Showing papers on "Microbial biodegradation published in 1995"

Environmental aspects of PAH biodegradation

Abstract: Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants, some of which are on the US Environmental Protection Agency priority pollutant list. Consequently, timely clean-up of contaminated sites is important. The lower-mol-wt PAHs are amenable to bioremediation; however, higher-mol-wt PAHs seem to be recalcitrant to microbial degradation. The rates of biodegradation of PAHs are highly variable and are dependent not only on PAH structure, but also on the physicochemical parameters of the site as well as the number and types of microorganisms present. PAHs sorb to organic matter in soils and sediments, and the rate of their desorption strongly influences the rate at which microorganisms can degrade the pollutants. Much of the current PAH research focuses on techniques to enhance the bioavailability and, therefore, the degradation rates of PAHs at polluted sites. Degradation products of PAHs are, however, not necessarily less toxic than the parent compounds. Therefore, toxicity assays need to be incorporated into the procedures used to monitor the effectiveness of PAH bioremediation. In addition, this article highlights areas of PAH research that require further investigation.

A review of bacterial degradation of pesticides

Abstract: Pesticide fate in the environment is affected by microbial activity. Some pesticides are readily degraded by microorganisms, others have proven to be recalcitrant. A diverse group of bacteria, including members of the genera Alcaligenes, Flavobacterium, Pseudomonas and Rhodococcus, metabolize pesticides. Microbial degradation depends not only on the presence of microbes with the appropriate degradative enzymes, but also on a wide range of environmental parameters. This review describes recent advances in biodegradation of pesticides by addressing the biology and molecular characterization of some pesticide degrading bacteria.

Potential for Bioremediation of Xenobiotic Compounds by the White-Rot Fungus Phanerochaete chrysosporium

Abstract: The white-rot fungi produce an unusual enzyme system, characterized by a specialized group of peroxidases, that catalyzes the degradation of the complex plant polymer lignin. This ligninolytic system shows a high degree of nonspecificity and oxidizes a very large variety of compounds in addition to lignin. Among these compounds are numerous environmental pollutants. Thus, the white-rot fungi show considerable promise as bioremediation agents for use in the restoration of environments contaminated by xenobiotic molecules. One white-rot fungus, Phanerochaete chrysosporium, has been studied in great detail with regard to ligninolytic enzymes and the degradation of anthropogenic chemicals. It has been widely promoted as a bioremediation agent. This article examines literature concerning the degradation of xenobiotic compounds by Phanerochaete chrysosporium and attempts to critically assess this organism's real potential as a bioremediation tool.

Biodegradation of naphthalene in aqueous nonionic surfactant systems.

Abstract: The principal objective of this study was to quantify the bioavailability of micelle-solubilized naphthalene to naphthalene-degrading microorganisms comprising a mixed population isolated from contaminated waste and soils. Two nonionic surfactants were used, an alkylethoxylate, Brij 30 (C12E4), and an alkylphenol ethoxylate, Triton X-100 (C8PE9.5). Batch experiments were used to evaluate the effects of aqueous, micellized nonionic surfactants on the microbial mineralization of naphthalene and salicylic acid, an intermediate compound formed in the pathway of microbial degradation of naphthalene. The extent of solubilization and biodegradation under aerobic conditions was monitored by radiotracer and spectrophotometric techniques. Experimental results showed that surfactant concentrations above the critical micelle concentration were not toxic to the naphthalene-degrading bacteria and that the presence of surfactant micelles did not inhibit mineralization of naphthalene. Naphthalene solubilized by micelles of Brij 30 or Triton X-100 in liquid media was bioavailable and degradable by the mixed culture of bacteria.

Microbial degradation in soil microcosms of fuel oil hydrocarbons from drilling cuttings.

Abstract: The biodegradation of the fuel oil hydrocarbons contained in drilling cuttings was studied in soil microcosms during a 270-day experiment. Concentration and chemical composition of residual hydrocarbons were periodically monitored by quantitative capillary gas chromatography. The decrease in hydrocarbon concentration was logarithmic with time. At the end of the experiment, the fuel oil was 75% degraded. In the saturated fraction, normal and branched alkanes were almost totally eliminated in 16 days ; 22% of the cycloalkanes were not assimilated. The aromatic fraction was 71% degraded ; some polycyclic aromatics were persistent. The resin fraction (10% of the initial weight) was completely refractory to biodegradation. The inorganic part of drilling cuttings had no influence on the biodegradation rates of hydrocarbons. Biogenic hydrocarbons and traces of degradable fuel oil hydrocarbons were protected from microbial activity by the soil and cuttings matrix. Enumerations of total heterotrophic bacteria and hydrocarbon-utilizing bacteria showed a strong stimulation in both populations. Hydrocarbon-degrading strains of bacteria and fungi were isolated and identified at the generic or specific level.

Mineralization of polycyclic and N‐heterocyclic aromatic compounds in hydrocarbon‐contaminated soils

Abstract: The comparative mineralization of eight polycyclic aromatic compounds in five soils collected from an abandoned coal tar refinery in eastern Ohio was determined. The soils showed differences only in total extractable hydrocarbon content of the soil chemical characteristics measured. The compounds studied included five polycyclic aromatic hydrocarbons (phenanthrene, anthracene, pyrene, and carcinogenic benz[a]anthracene and benzo[a]pyrene) and three N-heterocyclic aromatics (9H-carbazole, and carcinogenic 7H-dibenzo[c,g]carbazole and dibenz[a,j]acridine). Mineralization was measured by serum bottle radiorespirometry. Only phenanthrene, anthracene, pyrene, benz[a]anthracene, and carbazole were mineralized in the soils after 64 d. Two of the soils with eight to 15 times the hexane-extractable hydrocarbon content consistently showed more rapid initial rates and higher overall extents of mineralization compared to the other three soils. Overall extents of mineralization ranged from 38 to 55% for phenanthrene, 10 to 60% for anthracene, 25 to 70% for pyrene, background to 40% for benz[a]anthracene, and 25 to 50% for carbazole after 64 d. Extents of mineralization by indigenous soil microbiota appear to be more dependent on the chemical characteristics of the soil and not soil total biomass and activity. Cultures capable of degrading phenanthrene, anthracene, and pyrene were obtained following enrichment techniques. A Mycobacterium sp. capable of degrading these three compounds was isolated and reintroduced into two of the soils, resulting in mineralization enhanced above that of the indigenous soil microbial population. These data indicate that the future success of bioremediation methods relies on the characterization of environmental parameters affecting microbial degradation as well as the isolation of microbial populations that can reduce toxicity in the environment.

Biotransformations : microbial degradation of health-risk compounds

Abstract: Microbial degradation of nitrogenous xenobiotics of environmental concern, V. Andreoni et al synthesis and degradation of dimethyl nitrosamine in the natural environment and in humans, T. Yoshinari aflatoxin biotransformations - biodetoxification aspects, V.P. Singh metabolism and cometabolism of halogenated C-1 and C-2 hydrocarbons, M.K. Jain and C.S. Criddle aerobic biodegradation of polycyclic and halogenated aromatic compounds, E. Grund et al microbial degradation of halogenated aromatics, M.A. Bhat and C.S. Vaidyanathan microbial degradation of azo dyes, J.A. Bumpus microbial degradation of natural rubber, A. Tsuchii microbial degradation of polyesters, K. Mukai and Y. Doi degradation of hazardous organic compounds by rhizosphere microbial communities, T.A. Anderson et al microbial degradation of styrene, S. Hartmans microbial degradation of vinyl chloride, S. Hartmans isolation and characterization of neurotoxin-degrading gene, I.M. Santha and S.L. Mehta microbial degradation of tannins, R.K. Saxena et al.

Reductive Dechlorination of PCB-Contaminated Sediments in an Anaerobic Bioreactor System.

Abstract: An anaerobic bioreactor system was operated in a batch recycle mode to establish the microbial biodegradation of Aroclor 1248-spiked sediment, utilizing sanitary landfill leachate as a novel carbon, nutrient, and/or microbial source. Experiments conducted on two bioreactors confirmed that significant dechlorination of Aroclor 1248-spiked sediments occurred. After 13 weeks of operation, the average total chlorine/biphenyl of the original Aroclor was reduced by 11% and 23%, with the majority of dechlorination occurring within 7 weeks. No dechlorination was observed in the sterilized control reactor. The overall significance is the first reported occurrence of anaerobic dechlorination of a PCB-contaminated sediment in a low-cost laboratory-scale bioreactor system. The environmental significance is the reduction in chlorine content of the original Aroclor, an important component in any environmental bioremediation program. Innovative approaches to laboratory-scale bioreactor monitoring and bioreactor design principles applicable to hazardous waste containment areas are also discussed.

Process for in-situ bidegradation of chlorinated aliphatic hydrocarbons by subsurface hydrogen injection

Abstract: The present invention provides a method for stimulating in-situ microbial biodegradation of halogenated organic compounds in an aqueous subsurface environment comprising the delivery of hydrogen, in the absence of nutritional factors, into the subsurface environment.

Intrinsic in situ anaerobic biodegradation of chlorinated solvents at an industrial landfill

Abstract: The DuPont Necco Park Landfill in Niagara Falls, New York, is contaminated with numerous chlorinated solvents at concentrations of up to hundreds of mg/L in the groundwater. An extensive monitoring program was conducted to determine if intrinsic anaerobic biodegradation was occurring at the site, to determine what might limit this activity, and to characterize this activity with depth and distance away from the landfill. It was determined that anaerobic microbial activity was occurring in all zones, based upon the presence of intermediate products of the breakdown of the chlorinated solvents and the presence of final metabolic end products such as ethene and ethane. Aerobic, iron-reducing, manganese-reducing, sulfate-reducing, and methanogenic redox conditions were identified at the site. High levels of nitrogen and biodegradable organic compounds were present in most areas to support cometabolic anaerobic microbial activity against the chlorinated solvents. Intrinsic biodegradation is clearly evident and is effective in reducing the concentrations of chlorinated organic in the groundwater at the site. Groundwater modeling efforts during development of a site conceptual model indicated that microbial degradation was necessary to account for the downgradient reduction of chlorinated volatile organic compounds as compared to chloride, a conservative indicator parameter.

Degradation of hazardous organic compounds by rhizosphere microbial communities

Abstract: Publisher Summary The variety of plants and chemicals studied for the evidence of microbial degradation in the rhizosphere strongly suggests that a diverse and synergistic microbial community, rather than a single species, is responsible for biotransformation of toxicants in the rhizosphere. Participation of a microbial community is implicated by (i) the extreme diversity and complexity of toxicants degraded, and (ii) the knowledge that many of these compounds are completely degraded only in the presence of interacting microbial populations (consortia). Moreover, data presented, herein, from phospholipid fatty acid analysis, 14C acetate incorporation, and PHA analysis of micro-organisms from the rhizosphere are consistent with the participation of a microbial community in TCE degradation. Other mechanisms can also be invoked to explain how microbial transformations occur in the rhizosphere. Collectively, these factors have important implications for the successful use of vegetation to increase the participation of micro-organisms in biotransformation of toxicants at hazardous waste sites.

Biodegradation of pyridine and pyridine derivatives by soil and subsurface microorganisms

Abstract: Large amounts of aromatic compounds are produced by various industries and two thirds of these are heterocyclic chemicals. Compared with the extensive information available on microbial degradation of homocyclic aromatic compounds, relatively little is known on the transformation and biodegradation of heterocyclic chemicals in soil. Recent concerns about the persistence of hazardous pollutants have led to a renewed interest in the biodegradation of heterocyclic compounds. Hence, we investigated the microbial degradation of pyridine and some of its alkylated derivatives under aerobic and anaerobic conditions in groundwater, subsurface sediment, and soil. Results of the investigation revealed that these compounds were degraded predominantly under aerobic conditions and, to a lesser extent, under anaerobic conditions, with nitrate or sulfate serving as electron acceptors. In groundwater polluted with various pyridine derivatives, biodegradation was limited by the absence of oxygen. Therefore, we con...

Coupling transport and biodegradation of VOCs in surface and subsurface soils.

Abstract: Volatile organic chemicals present at Superfund sites preferentially partition into the soil gas and may be available for microbial degradation. A simple mass transfer model for biodegradation for volatile substrates has been developed for the aerobic decomposition of aromatic and aliphatic hydrocarbons. The mass transfer analysis calculates diffusive fluxes from soil gas through water and membrane films and into the cell. This model predicts an extreme sensitivity of potential biodegradation rates to the air-water partition coefficients of the compounds. Aromatic hydrocarbons are removed rapidly while the aliphatic hydrocarbons are much slower by orders of magnitude. Furthermore, oxygen transfer is likely to limit aromatic hydrocarbon degradation rates. The model presents results that cast doubt on the practicality of using methane or propane for the co-metabolic destruction of trichloroethylene in a gas phase bioreactor. Toluene as a primary substrate has better mass transfer characteristics to achieve more efficient trichloroethylene degradation. Hence, in sites where these contaminants coexist, bioremediation could be improved.

The effect of chemical pretreatment on the aerobic microbial degradation of PCB congeners in aqueous systems

Abstract: A series of experiments was conducted to examine the effects of chemical pretreatment on biodegradation of14C-labeled PCB congeners in aqueous systems. Fenton's reagent was used to generate hydroxyl radicals (OH) which were successful in partially oxidizing/transforming otherwise recalcitrant molecules of tetrachlorinated PCB, but had little or no impact on the biodegradation of a monochlorinated congener. Application of Fenton's reagent (1% H2O2, 1 mM FeSO4) followed by inoculation with pure culturesPseudomonas sp, strain LB 400 andAlcaligenes eutrophus, strain H850 resulted in the removal of approximately 38% of 2-chlorobiphenyl and 51% of 2,2′, 4,4′-tetrachlorobiphenyl in the form of14CO2. Comparison of the rate and extent of biodegradation of 2,2′, 4,4′-tetrachlorobiphenyl after the application of Fenton's reagent with the dynamic and final level of radioactivity in the aqueous phase of experimental system suggests two possible means of microbial utilization of tetrachlorinated PCB congener altered by chemical oxidation: (a) consumption of the partially oxidized chemical dissolved in the aqueous phase, and (b) direct microbial attack on the transformed compound, which may still be adhered to the solid surface.

Effect of nonionic surfactant on the degradation of glass-sorbed pcb congeners by integrated chemical-biological treatment

Abstract: A study was conducted on the effect of a nonionic surfactant on the efficiency of the integrated chemical-biological treatment (ICBT) of polychlorinated biphenyls (PCBs) sorbed to the glass walls of the experimental vessels. The addition of surfactant associated with the chemical oxidation was proposed to overcome two limitations of biodegradation of hydrophobic compounds: adsorption to surfaces, and lack of solubility and thus availability to the microorganisms. Two 14C-labeled PCB congeners, 2-chlorobiphenyl and 2,2′,4,4′-tetrachlorobiphenyl, were used as the test compounds. The integrated chemical-biological treatment consisted of sequential applications of Fenton's reagent (5% H2O2, 1 mM FeSO4) at pH 4.0 (with and without non-ionic surfactant Novel II 1412-60) and the inoculation with a mixed culture of Pseudomonas sp., strain LB400, and Alcaligenes eutrophus, strain H850, at pH 8.0. The chemical treatment in the presence of surfactant affected the removal of the congeners bound to the glass surfaces of the experimental test systems. As indicated by high-pressure liquid chromatography analysis, these PCBs were converted to unidentified soluble products that are hypothesized to be partial oxidation products. No parent test compounds were detectable in the system after chemical treatment with or without surfactant. The addition of the mixed culture of PCB-degrading bacteria after completion of chemical treatment in the presence of surfactant resulted in the removal of approximately 45 % of 2-chlorobiphenyl and 32% of 2,2′,4,4′-tetrachlorobiphenyl in the form of 14CO2. This compared to 29% and 23% without the addition of surfactant, respectively. We suggest that the combination of surfactant-induced desorption and chemical oxidation would increase the availability of hydrophobic pollutants for microbial degradation.

Microbial degradation of dibenzothiophene by nocardioides

Abstract: The atmospheric sulfur pollution is one of the major problem world is facing today. Combustion of low quality fossil fuels emitt sulfur dioxide gas. Precombustion desulfurization of fuels is a solution for reduction of atmospheric sulfur pollution. An actinomycetes, Nocardioides sp has been isolated from soil by enrichment culture technigue for the biodegradation of heterocyclic sulfur compound, dibenzothiophene (DBT). Resting cell suspension can degrade DBT with the release of sulfate. The investigation on DBT degradation by Nocardioidea has shown that the organism has got the potential for deaulfurization of petroleum crude.

Microbial degradation of nitrogenous xenobiotics of environmental concern

Abstract: Publisher Summary This chapter focuses on the broad and updated overview of the physiological, biochemical, and genetic basis of biodegradation of nitrogenous compounds by aerobic and anaerobic micro-organisms. Xenobiotic compounds have been used extensively in agriculture as herbicides and insecticides and in the manufacturing industry as surfactants, dyes, drugs, solvents, and so on. Aliphatic and aromatic organic nitrogen compounds represent an important fraction of these chemicals. Even if many of the nitrogenous compounds are highly toxic and often recalcitrant to microbial attack, the microorganisms exposed to these synthetic chemicals have developed the ability to utilize some of them. For every compound that has proven to be biodegradable, the load of environmental pollutants is reduced. The assessment of biodegradability opens the way for the development of microbiological methods for the clean-up of soils and waters, contaminated with synthetic compounds. As bioremediation has its basis in the physiology and ecology of micro-organisms, these methods have to be developed according to the capabilities of these micro-organisms to ensure an optimal performance in those habitats. Moreover, the development of genetic manipulation techniques gives us the possibility to construct new strains with the desired “capabilities” for the degradation of xenobiotics. The employment of these strains could enhance the possibilities to decontaminate polluted environments.

Microbial biodegradation of the herbicide 2,4-D in soils and subsurface sediments

Abstract: Much of the row crop production agriculture in the Midwest occurs on soils developed from glacial till, but little research has addressed herbicide biodegradation in subsurface till. This study investigated the ability of indigenous microorganisms to mineralize the herbicide 2,4-D (2,4-dichlorophenoxyacetic acid) at sites in Iowa and Indiana. Microorganisms were able to mineralize 2,4-D, with rates of mineralization ranging from 0.02 to 1.0% d"1 over the first 30 d. Rates of mineralization and total 2,4-D mineralized generally declined with depth in these profiles. Totai2,4-D mineralized ranged from 31 to 42% in surface soils and 2 to 47% in subsurface sediments between 150 to 180 d after addition. Populations of 2,4-D-degraders in soils and glacial sediments ranged from non-detectable to 59,000 degraders g·1 soil. The adaptation of 2,4-D metabolizing microorganisms in the subsurface impacted the mineralization rates and totai2,4-D mineralized. Sandy subsurface sediments ranging in depth from 2.9 to 3.5 m from one Indiana core exhibited greater mineralization rates before and after adaptation with more extensive 2,4-D mineralization than till from approximately 1 m depth. Lag periods in these two subsurface samples ranged from 42 to 80 d prior to increased mineralization. The population of 2,4-D-degraders in these deeper sandy sediments were greater than the populations in the overlying till. INTRODUCTION Ground water pollution by agricultural chemicals is a concern because ground water supplies a significant portion of the drinking water used in the United States (Hallberg, 1986). The U.S. Environmental Protection Agency (EPA) found pesticide detections in 23.5% of drinking water wells tested in 1992. Normal field usage of pesticides was suspect for 20.8% of all wells with detections (Jacoby, 1992). Atrazine, alachlor, and cyanazine movement from glacial till soils and agricultural watershed

Composting process and device for organic matter, especially wastes

Abstract: of EP0633235A process is intended for composting organic materials (biodegradation material), in particular waste, for example domestic waste or waste which resembles domestic waste. The biodegradation material is introduced into a sealed container and subjected to microbial degradation while passing in oxygen. A mixture of pure oxygen and waste air is furthermore added to the biodegradation material. To improve such a process, the CO2 in the waste air is returned to the biodegradation material. The water in the waste air which emanates from the biodegradation material is removed.

Chemical Reactions of Organics

Abstract: Abiotic (chemical) reactions of organic pollutants in soils and aquifers are important for several reasons. On the one hand, unlike microbial degradation, chemical transformation of a given pollutant does never lead to the mineralization of the compound. In fact, numerous reactions, particularly redox reactions of organic pollutants, may lead to products that are of considerable (eco)toxicological concern (Macalady et al., 1986). On the other hand, in certain cases, products may be formed that are more easily biodegraded, or that may undergo reactions with soil constituents to form so-called «bound residues» (Bollag, 1992). Furthermore, in heavily contaminated subsurface environments, chemical reactions involving organic pollutants may have a significant impact on biogeochemical processes, in that species are formed that may influence microbial activity (Heijman et al., 1994). Therefore, knowledge on the mechanisms and rates of chemical reactions of organic pollutants in the subsurface are of great interest, both for assessing the risks and hazards associated with pollution of soils and aquifers by organic compounds, as well as for in-situ, on-site or off-site remediations of contaminated sites.

Effects of low-surfactant concentration of the bioavailability and enhanced biodegradation of volatile organic compounds

Abstract: Volatile organic compounds (VOCs), such as toluene and carbon tetrachloride, are common contaminates at several DOE sites. Bioremediation can be enhanced by increasing the contaminant solubility, thus making it more bioavailable for microbial degradation. A synthetic non-ionic surfactant (Tween-80) was used to enhance the solubilization of toluene in an abiotic aqueous systems. Surfactant concentrations were tested in a range from above (0.1%), at (0.03%), and below (0.01%) the critical micelle concentration (CMC). Gas chromatography measured the relative concentrations of toluene in the headspace before and after surfactant treatment. Results indicate that the partitioning is independent of surfactant concentration and in fact additions at the CMC (0.03%) were slightly more effective than those concentrations above and below. Laboratory experiments have demonstrated that surfactant concentrations of 5% inhibit the growth of a consortium capabe of carbon tetrachloride degradation, and consequently inhibit bioremediation. This evidence further supports the conclusion that {open_quote}more is not necessarily better{close_quote} when dealing with surfactants and bioremediation activities.

Anaerober Abbau aromatischer Verbindungen im Untergrund : Abschätzung der Grenzen und Möglichkeiten

Abstract: The influence of variable redox conditions on the biodegradability of selected aromatic compounds was investigated. A laboratory scale filter system was built simulating aerobic and anaerobic conditions during bank filtration and underground passage. The testsubstances used were phenol, as rather simple aromatic compound, its monochlorinated derivatives and the three phenoxyacetic acid herbicides 2,4-D, 2,4,5-T and MCPA. With these substances the effect of different chemical structures in general and of the specific influence of chlorine substitution on biodegradability could be studied. The use of natural anaerobic and aerobic groundwater and of different underground material allowed us to assess other factors that affect microbial degradation processes. All substances could be degraded in at least one of the experimental settings, but required microbial adaptation. The duration of the lag-phase is mainly influenced by the redox range, the underground material and the chemical structure of the test component. Anaerobic processes proved to be more time-consuming than those in the presence of molecular oxygen. Filters filled with gravel provided more favourable conditions for microbial activity which led to shorter lag-phases. Microbial adaptation to chlorinated compounds seemed to be more complicated and required a longer period.

Microbial Degradation of Quinoline in Heavy Oil.

Abstract: For the purpose of removing nitrogen atoms from heavy oil by microbial procedures, the first approach was made to obtain microorganisms capable of degrading quinoline as the N-containing model compound by enrichment culture. One iso-late, identified as Pseudomonas putida Q26, was chosen for further study. The degrada-tion of quinoline by this strain yielded initially 2-hydroxyquinoline and then 8-hydroxycoumarin, resulting finally in the complete degradation. This strain was able to degrade quinoline and a few methylquinoline in a complex basic fraction of coal-liquids. It was observed that microbial treatment decreased nitrogen content of the basic fraction of hydrogenated recycle solvent derived from Taiheiyo coal.