Immobilization of the Hyperthermophilic Archaeon Thermococcus onnurineus Using Amine-coated Silica Material for H₂ Production

배승섭,나정걸,이성목,강성균,이현숙,이정현,김태완,Bae, Seung Seob,Na, Jeong Geol,Lee, Sung-Mok,Kang, Sung Gyun,Lee, Hyun Sook,Lee, Jung-Hyun,Kim, Tae Wan The Korean Society for Microbiology and Biotechnol 2015 한국미생물·생명공학회지 Vol.43 No.3

초고온성 고세균 Thermococcus onnurineus NA1은 개미산, 일산화탄소, 또는 전분 등을 이용해서 수소를 생산하는 것으로 알려져 있다. 본 연구에서는 T. onnurineus NA1의 고정화 세포를 이용한 수소생산을 고찰하였다. 고정화 실험결과, T. onnurineus NA1은 표면에 아민기가 코팅된 규조토 담체에 정전기적 인력에 의해 효과적으로 고정화되었고, 1 g의 담체에 고정화 될 수 있는 최대 세포의 양은 71.7 mg-dcw로 확인되었다. 고정화 세포를 이용한 세 번의 반복회분식 배양을 통해 개미산으로부터 수소생산 특성을 고찰하였고, 그 결과 배양이 반복됨에 따라 고정화 세포 농도의 증가에 기인하여 초기수소생산속도가 2.3 에서 4.0 mmol l⁻¹ h⁻¹로 상당량 증가됨이 관찰되었다. 따라서, T. onnurineus NA1의 고정화세포 시스템은 수소생산을 위한 좋은 대안이 될 수 있을 것으로 사료된다. 본 연구는 초고온성 고세균의 고정화세포를 수소생산에 적용한 첫 번째 사례이다. Previously we reported that the hyperthermophilic archaeon, Thermococcus onnurineus NA1 is capable of producing hydrogen (H₂) from formate, CO or starch. In this study, we describe the immobilization of T. onnurineus NA1 as an alternative means of H₂ production. Amine-coated silica particles were effective in immobilizing T. onnurineus NA1 by electrostatic interaction, showing a maximum cell adsorption capacity of 71.7 mg-dried cells per g of particle. In three cycles of repeated-batch cultivation using sodium formate as the sole energy source, immobilized cells showed reproducible H₂ production with a considerable increase in the initial production rate from 2.3 to 4.0 mmol l⁻¹ h⁻¹, mainly due to the increase in the immobilized cell concentration as the batch culture was repeated. Thus, the immobilized-cell system of T. onnurineus NA1 was demonstrated to be feasible for H₂ production. This study is the first example of immobilized cells of hyperthermophilic archaea being used for the production of H₂.

Role of the oxidizing agent in the etching of 4H-SiC substrates with molten KOH

Na, M.,Kang, I. H.,Moon, J. H.,Bahng, W. 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol. No.

<P>A novel etching solution using molten potassium hydroxide (KOH) for the identification of dislocation types in a silicon-carbide (SiC) epilayer is identified. Threading screw dislocations (TSDs) and threading edge dislocations (TEDs) are rarely useful for size-based differentiation of etch pits in highly nitrogen (N)-doped SiC through conventional KOH etching. In this study, we report the role of sodium peroxide (Na2O2) and potassium dioxide (KO2) as oxidizing agent additives to the etchant for identifying the dislocation types in highly N-doped 4H-SiC. A Na2O2-KOH phase diagram was calculated to predict the chemical composition of the etchant. Solid-phase Na2O2 remained in the system when added to the etchant at concentrations greater than 13-wt% Na2O2, and it provided excess oxygen to the etchant. We experimentally confirmed that etch pit shapes became more hexagonal and that the etch pit sizes of TSDs and TEDs differed more greatly when more than 20-wt% Na2O2 was added to the etchant. We also found that the size distribution of TEDs was much smaller than that of TSDs after etching using Na2O2-KOH. Dissolved oxygen played an essential role in enhancing the anisotropic etching of highly N-doped SiC and allowed the dislocation types to be identified.</P>

Role of the Oxidizing Agent in the Etching of 4H-SiC Substrates with Molten KOH

Moonkyong Na,In-Ho Kang,Jeong Hyun Moon,Wook Bahng 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.11

A novel etching solution using molten potassium hydroxide (KOH) for the identification of dislocation types in a silicon-carbide (SiC) epilayer is identified. Threading screw dislocations (TSDs) and threading edge dislocations (TEDs) are rarely useful for size-based differentiation of etch pits in highly nitrogen (N)-doped SiC through conventional KOH etching. In this study, we report the role of sodium peroxide (Na2O2) and potassium dioxide (KO2) as oxidizing agent additives to the etchant for identifying the dislocation types in highly N-doped 4H-SiC. A Na2O2-KOH phase diagram was calculated to predict the chemical composition of the etchant. Solid-phase Na2O2 remained in the system when added to the etchant at concentrations greater than 13-wt% Na2O2, and it provided excess oxygen to the etchant. We experimentally confirmed that etch pit shapes became more hexagonal and that the etch pit sizes of TSDs and TEDs differed more greatly when more than 20-wt% Na2O2 was added to the etchant. We also found that the size distribution of TEDs was much smaller than that of TSDs after etching using Na2O2-KOH. Dissolved oxygen played an essential role in enhancing the anisotropic etching of highly N-doped SiC and allowed the dislocation types to be identified.

Utilization of Waste Bittern as a Source for Magnesium Production and an Absorbent for Capturing Carbon Dioxide

( Choonki Na ),( Hyunju Park ),( Sangyul Kang ) 한국폐기물자원순환학회(구 한국폐기물학회) 2015 한국폐기물자원순환학회 3RINCs초록집 Vol.2015 No.-

This study examined the suitability of waste bittern, from slattern, as a source for magnesium (Mg) production and an absorbent for CO₂. A sequential two-step process was investigated; i) Mg was recovered by adding NaOH and precipitating as Mg(OH)₂, and ii) CO₂ was captured using the ammonia-soda process where ammoniated residual bittern reacted with CO₂. At NaOH:Mg molar ratios of 2.70:1 to 2.75:1 and pH 9.5-10, >99% of Mg ions (Mg ²⁺) precipitated from the bittern. Precipitate recovery was 100-120 g/L of the bittern and contained 94% Mg(OH)₂ after washing with water. The NaOH concentration did not significantly influence Mg²⁺ precipitation efficiency; however, it did affect the Na+ concentration in the precipitate filtrate considerably. The precipitate filtrate containing a large amount of Na+ was able to capture CO ₂ effectively with an ammonia catalyst (NH4OH≥3%), forming NaHCO₃. Higher Na⁺ concentrations resulted in higher absorption of CO₂, because NaHCO₃ solubility influences CO₂ capture in the ammonia-soda process. The optimum amount of NH4OH about 5%, at whichNaHCO₃ precipitate (97% purity) recovery was 120 g/L, which is equivalent to CO₂ capture of 63 g/L. The results show that bittern may be a suitable resource for Mg production and CO₂ capture.

Electrochemical properties of ultrafine Sb nanocrystals embedded in carbon microspheres for use as Na-ion battery anode materials

Ko, You Na,Kang, Yun Chan The Royal Society of Chemistry 2014 Chemical communications Vol.50 No.82

<P>Ultrafine Sb nanocrystals, uniformly distributed in a carbon matrix with a microspherical morphology, were synthesized by one-pot spray pyrolysis. The Sb–carbon composite microspheres exhibited good Na-storage properties with stable cyclability, a capacity retention of 90% over 100 cycles, and good rate performance.</P> <P>Graphic Abstract</P><P>The preparation of Sb–carbon composite microspheres and their electrochemical performance are investigated. Sb nanocrystals embedded in a microspherical carbon matrix exhibited superior Na-storage performances. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4cc05275g'> </P>

Hollow Cobalt Selenide Microspheres: Synthesis and Application as Anode Materials for Na-Ion Batteries

Ko, You Na,Choi, Seung Ho,Kang, Yun Chan American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.10

<P>The electrochemical properties of hollow cobalt oxide and cobalt selenide microspheres are studied for the first time as anode materials for Na-ion batteries. Hollow cobalt oxide microspheres prepared by one-pot spray pyrolysis are transformed into hollow cobalt selenide microspheres by a simple selenization process using hydrogen selenide gas. Ultrafine nanocrystals of Co3O4 microspheres are preserved in the cobalt selenide microspheres selenized at 300 degrees C. The initial discharge capacities for the Co3O4 and Cobalt selenide microspheres selenized at 300 and 400 degrees C are 727, 595, and 586 mA h g(-1), respectively, at a current density of 500 mA g(-1). The discharge capacities after 40 cycles for the same samples are 348, 467, and 251 mA h g(-1), respectively, and their capacity retentions measured from the second cycle onward are 66, 91, and 50%; respectively. The hollow cobalt selenide microspheres have better rate performances than the hollow cobalt oxide microspheres.</P>

Immobilization of the Hyperthermophilic Archaeon Thermococcus onnurineus Using Amine-coated Silica Material for H2 Production

( Seungseob Bae ),( Jeonggeol Na ),( Sungmok Lee ),( Sunggyun Kang ),( Hyunsook Lee ),( Junghyun Lee ),( Taewan Kim ) 한국미생물생명공학회(구 한국산업미생물학회) 2015 한국미생물·생명공학회지 Vol.43 No.3

Previously we reported that the hyperthermophilic archaeon, Thermococcus onnurineus NA1 is capable of producing hydrogen (H2) from formate, CO or starch. In this study, we describe the immobilization of T. onnurineus NA1 as an alternative means of H2 production. Amine-coated silica particles were effective in immobilizing T. onnurineus NA1 by electrostatic interaction, showing a maximum cell adsorption capacity of 71.7 mg-dried cells per g of particle. In three cycles of repeated-batch cultivation using sodium formate as the sole energy source, immobilized cells showed reproducible H2 production with a considerable increase in the initial production rate from 2.3 to 4.0 mmol l-1 h-1, mainly due to the increase in the immobilized cell concentration as the batch culture was repeated. Thus, the immobilized-cell system of T. onnurineus NA1 was demonstrated to be feasible for H2 production. This study is the first example of immobilized cells of hyperthermophilic archaea being used for the production of H2.

Comparative AFLP Profiles among Strains of Korean Races of Xanthomonas oryzae pv. oryzae.

Kang,Mi-Hyung,Lee,Du-Ku,Noh,Tae-Hwan,Shim,Hyeong-Kwon,Na,Seung-Yong,Kim,Jae-Duk 한국자원식물학회 2004 Plant Resources Vol.7 No.1

We used an amplified fragment length polymorphism (AFLP) analysis, a novel PCR-based technique, to differentiate Xanthomonas oryzae pv. oryzae (Xoo) of Korean races. The 6 strains of Xoo K1, K2, K3 races were tested with 81 AFLP primer combinations to identify the best selective primers. The primer combinations were selected according to their reproducibility, number of polymorphic bands and polymorphism detected among Xoo strains. 18 strains of Xoo K1, K2 and K3 races were analyzed with the selected combinations of primer set. Some primer combinations (Eco R I +1 / Mse I+1) could differentiate Xoo of Korean races that were not distinguished by other fingerprinting analysis. Thus AFLP fingerprinting permitted very fine discrimination among different races.

Cost Management of the K2 Main Battle Tank by Hyundai Rotem Company

Kang,Ho Shin,Na,In Sung,Jung,DongSuk 韓國防衛産業學會 2008 韓國防衛産業學會誌 Vol.15 No.1

현대의 전장상황은 네트워크전, 정보전, 로봇전, 우주전 등과 같이 고도로 정밀하고 복잡해짐과 동시에 장비 개발을 위해서 요구되는 비용은 기하급수적으로 급증하고 있는 추세이다. 그러므로 한정된 예산하에서 사업을 성공적으로 수행하기 위해서는 개발 초기부터 목표비용 설정 및 관리와 비용 절감 활동이 필수적으로 요구되고 있다.따라서 본 연구에서는 국방분야에서 추진하고 있는 비용관리 정책을 소개하고 K2 전차를 개발하면서 현대로템에서 적용한 목표비용 개념, 비용관리 절차 및 방법론을 제시하고 대표적인 비용절감 사례를 소개하고자 한다.

Chitosan/oleamide Nanofluid for Enhancing Gas Utilization Efficiency in C1-gas Bioconversion

Eungsu KANG,Hyunsuk CHOI,Ji Yeong LEE,Min-sik KIM,Jeong Geol NA,Yoo Seong CHOI 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.10

Microbial biotransformation using C1-gases (CH₄, CO) is a notable technique for sustainable, carbon-neutral chemical and fuel production. However, the low mass transfer coefficient (KLa) of C1-gases in biological processes has hampered the efficient production of value-added materials, despite efficient, nonnative strains having been recently developed. Here, we constructed a nanofluid material mainly composed of chitosan and oleamide (CS/OA), which was stably suspended with a particle size of 120.7 ± 39.0 ㎚ in aqueous culture media below pH 7.5. The kLa value was enhanced more than 1.5-fold with a reduction of surface tension even in the 0.0001 % (w/v) CS/OA nanofluid. In addition, when the nanofluid was applied into media for seed-cultivation of three C1-gas utilizing strains such as Methylomonas sp. DH-1, M. trichosporium OB3b, and Thermococcus onnurineus NA1 156T, the CS/OA nanoparticles attached to the cell surface, leading to a morphological change in the cell surface at extended lag-phase, and enhanced the specific cell growth rates (μmax), gas utilization efficiency in log-phase. Remarkably, the adapted strains from the seed culture using the CS/OA nanofluid media also had enhanced μmax in a subsequent subculture and the main culture using conventional culture media, resulting in higher C1 gas consumption, cell growth, and metabolite production such as formate and succinate. These results showed that the CS/OA nanofluid could be an effective medium component to enhance the gas utilization efficiency in C1-gas microbial bioconversion.Microbial biotransformation using C1-gases (CH₄, CO) is a notable technique for sustainable, carbon-neutral chemical and fuel production. However, the low mass transfer coefficient (KLa) of C1-gases in biological processes has hampered the efficient production of value-added materials, despite efficient, nonnative strains having been recently developed. Here, we constructed a nanofluid material mainly composed of chitosan and oleamide (CS/OA), which was stably suspended with a particle size of 120.7 ± 39.0 ㎚ in aqueous culture media below pH 7.5. The kLa value was enhanced more than 1.5-fold with a reduction of surface tension even in the 0.0001 % (w/v) CS/OA nanofluid. In addition, when the nanofluid was applied into media for seed-cultivation of three C1-gas utilizing strains such as Methylomonas sp. DH-1, M. trichosporium OB3b, and Thermococcus onnurineus NA1 156T, the CS/OA nanoparticles attached to the cell surface, leading to a morphological change in the cell surface at extended lag-phase, and enhanced the specific cell growth rates (μmax), gas utilization efficiency in log-phase. Remarkably, the adapted strains from the seed culture using the CS/OA nanofluid media also had enhanced μmax in a subsequent subculture and the main culture using conventional culture media, resulting in higher C1 gas consumption, cell growth, and metabolite production such as formate and succinate. These results showed that the CS/OA nanofluid could be an effective medium component to enhance the gas utilization efficiency in C1-gas microbial bioconversion.