h형 액막화 공기 공급장치를 이용한 산소의 물질전달 특성 연구

조용현 ( Yong-hyun Cho ),김연은 ( Yun-eun Kim ),김희영 ( Hee-young Kim ) 한국수처리학회 2017 한국수처리학회지 Vol.25 No.4

In this study, the aeration system using the principle of airlift pump, which is one of the element technologies for the artificial aeration, was researched as part of the measures to prevent the eutrophication in the lentic zone and the oxygen depletion in the bottom water. The mass transfer characteristics of the oxygen such as oxygen transfer variation, changes in DO concentration, dissolution, overall oxygen mass transfer coefficient(K_La), oxygen dissolution efficiency(E_A), etc. were evaluated through the h-type liquid-film air supply unit, which has oxygen dissolution and water circulation functions and the oxygen supply function by the liquid film. In the results of water circulation experiment with the deoxygenated water of having DO of 0.5 mg/L or less at air supply of 17 L/min, 20 L/min, 23 L/min and 26 L/min, it was judged that operating at 23 L/min was appropriate. The DO concentration by air supply at 14℃ and 17℃ of the water temperature was measured and the performance of the aeration system was evaluated by calculating KLa and EA considering the air flow rate, water temperature and reactor size out of the various factors having impact on the oxygen transfer. In the results of calculating K_La(20), the more the air supply was increased by 23 L/min, the more the value was increased but at 27 L/min, it showed the tendency that it was increased slightly or decreased. In the results of calculating E_A, which is the basic index of aeration efficiency, the more the air supply was increased, the pure oxygen dissolution efficiency was decreased. Therefore, it was observed that in the aspect of water circulation, it did not require the air supply more than necessary. In addition, in the aspect of oxygen supply, the more the air supply was increased, the more the aeration efficiency of the system was decreased, which is deemed that the formation of liquid-film was inhibited.

Development of Oxygen Transfer Rate (OTR) Prediction Model in CHO Cell Shake Flask Cultures

hanchul KO,Jong Youn BAIK 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.4

Shake flasks are widely used as small-scale mammalian culture vessels during cell line development and bioprocess optimization for the production of biopharmaceuticals. However, the lack of information about culture parameters in shake flasks, such as pH and dissolved oxygen, often leads to oxygen limitation that can adversely affect cell growth and productivity during cell culture, thereby challenging cell line development and scale-up processes. In this work, we report an oxygen transfer rate(OTR) prediction model of shake flasks using Chinese hamster ovary(CHO) cells to reduce oxygen limitation in shake flasks. First, we varied shaking speed and culture volume to measure maximum OTR(OTR_max) and created an OTR_max regression function. Then, we estimated theoretical maximum oxygen-supplied cell density with the known oxygen uptake rates of CHO cells and the OTR_max values. Lastly, we tested if decreasing culture volume or increasing shaking speed could mitigate the adverse effect of oxygen limitation. In conclusion, we believe this OTR prediction model will provide information about the oxygen availability in shake flasks, presumably assisting to achieve better culture performances.

Combustion and Radiation Characteristics of Oxygen-Enhanced Inverse Diffusion Flame

Hwang, Sang-Soon,Gore, Jay-P The Korean Society of Mechanical Engineers 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.9

The characteristics of combustion and radiation heat transfer of an oxygen-enhanced diffusion flame was experimentally analyzed. An infrared radiation heat flux gauge was used to measure the thermal radiation of various types of flames with fuel, air and pure oxygen. And the Laser Induced Incandescence (LII) technique was applied to characterize the soot concentrations which mainly contribute to the continuum radiation from flame. The results show that an oxygen-enhanced inverse diffusion flame is very effective in increasing the thermal radiation compared to normal oxygen diffusion flame. This seems to be caused by overlapped heat release rate of double flame sheets formed in inverse flame and generation of higher intermediate soot in fuel rich zone of oxygen-fuel interface, which is desirable to increase continuum radiation. And the oxygen/methane reaction at slight fuel rich condition (ø=2) in oxygen-enhanced inverse flame was found to be more effective to generate the soot with moderate oxygen availability.

실리콘 튜브를 이용한 동물세포 배양장치의 산소전달

정흥채,김정회 한국산업미생물학회 1992 한국미생물·생명공학회지 Vol.20 No.4

동물세포 배양기에서 silicone tube를 oxygenator로 이용하여 산소전달 정도를 조사하였다. Silicone tube를 이용할 때 표면통기에 비해 산소전달 상수 k_La는 약 30배 이상 증가하였다. 통기속도와 교반속도가 증가할수록 k_La값도 증가하지만 교반속도가 휠씬 효과적이었고, 물질전달에 관한 무차원 상수 tubing Sherwood number(Sh)와 유체 흐름에 관한 상수 impeller Reynolds number(Re)는 log-log 좌표에서 직선관계가 있었고 기울기는 tube 길이에 관계없이 0.26이었다. Tube 길이는 2m가 적당하였고 impeller는 pitched blade type이 효과적이었다. 5% serum이 첨가된 medium에서는 k_La가 40%로 감소하였다. HepG2를 이용한 실제 동물세포 배양에서는 전형적인 세포농도인 4∼6×10^6 cells/㎖를 얻을 수 있었다. An enhancement of the oxygen transfer rate in a 1ℓ bioreactor for mammalian cell culture by using a silicone rubber tubing as an oxygenator was investigated. When the silicone membrane was used to supply oxygen to the culture broth, the oxygen transfer coefficients (k_La) measured in deionized-distilled water were markedly increased. Effect of surface aeration without the tubing aeration was very low under 1.0 hr^-1 of k_La. The enhancing effects of agitation rates on k_La were much more effective than those of aeration rates. The increase of k_La with increasing tube length was observed as a result of the large surface area for oxygen supply. However, 2m of the tube length was adequate for a 1ℓ vessel. The larger blade type of impeller was effective to enhance the k_La values because of its high mixing intensity. In culture medium supplemented with 5% serum, k_La values were reduced to approximately 40% probably due to the viscosity. We also obtained the normal cell concentration of 5×10^6 cells/㎖ of HepG2 on microcarriers, which could be achieved in a typical bioreactor for animal cell culture.

A Study on Radiation Heat Transfer and Characteristics of Oxygen Enriched Double Inversed Diffusion Flame

Lee, Sung-Ho,Hwang, Sang-Soon The Korean Society of Combustion 2001 한국연소학회지 Vol.6 No.2

An experimental study of oxygen enriched double inversed diffusion flame was conducted to understand the flame characteristics and radiation heat transfer. The infrared radiation meter was used to measure of various combination of fuel, air and pure oxygen. The results show that oxygen enriched double inversed diffusion flame is very effective to increase of thermal radiation and proper addition of pure oxygen in air flow can intensify thermal radiation of flame. And it can be found that oxygen enriched double inversed diffusion flame could give benefits of cost effective and very high energy.

CFD 를 이용한 Bioreactor 의 점도 변화에 따른 oxygen mass transfer 추정

박영석,이종민 제어로봇시스템학회 2021 제어로봇시스템학회 국내학술대회 논문집 Vol.2021 No.6

In a bioreactor, dissolved oxygen (DO) is an index that influences cell productivity severely because it is directly related to cell death. In addition, as the process proceeds, the properties of the continuous phase (liquid) such as viscosity change greatly, and the accuracy of the existing estimation is greatly degraded. Therefore, in order to optimally control the bioreactor, a model that can reflect the gas-liquid mass transfer in a continuous phase of various properties must be used. In this study, the oxygen mass transfer coefficient is estimated using a CFD (Computational fluid dynamics) technique to estimate the DO distribution of a bioreactor at 3 different viscosities. Population balance model was used to reflect accurate local bubble distribution, and Higbie's penetration and Eddy cell model were used to estimate bubble to liquid mass transfer. The CFD model showed good agreement with the measured value of the local bubble distribution. In the case study, as the viscosity increased, the area with the extreme low mass transfer coefficient decreased since the gas hold-up increased, but the time it takes to reach equilibrium state increase by more than 5 times more..

Dimensionality-dependent oxygen reduction activity on doped graphene: Is graphene a promising substrate for electrocatalysis?

Chung, Min Wook,Choi, Chang Hyuck,Lee, Seung Yong,Woo, Seong Ihl Elsevier 2015 Nano energy Vol.11 No.-

<P><B>Abstract</B></P> <P>Graphene, a two-dimensional layer framework of <I>sp</I> <SUP>2</SUP>-hybridized carbon, has attracted tremendous attentions as a promising material for oxygen reduction reactions (ORRs) due to its ideal uniqueness of high surface area and electrical conductivity. Contrary to the general belief, however, graphene catalysts have shown poor catalytic activities compared with those of other carbon-based catalysts. Herein, to understand the low ORR kinetics on the graphene catalysts, the dimensionality of graphene catalysts is sequentially tuned from sheets (2D) to ribbons (1D) and to dots (0D), and then the accompanying changes in terms of physical and electrochemical properties are investigated. In ultraviolet photoelectron spectroscopy, an increment in electropotential is measured as the dimensionality of the graphene catalysts decreases, of which the result infers the enhanced kinetics of the electron transfer from the graphene catalysts to O<SUB>2</SUB> (electropotential: 0D>1D>2D). However, ORR performance does not follow the order of electropotential, and the graphene ribbons show the best activity among the prepared graphene catalysts (ORR activity: 1D>0D>2D). Further electrochemical impedance spectroscopy studies demonstrate that ORR kinetics is primarily determined by charge transfer rates in the fabricated graphene electrodes, which are strongly related to the electrode configurations and thus also to the length-to-width ratios of the graphene catalysts. The graphene sheets and dots, of which the length-to-width ratios are almost 1, handily lay over each other, leading to an impedance of efficient charge transfers. This study suggests the importance of void channels in the fabricated graphene electrode, which have not previously been considered significantly as a factor for improving ORR activity on the graphene catalysts.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The dimensionality of graphene catalysts is sequentially tuned from sheets (2D) to ribbons (1D) and to dots (0D), and then the accompanying changes in terms of physical and electrochemical properties are investigated. </LI> <LI> The prepared graphene catalysts, having N-doped sites as active sites, revealed an increment of electropotential as the dimensionality decreased, but the catalytic activity did not perfectly follow the tendency. </LI> <LI> Electrochemical impedance spectroscopy studies demonstrate that ORR kinetics is primarily determined by charge transfer rates in the fabricated graphene electrodes. </LI> <LI> To achieve a superior ORR performance, the structural constitute for efficient charge accessibility as well increased <I>E</I> <SUB>P</SUB> may be preferentially considered in future design of graphene catalysts. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Shape effect on optimal geometric conditions in surface aeration systems

Bimlesh Kumar,Ajey Kumar Patel,Achanta Ramakrishna Rao 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.1

The performance of surface aeration systems, among other key design variables, depends upon the geometric parameters of the aeration tank. Efficient performance and scale up or scale down of the experimental results of an aeration system requires optimal geometric conditions. Optimal conditions refer to the conditions of maximum oxygen transfer rate, which assists in scaling up or down the system for commercial utilization. The present work investigates the effect of an aeration tank's shape (unbaffled circular, baffled circular and unbaffled square) on oxygen transfer. Present results demonstrate that there is no effect of shape on the optimal geometric conditions for rotor position and rotor dimensions. This experimentation shows that circular tanks (baffled or unbaffled) do not have optimal geometric conditions for liquid transfer, whereas the square cross-section tank shows a unique geometric shape to optimize oxygen transfer.

Photochemical Property and Photodynamic Activity of Tetrakis(2-naphthyl) Porphyrin Phosphorus(V) Complex

Hirakawa, Kazutaka,Aoki, Shunsuke,Ueda, Hiroyuki,Ouyang, Dongyan,Okazaki, Shigetoshi Korean Society of Photoscience 2015 Rapid communication in photoscience Vol.4 No.2

To examine the photosensitized biomolecules damaging activity, dimethoxyP(V)tetrakis(2-naphthyl)porphyrin (NP) and dimethoxyP(V)tetraphenylporphyrin (PP) were synthesized. The naphthyl moiety of NP hardly deactivated the photoexcited P(V)porphyrin ring in ethanol. In aqueous solution, the naphthyl moiety showed the quenching effect on the photoexcited porphyrin ring, possibly through electron transfer and self-quenching by a molecular association. Binding interaction between human serum albumin (HSA), a water soluble protein, and these porphyrins could be confirmed by the absorption spectral change. The apparent association constant of NP was larger than that of PP. It is explained by that more hydrophobic NP can easily bind into the hydrophobic pockets of HSA. The photoexcited PP effectively induced damage of the tryptophan residue of HSA, through electron transfer-mediated oxidation and singlet oxygen generation. NP also induced HSA damage during photo-irradiation and the contributions of the electron transfer and singlet oxygen mechanisms were speculated. The electron transfer-mediated mechanism to the photosensitized protein damage should be advantageous for photodynamic therapy in hypoxic condition. The quantum yield of the HSA photodamage by PP was significantly larger than that of NP. The quenching effect of the naphthyl moiety is considered to suppress the photosensitized protein damage. In conclusion, the naphthalene substitution to the P(V)porphyrins can enhance the binding interaction with hydrophobic biomacromolecules such as protein, however, this substitution may reduce the photodynamic effect of P(V)porphyrin ring in aqueous media.

Determination of nanomolar levels of reactive oxygen species in microorganisms and aquatic environments using a single nanoparticle-based optical sensor

Kim, Yura,Kim, Youngho,Choi, Jinhee,Kang, Taewook,Choi, Inhee Elsevier 2017 Analytica chimica acta Vol.967 No.-

<P><B>Abstract</B></P> <P>Reactive oxygen species (ROS) are strong oxidants, and have attracted considerable attention in both biological and environmental fields. Although various methods for ROS detection, including optical and electrochemical techniques, have been developed, they still face challenging issues in terms of poor sensitivity, reproducibility, stability, and <I>in vivo</I> applicability. Here, we present a sensitive and selective optical sensor for ROS detection, based on single plasmonic nanoprobes and redox-active cytochrome <I>c</I> (Cyt <I>c</I>)-mediated plasmon resonance energy transfer. By measuring the spectral changes of plasmonic nanoprobes, derived from the unique molecular absorption of Cyt <I>c</I> in accordance with the redox state, calibration curves for H<SUB>2</SUB>O<SUB>2</SUB>, a representative ROS, in various media were obtained over a wide concentration range from 100 mM to 1 nM. Limit of detection and limit of quantification in accordance with the used medium were determined from 8.3 to 12.8 nM and from 27.6 to 42.7 nM, respectively. Selectivity coefficients for major interfering solutes were much lower than 0.1 indicating a good selectivity for ROS. From the dynamic spectral changes, we sensitively monitored ROS generated in <I>Caenorhabditis elegans</I> (<I>C. elegans</I>) exposed to graphene oxide. Based on the calibration curves, we also determined ROS levels in various aquatic environments, such as river streams and a small pond, as a way of environmental monitoring. We believe that our approach could provide an avenue for achieving dynamic and sensitive monitoring of ROS in toxicological, biological, and environmental fields in the future.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Single nanoparticle-based optical sensor for monitoring reactive oxygen species (ROS). </LI> <LI> More sensitive monitoring and wider detection range than commercially available method. </LI> <LI> Limit of detection and quantification were determined from 8.3 to 12.8 nM and from 27.6 to 42.7 nM, respectively. </LI> <LI> Selectivity coefficients for major interfering solutes were much lower than 0.1. </LI> <LI> Determination of nanomolar level ROS in biological and environmental samples. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>