Showing papers on "Microbial biodegradation published in 2003"

Microbial degradation of high and low molecular weight polyaromatic hydrocarbons in a two-phase partitioning bioreactor by two strains of Sphingomonas sp.

Abstract: A mixture of six polyaromatic hydrocarbons (naphthalene, phenanthrene, fluoranthene, pyrene, chyrysene and benzo[a]pyrene), varying in size from 2 to 5 rings, was dissolved in dodecane, and used as the delivery phase of a partitioning bioreactor. Two species of Sphingomonas were then used individually, and as a consortium, to determine which of the PAHs were degraded. Only low molecular weight PAHs (naphthalene, phenanthrene and fluoranthene) were degraded by the individual strains, but the consortium degraded all substrates either to completion or near completion.

Bioremediation of Petroleum Hydrocarbon Pollution

Abstract: Uncontrolled and catastrophic releases of petroleum pose ecologicaland environmental repercussions as a lot of hydrocarbon components are toxic and persistent in terrestrial and aquatic environments. Several physico-chemical methods of decontaminating the environment have been established and employed. Biological degradation, a safe, effective and an economic alternative method, is a process of decay initiated by biological agents, specifically in this case by microorganisms. Bioremediation refers to site restoration through the removal of organic contaminants by microorganisms. Biodegradation of hydrocarbons is largely carried out by diverse bacterial populations, which are ubiquitously distributed in the environment. The most commonly reported genera of hydrocarbon-degraders include Pseudomonas, Acinetobacter, Nocardia, Vibrio and Achromobacter. The factors, that influence the rates of microbial degradation of hydrocarbons, include temperature, pH, salinity, oxygen, nutrients, and physical and chemical composition of petroleum. Due to the complexity of crude oil, biodegradation involves the interaction of many different microbial species. It could be attributed to the effects of synergistic interactions among members of the consortium.

The organization of the microbial biodegradation network from a systems-biology perspective

Abstract: Microbial biodegradation of environmental pollutants is a field of growing importance because of its potential use in bioremediation and biocatalysis. We have studied the characteristics of the global biodegradation network that is brought about by all the known chemical reactions that are implicated in this process, regardless of their microbial hosts. This combination produces an efficient and integrated suprametabolism, with properties similar to those that define metabolic networks in single organisms. The characteristics of this network support an evolutionary scenario in which the reactions evolved outwards from the central metabolism. The properties of the global biodegradation network have implications for predicting the fate of current and future environmental pollutants.

Biodegradation of chlorsulfuron and metsulfuron-methyl by Aspergillus niger in laboratory conditions.

Abstract: Two sulfonylurea herbicides, chlorsulfuron and metsulfuron-methyl, were studied under laboratory conditions, in order to elucidate the biodegradation pathway operated by Aspergillus niger, a common soil fungus, which is often involved in the degradation of xenobiotics. HPLC-UV was used to study the kinetic of degradation, whereas LC-MS was used to identify the metabolites structure. In order to avoid the chemical degradation induced by a decrease in pH, due to the production of citric acid by the fungus, the experiments were performed in a buffered neutral medium. No significant degradation for both compounds was observed in mineral medium with 0.2% sodium acetate. On the contrary, in a rich medium, after 28 days the degradations, chemical degradation excluded, were about 30% for chlorsulfuron and 33% for metsulfuron-methyl. The main microbial metabolites were obtained via cleavage of the sulfonylurea bridge. In addition the fungus seems to be able to hydroxylate the aromatic ring of chlorsulfuron. In the case of metsulfuron-methyl the only detected metabolite was the triazine derivative, while the aromatic portion was completely degraded. Finally, the demethylation of the methoxy group on the triazine ring, previously observed with a Pseudomonas fluorescens strain, was not observed with A. niger.

Sorption kinetics and microbial biodegradation activity of hydrophobic chemicals in sewage sludge: Model and measurements based on free concentrations.

Abstract: In the current study, a new method is introduced with which the rate-limiting factor of biodegradation processes of hydrophobic chemicals in organic and aqueous systems can be determined. The novelty of this approach lies in the combination of a free concentration-based kinetic model with measurements of both free and total concentrations in time. This model includes microbial biodegradation activity of the chemical in the aqueous phase and chemical sorption kinetics with respectto organic carbon and aqueous phases. The time dependency of free and total concentrations of 7-acetyl-1,1,3,4,4,6-hexamethyltetrahydronaphthalene and 7-acetyl-1,1,3,4,4,6-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta(g) -2-benzopyrane in activated sludge was experimentally determined in vitro. Evaporation losses from the test system were also determined. Least-squares regression to optimize the model parameters resulted in a model that is in accordance with the experimental data. Additionally, the model shows that a comparison between the decrease of free and total chemical concentrations in time, in combination with an independent measurement of the organic carbon/water partition coefficient provides information about the rate-limiting step of the degradation process. This information can be used by sewage treatment plant managers to decide whether the microbial biodegradation activity itself or the desorption from organic carbon to the aqueous phase should be improved.

Biodiversity of Dioxin-Degrading Microorganisms and Potential Utilization in Bioremediation

Abstract: Dioxins are a group of chloroaromatic compounds known to be toxic and carcinogenic, and persistent environmental pollutants. How to remedy dioxin-polluted environments is one of the most challenging problems in environmental technology. From ecological and economical viewpoints, biological methods using particular microorganisms and microbial consortia capable of dioxin transformation and degradation have greater appeal than physicochemical methods in their application for environmental remediation. Large numbers of microorganisms capable of degrading dioxins and dioxin-like compounds have been isolated and characterized. Information about the biodiversity, ecophysiology and molecular biology of dioxin-degrading microorganisms has accumulated particularly during the past decade. There are three major modes of microbial degradation and transformation of dioxins; that is, oxidative degradation by aerobic bacteria containing aromatic hydrocarbon dioxygenases, reductive dechlorination by anaerobic microorganisms and fungal oxidation with cytochrome P-450, lignin peroxidases and laccases. This article overviews the current knowledge of microbial degradation and transformation of dioxins as well as the biodiversity of microorganisms involved. Strategies directed towards the bioremediation of dioxin-polluted environments are discussed.

Biotransformation of 2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12- Hexaazaisowurtzitane (CL-20) by Denitrifying Pseudomonas sp. Strain FA1

Abstract: The microbial and enzymatic degradation of a new energetic compound, 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), is not well understood. Fundamental knowledge about the mechanism of microbial degradation of CL-20 is essential to allow the prediction of its fate in the environment. In the present study, a CL-20-degrading denitrifying strain capable of utilizing CL-20 as the sole nitrogen source, Pseudomonas sp. strain FA1, was isolated from a garden soil. Studies with intact cells showed that aerobic conditions were required for bacterial growth and that anaerobic conditions enhanced CL-20 biotransformation. An enzyme(s) involved in the initial biotransformation of CL-20 was shown to be membrane associated and NADH dependent, and its expression was up-regulated about 2.2-fold in CL-20-induced cells. The rates of CL-20 biotransformation by the resting cells and the membrane-enzyme preparation were 3.2 ± 0.1 nmol h−1 mg of cell biomass−1 and 11.5 ± 0.4 nmol h−1 mg of protein−1, respectively, under anaerobic conditions. In the membrane-enzyme-catalyzed reactions, 2.3 nitrite ions (NO2−), 1.5 molecules of nitrous oxide (N2O), and 1.7 molecules of formic acid (HCOOH) were produced per reacted CL-20 molecule. The membrane-enzyme preparation reduced nitrite to nitrous oxide under anaerobic conditions. A comparative study of native enzymes, deflavoenzymes, and a reconstituted enzyme(s) and their subsequent inhibition by diphenyliodonium revealed that biotransformation of CL-20 is catalyzed by a membrane-associated flavoenzyme. The latter catalyzed an oxygen-sensitive one-electron transfer reaction that caused initial N denitration of CL-20.

Influence of peanut oil on microbial degradation of polycyclic aromatic hydrocarbons.

Abstract: Peanut oil amendment (0.1%–0.2% (v/v)) increased the biodegradation of various polycyclic aromatic hydrocarbons (PAHs) by 15%–80% with a mixed bacterial culture and a pure culture of Comamonas test...

Bioremediation of Metals and Radionuclides: What It Is and How It Works (2nd Edition)

Abstract: This primer is intended for people interested in environmental problems of the U.S. Department of Energy (DOE) 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. The second edition of the primer incorporates recent findings by researchers in DOE's Natural and Accelerated Bioremediation Research (NABIR) Program. 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 the physical-chemical environment, microbial communities, and nature of the contaminant. This technology includes intrinsic bioremediation, which relies on naturally occurring processes, and accelerated bioremediation, which enhances microbial degradation or transformation through the addition of nutrients (biostimulation) or inoculation with microorganisms (bioaugmentation). Over the past few years, interest in bioremediation has increased. It has become clear that many organic contaminants such as hydrocarbon fuels can be degraded to relatively harmless products such as CO{sub 2} (the end result of the degradation process). Waste water managers and scientists have also found that microorganisms can interact with metals and convert them from one chemical form to another. Laboratory tests and ex situ bioremediation applications have shown that microorganisms can change the valence, or oxidation state, of some heavy metals (e.g., chromium and mercury) and radionuclides (e.g., uranium) by using them as electron acceptors. In some cases, the solubility of the altered species decreases and the contaminant is immobilized in situ, i.e., precipitated into an insoluble salt in the sediment. In other cases, the opposite occurs--the solubility of the altered species increases, increasing the mobility of the contaminant and allowing it to be more easily flushed from the environment. Both of these kinds of transformations present opportunities for bioremediation of metals and radionuclides--either to lock them in place, or to accelerate their removal. DOE's goal is to reduce the risk and related exposure to ground water, sediment, and soil contamination at Department of Energy facilities. Subsurface bioremediation of metals and radionuclides at the site of contamination (in situ bioremediation) is not yet in widespread use. However, successful in situ applications of bioremediation to petroleum products and chlorinated solvents provide experience from which scientists can draw. Taken together, the accomplishments in these areas have led scientists and engineers to be optimistic about applying this technology to the mixtures of metals and radionuclides that are found at some of the most contaminated DOE sites. This primer examines some of the basic microbial and chemical processes that are a part of bioremediation, specifically the bioremediation of metals and radionuclides. The primer is divided into six sections, with the information in each building on that of the previous. The sections include features that highlight topics of interest and provide background information on specific biological and chemical processes and reactions. The first section briefly examines the scope of the contamination problem at DOE facilities. The second section gives a summary of some of the most commonly used bioremediation technologies, including successful in situ and ex situ techniques. The third discusses chemical and physical properties of metals and radionuclides found in contaminant mixtures at DOE sites, including solubility and the most common oxidation states in which these materials are found. The fourth section is an overview of the basic microbial processes that occur in bioremediation. The fifth section looks at specific in situ bioremediation processes that can be used on these contaminant mixtures. The primer concludes with examples of field research on bioremediation of metals and radionuclides.

Aerobic and anaerobic microbial degradation of poly-β-hydroxybutyrate produced by Azotobacter chroococcum

Abstract: Food industry wastewater served as a carbon source for the synthesis of poly-β-hydroxybutyrate (PHB) by Azotobacter chroococcum. The content of polymer in bacterial cells grown on the raw materials reached 75%. PHB films were degraded under aerobic, microaerobic, and anaerobic conditions in the presence and absence of nitrate by microbial populations of soil, sludges from anaerobic and nitrifying/denitrifying reactors, and sediment from a sludge deposit site. Changes in molecular mass, crystallinity, and mechanical properties of PHB were studied. Anaerobic degradation was accompanied by acetate formation, which was the main intermediate utilized by denitrifying bacteria or methanogenic archaea. On a decrease in temperature from 20 to 5° C in the presence of nitrate, the rate of PHB degradation was 7.3 times lower. Under anaerobic conditions and in the absence of nitrate, no PHB degradation was observed, even at 11°C. The enrichment cultures of denitrifying bacteria obtained from soil and anaerobic sludge degraded PHB films for a short time (3–7 d). The dominant species in the enrichment culture from soil were Pseudomonas fluorescens and Pseudomonas stutzeri. The rate of PHB degradation by the enrichment cultures depended on the polymer molecular weight, which reduced with time during biodegradation.

Microbial genes and enzymes in the degradation of chlorinated compounds.

Abstract: Microorganisms are well known for degrading numerous natural compounds. The synthesis of a multitude of chlorinated compounds by the chemical industry and their release into the natural environment have created major pollution problems. Part of the cause of such pollution is the inability of natural microorganisms to efficiently degrade synthetic chlorinated compounds. Microorganisms are, however, highly adaptable to changes in the environment and have consequently evolved the genes that specify the degradation of chlorinated compounds to varying degrees. Highly selective laboratory techniques have also enabled the isolation of microbial strains capable of utilizing normally recalcitrant highly chlorinated compounds as their sole source of carbon and energy. The evolution and role of microbial genes and enzymes, as well as their mode of regulation and genetic interrelationships, have therefore been the subjects of intense study. This review emphasizes the genetic organization and the regulation of gene expression, as well as evolutionary considerations, regarding the microbial degradation of chlorobenzoates, chlorocatechols, and chlorophenoxyacetic acids.

Bioremediation of Metals and Radionuclides: What It Is and How It Works (2nd Edition)

Abstract: This primer is intended for people interested in environmental problems of the U.S. Department of Energy (DOE) 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. The second edition of the primer incorporates recent findings by researchers in DOE's Natural and Accelerated Bioremediation Research (NABIR) Program. 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 the physical-chemical environment, microbial communities, and nature of the contaminant. This technology includes intrinsic bioremediation, which relies on naturally occurring processes, and accelerated bioremediation, which enhances microbial degradation or transformation through the addition of nutrients (biostimulation) or inoculation with microorganisms (bioaugmentation). Over the past few years, interest in bioremediation has increased. It has become clear that many organic contaminants such as hydrocarbon fuels can be degraded to relatively harmless products such as CO{sub 2} (the end result of the degradation process). Waste water managers and scientists have also found that microorganisms can interact with metals and convert them from one chemical form to another. Laboratory tests and ex situ bioremediation applications have shown that microorganisms can change the valence, or oxidation state, of some heavy metals (e.g., chromium and mercury) and radionuclides (e.g., uranium) by using them as electron acceptors. In some cases, the solubility of the altered species decreases and the contaminant is immobilized in situ, i.e., precipitated into an insoluble salt in the sediment. In other cases, the opposite occurs--the solubility of the altered species increases, increasing the mobility of the contaminant and allowing it to be more easily flushed from the environment. Both of these kinds of transformations present opportunities for bioremediation of metals and radionuclides--either to lock them in place, or to accelerate their removal. DOE's goal is to reduce the risk and related exposure to ground water, sediment, and soil contamination at Department of Energy facilities. Subsurface bioremediation of metals and radionuclides at the site of contamination (in situ bioremediation) is not yet in widespread use. However, successful in situ applications of bioremediation to petroleum products and chlorinated solvents provide experience from which scientists can draw. Taken together, the accomplishments in these areas have led scientists and engineers to be optimistic about applying this technology to the mixtures of metals and radionuclides that are found at some of the most contaminated DOE sites. This primer examines some of the basic microbial and chemical processes that are a part of bioremediation, specifically the bioremediation of metals and radionuclides. The primer is divided into six sections, with the information in each building on that of the previous. The sections include features that highlight topics of interest and provide background information on specific biological and chemical processes and reactions. The first section briefly examines the scope of the contamination problem at DOE facilities. The second section gives a summary of some of the most commonly used bioremediation technologies, including successful in situ and ex situ techniques. The third discusses chemical and physical properties of metals and radionuclides found in contaminant mixtures at DOE sites, including solubility and the most common oxidation states in which these materials are found. The fourth section is an overview of the basic microbial processes that occur in bioremediation. The fifth section looks at specific in situ bioremediation processes that can be used on these contaminant mixtures. The primer concludes with examples of field research on bioremediation of metals and radionuclides.

Environmental factors and kinetics of microbial degradation of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) in an aqueous medium

Abstract: Environmental factors such as oxygen, temperature, and microbial species may have significant effects on decomposition of biodegradable polymers. A representative biodegradable, thermoplastic polymer, poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV), was decomposed in an aqueous medium under controlled laboratory conditions by soil microbes for the intrinsic degradation kinetics and the effects of the environmental factors on polymer biodegradation. The amount of proteins, including the PHBV depolymerases, that attached to the polymer surfaces was quite constant during the period of significant mass loss of the polymer specimens. The microbial polymer degradation followed a zero-order rate model, so the residual mass fraction of PHBV films declined linearly with time. The mixed aerobic microbial organisms from fertile soil showed a higher activity of polymer degradation than an aerobic PHBV-producing bacterium and the mixed anaerobes in the same soil. The mixed anaerobic microorganisms from barren soil decomposed the polymer at a slower rate than the anaerobes from fertile soil, and this was attributed to fewer microbial cells in the barren soil instead of the difference in the microbial species. The temperature effect on PHBV degradation can be described with an Arrhenius equation, and the activation energy is around 16 kcal/mol. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 205–213, 2003

Phytoremediation of solid oil shale waste from the chemical industry

Abstract: The processed oil shale (semi-coke) contains several organic and inorganic compounds (oil fractions, sulphides, phenolic compounds, polycyclic aromatic hydrocarbons) and is highly toxic. The solid waste deposit is a source of toxic phenolic leachate, which is discharged into nearby bodies of water without any treatment. Field experiments were carried out in order to test the effect of phytoremediation to enhance in-situ microbial biodegradation of pollutants in semi-coke. Four pilot test plots (50 m 2 ) were established at a semi-coke deposit in July 2001. The growth rate of plants was approximately twice higher in the case of soil amendment. The phytoremediation increased the number of biodegradative bacteria and diversity of microbial community in semi-coke. The presence and diversity of multi-component phenol hydroxylase (mPH) genes in the environment were assessed using the microbial DNA directly extracted from semi-coke. The changes in the genotypes of mPHs indicated shifts in the microbial community structure towards the more efficient degradation of pollutants due to plant treatment. Within a four-month period starting from the establishment of test plots in July, the concentration of phenolic compounds decreased three times in average and the concentration of oil products up to ten times, compared to the control plot.

Enhancement of aerobic microbial degradation of polychlorinated biphenyl in soil microcosms.

Abstract: This article reports the results of various biodegradation experiments on polychlorinated biphenyl (PCB)-contaminated sandy soil employing a mixed culture of acclimatized bacteria. Following the optimization of different variables without chemical pretreatment, the elimination rate achieved of Aroclor® 1242 in slurry-phase reactors was 61% after four months of treatment, with the presence of biphenyl as cosubstrate being the most important factor affecting PCB biodegradation. The biodegradation occurred as a first-order process, and it proved most effective in respect to dichlorinated biphenyls (100% removal), followed by trichlorinated (92%) and tetrachlorinated biphenyls (24%). The results also showed that the degradability of PCBs in soil may be enhanced by an advanced oxidation pretreatment (Fenton reaction), producing almost 100% elimination of PCBs at the end of the integrated chemical-biological process and 72% mineralization of the intermediates generated during the chemical pretreatment.

Microbial degradation of linear alkylbenzene cable oil in soil and aqueous culture under aerobic and anaerobic conditions

Abstract: Johnson, S.J. (2004) Microbial degradation of linear alkylbenzene cable oil in soil and aqueous culture under aerobic and anaerobic conditions. Ph.D. Thesis. The University of Edinburgh.

Biodegradation of anthracene in the roots and growth substrate of poplar cuttings.

Abstract: Following their exposure to anthracene, the roots of Populus nigra L. Loenen showed traces of 9 substances classed as products of biodegradation. The main substances detected were phthalic acid and 9,10-anthraquinone, followed by hydroxy-anthracene and methoxyanthracene and five other compounds which could not be identified. Due to the relatively low concentration of degradation products found in the roots, further degradation to lower molecular compounds are discussed. The presence of 9,10-anthraquinone as the main product of the degradation of anthracene was also evident in the control tests with unplanted sandy substrate, although the content was higher in the planted series of tests. As a non-sterile approach was chosen, it may be assumed that a microbial degradation for 9,10-anthraquinone took place in the control series. However, it is difficult to differentiate clearly between a microbial degradation of anthracene in the substrate and metabolization in the roots due in part to the absence of specific degradation products in the various reaction areas.

Biodegradation Mechanism of Polycyclic Aromatic Hydrocarbons (PAHs) in Soil: A Review

Abstract: Many polycyclic aromatic hydrocarbons (PAHs)are known to be toxic, mutagenic and carcinogenic, and their contamination in soil is of great environmental concern. Microbial degradation of PAHs by its enzymatic capacity is the main process of the dissipation of PAHs in soils. Numerous genera of bacteria and fungi with the ability to utilize low molecular weight PAHs as sole carbon and energy sources have been reported. Limited numbers of bacteria and white rot fungi are found be able to cometabolize PAHs with four or more fused aromatic rings, provided that another carbon source is present. The focus of this review is on the high molecular weight PAHs: pyrene and benzopyrene (Bap). This review provides microorganisms with the ability to degrade PAHs, including pathways for their degradation by these organisms. Combined remediation with microorganisms and plants is a new bioremedial technique used in PAHs contaminated soils. In addition, the prospects on the research for PAHs degradation are discussed.

Characterisation of microbial community structure within anaerobic biofilms on municipal sold waste

Abstract: The overall aim of this study is to gain a deeper understanding of anaerobic microbial degradation processes of organic solid substrates. A number of commercial anaerobic in-vessel digestion technologies have been developed for the treatment of the organic fraction of municipal solid wastes (OFMSW) with the growing awareness and expectations of the community in relationship to environmental care. One of the major problems associated with in-vessel anaerobic digestion of MSW is the high capital cost for large-scale reactors and conveyor systems. Therefore, any advances that decrease the degradation time for MSW and thereby increase the potential throughput of anaerobic digesters are significant. This thesis, for the first time, made detailed microscopic observations of hydrolysing bacteria and biofilms on the surface of organic particles under anaerobic conditions. Also, this study investigates the influence of solid residence time (SRT) on the solubilisation of particles under a range of well-defined conditions.The experiments were performed in batch and semi-continuous mode. A mixture of leachate and cellulose was used as a medium. The performance of the reactors was evaluated by measuring the pH, soluble chemical oxygen demand (sCOD), total volatile fatty acid (TVFA), NH4-N and methane production rate, and calculating cumulative methane production and the extent of cellulose solubilisation. The microbial biofilm architecture was examined by using light and electron microscopy. Fluorescent in situ hybridisation with confocal laser scanning microscopy (FISH-CLSM) was used to investigate the microbial biofihn population structure.The batch experiments were initiated by inoculating with leachate and strained rumen contents. The complete anaerobic biodegradation of cellulose occurred in the reactor where the adherent cells had developed into a mature biofilm on the surface of cellulose. In contrast, only a few attached cells were observed on the particle surfaces in the soured reactors. This indicates that the formation of biofilms on the particle surface is necessary for the complete anaerobic degradation of organic matter. The results of rumen experiments suggest that the difference in the rate of solubilisation between the rumen and leachate systems was due to a difference in the rate of microbial attachment and a difference in the microbial populations. The light and electron microscopic examinations show that hydrolysing bacteria were anchored to the particle surfaces by extracellular polysaccharide (ECP) and the hydrolytic enzyme complexes were cell-associated. The FISH-CLSM observations suggest that the microbial communities involved in the complete anaerobic biodegradation processes exist entirely within the biofilm. The FISH-CLSM and transmission electron microscopy (TEM) biofilm observations found for the first time that the predominant methanogens in an anaerobic digestion environment are present in the form of striking ball-shaped colonies within biofilm.The effect of SRT on the solubilisation of cellulose was investigated in a semicontinuous mode under the six different SRTs. The scanning electron microscopy (SEM) images, showing that cellulose is only solubilised beneath adherent bacteria on the surface of the particles, suggest that a more fundamental measurement of the hydrolysis rate is the production of sCOD per unit surface area per unit time. The attachment of hydrolysing bacteria to the solid surface was limited at SRTs less than 5 days which leads a reduction in the extent and rate of cellulose solubilisation. The constant values of specific hydrolysis rate at longer SRTs suggest that the microbial solubilisation rate is constant regardless of SRTs, when the particle surface is covered with microorganisms. However, the investigation of the extent of cellulose solubilisation shows that the microbial pathways that lead to biomass and ECP are associated with longer SRTs. The model that was used to derive the surface specific hydrolysis rate assumed exponential microbial growth across the surface of the cellulose particles. The model did not consider surface limitations, but this is not a significant shortcoming because the particles are almost fully degraded once their surfaces are fully covered by biomass.The results in this thesis provide fundamental information on microbial hydrolysis processes and have important implications for improvement of the performance of in-vessel MSW anaerobic digestion processes.

Utilization of Agricultural Materials to Enhance Microbial Degradation of Polycyclic Aromatic Hydrocarbons in Soil

Abstract: The ability of agricultural waste materials to enhance bioremediation of soil contaminated with polycyclic aromatic hydrocarbons (PAHs) was investigated. Sandy soil spiked with phenanthrene, fluoranthene and pyrene was mixed with each of the following agricultural material: rice straw, peanut shells and rain tree leaves, at the ratio of 9:1. Bioremediation was performed in a small screw-capped vial used as a 2-gram microcosm with the moisture content of the soil mixtures adjusted to 60% of the water holding capacity of the soil and incubated at 30 o C in the dark. HPLC analyses revealed that addition of peanut shells and rain tree leaves could facilitate the decrease in concentrations to undetectable levels of phenanthrene within 24 days and fluoranthene and pyrene within 42 days, while rice straw did not produce any enhanced bioremediation effect. No decrease in PAH concentrations were observed in the soil mixtures without added agricultural materials or in the sterilized soil being used as a control. The results indicated that some biotic factors from the peanut shells and the rain tree leaves might play an important role in PAH degradation. Phenanthrene-degrading bacteria, representative PAH degraders, were detected by clear zone-forming around the colonies grown on carbon free mineral medium (CFMM) agar plate sprayed with phenanthrene solution. Numerous phenanthrene-degrading bacteria were found in mixtures of soil with nonsterilized peanut shells or rain tree leaves. Furthermore, bioavailability of PAHs in the soil mixtures was also determined via the dichloromethane extractability of the respective PAHs, indicating that the rain tree leaves provided more PAH availability than the peanut shells.

Microbial biodegradation of phosphonates

Abstract: A biodegradation process for the organophosphonate product of Sarin (O-isopropyl methylphosphonofluoridate) hydrolysis, i.e., isopropylmethylphosphonate (IMPA). This process provides a feasible biodegradation demilitarization alternative to Sarin incineration. Public opposition of nerve agent incineration is widespread, and alternative methods are sought to help the U.S. Army meet the 2007 demilitarization deadline imposed by the Chemical Weapons Convention. This process uses a two-step approach to IMPA biodegradation. In the first step, a concentrated IMPA solution is used as the sole nutritional carbon and phosphorus source for microbial cultures. The second step involves diluting the culture and adding an inexpensive carbon source to encourage bacterial phosphate assimilation. The biodegradation typically involves a consortium of microorganisms comprising Methylobacterium radiotolerans GB21, Agrobacterium tumefaciens GB2GA, Klebsiella oxytoca GB2CS, GB272, Aureobacterium sp. GB2 and three bacterial isolates belonging to the same species GB23, GB272, and GB292.

8 - Stable isotopic compositions of bacterial light hydrocarbons in marginal marine sediments

Abstract: This chapter discusses the stable isotopic compositions of bacterial light hydrocarbons in marginal marine sediments. While methane is the most abundant hydrocarbon in marginal marine sediments, other light hydrocarbons accompany methane in detectable concentrations. These are probably produced through the thermogenic and/or microbial degradation processes of organic materials. Distinguishing between these two types of natural gases is important for studying various phenomena that occur within land margin sediments, such as fluid migration, carbon cycling, natural gas (including gas hydrate) generation, and microbial activities under extreme conditions. Stable isotopic compositions of methane in anaerobic sediments are widely used to determine the mechanism and pathways of the production and consumption of methane, because microbial methane in general is 13 C-depleted relative to thermogenic methane.

Stimulation of microbial dechlorination of polychlorinated biphenyls with halogenated ethenes

Abstract: Disclosed is a method for the anaerobic microbial dechlorination of polychlorinated biphenyls (PCBs). Polyhalogenated ethenes are used to stimulate the growth and dechlorinating activity of PCB dechlorinating bacteria in a contaminated soil or sediment. This method may be further coupled with aerobic microbial degradation of PCBs for the complete destruction of PCBs in soils and sediments. Polyhalogenated ethenes are also used in growth media for the culturing of PCB dechlorinating bacteria.