Development of an experimental apparatus and protocol for determining antimicrobial activities of gaseous plant essential oils

Seo, H.S.,Beuchat, L.R.,Kim, H.,Ryu, J.H. Elsevier Science Publishers 2015 International journal of food microbiology Vol.215 No.-

There is a growing interest in the use of naturally-occurring antimicrobial agents such as plant essential oils (EOs) to inhibit the growth of hazardous and spoilage microorganisms in foods. Gaseous EOs (EO gases) have many potential applications in the food industry, including use as antimicrobial agents in food packaging materials and sanitizing agents for foods and food-contact surfaces, and in food processing environments. Despite the potentially beneficial applications of EO gases, there is no standard method to evaluate their antimicrobial activities. Thus, the present study was aimed at developing an experimental apparatus and protocol to determine the minimal inhibitory concentration (MIC) and minimal lethal concentration (MLC) of EO gases against microorganisms. A sealed experimental apparatus was constructed for simultaneous evaluation of antimicrobial activities of EO gases at different concentrations without creating concentration gradients. A differential medium was then evaluated in which a color change allowed for the determination of growth of glucose-fermenting microorganisms. Lastly, an experimental protocol for the assessment of MIC and MLC values of EO gases was developed, and these values were determined for 31 EO gases against Escherichia coli O157:H7 as a model bacterium. Results showed that cinnamon bark EO gas had the lowest MIC (0.0391μl/ml), followed by thyme-thymol EO gas (0.0781μl/ml), oregano EO gas (0.3125μl/ml), peppermint EO gas (0.6250μl/ml), and thyme-linalool EO gas (0.6250μl/ml). The order of the MLC values of the EO gases against the E. coli O157:H7 was thyme-thymol (0.0781μl/ml)<cinnamon bark (0.1563μl/ml)<oregano (0.3125μl/ml)<peppermint (0.6250μl/ml)=thyme-linalool (0.6250μl/ml). The experimental apparatus and protocol enable rapid and accurate determination of the MIC and MLC values of EO gases and perhaps other types of gaseous antimicrobial agents.

Combined effects of chlorine dioxide, drying, and dry heat treatments in inactivating microorganisms on radish seeds

Bang, J.,Kim, H.,Kim, H.,Beuchat, L.R.,Ryu, J.H. Academic Press 2011 FOOD MICROBIOLOGY Vol.28 No.1

We determined the combined effectiveness of ClO<SUB>2</SUB> (200 and 500 μg/ml, 5 min), air drying [25 <SUP>o</SUP>C, 40% relative humidity (RH), 2 h], and mild dry heat (55 <SUP>o</SUP>C, 23% RH, up to 48 h) treatments in killing total aerobic bacteria (TAB), Escherichia coli O157:H7, and molds and yeasts (MY) on radish seeds. A 5.1-log reduction in the number of TAB was achieved on radish seeds treated with 200 or 500 μg/ml ClO<SUB>2</SUB> followed by air drying for 2 h and dry heat treatment for 48 h or 24 h, respectively. When radish seeds were treated with 200 and 500 μg/ml ClO<SUB>2</SUB>, air dried, and heat treated for 12 h and 6 h, respectively, the initial population of E. coli O157:H7 (5.6 log CFU/g) on seeds was reduced to an undetectable level (<0.8 log CFU/g). However, the pathogen was detected in 5-day-old sprouts. The reduction of MY (1.2-1.0 log CFU/g) on radish seeds under similar experimental conditions was not changed significantly during subsequent heat treatment up to 48 h. Results show that treating radish seeds with 500 μg/ml ClO<SUB>2</SUB>, followed by air dried at 25 <SUP>o</SUP>C for 2 h and heat treatment at 55 <SUP>o</SUP>C for 36 h achieved a >5-log CFU/g reduction of TAB and E. coli O157:H7. These observations will be useful when developing effective strategies and practices to enhance the microbiological safety of radish sprouts.

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>

Interaction of copper(II) with N-substituted bis(2-pyridylmethyl)amine derivatives

Kim, M.,Mora, C.,Lee, Y.H.,Clegg, J.K.,Lindoy, L.F.,Min, K.S.,Thuery, P.,Kim, Y. Elsevier 2010 Inorganic chemistry communications Vol.13 No.10

<P>Interaction of copper(II) with the N-substituted bis(2-pyridylmethyl)amine derivatives, (R)-N-1,N-1-bis (pyridine-2-ylmethyl)butane-1,2-diamine (L-1) and (R)-2-(bis(pyridin-2-ylmethyl)amino)butan-1-ol (L-2), has led to isolation of optically active [Cu(L-1)Cl]PF6 (1) and [Cu(L-2)Cl]ClO4 (2), respectively. The X-ray structures of (1) and (2) show that the copper is bound to all four heteroatoms of the respective ligands as well as to a chlorine atom in a distorted square pyramidal arrangement in which the three nitrogens of L-1 or L-2 occupy three positions of each basal plane while the fourth position is occupied by the chloro ligand; apical sites in each case are filled by the amine donor from the NH2-substituted butane arm in L-1 or the (protonated) alcohol oxygen of the 2-aminobutane-1-ol substituent in L-2. To a first approximation the coordination geometry in 2 is distorted square pyramidal; however, the remaining (axial) site on each copper centre is involved in a long contact (2.96 angstrom) with a bound chloro ligand from an adjacent complex which connects individual complex units in a zigzag 1-D polymeric chain, so that the coordination geometry could also be seen as pseudo-octahedral. A temperature-dependent magnetic study revealed the presence of ferromagnetic exchange coupling between copper centres in the chain reflecting the orthogonal structure between the chloro-bridged copper(II) ions; in contrast, and as expected, the discrete complex 1 is magnetically dilute. (C) 2010 Elsevier B.V. All rights reserved.</P>

Hybrid architecture of rhodium oxide nanofibers and ruthenium oxide nanowires for electrocatalysts

Kim, Y.L.,Ha, Y.,Lee, N.S.,Kim, J.G.,Baik, J.M.,Lee, C.,Yoon, K.,Lee, Y.,Kim, M.H. Elsevier Sequoia 2016 JOURNAL OF ALLOYS AND COMPOUNDS Vol.663 No.-

We report the synthesis and electrochemical performances of the hybrid architecture of rhodium oxide (Rh<SUB>2</SUB>O<SUB>3</SUB>) nanofibers (NF) and highly single crystalline RuO<SUB>2</SUB> nanowires (NW) by combining the electrospinning process and a simple recrystallization process. The amorphous Ru(OH)<SUB>3</SUB>.xH<SUB>2</SUB>O precursors at relatively low temperature were efficiently transformed into highly single crystalline RuO<SUB>2</SUB> nanowires with the tetragonal rutile structure on electrospun Rh<SUB>2</SUB>O<SUB>3</SUB> nanofibers. Pure Rh<SUB>2</SUB>O<SUB>3</SUB> NF and hybrid RuO<SUB>2</SUB> NW-Rh<SUB>2</SUB>O<SUB>3</SUB> NF exhibited different electroactivities toward H<SUB>2</SUB>O<SUB>2</SUB> electrochemical reaction: Rh<SUB>2</SUB>O<SUB>3</SUB> NF facilitates the H<SUB>2</SUB>O<SUB>2</SUB> oxidation vs. hybrid RuO<SUB>2</SUB> NW-Rh<SUB>2</SUB>O<SUB>3</SUB> NF promotes H<SUB>2</SUB>O<SUB>2</SUB> reduction more favorably. The H<SUB>2</SUB>O<SUB>2</SUB> reduction free from O<SUB>2</SUB> reduction interference at RuO<SUB>2</SUB> NW-Rh<SUB>2</SUB>O<SUB>3</SUB> NF is advantageous and finds the feasibility for selective H<SUB>2</SUB>O<SUB>2</SUB> detection in various samples. Furthermore, RuO<SUB>2</SUB> NW-Rh<SUB>2</SUB>O<SUB>3</SUB> NF generated a greatly higher current induced by H<SUB>2</SUB>O<SUB>2</SUB> reduction (i.e., enhanced sensitivity to H<SUB>2</SUB>O<SUB>2</SUB>) than bare Rh<SUB>2</SUB>O<SUB>3</SUB> NF.

Pathway analysis of genome‐wide association datasets of personality traits

Kim, H.‐,N.,Kim, B.‐,H.,Cho, J.,Ryu, S.,Shin, H.,Sung, J.,Shin, C.,Cho, N. H.,Sung, Y. A.,Choi, B.‐,O.,Kim, H.‐,L. Blackwell Publishing Ltd 2015 Genes, brain, and behavior Vol.14 No.4

<P><B>Abstract</B></P><P>Although several genome‐wide association (GWA) studies of human personality have been recently published, genetic variants that are highly associated with certain personality traits remain unknown, due to difficulty reproducing results. To further investigate these genetic variants, we assessed biological pathways using GWA datasets. Pathway analysis using GWA data was performed on 1089 Korean women whose personality traits were measured with the Revised NEO Personality Inventory for the 5‐factor model of personality. A total of 1042 pathways containing 8297 genes were included in our study. Of these, 14 pathways were highly enriched with association signals that were validated in 1490 independent samples. These pathways include association of: Neuroticism with axon guidance [L1 cell adhesion molecule (L1CAM) interactions]; Extraversion with neuronal system and voltage‐gated potassium channels; Agreeableness with L1CAM interaction, neurotransmitter receptor binding and downstream transmission in postsynaptic cells; and Conscientiousness with the interferon‐gamma and platelet‐derived growth factor receptor beta polypeptide pathways. Several genes that contribute to top‐ranked pathways in this study were previously identified in GWA studies or by pathway analysis in schizophrenia or other neuropsychiatric disorders. Here we report the first pathway analysis of all five personality traits. Importantly, our analysis identified novel pathways that contribute to understanding the etiology of personality traits.</P>

The Histone Modification Domain of Paf1 Complex Subunit Rtf1 Directly Stimulates H2B Ubiquitylation through an Interaction with Rad6

Van Oss, S. Branden,Shirra, Margaret K.,Bataille, Alain R.,Wier, Adam D.,Yen, Kuangyu,Vinayachandran, Vinesh,Byeon, In-Ja L.,Cucinotta, Christine E.,Hé,roux, Annie,Jeon, Jongcheol,Kim, Jaehoon,V Elsevier 2016 Molecular cell Vol.64 No.4

<P><B>Summary</B></P> <P>The five-subunit yeast Paf1 complex (Paf1C) regulates all stages of transcription and is critical for the monoubiquitylation of histone H2B (H2Bub), a modification that broadly influences chromatin structure and eukaryotic transcription. Here, we show that the histone modification domain (HMD) of Paf1C subunit Rtf1 directly interacts with the ubiquitin conjugase Rad6 and stimulates H2Bub independently of transcription. We present the crystal structure of the Rtf1 HMD and use site-specific, in vivo crosslinking to identify a conserved Rad6 interaction surface. Utilizing ChIP-exo analysis, we define the localization patterns of the H2Bub machinery at high resolution and demonstrate the importance of Paf1C in targeting the Rtf1 HMD, and thereby H2Bub, to its appropriate genomic locations. Finally, we observe HMD-dependent stimulation of H2Bub in a transcription-free, reconstituted in vitro system. Taken together, our results argue for an active role for Paf1C in promoting H2Bub and ensuring its proper localization in vivo.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Histone modification domain (HMD) of Rtf1 directly contacts Rad6 in vivo </LI> <LI> HMD structure and in vivo crosslinking identify a conserved Rad6 interaction surface </LI> <LI> Paf1C regulates global H2B ubiquitylation (ub) patterns by linking HMD to Pol II </LI> <LI> HMD stimulates Bre1-dependent H2Bub in a transcription-free, reconstituted assay </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>

Effect of dietary lactulose supplementation on growth performance, nutrient digestibility, meat quality, relative organ weight, and excreta microflora in broilers

Zhao, P.Y.,Li, H.L.,Mohammadi, M.,Kim, I.H. Elsevier 2016 Poultry science Vol.95 No.1

<P>A 35 d trial was conducted to evaluate the effects of dietary lactulose on growth performance, nutrient digestibility, meat quality, relative organ weight, and excreta microflora in broilers. A total of 816 1-day-old male Ross broilers (40.2 +/- 0.4 g) were allotted to 4 dietary treatments using 12 cages with 17 chicks per cage. Treatments were: 1) CON, basal diet; 2) L05, CON + 0.05% lactulose; 3) L10, CON + 0.10% lactulose; and 4) L15, CON + 0.15% lactulose. Higher (P < 0.05) body weight gain (BWG) and lower (P < 0.05) feed conversion ratio (FCR) were observed in broilers fed the L15 diet compared with those fed the CON diet during d 22 to 35. During d 0 to 35, BWG was higher (P < 0.05) and FCR was lower (P < 0.05) in broilers fed lactulose diets than those fed the CON diet. Additionally, broilers fed L15 diets had the highest BWG (P < 0.05) and lowest FCR (P < 0.05). The apparent total tract digestibility (ATTD) of DM and nitrogen (N) was increased (P < 0.05) in broilers fed the L15 diet compared with those fed the CON diet. Drip loss was decreased (P < 0.05) in L10 and L15 treatments compared with CON treatment on d 1, d 3, and d 5. On d 3, lowest (P < 0.05) drip loss was observed in the L15 treatment. Excreta E. coli counts in the L15 treatment were decreased (P < 0.05) on d 14, but Lactobacillus counts in the L15 treatment were increased (P < 0.05) on d 14 and d 35 compared with the CON diet. A linear effect (P < 0.05) was observed on BWG (d 22 to 35), FCR (d 0 to 35), the ATTD of DM and N, drip loss, E. coli (d 14), and Lactobacillus (d 14 and d 35) counts. In conclusion, dietary supplementation of 0.15% lactulose can improve growth performance and nutrient digestibility; as well as increase the proliferation of Lactobacillus and decrease E. coli counts in excreta.</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>

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>