• Microbiology and Biotechnology Letters
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• v.51 no.1
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• pp.99-108
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• 2023

Several challenges arise in DNA extraction and gene amplification for airborne fungal metagenome analysis from a particulate matter (PM) samples. In this study, various conditions were tested to optimize the DNA extraction method from PM samples and polymerase chain reaction (PCR) conditions with primer set and annealing temperature. As a result of comparative evaluation of DNA extraction under various conditions, chemical cell lysis using buffer and proteinase K for 20 minutes and bead beating treatment were followed by using a commercial DNA extraction kit to efficiently extract DNA from the PM filter samples. To optimize the PCR conditions, PCR was performed using 10 primer sets for amplifying the ITS2 gene region. The concentration of the PCR amplicon was relatively high when the annealing temperature was 58℃ with the ITS3tagmix3/ITS4 primer set. Even under these conditions, when the concentration of the PCR product was low, nested PCR was performed using the primary PCR amplicon as the template DNA to amplify the ITS2 gene at a satisfactory concentration. Using the methods optimized in this study, DNA extraction and PCR were performed on 15 filter samples that collected PM2.5 in Seoul, and the ITS2 gene was successfully amplified in all samples. The optimized methods can be used for research on analyzing and interpreting the fungal metagenome of atmospheric PM samples.

• The Korean Journal of Zoology
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• v.22 no.3
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• pp.103-114
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• 1979

The authors observed the ultrastructure of the granular glands in the amphibian skin with an electron microscope. The specimens from the experimental animals (Bombina orientalis, Bufo bufo gargarizans, Rana nigromaculata and Rana rugosa) were fixed in 2.5% glutaraldehyde-paraformaldehyde fixative in phosphate buffer at pH 7.2 prior to fixation in 1% osmium tetroxide, dehydrated in graded ethanol and acetone, embedded in Epon 812 mixture, and sectioned with a LKB-ultramicrotome. the ultrathin sections were contrasted with uranyl acetate and lead citrate and observed with a JEOL-100B electron microscope. The results were as follws: 1. The granular gland in the amphibian skin consisted of the glandular epithelial and the myoepithelial cells. 2. The epithelial cells of the granular gland in the amphibian skin consisted of the dark cells but the light cells were also observed in that of Bombina orientalis. 3. The granular glands of the amphibian skin were in holocrine fashion. 4. The nuclei of the epithelial cells of the amphibian cutaneous granular glands were round or oval and showed small and large inforldings of nuclear envelope. Heterochromatins were mainly distributed near the nuclear envelope. Mitochondria were mainly distributed in the perinuclear portion and rough-surfaced endoplasmic reticulums were developed in the cytoplasm but smooth-surfaced endoplasmic reticulums were not well developed. 5. Secretory granules were round or oval and electron-dense and less electron-dense granules were observed. 6. The authors infer that the differences in electron density of the secretory granules in the granular glands of the amphibian skin are due to difference in the concentrations of secretory substances as related to the processes of its formation, and that those chemical components are identical.

• Journal of the Korean Electrochemical Society
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• v.27 no.1
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• pp.32-39
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• 2024

The key components of a Phosphoric acid fuel cell (PAFC) are an electrode catalyst, an electrolyte matrix and a gas diffusion layer (GDL). In this study, we introduced a microporous layer on the GDL of PAFC to enhance liquid electrolyte management and overall electrochemical performance of PAFC. MPL is primarily used in polymer electrolyte membrane fuel cells to serve as an intermediate buffer layer, effectively managing water within the electrode and reducing contact resistance. In this study, electrodes were fabricated using GDLs with and without MPL to examine the influence of MPL on the performance of PAFC. Internal resistance and polarization curves of the unit cell were measured and compared to each other to assess the impact of MPL on PAFC electrode performance. As the results, the application of MPL improved power density from 170.2 to 192.1 mW/cm². MPL effectively managed electrolyte and water within the matrix and electrode, enhancing stability. Furthermore, the application of MPL reduced internal resistance in the electrode, resulting in sustained and stable performance even during long-term operation.

• Journal of Applied Biological Chemistry
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• v.66
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• pp.258-265
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• 2023

After application of veterinary antibiotics, they may be partially metabolized before they are excreted by feces or urine either as unaltered form or as metabolites. Residual antibiotics enter the adjacent agricultural environments by spraying manure-based compost and liquid fertilizer on farmlands and lead to secondary pollution. The objective of this study was to compare the residual concentrations of 6 veterinary antibiotics by different production stages of liquid fertilizer from livestock manure recycling facilities. The relationship between concentration change of the residual antibiotics and the amount of liquid fertilizer component was also assessed. Pre-treatment showed the recovery of 63.4-106.7% at ppb level and the limit of quantification of 0.009-0.037 ㎍/L.As the result of analyzing the relationship between the residual concentrations of antibiotics and the amount of N component in liquid fertilizer by different production stages, the residual concentrations of antibiotics and N tended to decrease as the stabilization period elapsed during the liquid fertilization process. Average concentrations of sulfamethazine in raw materials, middle and final products of liquid fertilizer were 40.85, 26.17, 3.54 ㎍/L, respectively. Those of chlortetracycline decreased from 2.32 to 1.25 ㎍/L. The other 4 antibiotics also showed a decreasing trend by different production stages of liquid fertilizer. The amount of liquid fertilizer component N decreased from 0.21 to 0.096% by production stages of liquid fertilizer. It is considered that the correlation between residual antibiotic concentrations and N content can be applied as basic data for setting antibiotic reduction indicators.

• Applied Biological Chemistry
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• v.40 no.1
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• pp.12-17
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• 1997

Three strains of lactic acid bacteria were isolated from fish and shrimp pickles. Two strains were identified as Lactobacillus casei, and one strain as L. Pentosus, respectively. All three strains were used as starters in producing yogurts. The physico-chemical characteristics of yogurts were examined. The original pH, titratable acidity, visicosity and viable cell counts of the yogurts were $4.03{\sim}4.26,\;1.049{\sim}l.217%,\;1,772{\sim}2,232\;cps\;and\;1.4{\times}10^9{\sim}1.6{\times}10^9\;cfu/ml$, respectively. In evaluating buffer capacity, $12.50{\sim}14.06\;ml$ 1.0N HCl was consumed to titrate 100 ml of yogurt to pH value 2 units below the original pH value and $9.46{\sim}13.06\;ml$ of 1.0N NaOH was consumed to pH value 4 units above the original pH value. The ${\beta}-galactosidase$ activity reached maximum at 48 hrs, and reduced gradually during fermantation. After 2 hr incubation of yogurts at $37^{\circ}C$ under different pH conditions, ${\beta}-galactosidase$ activities of three strains were reduced to 50% at pH 3.5, but there were no remaining activities neither at pH 2.5 nor at pH 1.5. Under the same pH conditions the number of viable cells decreased to $1.9{\times}10^6{\sim}1.8{\times}10^8\;cfu/ml$ at pH 2.5 and $1.0{\times}10^3{\sim}2.4{\times}10^5$ at pH 1.5, respectively. However, no significant difference was found at pH 3.5.

• Journal of Korean Society of Forest Science
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• v.86 no.3
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• pp.324-333
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• 1997

The research has been made for the effects of the pollution by the abandoned coal mine drainage on the physical and chemical properties of soil, stream sediment and soil water. The soils overspreaded by the abandoned coal don't develop solum and the bulk density is $1.83g/m^3$, compared with $1.14-1.38g/m^3$ in the other forest soils. The soil pH range in coal bearing region ie, from 4.01 to 4.11 and non-coal bearing soil range is from 5.03 to 5.13. Heavy metals such as As, Cr, Ni, Mo and Ba of coal bearing soils and polluted stream sediments have larger concentration than those of non-coal content and non-polluted. Especially As and Mo concentrations are largely high in coal bearing. The relative ratios $K_2O/Na_2O$ of geochemical elements are higher in coal bearing soil and polluted stream sediments than those of non-coal bearing soils and non-polluted stream sediments as well as black shales of the Changri Formation. However, $MgO+Fe_2O_3+TiO_2/CaO+K_2O$ are the opposite trends, so that the ratios are lower in the polluted regions. The soil water pHs in the polluted regions are the strong acid(pH3.4-4.2) and buffer capacity of the polluted soil is low because canons such as $Na^+$, $K^+$, $Mg^{+2}$are leached by the acidification.

• Journal of the Korean Chemical Society
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• v.54 no.5
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• pp.556-566
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• 2010

A new kinetic spectrophotometric method is developed for the measurement of Mn(II) in natural water samples. The method is based on the catalytic effect of Mn(II) with the oxidation of Gallocyanin by $KIO_4$ using nitrilotriacetic acid (NTA) as an activation reagent at 620 nm. The optimum conditions obtained are $4.00{\times}1^{-5}\;M$ Gallocyanin, $KIO_4$, $1.00{\times}10^{-4}\;M$ NTA, 0.1 M HAc/NaAc buffer of pH = 3.50, the reaction time of 5 min and the temperature of $30^{\circ}C$. Under the optimum conditions, the proposed method allows the measurement of Mn(II) in a range of $0.1\;-\;4.0\;ng\;mL^{-1}$ and with a detection limit of down to $0.025\;ng\;mL^{-1}$. The recovery efficiency in measuring the standard Mn(II) solution is in a range of 98.5 - 102%, and the RSD is in a range of 0.76 - 1.25%. The newly developed kinetic method has been successfully applied to the measurement of Mn(II) in both some environmental water samples and certified standard reference river water sample, JAC-0031 with satisfying results. Moreover, few cations and anions interfere with the measurement of Mn(II). Compared with the other catalytic-kinetic methods and instrumental methods, the proposed kinetic method shows fairly good selectivity and sensitivity, low cost, cheapness, low detection limit and rapidity. It can easily and successfully be applied to the real water samples with relatively low salt content and complex matrices such as bottled drinking water, cold and hot spring waters, lake water, river water samples.

• Korean Journal of Food Science and Technology
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• v.7 no.4
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• pp.200-207
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• 1975

This experiment was carried out to investigate the chemical composition and microflora of soy sauce during storage under the different temperature. The results obtained are as follows. (1) Total nitrogen, color density, specific gravity and sodium chloride concentration of soy sauce showed a increasing tendency in the progress of storage period. Open-storage state at $30^{\circ}C\;and\;15^{\circ}C$ were responsible to the increase of components as compare with close-storage state at $5^{\circ}C$. (2) pH and buffer action were not almost changed during the storage. (3) Alcohol and sugar contents of soy sauce showed a decreasing tendency in the process of storage period, especially in the case of open state alcohol being almost disappeared within 11 months in all groups. (4) The number of common bacteria in one ml of soy sauce were counted as $96{\times}10^4$ before pasteurization and $10^3$ after pasteurization. The osmophilic bacteria was counted as $38{\times}10^4$, $10^2$ after pasteurization. (5) The spore number of mold in one ml of soy sauce were counted $32{\times}10^7$ before pasteurization, 58 after pasteurization and 10 to $10^2$ in the progress of storage period. (6) The bacteria number of soy sauce were somewhat decreased with the passing, of the time. The group of high temperature and open state were more notable than low temperature and close state.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.588-593
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• 2022

Terephthalaldehyde (TPA) is introduced as a cross liker to enhance electron transfer of hemin-based cathodic catalyst consisting of polyethyleneimine (PEI), carbon nanotube (CNT) for hydrogen peroxide reduction reaction (HPRR). In the cyclic voltammetry (CV) test with 10 mM H₂O₂ in phosphate buffer solution (pH 7.4), the current density for HPRR of the suggested catalyst (CNT/PEI/hemin/PEI/TPA) shows 0.2813 mA cm^-2 (at 0.2 V vs. Ag/AgCl), which is 2.43 and 1.87 times of non-cross-linked (CNT/PEI/hemin/PEI) and conventional cross liker (glutaraldehyde, GA) used catalyst (CNT/PEI/hemin/PEI/GA), respectively. In the case of onset potential for HPRR, that of CNT/PEI/hemin/PEI/TPA is observed at 0.544 V, while those of CNT/PEI/hemin/PEI and CNT/PEI/hemin/PEI/GA are 0.511 and 0.471 V, respectively. These results indicate that TPA plays a role in facilitating electron transfer between the electrodes and substrates due to the π-conjugated cross-linking bonds, whereas conventional GA cross-linker increases the overpotential by interrupting electron and mass transfer. Electrochemical impedance spectroscopy (EIS) results also display the same tendency. The charge transfer resistance (R_ct) of CNT/PEI/hemin/PEI/TPA decreases about 6.2% from that of CNT/PEI/hemin/PEI, while CNT/PEI/hemin/PEI/GA shows the highest R_ct. The polarization curve using each catalyst also supports the superiority of TPA cross liker. The maximum power density of CNT/PEI/hemin/PEI/TPA (36.34±1.41 μWcm^-2) is significantly higher than those of CNT/PEI/hemin/PEI (27.87±0.95 μWcm^-2) and CNT/PEI/hemin/PEI/GA (25.57±1.32 μWcm^-2), demonstrating again that the cathode using TPA has the best performance in HPRR.

• Korean Journal of Food Science and Technology
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• v.15 no.2
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• pp.128-132
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• 1983

The apple seed contained 25.96% of crude fat and 37.62% of crude protein. The lipid fractions obtained by cilicic column chromatography were mainly composed of about 93.52% neutral lipid, whereas compound lipid was only 6.48% level. Among the neutral lipid separated by thin layer chromatography, triglyceride was 92.17%, sterol ester, sterol, diglyceride and free fatty acid were 3.53, 2.25, 1.44 and 0.56, respectively. The predominent fatty acids of total and neutral lipids were linoleic acid (59.79-69.37%) and oleic acid (20.04-29.82%), but those of glycolipid and phojspholipid were linoleic acid (29.20-36.04%). The major fatty acids of triglyceride separated from neutral lipid were oleic acid (44.31%), linoleic acid (36.66%) and palmitic acid (12.48%). The salt soluble protein of apple seed was highly dispersible in 0.02M sodium phosphate buffer containing about 1.0M $MgSO_4$, and the extractability of seed protein was 37%, Glutamic acid was the major amino acid in salt soluble protein, followed by arginine and aspartic acid. The eletrophoretic analysis showed three bands in apple seed protein, and the collection rate of the main protein fraction purified by Sephadex G-100 and G-200 was 76.6%. Glutamic acid, aspartic acid and arginine were the major amino acids of the main apple seed protein. The molecular weight for the main protein of the apple seed was estimated to be 45,000.