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At least 73 records · Page 4Linked to original sources
PubMed2003

Environmental impact of highway construction and repair materials on surface and ground waters. Case study: crumb rubber asphalt concrete.

The practice of incorporating certain waste products into highway construction and repair materials (CRMs) has become more popular. These practices have prompted the National Academy of Science, National Cooperative Highway Research Program (NCHRP) to research the possible impacts of these CRMs on the quality of surface and ground waters. State department of transportations (DOTs) are currently experimenting with use of ground tire rubber ( crumb rubber) in bituminous construction and as a crack sealer. Crumb rubber asphalt concrete (CR-AC) leachates contain a mixture of organic and metallic contaminants. Benzothiazole and 2(3H)-benzothiazolone (organic compounds used in tire rubber manufacturing) and the metals mercury and aluminum were leached in potentially harmful concentrations (exceeding toxic concentrations for aquatic toxicity tests). CR-AC leachate exhibited moderate to high toxicity for algae ( Selenastrum capriconutum) and moderate toxicity for water fleas ( Daphnia magna). Benzothiazole was readily removed from CR-AC leachate by the environmental processes of soil sorption, volatilization, and biodegradation. Metals, which do not volatilize or photochemically or biologically degrade, were removed from the leachate by soil sorption. Contaminants from CR-AC leachates are thus degraded or retarded in their transport through nearby soils and ground waters.

Animals↗
PubMed1996

Regulatory noise in prokaryotic promoters: how bacteria learn to respond to novel environmental signals.

Various features of the regulation of pathways for biodegradation of recalcitrant compounds by Pseudomonas provide insights into the mechanisms by which operons evolve to acquire conditionally active promoters that permit the corresponding genes to be transcribed only when required. The "regulatory noise hypothesis' proposes that transcriptional control systems develop responsiveness to new signals due to the leakiness and lack of specificity of preexisting promoters and regulators. When needed, these may become more specific through suppression of undesirable signals and further fine-tuning of the recruited proteins to interact with distinct chemicals. This hypothesis is supported by the sophisticated regulation of sigma 54-dependent promoters of the TOL (toluene biodegradation) operons, which can be activated to various degrees by heterologous proteins. Such "illegitimate' activation is suppressed by bent DNA structures, either static or protein induced, between promoter core elements. Therefore, not only the regulators but also the DNA sequences participate in the process that gives rise to novel specificities.

Biodegradation, Environmental↗
PubMed1992

Biostability of a non-ether polyurethane.

A new type of medical grade polyurethane elastomer, based upon an ether-free macroglycol, has been developed by VASCOR, Inc. Prior research conducted by others has indicated that an ether-free urethane should be inherently immune to biodegradation and environmental stress cracking. Specimens of the experimental polyurethane, along with positive and negative control materials, were formed into tubing, mounted on mandrels, and implanted in rabbits. After being exposed to the in vivo environment for six months, the specimens were explanted and examined with scanning electron microscopy. No indication of degradation was observed in the experimental polymer or negative control specimens, whereas severe microcracking was seen in most of the positive control specimens.

Animals↗
PubMed2003

The organization of the microbial biodegradation network from a systems-biology perspective.

Microbial biodegradation of environmental pollutants is a field of growing importance because of its potential use in bioremediation and biocatalysis. We have studied the characteristics of the global biodegradation network that is brought about by all the known chemical reactions that are implicated in this process, regardless of their microbial hosts. This combination produces an efficient and integrated suprametabolism, with properties similar to those that define metabolic networks in single organisms. The characteristics of this network support an evolutionary scenario in which the reactions evolved outwards from the central metabolism. The properties of the global biodegradation network have implications for predicting the fate of current and future environmental pollutants.

Bacteria↗
PubMedDate not supplied

19F NMR metabolomics for the elucidation of microbial degradation pathways of fluorophenols.

Of all NMR-observable isotopes 19F is the one most convenient for studies on the biodegradation of environmental pollutants and especially for fast initial metabolic screening of newly isolated organisms. In the past decade we have identified the 19F NMR characteristics of many fluorinated intermediates in the microbial degradation of fluoroaromatics including especially fluorophenols. In the present paper we give an overview of results obtained for the initial steps in the aerobic microbial degradation of fluorophenols, i.e. the aromatic hydroxylation to di -, tri - or even tetrahydroxybenzenes ultimately suitable as substrates for the second step, ring cleavage by dioxygenases. In addition we present new results from studies on the identification of metabolites resulting from reaction steps following aromatic ring cleavage, i.e. resulting from the conversion of fluoromuconates by chloromuconate cycloisomerase. Together the presented data illustrate the potential of the 19F NMR technique for (1) fast initial screening of biodegradative pathways, i.e. for studies on metabolomics in newly isolated microorganisms, and (2) identification of relatively unstable pathway intermediates like fluoromuconolactones and fluoromaleylacetates.

Biodegradation, Environmental↗
PubMed2003

Induced phytoextraction/soil washing of lead using biodegradable chelate and permeable barriers.

Chelate-induced remediation has been proposed as an effective tool for the extraction of lead (Pb) from contaminated soils by plants. However, side-effects, mainly mobilization and leaching of Pb, raise environmental concerns. Biodegradable, synthetic organic chelate ethylenediaminedisuccinic acid (EDDS), and commonly used ethylenedimanetetraacetic acid (EDTA) were used for induced phytoextraction with a test plant Brassica rapa and in situ washing of soil contaminated with 1350 mg/kg of Pb. Horizontal permeable barriers were placed 20 cm deep in soil columns and tested for their ability to prevent leaching of Pb. The reactive materials in the barriers were nutrient enriched vermiculite, peat or agricultural hydrogel, and apatite. EDTA and EDDS addition increased Pb concentrations in the test plant by 158 and 89 times compared to the control, to 817 and 464 mg/kg, respectively. In EDTA treatments, approximately 25% or more of total initial soil Pb was leached in single cycle of chelate addition. In EDDS treatments, 20% of the initial Pb was leached from columns with no barrier, while barriers with vermiculite or hydrogel and apatite decreased leaching by more than 60 times, to 0.35%. 11.6% of total initial Pb was washed from the soil above the barrier with vermiculite and apatite, where almost all leached Pb was accumulated. Results indicate that use of biodegradable chelate EDDS and permeable barriers may lead to environmentally safe induced Pb phytoextraction and in situ washing of Pb.

Aluminum Silicates↗
PubMed1996

Biodegradation of atrazine in surface soils and subsurface sediments collected from an agricultural research farm.

The purpose of the present study was to assess atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) mineralization by indigenous microbial communities and to investigate constraints associated with atrazine biodegradation in environmental samples collected from surface soil and subsurface zones at an agricultural site in Ohio. Atrazine mineralization in soil and sediment samples was monitored as 14CO2 evolution in biometers which were amended with 14C-labeled atrazine. Variables of interest were the position of the label ([U-14C-ring]-atrazine and [2-14C-ethyl]-atrazine), incubation temperature (25 degrees C and 10 degrees C), inoculation with a previously characterized atrazine-mineralizing bacterial isolate (M91-3), and the effect of sterilization prior to inoculation. In uninoculated biometers, mineralization rate constants declined with increasing sample depth. First-order mineralization rate constants were somewhat lower for [2-14C-ethyl]-atrazine when compared to those of [U-14C-ring]-atrazine. Moreover, the total amount of 14CO2 released was less with [2-14C-ethyl]-atrazine. Mineralization at 10 degrees C was slow and linear. In inoculated biometers, less 14CO2 was released in [2-14C-ethyl]-atrazine experiments as compared with [U-14C-ring]-atrazine probably as a result of assimilatory incorporation of 14C into biomass. The mineralization rate constants (k) and overall extents of mineralization (Pmax) were higher in biometers that were not sterilized prior to inoculation, suggesting that the native microbial populations in the sediments were contributing to the overall release of 14CO2 from [U-14C-ring]-atrazine and [2-14C-ethyl]-atrazine. A positive correlation between k and aqueous phase atrazine concentrations (Ceq) in the biometers was observed at 25 degrees C, suggesting that sorption of atrazine influenced mineralization rates. The sorption effect on atrazine mineralization was greatly diminished at 10 degrees C. It was concluded that sorption can limit biodegradation rates of weakly-sorbing solutes at high solid-to-solution ratios and at ambient surface temperatures if an active degrading population is present. Under vadose zone and subsurface aquifer conditions, however, low temperatures and the lack of degrading organisms are likely to be primary factors limiting the biodegradation of atrazine.

Adsorption↗
PubMed1987

Effects of colorants in the aquatic environment.

Modern colorants use a variety of chromophoric groups which in turn, may carry a wide range of substituents, both to influence the color, and to provide the required properties for dyeing particular substrates. Thus, there are many thousands of different substances used as commercial colorants. Further, the introduction of new structures to meet particular demands for shade and application is still in an area of major innovative activity. However, in general, individual products have a relatively low sales volume and the strategy which has been developed to assess the effect of dyestuffs (water-soluble, or water-dispersible, colorants) in the environment must necessarily be different from that appropriate for, say, pesticides. The paper discusses this strategy and shows how a "base set" package of data, the concept of which was developed by the colorant industry some years ahead of the "6th Amendment" Directive, may be used to assess the possible effects of a specific dyestuff when discharged in an aqueous effluent. As a second part of the strategy, the paper addresses more general questions relating to the ultimate fate of dyestuffs when discharged in aqueous effluents and in particular considers their most likely environmental distribution, their potential for bioaccumulation, and their biodegradability.

Animals↗
PubMed2004

Enhancement of metal bioremediation by use of microbial surfactants.

Metal pollution all around the globe, especially in the mining and plating areas of the world, has been found to have grave consequences. An excellent option for enhanced metal contaminated site bioremediation is the use of microbial products viz. microbial surfactants and extracellular polymers which would increase the efficiency of metal reducing/sequestering organisms for field bioremediation. Important here is the advantage of such compounds at metal and organic compound co-contaminated site since microorganisms have long been found to produce surface-active compounds when grown on hydrocarbons. Other options capable of proving efficient enhancers include exploiting the chemotactic potential and biofilm forming ability of the relevant microorganisms. Chemotaxis towards environmental pollutants has excellent potential to enhance the biodegradation of many contaminants and biofilm offers them a better survival niche even in the presence of high levels of toxic compounds.

Biodegradation, Environmental↗
PubMed2026

Degradation of a graphene-reinforced polyamide by fungi: When culture conditions matter.

The large-scale production, marketing and disposal of polymer-based graphene products can lead to the dispersal of graphene-enriched plastic particles into terrestrial ecosystems, where they might accumulate if not degraded by organisms. The objective of this work is to test the degradability and compatibility of one polyamide-6 polymer reinforced with reduced graphene-oxide (PA6-rGO) and its base constituents (polyamide-6, PA6; reduced graphene oxide, rGO) using mono- and co-cultures of two lignin-degrading fungi (Bjerkandera adusta and Morchella esculenta) grown under different nutrient conditions. Fungal (co-)cultures were exposed to pure rGO or abraded powders of PA6 and PA6-rGO in two different liquid media, and monitored over time for biomass growth, H2O2 production, and activity of two lignolytic enzymes (i.e., Laccase, Lac, and Lignin peroxidase, LiP). The changes in polyamide structure were evaluated by proton nuclear magnetic resonance and mass spectrometry, and changes in rGO were evaluated by Raman spectroscopy. The materials had no effect on fungal growth. PA6 increased Lac secretion only in low nutrient medium, while PA6-rGO slightly suppressed LiP activity. Only M. esculenta promoted polyamides oxidation when cultured in a low nutrient medium, as evidenced by a change in mass distribution values (m/z: 400-420) and the appearance of a new resonance peak (at 5.37 ppm). Lignolytic exudates in co-cultures low in nutrients caused a greater change in rGO, as shown by the increase in the ID/IG ratio. The degradation of rGO, PA6 and PA6-rGO depended on culture conditions.

Graphite↗
PubMed2006

In-situ surfactant/surfactant-nutrient mix-enhanced bioremediation of NAPL (fuel)-contaminated sandy soil aquifers.

SCOPE AND BACKGROUND: Contamination of soils, aquifers and groundwater by nonaqueous phase liquid (NAPL) pollutants constitutes a major environmental issue of concern, worldwide. The residual (biodegradation-resistant) hydrophobic fuel hydrocarbons entrapped in the soil porous matrix, possess a particular bioremediation challenge due to their becoming virtually immobile, nor desorbable, or water dispersible. Consequently, they are not available as substrates to the micro-organism-based biodegradation. MATERIALS AND METHODS: Our research involves the development of economically feasible, surfactant/surfactant-nutrient mix (SSNM)-enhanced bioremediation methodologies for sustainable, in situ bioremediation of fuel-contaminated aquifers. This requires, methodologically, (a) the optimization, via in vitro 'flow' (columns) lab experiments and screening processes, of an effective mixture for the intended SSNM-enhanced bioremediation; and (b) the study of the combined effect of the optimized SSNM on the solubilization/mobilization and biodegradation of NAPL (fuel) in in vitro site/aquifer-simulated bioremediation. RESULTS AND DISCUSSION: The essence of our findings: (1) kerosene's maximum enhanced mobilization - f = 3.6, compared with that of deionized water, was achieved with an SSNM having the composition of linear alkylbenzene sulfonate (LABS): coco-amphodiacetate (containing N): surfactant-nutrient X (containing both N and P) = 0.15: 0.15: 0.05 g/L, respectively; (2) 62-64% of the initial amount of kerosene in the initially saturated soil matrix, 'packed' in a column, has been eluted from it during approximately 30 days, compared with 68% of kerosene biodegradation in 'vessel' settings, in 21 days. CONCLUSIONS: (1) The indigenous microorganisms present in th vadose zones of fuel-contaminated sandy soil aquifers are potentially capable of unassisted removal of approximately 80% of the initially contained fuel (kerosene), during a period of about 42 days; (2) the major effects of the SSNM addition are (a) enhanced mobilization of the bulky NAPL; and (b) enhanced desorbtion/ solubilization/dispersion of the entrapped NAPL which, in turn, facilitate their enhanced biodegradation. RECOMMENDATIONS AND PERSPECTIVE: Our findings suggest that pre-optimized, biodegradable SSNM is essential for surfactants-based bioremediation of NAPL-contaminated aquifers, in order to make this in-situ methodology both technologically and economically feasible.

Biodegradation, Environmental↗
PubMedDate not supplied

Selection of a pesticide with low environmental impact.

The conditions were analyzed for evaluation of a mean soil biodegradation of a pesticide within a certain region. Different soils from two Czech and two German regions were used for a highly sensitive analysis based on a laboratory incubation of each isolated active soil strain with a radiolabeled pesticide. It was proved for all analyzed soils that the biodegradation activity of the total biomass was caused by only a small part of the present microbial strains. Not only bacteria, but also fungi and yeast have to be taken into consideration in a pesticide biodegradation. The biodegradation products were quantified by radio high-performance liquid chromatography.

Animals↗