• KSBB Journal
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• v.10 no.1
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• pp.9-14
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• 1995

Continuous production of fructooligosaccharides from sucrose by a dual immobilized enzyme system of fructosyltransferase and glucose isomerase was studied in a column reactor. The optimal temperature and pH of the immobilized fructosyltransferase were $65^{\circ}C$ and 5.5, respectively. The activity of glucose isomerase was favorable as temperature and pH were increased within the ranges examined. However, both the immobilized enzymes were thermally unstable over $5^{\circ}C$, suggesting that long-term operation of the dual immobilized enzyme column should be carried out below $50^{\circ}C$. The optimum packing ratio of fructosyltransferase to glucose isomerase was found to be around 5/3. Under the optimized reaction conditions, the dual enzyme column was successfully operated for 40 days without any loss of initial enzyme activities, yielding 66% of fructooligosaccharides. Furthermore, the relative sweetness of fructooligosaccharides produced by a dual emzyme system was enhanced by 6% compared with that of fructosyltransferase alone.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 1979.10a
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• pp.244.2-244
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• 1979

고분자 기질을 분해하는 효소의 고정화 후의 활성 yield을 높히고자 Polysaccharide의 표면에 acrylamide 및 N-hydroxysuccinimidyl acrylate을 graft 공중합 시킴으로써 긴 측쇄에 활성 ester을 가지는 새로운 carrier에 phosphiesterase을 고정화 시켰으며 이 고정화된 phosphodiesterase의 몇가지 성질을 조사하여 본래의 phosphiesterase의 성질과 비교하였다. 1) 이 Carrier에 phosphodiesterase을 직접 고정화시킨 결과 52%가 고정화되었으며 고정화된 효소는 38%의 비활성을 나타내 주었다. 2) phosphodiesterase는 이상과 같이 고정화됨으로써 최적작용 pH는 8.0부근에서 9.0부근으로 최적작용온도는 $50^{\circ}C부근에서$ $60^{\circ}C부근으로$ KM치는 1.11mg에서 2.1mg/ml로 변하였으며 열안정성은 훨씬 증가하여 본래의 phosphodiesterase의 열불활성속도상수가 0.4인데 고정화된 효소는 0.03 이었다. 또 $5^{\circ}C에서$ 수용액상태(pH 8.0 Tris buffer)로 6개월 보관후의 관존 활성은 본래의 효소가 0.2%인데 고정화된 효소는 42%로 높은 치를 나타내주었다.

• KSBB Journal
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• v.13 no.2
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• pp.147-154
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• 1998

Enzymatic hydrolysis using an immobilized enzyme was carried out to produce chitosan oligosaccharides (COSs) from chitosan effectively. Chitosanase was immobilized on eight different carriers by physical adsorption. The enzyme immobilized on chitin had higher activity than those immobilized on the other carriers in spite of its lower adsorption. The activity of chitin-immobilized enzyme was more than 90% of the original activity. Optimal temperature of the immobilized enzyme increased by about $15^{\circ}C$ and its thermostability was excellent in relatively wide range of temperature. But its effects of pH did not improve compared to the free enzyme. The immobilized enzyme produced 153 mg/g chitosan of the reducing sugar for 3hrs of hydrolytic incubation time. The total content of higher oligomers, tetramer to hexamer, among amount of total COSs obtained for 2hrs was more than 90%. In kinetic parameters for both enzymes, immobilized enzyme showed lower affinity for substrate and reaction rate than free enzyme, however, no reduction of the rate for high substrate concentrations. Consequently, chitin-immobilized could effectively hydrolyse chitosan and produce the higher COSs without activity decrease in comparison with the free enzyme.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1935-1937
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• 2003

최근 콜레스테롤 센서는 전극 상에 효소를 고정화 하는 방식을 이용하여 센서의 집적도를 높이는 시도가 이루어지고 있다. 이러한 전극 상의 효소고정화 방식으로 entrapment, cross liking, covalently binding 등이 있다. 본 논문에서는 이러한 효소 고정화 방식-전도성 고분자인 P3MT를 사용하여 entrap시키는 방법과 silanization을 이용한 covalent bonding 시키는 방법-에 따른 전기화학 센서의 감도 특성에 관한 연구를 수행하였다. 전도성 고분자를 사용한 고정화 방법은 cyclic voltammograms으로 scan rate 10 mA/s, potential 0.5-1.3V의 조건하에서 P3MT를 Polymerization하고, 효소 고정화를 위해 chromoampermeter로 potential 0.6V에서 900초 동안 수행하였다. silanization을 이용한 covalent bonding 시키는 방법은 nitric acid로 Pt 전극표면을 산화시키고, APTER로 silanization 공정을 시행하였다. 효소 고정화를 위해 전해질로는 0.1M Phosphate buffer solution을 사용하여 cyclic voltammograms으로 scan rate 50 mA/s 전위 0.0-0.7V의 조건 하에서 수행하였다. 이 결과 전도성 고분자를 이용한 고정화 방법에서의 senstivity가 0.89 ${\mu}A/mM{\cdot}cm^2$이고, silanization을 이용한 효소 고정화 방법에서는 1.51 ${\mu}A/mM{\cdot}cm^2$였다. 이처럼 후자의 방법에서 더 좋은 감도 특성이 나타났다. 따라서, silanization을 이용한 고정화 방법이 센서 제작 방식으로 더 적합하다고 사료된다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.251.1-251.1
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• 2010

바이오디젤은 동식물성 기름과 메탄올의 트랜스에스테르화 반응에 의해 생산되는 지방산메틸에스테르(FAME, fatty acid methyl esters)로서, 트랜스에스테르화 공정에는 KOH, NaOH, $NaOCH_3$등의 균질계 화학촉매를 이용한 방법, 무촉매 공정인 초임계 메탄올 이용 방법, 그리고 효소촉매를 이용한 방법이 있다. 초임계 공정은 에너지 소비와 장치비가 커서 경제성이 떨어지는 것으로 보고되며 화학촉매 공정은 반응 효율이 높다는 장점을 가지고 있지만, 반응 및 정제단계가 복잡하고 정제과정에 폐수를 발생시키는 문제점을 가지고 있다. 고정화 효소를 사용하는 효소 공정은 에너지 비용의 절감, 후 처리 공정의 단순화, 고 순도의 글리세롤을 얻을 수 있는 장점이 있지만, 반응 속도가 느리고 효소 가격이 비싸다는 단점이 있어 현재까지 상업화되지 못하고 있다. 반응속도가 높고 재사용이 가능한 효소 촉매 공정 개발을 위해 본 연구에서는 Candida rugosa, Rizhopus oryzae 2종을 실리카에 동시 고정화하였다. 고정화 Lipase의 제조는 실리카겔을 과산화수소를 이용하여 전처리를 하고 Acetone과 3-APTES의 혼합용액을 첨가한 후 실리카겔과 (silanization)을 진행 하였다. 그리고 glutaraldehyde를 첨가 하여 공유 결합을 형성 한 후에 증류수를 사용하여 실리카겔을 회수하여 lipase(Rizhopus oryzae, Candida rugosa 10% 용액)를 고정화 하였다. 고정화 효소의 효소 활성을 측정한 결과 3000-3500 Unit(${\mu}mol/g{\cdot}min$)으로 측정되었다. 제조된 고정화 효소를 이용하여 Canola Oil을 바이오디젤로 전환하는 실험을 진행하였으며 생성물로부터 고정화 효소를 분리한 후에 상층의 에스테르층을 취하여 수세한 뒤 원심분리하여 FAME 함량을 측정한 결과 83%의 바이오디젤을 얻을 수 있었다. 그리고 효소 촉매 트랜스에스테르화 반응의 Enzyme, Water, Methanol 투입량의 반응 변수들에 대하여 반응표면분석법(Response Surface Methodology)을 적용하여 최적 반응조건을 도출하는 연구를 수행하였다.

• Applied Biological Chemistry
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• v.35 no.5
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• pp.410-414
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• 1992

Endoinulase from Streptomyces sp. S56 was immobilized by adsorption on DEAE-cellulose in 0.01 M citrate-sodium phosphate buffer, pH 6.0 and the properties of immobilized and free enzymes were investigated. The immobilized enzyme preparation, having 40 inulase activity units per dried matrix, revealed the maximal activity at $pH\;4.5{\sim}5.5$ and $55{\sim}60^{\circ}C$ and were most stable at pH 6 and 45^{\circ}C$. The immobilization caused a drop in optimum pH and affinity toward inulin, a slight increase in optimum temperature, an important increase in thermal stability and maximum reaction velocity. The immobilized endoinulase hydrolyzed the tuber extract of jerusalem artichoke and inulin, mainly into fructose and inulobise, degrading 63 and 78% of the total sugar respectively, within 48 hrs in batch reactor.

• Journal of Life Science
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• v.20 no.11
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• pp.1656-1661
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• 2010

Alkaline protease for the hydrolysis of egg yolk protein was immobilized on five carriers - Duolite A568, Celite R640, Dowex-1, Dowex 50W and Silica gel R60. Duolite A568 showed a maximum immobilization yield of 24.7%. Optimum pH for the free and immobilized enzyme was pH 8 and 9, respectively. However, no change was observed in optimum temperature ($50^{\circ}C$). Thermal stability was observed in immobilized enzymes compared to free enzymes. The immobilized enzyme retained 86% activity after 10 cycle operations in a repeated batch process. The effect of flow rate on the stability of enzyme activity in continuous packed-bed reactor was investigated. Lowering flow rate increased the stability of the immobilized enzyme. After 96 hr of continuous operation in a packed-bed reactor, the immobilized enzyme retained 83 and 61% activity when casein and egg yolk were used as a raw materials, respectively.

• Korean Journal of Food Science and Technology
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• v.11 no.3
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• pp.192-199
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• 1979

With cells of Streptomyces spp K-45 isolated from soil, the immobilization of glucose isomerase by a series of treatments ; heat, carefully manipulated drying, extrusion with a thickening agent, and glutaraldehyde-induced crosslinking, was presented. This was aimed to obtain a mechanically stable form of whole cell containing glucose isomerase. The resulted pellet form had a good mechanical strength, compared with a commercial product, and showed 26 % of the activity recovery. The specific activity was 48.1 units per g of the dry material. The immobilized glucose isomerase generally showed properties similar to those of the soluble enzyme ; optimal pH at $7.5{\sim}9.0$, optimal temperature at $80{\sim}85^{\circ}C$, activation energy of 10.9 kcal/mole, and $K_m$ for glucose of 10.9M. The immobilized enzyme was very thermostable and pH stable.

• KSBB Journal
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• v.8 no.4
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• pp.313-319
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• 1993

Methyl fructoside was synthesized from sucrose and methanol using an immobilized invertase. The enzyme was covalently bound by glutaraldehyde on porous silica coated with polyethyleneimine to give loading capacity of 120mg of invertase per one gram of dry porous silica and effective activity of 100U per one milligram of bound invertase. Polyethyleneimine coating imparted a hydrophillic character, good activity retention and high loading capacity to the surface of porous silica as well as hydrophillic microenviroment in the vicinity of bound invertase. The immobilized enzyme was formed into an alginate-enclosed silica bead to have enough activity for methyl fructoside synthesis from aqueous methanol-sucrose solution. Using the alginate-enclosed biocatalyst the yield of methyl fructoside was obtained as high as 55.9% from aqueous 30% (v/v) methanol and 0.291mo1/l sucrose with 2U/ml activity at $25^{\circ}C$, pH 4.8.

• Journal of Life Science
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• v.23 no.11
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• pp.1365-1370
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• 2013

Immobilized cellulase on weak ion exchange resin showed a typical Langmuir adsorption isotherm. Immobilized cellulase had better stability with respect to pH and temperature than free cellulase. Kinetics of thermal inactivation on free and immobilized cellulase followed first order rate, and immobilized cellulase had a longer half-life than free cellulase. The initial rate method was used to characterize the kinetic parameters of free and immobilized enzyme. The Michaelis-Menten constant $K_m$ was higher for the immobilized enzyme than it was for the free enzyme. The effect of the recirculation rate on cellulose degradation was studied in a recycling packed-bed reactor. In a continuous packed-bed reactor, the increasing flow rate of cellulose decreased the conversion efficiency of cellulose at different input lactose concentrations. Continuous operation for five days was conducted to investigate the stability of long term operation. The retained activity of the immobilized enzymes was 48% after seven days of operation.