• 공업화학
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• 제2권3호
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• pp.209-215
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• 1991

n-헥산과 40 wt % p-TSA 수용액으로 이루어진 비혼화성 액상계에서 교반에 의한 유기상의 분산을 해석하였다. 사용된 교반기는 blade의 형태가 flat와 금망으로 된 4가지 형태의 6-bladed turbine 교반기를 사용하였다. 실험결과, 동일한 교반속도에서 유기상의 분산정도는 blade의 형태가 flat, 60 mesh, 40 mesh, 20 mesh의 순서로 감소하였고 계면활성제인 TBA의 농도가 증가할수록, 그리고 유기상의 부피비가 작을수록 유기상은 잘 분산되었다. 또한 완전분산에 필요한 최소교반속도는 flat, 60 mesh, 40 mesh, 20 mesh의 순서로 증가하였으나 최소소요동력은 거의 동일하였다. 이때 Power number와 Reynolds number와의 관계는 $N_p=a\;N_{Re}{^b}$ 이었으며 교반기의 형태에 따른 상수 a와 혼합계의 종류에 따른 상수 b의 값은 각각 2200~4100, -0.69~-0.63 범위이었다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제20권6호
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• pp.103-110
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• 2015

Nitro-aromatic Compounds (NACs) of explosives are structurally non-degradable materials that have an adverse effect to humans and ecosystems in case of emissions in natural due to the strong toxicity. In this study, batch test in the laboratory-scale has been conducted to find some process parameters of alkaline hydrolysis by considering the characteristics of NACs which are unstable in a base status and field application evaluation have been performed on the batch test results. Based on the experimental results of both laboratory and pilot-scale test, the optimum conditions of parameters for the alkaline hydrolysis of soils contaminated with explosives were pH 12.5, above the solid-liquid ratio 1 : 3, above the room temperature and 30 minute reaction time. In these four process parameters, the most important influencing factor was pH, and the condition of above pH 12.0 was necessary for high contaminated soils (more than 60 mg/kg). In the case of above pH 12.5, the efficiency of alkaline hydrolysis was very high regardless of the concentrations of contaminated soils. At pH 11.5, the removal efficiency of TNT was increased from 76.5% to 97.5% when the temperature in reactor was elevated from room temperature to 80℃. This result shows that it is possible to operate the alkaline hydrolysis at even pH 11.5 due to increased reaction rate depending on temperature adjustment. The results found in above experiments will be able to be used in alkaline hydrolysis for process improvement considering the economy.

• Journal of Microbiology and Biotechnology
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• 제24권6호
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• pp.781-787
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• 2014

2-Ketogluconic acid production by Klebsiella pneumoniae is a pH-dependent process, strictly proceeding under acidic conditions. Unfortunately, cell growth is inhibited by acidic conditions, resulting in low productivity of 2-ketogluconic acid. To overcome this deficiency, a two-stage fermentation strategy was exploited in the current study. During the first stage, the culture was maintained at neutral pH, favoring cell growth. During the second stage, the culture pH was switched to acidic conditions favoring 2-ketogluconic acid accumulation. Culture parameters, including switching time, dissolved oxygen levels, pH, and temperature were optimized for the fed-batch fermentation. Characteristics of glucose dehydrogenase and gluconate dehydrogenase were revealed in vitro, and the optimal pHs of the two enzymes coincided with the optimum culture pH. Under optimum conditions, a total of 186 g/l 2-ketogluconic acid was produced at 26 h, and the conversion ratio was 0.98 mol/mol. This fermentation strategy has successfully overcome the mismatch between optimum parameters required for cell growth and 2-ketogluconic acid accumulation, and this result has the highest productivity and conversion ratio of 2-ketogluconic and produced by microorganism.

• 공업화학
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• 제34권1호
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• pp.57-63
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• 2023

본 연구에서는 Abaca 나노 셀룰로오스와 이산화 티타늄(TiO₂)의 유-무기 하이브리드 복합체를 제조하였다. Abaca 나노 셀룰로오스는 Abaca 셀룰로오스를 산화시키는 방법으로 제조하였으며, 촉매로서 TEMPO (2,2,6,6-tetramethyl-piperidine-1-oxyl)를 이용하였다. TiO₂ 나노입자는 sol-gel법으로 제조하였으며 이를 나노 셀룰로오스와 하이브리드(hybrid) 시켜 복합체를 제조하였다. 제조 pH 변화에 따른 복합체의 특성과 그의 물성을 비교해 본 결과, 나노 셀룰로오스와 이산화 티타늄 결합 시 pH의 영향이 매우 컸으며, 본 실험 조건에서 pH 8에서 최적의 결합성능을 나타냈다. 또한, 제조된 복합체는 광촉매 특성을 보였으며, 이산화 티타늄의 함량이 높을수록 UV광 조사에 따라 복합체의 친수성이 증가하였다.

• 센서학회지
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• 제26권6호
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• pp.414-419
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• 2017

The optical characteristics of cresol red, phenol red, and neutral red immobilized in the thin film were investigated with absorbance measurement in order to find a sensing part of a fiber-optic pH sensor. Sol-Gel method with tetramethyl orthosilicate as a precursor was used to immobilize the pH indicators in the thin film. The absorbance spectra were measured when pH indicators were immobilized in the film and were dissolved in the buffer solution. Experimental results showed that the absorbance spectra could be changed when the pH indicator is immobilized in the thin film. As compared with other pH indicators, the neutral red exhibited similar absorbance spectra regardless of physical conditions and was sensitive over whole pH range between 4 and 11. In addition, the absorbance ratio of base peak to acid peak tended to increase in proportion to the increase in pH. Experimental results indicate that the neutral red is a good pH indicator for fabrication of a sensing part of the fiber-optic pH sensor.

• 공업화학
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• 제8권5호
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• pp.830-836
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• 1997

본 실험에서는 물유리를 사용하여 산세척에 의하여 제조된 산화철 입자의 표면개질에 대하여 연구하였다. 사용한 물유리의 $SiO_2$와 $Na_2O$의 몰비($SiO_2/Na_2O$)는 1, 2, 3.5이였다. 첨가되는 실리카의 양과 pH에 따라 산화철 현탁액의 분산성을 입자의 표면하전과 침강속도에 의하여 평가하였다. 그리고, 중성 영역에서 산화철 입자의 분산안정성을 유지할 수 있는 표면개질제(실리카)의 양을 도출하였으며, 물유리에 의한 산화철 입자의 표면개질을 습식 볼밀링에 의하여 슬러리 상태에서 실시하였다. 그 결과, 표면처리한 산화철 현탁액의 분산 안정성은 실리카의 양과 pH에 상호 의존하였다. 미처리한 산화철은 등전점인 pH 8에서 분산안정성을 잃고 있었으나, 산화철에 대하여 약 0.8wt%의 실리카로 표면처리한 산화철은 pH 5 이상 중성영역에서 분산안정성을 나타내었으며, 음이온성 계면활성제를 0.2wt% 이상 첨가에 의한 분산안정성이 더욱 증가되었다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제5권3호
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• pp.153-158
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• 2000

Vancomycin belongs to the vancomycin-risocetin family of glycopeptides, and is a subclass of linear sugar containg peptides composed of seven amino acids. Its strochemical configuration forms the basic of a peptidoglycon monomer. The glycosylated hexapeptide chainconsists of chloro-$\beta$-hydroxytyrosines, p-hytidoglycines, N-anthylleucine and aspartic acid forms a rigid molecular frame work and gives the difficulty in the analysis. Voncomycin in the serum samples is usually estimated by liquid chromatography and the bacterial sensitivity was genereally tested by the microbiological assay. The pressent review deals with the qualitative, quantutative, microbioligical and immunological assays and the comparison of the quantitative methods. Clinical implications of vancomycin have also been cited in the review.

• Journal of Microbiology and Biotechnology
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• 제11권4호
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• pp.649-655
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• 2001

The kinetics of the thermolysin-catalyzed synthesis of N-(benzyloxycarbonyl)-L-phenylalanyl-L-leucine ethyl ester (Z-Phe-LeuOEt) from N-(benzyloxycarbonyl)-L-phyenylalanine (Z-Phe) and L-leucine ethyl ester (LeuOEt) in an ethyl acetate saturated aqueous system in a batch operation were studied. The kinetics for the synthesis of Z-Phe-LeuOEt were expressed using a rate equation for the rapid equilibrium random bireactant mechanism. The four kinetic constants involved in the rate equation were determined numerically by the quasi-Newton method so as to fit the calculated results with the experimental data. Within the pH and temperature range examined, the $K_{cat}$ value for the synthesis of Z-Phe-LeuOEt reached a maximum at pH 7.0 and $45^{\circ}C$, whereas the affinity between Z-Phe and thermolysin reached a maximum at pH 6.0 adn $40^{\circ}C$. The inhibitory effect of Z-Phe on the condensation reaction decreased as the pH and temperature decreased. In contrast, they affinity between LeuOEt and thermolysin remained unchanged within the pH and temperature range examined. Therefore, it was concluded that the protonation state of the carboxyl groups. of Z-Phe was more imprtant than that of the amono groups of LeuOEt for the synthesis of Z-Phe-LeuOEt in the present solvent system. The equilibrium yield at pH 6.0 and $30^{\circ}C$ was 8% higher than that at pH 7.0 and $40^{\circ}C$, although the rate was much slower. This result suggested that the affinity between the enzyme and the substrate rather than the overall rate was a more important factor affecting the equilibrium yield, when the peptide synthesis was carried out in a product-precipitation system.

• 대한수의학회지
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• 제46권2호
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• pp.127-133
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• 2006

Pasteurella multocida is a terrible veterinary pathogen that causes widespread infections in husbandry. To induce homologous and/or heterologous immunity against the infections, outer membrane protein Hs (OmpH) in the envelope of different strains of P. multocida are thought to be attractive vaccine candidates. Previously we cloned and characterized a gene for OmpH from pathogenic P. multocida (A : 3) (In Press, Korean J. Microbiol. Biotechnol. 2005, 33, December). The gene is composed of 1,047 nucleotides (nt) coding 348 amino acids (aa) with signal peptide of 20 aa. The truncated ompH, a gene without nt coding for the signal peptide, was generated using pRSET A to name "pRSET A/OmpH-F2". This truncated ompH was well expressed in Escherichia coli BL21 (DE3). Truncated OmpH was purified for induction of immunity against live pathogen of fowl cholera (P. multocida A : 3) in mice. Some $50{\mu}g$ of the purified polypeptide was intraperitoneally injected into mice two times with 10 day interval. Lethal dose ($25{\mu}l$) of live P. multocida A : 3 was determined by directly injecting the pathogen into wild mice (n = 25). To demonstrate the vaccine candidate of the truncated OmpH, the live pathogen ($25{\mu}l$) was challenged with the OmpH-immunized mouse group as well as positive & negative controls (n = 80). The results show that the truncated OmpH can be used for an effective vaccine production to prevent fowl cholera caused by pathogenic P. multocida (A : 3).

• 대한화학회지
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• 제46권5호
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• pp.432-449
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• 2002

본 논문에서는 산화 환원 효소의 최적 pH를 예측해 보았다. Boltzman 분배를 이용하여 어떤 아미노산의 side chain이 물에서 발견될수 있는 상대적 확률이나 물에 대한 상대적 친화력을 구하였으며 p$K_R$을 이용해 protonated 아미노산의 양과 deprotonated 아미소산의 양을 계산하였다. 효소의 최적 pH는 아미노산의 side chain이 물에서 발견될수 있는 상대적 확률과 protonated 또는 deprotonated된 아미노산 양의 곱인 유효 protonated된 양과 유효 depotonated된 양이 같아지는 pH로 예측하였다. 문헌 값과 비교해 보았을 때 예측치는 상당히 일치하는 경향을 보였으며 이 결과 로 효소 자체의 전도도가 생물학적 기능에 있어 매우 중요한 역할을 하는 것을 알 수있다.