• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.89-91
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• 2000

Polynuclear aromatic hydrocarbon (PAH) compounds are highly carcinogenic chemicals and common groundwater contaminants that are observed to persist in soils. The adherence and slow release of PAHs in soil is an obstacle to remediation and complicates the assessment of cleanup standards and risks. Biological degradation of PAHs in soil has been an area of active research because biological treatment may be less costly than conventional pumping technologies or excavation and thermal treatment. Biological degradation also offers the advantage to transform PAHs into non-toxic products such as biomass and carbon dioxide. Ample evidence exists for aerobic biodegradation of PAHs and many bacteria capable of degrading PAHs have been isolated and characterized. However, the microbial degradation of PAHs in sediments is impaired due to the anaerobic conditions that result from the typically high oxygen demand of the organic material present in the soil, the low solubility of oxygen in water, and the slow mass transfer of oxygen from overlying water to the soil environment. For these reasons, anaerobic microbial degradation technologies could help alleviate sediment PAH contamination and offer significant advantages for cost-efficient in-situ treatment. But very little is known about the potential for anaerobic degradation of PAHs in field soils. The objectives of this research were to assess: (1) the potential for biodegradation of PAH in field aged soils under denitrification conditions, (2) to assess the potential for biodegradation of naphthalene in soil microcosms under denitrifying conditions, and (3) to assess for the existence of microorganisms in field sediments capable of degrading naphthalene via denitrification. Two kinds of soils were used in this research: Harbor Point sediment (HPS-2) and Milwaukee Harbor sediment (MHS). Results presented in this seminar indicate possible degradation of PAHs in soil under denitrifying conditions. During the two months of anaerobic degradation, total PAH removal was modest probably due to both the low availability of the PAHs and competition with other more easily degradable sources of carbon in the sediments. For both Harbor Point sediment (HPS-2) and Milwaukee Harbor sediment (MHS), PAH reduction was confined to 3- and 4-ring PAHs. Comparing PAH reductions during two months of aerobic and anaerobic biotreatment of MHS, it was found that extent of PAHreduction for anaerobic treatment was compatible with that for aerobic treatment. Interestingly, removal of PAHs from sediment particle classes (by size and density) followed similar trends for aerobic and anaerobic treatment of MHS. The majority of the PAHs removed during biotreatment came from the clay/silt fraction. In an earlier study it was shown that PAHs associated with the clay/silt fraction in MHS were more available than PAHs associated with coal-derived fraction. Therefore, although total PAH reductions were small, the removal of PAHs from the more easily available sediment fraction (clay/silt) may result in a significant environmental benefit owing to a reduction in total PAH bioavailability. By using naphthalene as a model PAH compound, biodegradation of naphthalene under denitrifying condition was assessed in microcosms containing MHS. Naphthalene spiked into MHS was degraded below detection limit within 20 days with the accompanying reduction of nitrate. With repeated addition of naphthalene and nitrate, naphthalene degradation under nitrate reducing conditions was stable over one month. Nitrite, one of the intermediates of denitrification was detected during the incubation. Also the denitrification activity of the enrichment culture from MHS slurries was verified by monitoring the production of nitrogen gas in solid fluorescence denitrification medium. Microorganisms capable of degrading naphthalene via denitrification were isolated from this enrichment culture.

• Proceedings of the Zoological Society Korea Conference
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• 2000.10a
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• pp.127.2-128
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• 2000

No Abstract, See Full Text

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.1
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• pp.40-46
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• 2005

Clostridium bifermentans strain DPH-1 has already been found to dechlorinate perchloroethylene (PCE) to cis-dichloroethylene (cis-DCE) via trichloroethylene (TCE). In this study, our investigation on different culture conditions of this DPH-1 strain was extended to find a more efficient and cost effective growth medium composition for this DPH-1 strain in bioremediation practices. Temperature dependency of strain DPH-1 showed that the growth starting time and PCE degradation at $15^{\circ}C$ was very slow compared to that of $30^{\circ}C$, but complete PCE degradation occurred in both cases. For the proper utilization of strain DPH-1 in more cost effective bioremediation practices, a simpler composition of an effective media was studied. One component of the culture medium, yeast extract, had been substituted by molasses, which served as a good source of electron donor. The DPH-1 strain in the medium containing molasses, in the presence of $K_{2}HPO_4\;and\;KH_{2}PO_4$, showed identical bacterial multiplication (0.135 mg protein $mL^{-1}h^{-1}$) and PCE degradation rates ($0.38\;{\mu}M/h$) to those of the yeast extract containing medium.

• KSBB Journal
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• v.23 no.6
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• pp.479-483
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• 2008

The environmental contamination by organic pollutants is a widespread problem. The most widely distributed pollution can be attributed to oil contamination. Bioremediation, the use of microorganism or microbial processes to degrade environmental contaminant, is one of the new technologies. The objective of the present study is to study the degradation of JP-8 in soil by microorganism. The degradation of JP-8 was analysed by TPH using gas chromatography. Rhodococcus fascians isolated from the petroleum contaminated site was applied for the degradation of JP-8 in the soil column system. Air flow rate of 30 ml/min was sufficient to degrade JP-8 in the soil column as much as 70% of JP-8 in the soil column. The addition of nitrogen source resulted in the increase in JP-8 degradability to 75% of JP-8 and the C:N ratio for JP-8 degradation was 100:10.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.1
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• pp.43-50
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• 2012

Two typical animal waste management practices, composting and stockpiling, were evaluated for their effect on the degradation of three veterinary antibiotics (VAs), chlortetracycline (CTC), tylosin (TYL), and monensin (MNS). The VAs were applied to horse manure plots subject to composting or stockpiling, and core samples were collected over a period of time. Selected buffer solutions were used to extract the VAs and analysis for concentration was conducted with solid phase extraction (SPE) followed by high performance liquid chromatography tandem mass spectrometry (HPLC/MS/MS) technique. The VAs demonstrated rapid dissipation within ten days followed by a gradual decrease in concentration until the end of the experimental period (141 days). All three VAs degraded more rapidly in the composting samples than in the stockpiling samples, particularly between 20 and 60 days of the observation period. Degradation of the three VAs generally followed a first-order kinetic model, and a fitted model with a calculated rate constant was determined for each treatment. TYL in composting showed the fastest degradation, with a calculated rate constant of $0.91day^{-1}$; the slowest degradation was exhibited by MNS in stockpiling, with rate constant of $0.17day^{-1}$. Calculated correlation coefficients ranged from 0.89 to 0.96, indicating a strong correlation between measured concentrations and fitted values in this study. Although concentration of TYL in composting treatment showed below detection limit during the test period, this study suggests that composting can reduce animal waste contaminants prior to field application as fertilizer.

• Journal of the Korean Electrochemical Society
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• v.9 no.3
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• pp.118-123
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• 2006

Degradation of polymer electrolyte membrane fuel cell (PEMFC) that is facilitated by on/off cycles is one of the most important issues for commercialization of fuel cell vehicles. When a PEMFC stack is shut down, residual hydrogen and induce high voltage equivalent to open circuit voltage to the cathode side that might cause sintering of Pt catalyst and facilitate formation of hydrogen peroxide at the anode side that might decompose $Nafionc\'{A}$ membrane. In this study, degradation of PEMFC exposed to repetitive on/off cycles was investigated by measuring i-V characteristics, ac impedance, cyclic voltammograms, gas leak, cross-sectional SEM images, and TEM images. To prevent degradation of PEMFC caused by the residual gases, hydrogen was removed from anode gas channel by gas-purging and by using a dummy resistance, that were found to be a very effective method.

• Applied Biological Chemistry
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• v.38 no.3
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• pp.263-268
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• 1995

A study was undertaken to compare degradation patterns of carbofuran in soils between submerged and upland moisture conditions [$3-^{14}C$]Carbofuran was treated in each soils at the rate of 1.0 mg/kg (87.8 kBq $^{14}C/50g$ soil) and the time-course analysis for distribution of radioactivity and degradation products were conducted. Differences in the pathway and rate of carbofuran degradation in soils were observed between submerged and upland moisture conditiona major degradation being hydrolysis at 7-C position and oxidation at 3-C position, respectively. Carbofuran showed less persistence in soils of higher moisture contents A significant portion, $24{\sim}39%$ of the total radioactivity, resided in soils as nonextractable residues at 60 days after treatment The nonextractable radioactivity was mainly located in soil organic matter, fulvic acid, humic acid and humin factions Gel filtration chromatography confirmed the incorporation of carbofuran and its degradation products into the organic matter.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.44-45
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• 2001

• Proceedings of the Microbiological Society of Korea Conference
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• 2005.05a
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• pp.120-122
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• 2005

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2004.11a
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• pp.163-165
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• 2004