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PubMed2000

Effect of the carbon source on assessment of degrading bacteria with the spread-plating technique during in situ bioremediation.

Spread-plating belongs to traditional microbiological methods employed for quantification of subsurface microflora during bioremediation projects in the Czechia. Concentration of degrading organisms is estimated from the number of colonies grown on agar plates supplied with contaminant as the sole carbon source. The data obtained during in situ bioremediation of the Dacice site contaminated by cutting oil suggests that changes in the composition of the carbon source in the subsurface may cause a discrepancy between laboratory data and situation in subsurface.

Bacteria↗
PubMed2002

Bioremediation of PAH-contaminated soil by composting: a case study.

Composting technique was used for bioremediation of industrial soil originating from a former tar-contaminated site. The composting process was regulated by aeration to keep optimal temperature gradient and concentrations of O2 and CO2 inside the composting pile. The efficiency of bioremediation was evaluated by performing analysis of 11 individual three- to six-ring unsubstituted aromatic hydrocarbons (PAH) and estimating of changes in ecotoxicity of the contaminated soil. After 42 d of composting, PAH with 3-4 rings were removed from 42 to 68%, other higher-molar mass PAH from 35 to 57%. Additional 100 d of compost maturation in open-air field did not result in a further decrease of PAH. Ecotoxicity tests performed with bioluminescent bacteria Vibrio fischerii showed a decrease in toxicity both after composting and maturation phases. However, toxicity tests on mustard-seed germination did not reveal any significant changes during composting and maturation phases.

Agaricus↗
PubMed1991

Bench scale studies of the soil aeration process for bioremediation of petroleum hydrocarbons.

An alternative to traditional hydrocarbon bioremediation is to pump air through unsaturated soils to create aerobic conditions and induce biodegradation. This study examines the effects of moisture and nutrient augmentation on biodegradation of petroleum hydrocarbons in aerated soils. Findings indicate that forced aeration, coupled with additions of nutrients and moisture, stimulate hydrocarbon-degrading microorganisms and present a feasible approach to bioremediation management.

Bacteria↗
PubMed1994

Bioremediation of petroleum hydrocarbons in soil column lysimeters from Kwajalein island.

Soil column studies were used to evaluate petroleum hydrocarbon (PHC) remediation in soils from Kwajalein Atoll. Treatments included controls, and combinations of water, air, nutrients, and bioaugmentation with indigenous microbes (W, A, N, and M, respectively). Microbial colony forming units (CFU) decreased in the control columns and in treatments without air. Treatments including W+A+N and W+A+N+ exhibited increased CFU. One third of the PHC was removed by water and another third was removed by W+A+N and W+A+N+M treatments. Bioaugmentation with indigenous PHC degraders did not enhance bioremediation. Potential for bioremediation was demonstrated by air, water, and nutrient amendments.

Air↗
PubMed2004

Utilization of microbial biofilms as monitors of bioremediation.

A down-well aquifer microbial sampling system was developed using glass wool or Bio-Sep beads as a solid-phase support matrix. Here we describe the use of these devices to monitor the groundwater microbial community dynamics during field bioremediation experiments at the U.S. Department of Energy Natural and Accelerated Bioremediation Research Program's Field Research Center at the Oak Ridge National Laboratory. During the 6-week deployment, microbial biofilms colonized glass wool and bead internal surfaces. Changes in viable biomass, community composition, metabolic status, and respiratory state were reflected in sampler composition, type of donor, and groundwater pH. Biofilms that formed on Bio-Sep beads had 2-13 times greater viable biomass; however, the bead communities were less metabolically active [higher cyclopropane/monoenoic phospholipid fatty acid (PLFA) ratios] and had a lower aerobic respiratory state (lower total respiratory quinone/ PLFA ratio and ubiquinone/menaquinone ratio) than the biofilms formed on glass wool. Anaerobic growth in these systems was characterized by plasmalogen phospholipids and was greater in the wells that received electron donor additions. Partial 16S rDNA sequences indicated that Geobacter and nitrate-reducing organisms were induced by the acetate, ethanol, or glucose additions. DNA and lipid biomarkers were extracted and recovered without the complications that commonly plague sediment samples due to the presence of clay or dissolved organic matter. Although microbial community composition in the groundwater or adjacent sediments may differ from those formed on down-well biofilm samplers, the metabolic activity responses of the biofilms to modifications in groundwater geochemistry record the responses of the microbial community to biostimulation while providing integrative sampling and ease of recovery for biomarker analysis.

Acetates↗
PubMed2000

Aquifer Protist Response and the Potential for TCE Bioremediation with Burkholderia cepacia G4 PR1.

Bacterivorous protists have been recovered from pristine and contaminated aquifer environments, but the ecological role of these organisms in bioremediation strategies has not been well defined. Burkholderia cepacia G4 PR1 constitutively expresses a toluene ortho-monooxygenase (tom) due to a secondary transposition of a Tn5 transposable element in a trichloroethylene (TCE) degradative plasmid (TOM). Groundwater and sediment from a potential site for a TCE bioremediation field demonstration were used in laboratory microcosms to test the survival of this organism. In nonsterile aquifer sediment slurries, the bacterium was eliminated in a logrithmic decay concomitant with an increase in bacterivorous protists. A half-life for the organism calculated from extinction coefficients increased logarithmically with increasing inoculation density above 1 x 10(6) PR1 ml(-1). For inoculation densities below this level, the half-life of PR1 increased exponentially with decreasing inoculation density. The lowest half-lives corresponded to densities of bacteria that stimulate response of bacterivores. In a column system designed to incorporate aquifer flow, repeated addition of PR1 resulted in a buildup of bacterivore populations and reduced half-life of the bacterium. Addition of TCE and growth substrate in the eluent resulted in prolonged survival of PR1 and apparent mineralization of TCE. The results indicate significant but predictable losses due to native bacterivores would occur within and beyond a treatment zone where PR1 would be added to the aquifer, and mineralization of TCE in contaminated groundwater might be possible with repeated inoculation and addition of nutrients.

Journal Article↗
PubMed2002

Biotechnology and bioremediation: successes and limitations.

With advances in biotechnology, bioremediation has become one of the most rapidly developing fields of environmental restoration, utilizing microorganisms to reduce the concentration and toxicity of various chemical pollutants, such as petroleum hydrocarbons, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, phthalate esters, nitroaromatic compounds, industrial solvents, pesticides and metals. A number of bioremediation strategies have been developed to treat contaminated wastes and sites. Selecting the most appropriate strategy to treat a specific site can be guided by considering three basic principles: the amenability of the pollutant to biological transformation to less toxic products (biochemistry), the accessibility of the contaminant to microorganisms (bioavailability) and the opportunity for optimization of biological activity (bioactivity). Recent advances in the molecular genetics of biodegradation and studies on enzyme-tailoring and DNA-shuffling are discussed in this paper.

Biodegradation, Environmental↗
PubMed2002

Recent developments in molecular techniques for identification and monitoring of xenobiotic-degrading bacteria and their catabolic genes in bioremediation.

The pollution of soil and water with xenobiotics is widespread in the environment and is creating major health problems. The utilization of microorganisms to clean up xenobiotics from a polluted environment represents a potential solution to such environmental problems. Recent developments in molecular-biology-based techniques have led to rapid and accurate strategies for monitoring, discovery and identification of novel bacteria and their catabolic genes involved in the degradation of xenobiotics. Application of these techniques to bioremediation has also improved our understanding of the composition, phylogeny, and physiology of metabolically active members of the microbial community in the environment. This review provides an overview of recent developments in molecular-biology-based techniques and their application in bioremediation of xenobiotics.

Bacteria↗
PubMed2002

Bioremediation of chromate: thermodynamic analysis of the effects of Cr(VI) on sulfate-reducing bacteria.

Developing new bioremediation processes for soils and effluents polluted by Cr(VI) requires the selection of the most efficient and the most heavy-metal-resistant bacteria. The effects of Cr(VI) on bioenergetic metabolism in two sulfate-reducing bacteria (SRB), Desulfovibrio vulgaris Hildenborough and Desulfomicrobium norvegicum, were monitored using isothermal microcalorimetry. The complete reduction of Cr(VI) to Cr(III) was studied by spectrophotometry and by speciation using a combination of high-performance liquid chromatography and inductively coupled plasma-mass spectrometry. Results revealed that Cr(VI) induces an inhibition of growth with concomitant production of energy, which can be compared to the reaction of the bacteria to a stress such as oxidative stress. Moreover, the sensitivity of bacteria towards this metal is as a characteristic of the strain, which leads to differences in the kinetics of Cr(VI) reduction. The study by microcalorimetry of heavy metal effects on SRB bioenergetic metabolism thus appears an appropriate tool to identify better strains to be used for industrial bioremediation process development.

Biodegradation, Environmental↗
PubMed2005

Investigation on bioremediation of oil-polluted wetland at Liaodong Bay in northeast China.

An investigation on the effect of various microbes on degradation was carried out as part of the study on bioremediation of oil-polluted wetland at LiaoDong Bay in northeast China. The method used involved direct inoculation of selected bacteria, which were capable of degrading oil, to the soil samples. The combination of various bacteria showed better results in terms of oil degradation than any single ones due to their synergetic effects. The operation conditions [pH 8.0, 25 degrees C, C/N/P (40:5.6:1)] for these bacteria to degrade the oil content in the soil samples were also studied and optimized. Addition of appropriate surfactants was helpful for bacteria growth, thus favoring the oil degradation. For instance, after adding Tween 80 (300 mg/kg) for 8 days, the number of bacteria was amplified 6.22 times and the rate of oil degradation increased by 20%. Adequate amount of H2O2 was also beneficial for microbes to decompose oil. However, overdosage may cause the death of the bacteria. The addition of 400 mg/l H2O2 each time was suitable. Seven thousand milligrams of H2O2 was added entirely in 11 days, and the rate of oil degradation increased significantly from 27% (without H2O2) up to 67%. The study clearly demonstrated that the direct soil inoculation was an effective method for environmental bioremediation.

Biodegradation, Environmental↗
PubMed1999

Fermented whey--an inexpensive feed source for a laboratory-scale selenium-bioremediation reactor system inoculated with Thauera selenatis.

It is critical that an inexpensive electrondonor/carbon-source be found for selenium bioremediation using the selenate-respiring bacterium, Thauera selenatis. Since acetate is a preferred substrate for growth of this organism, a method was developed for fermenting the lactose in whey to large amounts of acetate. Indigenous whey microorganisms fermented the whey lactose in this manner when grown in continuous culture at a very slow dilution rate (D = 0.05 h-1). The successful use of the fermented whey lactose as the carbon-source/electron-donor feed for a laboratory-scale selenium-bioremediation reactor system, inoculated with T. selenatis, treating selenium-contaminated drainage water was also demonstrated. Selenium oxyanions and nitrate were reduced by 98%.

Animals↗
PubMed2002

Bioremediation of an industrial effluent containing monocrotophos.

Almost 30% of the precious agricultural output of India is lost owing to pest infestation. In India, pesticide consumption for protecting crops is about 3% of the total world consumption. Monocrotophos (MCP), an organophosphorus insecticide, is widely used to control insects on crops. Being readily water soluble and highly toxic, its removal from wastewater generated during manufacture becomes inevitable. Bioremediation of wastewater containing MCP by Arthrobacter atrocyaneus, Bacillus megaterium, and Pseudomonas mendocina was highest at pH 8.0, but maximum reduction in Chemical Oxygen Demand (COD) was at pH 7.0. Removal of MCP and reduction in COD by B. megaterium and Ps. mendocina were highest at 35 degrees C, while with A. atrocyaneus, it was maximum at 30 degrees C, under aerated culture condition and inoculum density of 10(8) cells/ml. Use of pure cultures for bioremediation of effluent containing MCP appears to be the first such attempt.

Arthrobacter↗
PubMed2001

In situ bioremediation potential of an oily sludge-degrading bacterial consortium.

A field-scale study was conducted in a 4000 m2 plot of land contaminated with an oily sludge by use of a carrier-based hydrocarbon-degrading bacterial consortium for bioremediation. The land belonged to an oil refinery. Prior to this study, a feasibility study was conducted to assess the capacity of the bacterial consortium to degrade oily sludge. The site selected for bioremediation contained approximately 300 tons of oily sludge. The plot was divided into four blocks, based on the extent of contamination. Blocks A, B, and C were treated with the bacterial consortium, whereas Block D was maintained as an untreated control. In Block A, at time zero, i.e., at the beginning of the experiment, the soil contained as much as 99.2 g/kg of total petroleum hydrocarbon (TPH). The application of a bacterial consortium (1 kg carrier-based bacterial consortium/10 m2 area) and nutrients degraded 90.2% of the TPH in 120 days, whereas in block D only 16.8% of the TPH was degraded. This study validates the large-scale use of a carrier-based bacterial consortium and nutrients for the treatment of land contaminated with oily sludge, a hazardous hydrocarbon waste generated by petroleum industry.

Acinetobacter↗
PubMed2004

Mineralization of hexachlorocyclohexane in soil during solid-phase bioremediation.

Soil containing hexachlorocyclohexane (HCH) was spiked with (14)C-gamma-HCH and then subjected to bioremediation in bench-scale microcosms to determine the rate and extent of mineralization of the (14)C-labeled HCH to (14)CO(2). The soil was treated using two different DARAMEND amendments, D6386 and D6390. The amendments were previously found to enhance natural HCH bioremediation as determined by measuring the disappearance of parent compounds under either strictly oxic conditions (D6386), or cycled anoxic/oxic conditions (D6390). Within 80 days of the initiation of treatment, mineralization was observed in all of the strictly oxic microcosms. However, mineralization was negligible in the cycled anoxic/oxic microcosms throughout the 275-day study, even after cycling was ceased at 84 days and although significant removal (up to 51%) of indigenous gamma-HCH (146 mg/kg) was detected by GC with electron capture detector. Of the amended, strictly oxic treatments, only one, in which 47% of the spiked (14)C-HCH was recovered as (14)CO(2), enhanced mineralization compared with an unamended treatment (in which 34% recovery was measured). Other oxic treatments involving higher amendment application rates or auxiliary carbon sources were inhibitory to mineralization. Thus, although HCH degradation occurs during the application of either oxic or cycled anoxic/oxic DARAMEND treatments, mineralization of gamma-HCH may be inhibited depending on the amendment and treatment protocol.

Biodegradation, Environmental↗
PubMed2005

Laboratory evaluation of oil spill bioremediation products in salt and freshwater systems.

Ten oil spill bioremediation products were tested in the laboratory for their ability to enhance biodegradation of weathered Alaskan North Slope crude oil in both freshwater and saltwater media. The products included nutrients to stimulate inoculated microorganisms, nutrients plus an oil-degrading inoculum, nutrients plus compounds intended to stimulate oil-degrading activity, or other compounds intended to enhance microbial activity. The product tests were undertaken to evaluate significant modifications in the existing official United States Environmental Protection Agency (EPA) protocol used for qualifying commercial bioremediation agents for use in oil spills. The EPA protocol was modified to include defined formulas for the exposure waters (freshwater, saltwater), a positive control using a known inoculum and nutrients, two negative controls (one sterile, the other inoculated but nutrient-limited), and simplified oil chemical analysis. Three analysts conducted the product test independently in each type of exposure water in round-robin fashion. Statistical tests were performed on analyst variability, reproducibility, and repeatability, and the performance of the various products was quantified in both exposure media. Analysis of variance showed that the analyst error at each time-point was highly significant (P values ranged from 0.0001 to 0.008, depending on water type and oil fraction). In the saltwater tests, six products demonstrated various degrees of biodegradative activity against the alkane fraction of the crude oil and three degraded the aromatic hydrocarbons by >10%. In the freshwater tests, eight products caused >20% loss of alkane hydrocarbons, of which five degraded the alkanes by >50%. Only four products were able to degrade polycyclic aromatic hydrocarbons (PAHs) by >20%, one of which caused 88% removal. However, when the variability of the analysts was taken into consideration, only one of the ten products was found to yield significant percent removals of the PAH fraction and only in freshwater. Viable microorganism population analysis (most-probable-number method) was also performed on every sample by each operator to measure the changes in aromatic and alkane hydrocarbon-degrading organism numbers. In general, little evidence of significant growth of either alkane- or PAH-degraders occurred among any of the ten products in either the saltwater or freshwater testing.

Alkanes↗
PubMed2006

Characterization and performance of constructed nitrifying biofilms during nitrogen bioremediation of a wastewater effluent.

Constructed ammonium oxidizing biofilms (CAOB) and constructed nitrite oxidizing biofilms (CNOB) were characterized during the bioremediation of a wastewater effluent. The maximum ammonium removal rate and removal efficiency in CAOB was 322 mg N-NH4+ m(-3) d(-1) and 96%, respectively, while in CNOB a maximum removal rate of 255 mg N-NH4+ m(-3) d(-1) and a removal efficiency of 76% was achieved. Both constructed biofilms on low-density polyester Dacron support achieved removal efficiencies higher than that of the concentrations normally present in reactors without constructed biofilms (P < 0.05). Nitrifying bacteria from the constructed biofilms cultures were typed by sequencing 16S rRNA genes that had been amplified by PCR from genomic DNA. Analysis of enrichment biofilms has therefore provided evidence of high removal of ammonium and the presence of Nitrosomonas eutropha, N. halophila and N. europaea in CAOB, while in CNOB Nitrobacter hamburgensis, N. winogradskyi and N. alkalicus were identified according to 16S rRNA gene sequences comparison. The biofilm reactors were nitrifying over the whole experimental period (15 days), showing a definite advantage of constructed biofilms for enhancing a high biomass concentration as evidenced by environmental electron microscopic analysis (ESEM). Our research demonstrates that low-density polyester Dacron can be effectively used for the construction of nitrifying biofilms obtaining high removal efficiencies of nitrogen in a relatively short time from municipal effluents from wastewater treatment plants. CAOB and CNOB are potentially promissory for the treatment of industrial wastewaters that otherwise requires very large and expensive reactors for efficient bioremediation of effluents.

Bacteria↗
PubMed2005

Evaluation of different bioremediation protocols to enhance decomposition of organic polymers in harbour sediments.

The response of the microbial community (in term of abundance and enzymatic activity) was investigated to test the effect of different bioremediation protocols to naturally enhance decomposition of organic polymers in harbour sediments (Genoa Harbour, Italy, N-W Mediterranean). Bioremediation techniques tested were bioaugmentation (5 different microorganisms' inocula), biostimulation (air supply), and natural attenuation. The coupling bioaugmentation/biostimulation was also tested. After 60 days, following the bioaugmentation protocol, bacterial densities correlated to the quantities of inocula amended to the boxes, suggesting that allochthonous community was able to survive and multiply. However, while bioaugmentation alone seems not to be able to carry out significative degradation, its coupling with air insufflations produced the best response: here bacterial densities increased, especially in the water (from 2.3 x 10(7) to 3.50 x 10(8) cells ml(-1)), average cell size and enzymatic activities increased, and sedimentary organic matter was significantly depleted (PRT 5-folds reduction, CHO 1.5-folds reduction). The strong coupling observed between the sediment and water compartments together with the greatest microbial response observed in this latter suggest that the sediment-water interface may constitute a key compartment for the occurring of biodegradation processes in organic-rich sediments.

Bacteria↗
PubMed1993

Monitoring the efficacy of bioremediation.

The general acceptance of bioremediation technology as an environmentally sound and economic treatment for hazardous waste requires the demonstration of its efficacy, reliability and predictability, as well as its advantages over conventional treatments. An effective monitoring design includes protocols for treatment-specific, representative sampling, control and monitoring: these should take into account abiotic and biotic pollutant fate processes in all relevant process compartments. A number of well-established and novel chemical and molecular biological monitoring techniques and parameters are available. Logical and balanced combinations of both chemical and biological monitoring parameters should be used to demonstrate complete degradation and detoxification of a hazardous waste as well as the biological nature of the process. At each process-scale level, a set of general criteria should be used for systematic evaluation of the overall efficacy of bioremediation.

Biodegradation, Environmental↗