves were acceleratively decomposed when the tested moisture was increased. Moisture affected the decomposition process more strongly than light.

Biodegradation, Environmental↗

PubMed2002

Prediction of uptake dynamics of persistent organic pollutants by bacteria and phytoplankton.

Phytoplankton and bacteria play an important role on the biogeochemical cycles of persistent organic pollutants (POPs). However, experimental data and quantitative knowledge of the kinetics of uptake and depuration of most POPs by bacteria and phytoplankton are scarce. In the present paper, a procedure to predict the sorption kinetics to bacteria and phytoplankton is developed. The prediction method is the combination of a mechanistic model for sorption and quantitative structure-activity relationships relating bioconcentration factors and membrane permeability to the chemical physical-chemical properties. The model consists of two compartments where the first compartment is the cellular surface and the second compartment is the cell biomass or matrix. Equations for estimating uptake and depuration rate constants into the matrix and adsorption and desorption rate constants onto the surface are obtained. These expressions depend on the physical-chemical properties of the chemical, the environmental temperature, the microorganism size, and species-specific quality of organic matter. While microorganism shape has a secondary influence on uptake dynamics, microorganism size and chemical hydrophobicity arise as the key factors controlling the kinetics of POP incorporation into bacteria and plankton. Uptake, depuration, adsorption, and desorption rate constants are reported for POPs such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated dioxins and furans (PCDD/Fs), and POPs of emerging concern, such as polybrominated diphenyl ethers (PBDEs). Finally, implications of uptake and depuration dynamics on the biogeochemical cycling of POPs are discussed.

Adsorption↗

PubMed1995

Phytoremediation: a novel strategy for the removal of toxic metals from the environment using plants.

Toxic metal pollution of waters and soils is a major environmental problem, and most conventional remediation approaches do not provide acceptable solutions. The use of specially selected and engineered metal-accumulating plants for environmental clean-up is an emerging technology called phytoremediation. Three subsets of this technology are applicable to toxic metal remediation: (1) Phytoextraction--the use of metal-accumulating plants to remove toxic metals from soil; (2) Rhizofiltration--the use of plant roots to remove toxic metals from polluted waters; and (3) Phytostabilization--the use of plants to eliminate the bioavailability of toxic metals in soils. Biological mechanisms of toxic metal uptake, translocation and resistance as well as strategies for improving phytoremediation are also discussed.

Biodegradation, Environmental↗

PubMedDate not supplied

Characterization of a diesel sludge microbial consortia for bioremediation.

The organisms found growing in a mixed diesel sludge-chromium metal waste were characterized directly using environmental scanning electron microscopy (ESEM) and traditional fixation techniques with scanning electron microscopy (SEM). An attempt to identify organisms genetically directly from the sludge failed because of interference from chemicals in the waste with polymerase chain reaction (PCR). The organisms were isolated using plate culture techniques and isolates were characterized by SEM and genetic sequencing. A variety of organisms were found with differing morphologies and growth habits. Sequencing identified an organism homologous to Bacillus mycoides and matched other organisms such as Paenibacillus lautus, Paenibacillus spp., Bacillus spp., and Rhodobacter spp.

Bacteria↗

PubMed1999

Towards the production of salt-tolerant crops.

Crop production is affected by numerous environmental factors, with soil salinity and drought having the most detrimental effects. Attempts to improve yield under stress conditions by plant breeding have been unsuccessful, primarily due to the multigenic origin of the adaptive responses. The transfer of genes through genetic engineering of crop plants appears more feasible. Important adaptive mechanisms targeted for potential gene transfer would be the tonoplast Na+/H+ antiport, compatible solute synthesis and, regulation of water channel activity and expression, mechanisms involved in cellular osmoregulation. In this review we discuss recent advances in our understanding of these adaptive mechanisms.

Aquaporins↗