• 한국동물학회지
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• 제32권2호
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• pp.134-141
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• 1989

본 연구는 온열처리에 의한 세포치사의 mechqnism을 밝히기 위해서 heat sensitizer인 low pH와 heat protector인 glycerol을 이용하여 cell lethlity와 단백질의 분해 kinetics를 검토한 것이다. 41-45도씨의 온열처리 중에서 41도씨를 제외한 전 온도범위에서 sensitizer와 protector의 효과가 뚜렷이 나타났으며, protector이 효과는 cell lethality와 단백질분해 모두에서 sensitizer의 효과에 비해서 현저히 나타나서 sensitizer와 protector의 작용기작은 서로 다를 것으로 생각되었다. 즉, 43-44도씨에서 cell inactivation energy는 정상, low pH, glycerol 상태에서 각각 239, 190, 317 kcal/mole의 값을 보였다. 단백질분해 kinetics의 경우에도 대체적인 경향성은 cell inactivation kinetics와 유사하였으나, 직접적인 연관성은 발견할 수 없었다. 이와 같은 결과로 미루어 볼 때, cell lethality와 단백질 분해의 mechanism 사이에 직접적인 관계는 없고, 주로 막단백질로 추정되는 단백질의 inactivation에 의한 세포내 환경의 변화에 의해서 2차적으로 세포치사가 일어나는 것으로 추정할 수 있으며, 정확한 mechanism을 밝히기 위해서는 DNA polymerase를 비롯한 몇가지 가능한 표적에 대한 연구가 이루어져야 할 것으로 사료된다.

• BMB Reports
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• 제31권3호
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• pp.258-263
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• 1998

Acetolactate synthase (ALS) is the common enzyme in the biosynthetic pathways leading to leucine, valine, and isoleucine. Tobacco ALS was expressed in E. coli and purified to homogeneity. The recombinant tobacco ALS was inactivated by thiol-specific reagents, N-ethylmaleimide (NEM) and 5,5'-dithio-bis-(2-nitrobenzoic acid) (DTNB). Inactivation of the ALS by NEM followed pseudo-first order kinetics and was first order with respect to the modifier. The substrate pyruvate protected the enzyme against the inactivation by NEM and DTNB. Extrapolation to complete inactivation of the enzyme by DTNB showed modification of approximately 2 out of 4 total cysteinyl residues (or 2 cysteinyl and 1 cysteinyl residues), with approximately 1 residue protected by pyruvate. The tobacco ALS was also inactivated by the tryptophanspecific reagent, N-bromosuccinimide (NBS), and was similarly protected by pyruvate. The kinetics of the inactivation was first-order with respect to NBS. The present data suggest that cysteinyl and tryptophanyl residues play a key role in the catalytic function of the enzyme.

• 한국미생물·생명공학회지
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• 제25권2호
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• pp.173-177
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• 1997

Glycerol-3-phosphate cytidylyltransferase from Bacillus subtilis was modified with various chemical modifiers to determine the active sites of the enzyme. Treatment of the enzyme with group-specific reagents diethylpyrocarbonate, N-bromosuccinimide, or carbodiimide resulted in complete loss of enzyme activity, which shows histidine, tryptophan, and glutamic acid or aspartic acid residues are at or near the active site. In each case, inactivation followed pseudo first-order kinetics. Inclusion of glycerol-3-phosphate and/or CTP prevented the inactivation, indicating the presence of tryptophan and glutamic acid or aspartic acid residues at the substrate binding site. Analysis of kinetics of inactivation showed that the loss of enzyme activity was due to modification of a two histidine residues, single tryptophan residue, and two glutamic acid or aspartic acid residues.

• 상하수도학회지
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• 제33권5호
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• pp.379-388
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• 2019

Chlorination and UV illumination are being widely applied to inactivate a number of pathogenic microbials in the environment. Here, we evaluated the inactivation efficiency of individual and combined treatments of chlorination and UV under various aqueous conditions. UV dosage was required higher in waste water than in phosphate buffer to achieve the similar disinfecting efficiency. Free chlorine generated by electrolysis of waste water was abundant enough to inactivate microbials. Based on these, hybrid system composed of sequential treatment of electrolysis-mediated chlorination and UV treatment was developed under waste water conditions. Compared to individual treatments, hybrid system inactivated bacteria (i.e., E. coli and S. typhimurium) and viruses (i.e., MS-2 bacteriophage, rotavirus, and norovirus) more efficiently. The hybrid system also mitigated the photo re-pair of UV-driven DNA damages of target bacteria. The combined results suggested the hybrid system would achieve high inactivation efficiency and safety on various pathogenic microbials in wastewater.

• 한국축산식품학회지
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• 제29권3호
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• pp.310-316
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• 2009

In this study, the influence of pressure assisted mild thermal inactivation (PAMTI) on E. coli ATCC 10536 was examined at 200 MPa and temperature range of $20-50^{\circ}C$. Inactivation rate significantly increased (p<0.05) as temperature and time increased at 200 MPa. The maximum inactivation (7.91 log reduction) was obtained at $50^{\circ}C$ for 30 min under 200 MPa, which meant the complete inactivation of E. coli ATCC 10536. Inactivation kinetics were evaluated with the first order inactivation rate (k), activation energy ($E_a$), thermal death time (TDT), and z value. Kinetic parameters were significantly (p<0.05) influenced by variation temperature of PAMTI. In this study, the synergistic effect of pressure and temperature were found in the inactivation of E. coli ATCC 10536 through PAMTI.

• BMB Reports
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• 제30권2호
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• pp.113-118
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• 1997

Aspartase from Hafnia alvei was inactivated by N-ethylmaleimide (NEM) and 5,5' -Dithiobis-(2-znitrobenzoic acid) (DTNB) following pseudo-first order kinetics. Their apparent reaction orders were 0.83 and 0.50 for NEM and DTNB modifications, respectively, indicating that inactivation was due to a sulfhydryl group in the active site of aspartase and participation of the sulfhydryl group in an essential step in the catalytic reaction. When aspartase was modified by DTNB, the enzyme activity was restored by dithiothreitol treatment, indicating that cysteine residuetsl islarel possibly at or near the active site. The pH-dependence of the inactivation rate by NEM suggested that an amino acid residue having pK value of 8.3 was involved in the inactivation. When aspartase was incubated with NEM and L-aspartate together, L-aspartate markedly protected the enzyme from inactivation by NEM, but the other reagents used did not.

• Applied Microscopy
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• 제11권1호
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• pp.29-38
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• 1981

Bacteriophage f2 were treated with ozone at various concentrations for 20 minutes. The inactivation kinetics of f2 phage were examined during ozonation. In order to study the mode of action of ozone on the phage f2, absorption of the phage to the host pili was meassured by utilyzing radioactivity of tritium incorporated into the phage RNA. Sucrose density gradient analysis and electron microscopy were also used to prove the mechanism of ozone inactivation of the phage. Strucural proteins of the phage were broken by ozonation into many protein subunits. The extent of phage breakage was proportional to ozone concentration and reaction time. Percent decrease of the phage absorption to the host pili was coincident with the rate of ozone inactivation of the phage. Ozone inactivation of bacteriophage f2 was shown to be caused by the breakage of the structural protein and blockage of the phage absorption to the host pili.

• 한국식품영양학회지
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• 제34권1호
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• pp.26-35
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• 2021

Myrosinases (thioglucosidases) catalyze the hydrolysis of a class of compounds called glucosinolates, of which the aglycones show various biological functions. It is often necessary to minimize the loss of myrosinase activity during thermal processing of cruciferous vegetables. Myrosinase was isolated from a popular spice, white mustard (Sinapis alba), and its thermal inactivation kinetics was investigated. The enzyme was extracted from white mustard seeds and purified by a sequential processes of ammonium sulfate fractionation, Concanavalin A-Sepharose column chromatography, and gel permeation chromatography. At least three isozymes were revealed by Concanavalin A-Sepharose column chromatography. The purity of the major myrosinase was examined by native polyacrylamide gel electrophoresis and on-gel activity staining with methyl red. The molecular weight of the major enzyme was estimated to be 171 kDa. When the consecutive step model was used for the thermal inactivation of the major myrosinase, its inactivation energy was 44.388 kJ/mol for the early stage of destruction and 32.019 kJ/mol for the late stage of destruction. When the distinct two enzymes model was used, the inactivation energy was 77.772 kJ/mol for the labile enzyme and 95.145 kJ/mol for the stable enzyme. The thermal inactivation energies lie within energy range causing nutrient destruction on heating.

• 산업식품공학
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• 제13권2호
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• pp.122-129
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• 2009

자외선 살균소독기의 유효성을 검정하기 위하여 스테인리스스틸 컵 바닥에서 E. coli를 대상으로 살균력을 측정하고 살균패턴을 조사하였다. 스테인리스스틸 컵 바닥의 자외선 강도는 컵의 위치에 따라 큰 차이를 보였다. 중앙부에 놓인 컵의 바닥에서는 높은 자외선 강도를 보인 반면 외곽으로 갈수록 자외선 강도는 급격하게 약화되었으며, 이러한 편차는 상단 선반에서 가장 심하였고 중단 및 하단선반으로 갈수록 완화되었다. E. coli를 대상으로 한 스테인리스스틸 컵 바닥에서 살균효과는 컵 바닥의 자외선 강도와 살균시간에 비례하였다. 자외선에 의한 E. coli 살균패턴은 tailing을 수반하는 의사 1차반응으로 나타났으며 각 구간의 살균속도상수를 산출한 결과 초기 살균속도상수 ($K_{1}$)는 위치에 따라 큰 차이를 보인 반면 후기 살균속도상수($K_{2}$)는 위치에 따른 차이가 크지 않았다. 현장에서 자외선 살균소독기를 용이하게 사용할 수 있도록 일정 살균치를 얻는데 필요한 자외선 조사시간을 산출하는 방정식을 제시하였다.

• 산업식품공학
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• 제14권3호
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• pp.202-207
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• 2010

저온에서 미생물을 사멸시킬 수 있는 비열살균기술로 감압 플라즈마를 활용하고자 생성기체별 감압 플라즈마 특성을 비교하고 Escherichia coli 살균효과를 조사하였다. 1 Torr이하로 감압시킨 상태에서 공기, 산소, 질소를 350 mL/min으로 공급하며 플라즈마를 발생시킨 결과 아크발생 없이 균일한 플라즈마가 생성되었다. 감압 플라즈마에 의한 온도 상승은 5분 처리 시 ${10^{\circ}C}$ 내외, 10분 처리 시 ${25^{\circ}C}$ 미만이었으며, 기체 종류별로는 공기, 산소, 질소 순으로 상승도가 낮았다. 감압 플라즈마 5분간 처리로 E. coli는 5 log 이상 감소하였으며, 이후 감소율이 둔화되어 10분간 처리 후 6-7 log 정도의 감소를 보였다. 감압 플라즈마에 의한 E. coli 살균패턴은 살균속도가 높은 초기와 낮은 후기로 구분되는 2단계 1차 반응으로 확인되었으며, 초기 살균속도상수($k_{1}$)는 공기, 산소, 질소 순으로 감소하였다. 감압 공기플라즈마 살균의 작은 D값 또한 식품 표면의 오염도를 낮추기 위한 비열살균기술로서의 가능성을 제시하였다.