Showing papers on "Microbial biodegradation published in 1991"

Microbial populations and hydrocarbon biodegradation potentials in fertilized shoreline sediments affected by the T/V Exxon Valdez oil spill.

Abstract: The effort of clean up the T/V Exxon Valdez oil spill in Prince William Sound, Alaska, included the use of fertilizers to accelerate natural microbial degradation of stranded oil. A program to monitor various environmental parameters associated with this technique took place during the summer of 1990. Microbiological assays for numbers of heterotrophic and oil-degrading microbes and their hydrocarbon mineralization potentials were performed in support of this program. Fertilizer addition resulted in higher hexadecane and phenanthrene mineralization potentials on treated plots than on untreated reference plots. Microbial numbers in treated and reference surface sediments were not significantly different immediately after the first nutrient application in May 1990. However, subsurface sediments from treated plots had higher numbers of hydrocarbon degraders than did reference sediments shortly after treatment. The second application of fertilizer, later in summer, resulted in surface and subsurface increases in numbers of hydrocarbon degraders with respect to reference sediments at two of the three study sites. Elevated mineralization potentials, coupled with increased numbers of hydrocarbon degraders, indicated that natural hydrocarbon biodegradation was enhanced. However, these microbiological measurements alone are not sufficient to determine in situ rates of crude oil biodegradation.

Factors affecting the microbial degradation of phenanthrene in soil.

Abstract: Because phenanthrene was mineralized more slowly in soils than in liquid media, a study was conducted to determine the environmental factors that may account for the slow biodegradation in soil. Mineralization was enhanced by additions of phosphate but not potassium, and it was reduced by additions of nitrate. Aeration or amending the soil with glucose affected the rate of mineralization, although not markedly. Phenanthrene was sorbed to soil constituents, the extent of sorption being directly related to the percentage of organic matter in the soil. Soluble phenanthrene was not detected after addition of the compound to a muck soil. The rate of mineralization was slow in the organic soil and higher in mineral soils with lower percentages of organic matter. We suggest that sorption by soil organic matter slows the biodegradation of polycyclic aromatic hydrocarbons that are otherwise readily metabolized.

Factors affecting the microbial degradation of phenanthrene in soil. (Reannouncement with new availability information)

Abstract: Because phenanthrene was mineralized more slowly in soils than in liquid media, a study was conducted to determine the environmental factors that may account for the slow biodegradation in soil. Mineralization was enhanced by additions of phosphate but not potassium, and it was reduced by additions of nitrate. Aeration or amending the soil with glucose affected the rate of mineralization, although not markedly. Phenanthrene was sorbed to soil constituents, the extent of sorption being directly related to the percentage of organic matter in the soil. Soluble phenanthrene was not detected after addition of the compound to a muck soil. The rate of mineralization was slow in the organic soil and higher in mineral soils with lower percentages of organic matter. We suggest that sorption by soil organic matter slows the biodegradation of polycyclic aromatic hydrocarbons that are otherwise readily metabolized.

Bioventing soils contaminated with petroleum hydrocarbons

Abstract: Bioventing combines the capabilities of soil venting and enhanced bioremediation to cost-effectively remove light and middle distillate hydrocarbons from vadose zone soils and the groundwater table. Soil venting removes the more volatile fuel components from unsaturated soil and promotes aerobic biodegradation by driving large volumes of air into the subsurface. In theory, air is several thousand times more effective than water in penetrating and aerating fuel-saturated and low permeability soil horizons. Aerobic microbial degradation can mitigate both residual and vapor phase hydrocarbon concentrations. Soil venting is being evaluated at a number of U.S. military sites contaminated with middle distillate fuels to determine its potential to stimulate in situ aerobic biodegradation and to develop techniques to promote in situ vapor phase degradation. In situ respirometric evaluations and field pilot studies at sites with varying soil conditions indicate that bioventing is a cost-effective method to treat soils contaminated with jet fuels and diesel.

Photochemically enhanced microbial degradation of environmental pollutants

Abstract: This invention provides for improved methods of biodegradation of environmental pollutants. The invention specifically provides for the simultaneous treatment of the pollutants in a contaminated medium with ultraviolet radiation and lignin-degrading fungi. The preferred fungus is the white rot fungus Phanerochaete chrysosporium ATCC 64046. The fungi are discontinuously contacted with the mass of a contaminated medium. When removed from the mass of contaminated medium, the fungi and adhering contaminated medium are simultaneously exposed to the ultraviolet radiation. The combination of fungal enzymes and ultraviolet radiation enhances the rates of degradation beyond that expected for either of the treatments alone.

Methodological modifications for accurate and efficient determination of contaminant biodegradation in unsaturated calcareous soils.

Abstract: Many techniques for quantifying microbial biodegradation of 14C-labeled compounds use soil-water slurries and trap mineralization-derived 14CO2 in solution wells suspended within the incubation flasks. These methods are not satisfactory for studies of arid-region soils that are highly calcareous and unsaturated because (i) slurries do not simulate unsaturated conditions and (ii) the amount of CO2 released from calcareous soils exceeds the capacity of the suspended well. This report describes simple, inexpensive methodological modifications for quantifying microbial degradation of [14C]benzene and 1,2-dichloro[U-14C]ethane in calcareous soils under unsaturated conditions. Soils at 50% water holding capacity were incubated with labeled contaminants for periods up to 10 weeks, followed by acidification of the soil and trapping of the evolved CO2 in a separate container of 2 N NaOH. The CO2 was transferred from the incubation flask to the trap solution by a gas transfer shunt containing activated charcoal to remove any volatilized labeled organics. The amount of 14CO2 in the trap solution was measured by scintillation counting (disintegrations per minute). The method was tested by using two regional unamended surface soils, a sandy aridisol and a clay-rich riparian soil. The results demonstrated that both [14C]benzene and 1,2-dichloro[U-14C]ethane were mineralized to release substantial amounts of 14CO2 within 10 weeks. Levels of mineralization varied with contaminant type, soil type, and aeration status (anaerobic vs. aerobic); no significant degradation was observed in abiotic control samples. Methodological refinements of this technique resulted in total 14CO2 recovery efficiency of approximately 90%.

Microbial degradation of bitumen

Abstract: A blown bitumen Mexphalte R 90/40 with a high content of saturated hydrocarbons was degraded by several microorganisms to the same extent. In batch cultures ofSaccharomycopsis lipolytica, maximal biodegradation was estimated to be about 9% w/w, 3.2·10−3 g/cm2 and 3.1·10−3 cm of degraded bitumen. The Mexphalte R 90/40 degradation rate was closely coupled to biofilm formation. The microbial activity concerned predominantly the oxidation of saturated hydrocarbons. A direct distillation bitumen 80/100 with a low content of saturated hydrocarbons and a high content of aromatic hydrocarbons and resins was more resistant to biodegradation.

Biodegradation of bitumen used for nuclear waste disposal

Abstract: Studies have been carried out to test microbial degradation of bitumen used for encapsulating radioactive waste in Sweden. Microorganisms have been isolated that degrade bitumen. In ong-term tests under conditions simulating those in the silo part of the final repository for low-and intermediate-level radioactive waste, both aerobic and anaerobic degradation of bitumen has been found, equivalent to 0.6–1.5 μmoles CO2/month·mg bitumen and 1.1–1.5 μmoles CO2/month·mg bitumen, respectively.

Developing strategies for PAH and TCE bioremediation

Abstract: Bioremediation is the controlled use of microbes, commonly bacteria and fungi, to reclaim soil and water contaminated with substances that are deleterious to human health and the environment. The organisms used often naturally inhabit the polluted matrix; however, they may inhabit a different environment and be used as seed organisms because of their ability to degrade a specific class of substances. It is because of the wide diversity of microbial metabolic potential that bioremediation is possible. Polyaromatic hydrocarbons (PAHs) are organic compounds that are ubiquitous in the environment. They are present in fossil fuels and are formed during the incomplete combustion of organic material. PAHs exhibit low volatility and low aqueous solubility. As the molecular weight of these compounds increases, there is an exponential decrease in solubility and volatility. PAHs tend to adsorb onto soils and sediments because of their hydrophobic character, which is an intrinsic function of molecular size. The microbial degradation of individual PAHs by pure cultures and mixed populations occurs under a wide range of soil types and environmental conditions. Generally, the factors having the greatest influence on PAH biodegradation rates are soil moisture content, pH, inorganic nutrients present, PAH loading rates, initial PAH concentrations, and themore » presence of an acclimated microbial population. Feasibility studies are essential for developing a bioremediation strategy and are performed in a phased testing program that is designed to accomplish a number of objectives. These objectives include establishing an indigenous microbial population that will degrade specific contaminants, defining the rate-limiting factors for enhanced PAH degradation and the optimal treatment in terms of rates and cleanup levels attainable, and developing design parameters for field operations.« less

Physiology of biodegradative microorganisms

Abstract: Physiology of aliphatic hydrocarbon-degrading microorganisms.- Microbial metabolism of monoterpenes - recent developments.- Formation and physiological role of biosurfactants produced by hydrocarbonutilizing microorganisms. Biosurfactants in hydrocarbon utilization.- Microbial degradation of chelating agents used in detergents with special reference to nitrilotriacetic acid (NTA).- Physiology and performance of thermophilic microorganisms in sewage sludge treatment processes.- Enzymology of cellulose degradation.- Biodegradation of lignin-carbohydrate complexes.- Physiology of microbial degradation of chitin and chitosan.- The biodegradation of aromatic hydrocarbons by bacteria TargetID.- Degradation of halogenated aromatic compounds.

Volatilization of mercury compounds and utilization of various aromatic compounds by a broad-spectrum mercury resistant Bacillus pasteurii strain

Abstract: Aquatic ecosystems may receive aromatic compounds through various routes These compounds can cause cancerous diseases in aquatic animals and enhance mutagenicity of the sediments The persistence of aromatic compounds deposited in sediments is affected by microbial degradation Plasmid-determined mercuric and organomercurial resistance in microorganisms has also been studied by several workers Utilization of various aromatic compounds as sole sources of carbon by an Hg-resistant bacterial strain has not been reported The author isolated a broad-spectrum Hg-resistant Bacillus pasteurii strain DR{sub 2} which could volatilize different mercury compounds and utilize various aromatic compounds as sole sources of carbon This strain preferentially utilized benzene in a medium containing both glucose and benzene To their knowledge, until recently there has been no report on preferential utilization of other compounds, particularly an aromatic compound to glucose in a mixture

Ch. R-8 Anaerobic Microbial Degradation of Aromatic Hydrocarbons

Abstract: In the last decade, it has become widely recognized that nonoxygenated aromatic hydrocarbons undergo microbial transformations under anoxic conditions. The compounds which are transformed include mononuclear and polynuclear homocyclic, nitrogen heterocyclic, and sulfur heterocyclic aromatic hydrocarbons. The conditions conducive to the transformations range from denitrifying and iron(III)-reducing, to sulfate-reducing and fermentative/methanogenic. Anaerobic or facultatively anaerobic bacteria capable of degrading aromatic hydrocarbons have been enriched and, in some cases, isolated from various environments, both pristine and contaminated with pollutant mixtures containing aromatic hydrocarbons: anaerobic sludge, soil, freshwater sediments, estuarine sediments, marine sediments, and ground water aquifers. At this point, it is maybe premature to conclude that such bacteria are ubiquitous and that they can all degrade a very broad range of hydrocarbons; however, they are being detected in numerous environmental samples, and their activity can be demonstrated in-situ , e.g. in ground water aquifers contaminated by petroleum or creosote. Once the nutritional requirements, physiology and ecology of these microorganisms are well understood, they will represent a considerable potential to be tested and used in microbially-enhanced oil recovery.

Biodeterioration of Fuels

Abstract: The biodeterioration of hydrocarbons only occurs when water is present, the active deteriogens growing either at the oil-water interface or in the aqueous phase. It is primarily trophic biodeterioration in which the hydrocarbon is used as a carbon and energy source and as such is synonymous with biodegradation. The only difference is that biodeterioration is biodegradation in the wrong place. Thus microbial degradation of fuel in the wing tanks of an aircraft is biodeterioration but the same process occurring in an oil slick is biodegradation. Biodegradation of hydrocarbons is a strictly aerobic process and degradation cannot occur under anaerobic conditions. This is because hydrocarbons, unlike carbohydrates, contain no oxygen. Hence those processes which take place during the fermentation of glucose, whereby the oxidised product following energy release itself becomes the ultimate hydrogen and electron acceptor to form alcohol, cannot occur. Paradoxically, this does not mean that biodeterioration will not take place under anaerobic conditions; trophic degradation can and does occur providing an alternative electron acceptor such as nitrate or sulphate is present. Whilst primary deterioration is trophic there may be secondary forms of spoilage which arise from microbial growth such as the migration of water droplets into the fuel, the accumulation of microbial slimes in the fuel and souring by hydrogen sulphide produced by the sulphate reducing bacteria.

Microbial Degradation of Mixtures of Aromatic Compounds at Low Concentrations under Aerobic Conditions

Abstract: This study has shown that microorganisms can adapt to degrade mixtures of aromatic pollutants at relatively high rates in the μg/1 concentration range. The following compounds were studied under aerobic conditions in an attached biofilm system: phenol, methylphenols, chlorophenols, nitrophenol and aromatic hydrocarbons. At concentrations below 20-100 μg/1 the degradation is typically controlled by a first order kinetics. The first order surface removal rate constants were surprisingly similar for the different aromatic compounds. A literature search has revealed that kinetic data as presented here are very scarce.

The microbial degradability of aniline in river water and an attempt to use the level of the biodegradability as an indicator of water pollution

Abstract: The microbial degradation of 6 chemicals in river water samples was tested using the cultivation method (Handai Method). Since aniline showed a regional difference, its microbial degradability was investigated in detail using the modified Handai Method to evaluate the possibility of its indication of water pollution caused by organic substances. The results were as follows. n-Butylacrylate was easy biodegradable and Diazinon was degraded to some degree. The microbial degradability of aniline in river water was different. The biodegradation rate increased slowly in unpolluted river water from rural areas, but increased rapidly in polluted river water from urban areas. Additionally, the biodegradation of aniline in these test samples was assumed to tend to be slightly higher in summer than in winter. This suggested that the microbial degradability of aniline in urban river water could be an indicator of water pollution because of the close correlation with the degree of water quality.

Microbial degradation of alkylbenzenes under sulfate-reducing and methanogenic conditions. Final report, May 89-Apr 91

Abstract: Aquifer solids and soils obtained from various hydrocarbon-contaminated sites were used to investigate the ability of indigenous microorganisms to degrade monoaromatic hydrocarbons under strictly anaerobic conditions. In anaerobic microcosms inoculated with fuel-contaminated soil from the Patuxent River site, toluene degradation occurred concomitantly with sulfate reduction and ferric iron reduction. Similar results were obtained with suspended enrichments derived from the microcosms. Stoichiometric data and other observations suggested that sulfate reduction was closely linked to toluene degradation, whereas iron reduction was a secondary, potentially abiotic, reaction between ferric iron and biogenic hydrogen sulfide. The presence of millimolar concentrations of amorphous Fe(OH)3 in Patuxent River microcosms and enrichments either greatly facilitated the onset of toluene degradation or accelerated the rate once degradation had begun. Fermentative/methanogenic microcosms and enrichments that degraded toluene and o-xylene without added exogenous electron acceptors (except CO2) were developed from creosote-contaminated Pensacola samples. The microcosms initially underwent an acclimation lag of several months; however, once the degradation of aromatic hydrocarbons was initiated, it proceeded at a relatively rapid rate, and it was complete (resulting in mineralization to CO2 and CH4). Benzene, ethylbenzene, and p-xylene were not degraded.

Biodegradation of nitriles and cyanide.

Abstract: The microbial degradation of numerous compounds has been studied and the biochemical pathways and mechanisms of enzyme action have been elucidated particularly with respect to pure cultures of bacteria. This research has been extremely valuable but to date industrial application of the knowledge has been somewhat limited. However, public awareness of the environment and governmental pressure in the form of the recent “Green Bill” has stimulated industry into taking measures to reduce the discharge of compounds likely to cause environmental problems. Biodegradation can play a significant role as, when it is achievable, it is by far the most economic method of treatment for removal of pollutants from a waste effluent.