• Journal of Microbiology and Biotechnology
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• v.17 no.2
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• pp.244-252
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• 2007

Escherichia coli has a PhoR-PhoB two-component regulatory system to detect and respond to the changes of environmental phosphate concentration. For the E. coli W3110 strain growing under phosphate-limiting condition, the changes of global gene expression levels were investigated by using DNA microarray analysis. The expression levels of some genes that are involved in phosphate metabolism were increased as phosphate became limited, whereas those of the genes involved in ribosomal protein or amino acid metabolism were decreased, owing to the stationary phase response. The upregulated genes could be divided into temporarily and permanently inducible genes by phosphate starvation. At the peak point showing the highest expression levels of the phoB and phoR genes under phosphate-limiting condition, the phoB- and/or phoR-dependent regulatory mechanisms were investigated in detail by comparing the gene expression levels among the wild-type and phoB and/or phoR mutant strains. Overall, the phoB mutation was epistatic over the phoR mutation. It was found that PhoBR and PhoB were responsible for the upregulation of the phosphonate or glycerol phosphate metabolism and high-affinity phosphate transport system, respectively. These results show the complex regulation by the PhoR-PhoB two-component regulatory system in E. coli.

• The Korean Journal of Food And Nutrition
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• v.10 no.2
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• pp.174-179
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• 1997

The antimicrobial and GTase(Glucosyltransferase) inhibition activity were investigated for solvent fractions of Gall-nut, variety of fork drugs and Red-grape husk water extracts. Among them, Gall-nut and Red-grape husk water extracts were selected for the powerful antimicrobial and GTase inhibition activity. The methanol fractions of Gall-nut and Red-grape husk were showed very powerful antimicrobial activity on both B. subtilis and E. coli. The MIC(Minimum Inhibitory Concentration) of gall-nut methanol fraction were 1.0mg/ml for B. subtilis and 3.0mg/ml for E. coli. Red-grape husk were 2.0mg/ml for B. subtilis and 3.0mg/ml for E. coli. The methanol fractions of Gall-nut and Red-grape husk were showed very powerful Gtase inhibition activity. The concentrations of these fractions for 80% inhibition of GTase activity were 1.08$\times$10-3mg/ml and 1.08$\times$10-2mg/ml, respectively. The principal compound for the antimicrobial and GTase inhibition activity in tese extracts seems to be polyphenol derivatives.

• Asian-Australasian Journal of Animal Sciences
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• v.25 no.12
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• pp.1742-1747
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• 2012

A total of 96 growing pigs ((Landrace${\times}$Yorkshire)${\times}$Duroc; BW = $26.58{\pm}1.41$ kg) were used in a 6-wk feeding trail to evaluate the effects of fermented chlorella (FC) supplementation on growth performance, nutrient digestibility, blood characteristics, fecal microbial and fecal noxious gas content in growing pigs. Pigs were randomly allotted into 1 of 4 dietary treatments with 6 replicate pens (2 barrows and 2 gilts) per treatment. Dietary treatments were: i) negative control (NC), basal diet (without antibiotics); ii) positive control (PC), NC+0.05% tylosin; iii) (fermented chlorella 01) FC01, NC+0.1% FC, and iv) fermented chlorella 02 (FC02), NC+0.2% FC. In this study, feeding pigs PC or FC01 diets led to a higher average daily gain (ADG) and dry matter (DM) digestibility than those fed NC diet (p<0.05), whereas the inclusion of FC02 diet did not affect the ADG and DM compared with the NC group. No difference (p>0.05) was observed on the body weight, average daily feed intake (ADFI), gain:feed (G:F) ratio, the apparent total tract digestibility of N and energy throughout the experiment. The inclusion of PC or FC did not affect the blood characteristics (p>0.05). Moreover, dietary FC treatment led to a higher (p<0.05) lactobacillus concentration and lower E. coli concentration than the NC treatment, whereas the antibiotic supplementation only decreased the E. coli concentration. Pigs fed FC or PC diet had reduced (p<0.05) fecal $NH_3$ and $H_2S$ content compared with those fed NC diet. In conclusion, our results indicated that the inclusion of FC01 treatment could improve the growth performance, nutrient digestibility, fecal microbial shedding (lower E. coli and higher lactobacillus), and decrease the fecal noxious gas emission in growing pigs when compared with the group fed the basal diet. In conclusion, dietary FC could be considered as a good source of supplementation in growing pigs because of its growth promoting effect.

• Journal of the East Asian Society of Dietary Life
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• v.10 no.2
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• pp.160-169
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• 2000

This study was conducted to understand the inhibitory garlic and ginger against the growth of food born pathogenic bacteria. Juice was prepared from the raw spices by using an electric homogenizer and membrane filter. Dry-powdered spices were treated with double distilled water and 70% ethanol to extract the antibacterial substances, respectively. Growth inhibitory effects of juice and extracts of the spices were monitored by using bacterial strains such as B. subtilis, L. moncytogenes, S. aureus,E. coli O157 : H7, P. aeruginosa, and S. typhimurium. On a solid medium where E. coli and S. aureus cells were grown, ginger juice formed inhibitory zone at the concentrations of 2-10% by paper disc test. The Bone formed by ginger juice was wider and more transparent than that formed by garlic juice on the same concentration.1. monocytogenes and B. subtilis were more sensitive to garlic juice than others, and stopped growing at 2% garlic juice. Ginger juice showed the growth inhibition by 30-50% at 1.0% concentration. On the contrast, P. aeruginosa which resisted to the garlic juice was the most sensitive to ginger juice. Water extract of garlic was not effective to inhibit the bacterial growth, while 2% ginger extract completely inhibited the growth of E. coli and S. aureus. Alcohol extract of ginger inhibited the growth of bacteria at the concentration of 0.3%. This growth inhibition is almost 10 times lower than that of the garlic extract. It was clear that ginger had more potential than garlic as an inhibitor to control the growth of the indicator organisms.

• KSBB Journal
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• v.18 no.5
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• pp.404-407
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• 2003

Two recombinant Escherichia coli strains, GCSC6576 harboring a plasmid pSYL107 containing the Ralstonia eutropha polyhydroxyalkanoate (PHA) biosynthesis genes and a fadR atoC mutant LS5218 harboring a plasmid pJC4 containing the Alcaligenes latus PHA biosynthesis genes were compared for their ability to synthesize poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV) from whey. The 3HV fraction could be increased by acetic acid induction and oleic acid supplementation in flask cultures of recombinant E. coli GCSC6576. With the pH-stat fed-batch culture of recombinant E. coli LS5218, we obtained a cell concentration, a P(3HB-co-3HV) concentration, a P(3HB-co-3HV) content, and a 3HV fraction of 31.8 g/L, 10.6 g/L, 33.4%, and 6.26 mol%, respectively in 39 h.

• Journal of Food Hygiene and Safety
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• v.13 no.2
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• pp.112-120
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• 1998

This study was performed to investigate the synergistic effect of chitosan and sorbic acid as a new food preservative. So it was performed to investigate inhibitory effect on growh of E. coli 0157:H7, gram negative pathogenic food borne disease bacteria and of S. aureus, gram positive food borne disease bacteria in chitosan, sorbic acid and combination of chitosan and sorbic acid. Minimun Inhibitory Concentration (MIC) of chitosan in E. coli 0157:H7 was 500 ppm at pH 5.0, 250 ppm at pH 5.5, 500 ppm at pH 6.0, and 2000 ppm at pH 6.5, while in Staph. aureus 31.25 ppm at pH 5.0 and 62. 5 ppm at more than pH 5.5. also, MIC of sorbic acid in E. coli 0157:H7 was 500 ppm at pH 5.0, 1500 ppm at pH 5.5, and 2000 ppm at more than pH 6.0, while in Staph. aureus 1500 ppm at pH 5.0 and more than 2000 ppm at more than pH 5.5. Due to the effect of pH in E. coli 0157:H7, MIC of combined chitosan and sorbic acid was 500 ppm of chitosan with 500 ppm of sorbic acid at pH 6.5, but 250 ppm of chitosan with 31.3 ppm of sorbic acid at pH 5.0. In Staph. aureus, there was great effect of chitosan, but neither effect of pH nor sorbic acid. When E. coli 0157:H7 were treated with 500 ppm of chitosan with 500 ppm of sorbic acid and 250 ppm of chitosan with 250 ppm of sorbic acid at pH 6.5, they were inhibited. But, they were increased at the initial concentration of bacteria at 1000 ppm of chitosan in 18 hours, at 500 ppm of chitosan in 36 hours. There was no effect of growth inhibition with sorbic acid but great effect with chitosan on Staph. aureus. The correl~tions between MICs of chitosan and sorbic acid in E. coli 0157:H7 accoding to pH were higher than those in Staph. aureus. R values in E. coli 0157:H7 were 0.95 (p<0.01), 0.99 (p<0.01), 0.97 (p<0.01), and 0.99 (p<0.01) at pH 6.5, 6.0, 5.5, and 5.0 respectively. The synergistic effect of chitosan and sorbic acid in E. coli 0157:H7 could be confirmed from the result of this experiment. Therefore, it was expected that the food preservation would increase or maintain by using sorble acid together with chitosan, natural food additive that did no harm to human body.

• Journal of Dairy Science and Biotechnology
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• v.41 no.2
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• pp.76-85
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• 2023

This study investigated the effect of the addition of pomegranate concentrate to yogurt on the growth of pathogenic and lactic acid bacteria. The concentration of the MRS broth was adjusted to one-half and used for an experiment. Pomegranate concentrate was added at concentrations of 4%, 2%, 1%, and 0.5%, which significantly promoted the growth of Lacto-coccus cremoris, Weissella cibaria, Weissella paramesenteroides, Lactobacillus plantarum, Lactobacillus acidophilus, Streptococcus thermophillus, Lactobacillus bulgaricus, and Lactobacillus lactis. The growth of lactic acid bacteria increased with higher concentrations of pomegranate. However, the addition of pomegranate concentrate inhibited the growth of Escherichia coli KCCM11587, E. coli KCCM11591, E. coli KCCM11596, and E. coliKCCM11600. Yogurt with added pomegranate concentrate demonstrated optimal conditions compared to that of the control without the addition. Particularly, the viable cell count of lactic acid bacteria was significantly higher in the yogurt with pomegranate concentrate. Furthermore, the viability of the lactic acid bacteria in the yogurt with pomegranate concentrate was higher than that of the control without the addition of concentrate during storage.

• Journal of Food Hygiene and Safety
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• v.38 no.1
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• pp.31-36
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• 2023

This study was conducted to evaluate the efficacy of sodium hypochlorite in eliminating Escherichia coli strains from leafy green and stem vegetables, which are frequently sold at community service centers. A cocktail of non-pathogenic E. coli and enterohaemorrhagic E. coli (E. coli O157:H7) was used to artificially contaminate the vegetables (initial numbers of bacteria 7-8 log CFU/g). The contaminated vegetables were soaked in sodium hypochlorite for 5 min and then washed three times with running water. After the treatment, number of viable bacterial cells on the vegetables was estimated. Sodium hypochlorite treatment reduced the E. coli population by 1-2 log CFU/g on leafy green and stem vegetables, a significant reduction from the initial number. Further, sodium hypochlorite showed better antimicrobial efficacy for leaves with a larger surface area, less roughness, and softness. There was no significant difference in the antimicrobial effect between 100 and 200 mg/kg of sodium hypochlorite. Therefore, it is not necessary to increase sodium hypochlorite concentration than the level suggested in the school meal hygiene management guidelines. However, sodium hypochlorite treatment is not sufficient to achieve a safe level of microorganisms on leafy green and stem vegetables since they generally have a high abundance of microorganisms on their surface. Thus, an alternative cooking method for fresh leafy green and stem vegetables in summer should be developed to ensure they are safe for consumption.

• Microbiology and Biotechnology Letters
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• v.32 no.4
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• pp.341-346
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• 2004

The quantification of the toxicological effects of the heavy metals such as Cu, Cd, Cr, Hg, and Zn on the growth of Escherichia coli was performed, and the variations of toxicwith exposure time were evaluated in adaptation procedure. The characteristics of growth inhibition on Escherichia coli by heavy metals were different with metal species, and critical concentration of each metal, which inhibited cell growth completely, were Cu of 3.5 mM, Zn of 2.5 mM, Cd of 1.5 mM, Cr of 1.2 mM, and Hg of 0.12 mM, respectively. The tolerance of E. coli against heavy metals, based on $EC_{50}$ values, increased in order of Cu > Zn > Cr > Cd > Hg. The slopes obtained from the relationship between ECso values and expose time corresponds to adaptability of test organisms to the toxicants. The adaptability of test organisms to the toxicants was much higher at higher slope values. Adaptability of E. coli on heavy metals increased in order to Zn > Cd > CU >> Cr> Hg.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.5
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• pp.425-431
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• 2006

The development of fermentation conditions for the production of C595 diabody fragment (dbFv) in E. coli HB2151 clone has been explored. Investigations were carried out to study the effect of carbon supplements over the expression period, the comparison of C595 dbfv production in synthetic and complex media, the influence of acetic acid upon antibody production, and comparison of one-stage and two-stage processes operated at batch or fed-batch modes in bioreactor. Yeast extract supplied during expression yielded more antibody fragment than any other carbon supply. The synthetic medium presented higher specific productivity (0.066 mg dbFv $g^{-1}$ dry cell weight) when compared to the complex medium (0.044 mg dbFv $g^{-1}$ DCW). The comparison of fermentation strategies demonstrated that (1) one-stage fed-batch fermentation performed higher C595 dbFv production than that operated in batch mode which was significantly affected by acetate concentration; (2) a two-stage batch operation could enhance C595 dbFv production. It was found that a concentration of 12.3 mg $L^{-1}$ broth of C595 dbFv and a cell concentration of 10.8g $L^{-1}$ broth were achieved at the end of two-stage operation in 5-L fermentation.