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At least 19 recordsLinked to original sources
PubMed2003

Molecular and physiological approaches to understanding the ecology of pollutant degradation.

Pollutant biodegradation in the environment occurs in the context of various interactions among microorganisms. To understand this ecological process, identification of functionally important populations is considered to be the primary step, which can be followed by isolation and laboratory pure-culture studies of the important organisms. Laboratory studies can then proceed to the analysis of in situ activity and interactions with other organisms. Such studies will shape a deeper understanding of the ecology of pollutant degradation and facilitate the development of new bioremediation strategies.

Bacteria↗
PubMed1994

Pollutant degradation by white rot fungi.

The white rot fungi technology is very different from other more well-established methods of bioremediation (e.g., bacterial systems). The differences are primarily due to the mechanisms discussed previously. The unusual mechanisms used by the fungi provide them with several advantages for pollutant degradation, but the complexity of these mechanisms has also made the technology slow to emerge as a viable method of bioremediation. One distinct advantage that white rot fungi have over bacterial systems is that they do not require preconditioning to a particular pollutant. Bacteria must be preexposed to a pollutant to allow the enzymes that degrade the pollutant to be induced. The pollutant must also be present in a significant concentration, otherwise induction of enzyme synthesis will not occur. Therefore, there is a finite level to which pollutants can be degraded by bacteria. In contrast, the degradative enzymes of white rot fungi are induced by nutrient limitation. Thus, cultivate the fungus on a nutrient that is limited in something, and the degradative process will be initiated. Also, because the induction of the lignin-degrading system is not dependent on the chemical, pollutants are degraded to near-nondetectable levels by white rot fungi. Another unique feature of pollutant degradation by white rot fungi involves kinetics. The process of chemical conversion by these fungi occurs via a free-radical process, and thus the degradation of chemicals often follows pseudo-first-order kinetics. In fact, in several studies, it has been found that the rate of mineralization or disappearance of a pollutant is proportional to the concentration of the pollutant. This makes the time required to achieve decontamination more important than the rate of degradation. Because the metabolism of chemicals by bacteria involves mostly enzymatic conversions, pollutant degradation often follows Michaelis-Menton-type kinetics. Therefore, Km values of various degradative enzymes with respect to the pollutant must be considered when using bacteria for bioremediation. Considering this, the solubility of a pollutant or a mixture of pollutants might also present a problem for bacterial degradation. In contrast, using a nonspecific free-radical-based mechanism, the fungi are able to degrade insoluble complex mixtures of pollutants, such as creosote (Aust and Bumpus 1989) and Arochlor (Bumpus and Aust 1987b). Inexpensive nutrient sources, such as sawdust, wood chips, surplus grains, and agricultural wastes, can be used to effectively cultivate white rot fungi.(ABSTRACT TRUNCATED AT 400 WORDS)

Basidiomycota↗
PubMed2005

Taking the fungal highway: mobilization of pollutant-degrading bacteria by fungi.

The capacity of fungi to serve as vectors for the dispersion of pollutant-degrading bacteria was analyzed in laboratory model systems mimicking water-saturated (agar surfaces) and unsaturated soil environments (glass-bead-filled columns). Two common soil fungi (Fusarium oxysporum and Rhexocercosporidium sp.) forming hydrophilic and hydrophobic mycelia, respectively, and three polycyclic aromatic hydrocarbon degrading bacteria (Achromobacter sp. SK1, Mycobacterium frederiksbergense LB501TG, and Sphingomonas sp. L138) were selected based on the absence of mutual antagonistic effects. It was shown that fungal hyphae act as vectors for bacterial transport with mobilization strongly depending on the specific microorganisms chosen: The motile strain Achromobacter sp. SK1 was most efficiently spread along hyphae of hydrophilic F. oxysporum in both model systems with transport velocities of up to 1 cm d(-1), whereas no dispersion of the two nonmotile strains was observed in the presence of F. oxysporum. By contrast, none of the bacteria was mobilized along the hydrophobic mycelia of Rhexocercosporidium sp. growing on agar surfaces. In column experiments however, strain SK1 was mobilized by Rhexocercosporidium sp. It is hypothesized that bacteria may move by their intrinsic motilitythrough continuous (physiological) liquid films forming around fungal hyphae. The results of this study suggest that the specific stimulation of indigenous fungi may be a strategy to mobilize pollutant-degrading bacteria leading to their homogenization in polluted soil thereby improving bioremediation.

Agar↗
PubMed2005

[Horizontal transfer of environmental pollutant-degrading gene and application in bioremediation].

Horizontal gene transfer, unlike vertical gene transfer, is a means of genetic communication in bacteria. In the special polluted environment, horizontal transfer of polluted-degrading gene has significant functions. Study on horizontal transfer of degrading gene in polluted environment may deepen our understanding of the mechanism of bacterial adaptation to the organic-polluted environment. In the practical application in bioremediation, horizontal transfer of degrading gene can be regulated to promote degrading ability of microorganisms. In this article, we will review the advances in the study on mechanisms of genetic interactions among bacteria, the effect of degrading gene transfer in contaminated environment on microorganisms'adaptation to contaminated environment and the degradation of the pollutants.

Adaptation, Physiological↗
PubMed2006

Mixed pollutant degradation by Methylosinus trichosporium OB3b expressing either soluble or particulate methane monooxygenase: can the tortoise beat the hare?

Methanotrophs have been widely investigated for in situ bioremediation due to their ubiquity and their ability to degrade halogenated hydrocarbons through the activity of methane monooxygenase (MMO). It has been speculated that cells expressing the soluble form of MMO (sMMO) are more efficient in cleaning up sites polluted with halogenated hydrocarbons due to its broader substrate range and relatively fast degradation rates compared cells expressing the other form of MMO, the particulate MMO (pMMO). To examine this issue, the biodegradation of mixtures of chlorinated solvents, i.e., trichloroethylene (TCE), trans-dichloroethylene (t-DCE), and vinyl chloride (VC), by Methylosinus trichosporium OB3b in the presence of methane using either form of MMO was investigated over longer time frames than those commonly used, i.e., days instead of hours. Growth of M. trichosporium OB3b along with pollutant degradation were monitored and analyzed using a simple comparative model developed from the Omega model created for analysis of the competitive binding of oxygen and carbon dioxide by ribulose bisphosphate carboxylase. From these findings, it appears that at concentrations of VC, t-DCE, and TCE greater than 10 microM each, methanotrophs expressing pMMO have a competitive advantage over cells expressing sMMO due to higher growth rates. Despite such an apparent growth advantage, pMMO-expressing cells degraded less of these substrates at these concentrations than sMMO-expressing cells during active growth. If the concentrations were increased to 100 muM, however, not only did pMMO-expressing cells grow faster, they degraded more of these pollutants and did so in a shorter amount of time. These findings suggest that the relative rates of growth substrate and pollutant degradation are important factors in determining which form of MMO should be considered for pollutant degradation.

Biodegradation, Environmental↗
PubMed2001

Monte Carlo analysis of uncertainty attached to microbial pollutant degradation rates.

Prediction of bioremediation performance relies on models of microbial activity that are typically fitted to few data, which can lead to large errors in parameter estimates and uncertain prediction of reaction rates and degradation times. This paper presents a Monte Carlo approach to propagate the uncertainty about model parameters and error component through the Michaelis-Menten equation, yielding a probability distribution for both pollutant degradation rate and time for cleanup to some prescribed level. The procedure is illustrated using data related to the degradation kinetics of halogenated hydrocarbons by Methylomicrobium album BG8. It is shown that the assumption of homoscedasticity of the error variance in the Michaelis-Menten model is usually inappropriate, and analytical expressions are derived to account for the dependence of the error variance on the concentration of substrate. Depending on the substrate, the addition of formate might have a significant impact on the expected degradation rates and times, and the proposed approach allows one to test statistically such an impact for various substrate concentrations.

Bacteria↗
PubMed2006

Petroleum pollutant degradation by surface water microorganisms.

BACKGROUND, AIMS AND SCOPE: It is well known that the composition of petroleum or some of its processing products changes in the environment mostly under the influence of microorganisms. A series of experiments was conducted in order to define the optimum conditions for an efficient biodegradation of petroleum pollutant, or bioremediation of different segments of the environment. The aim of these investigations was to show to what extent the hydrocarbons of a petroleum pollutant are degraded by microbial cultures which were isolated as dominant microorganisms from a surface water of a wastewater canal of an oil refinery and a nitrogen plant. Biodegradation experiments were conducted on one paraffinic, and one naphthenic type of petroleum during a three month period under aerobic conditions, varying the following parameters: Inorganic (Kp) or an organic medium (Bh) with or without exposition to light. METHODS: Microorganisms were analyzed in a surface water sample from a canal (Pancevo, Serbia), into which wastewater from an oil refinery and a nitrogen plant is released. The consortia of microorganisms were isolated from the water sample (most abundant species: Phormidium foveolarum--filamentous Cyanobacteria, blue-green algae and Achanthes minutissima, diatoms, algae). The simulation experiments of biodegradation were conducted with the biomass suspension and crude oils Sirakovo (Sir, paraffinic type) and Velebit (Ve, naphthenic type). After a three month period, organic substance was extracted by means of chloroform. In the extracts, the content of saturated hydrocarbons, aromatic hydrocarbons, alcohols and fatty acids was determined (the group composition). n-Alkanes and isoprenoid aliphatic alkanes, pristane and phytane, in the aliphatic fractions, were analyzed using gas chromatography (GC). Total isoprenoid aliphatic alkanes and polycyclic alkanes of sterane and triterpane types were analyzed by GC-MS. RESULTS AND DISCUSSION: Paraffinic type petroleums have a significant loss of saturated hydrocarbons. For naphthenic type petroleum, such a trend has not been observed. The most intensive degradation of n-alkanes and isoprenoid aliphatic alkanes (in paraffinic oil) and isoprenoids (in naphthenic oil) was observed using the inorganic medium Kp in the light; the microbial conversion is somewhat lower with Kp in the dark; with organic medium Bh in the light the degradation is of low intensity; with the same medium in the dark the degradation is hardly to be seen. Steranes and triterpanes were not affected by microbial degradation under the conditions used in our experiments. Obviously, the petroleum biodegradation was restricted to the acyclic aliphatics (n-alkanes and isoprenoids). CONCLUSION: Phormidium foveolarum (filamentous Cyanobacteria--blue-green algae) and Achanthes minutissima (diatoms, algae), microbial cultures isolated as dominant algae from a surface water in a wastewater canal of an oil refinery and a nitrogen plant, have degradable effects dominantly involving petroleum hydocarbons. Petroleum microbiological degradation is more intensive when inorganic medium (in the light) is applied. Having in mind that the inorganic pollutants have been released into the canal as well, this medium reflects more the natural environmental conditions. Polycyclic alkanes of sterane and triterpane type, in spite of the fact that these compounds could be degraded, have remained unchanged regarding abundance and distribution. Since this is the case even for naphthenic type petroleum (which is depleted in n-alkanes), it can be concluded that the biodegradation of petroleum type pollutants, under natural conditions, will be restrained to the n-alkane and isoprenoid degradation. RECOMMENDATION AND OUTLOOK: Performed experiments and simulations of petroleum microbiological degradation may serve for the prediction of the fate of petroleum type pollutants, as well as for definition of conditions for bioremediation of some environmental segments.

Biodegradation, Environmental↗
PubMed2002

A two-stage anaerobic system for biodegrading wastewater containing terephthalic acid and high strength easily degradable pollutants.

The high strength easily biodegradable pollutants (represented by CODE) are strong inhibitors of terephthalic acid (TA) anaerobic biodegradation. At the same time, TA can inhibit easily biodegradable pollutants removal under anaerobic conditions to a limited extent. This mutual inhibition could happen and cause a low removal efficiency of both TA and CODE, when the effluent from TA workshops containing TA and easily biodegradable pollutants are treated by a single anaerobic reactor system. Based upon the treatment kinetics analysis of both TA degradation and CODE removal, a two-stage up-flow anaerobic sludge blanket and up-flow fixed film reactor(UASB-UAFF) system for dealing with this kind of wastewater was developed and run successfully at laboratory scale. An UASB reactor with the methanogenic consortium as the first stage removes the easily biodegradable pollutants(CODE). An UAFF reactor as the second stage is mainly in charge of TA degradation. At a CODE loading of 15.3 g/(L.d) and a TA loading of 1.4 g/(L.d), HRT 18.5 h, the CODE and TA removal rate of the system reached 89.2% and 71.6%, respectively.

Acetates↗
PubMed2000

Engineering of heterologous cytochrome P450 in Acinetobacter sp.: application for pollutant degradation.

Many organisms do not contain the necessary biochemical armoury to carry out the initial oxidative attack of many pollutant chemicals. In the present study, Acinetobacter sp. strain BD413 has been genetically engineered to express the cytochrome P450 xenobiotic-metabolising enzyme CYP105D1 from Streptomyces griseus that has in its repertoire a diverse array of organic pollutants. Further, it is shown that the transformed Acinetobacter calcoaceticus strain BD413 can grow on pollutants unlike control bacteria not expressing cytochrome P450 and that was reflected in release of radiolabel with growth on radiolabelled chlortoluron. We show that cytochrome P450 can enhance the biodegrading repertoire of A. calcoaceticus and discuss the application of such results to bioremediation strategies.

Acinetobacter calcoaceticus↗
PubMed2002

Environmental remediation by an integrated microwave/UV illumination technique. 3. A microwave-powered plasma light source and photoreactor to degrade pollutants in aqueous dispersions of TiO2 illuminated by the emitted UV/visible radiation.

The characteristic features of a novel double-quartz cylindrical plasma photoreactor (DQCPP) were assessed by examining the photodegradation of rhodamine-B dye (RhB+) in aqueous TiO2 dispersions irradiated simultaneously by both microwave radiation and UV/visible radiation emitted from a microwave-powered (MW, 2.45 GHz) electrodeless mercury lamp. The features of the DQCPP lamp are given and discussed in terms of the experimental output UV energy in the wavelength ranges 210-300 and 310-400 nm for applied MW powers from 74 to 621 W. The DQCPP and a water-cooled DQCPP reactor absorbed more than 50% MW radiation (50-88 and 50-75%, respectively). The emitted light irradiance scaled sublinearly with applied MW power. Relative to the DQCPP lamp, loss of irradiance by the water-cooled DQCPP lamp was approximately 28-46% at 250 nm and approximately 41-58% at 360 nm in the range of MW power used. The smallest loss occurred at 178.9 W at which the degradation of RhB+ was subsequently examined by UV/visible spectroscopy and by total organic carbon analyses. Highly intense mercury lines were seen at 365, 404, 435, 546, and 579 nm (those below 365 nm were more than 10 times weaker). About 80% of the RhB+ solution was photomineralized after 60 min of irradiation of the aqueous RhB+/TiO2 dispersion with the DQCPP lamp; no UV/ visible spectral features of RhB+ were evident at wavelengths below 250 nm after 30 min. Possible effects of microwave radiation and temperature on the degradative process are described.

Coloring Agents↗
PubMed2004

The tritrophic trinity: a source of pollutant-degrading enzymes and its implications for phytoremediation.

Barring bioavailability and nutritional limitations, virtually all organic anthropogenic chemicals can be naturally biodegraded. It is to this phenomenon we owe thanks to the long established 'tritrophic trinity' of microbe-plant-insect interactions. Over hundreds of millennia these organisms have coevolved, producing hundreds of thousands of different chemicals that are used to attract, defend, antagonize, monitor and misdirect one another. In comparison, the numbers of truly novel chemicals of anthropogenic origin are negligible. It is only now that we are beginning to appreciate the fortuitous evolution of xenobiotic-degrading enzymes from these interactions. We argue that success in phytoremediation can be hastened through understanding the structure, sources, uses and targets of these secondary metabolites. Owing to recent developments in molecular biology, particularly stable isotope probing, we eagerly anticipate highly significant insights into trophic interactions, particularly in the rhizosphere, providing phytoremediation with a solid mechanistic understanding.

Animals↗
PubMed2003

Modelling in-sewer pollutant degradation processes in the Costa do Estoril sewer system.

Characteristics of wastewater vary during transportation through sewer systems as a result of a number of processes. Under aerobic conditions, in long sewer systems, the reduction of the BOD or COD may be similar to the reduction obtained in conventional primary settling tanks. The mathematical model that was developed is based on a number of different existing models: the ASM n. 1 and ASM n. 2 models, the AEROSEPT model and the WATS model. The model also includes a prediction of reaeration at falls. The module of the anoxic conditions was adapted from the ASM n. 2 model. This module is a first attempt to model the degradation of organic matter in sewer systems under anoxic conditions. The mathematical model was applied to the Costa do Estoril intercepting sewer, and the obtained results are discussed taken into account the experimental data that was collected during a three-month period. Average removals of dissolved COD over 20% have been obtained. In the paper special emphasis is given to the importance of the performance of the Costa do Estoril sewer system as a biological reactor.

Bacteria, Aerobic↗
PubMed1999

Towards elucidation of microbial community metabolic pathways: unravelling the network of carbon sharing in a pollutant-degrading bacterial consortium by immunocapture and isotopic ratio mass spectrometry.

Although much information on metabolic pathways within individual organisms is available, little is known about the pathways operating in natural communities in which extensive sharing of nutritional resources is the rule. In order to analyse such a consortium pathway, we have investigated the flow of 4-chlorosalicylate as carbon substrate within a simple chemostat microbial community using 13C-labelled metabolites and isotopic ratio mass spectrometric analysis of label enrichment in immunocaptured member populations of the community. A complex pathway network of carbon sharing was thereby revealed, involving two different metabolic routes, one of which is completely novel and involves the toxic metabolite protoanemonin. The high stability of the community results, at least in part, from interdependencies based on carbon sharing and the rapid removal of toxic metabolites.

Alcaligenes↗