Showing papers on "Microbial biodegradation published in 2004"

Atmospheric nitrate deposition and the microbial degradation of cellobiose and vanillin in a northern hardwood forest

Abstract: Human activity has increased the amount of N entering terrestrial ecosystems from atmospheric NO3− deposition. High levels of inorganic N are known to suppress the expression of phenol oxidase, an important lignin-degrading enzyme produced by white-rot fungi. We hypothesized that chronic NO3− additions would decrease the flow of C through the heterotrophic soil food web by inhibiting phenol oxidase and the depolymerization of lignocellulose. This would likely reduce the availability of C from lignocellulose for metabolism by the microbial community. We tested this hypothesis in a mature northern hardwood forest in northern Michigan, which has received experimental atmospheric N deposition (30 kg NO3−–N ha−1 y−1) for nine years. In a laboratory study, we amended soils with 13C-labeled vanillin, a monophenolic product of lignin depolymerization, and 13C-labeled cellobiose, a disaccharide product of cellulose degradation. We then traced the flow of 13C through the microbial community and into soil organic carbon (SOC), dissolved organic carbon (DOC), and microbial respiration. We simultaneously measured the activity of enzymes responsible for lignin (phenol oxidase and peroxidase) and cellobiose (β-glucosidase) degradation. Nitrogen deposition reduced phenol oxidase activity by 83% and peroxidase activity by 74% when compared to control soils. In addition, soil C increased by 76%, whereas microbial biomass decreased by 68% in NO3− amended soils. 13C cellobiose in bacterial or fungal PLFAs was unaffected by NO3− deposition; however, the incorporation of 13C vanillin in fungal PLFAs extracted from NO3− amended soil was 82% higher than in the control treatment. The recovery of 13C vanillin and 13C cellobiose in SOC, DOC, microbial biomass, and respiration was not different between control and NO3− amended treatments. Chronic NO3− deposition has stemmed the flow of C through the heterotrophic soil food web by inhibiting the activity of ligninolytic enzymes, but it increased the assimilation of vanillin into fungal PLFAs.

Biodegradability of chlorinated solvents and related chlorinated aliphatic compounds

Abstract: The biodegradability of chlorinated methanes, chlorinated ethanes, chlorinated ethenes, chlorofluorocarbons (CFCs), chlorinated acetic acids, chlorinated propanoids and chlorinated butadienes was evaluated based on literature data. Evidence for the biodegradation of compounds in all of the compound categories evaluated has been reported. A broad range of chlorinated aliphatic structures are susceptible to biodegradation under a variety of physiological and redox conditions. Microbial biodegradation of a wide variety of chlorinated aliphatic compounds was shown to occur under five physiological conditions. However, any given physiological condition could only act upon a subset of the chlorinated compounds. Firstly, chlorinated compounds are used as an electron donor and carbon source under aerobic conditions. Secondly, chlorinated compounds are cometabolized under aerobic conditions while the microorganisms are growing (or otherwise already have grown) on another primary substrate. Thirdly, chlorinated compounds are also degraded under anaerobic conditions in which they are utilized as an electron donor and carbon source. Fourthly, chlorinated compounds can serve as an electron acceptor to support respiration of anaerobic microorganisms utilizing simple electron donating substrates. Lastly chlorinated compounds are subject to anaerobic cometabolism becoming biotransformed while the microorganisms grow on other primary substrate or electron acceptor. The literature survey demonstrates that, in many cases, chlorinated compounds are completely mineralised to benign end products. Additionally, biodegradation can occur rapidly. Growth rates exceeding 1 d-1 were observed for many compounds. Most compound categories include chlorinated structures that are used to support microbial growth. Growth can be due to the use of the chlorinated compound as an electron donor or alternatively to the use of the chlorinated compound as an electron acceptor (halorespiration). Biodegradation linked to growth is important, since under such conditions, rates of degradation will increase as the microbial population (biocatalyst) increases. Combinations of redox conditions are favorable for the biodegradation of highly chlorinated structures that are recalcitrant to degradation under aerobic conditions. However, under anaerobic conditions, highly chlorinated structures are partially dehalogenated to lower chlorinated counterparts. The lower chlorinated compounds are subsequently more readily mineralized under aerobic conditions.

Predicting the biodegradation products of perfluorinated chemicals using CATABOL

Abstract: Perfluorinated chemicals (PFCs) form a special category of organofluorine compounds with particularly useful and unique properties. Their large use over the past decades increased the interest in the study of their environmental fate. Fluorocarbons may have direct or indirect environmental impact through the products of their decomposition in the environment. It is a common knowledge that biodegradation is restricted within non-perfluorinated part of molecules: however, a number of studies showed that defluorination can readily occur during biotransformation. To evaluate the fate of PFCs in the environment a set of principal transformations was developed and implemented in the simulator of microbial degradation using the catabolite software engine (CATABOL). The simulator was used to generate metabolic pathways for 171 perfluorinated substances on Canada's domestic substances list. It was found that although the extent of biodegradation of parent compounds could reach 60%, persistent metabolites could be formed in significant quantities. During the microbial degradation a trend was observed where PFCs are transformed to more bioaccumulative and more toxic products. Perfluorooctanoic acid and perfluorooctanesulfonate were predicted to be the persistent biodegradation products of 17 and 27% of the perfluorinated sulphonic acid and carboxylic acid containing compounds, respectively.

Pathway Dependent Isotopic Fractionation during Aerobic Biodegradation of 1,2-Dichloroethane

Abstract: 1,2-Dichloroethane (1,2-DCA) is a widespread groundwater contaminant known to be biodegradable under aerobic conditions via enzymatic oxidation or hydrolytic dehalogenation reactions. Current literature reports that stable carbon isotope fractionation of 1,2-DCA during aerobic biodegradation is large and reproducible (−27 to −33‰). In this study, a significant variation in the magnitude of stable carbon isotope fractionation during aerobic biodegradation was observed. Biodegradation in experiments involving microcosms, enrichment cultures, and pure microbial cultures produced a consistent bimodal distribution of enrichment factors (e) with one mean e centered on −3.9 ± 0.6‰ and the other on −29.2 ± 1.9‰. Reevaluation of e in terms of kinetic isotope effects 12k/13k gave values of 12k/13k = 1.01 and 1.06, which are typical of oxidation and hydrolytic dehalogenation (SN2) reactions, respectively. The bimodal distribution is therefore consistent with the microbial degradation of 1,2-DCA by two separate enzym...

Biodegradation of polycyclic aromatic hydrocarbons in oil-contaminated beach sediments treated with nutrient amendments.

Abstract: Microbial biodegradation of polycyclic aromatic hydrocarbons (PAHs) during the process of bioremediation can be constrained by lack of nutrients, low bioavailability of the contaminants, or scarcity of PAH-biodegrading microorganisms. This study focused on addressing the limitation of nutrient availability for PAH biodegradation in oil-contaminated beach sediments. In our previous study, three nutrient sources including inorganic soluble nutrients, the slow-release fertilizer Osmocote (Os; Scotts, Marysville, OH) and Inipol EAP-22 (Ip; ATOFINA Chemicals, Philadelphia, PA), as well as their combinations, were applied to beach sediments contaminated with an Arabian light crude oil. Osmocote was the most effective nutrient source for aliphatic biodegradation. This study presents data on PAH biodegradation in the oil-spiked beach sediments amended with the three nutrients. Biodegradation of total target PAHs (two- to six-ring) in all treatments followed a first-order biodegradation model. The biodegradation rates of total target PAHs in the sediments treated with Os were significantly higher than those without. On Day 45, approximately 9.3% of total target PAHs remained in the sediments amended with Os alone, significantly lower than the 54.2 to 58.0% remaining in sediment treatments without Os. Amendment with Inipol or soluble nutrients alone, or in combination, did not stimulate biodegradation rates of PAHs with a ring number higher than 2. The slow-release fertilizer (Os) is therefore recommended as an effective nutrient amendment for intrinsic biodegradation of PAHs in oil-contaminated beach sediments.

Biotransformation and dissolution of petroleum hydrocarbons in natural flowing seawater at low temperature.

Abstract: The objective of this study was to establish methods for controlled studies of hydrocarbon depletion from thin oil films in cold natural seawater, and to determine biotransformation in relation to other essential depletion processes. Mineral oil was immobilized on the surface of hydrophobic Fluortex fabrics and used for studies of microbial biodegradation in an experimental seawater flow-through system at low temperatures (5.9–7.4°C) during a test period of 42 days. The seawater was collected from a depth of 90 m, and microbial characterization by epifluorescence microscopy, fluorescence in situ hybridization, and most-probable number analysis showed relatively larger fractions of archaea and oil-degrading microbes than in the corresponding surface water. Chemical analysis of hydrocarbons attached to the fabrics during the test perweree re(H)-hopane showed that the oil remained adsorbed to the fabrics during the test period.

Biosurfactant Enhancement of Microbial Degradation of Various Structural Classes of Hydrocarbon in Mixed Waste Systems

Abstract: This study examines the effect of two rhamnolipid biosurfactants on the first-order biodegradation rate constant for a microbial consortium growing on a mixture of hydrocarbons representing four structural classes of hydrocarbons. The microbial biodegradation rate of hexadecane, dodecane, benzene, toluene, iso-octane, pristane (2,6,10,14 tetramethyl pentadecane), naphthalene, and phenanthrene in the presence and absence of a mixture of rhamnolipid biosurfactant was determined. A first-order b iodegradation model was applied in these studies to better discern the differential solubilization and biodegradation rates for specific structural classes of hydrocarbons in hydrocarbon mixtures. The biodegradation rate was enhanced by the addition of biosurfactant levels above the critical micelle concentration for all hydrocarbon species except phenanthrene and naphthalene. The time required for complete removal of each of hydrocarbons from the culture was shortened due to the presence of s urfactant, indicating a...

Application of a slow-release fertilizer for oil bioremediation in beach sediment.

Abstract: A 105-d field experiment was conducted to determine the potential of the slow-release fertilizer, Osmocote (Scotts, Marysville, OH), to stimulate the indigenous microbial biodegradation of petroleum hydrocarbons in an oil-spiked beach sediment on an intertidal foreshore in Singapore. Triplicate microcosms containing 80 kg of weathered sediment, spiked with 5% (w/w) Arabian light crude oil and 1.2% (w/w) Osmocote pellets, were established, together with control microcosms minus Osmocote. Relative to the control, the presence of the Osmocote sustained a significantly higher level of nutrients (NH(4)(+)-N, NO(3)(-)-N, and PO(4)(3-)-P) in the sediment pore water over the duration of the experiment. The metabolic activity of the indigenous microbial biomass, as measured using an intracellular dehydrogenase enzyme assay, was also significantly enhanced over the duration of the experiment in amended sediments. The loss of total recoverable petroleum hydrocarbons (TRPH) and biodegradation of total n-alkanes (C(10)-C(33)), branched alkanes (pristane and phytane), as well as total target polycyclic aromatic hydrocarbons (PAHs) (two- to six-ring), in both the control and Osmocote-amended sediments, followed a first-order biodegradation model. The first-order loss rate of total recoverable petroleum hydrocarbons was 2.57 times greater than that of the control. The hopane-normalized rate constants for total n-alkane, branched alkane, and total target PAH biodegradation in the Osmocote-treated sediments were 3.95-, 5.50-, and 2.45-fold higher than the control, respectively. Overall, the presence of Osmocote was able to significantly enhance and accelerate the biodegradation of aliphatics and PAHs in oil-contaminated sediments under natural field conditions in an intertidal foreshore environment.

Use of activated carbon as a support medium for H2S biofiltration and effect of bacterial immobilization on available pore surface.

Abstract: The use of support media for the immobilization of microorganisms is widely known to provide a surface for microbial growth and a shelter that protects the microorganisms from inhibitory compounds. In this study, activated carbon is used as a support medium for the immobilization of microorganisms enriched from municipal sewage activated sludge to remove gas-phase hydrogen sulfide (H2S), a major odorous component of waste gas from sewage treatment plants. A series of designed experiments is used to examine the effect on bacteria-immobilized activated carbon (termed "biocarbon") due to physical adsorption, chemical reaction, and microbial degradation in the overall removal of H2S. H2S breakthrough tests are conducted with various samples, including microbe-immobilized carbon and Teflon discs, salts-medium-washed carbon, and ultra-pure water-washed carbon. The results show a higher removal capacity for the microbe-immobilized activated carbon compared with the activated carbon control in a batch biofilter column. The increase in removal capacity is attributed to the role played by the immobilized microorganisms in metabolizing adsorbed sulfur and sulfur compounds on the biocarbon, hence releasing the adsorption sites for further H2S uptake. The advantage for activated carbon serving as the support medium is to adsorb a high initial concentration of substrate and progressively release this for microbial degradation, hence acting as a buffer for the microorganisms. Results obtained from surface area and pore size distribution analyses of the biocarbon show a correlation between the available surface area and pore volume with the extent of microbial immobilization and H2S uptake. The depletion of surface area and pore volume is seen as one of the factors which cause the onset of column breakthrough. Microbial growth retardation is due to the accumulation of metabolic products (i.e., sulfuric acid); and a lack of water and nutrient salts in the batch biofilter are other possible causes of column breakthrough.

Biodegradation and Bioremediation of Halogenated Organic Compounds

Abstract: Halo-organic compounds are among the most problematic pollutants. The relatively great electronegativity of halogens often confers chemical stability to halo-organic compounds, thereby making these compounds recalcitrant to biodegradation. Halogen substituents can increase the hydrophobicity of organic compounds, increasing their tendency to bioaccumulate in food chains as well as to sorb to soil. Finally, halogen substituents can contribute to harmful biological effects of organic compounds, increasing their toxicity, mutagenicity and other detrimental capacities. This chapter will focus on types of halo-organic compounds that have become important soil pollutants and that have the potential, demonstrated or theoretical, to be bioremediated. Generally, the potential for bioremediation requires that a halo-organic compound can be biodegraded, partly or completely destroyed by metabolism. Despite the metabolic challenges posed by halo-organic compounds, microorganisms have demonstrated a remarkable capacity to biodegrade such compounds.

Bioavailability and Biodegradation of Organic Pollutants — A Microbial Perspective

Abstract: Environmental pollutants are a global issue due to direct contamination from growing industrialized centers, application of pesticides, herbicides and insecticides, and indirect contamination resulting from longrange atmospheric transport that distributes persistent pollutants such as polychlorinated biphenyls (PCBs) around the world (Meijer et al. 2003). Pollutant characteristics, environmental conditions, soil and vegetation type, and proximity to source create a complex set of conditions influencing pollutant lifecycles. Soils are key reservoirs for environmental pollutants with deposition and persistence being dependent on factors such as atmospheric exchange, formation of bound residues, burial, and biodegradation (Mackay 2001).

Investigation of PCBs biodegradation by soil bacteria using tritium-labeled PCBs

Abstract: The method of tritium labeling of polychlorinated biphenyls (PCBs) has been developed. It allows producing of uniformly labeled tritium PCBs. High specific activity permits the tracing all of the tritium labeled PCBs biodegradation products. Radiochemical approach of the investigation of PCBs microbial degradation has been developed and PCB-destructive activity of soil bacteria strains has been studied. It was found that 4 investigated bacteria strains of Bacillus sp. has the ability accumulate and destroy PCBs. Use of developed radiochemical methods in complex with other analytical methods in investigation of PCBs biodegradation provide useful additional information. The radiochemical methods developed can be successfully used for wide screening of microorganisms, destructors of PCBs.

Remediation of petroleum-contaminated Antarctic soil

Abstract: Remediation of petroleum hydrocarbons in polar environments is more costly and logistically and technically more difficult than corresponding temperate and tropical contaminated sites. Bioremediation and in-situ chemical oxidation (ICO) are possible strategies which may overcome the financial and technical challenges associated with polar-region site remediation. ICO involves introducing reactive chemicals to contaminated soils so that organic contaminants such as petroleum hydrocarbons are oxidised to environmentally innocuous compounds, while bioremediation relies on microbial activity to achieve this. At Old Casey Station, East Antarctica (66°17'S, 110°32'E) more than 20 000 L of Special Antarctic Blend (SAB) diesel fuel was spilt over 15 years ago. Concentrations in the spill zone are still about 20 000 ppm and the rates of natural attenuation are relatively slow. The application of oxidative chemicals to the site did not significantly reduce petroleum hydrocarbon concentrations and would likely hinder biodegradation through the destruction of the subsurface microbial communities to below the level of detection for over 2 years. Bioremediation is considered the only likely viable alternative to natural attenuation or dig-and-haul procedures. The factors which were suspected of limiting microbial degradation of petroleum contaminants were temperature, nutrients and water availability. Their potential limitations were investigated with a series of radiometric treatability (microcosm) studies. A positive correlation between temperatures (between -2 and 42°C) and the rate of 14C-octadecane mineralisation was found. The high rate of mineralisation at 37 and 42°C was surprising, as most continental Antarctic microorganisms have an optimal temperature between 20 and 30°C and a maximal growth temperature of less than 37°C. 14C-octadecane mineralisation at nine different inorganic nitrogen concentrations (ranging from 85 to over 27 000 mg N kg-soil-H20 -1 ) was monitored. Total mineralisation increased with increasing nutrient concentration peaking in the range 1000-1600 mg N kg-soil-H20-1 . Higher N concentrations reduced the rate of mineralisation, highlighting the importance of avoiding over-fertilisation. Gas chromatographic analysis of the aliphatic components of the SAB diesel in the contaminated soil showed good agreement with the radiometric microcosm outcomes. Ratios of n-C17: pristane and n-C18: phytane indicated that low nutrient concentrations rather than water were the main limiting factor for biodegradation of hydrocarbons in the soil collected from Old Casey Station when incubated at 10°C. The high rate of mineralisation at 42°C and the microbial population dynamics were also investigated in a series of non-radiometric microcosm studies. Denaturing gradient gel electrophoresis of nutrient-amended contaminated soil after 40 days incubation at 4, 10 and 42°C indicated significant differences between the microbial communities at each of the incubation temperatures. 16S rRNA gene sequences and fatty acid methyl ester analysis indicate that the dominant hydrocarbon degrading bacteria at 4 and 10°C are Pseudomonas spp., while Paenibacillus spp. are likely to be the dominant hydrocarbon degrading bacteria at 42°C. The main implication for bioremediation in Antarctica from this study is that a high-temperature treatment would yield the most rapid biodegradation of the contaminant. In situ biodegradation using nutrients and other amendments is still possible at soil temperatures that occur naturally during summer in Antarctica. However, because the soils from this site are characterised by low water holding capacities, it would be difficult to maintain optimal nutrient concentrations during full scale treatment, and thus the use of a controlled release nutrient should be considered for full scale remediation of petroleum contaminated soil in Antarctica.

Molecular composition of the gas chromatography amenable fractions of maya crude oil. a reference oil for microbial degradation experiments

Abstract: Maya oil constitutes a representative example of heavy sulphur-rich oils of increasing use in refineries which has been used as reference oil in the microbial degradation experiments performed within the MATBIOPOL project. A detailed study of the composition of n-alkanes, isoprenoid hydrocarbons, hopanes, steranes, polycyclic aromatic hydrocarbons, sulphur-compounds, carbazoles, phenols and alkyl carboxylic acids is reported in the present study. The distributions of these compounds indicate that the oil is geochemically mature and non biodegraded. However, the degree of thermal maturation does not reach the maximum geochemical conditions of hydrocarbon generation. The composition of these biomarkers also indicates that the oil originated from organic matter deposited in evaporitic environments. The content in phenols, carbazoles and other polar and acidic molecules may induce toxic effects in the microorganisms that may eventually increase the crude oil degradation rate upon spillage in coastal ...

Microbial degradation of Abamectin in soil

Abstract: Incubation test on the degradation dynamics of Abamectin in soil showed that the half-life of its non-biodegradation plus microbial biodegradation, non-biodegradation, and microbial biodegradation was 34.8, 277.3 and 49.9 d, respectively, and its degradation in soil was mostly by microbes. A dominant bacterium which could effectively degrade Abamectin was isolated from test soil, and identified as Stenotrophomonas maltrophilia by 16S rDNA. The crude enzyme extracted from the dominant bacteria had a Michaelis-Menten's constant 6.78 nmol x ml(-1) and a maximum rate 81.5 nmol x min(-1) x mg(-1).

Laboratory And Field Results Linking High Bulk Conductivities To The Microbial Degradation Of Petroleum Hydrocarbons

Abstract: The results of a field and laboratory investigation of unconsolidated sediments contaminated by petroleum hydrocarbons and undergoing natural biodegradation are presented. Fundamental to geophysical investigations of hydrocarbon impacted sediments is the assessment of how microbial degradational processes affect their geoelectrical response. Therefore, the primary goal of this study was to understand how microbially mediated processes in hydrocarbon impacted sediments influence the geoelectrical response of this impacted zone. The field and laboratory results showed higher bulk conductivity in sediments impacted by petroleum hydrocarbons. The impacted sediments also showed increased populations of alkane degrading microbes and elevated dissolved cations (e.g. Ca). The elevated cations in the contaminated sediments relative to uncontaminated sediments suggest enhanced mineral dissolution related to the microbial degradation of the hydrocarbon. Both the laboratory and field data showed the highest bulk conductivities occurring within zones impacted with the free-phase and residual phase hydrocarbon and not within the water saturated zone. A model using a simplified form of Archie's Law suggests highly elevated estimated pore water conductivities within this conductive zone (~4 to 6 times background bulk conductivity) for both the laboratory and field data. The similar results for hydrocarbon contaminated sediments in laboratory experiments and field settings suggest that the mechanism for the high bulk conductivity in the contaminated zone is related to the microbial metabolism of the hydrocarbon and the resulting geochemical alterations within the contaminated zone. This study demonstrates that the higher bulk conductivity measured by geoelectrical methods at hydrocarbon impacted sites may be in part related to the microbial mineralization of the hydrocarbon.