Showing papers on "Microbial biodegradation published in 1999"

Biodegradation of aromatic compounds by microalgae

Abstract: The microbial degradation of aromatic pollutants has been well characterized over a period of more than 30 years. The microbes of most interest have been bacteria and fungi. Only relatively recently has the question of how algae figure in the catabolism of these compounds attracted a degree of interest. The aim of this review is to highlight the biodegradative capabilities of microalgae on aromatic compounds, ranging from simple monocyclic to more complex polycyclic pollutants. This paper will briefly encompass studies which have investigated the growth on and the oxidation of these compounds by algae, as well as a more detailed characterization of the catabolic sequences involved in the transformation of these compounds.

Formation of Bound Residues during Microbial Degradation of [14C]Anthracene in Soil

Abstract: Carbon partitioning and residue formation during microbial degradation of polycyclic aromatic hydrocarbons (PAH) in soil and soil-compost mixtures were examined by using [14C]anthracenes labeled at different positions. In native soil 43.8% of [9-14C]anthracene was mineralized by the autochthonous microflora and 45.4% was transformed into bound residues within 176 days. Addition of compost increased the metabolism (67.2% of the anthracene was mineralized) and decreased the residue formation (20. 7% of the anthracene was transformed). Thus, the higher organic carbon content after compost was added did not increase the level of residue formation. [14C]anthracene labeled at position 1,2,3,4,4a,5a was metabolized more rapidly and resulted in formation of higher levels of residues (28.5%) by the soil-compost mixture than [14C]anthracene radiolabeled at position C-9 (20.7%). Two phases of residue formation were observed in the experiments. In the first phase the original compound was sequestered in the soil, as indicated by its limited extractability. In the second phase metabolites were incorporated into humic substances after microbial degradation of the PAH (biogenic residue formation). PAH metabolites undergo oxidative coupling to phenolic compounds to form nonhydrolyzable humic substance-like macromolecules. We found indications that monomeric educts are coupled by C-C- or either bonds. Hydrolyzable ester bonds or sorption of the parent compounds plays a minor role in residue formation. Moreover, experiments performed with 14CO2 revealed that residues may arise from CO2 in the soil in amounts typical for anthracene biodegradation. The extent of residue formation depends on the metabolic capacity of the soil microflora and the characteristics of the soil. The position of the 14C label is another important factor which controls mineralization and residue formation from metabolized compounds.

13C/12C isotope fractionation of aromatic hydrocarbons during microbial degradation

Abstract: The influence of microbial degradation on the 13C/12C isotope composition of aromatic hydrocarbons is presented using toluene as a model compound. Four different toluene-degrading bacterial strains grown in batch culture with oxygen, nitrate, ferric iron or sulphate as electron acceptors were studied as representatives of different environmental redox conditions potentially prevailing in contaminated aquifers. The biological degradation induced isotope shifts in the residual, non-degraded toluene fraction and the kinetic isotope fractionation factors alphaC for toluene degradation by Pseudomonas putida (1.0026 +/- 0.00017), Thauera aromatica (1.0017 +/- 0.00015), Geobacter metallireducens (1.0018 +/- 0.00029) and the sulphate-reducing strain TRM1 (1.0017 +/- 0.00016) were in the same range for all four species, although they use at least two different degradation pathways. A similar 13C/12C isotope fractionation factor (alphaC = 1.0015 +/- 0.00015) was observed in situ in a non-sterile soil column in which toluene was degraded under sulphate-reducing conditions. No carbon isotope shifts resulting from soil-hydrocarbon interactions were observed in a non-degrading soil column control with aquifer material under the same conditions. The results imply that microbial degradation of toluene can produce a 13C/12C isotope fractionation in the residual hydrocarbon fraction under different environmental conditions.

Effect of concentration on sequestration and bioavailability of two polycyclic aromatic hydrocarbons

Abstract: A study was conducted to determine the effect of concentration on sequestration and bioavailability of phenanthrene and pyrene in soil. The compounds at 1.0, 10, and 100 mg/kg of soil became increasingly resistant to a mild solvent extraction and progressively less bioavailable to earthworms (Eisenia foetida) as a result of aging for 120 days. Aging also resulted in both compounds at 1.0 and 10 mg/kg and phenanthrene but not pyrene at 100 mg/kg becoming more resistant to microbial degradation. Increasing the concentration led to an increase in the percentages of the unaged and aged compounds that were susceptible to microbial degradation. Some of each of the two compounds was still available to earthworms following biodegradation. The data show that sequestration of the polycyclic aromatic hydrocarbons occurs at both low and high concentrations.

Bioremediation of metals and radionuclides: What it is and How itWorks

Abstract: This primer is intended for people interested in DOE environmental problems and in their potential solutions It will specifically look at some of the more hazardous metal and radionuclide contaminants found on DOE lands and at the possibilities for using bioremediation technology to clean up these contaminants Bioremediation is a technology that can be used to reduce, eliminate, or contain hazardous waste Over the past two decades, it has become widely accepted that microorganisms, and to a lesser extent plants, can transform and degrade many types of contaminants These transformation and degradation processes vary, depending on physical environment, microbial communities, and nature of contaminant This technology includes intrinsic bioremediation, which relies on naturally occurring processes, and accelerated bioremediation, which enhances microbial degradation or transformation through inoculation with microorganisms (bioaugmentation) or the addition of nutrients (biostimulation)

Kinetic model of biosurfactant-enhanced hexadecane biodegradation by Pseudomonas aeruginosa.

Abstract: Many sites of environmental concern contain groundwater contaminated with nonaqueous phase liquids (NAPL). In such sites interfacial processes may affect both the equilibrium and kinetic behavior of the system. In particular, insoluble hydrocarbon partitioning and microbial biodegradation of insoluble hydrocarbon are influenced by the physicochemical and interfacial characteristics of the system. A mechanistic model describing the influence of biological surfactants on microbial biodegradation of liquid-phase insoluble hydrocarbon and subsequent reduction of nonaqueous-phase liquid hydrocarbon is presented. The model consists of six coupled differential equations which use lumped kinetic parameters to describe surfactant micelle formation and diffusion to the microbial cell, nonlinear kinetic expressions for microbial growth and degradation of insoluble hydrocarbon, kinetic spatial descriptions of the change in NAPL-phase droplet size and the organic phase volume fraction with time, as well as equilibrium partitioning expressions for hydrophobic organic contaminant partioning into the surfactant micelle. The model is validated by comparison to data obtained for hexadecane degradation in a well-mixed batch system by the biosurfactant producing microorganism Pseudomonas aeruginosa strain PG201 as well as for nonproducing mutants' growth and hexadecane biodegradation in the presence of exogenously added biosurfactant. Experimentally determined biological growth parameters, as well as physical parameters such as hydrocarbon droplet size, were applied in the kinetic model. Parameter sensitivity analysis was performed on the physical and biological parameters in the model. The parameter sensitivity analysis indicates that for the biological system examined the rate of hydrocarbon solubilization and micellar transport to the cell controls the rate at which cellular uptake and biodegradation of insoluble hydrocarbon occurs. Practical aspects relating to use of the model for support of surfactant-based bioremediation efforts are discussed.

Bioavailability of hydrocarbons during microbial remediation of a sandy soil.

Abstract: The microbial degradation of hydrocarbons was studied in an artificially contaminated sandy soil, using a pilot-scale percolator system. After a short lag period, an intensive degradation occurred, which diminished in time and completely stopped in the end, despite large residual contaminations (residues of 56% diesel fuel, 20% n-hexadecane and 3.5% phenanthrene at the initial loadings of each 3000 mg/kg). The remaining pollutant content was influenced by the kind of hydrocarbon but was nearly independent of its initial loading. According to a model-aided analysis of the carbon dioxide production during remediation, the observed stagnation of degradation was caused by a limited bioavailability of the pollutants. The degradation in the soil-free aqueous phase was more extensive than in the soil, which suggests that the limited bioavailability in the soil can be attributed mainly to matrix-dependent rather than substrate-dependent influences. Generally, fine particles and organic matter are mainly responsible for the adsorption of pollutants to the soil matrix. Our sandy soil also bound hydrocarbons adsorptively although it contained neither silty material nor significant amounts of organic matter. As shown by Brunauer Emmett Teller (BET) analysis, the soil particles were covered by micropores, which enlarged the soil surface by a factor of 120 in comparison with the macroscopic surface area. The microporosity is the reason for the hydrocarbons being more strongly adsorbed to the sandy soil than expected.

Sphingomonads involved in the biodegradation of xenobiotic polymers.

Abstract: Sphingomonads involved in the microbial degradation of xenobiotic polymers are introduced. The metabolism of polyethylene glycol was the primary focus of the study. Several others, including polyvinyl alcohol, polyethylene and polyaspartate were also studied. It is suggested that these xenobiotic polymers are metabolized by intracellular enzymes located in the periplasmic space or bound to membranes, indicating that transport of these polymers through outer membranes is requisite for their metabolism. Involvement of specific membrane structures of sphingomonads such as unusual sphingolipids is suggested for membrane transport of xenobiotic compounds, especially hydrophobic materials.

The University of Minnesota Biocatalysis/ Biodegradation Database: specialized metabolism for functional genomics

Abstract: The University of Minnesota Biocatalysis/Biodegradation Database (UM-BBD, http://www.labmed.umn.edu/umbbd/i nde x.html) first became available on the web in 1995 to provide information on microbial biocatalytic reactions of, and biodegradation pathways for, organic chemical compounds, especially those produced by man. Its goal is to become a representative database of biodegradation, spanning the diversity of known microbial metabolic routes, organic functional groups, and environmental conditions under which biodegradation occurs. The database can be used to enhance understanding of basic biochemistry, biocatalysis leading to speciality chemical manufacture, and biodegradation of environmental pollutants. It is also a resource for functional genomics, since it contains information on enzymes and genes involved in specialized metabolism not found in intermediary metabolism databases, and thus can assist in assigning functions to genes homologous to such less common genes. With information on >400 reactions and compounds, it is poised to become a resource for prediction of microbial biodegradation pathways for compounds it does not contain, a process complementary to predicting the functions of new classes of microbial genes.

Assessing the oil degradation potential of endogenous micro‐organisms in tropical marine wetlands

Abstract: As part of a larger study on the bioremediation of oil spills in tropical mangrove habitats, we conducted a series of flask experiments to test for the presence of hydrocarbon degrading microdashorganisms in representative wetland habitats. Also tested was the biodegradation of selected oils (Gippsland Crude, Arabian Light Crude and Bunker C), that are transported along the Australian coast. We also tested for potential inhibition of biodegradation by natural organics in the mangrove pore waters and evaluated the ability of an oxygen release compound (ORC) to stimulate biodegradative processes. Evaporation was a significant factor in removing the light alkane and aromatic hydrocarbons from air and nitrogen sparged flasks. Evaporation removed sim27% of the Gippsland, sim37%of the Arabian, and sim10% of the Bunker oils. Oxygen was necessary to support biodegradation as expected. The microdashorganisms were capable of biodegrading the nondashvolatile saturate fraction of each oil. Degradation removed another 14 of the Gippsland, 30 of the Arabian, and 22 of the Bunker C oils. Normalisation of the individual aromatic hydrocarbon classes to internal triterpane biomarkers indicated some degradation of aromatics in the Arabian Light and Bunker C oils. Although alkane degradation rates were comparable in the three oils, the Gippsland oil had a higher wax content and after 14 days incubation, still contained as much as 25 of the alkanes present in the original oil. Thus, degradation of its aromatic fraction may have been delayed. Based on these results we estimate that Arabian Light Crude oil would have a shorter residence time than the other oils in mangrove sediment. It has a higher content of light hydrocarbons, which are readily removed by both physical and microbial processes. The Bunker C would be expected to have the longest residence time in mangrove sediment, because it contains a larger percentage of higher molecular weight, unresolved components. Comparison of the efficiency of inoculates from three tropical intertidal habitats (Avicennia and Rhizophora mangroves, plus salt marsh sediments) indicated the presence of hydrocarbon degrading microdashorganisms in all three habitats. There was no known history of oil contamination in the soil source area. There was no inhibition of degradation due to addition of mangrove pore waters. The ORC did not facilitate degradation in closed laboratory experiments. These results were used to formulate a bioremediation strategy to treat oiled sediments in mangrove forests in Queensland Australia, which was based on forced aeration and nutrient addition. Evaporation was a significant factor in removing the light alkane and aromatic hydrocarbons from air and nitrogen sparged flasks. Evaporation removed sim27% of the Gippsland, sim37% of the Arabian, and sim10% of the Bunker oils. Oxygen was necessary to support biodegradation as expected. The micro-organisms were capable of biodegrading the non-volatile saturate fraction of each oil. Degradation removed another 14% of the Gippsland, 30% of the Arabian, and 22% of the Bunker C oils. Normalisation of the individual aromatic hydrocarbon classes to internal triterpane biomarkers indicated some degradation of aromatics in the Arabian Light and Bunker C oils. Although alkane degradation rates were comparable in the three oils, the Gippsland oil had a higher wax content and after 14 days incubation, still contained as much as 25% of the alkanes present in the original oil. Thus, degradation of its aromatic fraction may have been delayed. Based on these results we estimate that Arabian Light Crude oil would have a shorter residence time than the other oils in mangrove sediment. It has a higher content of light hydrocarbons, which are readily removed by both physical and microbial processes. The Bunker C would be expected to have the longest residence time in mangrove sediment, because it contains a larger percentage of higher molecular weight, unresolved components. Comparison of the efficiency of inoculates from three tropical intertidal habitats (Avicennia and Rhizophora mangroves, plus salt marsh sediments) indicated the presence of hydrocarbon degrading micro-organisms in all three habitats. There was no known history of oil contamination in the soil source area. There was no inhibition of degradation due to addition of mangrove pore waters. The ORC did not facilitate degradation in closed laboratory experiments. These results were used to formulate a bioremediation strategy to treat oiled sediments in mangrove forests in Queensland Australia, which was based on forced aeration and nutrient addition.

The microbial biodegradation of paraquat in soil

Abstract: The microbial degradation of [ 14 C]paraquat using cultures from two agricultural soils was investigated. The experiments were carried out in the absence of light, under aerobic conditions. Degradation was rapid, with 50% mineralisation to [ 14 C]carbon dioxide occurring within three weeks. HPLC, capillary electrophoresis and mass spectroscopy confirmed that the majority (>85%) of the remaining radiochemical in solution was [ 14 C]oxalic acid, and that no paraquat remained.

Microbial degradation of poly-β-hydroxybutyrate using landfill soils

Abstract: The population of poly-β-hydroxybutyrate-degrading microorganisms and the biodegradation of PHB in local landfill soils were examined in vitro and in vivo. Forty-two PHB-degraders consisting of 12 bacteria, 25 actinomycetes and 5 moulds were isolated. The total PHB-degraders averaged 4.7 × 10 7 and 20×10 4 colony forming units (cfu)/g for San Mateo wet and dry soils, respectively, and 2.3 × 10 7 and 8.5 × 104 cfu/g for Carmona wet and dry samples, respectively. The PHB-degraders formed 0-59% of the total microbial population in San Mateo and 8-42% in Carmona. Complete (100%) degradation of PHB powder was observed for Chryseomonas-27 and Aspergillus-39 on day 5 in shake flask culture and for Streptomyces-4 on day 7. Burial test in landfill soils showed a 90-91% weight loss of PHB film strips within four weeks; the weight loss of polypropylene film strips was up to 0.12% only. Scanning electron micrographs of degraded films revealed the attachment of microbial cells and fungal mycelium and spores on the surfaces. Holes and cavities were also noted due to the microbial degradation processes.

Non-haem iron-containing oxygenases involved in the microbial biodegradation of aromatic hydrocarbons.

Abstract: A wide variety of aromatic hydrocarbons can be degraded aerobically by micro-organisms. A large fraction of the metabolic pathways are initiated by oxygenases containing Fe(II) at the active sites, which participates in the oxygenation and activation of the hydrocarbons. Mono-oxygenations and dioxygenations are found in these pathways. Some of these enzymes can catalyse either or both reactions, depending on the nature of the substrate. Two general themes are found: mononuclear Fe(II) centres that must be reduced by one electron at a time, or di-iron centres that can be reduced by two electrons. The electrons from NAD(P)H can be delivered by either an electron-transfer chain consisting of a flavin and one or more [2Fe-2S] centres, or a pterin. Proposed mechanisms generally involve higher oxidation states of the iron (Fe = O), analogous to those for P450, and peroxidase systems. These strong oxidants are necessary to oxidize aromatic and aliphatic compounds. Mechanisms currently considered viable for these reactions require significant changes in ligation during catalysis. The structures of the non-haem iron centres may be particularly well-suited for such transformations.

Biodegradation of Polycyclic Aromatic Hydrocarbons

Abstract: Polycylic aromatic hydrocarbons (PAHs), such as petroleum and petroleum derivatives, are widespread organic pollutants entering the environment, chiefly, through oil spills and incomplete combustion of fossil fuels. Since most PAHs are persist in the environment for a long period of time and bioaccumulate, they cause environmental pollution and effect biological equilibrium dramatically. Biodegradation of some PAHs by microorganisms has been biochemically and genetically investigated. Gene locations for some of these pathways are frequently found in exrachromosomal elements. Determination, isolation and characterization of microorganisms which participate in the bidegradation of PAHs have great significance in the decontamination of the environment in shorter periods. Decontamination of polycyclic aromatic hydrocarbons (PAHs), which cause environmental pollution and effect biological equilibrium dramatically, has also great significance for environmental and applied microbiology. In this review article, we focussed on the biodegradation of hydrocarbons which contaminates the environment.

13C/12C Stable Isotope Fractionation of Toluene by Anaerobic Degradation

Abstract: In microbial degradation experiments with soil percolation columns and a pure bacterial culture the consumption and the13C/12C stable carbon isotope composition of aromatic hydrocarbons were monitored in order to evaluate if isotopic fractionation is applicable as a parameter to evaluate biodegradation processes in field studies

Bakterientoxizität - standardisierte Testmethoden und Erfahrungen

Abstract: In laboratories, ecotoxicological tests with bacteria are required either to detect toxic effects of compounds, mixtures or wastewaters to microorganisms and to predict their behaviour in surface waters, wastewater treatment plants, anaerobic digesters, soils or composting facilities or to determine inhibitory concentrations before microbial degradation tests are performed.These toxic effects are indicated as effective concentrations (EC-values). For example, an EC 50 -value indicates a concentration at which a substance will inhibit a certain microbial process, usually respiration or growth, to a degree of 50%. In natural and technical environments, bacteria are able to degrade numerous different chemical compounds. They are the basis for the self-purification processes in natural waters and are responsible for the correct operation of biological wastewater or solid waste treatment plants.These microbial processes are always performed by mixed cultures, which react to toxic stress differently from pure cultures. Therefore, the transfer of results obtained in the laboratory to real environmental conditions may be crucial pure bacterial cultures are used. As could be shown by several studies performed in BASF's Ecology Laboratory, results obtained with pure cultures such as Pseudomonas putida are often readily reproducible, but may cause false predictions. Standardized bacterial tests which work with natural microbial communities such as the respiration inhibition test (ISO 8192, OECD 209) or the growth inhibition test ISO 15522 offer a solution to this problem by using activated sludge as an inoculum. For specific problems, special toxicity tests such as the nitrification inhibition test (ISO 9509) or the anaerobic inhibition test (ISO draft 13641) should be used.

Microbial Enzymes in Biodegradation

Abstract: Biodegradation of organic pollutants cleanses the Earth much like the mammalian immune system cleanses the body of foreign viruses and bacteria. Both systems have evolved to handle millions of different foreign agents. More than 10 million organic compounds are known on Earth and many of those are likely to be biodegradable. How does nature biodegrade such a vast range of compounds? First, hundreds of thousands, if not millions, of compounds are formed naturally by biosynthesis or diagenesis. The latter process has generated fossil fuel hydrocarbons and heterocyclic compounds (Blumer, 1976). Second, life has likely existed on Earth for at least 3.6 billion years (Lazcano & Miller, 1996), during which time evolution has trained life to catabolize many carbon sources. Consider that early life forms were thought to be bathed in a soup of organic compounds formed by prebiotic chemical reactions and these provided some of the first energy sources for metabolism. Single celled life forms, Eubacteria and Archae in the modern world, have continued to feed on the "soup" around them. Their evolution over 3.6 billion years has generated enormous phylogenetic diversity which is matched by enormous metabolic versatility in the prokaryotic world (Pace, 1997). But while prokaryotes have recycled organic matter on Earth over eons, organic chemists in the last century have fashioned millions of new organic structures, posing new challenges to microbial metabolism. Yet, microbes have apparently responded. There are numerous reports of industrial chemicals initially evading microbial catabolism, as evidenced by their persistence in the environment, only to be later documented to be biodegradable. Examples include polychlorinated biphenyls (Brown, et.al, 1987), tetrachloroethene (Maymo-Gatell, et.al, 1997), and atrazine (Cook, 1987); all compounds that in early studies were poorly, if at all, cleared from the environment. All of these com-

Biodegradation of Organic Pollution Involving Soil Iron(III) Solubilized by Bacterial Siderophores as an Electron Acceptor

Abstract: Microbial degradation of organic matter, like any oxidation process, requires an oxidizing agent. The role of the latter may be played by oxygen (the most common electron acceptor). However, under microaerobic conditions (ground water, subsurface soil) the supply of oxygen is limited, which, in its turn, may limit the biodegradation rate. An alternative possibility is the use of other electron acceptors, among which iron(III) is generally abundant in soil, yet being poorly soluble at physiological pH values. In this case its bioavailability can be essentially increased, e.g. by adding a chelating agent: NTA, EDTA, etc.

Microbial degradation of polychlorinated biphenyls and alkylated polycyclic aromatic hydrocarbons

Abstract: Polychlor ina ted biphenyls ( P C B s ) and p o l y c y l i c aromatic hydrocarbons ( P A H s ) are widespread environmental contaminants, and their presence i n the environment is a cause for concern because they are l i nked to a variety o f tox ic effects. In this thesis, some aspects o f the mic rob i a l degradation o f P C B s and a l k y l P A H s are investigated. A n a l y t i c a l methods for the extraction and analysis (by us ing gas chromatography coupled to mass spectrometry ( G C / M S ) ) o f P C B s were developed and tested. The P C B content o f three sediment cores taken f rom lakes i n Cambr idge B a y (Nunavut) was analyzed, but no evidence for in-si tu mic rob i a l dechlor inat ion o f P C B s was found. A variety o f approaches to the development o f mic rob i a l enrichment cultures were tested. The most successful were developed by us ing 4-bromobenzoate, as an amendment to stimulate dehalogenation act ivi ty, and sediment col lected from Esqu ima l t Harbour (Br i t i sh C o l u m b i a ) as an i nocu lum source. The dechlor inat ion o f A r o c l o r 1260 i n soils f rom Reso lu t ion Island (Nunavut) and Saglek (Labrador) by us ing a variety o f enrichment cultures was investigated. Ex tens ive dechlor inat ion o f h ighly-chlor ina ted P C B congeners was achieved, and the most abundant products f rom A r o c l o r 1260 dechlor inat ion were tetrachlorobiphenyls. A method to determine the identity o f one major dechlor inat ion product by us ing M S / M S was developed, and the dechlor inat ion product was found to be 24-24tetrachlorobipheny 1. Some factors that cou ld affect the extent and rate o f P C B dechlor inat ion were investigated. It was found that autoclaving pre-incubated cultures pr ior to inocula t ion w i t h P C B d e c h l o r i n a t i n g enrichment cultures increased the rate and extent o f P C B