• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.40-44
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• 2003

Soil-borne infectious disease including Pythium aphanidermatum and Rhizoctonia solani causes severe damage to plants, such as cucumber. This soil-borne infectious disease was not controlled effectively by chemical pesticide. Since these diseases spread through the soil, chemical agents are usually ineffective. Instead, biological control, including antagonistic microbe can be used as a preferred control method. An efficient method was developed to select an antagonistic strain to be used as a biological control agent strain. In this new method, surface tension reduction potential of an isolate was included in the ‘decision factor’ in addition to the other factors, such as growth rate, and pathogen inhibition rate. Considering these 3 decision factors by a statistical method, an isolate from soil was selected and was identified as Bacillus sp. GB16. In the pot test, this strain showed the best performance among the isolated strains. The lowest disease incidence rate and fastest seed growth was observed when Bacillus sp. GB16 was used. Therefore this strain was considered as plant growth promoting rhizobacteria (PGPR). The action of surface tension reducing component was deduced as the enhancement of wetting, spreading, and residing of antagonistic strain in the rhizosphere. This result showed that new selection method was significantly effective in selecting the best antagonistic strain for biological control of soil-borne infectious plant pathogen. The antifungal substances against P. aphanidermatum and R. solani were partially purified from the culture filtrates of Bacillus sp. GB16. In this study, lipopeptide possessing antifungal activity was isolated from Bacillus sp. GB16 cultures by various purification procedures and was identified as a surfactin-like lipopeptide based on the Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), high performance liquid chromatography mass spectroscopy (HPLC-MS), and quadrupole time-of-flight (Q-TOF) ESI-MS/MS data. The lipopeptide, named GB16-BS, completely inhibited the growth of Pythium aphanidermatum, Rhizoctonia solani, Penicillium sp., and Botrytis cineria at concentrations of 10 and 50 mg/L, respectively. A novel method to prevent the foaming and to provide oxygen was developed. During the production of surface active agent, such as lipopeptide (surfactin), large amount of foam was produced by aeration. This resulted in the carryover of cells to the outside of the fermentor, which leads to the significant loss of cells. Instead of using cell-toxic antifoaming agents, low amount of hydrogen peroxide was added. Catalase produced by cells converted hydrogen peroxide into oxygen and water. Also addition of corn oil as an oxygen vector as well as antifoaming agent was attempted. In addition, Ca-stearate, a metal soap, was added to enhance the antifoam activity of com oil. These methods could prevent the foaming significantly and maintained high dissolved oxygen in spite of lower aeration and agitation. Using these methods, high cell density, could be achieved with increased lipopeptide productivity. In conclusion to produce an effective biological control agent for soil-borne infectious disease, following strategies were attempted i) effective screening of antagonist by including surface tension as an important decision factor ii) identification of antifungal compound produced from the isolated strain iii) novel oxygenation by $H_2O_2-catalase$ with vegetable oil for antifungal lipopeptide production.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.563-566
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• 2000

In order to obtain microbial endochitosanase for enzymatic production of chitooligosaccharides from chitosan, we screened four microbes from soil and selected. Bacillus sp. HSB-21 which showed highest activity. Chitosanase, produced from isolating microbe, was endo-type and molecular mass of the enzyme was estimated as 21,000 by active staining. Its optimum pH and temperature were 5.5 and $50^{\circ}C$, respectively. It was stable in the pH range of 3.0 to 8.0 and up to $40^{\circ}C$. It did not produce chitomonosaccharide and produced chitooligosaccharide ranging from chitobiose to chitooctaose as major end-products from chitosan. The chitosanase from Bacillus sp. HSB-21 can be applicable to enzymatic production of chitooligosaccharide which has high degree of polymerization .

• KOREAN JOURNAL OF CROP SCIENCE
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• v.58 no.1
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• pp.78-83
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• 2013

The excessive and indiscriminate use of chemical fertilizers in the past has brought serious soil and other environmental problems so alternatives over this agrochemical are being searched. Our study focuses on the effects of expanded rice hull inoculated with selected beneficial microorganisms on growth (through agronomic characters), yield and yield components, and grain quality indices of rice. Results showed that favorable effects of different expanded rice hull preparations were not readily apparent at vegetative stage and only treatments with supplemental chemical fertilizer application were comparable with the conventional practice. Expanded rice hull combined with 50% rate of chemical fertilizer exhibited a significantly higher yield (6,471 kg $ha^{-1}$) over conventional practice (5,719 kg $ha^{-1}$). Good milling quality indices were observed in treatments having 50% chemical fertilizers plus alternatives from expanded rice hull. Finally, we demonstrated that chemical fertilizer rate can potentially be reduced into 50% if combined with expanded rice hull, and show even better output than chemical fertilizer alone.

• Journal of Soil and Groundwater Environment
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• v.21 no.4
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• pp.42-49
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• 2016

Step-drawdown pumping tests for identifying the improvement of groundwater well performance after rehabilitation treatments were conducted in three longstanding wells. Three selective mechanical treatment methods including power bubble, high-voltage electric pulse, and air surging were applied to these wells and the applicability of these methods to secure additional groundwater resources were evaluated quantitatively. Commonly, drawdown at final stage of stepdrawdown pumping tests after rehabilitation decreased by as much as 0.61~0.70 meters compared to those before rehabilitation. In addition, final specific drawdown values of three wells increased from 9% to 14% after rehabilitation. Formation loss coefficient and well loss coefficient decreased to 6.1% and 60.6%, respectively, indicating some clogging materials by precipitation/corrosion/microbe within pores of aquifer materials, gravel packs, and screens were effectively removed by applied methods. Decrease of formation loss coefficient was higher in the well applied by the power bubble method meanwhile high-voltage electric pulse method demonstrated the higher decrease of well loss coefficient. Additionally secured groundwater amounts after rehabilitation ranged from 23.3 to 32.1 m³/day, which account for 8~16% of initially developed pumping rates of the wells. From the results of this study, the effective selection of rehabilitation treatments considering aquifer characteristics are expected to contribute to secure groundwater resources for irrigation as well as to plan systematic management program for groundwater resources in rural area.

• Journal of the Korean Geotechnical Society
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• v.28 no.9
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• pp.85-95
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• 2012

The method of using organic acid is more environment-friendly for it improves the strength of the ground. The method of proliferating microbes makes soil particle bonded, finally improves the strength of the ground and decreasing permeability. Although there has been the research on the effect of strength increasing, there has never been a research on the evaluation of field application. In this paper, through the light drop weight test, the dynamic cone penetration test, the field density test, the variation of strength was investigated in the mixed ground with organic acid for 56 days. As the results of the field test, it was found that the strength and stiffness of the ground increased with organic acid, and that through SEM-EDS, the precipitation of calcium carbonate made by specified microbe obviously increased with organic acid material and so the ground was improved. Therefore, the sustainable development of this method needs to be analysed more in the future.

• Microbiology and Biotechnology Letters
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• v.48 no.2
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• pp.99-112
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• 2020

Rhizoremediation, based on the ecological synergism between plant and rhizosphere microorganisms, is an environmentally friendly method for the remediation of petroleum hydrocarbon-contaminated soils. In order to mitigate global climate change, it is necessary to minimize greenhouse gas emissions while cleaning-up contaminated soils. In rhizoremediation, the main factors affecting pollutant remediation efficiency and greenhouse gas emissions include not only pollutant and soil physicochemical properties, but also plant-microbe interactions, microbial activity, and addition of amendments. This review summarizes the development in rhizoremediation technology for purifying oil-contaminated soils. In addition, the key parameters and strategies required for rhizoremediation to mitigate climate change mediation are discussed.

• Research in Plant Disease
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• v.26 no.4
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• pp.202-209
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• 2020

Organic farming is necessary to sustainable agriculture, preserve biodiversity and continued growth the sector in agriculture. In organic farming, reduced usage of chemical agents that adversely affect human health and environment, employing amino acids and oil cake fertilizer, plant extracts, and microbial agents are used to provide safe agricultural products to consumers. To investigation microbiome structure, we proceeded on the pepper plant with difference fertilizers and treatments in organic agriculture for three years. The microbial communities were analyzed by the next generation sequencing approach. Difference soil microbiota communities were discovered base on organic fertilizer agents. Occurrences of virus and anthracnose diseases had a low incidence in conventional farming, whereas bacteria wilt disease had a low incidence in microbial agents treated plots. Microbe agents, which applied in soil, were detected in the microbial community and the funding suggested the applied microbes successfully colonized in the organic farming environment.

• Horticultural Science & Technology
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• v.32 no.6
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• pp.879-886
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• 2014

This study was conducted to test in vitro the antagonistic effect of composted liquid manure (CLM) against soil-borne turfgrass pathogenic fungi, Rhizoctonia solani AG-2-2 (IIIB) (brown patch), R. solani AG-2-2 (IV) (large patch), and Sclerotinia homoeocarpa (dollar spot) for environmentally friendly turfgrass management. CLMs were collected from 9 livestock excretion treatment facilities around the country including Gunwi (GW), Hapcheon (HC), Hoengseong (HS), Icheon (IC), Iksan (IS), Muan (MA), Nonsan (NS), and Yeoju (YJ). CLMs of IC, GW, and IS showed s ignificant (p < 0.05) mycelium growth inhibition that was 17.8%, 20.4%, and 48.0% against R. solani AG-2-2 (IIIB), R. solani AG-2-2 (IV), and S. homoeocarpa, respectively. A t otal of 110 bacterial isolates were obtained from the CLMs that showed antagonistic effects. Among them, 5, 4, and 10 microbe isolates showed promising antifungal activity against mycelium growth of R. solani AG-2-2 (IIIB), R. solani AG-2-2 (IV), and S. homoeocarpa, respectively. The bacterial isolates ICIIIB60, GWIV70, and ISSH20 effectively inhibited the mycelial growth of three soil-borne turfgrass pathogens. Selected bacterial isolates were identified as Alcaligenes sp., Bacillus licheniformis Ab2, and B. subtilis C7-3 through 16s rDNA gene sequence analysis. Among 5 fungicides, the most compatible fungicide with ICIIIB60, GWIV70, and ISSH20 was tebuconazol, toclofos-methyl and toclofos-methyl, respectively. These findings suggested that CLMs could be effectively used not only as organic liquid fertilizer sources but also as biological control agents for soil-borne turfgrass diseases such as brown patch, large patch, and dollar spot.

• Korean Journal of Environmental Agriculture
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• v.19 no.1
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• pp.62-66
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• 2000

This study was conducted to determine the soil chemical properties and microbial flora of platycodon and their effect on rhizome rot incidence. Sampling sites were Keochang 4, Kimhae 7, Haman 6, Chinju 6 and Koseong 3 fields in Kyongnam province and Hongcheong 6 fields in Kangwon province. The root disease incidence rate was in the order of Haman 56.8%, Hongcheon 52.5%, Kimhae 36.7%, Koechang 35.3%, Chinju 32.3%, Koseong 30.0%. The yield at the Chinju 36.17 Mg/ha was higher than that of Koseong 25.00 Mg/ha, Kimhae 13.57 Mg/ha, Koechang 11.75 Mg/ha, Haman 9.50 Mg/ha, Hongcheon 5.24 Mg/ha. The soil K, $NH_4-N$ content and EC value of injury root were higher than those of normal root. The root CaO content was positively correlated with yield $Y=20505X-367.9(R^2=0.129^{\ast})$. The Fe and Zn content of normal root were higher than those of injury root, while the T-N, $P_2O_5$ and $K_2O$ content of normal root were lower than those of injury root. The population of bacteria, actinomycetes and bacteria/fungi ratio increased in soil of normal root, but that of fungi decreased.

• Korean Journal of Organic Agriculture
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• v.32 no.1
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• pp.107-125
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• 2024

Three types of veterinary antibiotics, including oxytetracycline (OTC) and chlortetracycline (CTC) of tetracycline class and amoxicillin (AMX) of penicilline class, were artificially introduced into the irrigation water. The residue of veterinary antibiotics in the soil, the absorption-translocation of veterinary antibiotics into the red lettuce and young radish plant, and crops yield were investigated according to the agricultural water irrigation method (surface drip irrigation, underground drip irrigation, and sprinkler irrigation). There was no significant difference in the residue and translocation of veterinary antibiotics in the soils and crops according to the irrigation method and type of veterinary antibiotics (p>0.05). For the edible parts of red lettuce and young radish, all three types of veterinary antibiotics were found to be below the detection limit, indicating that the safety of the crops was secured. The translocation factor of red lettuce and young radish were found to be less than 0.3 and 0.2, respectively. However, continuous introduction of veterinary antibiotics in agricultural arable lands may have negative effects by affecting soil microbial activity and soil microbe species diversity, so continuous management is deemed necessary.