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3,4-Dihydroxyphenyl-L-alanine의 효소적 생산에 대한 반응첨가물의 영향
이승구,노현수,홍승표,성문희 한국미생물생명공학회 ( 구 한국산업미생물학회 ) 1996 한국미생물·생명공학회지 Vol.24 No.2
재조합 대장균에서 과발현된 Citrobacter freundii KCTC 2006 유래의 tyrosine phenol-lyase(E.C.4.1.99.2) 이용 3,4-dihydroxyphenyl-L-alanine (L-DOPA)의 생산에 대한 반응첨가물의 영향을 조사하였다. 반응액 중 효소 및 조효소 농도의 영향을 조사한 결과, 효소농도는 약 2 units/ml이 적합하였으며, 조효소인 pyridoxal -5-phosphate 는 0.1 mM 이상이 필요하였다. Pyrocatechol과 결합하여 안정한 복합체를 형성하는 sodium borate는 pyrocatechol에 의한 효소의 불활성화를 감소시키는 효과가 있었으나, 효소의 반응성을 현저히 저하시켜 L-DOPA 생산의 관점에서는 불리한 단점도 있었다. 한편, 알콜류 등의 유기용매가 L-DOPA 합성반응에 미치는 영향을 조사한 결과 methanol을 5% 농도로 반응액에 첨가하였을 때, 효소의 반응과 안정성이 크게 증가하여 L-DOPA 합성반응이 지속적으로 수행됨으로써 고농도의 L-DOPA를 효율적으로 생산할 수 있게 되었다. 생산된 L-DOPA의 약 77%가 불용성 상태로 침전되어 쉽게 회수할 수 있었으며, 침전된 L-DOPA를 1N HCI에 용해한 후 재결정화 함으로써 최종적으로 99.96%의 고순도 L-DOPA를 생산할 수 있었다. The enzymatic synthesis of 3,4-dihydroxyphenyl-L-alanine (L-DOPA) was examined for the effects of the reaction additives such as sodium borate, alcohol, and organic solvents. The enzyme used was tyrosine phenol-lyase of Citrobacter freundii KCTC 2006 produced in Escherichia coli. The amounts of tyrosine phenol-lyase and pyridoxal -5-phosphate were optimized to 2.0 units/ml and 0.1 mM, respectively, for the synthetic reaction. Sodium borate, a substance that forms a complex with pyrocatechol, reduced the enzyme deactivation by pyrocatechol although it seriously inhibited the enzyme activity. Among the organic solvents tested, dimethylsulfoxide, dimethylformamide, and alcohol increased the productivity of the L-DOPA synthesis. In a reaction system with 5% methanol, L-DOPA concentration increased up to 210 mM after 24 hours, and 77.1% of which was separated as precipitates. The L-DOPA was purified to 99.96%
제조합 대장균에서 과발현된 Citrobacter freundii KCTC2006 유래의 β-Tyrosinase를 이용한 3,4-Dihydroxyphenyl-L-alanine의 생산
이승구,노현수,홍승표,이규종,왕지원,태동년,엄기남,방상구,김영준,성문희 한국미생물생명공학회 ( 구 한국산업미생물학회 ) 1996 한국미생물·생명공학회지 Vol.24 No.1
재조합 대장균에서 대량발현 시킨 Citrobacter freundii KCTC 2006 유래이 효소 β-tyrosinase를 이용하여 pyrocatechol, sodium pyruvate, ammonium acetate로부터 3,4-dihydroxy phenyl-L-alanine을 생산하기 위한 연구를 수행하였다. 이 효소반응에 적합한 온도 및 pH 조건은 각각 18℃와 8.5로 결정되었고, 반응액 중의 ammonium acetate와 sodium pyruvate의 농도는 각각 300 mM, 50 mM 이상으로 조절하는 것이 적합하였다. Pyrocatechol의 경우는 20 mM에서 가장 높은 반응성을 나타냈으나, 기질을 반복적으로 첨가하며 장시간 동안 효소반응을 수행하는 경우에는 pyrocatechol의 고갈을 피하기 위하여, 20 mM에서 50 mM 사이로 조절하였다. 한편, 반응액 중에 ethanol을 10% 첨가한 경우에는 반응속도가약 20% 증가하였다. 이상과 같은 효소반응특성에 기초하여 조제한 기질용액에 β-tyrosinase를 1 unit/㎖ 농도로 가하고, pyrocatechol과 pyruvate가 고갈되지 않도록 간헐적으로 첨가하면서 효소반응을 수행한 결과, 24시간 만에 85.2%의 수율로 31.6g/ℓ의 3,4-dihydroxyphenyl-L-alanine를 생산할 수 있었다. By using the β-tyrosinase of Citrobacter freundii KCTC2006, which was cloned and overexpressed in Escherichia coli, 3,4-dihydroxy phenyl-L-alanine (L-DOPA) was synthesized efficiently from pyrocatechol, sodium pyruvate, and ammonium acetate. Optimal temperature and pH for the reaction were determined to be about 18℃ and 8.5, respectively. The effects of substrate concentrations were also examined at different concentrations of ammonium acetate, sodium pyruvate, and pyrocatechol. Ammonium acetate and sodium pyruvate increased the reaction rate until the concentrations reached to 300 mM and 50 mM, respectively. Although pyrocatechol showed the optimal concentration at 20 mM, it was controlled between 20 mM and 50 mM to avoid the depletion of substrate during the enzymatic synthesis. Based on above results, a reaction medium for the production of L-DOPA was prepared and incubated with 1 unit/㎖ of β-tyrosinase. Pyrocatechol and sodium pyruvate was added to the reaction solution intermittently to avoid the substrate depletion during the enzymatic reaction. After 24 hour of reaction, 31.6 g/ℓ L-DOPA was accumulated in the reaction solution as soluble and precipitated ones and the conversion yield was about 85.2%.
Inactivation of Foot-and-Mouth Disease Virus by Citric Acid and Sodium Carbonate with Deicers
Hong, Jang-Kwan,Lee, Kwang-Nyeong,You, Su-Hwa,Kim, Su-Mi,Tark, Dongseob,Lee, Hyang-Sim,Ko, Young-Joon,Seo, Min-Goo,Park, Jong-Hyeon,Kim, Byounghan American Society for Microbiology 2015 Applied and environmental microbiology Vol.81 No.21
<P>Three out of five outbreaks of foot-and-mouth disease (FMD) since 2010 in the Republic of Korea have occurred in the winter. At the freezing temperatures, it was impossible to spray disinfectant on the surfaces of vehicles, roads, and farm premises because the disinfectant would be frozen shortly after discharge and the surfaces of the roads or machines would become slippery in cold weather. In this study, we added chemical deicers (ethylene glycol, propylene glycol, sodium chloride, calcium chloride, ethyl alcohol, and commercial windshield washer fluid) to keep disinfectants (0.2% citric acid and 4% sodium carbonate) from freezing, and we tested their virucidal efficacies under simulated cold temperatures in a tube. The 0.2% citric acid could reduce the virus titer 4 logs at −20°C with all the deicers. On the other hand, 4% sodium carbonate showed little virucidal activity at −20°C within 30 min, although it resisted being frozen with the function of the deicers. In conclusion, for the winter season, we may recommend the use of citric acid (>0.2%) diluted in 30% ethyl alcohol or 25% sodium chloride solvent, depending on its purpose.</P>
다공 동축 버너를 이용한 순산소 연소 시스템에 관한 연구
김현준(Hyeon Jun Kim),최원영(Wonyoung Choi),배수호(Soo Ho Bae),홍정구(Jung Goo Hong),신현동(Hyun Dong Shin) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.7
The characteristics of nonpremixed oxy-fuel flame in a multi-jet burner were experimentally and numerically investigated. The overall flow rate of fuel and oxygen was fixed, and the oxygen feeding ratio (OFR) was varied by 0.25, 0.5, and 0.75. The results of numerical simulation were compared with the measured results which are temperature profile and direct flame observation. The probability density function (PDF) model was applied accounting to the description between turbulence and chemistry, and standard k-ε model was used for turbulent flow field. Equilibrium assumption is very reasonable due to fast chemistry of the oxy-fuel combustion. Thus, the equilibrium calculation based on Gibbs free energy minimization was guaranteed to generate the solution of the oxy-fuel combustion. The result was obtained by numerical simulation. The predicted radial temperature profiles were in good agreement with the measured results. The flame length was shorten and was intensified with the decrease of OFR because the mixture of fuel and oxidizer are fast mixed and burnt. The maximum temperature became lower as the OFR increased, as a consequence of large flame surface area.
둔체를 갖는 연소기에서 자려 연소 진동에 관한 수치해석
김현준(Hyeon Jun Kim),홍정구(Jung Goo Hong),김대희(Dae Hee Kim),신현동(Hyun Dong Shin) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.9
Combustion instability has been considered as very important issue for developing gas turbine and rocket engine. There is a need for fundamental understanding of combustion instability. In this study, combustion instability was numerically and experimentally investigated in a dump combustor with bluff body. The fuel and air mixture had overall equivalence ratio of 0.9 and was injected toward dump combustor. The pressure oscillation with approximately 256㎐ was experimentally obtained. For numerical simulation, the standard k-ε model was used for turbulence and the hybrid combustion model (eddy dissipation model and kinetically controlled model) was applied. After calculating steady solution, unsteady calculation was performed with forcing small perturbation on initial that solution. Pressure amplitude and frequency measured by pressure sensor is nearly the same as those predicted by numerical simulation. Furthermore, it is clear that a combustion instability involving vortex shedding is affected by acoustic-vortex-combustion interaction. The phase difference between the pressure and velocity is π/2, and that between the pressure and heat release rate is in excitation range described by Rayleigh, which is obvious that combustion instability for the bluff body combustor meets thermoacoustic instability criterion.
연소실내의 압력 변동에 따른 연료 분사구에서의 당량비 변동에 관한 수치해석
김현준(Hyeon Jun Kim),홍정구(Jung Goo Hong),신현동(Hyun Dong Shin) 한국연소학회 2006 KOSCOSYMPOSIUM논문집 Vol.- No.-
It has been observed in experiments that combustion instability of low frequency (~10㎐) results form the modulation of equivalence ratio at fuel injection hole when a pressure fluctuation propagates upwards along the channel of the burner under an unchoked fuel flow condition. In this study, a commercial program was used to determine how the fuel flow rate changed with respect to the pressure, velocity of the fuel flow and the mass fraction in a choked and an unchoked condition. The calculation focus on the upstream of the dump plane to know how the forced pressure with the fuel injection conditions affects the modulation of the equivalence ratio. Therefore, it is found that pressure fluctuation leads to oscillation of mass flow rate and then results in equivalence ratio modulation under the unchoked fuel flow condition.
Jae-Hong Min,Seong-Man Kim,Soo Hyeon Goo,Jae-Hoon Oh,Seung-Ho Kim,Ji-Won Park,Ok-Kyoung Kwon,Jae-Won Lee,Sang-Bae Han,Kyung-Seop Ahn 한국실험동물학회 2021 한국실험동물학회 학술발표대회 논문집 Vol.2021 No.7
Lagerstroemia ovalifolia (LO) has been shown to have anti-inflammatory effects in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. I investigated whether the anti-inflammatory effect of LO in LPS-induced acute lung injury (ALI) in a mouse model. LO reduced the number of neutrophils and macrophages in the bronchoalveolar lavage fluid (BALF) of the LPS-induced ALI in a mouse model. LO decreased the pro-inflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in the BALF of the LPS-induced ALI in a mouse model. LO decreased the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and monocyte chemoattractant protein-1 (MCP-1) in the lung tissue of the LPS-induced ALI in a mouse model and regulated the activities of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPKs) in the lung tissue of the LPS-induced ALI in a mouse model. Therefore, LO has an anti-inflammatory effect of LPS-induced ALI in a mouse model.