Viability of sprout seeds as affected by treatment with aqueous chlorine dioxide and dry heat, and reduction of Escherichia coli O157:H7 and Salmonella enterica on pak choi seeds by sequential treatment with chlorine dioxide, drying, and dry heat

Choi, S.,Beuchat, L.R.,Kim, H.,Ryu, J.H. Academic Press 2016 FOOD MICROBIOLOGY Vol.54 No.-

<P>Germination rates of 11 types of sprout seeds (alfalfa, broccoli, kohlrabi, kyona, mustard, pak choi, red kohlrabi, red radish, red young radish, tatsoi, and violet radish) treated with ClO2 (200 mg/ml, 5 min) or dry-heat (80 degrees C/23% relative humidity [RH], 24 h) were determined. Pak choi, red radish, and tatsoi seeds showed highest tolerance to both ClO2 and dry-heat treatments. Next, pak choi seeds were inoculated with Escherichia coli O157:H7 (5.4 log CFU/g) or Salmonella enterica (4.8 log CFU/g) and sequentially treated with ClO2 (200 mg/ml, 5 min), drying (45 degrees C/23% RH, 24 h), and dry heat (80 degrees C/23% RH, 48 h). E. coli O157:H7 was inactivated, but S. enterica was not eliminated (>3.8 log CFU/g reduction). Pak choi seeds inoculated with the pathogens were treated with ClO2, drying, and dry heat and subsequently sprouted for 5 days. When seeds were not completely decontaminated, initial populations of E. coli O157:H7 and S. enterica on seeds (<1.0 log CFU/g) increased to >5.3 and >8.4 log CFU/g of sprouts, respectively. This study shows that sequential treatments of pak choi seeds with ClO2, drying, and dry heat are effective in reducing large numbers of E. coli O157:H7 and S. enterica without loss of seed viability. (C) 2015 Elsevier Ltd. All rights reserved.</P>

Survival and colonization of <i>Escherichia coli</i> O157:H7 on spinach leaves as affected by inoculum level and carrier, temperature and relative humidity

Choi, S.,Bang, J.,Kim, H.,Beuchat, L.R.,Ryu, J.‐,H Blackwell Publishing Ltd 2011 Journal of applied microbiology Vol.111 No.6

<P><B>Abstract</B></P><P><B>Aims: </B> To determine survival and colonization of <I>Escherichia coli</I> O157:H7 on spinach leaves as affected by inoculum level and carrier, temperature and relative humidity (r.h.).</P><P><B>Methods and Results: </B> Spinach leaves were inoculated with suspensions of <I>E.?coli</I> O157:H7 in distilled water (DW) and 0·1% peptone water (PW) and incubated at 4, 12 and 25°C and 43, 85 and 100% r.h. The number of <I>E.?coli</I> O157:H7 on leaves (5·6 or 1·9 log CFU per leaf) inoculated using DW as a carrier medium increased significantly at 25°C and 100% r.h. within 120 h but remained constant or decreased significantly under other test conditions. <I>E.?coli</I> O157:H7 on leaves (5·4 log CFU per leaf) inoculated using PW as a carrier increased significantly within 72 and 24 h, respectively, at 12 or 25°C and 100% r.h.; counts using a low inoculum (2·2 log CFU per leaf) increased significantly within 24 h at 25°C.</P><P><B>Conclusions: </B> <I>Escherichia coli</I> O157:H7 can colonize on spinach leaves at 12 or 25°C in a 100% r.h. environment. Organic matter in the inoculum carrier may provide protection and nutrients which enhance survival and colonization.</P><P><B>Significance and Impact of the Study: </B> Colonization of <I>E.?coli</I> O157:H7 on spinach leaves as affected by organic matter in the inoculum, temperature and r.h. was determined. These observations will be useful when developing strategies to prevent growth of <I>E.?coli</I> O157:H7 on pre‐ and postharvest spinach.</P>

Sanitizing radish seeds by simultaneous treatments with gaseous chlorine dioxide, high relative humidity, and mild heat

Bang, J.,Choi, M.,Son, H.,Beuchat, L.R.,Kim, Y.,Kim, H.,Ryu, J.H. Elsevier Science Publishers 2016 International journal of food microbiology Vol.237 No.-

<P>Sanitizing radish seeds intended for edible sprout production was achieved by applying simultaneous treatments with gaseous chlorine dioxide (ClO2), high relative humidity (RH, 100%), and mild heat (55 degrees C). Gaseous ClO2 was produced from aqueous ClO2 (0.66 ml) by mixing sulfuric acid (5% w/v) with sodium chlorite (10 mg/mL) in a sealed container (1.8 L). Greater amounts of gaseous ClO2 were measured at 23% RH (144 ppm after 6 h) than at 100% RH (66 ppm after 6 h); however, the lethal activity of gaseous ClO2 against naturally occurring mesophilic aerobic bacteria (MAB) on radish seeds was significantly enhanced at 100% RH. For example, when exposed to gaseous ClO2 at 23% RH, the number of MAB on radish seeds decreased from 3.7 log CFU/g to 2.6 log CFU/g after 6 h. However, when exposed to gaseous ClO2 at 100% RH for 6 h, the MAB population decreased to 0.7 log CFU/g after 6 h. Gaseous ClO2 was produced in higher amounts at 55 degrees C than at 25 degrees C, but decreased more rapidly over time at 55 degrees C than at 25 degrees C. The lethal activity of gaseous ClO2 against MAB on radish seeds was greater at 55 degrees C than at 25 degrees C. When radish seeds were treated with gaseous ClO2 (peak concentration: 195 ppm) at 100% RH and 55 degrees C, MAB were reduced to populations below the detectable level (<-0.7 log CFU/g) within 2 h without decreasing the seed germination rate (97.7%). The lethality of combined treatments against artificially inoculated Escherichia coli O157:H7 was also evaluated. When exposed to gaseous ClO2 at 100% RH and 55 degrees C for 6 h, the initial number of E. coli O157:H7 (3.5 log CFU/g) on radish seeds decreased to below the detection limit (0.7 log CFU/g) by direct plating but it was not eliminated from seeds. The germination rate of radish seeds was not significantly (P> 0.05) decreased after treatment for 6 h. The information reported here will be useful when developing decontamination strategies for producing microbiologically safe radish seed sprouts. (C) 2016 Published by Elsevier B.V.</P>

국내 분리 일본뇌염 바이러스 유전자에 대한 항체생성 연구(Ⅰ) : cloning of JEV viral genes

박찬,최우영,이호동,채수림,신은진,김인범,표재환,박근용,조해월 국립보건연구원 1999 국립보건원보 Vol.36 No.-

Effects of DME mixing on number density and size properties of soot particles in counterflow non-premixed ethylene flames

최재혁,B. C. Choi,S. M. Lee,S. H. CHUNG,K. S. Jung,W. L. Jeong,S. K. Choi,S. K. Park 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.5

In order to investigate the effect of DME mixing on the number density and size of soot particles, DME was mixed in a counter flownon-premixed ethylene flame with mixture ratios of 5%, 14% and 30%. A laser extinction/scattering technique has been adopted tomeasure the volume fraction, number density, and mean size of soot particles. The experimental results showed that the highest soot concentrationswere observed for flames with mixture ratios of 5% and 14%; however, for a mixture ratio of 30% the soot concentrationdecreased. Numerical results showed that the concentrations of propargyl radicals (C3H3) at the 5% and 14% ratios were higher thanthose measured in the ethylene-based flame, and the production of benzene (C6H6) in the 5% and 14% DME mixture flames was alsoincreased. This indicates the crucial role of propargyl in benzene ring formation. These reactions generally become stronger with increasedDME mixing, except for A1 + H2 → A1 + H (-R554) and n-C4H5 + C2H2 → A1 + H (R542). Therefore, it is indicated that addingDME to ethylene flames promotes benzene ring formation. Note that although the maximum C6H6 concentration is largest in the 30%DME mixing flame, the soot volume fraction is smaller than those for the 5% and 14% mixture ratios. This is because the local C6H6concentration decreases in the relatively low temperature region in the fuel side where soot growth occurs.

Effects of the novel angiotensin II receptor type I antagonist, fimasartan on myocardial ischemia/reperfusion injury

Han, J.,Park, S.J.,Thu, V.T.,Lee, S.R.,Long, L.T.,Kim, H.K.,Kim, N.,Park, S.W.,Jeon, E.S.,Kim, E.J.,Yoon, C.H.,Cho, G.Y.,Choi, D.J. Elsevier/North-Holland Biomedical Press 2013 INTERNATIONAL JOURNAL OF CARDIOLOGY Vol.168 No.3

Background: The aim of this study was to investigate the cardioprotective effect of fimasartan, a newly developed angiotensin II receptor type I blocker (ARB), against myocardial ischemia/reperfusion (I/R) injury and to identify the mechanism by which it reduces mitochondrial damage. Methods: Fimasartan was administered intravenously to Sprague-Dawley rats (3mg/kg), cardiomyocytes (50μM), and H9c2 cells (50μM) before ischemia or hypoxia. Myocardial infarction (MI), echocardiograms, DNA fragmentation, terminal deoxynucleotidyl transferase-mediated dUTP in situ nick-end labeling, immunoblotting, oxygen consumption, confocal microscopic appearance, and L-type Ca<SUP>2+</SUP> current (I<SUB>Ca,L</SUB>) were then assessed. Results: Fimasartan pretreatment remarkably reduced the rate of MI and improved cardiac performance well after I/R (n=9/group). Fimasartan also reduced apoptotic cell death both in vivo and in hypoxia/reoxygenation (H/R)-treated H9c2 cells (n=5~8/group). H/R-induced mitochondrial O<SUB>2</SUB><SUP>-</SUP> production and collapse of membrane potential were markedly attenuated in fimasartan-treated cardiomyocytes (n=4~6/group). Additionally, mitochondrial Ca<SUP>2+</SUP> overload during reoxygenation was suppressed by fimasartan (n=4~6/group), and this was found to be possibly related to the inhibition of I<SUB>Ca,L</SUB> and mitochondrial Ca<SUP>2+</SUP> uniporter. Furthermore, fimasartan pretreatment increased phosphorylations of Akt and glycogen synthase kinase-3β (n=5~7/group), decreased pro-apoptotic p53 levels, and increased anti-apoptotic Bcl-2 levels (n=4) during reperfusion. Conclusions: Fimasartan preconditioning has the potential to modulate Bcl-2 and suppress I/R-induced Ca<SUP>2+</SUP> overload by inhibiting I<SUB>Ca,L</SUB> and MCU. These beneficial effects could prevent the mitochondrial dysfunction and apoptosis accompanied by I/R.

Effects of Addition Level and Chemical Type of Propionate Precursors in Dicarboxylic Acid Pathway on Fermentation Characteristics and Methane Production by Rumen Microbes In vitro

Li, X.Z.,Yan, C.G.,Choi, S.H.,Long, R.J.,Jin, G.L.,Song, Man K. Asian Australasian Association of Animal Productio 2009 Animal Bioscience Vol.22 No.1

Two in vitro experiments were conducted to examine the effects of propionate precursors in the dicarboxylic acid pathway on ruminal fermentatation characteristics, $CH_4$ production and degradation of feed by rumen microbes. Fumarate or malate as sodium salts (Exp. 1) or acid type (Exp. 2) were added to the culture solution (150 ml, 50% strained rumen fluid and 50% artificial saliva) to achieve final concentrations of 0, 8, 16 and 24 mM, and incubated anaerobically for 0, 1, 3, 6, 9 and 12 h at $39^{\circ}C$. For both experiments, two grams of feed consisting of 70% concentrate and 30% ground alfalfa (DM basis) were prepared in a nylon bag, and were placed in a bottle containing the culture solution. Addition of fumarate or malate in both sodium salt and acid form increased (p<0.0001) pH of culture solution at 3, 6, 9 and 12 h incubations. The pH (p<0.0001) and total volatile fatty acids (VFA, p<0.05) were enhanced by these precursors as sodium salt at 3, 6 and 9 h incubations, and pH (p<0.001) and total VFA (p<0.01) from fumarate or malate in acid form were enhanced at a late stage of fermentation (9 h and 12 h) as the addition level increased. pH was higher (p<0.001) for fumarate than for malate as sodium salt at 3 h and 6 h incubations. Propionate ($C_3$) proportion was increased (p<0.0001) but those of $C_2$ (p<0.05) and $C_4$ (p<0.01 - p<0.001) were reduced by the addition of sodium salt precursors from 3 h to 12 incubation times while both precursors in acid form enhanced (p<0.011 - p<0.0001) proportion of $C_3$ from 6h but reduced (p<0.018 - p<0.0005) $C_4$ proportion at incubation times of 1, 3, 9 and 12 h. Proportion of $C_3$ was increased (p<0.05 - p<0.0001) at all incubation times by both precursors as sodium salt while that of $C_3$ was increased (p<0.001) from 6h but $C_4$ proportion was decreased by both precursors in acid form as the addition level increased. Proportion of $C_3$ was higher (p<0.01 - p<0.001) for fumarate than malate as sodium salt from 6 h incubation but was higher for malate than fumarate in acid form at 9 h (p<0.05) and 12 h (p<0.01) incubation times. Increased levels (16 and 24 mM) of fumarate or malate as sodium salt (p<0.017) and both precursors in acid form (p<0.028) increased the total gas production, but no differences were found between precursors in both chemical types. Propionate precursors in both chemical types clearly reduced (p<0.0001 - p<0.0002) $CH_4$ production, and the reduction (p<0.001 - p<0.0001) was dose dependent as the addition level of precursors increased. The $CH_4$ generated was smaller (p<0.01 - p<0.0001) for fumarate than for malate in both chemical types. Addition of fumarate or malate as sodium type reduced (p<0.004) dry matter degradation while both precursors in both chemical types slightly increased neutral detergent fiber degradability of feed in the nylon bag.

DHS-21, a dicarbonyl/l-xylulose reductase (DCXR) ortholog, regulates longevity and reproduction in Caenorhabditis elegans

Son, L.T.,Ko, K.M.,Cho, J.H.,Singaravelu, G.,Chatterjee, I.,Choi, T.W.,Song, H.O.,Yu, J.R.,Park, B.J.,Lee, S.K.,Ahnn, J. North-Holland Pub ; Elsevier Science Ltd 2011 FEBS letters Vol.585 No.9

Dicarbonyl/l-xylulose reductase (DCXR) converts l-xylulose into xylitol, and reduces various α-dicarbonyl compounds, thus performing a dual role in carbohydrate metabolism and detoxification. In this study, we identified DHS-21 as the only DCXR ortholog in Caenorhabditis elegans. The dhs-21 gene is expressed in various tissues including the intestine, gonadal sheath cells, uterine seam (utse) cells, the spermathecal-uterus (sp-ut) valve and on the plasma membrane of spermatids. Recombinant DHS-21 was shown to convert l-xylulose to xylitol using NADPH as a cofactor. Dhs-21 null mutants of C. elegans show defects in longevity, reproduction and egg-laying. Knock-down of daf-16 and elt-2 transcription factors affected dhs-21 expression. These results suggest that DHS-21 is a bona fide DCXR of C. elegans, essential for normal life span and reproduction.

격막을 통한 물질전달시 발생되는 자연대류 : 2부 : Rayleigh 수가 큰 경우 계면대류에 대한 이론적 모델 Part 2 : Theoretical Model for Interfacial Convection at High Rayleigh Numbers

최창균,김래현,최웅 한국화학공학회 1987 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.25 No.2

Rayleigh 수가 큰 경우(5×10^7<Ra<1.5×10^(11)) 격막을 통하여 물질전달이 일어날 때 격막주위에서 발생되는 계면대류의 영향을 정량적으로 고찰하였다. 가시화를 통해 관찰된 유동양상과 전달량을 바탕으로 경계층을 단순확산층과 에디발생에 의해 교체되는 대류층으로 구분하는 전달기구 모델을 제시하였다. 또한 대류층의 유동상태는 실험에서 측정된 에디발생주기를 Rayleigh 수의 관계로 표현하고, 이를 전달 기구모델에 적용시키는 새로운 접근방법에 의해, Rayleigh 효과에 의한 자연대류시 Rayleigh 수, 유체층의 두께, 확산층 두께로 표시되는 Sherwood수의 상관관계식을 얻었다. 본 실험범위에서 확산층의 두께는 거의 일정한 값을 나타냈으며 실험치는 아래식에 의한 결과과 잘 일치하였다. Sh=0.29Ra^(0.25)-0.0671(δ_S/L) Ra^(0.5){1-exp[3.86(L/δ_s) Ra^(-0.25)]² erfc[3.86(L/δ_s) Ra^(0.25)} The effects of interfacial convection were quantitatively investigated at high Rayleigh numbers (5×10^7< Ra < 1.5×10^(11), when a solute was transferred through membrane. A theoretical model for mass transfer was suggested on the basis of the flow patterns which had been observed by shadowgraph. lt was assumed that turbulent mass transfer in the present system was controlled by two mechanisms: (1) steady state molecular diffusion in a thin layer and (2) unsteady convection of buoyant elements in its adjacent layer. The generation periods of buoyant eddies were correlated by the Rayleigh number. By relating these results with the model, a correlation for the Sherwood number was obtained as a function of the Rayleigh number, the thickness of a whole fluid layer and the thickness of a diffusion layer. The thickness of a diffusion layer was found to be almost constant. The present experimental results were well represented by the following correlation. Sh=0.29Ra^(0.25)-0.0671(δ_S/L) Ra^(0.5){1-exp[3.86(L/δ_s) Ra^(-0.25)]² erfc[3.86(L/δ_s) Ra^(0.25)}

축산폐수 2 차 침전조 유출수의 난분해성 유기물 제거를 위한 광촉매 시스템 적용과 그 반응 특성

최홍림,김진길,홍성창,안희권 한국동물자원과학회 2001 한국축산학회지 Vol.43 No.3

High CODcr concentration and brown color of the clarified effluent of piggery wastewater cause the problems for recycle or discharge of treated wastewater. Heterogeneous photocatalytic treatment was applied for complete oxidation and decolorization of the effluent which contains a large amount of non-biodegradable organics (NBOs). The CODcr, BOD, TOC and color were analyzed with processes to evaluate its performance and investigate its optimum condition for higher efficiency. The UV/TiO₂/H₂O₂slung reactor was operated in batch manner. The highest removal efficiency was obtained at the condition of pH 2, TiO₂ 1.0 wt% and H₂O₂ 300 ㎖/L. However the least-cost operation was observed at the condition of pH 4, TiO₂ 0.6 wt% and H₂O₂300 ㎖/L. The photocatalytic oxidation rate of NBOs in the biologically-treated piggery slurry followed the pseudo-first order kinetic curve. It showed the removal efficiency of color was much higher than that of CODcr and TOC of NBOs. Color removal efficiency has reached 99% after three hours since the reaction began. The CODcr and TOC concentration decreased with the exponential increase of the irradiation time and the BOD_5/CODcr ratio. The photocatalytic system can be referred to as one of potential systems to treated piggery wastewater for reuse. However further study for practical application to field should be pursued in near future.