Mi-Sun Kim

Korea Institute of Energy Research, Sŏul, Seoul, South Korea

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Publications (48)111.09 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In the present work, lactic acid (LA) production performance with granulation was investigated at various hydraulic retention times (HRTs), 8-0.5h. Glucose was used as a feedstock, and anaerobic mixed cultures were inoculated in an up-flow anaerobic sludge blanket reactor. As HRT decreased, the average diameter and hydrophobicity of the granules increased from 0.31 to 3.4mm and from 17.5% to 38.3%, respectively, suggesting the successful formation of granules. With decreasing HRT, LA productivity increased up to 16.7gLA/L-fermenter/h at HRT 0.5h. The existence of rod-shaped organisms with pores and internal channels at granule surface was observed by scanning electron microscope. Next generation sequencing revealed that Lactobacillus was the dominant microorganism, accounting for 96.7% of total sequences, comprising LA-producing granules.
    Bioresource Technology 03/2014; · 4.75 Impact Factor
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    ABSTRACT: The release of silver (Ag) nanoparticles (NPs) into sewage streams has heightened concerns about potential adverse impacts on wastewater treatment processes. Here, we show that the rate constants of both biological nitrification and organic oxidation decreased exponentially with an increase in the Ag NP concentration, but nitrification was more severely inhibited than the organic oxidation even at low Ag NP concentrations (<1 mg Ag L(-1)) in batch experiments. The long-term exposure effects of Ag NPs on activated sludge bacteria were evaluated in sequencing batch reactors (SBRs) fed with two different substrates favoring heterotrophic and autotrophic bacteria. From a continuous operation for 50 days, it was found that heterotrophic bacteria in the organic removal process have higher tolerance to Ag NPs than do nitrifying bacteria. The effects of Ag NPs on the microbial community in both SBRs were analyzed using 16S ribosomal ribonucleic acid (rRNA) gene sequences obtained from pyrosequencing. The results showed that the level of microbial susceptibility is different for each type of microorganism and that the microbial diversity decreased dramatically after continuous exposure to Ag NPs for 50 days, resulting in a decrease of wastewater treatment efficiency.
    Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering 01/2014; 49(6):685-93.
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    ABSTRACT: Biological fermentation routes can provide an environmentally friendly way of producing H2 since they use renewable biomass as feedstock and proceed under ambient temperature and pressure. In particular, photo-fermentation has superior properties in terms of achieving high H2 yield through complete degradation of substrates. However, long-term H2 production data with stable performance is limited, and this data is essential for practical applications. In the present work, continuous photo-fermentative H2 production from lactate was attempted using the purple non-sulfur bacterium, Rhodobacter sphaeroides KD131. As a gradual drop in H2 production was observed, we attempted to add ethanol (0.2% v/v) to the medium.
    Biotechnology for Biofuels 01/2014; 7:79. · 5.55 Impact Factor
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    ABSTRACT: In the present work, we introduced a novel approach for microbial fatty acids (FA) production. Photosynthetic bacteria, Rhodobacter sphaeroides KD131, were cultivated in a continuous-flow, stirred-tank reactor (CFSTR) at various substrate (lactate) concentrations. At hydraulic retention time (HRT) 4d, cell concentration continuously increased from 0.97g dcw/L to 2.05g dcw/L as lactate concentration increased from 30mM to 60mM. At 70mM, however, cell concentration fluctuated with incomplete substrate degradation. By installing a membrane unit to CFSTR, a stable performance was observed under much higher substrate loading (lactate 100mM and HRT 1.5d). A maximum cell concentration of 16.2g dcw/L, cell productivity of 1.9g dcw/L/d, and FA productivity of 665mg FA/L/d were attained, and these values were comparable with those achieved using microalgae. The FA content of R. sphaeroides was around 35% of dry cell weight, mainly composed of vaccenic acid (C18:1, omega-7).
    Bioresource Technology 08/2013; 148C:277-282. · 4.75 Impact Factor
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    ABSTRACT: "Solubilization (SCOD/TCOD, chemical oxygen demand (COD), %)" is generally used as an indicator for the pretreatment effectiveness in anaerobic digestion (AD) of excess sludge. In the present work, ultrasonic (irradiation 5-60min) and alkaline pretreatments (pH 9-13) were applied to excess sludge individually and in combination. Biological methane potential tests were carried out using the whole part of pretreated sludge and only the soluble fraction. Although solubilization increased with pretreatment intensity increase, methane production was inconsistent with increased solubilization, due to the lower methane yield of soluble fraction. While the soluble fraction obtained under mild pretreatment condition (pH 9+ultrasonication 5min) showed 91% of methane yield, it was only 61% in case of severe pretreatment condition (pH 13+ultrasonication 60min). 25.8% of the pretreated sludge at (pH 13+ultrasonication 60min) consisted of soluble but non-biodegradable portion. These findings demonstrate that increased solubilization does not always result in enhanced AD efficiency.
    Bioresource Technology 06/2013; · 4.75 Impact Factor
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    ABSTRACT: In the present work, a continuous photo-fermentative hydrogen (H2) production from lactate was attempted at various hydraulic retention times (HRTs) (48–120 h). Electron balance was made at each operating conditions to elucidate different performances. At 120 h HRT, H2 production was negligible, while 42% and 52% of substrate electrons diverted towards cell growth and soluble microbial products (SMPs), respectively. After changing HRT to 96 h, H2 yield jumped to 2.3 mol-H2/mol-lactateadded with less SMPs production and minimal cell growth. The highest H2 production rate of 260 mL-H2/L-fermenter/d was also achieved at 96 h HRT. When HRT was further shortened to 72 and 48 h, H2 yield dropped to 1.4 and 0.2 mol-H2/mol-lactateadded, respectively. While almost all of the lactate was degraded at <72 h HRT, only 65% of the lactate was consumed at 48 h HRT. From 200th day, the feedstock was changed to lactate-rich acidified food waste, which was obtained via one-day fermentation of food waste and subsequent centrifugation. At 2 g chemical oxygen demand/L, substrate conversion efficiency reached 35%, which was slightly lower than that of feeding pure lactate. SMPs were found to be mainly consisted of low molecular weight compounds (<500 Da), and the majority of organic matters were aromatic proteins at 120 h HRT and it was shifted to humic-like region in 96 h HRT.
    International Journal of Hydrogen Energy 05/2013; 38(14):6161–6166. · 3.55 Impact Factor
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    ABSTRACT: The present work reports the first ever evaluation of the biological CH4 potential (BMP) of starfish, classified as invasive species. Since starfish contain a large amount of inorganic matter, only the supernatant obtained through grinding and centrifugation was used for BMP test. By applying response surface methodology, the individual and interactive effects of three parameters, inoculum/substrate ratios, substrate concentrations, and buffer capacities on CH4 production were investigated, and the maximum CH4 yield of 334mL CH4/g COD was estimated. In addition, continuous CH4 production was attempted using a two-stage (acidogenic sequencing batch reactor+methanogenic up-flow anaerobic sludge blanket reactor (UASBr)) fermentation process. Acidification efficiency was maximized at 2days of hydraulic retention time with valerate, butyrate, and acetate as main acids, and these were converted to CH4 with showing 296mL CH4/g CODadded. Overall, the two-stage fermentation process could convert 44% of organic content in whole starfish to CH4.
    Bioresource Technology 02/2013; · 4.75 Impact Factor
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    ABSTRACT: Rhodobacter sphaeroides evolves H2 by nitrogenase under photoheterotrophic growth conditions. The maximum accumulation level of H2 increases by up to 60% when the culture medium, in which succinate and ammonium ion are the major carbon and nitrogen sources, is supplemented with ethanol at 0.5% (vol/vol). Such an effect by ethanol is not observed when ammonium ion is omitted from the medium. Ethanol is not used as a carbon source under the conditions examined, and the utilization of succinate and ammonium ion by cell is not affected by ethanol. The nitrogenase activity in the presence of ethanol, which is approximately 60% higher compared with that determined in its absence, is regulated at the level of nif transcription since the similar increase in the β-galactosidase activity of nifH-lacZ fusion was reproducibly observed under the same conditions. Interestingly, nifA transcription also increased similarly in the presence of ethanol. Neither glnB nor glnK interruptions abolished the ethanol-mediated enhancement of H2 evolution. Thus, the presence of ethanol results in the enhancement of nitrogenase expression of R. sphaeroides through the increase of NifA expression in a manner independent of GlnB and GlnK.
    International Journal of Hydrogen Energy 11/2012; 37(21):15886–15892. · 3.55 Impact Factor
  • Dong-Hoon Kim, Mi-Sun Kim
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    ABSTRACT: In this study, a novel three-stage (lactate-+photo-H(2)+CH(4)) fermentation system was developed, which converts food waste to H(2) and CH(4), with an emphasis on achieving high H(2) yield. The system begins by first fermenting food waste to lactate, rather than acetate and butyrate, using indigenous lactic acid bacteria. Lactate fermentation effluent was then centrifuged, and the supernatant was used for H(2) production by photo-fermentation, while the residue was used for CH(4) production by anaerobic digestion. Overall, via the three-stage fermentation system, 41% and 37% of the energy content in the food waste was converted to H(2) and CH(4), respectively, corresponding to the electrical energy yield of 1146MJ/ton-food waste, which is 1.4 times higher value than that of previous two-stage dark (H(2)+CH(4)) fermentation system. The H(2) yield based on hexose input was 8.35mol H(2)/mol hexose(added), the highest value ever reported from actual organic waste.
    Bioresource Technology 10/2012; 127C:267-274. · 4.75 Impact Factor
  • Mi-Sun Kim, Jaehwan Cha, Dong-Hoon Kim
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    ABSTRACT: In this study, we investigated various cultural and operational factors to enhance electricity generation in a microbial fuel cell (MFC) using Geobacter sulfurreducens. The pure culture of G. sulfurreducens was cultivated using various substrates including acetate, malate, succinate, and butyrate, with fumarate as an electron acceptor. Cell growth was observed only in acetate-fed medium, when the cell concentrations increased 4-fold for 3 days. A high acetate concentration suppressed electricity generation. As the acetate concentration was increased from 5 to 20 mM, the power density dropped from 16 to 13 mW/m2, whereas the coulombic efficiency (CE) declined by about half. The immobilization of G. sulfurreducens on the anode considerably reduced the enrichment period from 15 to 7 days. Using argon gas to create an anaerobic condition in the anode chamber led to increased pH, and electricity generation subsequently dropped. When the plain carbon paper cathode was replaced by Pt-coated carbon paper (0.5 mg Pt/cm2), the CE increased greatly from 39% to 83%.
    Journal of Microbiology and Biotechnology 10/2012; 22(10):1395-400. · 1.40 Impact Factor
  • Dong-Hoon Kim, Hanna Son, Mi-Sun Kim
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    ABSTRACT: The information on continuous operation and the use of actual waste as a feedstock are essential for the practical application of photo-fermentative H2 production. For the first 200 days, continuous H2 production from lactate was attempted using purple non-sulfur (PNS) bacteria, Rhodobacter sphaeroides KD131, under an illumination of 110 W/m2. During the continuous operation, 30% of the fermenter volume was replaced by fresh feedstock once a day, and substrate concentration was gradually increased from 5 mM to 30 mM. H2 production was negligible at 5 mM, which was ascribed to the fact that the electrons contained in lactate were mostly consumed for cell growth and soluble microbial products (SMPs) production. As lactate concentration increased, H2 production gradually increased and reached a maximum at 20 mM, showing a substrate conversion efficiency (SCE) of 38%, a H2 yield of 2.3 mol H2/mol lactateadded, and a H2 production rate of 309 mL H2/L-fermenter/d. Further increases of lactate concentration resulted in a drop of H2 production (<1.0 mol H2/mol lactateadded). When the feedstock was changed to actual waste obtained from a 1-day lactate fermentation of food waste, stable H2 production was maintained, but showed a decreased SCE of 24%. It was speculated that the low performance was due to the fact that actual waste contained not only pure lactate but also other organic compounds that could not be utilized by PNS bacteria. In addition, compared to feeding with pure lactate, the electron consumption to the cell growth was higher in feeding with actual waste, which led to the lower performance.
    International Journal of Hydrogen Energy 10/2012; 37(20):15483–15488. · 3.55 Impact Factor
  • Mi-Sun Kim, Dong-Hoon Kim, Jaehwan Cha
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    ABSTRACT: The effect of culture conditions on photo-H2 production was investigated using the photosynthetic bacterium Rhodobacter sphaeroides KD131. When the initial cell concentrations were either below or above a threshold of 0.56 g-dcw/L, the H2 production decreased due to an imbalance between the biomass and the substrate. Malate- and succinate-fed cultures exhibited the highest substrate conversion to H2 production, whereas more than 85% of the substrate was utilized for cell growth in acetate- and butyrate-fed cultures. Compared with (NH4)2SO4, glutamate as a nitrogen source was more appropriate for the initial H2 production, but inhibited H2 evolution during extended cultivation due to released NH4+ ion. Even though the KD131 strain grew well under slightly acidic conditions, the pH value should be maintained in a neutral range in order to enhance H2 production. The highest H2 yield of 3.65 mol-H2/mol-succinate was achieved when the KD131 strain grew in the succinate–glutamate medium with an initial cell concentration of 0.56 g-dcw/L and the pH level controlled to 7.5.
    International Journal of Hydrogen Energy 10/2012; 37(19):14055–14061. · 3.55 Impact Factor
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    ABSTRACT: A frequently used fermentation manner in lactic acid (LA) production, batch fermentation by pure cultures, has a limited practicability: low volumetric productivity and high energy consumption. In this study, continuous LA fermentation was performed in a completely stirred tank reactor at 12h HRT, inoculated with anaerobic digester sludge. Glucose (25 g COD/L) was used as a feedstock and temperature was increased from 35 to 60°C. LA production significantly increased from 50°C, which was negligible up to 45°C, with obvious bacterial community change. At 50 and 55°C, LA production was maximized, reaching 23 g COD/L, corresponding to 92% LA conversion efficiency. Pyrosequencing analysis showed that microbial diversity was simplified at 50-60°C, and the sequences closely related with Bacillus coagulans became predominant, followed by Lactobacillus fermentum. An LA-producing upflow ananerobic sludge blanket reactor was successfully developed, which enhanced the productivity up to 4.8 gLA/L/h by shortening HRT to 4h.
    Bioresource Technology 05/2012; 119:355-61. · 4.75 Impact Factor
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    ABSTRACT: Hydrogen(H2)-producing bacterial community structures of the dark fermentation system in a batch reactor were investigated during 48 h by analyzing 16S rRNA gene sequences obtained from pyrosequencing. Organic wastes composed of food waste and sewage sludge were used as a feedstock. After heat treatment (90 °C for 20 min) of the feedstock, H2 was naturally evolved under anaerobic mesophilic conditions, showing a H2 yield of 2.26 mol H2/mol hexoseadded. The bacterial community structure of the initial inoculum (microbial community at the starting point (0 h)) combined with heat treated food waste and sewage sludge was mainly comprised of Proteobacteria and Bacteroidetes. After 6 h operation, the sequences that belong to other groups except Firmicutes decreased dramatically and were not observed at all in the latter samples. Clostridium spp., which were negligible in the inoculum, took over the main bacterial community by taking charge of H2 production. Among the phylum Firmicutes, the sequences closely related with Clostridium sordellii ATCC 9714T, Clostridium perfringens ATCC 13124T, and Clostridium butyricum ATCC 19398T became predominant in the time series within 48 h. Overall, the results showed how fast the Clostridium spp. overwhelmed the bacterial community in dark fermentative H2 production conditions, where they were at a negligible amount at the start.
    International Journal of Hydrogen Energy 05/2012; 37(10):8330–8337. · 3.55 Impact Factor
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    ABSTRACT: During photo-fermentative H(2) production, the effects of carbon and nitrogen sources on nitrogenase and hydrogenase activity, poly-β-hydroxybutyrate accumulation were investigated. In succinate/ammonium sulfate medium, H(2) was not detected for the first 6h because high ammonium concentration considerably reduced the nitrogenase activity to below 5 nmol/g-dcw/h. After 24h, 99% of the ammonium was consumed, and the nitrogenase activity increased to 296 nmol/g-dcw/h, accelerating H(2) production. In contrast, the ammonium in succinate/glutamate medium was much less, which led to rapid H(2) production in the beginning. However, H(2) evolution was repressed over time by increased ammonium. In the presence of H(2), hydrogenase activity increased with time regardless of the nitrogen source, and consequently, H(2) production was reduced. Compared with succinate, H(2) production in acetate media was severely limited due to increased pH over 9. During extended cultivation, the PHB accumulated in acetate media was 7 times higher than in succinate media.
    Bioresource Technology 04/2012; 116:179-83. · 4.75 Impact Factor
  • Dong-Hoon Kim, Mi-Sun Kim
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    ABSTRACT: In this study, a semi-continuous operation of photo-fermentative H2-producing reactor was attempted at various decanting volume ratios (DVR, decanting volume per day/total working volume, %), ranging 30-70%, using Rhodobacter sphaeroides KD131. H2 production was not efficient with showing low H2 yields of 0.2 and 0.5 mol H2/mol succinate(added) at 30% and 40% DVR, respectively. The low performance ascribed to the fact that over 70% of substrate electrons were diverted towards cell growth under these conditions. Meanwhile, cell growth was limited at DVR≥50%; therefore, higher H2 yields (>2.0 mol H2/mol succinateadded) were observed. Both the highest H2 yield of 3.7 mol H2/mol succinateadded and production rate of 1494 mL H2/L-reactor/d were achieved at 60% DVR. The content of soluble microbial products (SMPs) was measured, which accounted for 3-15% of substrate electrons. It was found that the largest (65-75%) portion of SMPs comprised low molecular-weight (<3 kDa).
    Bioresource Technology 01/2012; 103(1):481-3. · 4.75 Impact Factor
  • Dong-Hoon Kim, Mi-Sun Kim
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    ABSTRACT: In the present work, various carbon sources, xylose, glucose, galactose, sucrose, cellobiose, and starch were tested for thermophilic (60 °C) fermentative hydrogen production (FHP) by using the anaerobic mixed culture. An inoculum was obtained from a continuously-stirred tank reactor (CSTR) operated at pH 5.5 and HRT 12 h, and fed with tofu processing waste. The dominant species in the CSTR were found to be Thermoanaerobacterium thermosaccharolyticum and Clostridium thermosaccharolyticum, which are well known thermophilic H2-producers in anaerobic-state, and have the ability to utilize a wide range of carbohydrates. When initial pH was adjusted to 6.8 ± 0.1 but not controlled during fermentation, vigorous pH drop began within 5 h, and finally reached 4.0–4.5 in all carbon sources. Although over 90% of substrate removal was achieved for all carbon sources except cellobiose (71.7%), the fermentation performances were profoundly different with each other. Glucose, galactose, and sucrose exhibited relatively higher H2 yields whereas lower H2 yields were observed for xylose, cellobiose, and starch. On the other hand, when pH was controlled (pH ≥ 5.5), the fermentation performance was enhanced in all carbon sources but to a different extent. A substantial increase in H2 production was observed for cellobiose, a 1.9-fold increase of H2 yield along with a substrate removal increase to 93.8%, but a negligible increase for xylose. H2 production capabilities of all carbon sources tested were as follows: sucrose > galactose > glucose > cellobiose > starch > xylose. The maximum H2 yield of 3.17 mol H2/mol hexoseadded achieved from sucrose is equivalent to a 26.5% conversion of energy content in sucrose to H2. Acetic and butyric acids were the main liquid-state metabolites of all carbon sources while lactic acid was detected only in cellobiose, starch and xylose exhibiting relatively lower H2 yields.
    Fuel and Energy Abstracts 01/2012;
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    ABSTRACT: The effect of sewage sludge (SWS) addition on the H2 fermentation of food waste (FW) was investigated. It was found that a slight addition of SWS (10:1=FW:SWS on a COD basis) significantly enhanced the H2 fermentation performance, not only increasing the total amount of H2 produced but accelerating the whole reaction, shortening the lag period, and increasing the H2 production rate. Substrate degradation and microbial germination were also facilitated by SWS addition. A simple calculation reveals that the increased amount of H2 production derived mostly from FW, indicating that SWS addition synergistically enhanced H2 fermentation performance. This was attributed to the existence of Fe and Ca at much higher concentrations in the SWS compared to the FW. The batch process treating a mixture of FW and SWS was repeated and showed an average H2 yield of 2.11 ± 0.20 mol H2/mol hexose(added), which was 13% higher than that of FW treated alone.
    Bioresource Technology 05/2011; 102(18):8501-6. · 4.75 Impact Factor
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    ABSTRACT: The effect of initial pH from 5.0 to 9.0 on H2 fermentation of food waste was investigated. In this batch experiment, however, unlike previous studies for initial pH, operational pH was maintained at 5.0 by the addition of alkaline solution. Although the period for pH drop from the initial values to 5.0 was less than one-tenth of the entire fermentation, this short period significantly affected the H2 production performance. At initial pH 6.0-9.0, successful H2 yield of 1.3-1.9 mol H2/mol hexose(added) was achieved with a peak value at pH 8.0. The H2 yield achieved at initial pH 8.0 was corresponded to the 8.13% of total energy content in the substrate. At initial pH 5.0, the smallest butyrate production, but the highest ethanol production was detected, indicating unfavorable conditions for H2 production. There was no significant relationship between total required amount of alkaline solution and initial pH values.
    Bioresource Technology 03/2011; 102(18):8646-52. · 4.75 Impact Factor
  • Dong-Hoon Kim, Mi-Sun Kim
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    ABSTRACT: Biological H2 production offers distinctive advantages for environmental protection over existing physico-chemical methods. This study focuses specifically on hydrogenases, a class of enzymes that serves to effectively catalyze H2 formation from protons or oxidation to protons. It reviews the classification schemes (i.e., [NiFe]-, [FeFe]-, and [Fe]-hydrogenases) and properties of these enzymes, which are essential to understand the mechanisms for H2 production, the control of cell metabolism, and subsequent increases in H2 production. There are five kinds of biological hydrogen production methods, categorized based upon the light energy requirement, and feedstock sources. The genetic engineering work on hydrogenase to enhance H2 production is reviewed here. Further discussions in this study include nitrogenase, an enzyme that normally catalyzes the reduction of N2 to ammonia but is also able to produce H2 under photo-heterotrophic conditions, as well as other applicable fields of hydrogenase other than H2 production.
    Bioresource Technology 03/2011; 102(18):8423-31. · 4.75 Impact Factor

Publication Stats

482 Citations
111.09 Total Impact Points

Institutions

  • 2002–2014
    • Korea Institute of Energy Research
      • • Clean Fuel Department
      • • Wind Energy Research Center
      Sŏul, Seoul, South Korea
  • 2006–2008
    • Sogang University
      • Department of Life Science
      Seoul, Seoul, South Korea
    • Sungkyunkwan University
      • Department of Chemical Engineering
      Seoul, Seoul, South Korea
  • 2005
    • Pusan National University
      • Division of Chemical and Biomolecular Engineering
      Tsau-liang-hai, Busan, South Korea