Showing papers on "Microbial biodegradation published in 2013"

Bioavailability of Heavy Metals in Soil: Impact on Microbial Biodegradation of Organic Compounds and Possible Improvement Strategies

Abstract: Co-contamination of the environment with toxic chlorinated organic and heavy metal pollutants is one of the major problems facing industrialized nations today. Heavy metals may inhibit biodegradation of chlorinated organics by interacting with enzymes directly involved in biodegradation or those involved in general metabolism. Predictions of metal toxicity effects on organic pollutant biodegradation in co-contaminated soil and water environments is difficult since heavy metals may be present in a variety of chemical and physical forms. Recent advances in bioremediation of co-contaminated environments have focussed on the use of metal-resistant bacteria (cell and gene bioaugmentation), treatment amendments, clay minerals and chelating agents to reduce bioavailable heavy metal concentrations. Phytoremediation has also shown promise as an emerging alternative clean-up technology for co-contaminated environments. However, despite various investigations, in both aerobic and anaerobic systems, demonstrating that metal toxicity hampers the biodegradation of the organic component, a paucity of information exists in this area of research. Therefore, in this review, we discuss the problems associated with the degradation of chlorinated organics in co-contaminated environments, owing to metal toxicity and shed light on possible improvement strategies for effective bioremediation of sites co-contaminated with chlorinated organic compounds and heavy metals.

Microbial degradation of phenol and phenolic derivatives

Abstract: Phenol and its derivatives are one of the largest groups of environmental pollutants due to their presence in many industrial effluents and broad application as antibacterial and antifungal agents. A number of microbial species possess enzyme systems that are applicable for the decomposition of various aliphatic and aromatic toxic compounds. Intensive efforts to screen species with high-degradation activity are needed to study their capabilities of degrading phenol and phenolic derivatives. Mostofthecurrentresearchhasbeendirectedattheisolationandstudyofmicrobial species of potential ecological significance. In this review, some of the best achievementsindegradingphenoliccompoundsbybacteriaandyeastsarepresented,which draws attention to the high efficiency of strains of Pseudomonas, Candida tropicalis, Trichosporon cutaneum, etc. The unique ability of fungi to maintain their degradation potential under conditions unfavorable for other microorganisms is outstanding. Mathematical models of the microbial biodegradation dynamics of single and mixed aromatic compounds, which direct to the benefit of the processes studied in optimization of modern environmental biotechnology are also presented.

Rapid Degradation of Deepwater Horizon Spilled Oil by Indigenous Microbial Communities in Louisiana Saltmarsh Sediments

Abstract: The Deepwater Horizon oil spill led to the severe contamination of coastal environments in the Gulf of Mexico. A previous study detailed coastal saltmarsh erosion and recovery in a number of oil-impacted and nonimpacted reference sites in Barataria Bay, Louisiana over the first 18 months after the spill. Concentrations of alkanes and polyaromatic hydrocarbons (PAHs) at oil-impacted sites significantly decreased over this time period. Here, a combination of DNA, lipid, and isotopic approaches confirm that microbial biodegradation was contributing to the observed petroleum mass loss. Natural abundance 14C analysis of microbial phospholipid fatty acids (PLFA) reveals that petroleum-derived carbon was a primary carbon source for microbial communities at impacted sites several months following oil intrusion when the highest concentrations of oil were present. Also at this time, microbial community analysis suggests that community structure of all three domains has shifted with the intrusion of oil. These resul...

Determination of estrogenic steroids and microbial and photochemical degradation of 17α-ethinylestradiol (EE2) in lake surface water, a case study

Abstract: In this study, a GC-MS technique was applied to determine 17α-ethinylestradiol (EE2), an active ingredient of oral contraceptives, and its fate in Lake Quinsigamond, Massachusetts, USA. To the knowledge of the authors, this is the first study of EE2 and its microbial and photochemical degradation in a lake ecosystem. EE2 was detected at a concentration up to 11.1 ng L−1. At this concentration EE2 may affect the reproduction of fish and other aquatic organisms in the lake due to its high estrogenic activity. EE2 was persistent to the biodegradation by the microorganisms in the lake. Under aerobic conditions a long lag phase (42 days) was observed before the biodegradation of EE2 and a half-life of 108 days was estimated. Under anaerobic conditions, EE2 experienced even a longer acclimation stage (63 days) and a slower microbial degradation in the lake water. The photodegradation of EE2 was rapid in the lake surface water under natural sunlight, with a half-life of less than 2 days in summer sunny days. Compared to biodegradation, photodegradation may represent a predominant removal mechanism for EE2 in natural surface waters.

Degradation potential and microbial community structure of heavy oil-enriched microbial consortia from mangrove sediments in Okinawa, Japan.

Abstract: Mangroves constitute valuable coastal resources that are vulnerable to oil pollution. One of the major processes to remove oil from contaminated mangrove sediment is microbial degradation. A study on heavy oil- and hydrocarbon-degrading bacterial consortia from mangrove sediments in Okinawa, Japan was performed to evaluate their capacity to biodegrade and their microbial community composition. Surface sediment samples were obtained from mangrove sites in Okinawa (Teima, Oura, and Okukubi) and enriched with heavy oil as the sole carbon and energy source. The results revealed that all enriched microbial consortia degraded more than 20% of heavy oil in 21 days. The K1 consortium from Okukubi site showed the most extensive degradative capacity after 7 and 21 days. All consortia degraded more than 50% of hexadecane but had little ability to degrade polycyclic aromatic hydrocarbons (PAHs). The consortia were dominated by Pseudomonas or Burkholderia. When incubated in the presence of hydrocarbon compounds, the active bacterial community shifted to favor the dominance of Pseudomonas. The K1 consortium was a superior degrader, demonstrating the highest ability to degrade aliphatic and aromatic hydrocarbon compounds; it was even able to degrade heavy oil at a concentration of 15%(w/v). The dominance and turn-over of Pseudomonas and Burkholderia in the consortia suggest an important ecological role for and relationship between these two genera in the mangrove sediments of Okinawa.

Applications of bioremediation and phytoremediation.

Abstract: 1. Introduction The decontamination of soil and water from pollutants using microorganisms (bioremediators) is known as bioremediation (1). There are essentially two approaches, described as in situ and ex situ. In situ methods are those in which the contaminated material is treated at the site, whereas when the material is physically removed to be treated elsewhere it is referred to as ex situ. Some technologies that are related to bioremediation include those of phytoremediation (2,3), and are outlined below. It is possible for bioremediation to occur under natural conditions, or it can be stimulated, e.g. by the application of fertilisers (biostimulation), and more recently it has been shown that through the addition of matched microbe strains to the medium, the effectiveness of the resident microbe population to decompose contaminants may be enhanced. It should not be imagined that every type of contaminant can be disposed of by means of microorganisms. Heavy metal contaminants, e.g. [Cd.sub.2+] and [Pb.sup.2+], tend to resist interception by microorganisms. In such cases, phytoremediation is useful because the toxins are bioaccumulated into the body of plants, above ground, which can then be harvested and removed. By measuring the oxidation reduction potential (redox) in soil and groundwater, along with pH, temperature, [O.sub.2] tension, concentrations of electron acceptors and donors, and of decomposition products, such as C[O.sub.2], a measure of the bioremediation process can be obtained. Table 1 shows different biological decomposition processes, the rates of which decrease in decreasing order of the redox potential (fastest at higher potentials), although the detail of the overall bioremediation process per se is only scantly indicated by such values. To gain insight over a larger area, sufficient measurements should be made on and around the contaminated site such that contours of equal redox potential can be drawn. It is further necessary to perform analyses to ascertain that the ultimate levels of the contaminating compounds (and their products of decomposition) are below regulatory limits. Bioremediation can be used in locations that cannot readily be treated other than by excavation, e.g. spillages of petrol or chlorinated solvents which may contaminate groundwater. This is usually a much cheaper approach than excavating material to be disposed of elsewhere, or through other ex situ strategies, and which reduces or eliminates the need for "pump and treat", which is often employed where clean groundwater has been contaminated. The process may be enhanced by the addition of appropriate oxidising or reducing amendment agents. There is scope too for the creation of genetically modified microorganisms that are specifically tailored for bioremediation (5), e.g. the most radioresistant organism known so far, the aptly named bacterium Deinococcus radiodurans has been modified to consume and digest toluene and mercury cations in the presence of high level nuclear waste (6). 2. Some applications of microbial biodegradation The move toward finding "green" ways to ameliorate many environmental woes, including dealing with polluted environments, has led to a rising focus towards microbial degradation. Such methods of bioremediation and biotransformation exploit the remarkable diversity of xenobiotic metabolism by microbes. Thus, an enormous range of polluting materials may be addressed, including hydrocarbons (e.g. from oil-spills), polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), heterocyclics, pharmaceutical substances, pesticides, heavy metals (e.g. [Cd.sup.2+], [Pb.sup.2+], [Cu.sup.2+], [Zn.sup.2+]) and various radionuclides (e.g. [Cs.sup.+], [Sr.sup.2+]). Detailed genomic, metagenomic, proteomic, bioinformatic and other high-throughput analytical techniques, as applied to environmentally important microorganisms, have disclosed key features of critical biodegradative pathways and the ability of such organisms to adapt to changing environmental conditions and stress factors. …

Bioremediation via in situ microbial degradation of organic pollutants.

Abstract: Contamination of soil and natural waters by organic pollutants is a global problem. The major organic pollutants of point sources are mineral oil, fuel components, and chlorinated hydrocarbons. Research from the last two decades discovered that most of these compounds are biodegradable under anoxic conditions. This has led to the rise of bioremediation strategies based on the in situ biodegradation of pollutants. Monitored natural attenuation is a concept by which a contaminated site is remediated by natural biodegradation; to evaluate such processes, a combination of chemical and microbiological methods are usually used. Compound specific stable isotope analysis emerged as a key method for detecting and quantifying in situ biodegradation. Natural attenuation processes can be initiated or accelerated by manipulating the environmental conditions to become favorable for indigenous pollutant degrading microbial communities or by adding externally breeded specific pollutant degrading microorganisms; these techniques are referred to as enhanced natural attenuation. Xenobiotic micropollutants, such as pesticides or pharmaceuticals, contaminate diffusively large areas in low concentrations; the biodegradation pattern of such contaminations are not yet understood.

Bioremediation of Petroleum Contaminated Soil

Abstract: Environmental pollution with petroleum and petrochemical products has attracted much attention in recent decades. Contamination of the natural environment with oil derivatives causes soil, including arable land, to degrade, while the occurrence of many spots and areas of contamination may result in underground environments. This has been shown to have harmful effects on the environment and human beings at large. Improving our knowledge of the effects and remediation of oil-related pollution therefore is important for the future of developing countries with respect to the sustainable use of the environment. Bioremediation is one of the most popular remediation technologies in use due to the relatively low cost. It is a rapidly developing field of environmental restoration, utilizing natural microbial activity to reduce the concentration and/or toxicity of various chemical substances such as petroleum products and aliphatic and aromatic hydrocarbons. Biodegradation is a natural process carried out by soil and aquatic microorganisms, mostly bacteria and fungi. Certain bacterial strains have a demonstrated ability to break down or transform the chemical substances present in petroleum products. The goal of oil-spill bioremediation methods is to provide favorable conditions of oxygen, temperature and nutrients to maximize biological hydrocarbon breakdown. This paper is a short overview of petroleum hydrocarbon biodegradation and bioremediation.

Environmental studies on the microbial degradation of oil hydrocarbons and its application in Lebanese oil polluted coastal and marine ecosystem.

Abstract: Petroleum which is the major source of energy for industry and daily life is an extremely complex mixture of hydrocarbons. From the hundreds of individual components, four classes, based on related chemical structures can be recognized, and named as : aromatic, saturate or aliphatic, asphaltic and resins (Gopinathan et al., 2012). However, after the sinking of the super tanker Torney Canyon in 1967 the attention of the scientific community was drawn towards ISSN: 2319-7706 Volume 2 Number 6 (2013) pp. 1-18 http://www.ijcmas.com

Variovorax sp.-mediated biodegradation of the phenyl urea herbicide linuron at micropollutant concentrations and effects of natural dissolved organic matter as supplementary carbon source

Abstract: In nature, pesticides are often present as micropollutants with concentrations too low for efficient biodegradation and growth of heterotrophic pollutant-degrading bacteria. Instead, organic carbon present in environmental dissolved organic matter (eDOM) constitutes the main carbon source in nature. Information on how natural organic carbon affects degradation of pollutants and micropollutants, in particular, is however poor. Linuron-degrading Variovorax sp. strains SRS16, WDL1, and PBLH6 and a triple-species bacterial consortium, from which WDL1 originated, were examined for their ability to degrade linuron at micropollutant concentrations and the effect hereon of different eDOM formulations of varying biodegradability as supplementary C-source was explored. Individual strains and the consortium degraded linuron at initial concentrations as low as 1 μg L(-1) till concentrations below 4 ng L(-1). Degradation kinetics differed among strains with rates that differed up to 70-fold at the lowest linuron concentrations and with lag phases ranging from 0 to 7 days. Linuron biodegradation by the individual strains was inhibited by an easily biodegradable compound such as citrate but stimulated by eDOM at a linuron concentration of 10 mg L(-1). Effects were strongly reduced or became non-existent at micropollutant linuron concentrations. Effects of eDOM on degradation at 10 mg L(-1) linuron by WDL1 were reduced when WDL1 was incubated together with its original consortium members. This is the first report on eDOM effects on degradation of pesticides at micropollutant concentrations and indicates these effects are limited and depend on linuron and eDOM concentrations, eDOM quality, and the bacterial culture.

Biofilm comprising phototrophic, diazotrophic, and hydrocarbon-utilizing bacteria: a promising consortium in the bioremediation of aquatic hydrocarbon pollutants

Abstract: Biofilms harboring simultaneously anoxygenic and oxygenic phototrophic bacteria, diazotrophic bacteria, and hydrocarbon-utilizing bacteria were established on glass slides suspended in pristine and oily seawater. Via denaturing gradient gel electrophoresis analysis on PCR-amplified rRNA gene sequence fragments from the extracted DNA from biofilms, followed by band amplification, biofilm composition was determined. The biofilms contained anoxygenic phototrophs belonging to alphaproteobacteria; pico- and filamentous cyanobacteria (oxygenic phototrophs); two species of the diazotroph Azospirillum; and two hydrocarbon-utilizing gammaproteobacterial genera, Cycloclasticus and Oleibacter. The coexistence of all these microbial taxa with different physiologies in the biofilm makes the whole community nutritionally self-sufficient and adequately aerated, a condition quite suitable for the microbial biodegradation of aquatic pollutant hydrocarbons.

Biodegradation of Melanoidin from Distillery Effluent: Role of Microbes and Their Potential Enzymes

Abstract: Bioremediation is the process that deals with the microbial degradation of hazardous com‐ pounds from environment. The process of bioremediation is the natural process of biodegra‐ dation, which can degrade the pollutants and sometimes can completely oxidize the compound. Microorganisms play the vital role in the process of bioremediation and biode‐ gradation because of their great metabolic diversity, which includes the ability to metabolise these pollutants [1]. The degradation of toxic compounds to less harmful forms with the use of biological systems is called as bioremediation [2]. Bioremediation is limited in the number of toxic material, it can handle but where applicable it is cost effective and ecofriendly [3]. Today, water resources have been the most exploited of the natural systems, most of our water bodies are seriously polluted due to rapid population growth, industrial proliferation, urbanizations, increasing living standards and wide spheres of human activities. Many rivers of the world receive heavy flux due to industrial effluents [4]. The wastewater consisting of substances varying from simple nutrients to highly toxic hazardous chemicals, which when used for irrigation caused both beneficial and damaging effects to various crops including vegetables [5].

Bioremediation of PAH-Contaminated Soil by Fungi

Abstract: Polycyclic aromatic hydrocarbons (PAHs) are by-products of the incomplete combustion of organic materials. They are considered to be priority pollutants in the environment due to their recalcitrance and mutagenic properties. The principal PAH loss process from soil is through microbial degradation; therefore, the bioremediation is considered as an efficient, financially affordable, and adaptable alternative for the recuperation of PAH-contaminated soil. Several microorganisms, such as bacteria, yeasts, and filamentous fungi, are capable of degrading different types of PAHs. The ability of the fungi to degrade the high-molecular-weight PAHs, together with their physiological versatility, converts the fungal remediation in a promising technique for the cleanup of PAH-contaminated soil. This chapter summarizes the recent information on the metabolic pathway of the fungal transformation of PAHs and provides a critical review of previous work about fungal bioremediation of PAH-contaminated soil. Also, some of the most recently used fungal technology to enhance PAHs bioremediation processes is discussed.

Studies on Isolation and Identification of Active Microorganisms during Degradation of Polyethylene / Starch Film

Abstract: Low density polyethylene is a vital cause of environmental pollution. It occurs by choking sewer line through mishandling thus posing an everlasting ecological threat. Biodegradable plastics are eco-friendly; they accumulate great potential applications in various industries. Biodegradable polymers degrade upon disposal by the action of active microorganisms in the soil. The result of degradation can be interpreted with physical changes through biological force. Microbial degradation of plastics convert polymer into oligomers and monomers. This microbial degradation may be based on aerobic and anaerobic metabolisms. The main objective of present study is to isolate and identify the microorganisms from soil during biodegradation testing of polyethylene/starch film. The isolation is been carried out through soil serial dilution method. An isolated microorganism is cultivated in culture media. After growth of microorganisms at 37 0 C identification of microorganisms was carried out by macroscopic/microscopic examination. During identification it is found that bacteria (Pseudomonas spp, Streptococcus spp, Staphylococcus spp, Micrococcus spp and Moraxella spp etc), fungi (Aspergillus niger, Aspergillus glaucus etc), and Actinomycetes are present on the surface of polyethylene/starch film. Surface morphology of polyethylene/starch film has been analyzed by scanning electron microscopy (SEM) before and after degradation. Physico - mechanical properties has also been determined before and after degradation of film in order to understand the rate as well as the mechanism of degradation.