• Journal of Microbiology
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• v.40 no.4
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• pp.340-343
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• 2002

A PCB degrader, Ralstonia eutropha H850 was shown to induce bphC gene encoding 2,3-dihydroxy-biphenyl-1,2-dioxygenase in a carvone-amended pure culture in our previous study (Park et al.,1999). The present study was carried out to examine how plant terpenes, as natural substrates, would cause an expression of a PCB degradative gene in soil that was amended with terpenes. The population of Ralstonia eutropha H850 was maintained at least around 10$\^$8/ (CFU/g fresh soil) in the soil amended with carvone or limonene in the presence of succinate as a growth substrate at 50 th day. The gene expression was monitored by RT-PCR using total RNA directly extracted from each soil and bphC gene primers. The bphC gene expression of the seeded strain H850 was observed in the soil amended with biphenyl (4 days) but not with succinate, carvone and limonene. These results indicate that terpenes widely distributed in nature could be a potential inducing substrate for effective PCB biodegration in the soil but their bioavailability and specific induction behavior should be taken into account before PCB bioremediation implementation.

• Journal of Soil and Groundwater Environment
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• v.26 no.1
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• pp.34-44
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• 2021

Acid mine drainage (AMD) resulting from pyrite oxidation in mining areas, subsequently leads to soil acidification accompanied by lowering pH and high concentration of metals and metalloids in its surrounding environment. Regarding to this, the microbial amelioration has been considered as a promising option for a more cost-effective and eco-friendlier countermeasure, compared to the use of alkaline chemicals. This study was aimed to evaluate influencing factors in microbially-mediated amelioration of acidic soil spiked by simulated AMD. For this, microcosm experiments were conducted by acid-neutralizing bacterial consortium (dominated by Klebsiella sp. and Raoultella sp.) under the various conditions of AMD spikes (0-2,500 mg SO42-/L), together with acidic mine soil (0-100 g) or sphagnum peat (0-5 g) in the 200 mL of nutrient medium. The employed bacterial consortium, capable of resisting to high level of sulfate concentration (up to 1,500 mg SO42-/L) in low pH, generated the ammonium while concomitantly reduced the sulfate, subsequently contributing to the effective soil stabilization with an evolution of soil pH up to neutral. Furthermore, it demonstrates that suitable condition has to be tuned for successful microbial metabolism to facilitate with neutralization during practical application.

• KSBB Journal
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• v.27 no.2
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• pp.75-85
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• 2012

Although, microbial arsenic mobilization by dissimilatory arsenate-reducing bacteria (DARB) and the practical use to the removal technology of arsenic from contaminated soil are expected, most previous research mainly has been focused on the geochemical circulation of arsenic. Therefore, in this review we summarized the previously reported DARB to grasp the characteristic for bioremediation of arsenic. Evidence of microbial growth on arsenate is presented based on isolate analyses, after which a summary of the physiology of the following arsenate-respiring bacteria is provided: Chrysiogenes arsenatis strain BAL-$1^T$, Sulfurospirillum barnesii, Desulfotomaculum strain Ben-RB, Desulfotomaculum auripigmentum strains OREX-4, GFAJ-1, Bacillus sp., Desulfitobacterium hafniense DCB-$2^T$, strain SES-3, Citrobacter sp. (TSA-1 and NC-1), Sulfurospirillum arsenophilum sp. nov., Shewanella sp., Chrysiogenes arsenatis BAL-$1^T$, Deferribacter desulfuricans. Among the DARB, Citrobacter sp. NC-1 is superior to other dissimilatory arsenate-reducing bacteria with respect to arsenate reduction, particularly at high concentrations as high as 60 mM. A gram-negative anaerobic bacterium, Citrobacter sp. NC-1, which was isolated from arsenic contaminated soil, can grow on glucose as an electron donor and arsenate as an electron acceptor. Strain NC-1 rapidly reduced arsenate at 5 mM to arsenite with concomitant cell growth, indicating that arsenate can act as the terminal electron acceptor for anaerobic respiration (dissimilatory arsenate reduction). To characterize the reductase systems in strain NC-1, arsenate and nitrate reduction activities were investigated with washed-cell suspensions and crude cell extracts from cells grown on arsenate or nitrate. These reductase activities were induced individually by the two electron acceptors. Tungstate, which is a typical inhibitory antagonist of molybdenum containing dissimilatory reductases, strongly inhibited the reduction of arsenate and nitrate in anaerobic growth cultures. These results suggest that strain NC-1 catalyzes the reduction of arsenate and nitrate by distinct terminal reductases containing a molybdenum cofactor. This may be advantageous during bioremediation processes where both contaminants are present. Moreover, a brief explanation of arsenic extraction from a model soil artificially contaminated with As (V) using a novel DARB (Citrobacter sp. NC-1) is given in this article. We conclude with a discussion of the importance of microbial arsenate reduction in the environment. The successful application and use of DARB should facilitate the effective bioremediation of arsenic contaminated sites.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.29-32
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• 2006

화학적 산화처리와 bioremedation 기법을 개별적 또는 복합적으로 동시에 적용함으로써 한 개별 기법의 단점을 보완하고 현장적용성을 증대시킬 수 있는 통합기법을 개발하고자 하였다. 펜톤유사 반응을 통해 고농도의 유류를 산화분해 시킨 후 미생물 처리를 통해 잔류 유류 오염물질을 제거하고자 하였다. 유류 오염토양의 화학 생물학적 통합처리 공정의 현장 적용성 및 토양 미생물에 미치는 영향을 검증하기 위해 처리과정 전 후의 미생물 군집구조를 분석하였다. 또한 토양 내 유류 분해균을 분리하기 위해 탄소원으로 경유와 벙커C를 이용하여 농화배양을 수행하였다. 경유 분해균 10여종, 벙커 C 분해균 6종을 분리하여 분해능 및 동정을 시도하였다. 또한 유류 분해미생물의 consortia를 분자생물학적 기법으로 분석을 시도하였다.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2870-2874
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• 2011

Soil pollution around railroad has been occurred mainly by diesel and lubricant oil, which is difficult to treat due to high carbon number. In this study, we investigated the feasibility of inorganic-inorganic nanohybrid photo-catalyst for the remediation of diesel-contaminated railroad soil. Generally, the $TiO_2$ nanoparticle easily removes organic pollutants due to photo and natural clay of layer structure. Also, montmorillonite (MMT) have an excellent absorption property with organic component. So, we prepared $TiO_2$ pillared MMT nanohybrid photo-catalyst as a chemical oxidant through the integration of theses advantage. As a result, the removal efficiency of diesel was more than 45% at a laboratory-scale test with diesel concentration and the amount of $TiO_2$-MMT. In future, we will improve the removal efficiency of diesel to optimize experimental parameters and apply the field soil The remediation method using photo-catalyst can be used to clean up the railroad soil polluted with high concentration instead of common methods such as soil washing, bioremediation, etc..

• Journal of Soil and Groundwater Environment
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• v.19 no.3
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• pp.56-65
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• 2014

Contamination of explosive compounds in the soils of military shooting range may pose risks to human and ecosystems. As shooting ranges are located at remote places, active remediation processes with hardwares and equipments are less practical to implement than natural solutions such as bioremediaton. In this study, a series of experiments was conducted to select a suitable carbon source and to optimize dosing rate for the enhanced bioremediation of explosive compounds in surface soils and sediments of shooting ranges with indigenous microorganisms activated by external carbon source. Treatability study using slurry phase reactors showed that the presence of indigenous microbial community capable of explosive compounds degradation in the shooting range soils, and starch was a more effective carbon source than glucose and acetic acid in the removal of TNT. However, at higher starch/soil ratio, i.e., 2.0, the acute toxicity of the liquid phase increased possibly due to transformation products of TNT. RDX degradation by indigenous microorganisms was also stimulated by the addition of starch but the acute toxicity of the liquid phase decreased with the increase of starch/soil ratio. Taken together, the optimum range of starch/soil ratio for the degradation of explosive compounds without significant increase in acute toxicity was found to be 0.2 of starch/soil.

• Journal of Soil and Groundwater Environment
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• v.26 no.4
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• pp.20-26
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• 2021

In this work, an indigenous microbial consortium was obtained by selectively cultivating microbes using a long-aged petroleum-contaminated soil (Kuwait) containing recalcitrant petroleum hydrocarbons. The obtained microbial consortium was able to grow on and degrade the remaining petroleum hydrocarbons which could not have been utilized by the indigenous microbes in the original Kuwait soil. The following microbial community analysis using 16S rRNA gene sequencing suggested that the enhanced degradation of the remaining recalcitrant petroleum hydrocarbons by the novel microbial consortium may have been attributed to the selected bacterial populations belonging to Bacillus, Burkholderia, Sphingobacterium, Lachnospiraceae, Prevotella, Haemophilus, Pseudomonas, and Neisseria.

• Journal of the Korea Organic Resources Recycling Association
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• v.13 no.3
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• pp.89-96
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• 2005

In the present work, production of organophosphorus hydrolase (OPH) that is secreted in periplasmic space of recombinant Escherichia coli was performed for degradation of environmental toxic organophosphate compounds, paraoxon. The optimal conditions for enhancement of OPH production were 1.0 mM isopropyl-${\beta}$-D-thiogalactopytanoside (IPTG), 0.25 mM $Co^{2+}$, and 0.1 mM ethylenediamine tetraacetate (EDTA). Under these culture conditions, the maximum OPH production was $174Unit/L{\cdot}OD$. In addition, 1 mM of paraoxon was completely degraded by OPH. These results can be used as a bioremediation tool for removal of environmental toxic organophosphate compounds remaining in soil and aquatic environment.

• KSBB Journal
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• v.24 no.5
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• pp.453-457
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• 2009

Contamination of marine environment with hazardous and toxic chemicals is more common these days. Bioremediation is the application of microorganism or microbial processes to degrade environmental contaminant. Because of low water solubility and volatility of diesel, bioremediation is more efficient than physical and chemical methods. The objective of this study is biodegradation of diesel in sea water by using Rhodococcus fascians which is isolated petroleum-contaminated soil. R. fascians was cultured on sea water containing diesel to determine the diesel degradability. Changes in biodegradability of diesel with various inoculum sizes, diesel concentrations, initial pH, and culture temperature were analyzed by TPH analysis using gas chromatography. The inoculum size 2% was effective for biodegrdation of diesel in sea water by R. fascians. When diesel concentration was 5%, the growth of cell was inhibited by the toxicity of diesel. The optimal temperature and initial pH for degradation of diesel in sea water were $27^{\circ}C$ and pH 8.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.7
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• pp.764-769
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• 2006

In the electrokinetic(EK) process, oxygen production by electrolysis was proportional to current density. The dissolved oxygen (DO) concentration in anode tank and bioreactor increased with the circulation rate of electrolyte. The bacterial population in bioreactor rapidly increased by the supplement of current, but the DO concentration deceased by the increased bacterial oxygen consumption. From the results of EK bioremediation for pentadecane-contaminated soil, the bacterial population and removal efficiency at 1.88 $mA/cm^2$ were lower than those at 0.63 $mA/cm^2$. This is because the high oxygen production rate largely increased the production rate of organic acids, which reduced the electrolyte pH and bacterial activity. At 0.63 $mA/cm^2$, the highest bacterial population and removal efficiency could be obtained due to the appropriate oxygen production and small decrease in pH.