• Journal of Food Hygiene and Safety
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• v.13 no.3
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• pp.294-298
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• 1998

The effect of gamma irradiation on the survival of spore bacteria was investigated in frozen cells ($-18^{\circ}C$) with 0.1 M phosphate buffer and inoculated cells in beef. In the case of the frozen cells at log phase, the radiation $D_{10}\;and\;12D_{10}$ values were 0.29 kGy and 3.48 kGy in Bacillus subtilis, 0.39 kGy and 4.68 kGy in Bacillus cereus and 0.46 kGy and 5.52 kGy in Clostridium perfrigens. And inactivation factors were 6.52~10.34 and 10.87~17.24 at the dosage of 3 kGy and 5 kGy, respectively. The radiosensitivity of inoculated cells in beef showed the $D_{10}$ value of 0.59~0.76 kGy, the $12D_{10}$ value of 7.08~9.12 kGy, and inactivation factors of 3.95~8.47. The radiosensitivity of the frozen cells was higher than that of inoculated cells in beef.

• Journal of Food Hygiene and Safety
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• v.29 no.4
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• pp.253-259
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• 2014

This study was conducted to investigate survival of Bacillus cereus (B. cereus) on stainless steel and polyvinyl chloride (PVC) and its transfer from two material to lettuce. The stainless steel and PVC were innoculated with B. cereus and stored at 6 combination conditions (temperature : $20^{\circ}C$ and $30^{\circ}C$, relative humidity (RH) : 43%, 69%, and 100%). Although the total numbers of B. cereus at RH 43% and RH 69% were reduced by 3.53-4.00 log CFU/coupon within 24 h regardless of material type, the spore numbers of B. cereus was lasted at 3.0 log CFU/coupon. When two materials were stored at $30^{\circ}C$, RH 100%, the spore numbers of B. cereus was rapidly increased by 3.0 log CFU/coupon. In addition, the reduction rate of B. cereus was decreased in the presence of organic matter. Transfer rate of B. cereus from surface of stainless steel and PVC to lettuce was increased by 10 times in the presence of water on the lettuce surface. As a result of this study, the presence of B. cereus on produce contact surfaces can increase the risk of cross-contamination. Thus, it is important that the packing table and conveyer belt in post harvest facility should be properly washed and sanitized after working to prevent cross-contamination.

• Journal of Applied Biological Chemistry
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• v.55 no.1
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• pp.13-17
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• 2012

In order to enzymatically produce chitooligosaccharide using the crude enzyme preparation from Bacillus cereus D-11, we first studied the optimal reaction conditions. It was found that the optimal temperature for hydrolysis of chitosan was $55^{\circ}C$. The ratio of enzyme/substrate should not be lower than 0.13 U/mg in the reaction mixture. The enzyme activity was stable below $50^{\circ}C$. The products of enzymatic reaction were analyzed by both thin layer chromatography and high performance liquid chromatography. Under the appropriate condition, chitosan was hydrolyzed using the enzyme preparation. The resulting chitooligosaccharides were purified and separated by Dowex ($H^+$) ion exchange chromatography. From 4 g soluble chitosan, 0.95 g $(GlcN)_2$, 1.43 g $(GlcN)_3$, and 1.18 g $(GlcN)_4$ were recovered.

• Korean Journal of Environmental Biology
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• v.29 no.1
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• pp.52-60
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• 2011

Today, the weather is changing continually, due to the progress of global warming. As the weather changes, the habitats of different organisms will change as well. It cannot be predicted whether or not the weather will change with each passing day. In particular, the biological distribution of the areas climate change affects constitutes a major factor in determining the natural state of indigenous plants; additionally, plants are constantly exposed to rhizospheric microorganisms, which are bound to be sensitive to these changes. Interest has grown in the relationship between plants and rhizopheric microorganisms. As a result of this interest we elected to research and experiment further. We researched the dominant changes that occur between plants and rhizospheric organisms due to global warming. First, we used temperature as a variable. We employed four different temperatures and four different sites: room temperature ($27^{\circ}C$), $+2^{\circ}C$, $+4^{\circ}C$, and $+6^{\circ}C$. The four different sites we used were populated by the following species: Pinus deniflora, Pinus koraiensis, Quercus acutissima, and Alnus japonica. We counted colonies of these plants and divided them. Then, using 16S rRNA analysis we identified the microorganisms. In conclusion, we identified the following genera, which were as follows: 10 species of Bacillus, 2 Enterobacter species, 4 Pseudomonas species, 1 Arthrobacter species, 1 Chryseobacterium species, and 1 Rhodococcus species. Among these genera, the dominant species in Pinus deniflora was discovered in the same genus, but a different species dominated at $33^{\circ}C$. Additionally, that of Pinus koraiensis changed in both genus and species which changed into the Chryseobacrterium genus from the Bacilus genus at $33^{\circ}C$.

• Journal of Microbiology and Biotechnology
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• v.19 no.4
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• pp.358-361
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• 2009

The purified endochitosanase(Mw 41 kDa) from bacterium Bacillus cereus D-11 hydrolyzed chitooligomers $(GlcN)_{5-7}$ into chitobiose, chitotriose, and chitotetraose as the final products. The minimal size of the oligosaccharides for enzymatic hydrolysis was a pentamer. To further investigate the cleavage pattern of this enzyme, chitooligosaccharide alcohols were prepared as substrates and the end products of hydrolysis were analyzed by TLC and HPLC. The chitosanase split $(GlcN)_4GlcNOH$ into $(GlcN)_3+(GlcN)_1GlcNOH$, and $(GlcN)_5GIcNOH$ into $(GlcN)_4+(GlcN)_1GlcNOH$ and $(GlcN)_3+(GlcN)_2GlcNOH$. The heptamer $(GlcN)_6GlcNOH$ was split into $(GlcN)_5$ [thereafter hydrolyzed again into $(GlcN_3+(GlcN)2]+(GlcN)_1GlcNOH$, $(GlcN)_4+(GlcN)_2GlcNOH$, and $(GlcN)_3+(GlcN)_3GlcNOH$, whereas $(GlcN)_{1-3}GlcNOH$ was not hydrolyzed. The monomers GlcN and GIcNOH were never detected from the enzyme reaction. These results suggest that D-11 chitosanase recognizes three glucosamine residues in the minus position and simultaneously two residues in the plus position from the cleavage point.

• Journal of Microbiology and Biotechnology
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• v.9 no.5
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• pp.619-623
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• 1999

The C-terminal starch-binding domain of Bacillus cereus $\beta$-amylase expressed in Escherichia coli was purified and crystallized using the vapor diffusion method. The crystals obtained belong to a space group of $P3_2$ 21 with cell dimensions, a=b=60.20${\AA},\; c=64.92{\AA},\; and \; \gamma = 120^{\circ}$ The structure was determined by the molecular replacement method and refined at 1.95 ${\AA}$, with R-factors of 0.181. The final model of the starch-binding domain comprised 99 amino acid residues and 108 water molecules. The starch-binding domain had a secondary structure of two 4-stranded antiparallel p-sheets similar to domain E of cyclodextrin glucanotransferase and the C-terminal starch-binding domain of glucoamylase. A comparison of the structures of these starch-binding domains revealed that the separated starch-binding domain of Bacillus cereus $\beta-Amylase$had only one starch-binding site (site 1) in contrast to two sites (site 1 and site 2) reported in the domains of cyclodextrin glucanotransferase and glucoamylase.

• Journal of Food Hygiene and Safety
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• v.24 no.3
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• pp.256-261
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• 2009

Bacillus cereus is a gram-positive spore-forming bacterium and produces an emetic or diarrheal syndrome induced by an emetic toxin and an enterotoxin, respectively. In this study, the effect of different types of media, temperature, and time on the sporulation of B. cereus, and thermal resistance of B. cereus spores produced in various temperatures were evaluated. The highest levels of spores were detected when they are produced at $25^{\circ}C$. There were no significant differences in levels of spores produced at $25^{\circ}C$ among culture media and times while levels of spores produced at $43^{\circ}C$ were significantly reduced with the increase of time. However, thermal resistance of B. cereus spores could be affected by incubation temperature. In fact, higher D-values (12.0, 10.1, and 5.9 min for 2,4, and 6 weeks, respectively) of spores produced at $43^{\circ}C$ were observed than did in samples produced at other temperatures (25 and $37^{\circ}C$). D-values of spores were 7.7, 8.2, and 12.0 min when they were produced at 25,37, and $43^{\circ}C$ for 2 weeks, respectively. The sporulation of B. cereus at $25^{\circ}C$ could result in high amounts of spores however the sporulation at $43^{\circ}C$ for 2 weeks could be effective to produce thermal resistant spores.

• The Korean Journal of Pesticide Science
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• v.13 no.4
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• pp.275-282
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• 2009

The effect of two plant growth-promoting rhizobacteria (PGPR) on plant growth and systemic protection against soft rot disease and stem rot disease of canola (Brassica napus), caused by Erwinia carotovora and Sclerotinia sclerotiorum was investigated in a laboratory and a greenhouse. Selected PGPR strains C4 and D8 were treated to canola seeds by soaking. Strains C4 and D8 significantly not only increased plant height and root length about 74% and 40.3% and also reduced disease severity of soft rot disease by 80% by C4 and D8 respectively, compared to the control. Especially strain C4 showed antifungal activity against 6 fungal pathogens, S. sclerotiorum, Rhizoctonia solani, Botrytis cinerea, Fusarium oxysporum, Phytophthora capsici and Colletotrichum acutatum. In greenhouse experiment, the seed treatment of both of them increased plant height, leaf width and leaf length of canola plant to 19.5% and 24.9%, 11.3% and 15.3%, and 14.1% and 20.7% by C4 and D8, respectively, and reduced disease severity of S. sclerotiorium. These results indicate that these two PGPR strains can decrease disease severity and increased plant growth under greenhouse condition. Therefore, these two bacteria have a potential in controlling Sclerotinia stem rot of canola. These strains have to investigate under field condition to determine their role of antibiosis, induced systemic resistance and plant growth promotion on canola.

• Food Science of Animal Resources
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• v.30 no.5
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• pp.730-738
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• 2010

We developed predictive growth models for Staphylococcus aureus and Bacillus cereus on various food matrices consisting primarily of ready-to-eat (RTE) foods. A cocktail of three S. aureus strains, producing enterotoxins A, C, and D, or a B. cereus strain, were inoculated on sliced bread, cooked rice, boiled Chinese noodles, boiled bean sprouts, tofu, baked fish, smoked chicken, and baked hamburger patties at an initial concentration of 3 log CFU/g and stored at 8, 10, 13, 17, 24, and $30^{\circ}C$. Growth kinetic parameters were determined by the Gompertz equation. The square-root and Davey models were used to determine specific growth rate and lag time values, respectively, as a function of temperature. Model performance was evaluated based on bias and accuracy factors. S. aureus and B. cereus growth were most delayed on sliced bread. Overall, S. aureus growth was significantly (p<0.05) more rapid on animal protein foods than carbohydrate-based foods and vegetable protein foods. The fastest growth of S. aureus was observed on smoked chicken. B. cereus growth was not observed at 8 and $10^{\circ}C$. B. cereus growth was significantly (p<0.05) more rapid on vegetable protein foods than on carbohydrate-based foods. The secondary models developed in this study showed suitable performance for predicting the growth of S. aureus and B. cereus on various food matrices consisting of RTE foods.

• Applied Biological Chemistry
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• v.41 no.3
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• pp.213-218
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• 1998

A bacterium with potent activity of pigment production and protease was isolated and identified as being Bacillus sp. CS-17. Cell growth, protease activity and pigment production of the strain reached to its maximum point after 24 hrs, 48 hrs, 72 hrs, respectively. The best pigment producing ability of Bacillus sp. CS-17 was shown on basal medium for pigment production added 1.0% soybean. The high effcient conditions for pigment production was obtained at culture of pH 8.5, $37^{\circ}C$ and 72 hours. Among the tested 5 gram positive strains and 6 gram negative strains, weak antibacterial activity of pigment concentrated extracts was appeared against growth of B. subtilis, P. aeruginosa, S. typhimurium, E. aerogenes, B. cereus, A. hydrophila.