• Journal of Microbiology and Biotechnology
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• 제18권4호
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• pp.735-741
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• 2008

In our previous study, a surfactant-coated Candida rugosa lipase immobilized in microemulsion-based organogels was exploited for the synthesis of ethyl isovalerate. In the present study, we are focusing on the effective reuse of lipase immobilized in microemulsion-based organogels (MBGs) in terms of retainment of the catalytic activity. As water is one of the co-products in esterification reactions, the removal of water becomes a priority to allow the reaction to work in the forward direction and to prevent back hydrolysis. Taking this fact into consideration, the lipase-containing microemulsion-based organogels were given pretreatment and/or several intermittent treatments with dry reverse micellar solution of AOT in organic solvent during repeated cycles of ester synthesis. The pretreated MBGs with dry reverse micellar solution exhibited lower water content and higher initial rates of esterification in comparison with untreated freshly prepared MBGs. The esterification efficiency of untreated MBGs started decreasing after 5 cycles of reuse and was almost completely lost by the end of the $8^{th}$ cycle. In contrast, pretreated MBGs exhibited a gradual decrease in esterification efficiency after 5 cycles and retained about 80% of the initial activity at the end of the $8^{th}$ cycle. The intermittent treatment of MBGs after every 3 cycles resulted in enhanced reusability of immobilized lipase for up to 9 cycles without significant loss in esterification activity, after which it resulted in a slow decrease in activity with about 27% lower activity at the end of the $12^{th}$ cycle. Furthermore, the treatment conditions such as concentration of AOT in liquid dessicant and time of treatment were optimized with respect to our system. The granulated MBGs proved to be better in terms of initial esterification rates (1.2-fold) as compared with the pelleted MBGs.

• 약학회지
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• 제50권1호
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• pp.1-7
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• 2006

The purpose of the present study was to formulate the aqueous solution of 1-cyclopent-3-enylmethyl-6(3,5-dimethyl-benzoyl)-5-ethyl-1H-pyrimidine-2,4-dione (CPD), a novel antivirus compound containing pirimidine structure. For this purpose, the effects of various solubilization agents such as cosolvents [ethanol, propylene glycol (PG), polyethylene glycol 300 (PEG 300), polyethylene glycol 400 (PEG 400), glycerin], surfactants (Tween 80, Cremophor$^{(R)}$ RH40, Cremophor$^{(R)}$ EL, Poloxamer 407, Poloxamer 188) and a complexation agent [hydroxypropyl-${\beta}$-cyclodextrin (HPBCD)] , on the solubility of CPD in aqueous solution were evaluated. The solubility of CPD in water was under $1\;{\mu}g/ml$ at $20^{\circ}C$. Cosolvents such as ethanol, PG, PEG 300, PEG 400 and glycerin did not enhance the solubility of CPD at the $0{\sim}40\%$ concentration range. The solubility of CPD was significantly elevated by the addition of cosolvents over the $80\%$ concentration range. On the other hand, tween 80, Cremophor$^{(R)}$ L, Cremophor$^{(R)}$ RH40, and HPBCD showed enhanced effects on the solubility of CPD. The enhanced effects of Poloxamer 407 or Poloxamer 188 on the CPD solubility were less pronounced compared with tween 80, Cremophor$^{(R)}$ L or Cremophor$^{(R)}$ RH40. As a results, tween 80 aqueous solution was selected as an optimum solvent system. The aqueous solutions containing $20\%$ tween 80 were formulated as a dosing solution containing CPD for its intraperitoneal and intrahypodermic administration, respectively, The formular showed physical stability after stored for 7 days at $4^{\circ}C$.

• Journal of Microbiology and Biotechnology
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• 제10권2호
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• pp.251-257
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• 2000

Chitin synthases are identified as key enzymes of chitin biosynthesis in most of the fungi. Among them, chitin synthase II has been reported to be and essential enzyme in chitin biosynthesis, and exists as a membrane-bound form. To search and screen new antifungal agents from natural resources to inhibit chitin synthase II, the assay conditions were established using the enzyme isolated from Saccharomyces cerevisiae ECY38-38A(pAS6) that overproduces only chitin synthase II. This enzyme was activated only by partial proteolysis with trypsin. Its actibity reached the maximum at $80{\;}\mu\textrm{g}/ml$ of trypsin and was strongly stimulated by 2.0 mM $Co^{2+}$, 1.0 nM UDP-[$^{14}C$]-GicNAc, and 32 mM free-GlcNAc. Under these assay conditions, the highest chitin synthase II activity was observed by incubation at $30^{\circ}C$ for 90 min. However, and extremely narrow range of organic solvents up to as much as 25% of DMSO and 25% of MeOH was useful for determining optimal assay conditions. After a search or potent inhibitors of chitin synthase II from natural resources, prodigiosin was isolated from Serratia marcescens and purified by solvent extration and silica gel column chromatographies. The structure of prodigiosin was determined by UV, IR, Mass spectral, and NMR spectral analyses. Its molecular weight and formula were found to be 323 and $C_{20}H_{25}N_{3}O$, respectively. Prodigiosin ingibited chitin synthase II by 50% at the concentration of $115{\;}\mu\textrm{g}/ml$.

• Applied Biological Chemistry
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• 제19권1호
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• pp.24-30
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• 1976

갈대(Phragmites communis Trin.)의 지하경(地下莖)을 암소(暗所)에서 3일간 기른 싹의 메타놀 추출물(抽出物)을 TLC로 분리동정(分離同定)하였으며, 아래와 같은 결과를 얻었다. 1. 검정(檢定)된 화합물은 주(主)로 indole amine류(類)였으며, serotonin, tryptamine, tryptophan등은 표준화합물과의 co-chromatography에 의해 동정되었고, 용매계를 달리하여 구한 Rf치 및 발색특성을 문헌과 비교하여 추정한 것으로는 bufotenine, N-methylserotonin, N,N-dimethyltryptamine이었으며, Skatole 및 gramine의 존재(存在)의 가능성도 추측(推測)되었다. 2. 갈대 생육의 일정기간 동안 indole 화합물의 methyl화(化) 및 hydroxyl화(化) 대사계(代謝系)의 활성(活性)이 강하게 나타나고 있다고 생각된다. 3. 본 실험에서 처음 시도된 "overlap"점적(點滴)법을 사용한 TLC방법(方法)은 시료중의 방해물질(妨害物質)의 영향으로 시료와 표준품 간에 동일 화합물(化合物)이 Rf치에 차이(差異)를 나타낼 때 시료중의 동일(同一) 화합물의 검정에 유용한 방법이 될 것이다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.332-332
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• 2010

We have successfully demonstrated the inkjet printing method to create $Al_2O_3$ films withouWe have successfully demonstrated the inkjet printing method to create $Al_2O_3$ films without a high temperature sintering process. In order to remove the coffee ring effect in the ink drop, we have introduced a co-solvent system in order to create Marangoni flow in the ink drop, which leads to the dense packing of ceramic powders on the substrate during inkjet process. The packing density of the Inkjet-printed $Al_2O_3$ films is around 60% (max. 70%) which is very high compared to the value obtained from the same material films by other conventional methods such as film casting, dip coating process, etc. The voids inside the films (which are around 40% of the entire film volume) are filled with the polymer resin (Cyanate ester) by the infiltration process. This resin infiltration is also implemented by the inkjet printing process right after the Ah03 film ink-jetting process. The microstructures of the printed $Al_2O_3$ films are investigated by Scanning Electron Microscope (SEM) to understand the degree of packing density in the printed films. The inkjet-printed $Al_2O_3$ films have been characterized to investigate its thickness and roughness. Quality factor of the printed $Al_2O_3$ film is also measured to be over 300 at 1MHz.

• Bulletin of the Korean Chemical Society
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• 제32권3호
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• pp.867-872
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• 2011

For the prolonged delivery and sustained release rates of low molecular weight drugs, poly(lactic-co-glycolic acid) (PLGA) microparticles containing the drug SKL-2020 have been investigated. On increasing polyvinyl alcohol (PVA) concentration (from 0.2% to 5%), the size of microparticles decreased (from $48.02{\mu}m$ to $10.63{\mu}m$) and more uniform size distribution was noticeable due to the powerful emulsifying ability of PVA. A higher drug loading (from 5% to 20%) caused a larger concentration gradient between 2 phases at the polymer precipitation step; this resulted in decreased encapsulation efficiency (from 34.19% to 25.67%) and a greater initial burst (from 61.71% to 70.05%). SKL-2020-loaded PLGA microparticles prepared with different fabrication conditions exhibited unique release patterns of SKL-2020. High PVA concentration and high drug loading led to an initial burst effect by rapid drug diffusion through the polymer matrix. Since PLGA microparticles enabled the slow release of SKL-2020 over 1 week in vitro and in vivo, more convenient and comfortable treatment could be facilitated with less frequent administration. It is feasible to design a release profile by mixing microparticles that were prepared with different fabrication conditions. By this method, the initial burst could be repressed properly and drug release rate could decrease.

• 폴리머
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• 제32권5호
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• pp.409-414
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• 2008

전기방사법으로 이온염을 함유하는 TFE/증류수 혼합용매를 이용하여 젤라틴 나노섬유를 제조하였으며, 얻어진 나노섬유의 평균직경은 $110{\sim}125\;nm$였다. 이온염의 농도가 증가할수록 비드의 발생이 줄어들고 균일한 나노섬유 제조가 가능하였다. 이는 이온염의 첨가에 의한 젤라틴 용액의 점도 및 전도도가 증가함에 기인하는 것으로 확인되었다. 특히 일가이온보다 이가이온을 사용할 경우 점도 및 전도도의 증가에 더 효과적이었으며 이들 이온염은 분자간 소수성 상호작용뿐만 아니라 젤라틴 분자의 입체구조 정렬에도 영향을 주었다. 그러나 이온염 농도에 따른 나노섬유의 직경변화는 관찰되지 않았다. 제조된 나노섬유를 이용한 XRD분석 결과 이온염의 농도가 증가할수록 젤라틴 분자의 재결정화에 의해 나노섬유의 결정화도가 높아졌다.

• Journal of Electrochemical Science and Technology
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• 제13권1호
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• pp.78-89
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• 2022

ANODE-free Li-metal batteries (AFLMBs) operating with Li of cathode material have attracted enormous attention due to their exceptional energy density originating from anode-free structure in the confined cell volume. However, uncontrolled dendritic growth of lithium on a copper current collector can limit its practical application as it causes fatal issues for stable cycling such as dead Li formation, unstable solid electrolyte interphase, electrolyte exhaustion, and internal short-circuit. To overcome this limitation, here, we report a novel dual-salt electrolyte comprising of 0.2 M LiPF₆ + 3.8 M lithium bis(fluorosulfonyl)imide in a carbonate/ester co-solvent with 5 wt% fluoroethylene carbonate, 2 wt% vinylene carbonate, and 0.2 wt% LiNO₃ additives. Because the dual-salt electrolyte facilitates uniform/dense Li deposition on the current collector and can form robust/ionic conductive LiF-based SEI layer on the deposited Li, a Li/Li symmetrical cell exhibits improved cycling performance and low polarization for over 200 h operation. Furthermore, the anode-free LiFePO₄/Cu cells in the carbonate electrolyte shows significantly enhanced cycling stability compared to the counterparts consisting of different salt ratios. This study shows an importance of electrolyte design guiding uniform Li deposition and forming stable SEI layer for AFLMBs.

• 폴리머
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• 제38권2호
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• pp.164-170
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• 2014

본 연구에서는 신경세포인 슈반세포(SC)의 증식에 가장 적합한 생체재료를 연구하였다. 락타이드 글리콜라이드 공중합체(PLGA)에 탈미네랄 골분(demineralized bone particle, DBP), 소장점막하조직(small intestine submucosa, SIS), 그리고 실크를 각각 20% 첨가하여, 용매 증발법으로 각각의 필름을 제조하고, SC세포의 부착과 증식을 확인하기 위해 MTT, SEM 그리고 RT-PCR 분석을 실시하였다. 또한 필름의 친수성을 확인하기 위해 접촉각을 측정하였다. 분석 결과, PLGA/DBP 20% 필름에서 높은 친수성을 보였으며, SC의 부착과 증식률이 다른 군에 비해 크게 증가한 것을 확인할 수 있었다. 따라서 PLGA/DBP 필름은 중추신경재생 재료로 활용할 수 있을 것으로 사료된다.

• 청정기술
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• 제28권3호
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• pp.203-209
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• 2022

본 연구에서는 태양광 폐모듈 해체과정에서 회수한 실리콘을 재활용하여 기계구조용 메커니컬 실을 제조하는 공정에 대해 전과정평가 방법에 의한 환경성평가를 수행하였다. 재활용 실리콘은 고순도 정제 후 탄소와 반응시켜 β-SiC 입자로 합성하고 압축 성형, 소결 및 열처리를 거쳐 제품을 생산한다. 현장 데이터 수집 및 환경부 LCI DB를 활용하여 각 단계별로 자원고갈, 산성화, 부영양화, 지구온난화, 오존층파괴, 광화학산화물 등 6개 영역의 환경영향을 산정하였다. 영향범주 별 환경영향은 지구온난화 45 kg CO₂, 광화학산화물 2.23 kg C₂H₄으로 크게 나타났으며 가중화 분석결과 광화학산화물, 자원고갈 및 지구온난화에 의한 환경영향이 98.7%로 높은 기여도를 차지하였다. 원료 실리콘과 탄소를 미분쇄 혼합하는 습식공정과 β-SiC 과립화 공정이 주요한 환경영향 유발요인이므로 건식공정으로 전환 및 대기 배출되는 용매는 회수하여 재이용하는 시스템으로 개선이 필요하다. 폐모듈 실리콘의 재활용에 의해 자원고갈의 영향은 53.9%, 지구온난화는 60.7% 감소하며 가중화 결과 전체적인 환경영향이 27% 감소하는 것으로 분석되어 폐모듈 재활용은 자원절약과 탄소중립 실현의 주요 수단이 될 수 있음을 LCA 분석으로 확인하였다.