Showing papers on "Microbial biodegradation published in 1997"

Microbial degradation of DDT and its residues—A review

Abstract: Microbial degradation of DDT residues is one mechanism for loss of DDT from soil. In this review pathways for biodegradation of DDT, DDD, and DDE by bacteria and fungi are described. Biodegradation of DDT residues can proceed in soil, albeit at a slow rate. To enhance degradation in situ a number of strategies are proposed. They include the addition of DDT‐metabolising microbes to contaminated soils and/or the manipulation of environmental conditions to enhance the activity of these microbes. Ligninolytic fungi and chlorobiphenyl degrading bacteria are promising candidates for remediation. Flooding of soil and the addition of organic matter can enhance DDT degradation. As biodegradation may be inhibited by lack of access of the microbe to the contaminant, the soil may need to be pre‐treated with a surfactant. Unlike DDT, little is known about the biodegradation of DDE, and this knowledge is crucial as DDE can be the predominant residue in some soils.

Bioremediation of diesel-oil-contaminated alpine soils at low temperatures

Abstract: Bioremediation of two diesel-oil-contaminated alpine subsoils, differing in soil type and bedrock, was investigated in laboratory experiments at 10 °C after supplementation with an inorganic fertilizer. Initial diesel oil contamination of 4000 mg kg−1 soil dry matter (dm) was reduced to 380–400 mg kg−1 dm after 155 days of incubation. In both soils, about 30 % of the diesel oil contamination (1200 mg kg−1 dm) was eliminated by abiotic processes. The residual decontamination (60 %–65 %) could be attributed to microbial degradation activities. In both soils, the addition of a cold-adapted diesel-oil-degrading inoculum enhanced biodegradation rates only slightly and temporarily. From C/N and N/P ratios (determined by measuring the contents of total hydrocarbons, NH4+ N, NO3− N and PO43− P) of soils␣it could be deduced that there was no nutrient deficiency during the whole incubation period. Soil biological activities (basal respiration and dehydrogenase activity) corresponded to the course of biodegradation activities in the soils.

Polycyclic aromatic hydrocarbon (PAH) occurrence and remediation methods

Abstract: Polycyclic aromatic hydrocarbons (PAHs) are potentially mutagenic and carcinogenic substances occurring at various concentrations in atmosphere, soils, waters and sediments. PAHs, inherited both from natural and anthropogenic processes, are persistent organic pollutants (POP) due to their chemical stability and biodegradation resistance. The increase of road transportation, and of industrial and agricultural activities has led to a notable build up of PAH amounts in the environmental media. For cases of heavy soil pollution, the main remediation methods are containment, thermal desorption, incineration, and microbial degradation. Phytoremediation, a low-cost process based on microbial activation in the root zone, is a novel method under deep investigation.

Biotransformation and biodegradation of N‐substituted aromatics in methanogenic granular sludge

Abstract: N-Substituted aromatic compounds are environmental contaminants associated with the production and use of dyes, explosives, pesticides and pharmaceuticals. In this article, we examine the potential of anaerobic granular sludge from anaerobic treatment systems towards the detoxification, transformation, and mineralization of nitroaromatic and azo compounds. Nitroaromatics and azo dyes with strong electron withdrawing are highly inhibitory to acetoclastic methanogenic bacteria. However, nitro and azo substituted aromatics are readily reductively detoxified in methanogenic consortia to their respective aromatic amines, which are several orders of magnitude less toxic. This reductive detoxification has allowed the successful operation of anaerobic reactors for the treatment of highly toxic aromatic compounds. In the course of the experiments it was discovered that some aromatic amines were mineralized. These results indicate that some N-substituted aromatic compounds can be completely mineralized and serve as a carbon and energy source for anaerobic bacteria.

Organic pollutants in the coastal environment off San Diego, California. 2. Petrogenic and biogenic sources of aliphatic hydrocarbons

Abstract: The results from the measurements of aliphatic hydrocarbons suggest that hydrocarbons in the Point Loma Wastewater Treatment Plant (PLWTP) effluents are mainly petroleum derived; those in the Tijuana River runoff have largely originated from terrestrial plants with visible petroleum contamination; and those in the sea surface microlayer, sediment traps, and sediments at various coastal locations off San Diego have mostly resulted from biogenic contributions with enhanced microbial products in the summer season. Rainfall in the winter season appeared to amplify the inputs from terrestrial higher plants to the coastal areas. The PLWTP discharged approximately 3.85 metric tons of n-alkanes (C10-C35) in 1994, well below the level (136 metric tons) estimated in 1979. The input of aliphatic hydrocarbons from the Tijuana River was about 0.101 metric tons in 1994. Diffusion, solubilization, evaporation, and microbial degradation seemed partially responsible for the difference in the concentrations and compositions of aliphatic hydrocarbons in different sample media, although the relative importance of each mechanism cannot be readily discerned from the available data. The results from analyses of aliphatic hydrocarbon compositional indices are generally consistent with those of polycyclic aromatic hydrocarbons.

Microbial degradation and treatment of polycyclic aromatic hydrocarbons and plasticizers

Abstract: Rhodococcus erytropolis and Pseudomonas sp. rapidly degrade many kinds of polycyclic aromatic hydrocarbon (PAH) compounds such as phenanthrene and phthalate esters such as di(2-ethylhexyl) phthalate, used as plasticizers. These compounds were efficiently removed from wastewater by inoculating viable cells of Rhodococcus erythropolis and Pseudomonas sp. into activated sludge as a biological treatment system. The rapid PCR method and fluorescent antibody techniques were successfully applied for tracing the specified microorganisms, which were inoculated into a mixed culture system. The relationship of microflora to the removal rate of these compounds such as phthalate esters in inoculated biological treatment systems was examined. The metabolic pathway was investigated and enzymes were purified.

Enhanced oily sludge biodegradation by a tensio-active agent isolated from Pseudomonas aeruginosa USB-CS1

Abstract: The biodegradation of an oily sludge is facilitated by a microbial tensio-active agent isolated from Pseudomonas aeruginosa USB-CS1. The optimal oil-in-water dispersion conditions are as follows: pH 6.5, temperature 30 °C, agitation 150 rev/min. The total hydrocarbon content shows that the biodegradation of the oily substrate mediated by the biosurfactant or by the biosurfactant–P. aeruginosa USB-CS1 complex is significantly higher after 30 days of incubation than that in other experimental conditions, by a mean of 70%. Substrate fractionation by column chromatography reveals that, if biosurfactant is present, saturated and aromatic compounds are more susceptible to microbial degradation than they are in other biodegradation systems by an average of 55% and 40% respectively. These results suggest that the stimulatory effects of the biosurfactant on the biodegradation of the oily substrate are limited over time by the loss of surface activity of the biosurfactant after 30 days of incubation.

Perspectives in bioremediation: technologies for environmental improvement.

Abstract: 1. Environmental Site Assessments and Bioremediation J.G. Ham, J.S. Bonner. 2. Microbial Ecology of Contaminated Sites C.S. Jacobsen, R.R. Gayazov. 3. Predictive Models for the Efficacy of Bioremediation F. Briganti, et al. 4. Rates and Dynamics of Bioremediation S.D. Varfolomeyev. 5. Microorganisms Involved in the Biodegradation of Organic Compounds L. Golovleva. 6. Microbial Resources for Bioremediation of Sites Polluted by Heavy Metals M. Mergeay. 7. Bioconversion and Removal of Metals and Radionuclides F. Baldi, et al. 8. Adaptation: Dynamics of Genes, Enzyme Activities and Populations F. Baldi, et al. 9. Protein Engineering for Improved Biodegradation of Recalcitrant Pollutants J.R. Mason, et al.

Microbial biodegradation of organic wastes containing surfactants in a continuous-flow reactor

Abstract: In a continuous flow bioreactor seeded with microbes from municipal activated sludge, complete organic carbon oxidation of simulated graywater (wastewater produced in human residences, excluding toilet wastes) was achieved at dilution rates up to 0.36 h−1 in the presence of 64.1 μ M linear alkylbenzenesulfonate (LAS) L−1. At LAS concentrations of 187 μ M, the system functioned only at dilution rates up to 0.23 h−1, and the biomass yield was two-fold lower. There were physiological changes in the microbial communities under different operating conditions, as measured by specific contents of ATP and extracellular hydrolases as well as the respiratory potential of the biomass. LAS inhibited the activity of LAS-degrading microbes at >150 μ M LAS, and the activity of other microbes at >75 μ M LAS. Chemical analysis of graywater indicated that samples consisted primarily of biological polymers (proteins and polysaccharides) and lower concentrations of surfactants. Biological remediation of graywater is possible, although treatment efficiency is influenced by the operating conditions and wastestream composition.

Microbial. transformation and biodegradation of calotropis procera latex towards obtaining value added chemicals, pharmaceuticals and fuels

Abstract: The latex of Calotropia arocera (Ait.) R.Br., (a potential petrocrop) may be exploited to obtain fuels and chemicals. This latex has been subjected to microbial action with Sphaerotilus aeruginosa, Sphaerotilus natans, Streptococcus sp.. Escherichia coli. Penicllllum expanaum and Mucor Sp. with an aim to find out a biochemical route way to obtain fuels and chemicals. The treated latex was extracted with hexane, chloroform and methanol separately. The extracts obtained were analysed using 13CNMR and 1HNMR spectral techniques to understand the chemical dynamics of biotransformation of latex components. Microbial action was found to degrade, biotransform, oxidise, dehydrogenate and dearomatize the chemical components of the latex. S. aeruginosa and streptococcus sp were found to be the potential candidates for the microbial degradation of latex. Latex mainly contains triterterpenoid, steroid etc. compounds. These acyclic and naphthenic type of compounds are stabler and relatively less reactive compo...

Biotransformation of toluene, benzene and naphthalene under anaerobic conditions.

Abstract: Aromatic hydrocarbons are widespread in nature, due to increasing industrial activity, and often contribute to polluted soils, sediments, and groundwater. Most of these compounds are toxic at relatively high concentrations, but some are already carcinogenic at very low concentrations, e.g. benzene. A growing awareness of the health risks associated with contamination has directed research to the removal or degradation of such compounds. The use of microorganisms to degrade toxic compounds (bioremediation) is a relatively slow process compared to traditional, chemical methods, but it is a natural process, mostly very specific and low in costs. A review of the available information on the microbial degradation of aromatic compounds is given in chapter 1. The anaerobic degradation is emphasized, since in many polluted environments oxygen is limiting and anaerobic processes will prevail. In the absence of oxygen, compounds like nitrate, metalions (Fe 3+ and Mn 4+ ), sulfate, and carbondioxide, have taken over the function of oxygen as a terminal electron acceptor. In addition, the first transformation reactions differ from those in aerobic processes. Oxygenases are no longer ftinctioning and the degradation of oxygenated aromatic compounds, like benzoate and phenol, is known to occur via e.g. reduction, dehydroxylation and dehydrogenation of the aromatic ring. Information on the anaerobic degradation of mono- and polycyclic aromatic hydrocarbons without functional groups, like toluene, benzene, and naphthalene, is scarse. To gain more insight in the possibilities and limitations of the anaerobic degradation of these aromatic compounds, their behaviour in anaerobic sediment columns was followed. Toluene, benzene, and naphthalene were chosen as model compounds under methanogenic, sulfate-, iron-, manganese-, and nitrate-reducing conditions (Chapter 2). Toluene was transformed readily (within 1 to 2 months), while benzene was recalcitrant over the test period of 375-525 days under all redox conditions tested. Naphthalene was partly transformed in the column with nitrate or manganese as electron acceptor present; the addition of benzoate had a positive effect on the degradation of naphthalene in the column with nitrate. In the column with sulfate, the majority of the added naphthalene disappeared. No effect on the degradation of naphthalene was observed after adding and omitting an easier degradable substrate. [ 14 C]naphthalene was used to confirm the disappearance to be the result of degradation; two third of the naphthalene was converted to CO 2 .Numerous attempts have been made for further enrichment of sulfatereducing, naphthalene degrading bacteria (Chapter 3). Unfortunately, the observed degradation of naphthalene in a sediment column could not be obtained in batch cultures, despite the large variety of tested enrichment conditions (different naphthalene concentrations, inoculum. size, medium composition, extra additions etc.). A toxic effect of naphthalene on sulfate- reducing bacteria could not be found.Toluene degradation in the columns was demonstrated under all redox conditions tested. Chapter 4 describes the degradation of toluene in freshly started sediment columns, to which either amorphous or highly crystalline manganese oxide had been added. In batch experiments with material from these columns as inoculum, the degradation of toluene to C0 2 and the formation of biomass under manganese-reducing conditions was demonstrated. The oxidation of toluene was found to be coupled to the reduction of Mn(IV), and the rate of oxidation was found to be lower with the crystalline than with the amorphous manganese oxide. Upon successive transfers of the enrichment cultures, the toluene degrading activity would decrease in time. The activity could only be maintained in the presence of sterilized Rhine river sediment or its supernatant. Without the sediment, but in the presence of solids like teflon beads, glass beads, bentonite, vermiculite and sterilized granular sludge, the toluene degrading activity completely disappeared after 4 to 5 transfers. Furthermore, a direct contact between the bacteria and the manganese oxide was found to be advantageous for a rapid toluene degradation. The degradation rate could further be increased by adding organic ligands such as oxalic acid or nitrilotriacetic acid (NTA).The highly purified enrichment culture LET-13, which degrades toluene with manganese oxide as electron acceptor, was obtained via repeated dilution series, and is described and characterized in chapter 5. LET-13 was able to degrade a variety of substituted monoaromatic compounds like (p-hydroxy) benzylalcohol, (p-hydroxy) benzaldehyde, (p-hydroxy) benzoate, cresol, and phenol. Benzene, ethylbenzene, xylene and naphthalene were not degraded under the experimental conditions used. The degradation of toluene occurred via hydroxylation of the methyl group to benzoate, and a possible side reaction can lead to the formation of cresol.All organisms in the culture look similar; motile rods which are gram negative, oxidase negative and catalase negative. The culture was partly identified with phylogenetic analysis of cloned rDNA sequences. The phylogenetic analysis showed that at least two major groups of bacteria are present. One group of bacteria belongs to the Bacteroides- Cytophaga group, and one group consists of members of the β-subclass of the Proteobacteria.Finally, the results from this research are discussed in relation to their relevance for soil bioremediation technologies.

Aerobic and Anaerobic Biodegradation of Aged Pentachlorophenol by Indigenous Microorganisms

Abstract: Pentachlorophenol (PCP) use as a general biocide, particularly for treating wood, has led to widespread environmental contamination. Biodegradation has emerged as the main mechanism for PCP degradation in soil and groundwater and a key strategy for remediation. Examining the microbial biodegrading potential for PCP at a contaminated site is crucial in determining its fate. Hundreds of studies have been published on PCP microbial degradation, but few have described the biodegradation of PCP that has been in contact with soils for many years. The bioavailability of “aged” hydrophobic organics is a significant concern. PCP- and 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP)-contaminated soil samples from several depths at a former wood treatment site were placed under varying conditions in the laboratory to determine the anaerobic and aerobic potential for biodegradation of chlorophenols at the site. PCP biodegradation occurred in both anaerobic and aerobic soil samples. Rapid aerobic degradation occurred...

Composition and method for degradation of polychlorinated biphenyl compounds

Abstract: Methods and compositions are disclosed for the microbial degradation of polychlorinated biphenyl compounds (PCBs) at a concentration of 100-200 mg/kg soil in contaminated environments, using natural, non-toxic, environmentally-acceptable compounds for application to such environments, such that PCB-contaminated environments are bioremediated by inducing a metabolic pathway in PCB-degrading microbes. Inoculated or indigenous PCB-degrading microbes, such as Arthrobacter strain B1B are induced to decontaminate the PCBs. Also disclosed are a plant and chemical screening assays for identifying plants that produce metabolites which promote PCB cometabolism. Further disclosed is a method for bioremediating PCB-contaminated environments in a commercially practical manner using l-carvone, a nontoxic and inexpensive chemical component of spearmint, for the in situ cleanup of PCB-contaminated soils, to induce Arthrobacter strain B1B to cometabolize and to substantially degrade PCBs.

A risk assessment of chlorinated aliphatics in bioremediated soils

Abstract: Natural microbes living in contaminated subsurface media can be enhanced to degrade large concentrations of contaminating compounds at a faster rate than the microbes could degrade under natural conditions. A feasibility study demonstrating this principle was performed on-site in southern Louisiana to evaluate the effectiveness of two microbial degradation remediation methods used to decrease the human carcinogenic risks associated with exposure to ethylene dichloride and vinyl chloride concentrations in contaminated clay and sludge soils at the site. The results of the study are compared to an acceptable Louisiana Department of Environmental Quality closure level to evaluate in-situ microbial enhancement in chlorinated aliphatic-contaminated sludge and clay soils as a remediation/cleanup alternative in similar industrial situations.

Microbial degradation and photolysis of pentachlorophenol

Abstract: PCP degradation was studied by test of simulation and pot culture and microbial experiments. In the PCP-polluted area total microbial quantity was unchanged and the main microbial populations included Bacillus, Streptomyces and Aspergillus. The soil degradation in dry farming was more rapid than in paddyy field. The micro-organisms degrading PCP were Acetobacter, Alcaligenes and Aeromonas. The photolysis of PCP in solution exposed to U. V ferformsu (λ=320nm) was rapidy.

Microorganisms Involved in the Biodegradation of Organic Compounds

Abstract: Many of the microorganisms capable of the degradation and bioconversion of organic compounds are described in this chapter. Basic processes of the microbiological conversion of xenobiotics are considered along with a characterization of the enzymes that bring about these bioconversions. Special attention is paid to the processes of microbiological transformation of xenobiotics which lead to more recalcitrant and toxic intermediates compared to their parent compounds. Several examples of the use of microorganisms in the practical application of bioremediation on sites contaminated with organic pollutants are referenced and briefly described.