• Asian Journal of Turfgrass Science
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• v.21 no.2
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• pp.113-126
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• 2007

Mineral nutrients and population dynamics of soil microbes in the root zones of zoysiagrass infected by Rhizoctonia solani AG2-2 and that of healthy plants were sampled from ten golf courses using a cup cutter(diameter $10\;cm\;{\times}\;8\;cm$ deep). Analysis of variance(ANOVA) showed significant differences in content of $NO_3$-N(P = 0.05), $NH_4$-N(P = 0.1), and K(P = 0.1) between infected and healthy samples. The content of $NO_3$-N in the soils of large patch was 9.49 mg/kg and that in soil of healthγ plants was 7.02 mg/kg. However, the content of $NH_4$-N in the soil of large patch was 12.02 mg/kg whereas 14.40 mg/kg for the soil under the healthy plants. The content of K in the soil of large patch was lower than that of soil of healthy plants. There was few numbers of Pseudomonas colonies In the soils of large patch compared to that of healthy plants. These results indicated that the content of $NO_3$-N, NH4-N, and K and the microbial population dynamics in root zones correlated to occurrence of large patch.

• Journal of Soil and Groundwater Environment
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• v.19 no.4
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• pp.62-69
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• 2014

In the results of monitoring nitrate concentration in more than 8,000 groundwater wells around agro-livestock, the average and maximum nitrate concentration was 9.4 mg/L and 101.2 mg/L, respectively. Since about 31% of the monitoring wells was exceed the quality standard for drinking water, nitrate control such as remediation or source regulation is required to conserve safe-groundwater in South Korea. Typical nitrate-treatment technologies include ion exchange, reverse osmosis, and biological denitrification. Among the treatment methods, biological denitrification by indigenous microorganism has environmental and economic advantages for the complete elimination of nitrate because of lower operating costs compared to other methods. Major mechanism of the process is microbial reduction of nitrate to nitrite and nitrogen gas. Three functional genes (nosZ, nirK, nirS) that encode for the enzyme involved in the pathway. In this work, we tried to develop simple process to determine possibility of natural denitrification reaction by monitoring the functional gene. For the work, the functional genes in nitrate-contaminated groundwater were monitored by using PCR with specific target primers. In the result, functional genes (nosZ and nirK) encoding denitrification enzymes were detected in the groundwater samples. This method can help to determine the possibility of natural-nitrate degradation in target groundwater wells without multiplex experimental process. In addition, for field-remediation application we selected nitrate-contaminated site where 200~600 mg/L of nitrate is continuously detected. To determine the possibility of nitrate-degradation by stimulated-natural attenuation, groundwater was sampled in two different wells of the site and nitrate concentration of the samples was 300 mg/L and 616 mg/L, respectively. Fumarate for different C/N ratio was added into microcosm bottles containing the groundwater to examine denitrification rate depending on carbon concentration. In the result, once 1.5 times more than amount of fumarate stoichiometry required was added, the 616 mg/L of nitrate and 300 mg/L of nitrate were completely degraded in 8 days and 30 days. The nitrite, byproduct of denitrification process, was also completely degraded during the experimental period.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.6
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• pp.442-446
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• 2007

From the rhizoplane and rhizosphere of pepper, tomato, lettuce, pasture, and grass, unsoluble inorganic phosphate solubilizing bacterial strains were isolated using plate base assay on Pikovskaya's medium. Two strains, CL-1 and CL-2, which produced largest halo on plates (indicative of phosphate solubilization)were selected for further studies. Based on these biochemical and 16S rRNA analysis strains CL-1, CL-2 were found to be as species of Pseudomonas sp. and Kluyvera sp., respectively. In broth assay Pseudomonas sp. CL-1 and Kluyvera sp. CL-2 solubilized insoluble phosphate by 193.4 mg and $493.6P\;mg\;L^{-1}$, respectively after $3^{rd}$ day inoculation. These effecient phosphate solubilizing bacteria have a potential to be developed as microbial based fertilizer in future.

• Korean Journal of Food Science and Technology
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• v.53 no.5
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• pp.657-668
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• 2021

We prepared the growth and survival models of enterohemorrhagic Escherichia coli (EHEC) and Campylobacter jejuni in milk as a function of temperature and assessed the microbiological risks associated with the consumption of whole milk. EHEC and C. jejuni were not detected in whole milk (n=195) in the retail market. The minimum growth temperature of EHEC in milk was 7℃. The lag time of EHEC in whole milk was longer than that in skim milk. The survival ability of C. jejuni in milk was better at 4℃ than at 10℃. Lower delta values were observed in whole milk than in skim milk, indicating that C. jejuni survived better in skim milk. The probability of foodborne illness from whole milk consumption was 5.70×10^-5 for EHEC and 9.86×10^-9 for C. jejuni. Sensitivity analysis results show that the market temperature of EHEC and the dose-response model of C. jejuni are correlated with the probability of foodborne illness.

• Journal of Environmental Impact Assessment
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• v.27 no.6
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• pp.582-594
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• 2018

In this study, the vertical and horizontal flow wetlands were combined in series to create conditions for flow in the exhalation and anaerobic state with the aim of monitoring the variability and reduction of dissolved organic matterin the bio-reactive artificial wetlands, and the performance assessment was conducted as acrylic reaction groups by designing artificial wetlands that filled the functionalresiduals. In case of artificial wetlands in vertical and horizontal planes, the concentration of dissolved oxygen (DO) in the reaction tank was measured as 2.7 mg/L in the vertical flow wetlands under exhalation, and N.D. in the horizontal flow artificial wetlands under anaerobic conditions. The test was carried out by changing the operation time to 140 min, 80 min, and 60 min. The test was conducted with the same natural operation time of 20 min depending on the operation time. All hours of operation were shown to be due to microbial activity. In 3D-EEM, it was found that the longer the driving time was taken, the more reduction the organic compounds in the areas of insoluble human resources, III and V. Further research on the mechanism analysis of future reduction effects is expected to be carried out, but the findings are expected to contribute to the development of technologies for reducing obfuscated substances using artificial wetlands in the future.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.1
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• pp.63-71
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• 2019

Objective: The aim of the study was to investigate the effect of zinc-bearing palygorskite (Zn-Pal) on rumen fermentation by in vitro gas-production system. Methods: In trial, 90 incubators were evenly divided into five groups: control (0% Zn-Pal), treatment I (0.2% Zn-Pal), treatment II (0.4% Zn-Pal), treatment III (0.6% Zn-Pal), and treatment IV (0.8% Zn-Pal). The contents of zinc for treatments were 0, 49, 98, 147, 196 mg/kg, respectively. The main chemical composition and microstructure of Zn-Pal was investigated by X-ray diffraction. The physicochemical features were evaluated by Zeta potential analysis, cation-exchange capacity, ethylene blue absorption and specific surface area (the Brunauer-Emmett-Teller method). In vitro gas production (GP) was recorded at 3, 6, 9, 12, 18, 24, 36, 48, 60, and 72 h incubation. Incubation was stopped at 0, 6, 12, 24, 48, and 72 h and the inoculants were tested for pH, microbial protein yield (MCP), $NH_3-N$, volatile fatty acids (VFAs), lipopolysaccharide (LPS). Results: The results showed that the GP in the treatment groups was not significantly different from the control groups (p>0.05). Compared to the control group, pH was higher at 24 h, 48 h (p<0.05), and 72 h (p<0.01) (range 6 to 7). The concentration of $NH_3-N$ in the three treatment groups was higher than in the control group at 24 h (p<0.01), meanwhile, it was lower at 48 h and 72 h (p<0.01), except in the treatment IV. The concentration of MCP in treatment I group was higher than in the control at 48 h (p<0.01). Compared with control, the LPS concentration in treatment III became lower at 12 h (p<0.05). Total VFAs in treatments were higher than in the control at 24 h, 48 h (p<0.05). Conclusion: These results suggest that the addition of Zn-Pal can improve the rumen fermentation, especially when adding 0.2% Zn-Pal.

• Ocean and Polar Research
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• v.41 no.2
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• pp.89-97
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• 2019

Long chain plant waxes (n-alkanes, n-alkanoic acids, and n-alcohols) and their carbon isotopic compositions (${\delta}^{13}C$) in geologic archives are valuable tools for paleovegetation reconstruction. However, the sensitivity of different plant wax constituents to vegetation shift is not well understood. This study explores controls on the variation in ${\delta}^{13}C$ values of long-chain n-alkanes ($C_{27}$ to $C_{33}$) and n-alkanoic acids ($C_{26}-C_{30}$) in the Gulf of Mexico core sediments (ODP 625B) near the Mississippi River delta. n-Alkanoic acids' ${\delta}^{13}C$ values were higher than those of n-alkanes by 1-2‰ on average and such a pattern is the opposite from their isotope fractionation observed in living plants: 1-2‰ smaller in n-alkanes than n-alkanoic acids. We attribute this offset to contributions from aquatic plants or microbes that produce high concentrations of $^{13}C-enriched$ long-chain n-alkanoic acids. The sensitivity of n-alkanes and n-alkanoic acids to vegetation and climate varied among chain lengths. The $n-C_{33}$ alkanes were most sensitive to $C_4$ grassland expansion among n-alkane homologues, while no specific trend was observed in n-alkanoic acids. This is due to the similarity in n-alkanoic acid concentrations between $C_3$ and $C_4$ plants by homologues and low terrestrial plant-derived n-alkanoic acid contributions to the sediments. The results of this study suggest that long chain n-alkanoic acids' ${\delta}^{13}C$ values in sediments may be influenced by contributions from different sources such as aquatic plants or microbial inputs and therefore interpretations regarding this matter should be cautiously formulated. We suggest that there is a need for further studies on characterizing long-chain n-alkanoic acids ($C_{26}-C_{34}$) in aquatic plants and microbes from various climates and environments in order to investigate their production and integration into sedimentary archives.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.1
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• pp.27-36
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• 2019

Purpose: The aims of this study were to evaluate the dentist's awareness and the actual status of infection control of noncritical dental instruments. Materials and Methods: 40 dental clinics in Daejeon, South Chungcheong, North Chungcheong and North Jeolla provinces were surveyed. The questionnaire was delivered to the dentists belonging to those clinics, and the awareness and the practice of infection control were examined. The microbial contamination on the surface of five noncritical instruments (impression gun, light curing unit, 3-way syringe, shade guide, and dental floss dispenser) used by them was measured with an ATP luminometer. Correlation analysis between the awareness and the actual state of infection control was conducted. Results: Awareness and frequency of infection control was highest in the 3-way syringe. Surface disinfection using disinfectant was most frequent in all instruments. 3-way syringes and shade guides were less contaminated than impression guns, light curing units, and dental floss dispensers. Conclusion: 3-way syringes had a significant correlation between user awareness of infection control and surface contamination, and the higher awareness, the lower the contamination measurement was shown.

• Korean Journal of Microbiology
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• v.54 no.4
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• pp.354-361
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• 2018

This study was carried out to isolate soil bacteria with antimicrobial activity and evaluate antimicrobial substances produced by isolated bacteria. Among many isolates Bacillus subtilis DS660 and Paenibacillus polymyxa DS842 showed high antimicrobial activities against 6 species of microbial residents on human skin and 3 species of pathogenic bacteria. DS660 and DS842 showed 15.3~26.8 and 11.3~27.5 mm of inhibition zone diameter, respectively on nutrient agar medium against most target bacteria and fungi. DS660 and DS842 produced $57{\pm}8$ and $170{\pm}15{\mu}mol/ml$ of siderophore, respectively as an antimicrobial substance. Analysis of ethyl acetate extract of culture supernatants of DS660 and DS842 suggested production of glycolipid biosurfactant which reduced surface tension of culture supernatant of DS660 and DS842 from 60.0 to 40.3 and 30.3 mN/m, respectively. DS660 and DS842 also showed $169.2{\pm}9.9$ and $357.2{\pm}13.7nmol/min/mg$ protein of ${\beta}-1,3$-glucanase activity, respectively, and hydrolyzed cell wall components of 3 bacterial species. These results suggest that B. subtilis DS660 and P. polymyxa DS842 may be utilized as an environment-friendly biocontrol agent against some skin microbes and pathogenic bacteria.

• Journal of Life Science
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• v.29 no.2
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• pp.248-255
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• 2019

This research confirmed the diversity and characterization of gut microorganisms isolated from the intestinal organs of Muraenesox cinereus, collected on the Samcheonpo Coast and Seocheon Coast in South Korea. To isolate strains, Marine agar medium was basically used and cultivated at $37^{\circ}C$ and pH7 for several days aerobically. After single colony isolation, totally 49 pure single-colonies were isolated and phylogenetic analysis was carried out based on the result of 16S rRNA gene DNA sequencing, indicating that isolated strains were divided into 3 phyla, 13 families, 15 genera, 34 species and 49 strains. Proteobacteria phylum, the main phyletic group, comprised 83.7% with 8 families, 8 genera and 26 species of Aeromonadaceae, Pseudoalteromonadaceae, Shewanellaceae, Enterobacteriaceae, Morganellaceae, Moraxellaceae, Pseudomonadaceae, and Vibrionaceae. To confirm whether isolated strain can produce industrially useful enzyme or not, amylase, lipase, and protease enzyme assays were performed individually, showing that 39 strains possessed at least one enzyme activity. Especially the Aeromonas sp. strains showed all enzyme activity tested. This result indicated that isolated strains have shown the possibility of the industrial application. Therefore, this study has contributed for securing domestic genetic resources and the expansion of scientific knowledge of the gut microbial community in Muraenesox cinereus of South Korea.