Showing papers on "Microbial biodegradation published in 1990"

Enhanced biodegradation of pesticides in the environment.

Abstract: Pesticides in the Soil Microbial Ecosystems Effects of Long-Term Phenoxyalkanoic Acid Herbicide Field Applications on the Rate of Microbial Degradation Enhanced Carbamothioate Herbicide Degradation: Research in Nebraska Enhanced Biodegradation of Carbamothioate Herbicides in South Carolina Enhanced Biodegradation of Dicarboximide Fungicides in Soil Enhanced Biodegradation of Insecticides in Midwestern Corn Soils Enhanced Degradation of Insecticides in Soil: Factors Influencing the Development and Effects of Enhanced Microbial Activity Enhanced Degradation of S-Ethyl N,N-Dipropylcarbamothioate in Soil by an Isolated Soil Microorgnism The Role of Fungi and Bacteria in the Enhanced Degradation of Fungicide Carbendazim and the Herbicide Diphenamid Influence of Pesticide Metabolites on the Development of Enhanced Biodegradation Molecular Genetics of Pesticide Degradation by Soil Bacteria Response of Microbial Populations to Carbofuran in Soils Enhanced for Its Degradation Adaptation of Microorganisms in Subsurface Environments and its Significance to Pesticide Degradation Microbial Adaptation in Aquatic Ecosystems Evaluation of Some Methods for Coping with Enhanced Biodegradation of Soil Insecticides Systems Allowing Continued Use of Carbmothioate Herbicides Despite Enhanced Biodegradation Cultural Practices and Chemicals That Affect the Persistence of Carbamothioate Herbicides in Soil Spectrophotometric Methodologies for Predicting and Studying Enhanced Degradation Enhancing Biodegradation for Detoxification of Herbicide Waste in Soil Implications of Enhanced Biodegradation for the Use and Study of Pesticides in the Soil Environment

Fate of petroleum hydrocarbons and toxic organics in Louisiana coastal environments

Abstract: Numerous potentially toxic compounds are entering Louisiana’s inshore and nearshore coastal environments. To a large degree there is insufficient information for predicting the fate and effect of these materials in aquatic environments. Studies documenting the impact of petroleum hydrocarbons entering Louisiana coastal wetlands are summarized. Also included are research findings on factors affecting the persistence of petroleum hydrocarbons and other toxic organics (pentachlorophenol (PCP), 2,4-dichlorophenoxyacetic acid (2,4-D), creosote, etc.) in sediment-water systems. Sediment pH and redox conditions have been found to play an important role in the microbial degradation of toxic organics. Most of the hydrocarbons investigated degrade more rapidly under high redox (aerobic) conditions although there are exceptions (e.g., 1,1,1-trichloro-2,2-bis(4-chlorophenyl) (DDT) and polychlorobiphenyls (PCBs)). Some of these compounds, due to their slow degradation in anaerobic sediment, may persist in the system for decades.

Fate of petroleum hydrocarbons and toxic organics in Louisiana coastal environments

Abstract: Numerous potentially toxic compounds are entering Louisiana’s inshore and nearshore coastal environments To a large degree there is insufficient information for predicting the fate and effect of these materials in aquatic environments Studies documenting the impact of petroleum hydrocarbons entering Louisiana coastal wetlands are summarized Also included are research findings on factors affecting the persistence of petroleum hydrocarbons and other toxic organics (pentachlorophenol (PCP), 2,4-dichlorophenoxyacetic acid (2,4-D), creosote, etc) in sediment-water systems Sediment pH and redox conditions have been found to play an important role in the microbial degradation of toxic organics Most of the hydrocarbons investigated degrade more rapidly under high redox (aerobic) conditions although there are exceptions (eg, 1,1,1-trichloro-2,2-bis(4-chlorophenyl) (DDT) and polychlorobiphenyls (PCBs)) Some of these compounds, due to their slow degradation in anaerobic sediment, may persist in the system for decades

Involvement of fungi and bacteria in enhanced and nonenhanced biodegradation of carbendazim and other benzimidazole compounds in soil.

Abstract: The relationship between chemical structure and the enhancement of microbial degradation of three benzimidazole compounds in soil was determined. Preapplication of methyl benzimidazole-2-ylcarbamat...

In situ bioremediation of contaminated aquifers and subsurface soils.

Abstract: Bioremediation, the use of microorganisms to detoxify and degrade hazardous wastes, is an emerging in situ treatment technology for the remediation of contaminated aquifers and subsurface soils This technology depends upon the alteration of the physical/chemical conditions in the subsurface environment to optimize microbiological activity As such, successful bioremediation depends not only upon an understanding of microbial degradation processes, but also upon an understanding of the complex interactions that occur between the contaminants, the subsurface environment, and the indigenous microbial populations at each site At present, these interactions are poorly understood Site‐specific evaluation and design therefore are essential for bioremediation In this paper, we review microbiological, hydrological, and geochemical factors that should be considered in evaluating the appropriateness of bioremediation for hazardous waste‐contaminated aquifers and subsurface soils

Biodegradation of Dinoseb (2-sec-Butyl-4,6-Dinitrophenol) in Several Idaho Soils with Various Dinoseb Exposure Histories.

Abstract: We examined the ability of native microorganisms in various Idaho soils to degrade dinoseb and studied some physical and chemical soil characteristics which might affect the biodegradation process. Dinoseb biodegradation rates were higher in silt-loam soils than in loamy-sand soils. Biodegradation rates were not influenced by previous exposure of the soils to dinoseb. Bacterial numbers, measured by standard plate counts on soil extract agar, were the best predictors of biodegradation rates, accounting for 53% of the variability between soils. Soil nitrate-N inhibited dinoseb biodegradation and accounted for 39% of the variability. Sorption of dinoseb to soil surfaces also appeared to influence biodegradation rates. No other soil parameter contributed significantly to the variability in biodegradation rates. Persistence of dinoseb in one soil was due to inhibition of biodegradation by nitrate, while in another soil persistence appeared to be due to lack of native degradative microorganisms.

Anaerobic microbial degradation of acridine and the application of remote fiber spectroscopy to monitor the transformation process

Abstract: Anaerobic microbial transformation of a polynuclear nitrogen heterocycle, acridine, was studied in laboratory microcosms with three different inocula: a stabilized, mixed culture growing on ferulic acid that was originally enriched from anaerobic sewage sludge, and sulfate-reducing and methanogenic aquifer materials from two sites at a groundwater aquifer contaminated by landfill leachate Acridine degradation was investigated under methanogenic, denitrifying and sulfate-reducing conditions at concentrations of 1 to 6 μg/ml Substrate degradation was followed using two standard analytical techniques (HPLC and GC-MS) and a new, in situ remote fiber spectroscopic (RFS) technique This RFS was used successfully to follow changes in concentration of acridine with time, which indicates the technique has a significant potential for monitoring the degradation process in environmental media Acridine was degraded extensively in one to three weeks under each of the conditions studied A range of heterocyclic, homocyclic aromatic and aliphatic intermediates was identified by GC-MS analyses On the basis of these compounds, a tentative route of anaerobic acridine transformation is proposed that begins with oxidation and proceeds through the common degradative route for oxidized aromatic compounds

Biotransformation of alkyl and aryl carbonates. Microbial degradation.

Abstract: An enriched mixed culture was successfully grown on model alkyl and aryl carbonates. These compounds were degraded by microorganisms at different rates. P-Chlorophenyl-2-octyl carbonate and p-nitrobenzyl-2-octyl carbonate were metabolized through the formation of p-chlorophenol and p-nitrobenzyl alcohol respectively. A strain of Acinetobacter calcoaceticus isolated from the mixed culture utilized phenyl-2-octyl carbonate by an intracellular hydrolase to phenol and 2-octanol which were further metabolized.

Petroleum and Chlorinated Hydrocarbon Analysis in Support of In Vitro Studies of Natural Anaerobic and Aerobic Microbial Degradation of Xenobiotics in Contaminated Groundwater and Soil

Abstract: This program investigated in situ biological degradation as a remedial treatment technique at a United States Air Force Base in Texas. Soil and groundwater samples from the site were characterized regarding microbial populations and presence or absence of priority pollutant xenobiotics and petroleum hydrocarbon components. Time-series analyses of replicate nutrient-amended microcosms after approximately 1, 25, 50 and 100 days permitted aerobic and anaerobic degradation rate evaluation. Microcosm integrity was demonstrated throughout the experiment by observing appropriate dissolved oxygen, pH, oxidation/reduction potential, and sterile/viable conditions. Gas chromatographic analysis and ratios of straight-chain and isoprenoid components clearly demonstrated that aerobic conditions were preferred for degradation of aliphatic and aromatic petroleum hydrocarbons. Electron capture gas chromatographic analyses and purge-and-trap gas chromatographic/mass spectrometric analyses of lower molecular weight...

Effect of Microbial Surfactants on Hydrocarbon Mineralization in Different Model Systems of Soil

Abstract: By way of microbial degradation of hydrocarbons metabolites may be formed that are more toxic than the substrate hydrocarbon. For example undecanoic acid, which may be formed from undecane, inhibits the elongation of fatty acids in various bacteria (1). Therefore it is necessary to study the effect of microbial surfactants not only on the degradation of hydrocarbons by an original soil population but also on the extent of mineralization. In the first model system, a stirred reactor with 10% soil content of an original soil population, oil degradation capacity could be increased from 25,7 to 46,5 g hydrocarbon mixture per kg soil dry weight and day by lowering the interfacial tension caused by the sophorose lipids added (2). The degradation capacity for a fuel oil also increased from 25,3 to 32,8 g hydrocarbon per kg soil dry weight and day, when sophorose lipids were added. About 90% of this oil could be degraded related to 99% of the defined hydrocarbon mixture (3). Yet after elimination of the model oil the chemical oxygen demand was still about 27% of the initial theoretical value (2). Therefore we examined the extent of mineralization by calculations based on waste air analysis in the stirred reactor with 10% soil content or on hydrogen peroxide usage in fixed bed columns of sieved soil percolated with a mineral salts medium with sufficient hydrogen peroxide (4).

Microbial degradation of multiple halogenated aromatic compounds.

Abstract: Bacteria of the genus Brevibacterium which are able to utilise dibenzofuran and 2-bromodibenzofuran as sole source of carbon are employed for the biological cleanup of soils, sediments and leachates containing halodibenzodioxin and -dibenzofuran. Microorganism strains of this type are used for the microbial degradation of polyhalogenated polycyclic aromatic compounds, especially of halodibenzo-p-dioxins and dibenzofurans. It is possible to add monocyclic aromatic compounds, preferably phenol or toluene, as inducers.

Soil Venting: Removal and Biodegradation of Hydrocarbons from Polluted Soil

Abstract: Experience from a field test using forced ventilation for in-situ remediation of gasoline contaminated soil is being reported. The test shows that it is possible to establish an advective air flow through sandy soil, and within a period of 63 days remove a substantial amount of gasoline. Preliminary laboratory tests show that forced ventilation will be able to accelerate the microbial biodegradation of the hydrocarbons that are not physically removed by the air. The need for adding nutrients has yet to be established.