• International Journal of Air-Conditioning and Refrigeration
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• 제16권3호
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• pp.89-99
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• 2008

Indoor ozone has received attention because of its well-documented adverse effects on health. In addition to the inherently harmful effects of ozone, it can also initiate a series of reactions that generate potentially irritating oxidation products, including free radicals, aldehydes, organic acids and secondary organic aerosols (SOA). Especially, ozone reacts actively with terpene. The overarching goal of this work was to better understand ozone and terpene distributions within rooms. Towards this end, the paper has two parts. The first describes the development of a cylindrical test chamber that can be used to obtain the second order rate constant $(k_b)$ for the bi-molecular chemical reaction of ozone and terpene in the air phase. The second consists of model room experiments coupled with Computational Fluid Dynamics (CFD) analysis of the experimental scenarios to obtain ozone and terpene distributions in various turbulent flow fields. The results of CFD predictions were in reasonable agreement with the experimental measurements.

• 한국환경과학회지
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• 제30권12호
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• pp.1005-1014
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• 2021

Organic contaminants can be released into water environments due to chemical accidents and exist as dissolved and non-aqueous phase liquids (NAPL). Fenton oxidation was tested for bisphenol A and nitrobenzene as model organic contaminants in dissolved and NAPL states. Fenton oxidation was successfully applied for both of the dissolved and NAPL states of the two pollutants and the results indicated that a quick treatment was needed to reduce the risk from a chemical accidents instead of carrying out oxidation after the contaminants dissolve in water. A set of Fenton reactions were tested under seawater conditions because chemical accidents often occurs in the ocean. Chloride ions act as radical scavengers and inhibit Fenton oxidation. The reaction rate is inversely proportional to salt contents and the reduced reaction rate can be compensated by increasing the quantity of the oxidizing agents. The current study showes that Fenton oxidation could be applied as a quick treatments for organic contaminant in dissolved and NAPL state organic contaminants released as a result of leaks or chemical accidents.

• 유기물자원화
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• 제17권4호
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• pp.66-73
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• 2009

음식물류폐수와 축산분뇨를 1:1로 혼합한 폐수를 대상으로 고온/중온의 이상혐기소화공정을 실시하였고 혼합폐수내 병원성미생물의 존재 및 소화과정중 미생물상의 변화를 살펴보았다. 혼합원액내 미생물은 대장균, 분변성 장내세균, 대장균군 등의 장내세균총을 비롯하여 식중독을 일으키는 포도상구균과 살모넬라, 이질의 원인균인 쉬겔라, 유가공제품내 대표적 병원성세균인 리스테리아 및 효모 등이 검출되었다. 혐기소화의 안정화시기는 반응후 21일이 지나서부터 시작하였으며, 이 시기를 전후하여 산 발효조와 메탄발효조에서 각각 80% 및 90% 내외의 가파른 감소율을 보이며 대부분의 미생물이 감소되었다. 안정화이후 유기물의 평균분해율은 메탄발효조에서 60% 내외를 기록하였다. 메탄 발효조를 거친 소화액내 미생물개체수는 반응종료 시점에서 대부분 불검출 되었으나, 리스테리아와 포도상구균의 경우, 비교적 완만한 감소세를 보이며 반응최종일까지 검출이 되고 있음을 확인하였다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제10권1호
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• pp.99-102
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• 2005

Organic solvents are widely used in biotransformation systems. There are many efforts to reduce the consumption of organic solvents because of their toxicity to the environment and human health. In recent years, several groups have started to explore novel organic solvents called room temperature ionic liquids in order to substitute conventional organic solvents. In this work, lipase-catalyzed transesterification in several uni- and bi-phasic systems was studied. Two representative hydrophobic ionic liquids based on 1-butyl-3-methylimidazolum coupled with hexafluorophosphate ([BMIM][$PF_6$]) and bis[{trifluoromethylsulfonyl} imide] ([BMIM] [$Tf_{2}N$]) were employed as reaction media for the transesterification of n-butanol. The commercial lipase, Novozym 435, was used for the transesterification reaction with vinyl acetate as an acyl donor. The conversion yield was increased around $10\%$ in a water/[BMIM][$Tf_{2}N$] bi-phasic system compared with that in a water/hexane system. A higher distribution of substrates into the water phase is believed to enhance the conversion yield in a water/[BMIM][$Tf_{2}N$] system. Partition coefficients of the substrates in the water/[BMIM][$Tf_{2}N$] bi-phasic system were higher than three times that found in the water/hexane system, while n-butyl acetate showed a similar distribution in both systems. Thus, RTILs appear to be a promising substitute of organic solvents in some biotransformation systems.

• 한국미생물·생명공학회지
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• 제15권2호
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• pp.122-128
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• 1987

Candida rugosa와 Rhizopus arrhizus 리파제를 photocrosslinkable resin prepolymer에 고정화시켜서 이소옥탄을 유기용매로 사용한 이상계를 이용해서 유지분해 및 에스테르교환 반응을 보고자했다. Dioctylsulfosuccinate가 가장 좋은 surfactant였다. 소수성 젤인 ENTP-3000에 고정된 리파제가 좋은 활성을 나타냈고 친수성 젤인 ENT-4000에 고정된 리파제가 유기용매에 대해 안정했다. 고정화 matrix의 소수성이 증가될수록Vm(app)는 증가되었으나 Km(app)는 거의 일정했다. 리파제의 최적 pH는 소수성 젤인 ENTP-3000에 고정된 경우 C. rugosa와 R. arrhizus 리파제에 대해서 각각 6.0과 6.5였으나, 친수성 젤에 고정된 리파제는 짧은 시간 반응에는 pH에 크게 영향을 받지 않았으나 긴 시간 동안 반응시킬 때는 역시 pH6.0과 6.5에서 각각 C. rugosa와 R. arrhizus 리파제가 높은 양의 지방산을 분해시켰다. 리파제를 entrapment 시키면 열안정성이 증가됨을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제35권6호
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• pp.1659-1664
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• 2014

A porous metal-organic framework (MOF), MIL-101, was synthesized in the presence of sulfated zirconia (SZ) to produce acidic SZ/MIL-101 composites for the first time. The composites were characterized with XRD, nitrogen adsorption, FT-IR, scanning electron microscope, chemical analysis and so on. The composites (SZ/MIL-101s) were successfully applied in a liquid-phase esterification for a high yield of ester. This catalytic result of SZ/MIL-101, compared with that of pure SZ or MIL-101 (showing a negligible yield of ester), suggests that the SZ in the composite is highly active in the acid catalysis probably because of the well-dispersed active species of SZ. Moreover, the esterification is catalyzed in heterogeneous mode as confirmed by negligible esterification after filtration of the catalyst. Finally, microwaves can be efficiently applied both in the synthesis of the composites and the esterification reaction to accelerate the two processes of synthesis and esterification by about 5 times.

• 한국식품과학회지
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• 제17권6호
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• pp.490-494
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• 1985

물에 녹지않는 기질을 사용할 수 있고, 다시 효소를 회수하여 다음에 사용하고자 할때 효소와 기질등 과의 분리등 여러 가지 장점이 있는 2상계(이상계(二相界))를 사용하여 Rhizopus arrhizus의 리파제에 의한 에스테르 교환반응을 위한 기본 실험으로써 물에 녹지 않는 각종 유기용매 중에서 이 반응을 위한 가장 좋은 유기용매를 고르고자 유기용매가 리파제의 안정도와 활성도에 미치는 영향을 보았다. 이실험에서 사용된 유기용매는 n-hexane, n-heptane, n-octane, isooctane, cyclohexane등 5개의 탄화수소와 doethylether, diisopropylether, di-n-butylether등 3개의 에테르이다. 실험 결과 diiso-propylether와 isooctane 이 다른 유기용매에 비해 월등히 2상계를 이용한 에스테르 교환 반응에 좋은 용매임을 알았다.

• Journal of Microbiology and Biotechnology
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• 제4권3호
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• pp.204-209
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• 1994

The synthesis of N-(benzyloxycarbonyl)-L-aspartyl-L-phenylalanine methylester (Z-APM), a precursor of aspartame, from N-(benzyloxycarbonyl)-L-aspartic acid (Z-Asp) and L-phenylalanine methylester hydrochlolide($L-PM\cdot HCI$) was investigated in a saturated-ethylacetate single phase system using immobilized thermolysin. Among the various supports tested, glyceryl-CPG was found to be most efficient for retaining enzyme activity. The enzyme immobilized onto glyceryl-CPG also showed the highest activity for Z-APM synthesis in saturated ethyl acetate. Z-APM conversion yield in saturated ethylacetate was half of that obtained in an ethyl acetate-buffer two-phase system under the same reaction conditions. However, as the mole ratio of $L-PM \cdot HCI$ to Z-Asp was increased to 4.0, the conversion yield reached 95 %. When continuous synthesis of Z-APM was canied out in a plug flow reactor (PFR) with 80 mM of L-PMㆍHCI and 20 mM of Z-Asp in saturated ethylacetate (pH 5.5), more than 95 % of Z-Asp was converted to Z-APM with a space velocity of 1.16 $hr^{-1} at 40^{\circ}C$. Although the operational stability in PFR was reduced rapidly, more than 80% of initial activity was maintained in CSTR even after a week of operation.

• 한국막학회:학술대회논문집
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• 한국막학회 2003년도 The 4th Korea-Italy Workshop
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• pp.65-68
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• 2003

The paper discusses the use of stable emulsion, prepared by membrane emulsification technology, to improve the enantiocatalytic performance of immobilised lipase in multiphasic membrane reactors. The production of optical pure (S)-naproxen from racemic naproxen methyl ester has been used as model reaction system. The enzyme was immobilised in the sponge layer (shell side) of capillary polyamide membrane with 50 kDa cut-off, The O/W emulsion, containing the substrate in the organic dispersed phase, was fed to the enzyme membrane reactor from shell-to-lumen. The results evidenced that lipase maintained stable activity during all the operation time (more than 250 hours), showing an enantiomeric excess (96 $\pm$2%) comparable to the free enzyme (98 $\pm$ 1%) and much higher compared to similar lipase-loaded membrane reactors used in two-separate phase systems (90%). The study showed that immobilised enzymes can achieve high stability as well as high catalytic activity and enantioselectivity.

• 한국미생물·생명공학회지
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• 제16권3호
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• pp.250-258
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• 1988

리파제는 모노, 디, 트리글리세리드 분자 내의 에스테르 결합을 가수분해 시키는 효소로 잘 알려져 있다. 그런데, 이 효소의 기질인 유지는 물에 용해되지 않아 그 반응이 불균일계에서 일어남으로 리파제 반응의 반응속도론적 해석이 곤란하였다. 이러한 성질은 유지공업에서 리파제를 산업적 촉매로 사용하는데 커다란 장해 요인이 되었었다. 그러나, 최근에 이상계, 역미셀계, 미수계와 같이 반응매질로 유기용매를 도입한 효소반응계가 개발됨에 따라 리파제를 이용한 유지의 전환에 대한 관심이 집중하는 추세에 있다. 리파제를 사용하여 유지를 가수분해시킴으로써 지방간을 생산하고자 할 때 효소반응계로 재래식의 에멀젼보다 이상계 또는 역미셀계를 사용하면 생산성, 굳기름의 가수분해 속도, 생성물 분리등의 측면에서 전체 공정의 효율이 향상될 수 있었다. 한편, 미수계에서 리파제는 에멀젼에서는 불가능한 에스테르 교환반응, 글리세리드 합성, aminolysis, thiotransesterification 및 oximolysis 같은 반응을 촉매 할 수 있는 획기적인 특성을 나타냈다. 공업적 측면에서 이 반응계는 물리적 또는 화학적 특성 (특히 융점)이 변형된 유지를 생산하고자 하는 에스테르 교환반응의 효소반응계로 널리 이용되고 있다. 앞으로 유기용매 내에서 효소의 안정성을 확보할 수 있는 수단 및 연속조작이 가능한 효소반응기의 개발에 관한 연구가 계속된다면 이러한 효소공정이 공업적 제조기술로 발전될 수 있을 것이다.