• Korean Journal of Ecology and Environment
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• v.36 no.3 s.104
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• pp.235-241
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• 2003

The effect of ultraviolet (UV) radiation on the characteristics of algae-derived dissolved organic matter (DOM) was examined by comparing the biodegradability and DOM fraction distribution of algal DOM before and after UV exposure. Algal DOM from two axenic cultures of Microcystis aeruginosa and Oscillatoria agardhii were irradiated for 24 h at a UV intensity of 42 W/$m^2$. A complete degradation of algal DOM during the UV exposure did not occur, remaining at constant concentrations of dissolved organic carbon(DOC). After UV exposure, however, microbial degradations were reduced by 17% in M. aeruginosa and 53% in O. agardhii, respectively, and decomposition rates also were two times lower in UV exposed algal DOM. In addition, the chemical compositions of algal DOM altered substantially after UV radiation exposure. The proportions of hydrophilic bases (HiB; protein-like DOM) decreased considerably in both algal DOM sources after UV exposure (16.8% and 20.0% of DOM, respectively), whereas those of hydrophilic acids (HiA; carboxylic acids-like DOM) increased as much as the decrease of the HiB fraction. Capillary ion electrophoresis (CE) analysis showed that several carboxylic acids increased significantly after UV exposure, further confirming an increase in HiA fractions. The results of this study clearly indicate that algal DOM can be changed in its chemical composition as well as biodegradability without complete degradation by UV radiation.

• Korean Journal of Soil Science and Fertilizer
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• v.6 no.3
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• pp.159-163
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• 1973

A by-product from glutamic acid fermentation prepared by treating the fermentation residue with sulfuric acid and ammonium hydroxide was studied in the light of its chemical properties by chemical analysis and X-ray diffraction technique. Its effectiveness as fertilizer was also investigated with corn as test plant. The results are summarized as following. 1. The chemical analyses and study with X-ray diffraction technique revealed that the by-product contains an appreciable quantity of water soluble ammonium as ammonium sulfate and ammonium chloride, water soluble amino acid and in-soluble organic carbon. Particularly, the X-diffraction pattern of the material indicated the presence of unidentified water soluble double salt of ammonium sulfate and ammonium chloride. 2. The water soluble ammonium in this material was found to be as effective as urea on the growth of corn plant. 3. The organic portion of the material was found to be equally effective on the growth of corn plant as the other sources of organic matter such as compost and rice bran. It was, however found that the organic matter in the fermentation residue is more persisting in the soil than the compost and rice bran. 4. It was noticed that the application of the fermentation by-product, lowers the soil pH significantly. Inspite of the pH lowering effect, the absorption of iron by corn plant was surpressed by the application of this material.

• Journal of the Korean Wood Science and Technology
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• v.38 no.3
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• pp.242-250
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• 2010

The aim of this study was to investigate the terpenoids of Total Volatile Organic Compounds (VOCs) released during drying of Cryptomeria japonica using the thermal extractor (TE). Considering the drying process of C. japonica, temperatures of TE were set at $27^{\circ}C$, $60^{\circ}C$, $80^{\circ}C$, $100^{\circ}C$, and $120^{\circ}C$, respectively. As the result, the emission factors of VOCs and terpenoids were increased as temperature increased. The amount of terpenoids included in VOCs emission factors were 87.5%, 81.6%, 83.6%, 90.1%, and 97.3% depending on above temperatures, respectively. Especially at$100^{\circ}C$ and $120^{\circ}C$, the amount of terpenoids were measured more than 90%. ${\delta}$-cadinene was the highest yield at each temperature and 32 types of terpenoids were collected. Emitted terpenoids were classified into the sesquiterpene group which consists of 15 carbon sources. These 32 sesquiterpenes were used for determining the useful bioactivity such as antifungal activity by the agar dilution. As the result, they showed the antifungal activity against Trichophyton rubrum, Trichophyton mentagrophytes, Microsporum gypseum. The 5,000 ppm concentration of terpenoids showed a strong activity with 100% against the 3 fungi. At the 1,000 ppm concentration of terpenoids, the antifungal activities against three fungi were 95.2%, 98.7%, and 97.3%, and their activities were a little inhibited at 100 ppm concentration.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.3
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• pp.365-376
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• 2006

The purpose of this study was to evaluate the efficacy of blocking the oxygen in the air during the polymerization of sealant. All curing were performed with various light curing units under the application of oxygen gel barrier, stream of nitrogen and carbon dioxide gas for inhibition of oxygen diffusion into sealant surface. The results of present study can be summarized as follows : 1. The amount of eluted TEGDMA form the specimens cured with all the three different light units in the stream of $N_2$ and $CO_2$ gas and application of Oxygen gel barrier($DeOx^{(R)}$) were significantly lower than in the room-air atmosphere (Control) (p<0.05). 2. In the $DeOx^{(R)}$ application, the amount of eluted TEGDMA the specimen cured with PAC light for 10seconds was less than that cured in the stream of $N_2$ and $CO_2$ atmospheric conditions (p<0.05) 3. In the LED using 10 or 20sec irradiation times under the stream of $N_2$ and $CO_2$, the eluted TEGDMA showed to be no statistically significant difference (p>0.05). 4. The microhardness from the specimens cured with all the three different light units under each treated conditions were significantly higher than in the room-air atmosphere (p<0.05). 5. The surface treatment by $DeOx^{(R)}$, $N_2$ and $CO_2$ reduces the thickness of oxygen inhibited layer by sp proximately 49% of the untreated control value.

• Journal of the Mineralogical Society of Korea
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• v.31 no.2
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• pp.113-121
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• 2018

Baekasan Acheon cave located in Hwasun-gun, Jeollanam-do is a natural limestone cave only found in this province. In this study, the mineralogical and geochemical characteristics of speleothems collected from Baekasan Acheon cave were identified and the capability of carbonate mineral formation by aerobic microorganisms enriched from the cave and the mineralogical and geochemical characteristics of carbonate minerals formed by the microorganisms were investigated. The samples of sediments (clay) and speleothems (shelfstone and cave coral) were collected at three sites in the cave. The samples of shelfstone and cave coral were identified mainly as carbonate mineral, Mg-rich calcite, and clay minerals were composed of quartz, muscovite, and vermiculite by X-ray diffraction (XRD) analysis. To cultivate the carbonate forming microorganisms, parts of the sediment and speleothems were placed in D-1 medium containing urea, respectively, and the growth of microorganisms was observed under the aerobic condition at room temperature. The capability of carbonate mineralization of the cultured Baekasan Acheon cave microorganisms was examined through adding 1% (v/v) of the cultured microorganisms and calcium sources, Ca-acetate or Ca-lactate, into the D-1 medium. XRD analysis showed that the microorganisms cultured in cave deposits formed calcium carbonate ($CaCO_3$) under all conditions, and these microbial carbonate minerals included calcite and vaterite. The morphological characteristics and chemical composition of biologically formed minerals were observed by SEM-EDS showed various crystal forms such as rhomboid, spherical, perforated surface with Ca, C, and O of major chemical components. The existence of such microorganisms in the cave can contribute the formation of carbonate minerals, and it is likely to affect the geochemical cycles of carbon and calcium in the cave.

• Korean Journal of Environmental Agriculture
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• v.15 no.3
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• pp.362-371
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• 1996

This study was conducted to investigate the biochemical properties of isolated bacteria, low temperature tolerant methanogens which were selected for use as inoculum for anaerobic fermentation of agricultural and livestock wasted at low temperature. The results, obtained were summarized as follows: Low temperature tolerant methanogens were isolated from the samples which showed the high methanogenesis rate by enrichment culture at low temperature in methanol medium. These methanogens, Methanobacterium M-251 and Methanobacterium M-253 were isolated from swampy sediment at latitude $56.9^{\circ}$, Methanosarcina mazei M-372 from lake sediment IV at latitude $55.0^{\circ}$ N, and Methanobacterium formicicum M-375 from tidal land soil at latitude $37.0^{\circ}N$, respectively. The isolated anaerobic bacteria could not use sugars as carbon sources. The optimum pH value for the growth of M-251 and M-375 was 6.8, but those for M-253 and M-372 6.5 and 7.0, respectively. The minimum growth temperature of isolated, M-251 and M-253 were $8^{\circ}C$ and the optimum temperature $30^{\circ}C$, while the minimum of M-392 and M-395 were $13^{\circ}C$ and the optimum $37^{\circ}C$. The growth rate of isolates at $17.5^{\circ}C$ were lower by 32-50% than that of $30^{\circ}C$. The isolated Methanobacterium strains such as M-251, M-253, and M-375 have lower cell yield, 0.38-1.21g/1M $CH_4$ than 1.14-1.51g/1M $CH_4$ of Methanosarcina mazei M-372.

• Microbiology and Biotechnology Letters
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• v.15 no.6
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• pp.388-395
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• 1987

In order to obtain a regulatory mutant strain with high cellulase activity, a newly isolated Penicillium verrculosum, strain F-3 was used as parental strain since it was proved to be an efficient cellulase producer. A number of experiments were conducted to determine the optimum conditions to in-duce mutagenesis and isolate the desirable mutant strains. Out of several restriction compounds tested, 1.5% oxgall was found to be most effective to restrict the colony size by suppressing overgrowth. Derepression of catabolites was employed as a criterion in selecting mutant strains with high cellulase productivity. Production of cellulase by Penicillium venculosum F-3 was suppressed when cultured on the media with more than 1% of glucose or glycerol. It was found that either irradiation with UV light for 19 mins or treatment with nitrosoguanidine at 200$\mu\textrm{g}$/m1 for 60 mins, induced mutagenesis at desired level, when the survival rate of the spore was 0.2% and 48%, respectively. Three mutant strains of F-3, UV-9, UV-10, and NTG-3 that had the highest cellulase productivity were finally selected, based on filter paper degradation rate, size of clearing zone on the screening plate and cellulase activity in the medium containing cellulose powder. When the mutant strains were compared with parental strain F-3, on the KC-M-W medium containing cellulose powder, the filter paper activities of UV-9, UV-10, and NTG-3 were increased by 34%, 55%, and 41%, respectively. However, the assimilation of cellobiose octaacetate by UV-9 or NTG-3 was markedly reduced. When the mutant UV-10 was grown on cellobiose octaacetate medium (CCA-4) in shaking flasks, the cellulase activities of the mutant increased by 20 to 50% compared to the parental strain. Excreation of soluble protein from the mutant also elevated up to 30%. The mutant also constitutively produced both CMCase and $\beta$-glucosidase, though at relatively low level, in the presence of glucose or cellobiose as carbon sources.

• Journal of Life Science
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• v.25 no.12
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• pp.1408-1414
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• 2015

In this study, to retain a stable bacterial inoculant, Bacillus strains showing antifungal activity were screened. The improved production, antifungal mechanism, and stability of the antifungal metabolite by a selected strain, AF4, a potent antagonist against phytopathogenic Botrytis cinerea, were also investigated. The AF4 strain was isolated from rhizospheric soil of hot pepper and identified as Bacillus subtilis by phenotypic characters and 16S rRNA gene analysis. Strain AF4 did not produce antifungal activity in the absence of a nitrogen source and produced antifungal activity at a broad range of temperatures (25-40℃) and pH (7-10). Optimal carbon and nitrogen sources for the production of antifungal activity were glycerol and casein, respectively. Under improved conditions, the maximum antifungal activity was 140±3 AU/ml, which was higher than in the basal medium. Photomicrographs of strain AF4-treated B. cinerea showed morphological abnormalities of fungal mycelia, demonstrating the role of the antifungal metabolite. The B. subtilis AF4 culture exhibited broad antifungal activity against several phytopathogenic fungi. The antifungal activity was heat-, pH-, solvent-, and protease-stable, indicating its nonproteinous nature. These results suggest that B. subtilis AF4 is a potential candidate for the control of phytopathogenic fungi-derived plant diseases.

• The Korean Journal of Mycology
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• v.40 no.1
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• pp.54-59
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• 2012

This study investigates the effect of ${\beta}$-glucans on the growth of Caenorhabditis elegans. Comparison was made among lipopolysaccharide (LPS) and ${\beta}$-glucans extracted from Phellinus baumii, in the presence of peptidoglycans which is available as the major carbon source from OP50, a non-pathogenic strain of Escherichia coli. When the three sources of carbohydrate were added singularly or in mixture to the culture media, a significant level of variation was observed with respect to fecundity. Addition of ${\beta}$-glucans appeared to increase the fecundity. When ${\beta}$-glucans was reinforced in the culture media, the fecundity increased at least 20 percent compared to the OP50-only media which exclusively contains peptidoglycans. In terms of life span, C. elegans showed a modest reduction when treated especially with ${\beta}$-glucans. C. elegans accumulated less fat in the ${\beta}$-glucans containing media different from the OP50 media. Based on the Sudan black staining, fat deposition significantly decreased corresponding to the ${\beta}$-glucans content in the media. On LPS-supplemented media, no difference was observed in fat deposition compared to the normal OP50 media. At the level of motility, ${\beta}$-glucans-treated worms moved more distance as well as LPS-treated worm. They also showed a comparable degree of motility under similar treatment with each source of carbohydrate. In conclusion, LPS and ${\beta}$-glucans, extracted from P. baumii, may not entirely replace the food required for C. elegans; however, it might be utilized as valuable alternative food source which C. elegans use as forms of carbohydrates in stead of peptidoglycan of OP50.

• Korean Journal of Soil Science and Fertilizer
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• v.20 no.3
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• pp.261-268
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• 1987

A green house experiment was conducted to find out the differences in the amount of biologically fixed nitrogen and kjeldahl nitrogen on the different soil texture, kinds and amounts of fertilizer nitrogen under light (photosynthetic $N_2$-fixation) and dark (heterotrophic $N_2$-fixation) condition in submerged paddy soil. The reults obtained were summarized as follows; 1. The amount of biologically fixed nitrogen per mg carbon from different organic matter was obtained as 0.13 mg in glucose, 0.09 mg in rice straw, and 0.07 mg in refused mushroom compost and barley straw under 60 days of incubation. 2. Nitrogen fixing activities were decreased with increase of fertilizer nitrogen and those tendency was pronounced more in sandy soil with application of urea than that of ammonium sulfate. 3. The application of ammonium sulfate in sandy soil under light condition was increased the photosynthetic $N_2$-fixation and the applied urea was remarkably reduced the heterotrophic $N_2$-fixation in sandy soil. The proportion of biologically fixed total nitrogen after experiment in sandy soil was obtained as 25% for dark(heterotrophic $N_2$-fixation) and 75% for light (photosynthetic $N_2$-fixation) condition. On the other hand, very similar biological $N_2$-fixing tendency was obtained between kinds of nitrogen fertilizer and two light condition in clayey soil. 4. The kjeldahl nitrogen was remarkably decreased after experiment under dark condition with application of urea than that of light condition with ammonium sulfate, and no remarkable decreasing tendency was obtained in clayey soil between two kinds of fertilizer nitrogen. 5. The high significant positive correlationship was obtained between calculated biological nitrogen fixation by acetylene reducing activity and kjeldahl nitrogen after experiment under light (y=0.8488X-5.9632, $r=0.9928^{**}$, n=21) and dark (y=0.8795X-7.1056, $r=0.9782^{**}$, n=21) condition. In this experiment condition, conversion factors of 6:1 was obtained from biological nitrogen fixation to soil nitrogen.