• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2001년도 춘계학술발표회 초록집
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• pp.73-73
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• 2001

Boron-containing materials have several excellent properties, such as superlnardness, insulation and non-Rinear optical property. Recently, oxynitride compounds, such as Si(ON), Ti(ON), became the promising materials applied in diffusion barrier layer and solar cell. With the expectation of obtaining the hybrid property, we have firstly grown the BON thin film by radio frequency (R.F.) plasma enhanced metalorganic chemical vapm deposition (PEMOCVD) with 100 kHz frequency and trimethyl borate precursor. The plasma source gases used in this study were Ar and $H_2$, and two kinds of nhmgen source gases, $N_2$ and <$NH_3$, were also employed. The as-grown films were characterized by XPS, IR, SEM and Knoop microlhardness tester. The relationship between the films hardness and the growth rate indicated that the hardness of the film was dependent on several factors such as nitrogen source gas, substrate temperature and film thickness due to the variation of the composition and the structure of the film. Both nitrogen and carbon content could raise the film hardness, on which nitrogen content did stronger effect than carbon. The smooth morphology and continuous structure was benefit of obtaining high hardness. The maximum hardness of BON film was about 10 GPa.

• Composites Research
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• 제36권6호
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• pp.408-415
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• 2023

질소 도핑에 의한 Pyridinic-N, Pyrrolic-N, Graphitic-N과 같은 결합 구성의 형성은 탄소나노소재의 물리적 특성을 조절하거나 새로운 물성을 부여하는 중요한 역할을 한다. 본 연구에서는 멜라민을 도펀트 소스로 혼합하여 탄소 나노튜브(CNT)의 질소 결합 구성을 조절하는 간단하고 비용 효율적인 접근 방식을 제안한다. Stirring, Bath sonication 및 Tip sonication과 같은 세 가지 기계적 방법을 통해 멜라민을 탄소나노튜브와 혼합한 후 열처리를 통해 질소 도핑을 진행하였다. CNT 대비 멜라민 비율이 높을수록 Pyrrolic-N의 비율이 높게 나타났으며 Stirring을 통해 혼합한 경우 가장 높은 Pyridinic-N의 비율을 나타내었다. 본 연구에서 제안한 방법은 기계적인 혼합 방법을 이용해 탄소나노튜브에 다양한 종류의 질소 도펀트를 선택적으로 형성할 수 있는 손쉬운 방법으로, 향후 질소가 도핑된 탄소나노물질의 응용을 용이하게 할 것으로 기대된다.

• 한국유기농업학회지
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• 제8권2호
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• pp.97-110
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• 2000

An organic agriculture should be managed by mixed farming in farm unit as a closed recycling system. Due to restricted purchased of fertilizers from outside, organic farmer has to deal with limited amount of nutrient source in farm unit. Especially the supply of the essential nutrient, nitrogen, mostly depends on legumes fixing nitrogen optimizing the site-adapted crop rotation. Dynamics of humus and metabolic plant carbon and active soil carbon compartment in active and passive humuspool by rotation system was explained, and dynamics of potentially mineralizable nitrogen in organic nitrogen and biomass was discussed. It was also discussed comparison of ammonia emission, potential greenhouse effect, primary energy input, acidification potential, CO2 emission between organic and conventional farming, the nitrate-nitrogen dynamic in the soil profile by organic, integrated and conventional farming system. In conclusion, it was suggested for Korean Organic Agriculture that the importance of legumes and green manures in rotation system for increase/maintenance of soil ferfility, and was pointed out the need of investment for environment impact of Korean organic farming implement.

• Journal of Microbiology and Biotechnology
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• 제4권2호
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• pp.146-150
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• 1994

Production of poly-$\beta$-hydroxybutyrate (PHB) in fed-batch fermentation was studied. Utilization of carbon for PHB biosynthesis was investigated by using feeding solutions with different ratios of carbon to nitrogen (C/N). It was observed that at a high C/N ratio carbon source was more preferably utilized for PHB accumulation while its consumption for cellular metabolism appeared to be more favored at a low C/N value. A high cell concentration (184 g/l) was achieved when ammonium hydroxide solution was fed to control the pH, which was also utilized as the sole nitrogen source. For the mass production of PHB, two-stage fed-batch operations were carried out where PHB accumulation was observed to be stimulated by switching the ammonium feeding mode to the nitrogen limiting condition. A large amount of PHB (108 g/l) was obtained with cellular content of 80% within 50 hrs of operation.

• 한국물환경학회지
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• 제27권4호
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• pp.461-466
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• 2011

The feasibility of utilizing food waste leachate as an external carbon source was tested to enhance biological nutrient removal from an industrial wastewater with an average flow rate of $164,800m^3/d$ and a low carbon/nitrogen ratio of 2.8. A considerable improvement in the removal of nitrogen and phosphorus was observed when a certain amount of the leachate, ranging from 70 to $142m^3/d$, was supplemented to the biological industrial wastewater treatment process. The addition of the leachate led to an increase in the BOD/N ratio (4.5) and the removal efficiency of nutritents from 29.7% to 71.7% for nitrogen and from 34.8% to 65.6% for phosphorus. However, an excessive dose of the leachate that significantly exceeded $120m^3/d$ caused serious operational problems, like oil-layer formation in the grit chamber and scum layer in the primary clarifier. Thus, an supplement of food waste leachate at a dose acceptable to an existing facilities can be a practical and effective means to enhance the nutrient removal from industrial wastewater and to dispose of the food waste leachate.

• Journal of Microbiology and Biotechnology
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• 제16권3호
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• pp.438-442
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• 2006

The formation of astaxanthin by Xanthophyllomyces dendrorhous mutant JH1 depends on the culture conditions. Therefore, the effects of inoculation rate (1-5%, v/v) and medium compositions (various carbon and nitrogen sources) on cell growth and astaxanthin formation in X. dendrorhous mutant JH1 were investigated. Inoculation at 3% (v/v) was optimal for cell growth and astaxanthin formation. The most effective carbon source for cell growth and astaxanthin formation was glucose, and the best nitrogen source was yeast extract. The 3% (w/v) glucose and 0.2% (w/v) yeast extract showed the best effect on cell growth and astaxanthin formation, compared with others tested. The 3% glucose, 0.2% yeast extract, $0.15%\;KH_{2}PO_{4}$, $0.05%\;MgSO_4$, $0.01%\;MnSO_4$, and $0.01%\;CaCl_2$ were selected for cell growth and astaxanthin formation. Under the conditions selected, the maximum concentrations of cell and astaxanthin obtained after 168 h of cultivation were 5.43 g/l and 28.20 mg/l, respectively.

• KSBB Journal
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• 제25권3호
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• pp.230-238
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• 2010

A microbial strain having high keratinase activity was isolated from the soil of poultry factories of Gyeonggi or Chungcheong-do. The isolated strain was identified as Bacillus sp. based on its morphological and biochemical characteristics. In this study, the optimal conditions for the production of keratinase by this strain were investigated. The optimal medium composition for the keratinase production was determined to be 3.5% chicken feather as carbon source, 1.0% tryptone as organic nitrogen source, 1.0% $KNO_3$ as inorganic nitrogen source and 0.05% KCl, 0.05% $KH_2PO_4$, 0.03% $K_2HPO_4$ as mineral source and 0.01% yeast extract as growth factor. The optimal temperature and pH was $40^{\circ}C$ and 8.5 with shaking culture (200 rpm), respectively. The maximum keratinase production reached to 123 units/ml after 42 hr of cultivation under the optimal condition. When the hair was used as the sole carbon source, the maximum enzyme activity was 88 units/ml after 120 hr and in this case, the hair added in the medium was not degraded completely but got thinner than the control by 20%.

• Mycobiology
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• 제39권2호
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• pp.103-108
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• 2011

Amylases and cellulases are important enzymes that can be utilized for various biological activities. Ten different wild Nigerian mushrooms (Agaricus blazei, Agaricus sp., Corilopsis occidentalis, Coriolus versicolor, Termitomyces clypeatus, Termitomyces globulus, Pleurotus tuber-regium, Podoscypha bolleana, Pogonomyces hydnoides, and Nothopanus hygrophanus) were assayed for production of these secondary metabolites. The results revealed that most of the tested wild fungi demonstrated very good amylase and cellulase activities. With the incorporation of carboxymethyl-cellulose (a carbon source) into the culture medium, Agaricus blazei had the highest amylolytic activity of 0.60 unit/mL (at $25^{\circ}C$, pH 6.8). This was followed in order by P. tuber-regium and Agaricus sp. with 0.42 and 0.39 unit/mL, respectively ($p {\leq} 0.05$). Maltose and sucrose supplementation into the submerged liquid medium made N. hygrophanus and P. hydnoides to exhibit very low amylase activities of 0.09 and 0.11 unit/mL, respectively. Introducing peptone (an organic nitrogen source) into the basal medium enhanced the ability of C. versicolor to produce a cellulase value of 0.74 unit/mL. Other organic nitrogen sources that supported good cellulase activities were yeast extract and urea. Sodium nitrate (inorganic nitrogen source) generally inhibited cellulase production in all mushrooms. The best carbon source was carboxymethyl-cellulose, which promoted very high cellulase activity of 0.67 unit/mL in C. versicolor, which was followed in order by P. tuber-regium, T. chypeatus, and C. occidentalis ($p {\leq} 0.05$). Sucrose was the poorest carbon compound, supporting the lowest values of 0.01, 0.01, and 0.14 unit/mL in P. hydnoides, A. blazei, and Agaricus sp., respectively.

• 한국미생물·생명공학회지
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• 제15권6호
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• pp.369-374
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• 1987

하상 오니 및 토양으로부터 D-$\alpha$-Amino-$\varepsilon$-Caprolactam(DAC)의 자화능이 우수한 균을 분리하여 Alcaligenes eutrophus로 동정하였다. Alcaligenes eutrophus A52의 생육을 위한 배양조건은 배양 초기 최적 pH가 6.0, 최적온도는 3$0^{\circ}C$, 최적 DAC 농도는 0.2%로서 50시간 배양으로 0.2% DAC를 거의 다 자화하여 정지기에 도달하였다. 본 균은 탄소원으로 glucose와 fructose, 질소원으로는 NH$_4$Cl, NH$_4$NO$_3$, (NH$_4$)$_2$SO$_4$ 및 NaNO$_3$를 잘 자화하였다. 탄소원 및 질소원으로 Iysine, glutamate를 잘 이용하였으나 그 밖의 아미노산 자화능은 낮았다. 균체로부터 추출한 3.1mg의 단백질에 상당하는 무세포 추출 액으로 0.5% DAC를 55%에서 12시간 반응시킨 생성물은 약 98% L-Iysine으로 확인되었다.

• KSBB Journal
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• 제25권6호
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• pp.553-558
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• 2010

Increasing demands on fossil fuel have led to the unprecedented attraction to microalgal biofuel as an alternative energy. In this study, we investigated growth and lipid productions of microalga Nannochloris oculata under various carbon dioxide or nitrogen source concentrations and irradiance conditions. Biomass production of N. oculata was highest under 2% $CO_2$ with 0.3 flow rate (vvm). In addition, biomass productivities were proportional to the concentration of nitrogen source, whereas lipid biosynthesis was suppressed under higher nitrogen concentration (up to 50 mg/L). High irradiation ($160{\sim}180\;{\mu}mol/m^2{\cdot}s$) enhanced growth rate and lipid production of N. oculata.