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Staphylococcus aureus is a representative pathogenic bacterium carefully controlled in the dairy industry because it causes bovine mastitis and thus, can enter the dairy chain. Furthermore, the emergence of multi-drug resistant S. aureus is a big problem. We previously isolated a Lactococcus lactis strain producing a bacteriocin that exhibited strong antimicrobial activity against S. aureus. In this study, we investigated the synergistic inhibition of S. aureus by the bacteriocin and a bacteriophage (SAP84) which is specific to the organism. The bacteriocin (12.5–100 AU/mL) inhibited the growth of S. aureus KCTC 3881 in a dose-dependent manner, as did the bacteriophage SAP84 (0.001–1 MOI; multiplicity of infection). Co-treatment with the bacteriocin (100 AU/mL) and the bacteriophage (0.1 MOI) significantly inhibited the growth of S. aureus compared to each treatment alone (bacteriocin or bacteriophage), indicating the two components showed synergistic inhibition of S. aureus. Therefore, the bacteriocin and bacteriophage combination can be used as a good strategy for controlling pathogenic bacteria.

To reduce staphylococcal food poisoning (SFP), a phage-encoded cell wall hydrolase called endolysin has emerged as an attractive antibacterial agent. In this study, the Staphylococcus aureus infecting phage vB_SauS-SAP27 (ϕSAP27) was isolated from sewage and characterized morphologically and genetically. ϕSAP27 was identified as Siphoviridae temperate phage, with a genome of 43 kbp. A ϕSAP27 endolysin named LysSAP27 was produced recombinantly in Escherichia coli. LysSAP27 exhibited the highest activity at neutral pH and a temperature of 30 °C, and its lytic activity was upregulated by calcium ions. Following optimization of the enzymatic conditions, LysSAP27 was applied to S. aureus-contaminated milk. Treatment with 2 μM LysSAP27 led to a significant bactericidal effect, corresponding to a reduction in bacterial titer by 2.8 log CFU/mL within 1 h and 3.4 log CFU/mL within 2 h. Therefore, LysSAP27 could be used as an effective antimicrobial agent to prevent SFP in food. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10068-021-00910-2.

Foodborne Shiga toxin-producing Escherichia coli (STEC) cause severe diarrhea and hemolytic uremic syndrome (HUS) in humans. However, traditional methods for STEC sterilization are difficult to apply to fresh food. To control the pathogen, phage infecting E. coli O157:H7 were isolated and characterized. The isolated phage vB_EcoM-ECP26 had an icosahedral head and a contractile tail, and was classified as belonging to the Myoviridae family. The phage showed a broad host range against STEC and exhibited a large burst size of 1914 PFU/cell. The phage was highly stable at high temperatures (65 °C) and wide ranges of pH (4–10). The genome of vB_EcoM-ECP26 consists of 136,993 nucleotides, 214 open reading frames, and does not contain lysogenicity-related genes. Phylogenetic analysis showed that vB_EcoM-ECP26 is a V5-like species. STEC O157 growth was inhibited by vB_EcoM-ECP26 for 8 h. Furthermore, this phage not only significantly decreased the STEC population (p

Despite a great performance of Korean online game in Chinese online game market, Korean companies were faced with decreasing market positions in China from 2006. To overcome this problem, I will suggest a research model about determinant of repurchase behavior of on-line game user and moderation effect of online review. Data collected from questionnaire survey were used in empirical analysis on research hypothesis through moderated multiple regression method. There are several conclusions as such; first, perceived value and loyalty of consumer have great positive relationships with repurchase behavior. Second, online review has positive direct influence on repurchase behavior and moderation effect of relationships among them. Third, game company has great efforts to develop online games and game contents which were guaranteed before in price, quality, information, and accurate consideration of online review.

The synergy effect of trisodium phosphate (TSP) and ethanol against murine norovirus 1 (MNV-1), as a surrogate for human noroviruses, on fresh produces was evaluated. More than 2% (w/v) of TSP effectively inactivated MNV-1. The single treatment of 1% TSP or 30% ethanol for 30 min was not effective on MNV-1; however, cotreatment showed inactivation of MNV-1 on stainless steel and the produces of lettuce and bell pepper under 15 min. The results suggest that cotreatment of TSP and ethanol at a low concentration and a short time of exposure might be useful for the reduction of norovirus in some produce.

In this study, we reported the morphogenetic analysis and genome sequence by genomic analysis of the newly isolated staphylococcal phage SMSAP5 from soil of slaughterhouses for cattle. Based on transmission electron microscopy evident morphology, phage SMSAP5 belonged to the Siphoviridae family. Phage SMSAP5 had a double-stranded DNA genome with a length of 45,552 bp and 33 % G+C content. Bioinformatics analysis of the phage genome revealed 43 open reading frames. A blastn search revealed that its nucleotide sequence shared a high degree of similarity with that of the Staphylococcus phage tp310-2. In conclusion, this study is the first report to show the morphological features and the complete genome sequence of the phage SMSAP5 from soil of slaughterhouses for cattle.

Two phages of Escherichia coli O157:H7 from a sewage sample were isolated and characterized to control E. coli O157:H7 in foods. The isolated phages, BECP2 and BECP6, belonged to the Myoviridae and Podoviridae, respectively. Their burst sizes were 33 PFU/cell for BECP2 and 51 PFU/cell for BECP6 after a latent period of 25 min. Shiga toxin genes were not detected on either the BECP2 or BECP6 phage. The two phages were susceptible to 70% ethanol. To determine the utility of the two phage mixture for biocontrol of E. coli O157:H7, we analyzed the reduction of E. coli O157:H7 in commercial milk and in biofilms. The mixture reduced the growth of E. coli O157:H7 from 6 log CFU/mL to 1 log CFU/mL after 5-h incubation at 37 °C in commercial milk. The mixture was applied to E. coli O157:H7 in a biofilm formed on glass wool, microtiter plate, and stainless steel coupon. The density of E. coli O157:H7 in the biofilm reduced from OD600 1.1 to 0.6 on the plate and from 6 log CFU/coupon to 2 log CFU/coupon on the coupon. Therefore, the BECP2 and BECP6 phages might be efficient sanitizing agents for reducing E. coli O157:H7 in a biofilm environment.

In this study, we report the morphogenetic analysis and genome sequence of a new WCP30 phage of Weissella cibaria, isolated from a fermented food. Based on its morphology, as observed by transmission electron microscopy, WCP30 phage belongs to the family Siphoviridae. Genomic analysis of WCP30 phage showed that it had a 33,697-bp double-stranded DNA genome with 41.2% G+C content. Bioinformatics analysis of the genome revealed 35 open reading frames. A BLASTN search showed that WCP30 phage had low sequence similarity compared to other phages infecting lactic acid bacteria. This is the first report of the morphological features and complete genome sequence of WCP30 phage, which may be useful for controlling the fermentation of dairy foods.

To improve microbiological quality of Aster scaber during storage and distribution, hurdle technology with the sanitizers and packaging methods was used. After blanching, total aerobic bacteria of Aster scaber treated with 20% ethanol and 10% NaCl were measured at 2 log CFU/g after 6 days. Total aerobic bacteria of blanched Aster scaber at 100℃ were measured at 2 log CFU/g, and the storage at 4℃ effectively inhibited the growth of bacteria. Repeated blanching using water with added NaCl at 80℃ showed similar microbial growth inhibition compared with treatment at 100℃. After vacuum packaging, blanched sample showed 2 log CFU/g of total aerobic bacteria during 10 days (the storage at 4℃). Therefore, repeated blanching using the water with added 10% NaCl improved the microbiological quality of Aster scaber. We also found that repeated blanching after vacuum packaging was an effective way for storage and distribution of Aster scaber. In conclusion, blanching two times in the 10% salt water or in vacuum packaging at 80~100℃ would be helpful to control the microbes during storage and distribution. Key words: Aster scaber, hurdle technology, total microbe, Bacillus cereus group, lactic acid

Escherichia coli O157:H7 is an important pathogenic bacterium to humans because it produces various toxins, such as shiga-toxin. Coliphage ECP4, which belongs to the Siphoviridae family, was isolated from bovine feces to test its utility as a potential agent for the biocontrol of E. coli O157:H7. The burst size of coliphage ECP4 was about 80 PFU/cell, after a latent period of 30–35 min. Coliphage ECP4 was susceptible to temperatures above 70 °C; however, its stability was slightly reduced to 1–2 log PFU/ml after 30 min in 70% ethanol. In addition, the shiga toxin gene was not detected on coliphage ECP4. Coliphage ECP4 inhibited the growth of E. coli O157:H7 in vegetable juice, and was not detected in cabbage after 5 h. When coliphage ECP4 was applied to biofilm-formed E. coli O157:H7, E. coli O157:H7 was efficiently reduced. The newly identified coliphage ECP4 might effectively reduce E. coli O157:H7 or its biofilmed-form. Therefore, the coliphage ECP4 might be an efficient sanitizer for fresh produce contaminated with E. coli O157:H7 in the biofilm environment.

The substances of lactic acid bacteria (LAB) isolated feom Kimchi and Tarak, L. mesenteriodes LAB kw5, and S. thermophilus LAB KW15 were investigated for growth effect of Helicobacter pylori with IgY and Auricularia auricula. Inhibition of H. pylori was confirmed at LAB KW5 and KW15 supernatants. Interestingly, anti-H. pylori substance in LAB KW5 and KW15 supernatants were sensitive to lipase, but insensitive to protein hydrolase and carbohydrate hydrolase. The inhibition zone toward H. pylori was not shown with the lipase-treated supernatants. Therefore, there seemed to be lipid-like substances in the cultures. By the analyses with gas chromatography, undecanoic acid (C 11:0 ), palmitic acid (C 16:0 ), stearic acid (C 18:0 ), and oleic acid (C 18:1 ) were detected at the culture substances from L. mesenteroides LAB KW5 and S. thermophilus LAB KW15, and more eicosadienoic acid (C 20:2 ) from L. mesenteroides LAB KW5. Anti-H. pylori substances of LAB with IgY and A. auricula extract were analyzed for inhibition effect of H. pylori. The inhibition increased more by the range from 57% to 86% by the mixture. The substances with IgY and A. auricula extract showed more effective inhibition of H. pylori than single or double trials. Key words: Helicobacter pylori, lactic acid bacteria, IgY, Auricularia auricula

Food poisoning by Bacillus cereus is one of the common food-borne diseases and B. cereus is widely distributed in natural and commercial products owing to the strong resistance caused by biofilm or spore. The ethanol, NaCl, and organic acids of acetic acid, citric acid, and lactic acid for biocontrol of biofilm-forming B. cereus on glass wool were investigated. The biofilm on glass wool was observed in many developments after 48 h incubation. As the results of reduction of biofilm-forming B. cereus by sanitizers, reduction levels of each organic acid treatment ranged to 5-6 log CFU/g-glass wool. In case of combination treatments of 20% ethanol, 10% NaCl, and 1% of each organic acid for 1-5 min, the reduction level of biofilm-forming B. cereus was 7-8 log CFU/g-glass wool. Therefore, combination treatments of ethanol, NaCl, and an organic acid might effectively reduce biofilm-forming B. cereus in various food processes and industries.

To produce rapidly the traditional Kanjang soy sauce-like product with rich flavors, lactic acid bacteria of Enterococcus spp. isolated from Chungkukjang was used as one of starter cultures. Among 119 Enterococcus spp., eight strains were selected by protease-secreting activities and identified as four E. faecium, three E. faecalis, and one E. gallinarium. The strains showed low resistances toward eight antibiotics and had no resistant genes to the vancomycin. Especially, E. faecium O24 was cultivated well on 5% NaCl medium that was selected for further study as the starter. E. faecium O24 grew well on the steamed soybean and the counts increased by ten times overnight, which produced mostly 80 mg% glutamic acid and aspartic acid as the seasoning amino acids on the product. Various organic acids including principal lactic acid were also produced. Flavors of maltol and guaiacol, typical soy-sauce flavor, were produced in the mixed cultures of Zygosaccharomyces rouxii and Candida versatilis. Therefore, E. faecium O24 could be a starter of soybean fermentation for soy sauce-like product with rich flavors rapidly.Key words: soy-sauce, fermentation, Enterococcus spp., flavor, amino acid

Bacillus cereus is widely distributed on various foods and is known to cause clinical infections, food poisoning toxin induced diarrhea and vomiting. In this study, B. cereus group detected and analyzed rice, rice bran, and biofilm characterization of B. cereus confirmed. B. cereus was identified in approximately 34.6% of brown rice and 50.0% of rice bran. B. thuringiensis was detected in 3.9% of brown rice and 23% of rice bran, and B. mycoides was isolated from rice bran. The microtiter plate assay detected differences in biofilm-forming ability among B. cereus group isolates. Biofilm of B. cereus seemed to increase the MIC values of antimicrobial agent and antibiotic compounds compared with planktonic cells. Therefore, sufficient attention should be given to good manufacturing practice and good agriculture practice to avoid contamination of B. cereus group raw material including rice. Key words: Bacillus cereus group, rice, biofilm formation, antimicrobial agents † Corresponding author: Jong-Hyun Park, Dept. of Food Science and Biotechnology, Kyungwon University, Seongnam 461-701, Korea. Tel: +82- 31-750-5523, Fax: +82-31-750-5273, E-mail: p5062@kyungwon.ac.kr

Virulent Cronobacter sakazakii bacteriophage ES2 was isolated from swine fecal samples, and the genome sequence by was determined GS-Flx. Bacteriophage ES2 had a double-stranded DNA genome with a length of 22,162 bp and a G+C content of 50.08%. The morphological characteristics under a transmission electron microscope indicated that bacteriophage ES2 belongs to the family Myoviridae. The structural proteins, including the phage coat protein, were separated by SDS-PAGE and identified by Q-TOF. Bioinformatics analysis of the bacteriophage genome revealed 30 putative open reading frames (ORFs). The predicted protein products of the ORFs were determined and described. To our knowledge, the genome of the newly isolated bacteriophage ES2 was not significantly similar to that of any previously reported bacteriophages of members of the family Enterobacteriaceae.

Bacteriophages have been intensively-studied and applied in a variety of practical applications such as biocontrol of food-borne pathogens. Especially, endolysin of bacteriophage is highly specific to host strains that can hydrolyze cell wall. To get the control agent for foodpoisoning Bacillus cereus, cloning and nucleotide sequence of putative endolysin from temperate phage 250 (Tp250) of emetic B. cereus 250 were investigated. Tp250 was induced by mitomycin C and belonged to Siphoviridae family. Tp250, a circular dsDNA genome of 56,505 bp, consisted of various structural and functional genes for survival or propagation. ORFs from Tp250 were involved in replication, head morphogenesis, head-to-tail joining, tail morphogenesis, lysogenic module, host lysis, and other functional genes such as related metabolisms. For cloning of putative endolysin, Tp 250 DNA was extracted and pLYS250 was constructed. The pLYS250 had 752 ORF encoding a putative endolysin with 250 amino acids, which was expressed by around 28 kDa in Escherichia coli. Therefore, Tp250 and the endolysin might be applied as one of agents to reduce B.cereus pathogen in foods directly or through over-expression and purification.

The bacteriophage ES2 is a virus for bacterial host cells. Unlike other phages that are known for their therapeutic effects, the ES2 phage has never been clearly examined as a therapeutic agent. To systematically and conclusively evaluate its therapeutic efficacy, the expression of the surface markers CD86, CD40, and MHCII, the production of the proinflammatory cytokines IL-6, IL-1α, IL-1β, and TNF-α, and the underlying NF-κB signaling pathway in murine bone marrow-derived dendritic cells (BM-DCs) in response to ES2 phage infection were examined. The bacteriophage ES2, which was isolated from swine fecal samples an antigen, affected the expression of the cell surface molecules and proinflammatory cytokines that are associated with the DC maturation processes. Treatment with ES2 phage also led to NF-κBp65 activation and translocation to the nucleus, which indicates the activation of NF-κB signaling. Furthermore, the ES2 phage induced the promoter activity of IL-12p40. Our chromatin immunoprecipitation assay revealed that p65 was enriched at the IL12-p40 promoter as a direct target of chromatin. The present study demonstrates that the ES2 phage potently induces DC maturation via immune-enhancement processes.

Cronobacter sakazakii infection is particularly harmful to infants, and putative virulence factors of prophage origin have been identified in C. sakazakii . In this study, the phage ENT39118 was isolated from wild-type C. sakazakii ; it belongs to the family Siphoviridae . The genomic sequence of phage ENT39118 was composed of circular double-stranded DNA with a length of 39,012 bp. The sequence of ENT39118 showed weak sequence similarity to some reported regions of the prophage sequences in the C. sakazakii BAA-894 genome. To our knowledge, this is the first study of the genomic sequencing and annotation of this temperate phage, which was obtained from a C. sakazakii isolate from powdered infant formula.

Virulent phage ESP2949-1, which was isolated from sewage, has an icosahedral head, a contractile tail, and a double-stranded DNA genome with a length of 49,116 bp with 50.09% G+C content. Phage ESP2949-1 showed 3% similarity to enterobacteria phage TLS. Bioinformatics analysis of the phage genome revealed 43 putative open reading frames (ORFs). Predicted protein products of the ORFs were determined and described. Based on its morphology, phage ESP2949-1 can be classified as a member of the family Myoviridae. To our knowledge, this is the first report of the genomic sequence and characterization of phage ESP2949-1 isolated from sewage.

Bacteriophage TEM126, a newly isolated temperate phage from a mitomycin-C-induced lysate of wild-type Staphylococcus aureus isolated from food, has an isometric head, a noncontractile tail, and a double-stranded DNA genome with a length of 33,540 bp and a G+C content of 33.94%. Bioinformatics analysis of the phage genome revealed 44 putative open reading frames (ORFs). Predicted protein products of the ORFs were determined and described. Temperate phage TEM126 can be classified as a member of the family Siphoviridae by morphology and genome structure. Temperate phage TEM126 showed 84% similarity with Staphylococcus phage phiNM1. To our knowledge, this is the first report of genomic sequencing and characterization of temperate phage TEM126 from a wild-type S. aureus isolated from foods in Korea.

Cronobacter is a major food-borne pathogen in powdered infant formula and can lead to serious developmental aftereffect and death to infants. The contamination of Cronobacter may be a high risk for the powdered foods. To isolate and identify Korean Cronobacter from the powdered foods such as powdered infant formula and Saengsik, conventional culture method, rapid identification system, PCR, 16S rDNA sequencing were performed. As the results of isolation, seven Cronobacter were isolated from seven out of 102 powdered infant formulas and 41 Cronobacter were isolated from 41 out of 86 Saengsiks. Forty eight Cronobacter isolates were identified into C.sakazakii and C.dublenisis by 16s rDNA sequence analysis. Almost the isolates were C.sakazakii and 13% of the isolates were C. dublinesis. One fourth of the C.sakazakii showed different biochemical characteristics of negative nitrate reduction and non-motility activities with the other strains reported previously.

This paper considers a general design problem for a parallel processors system which consists of a set of non-homogeneous potential processors and a set of traffic distributing points. For this problem, two levels of technology choice are made: 1) which candidate processors to establish with capacity option, 2) how to allocate the incoming traffic among established processors generated at each distributing point. The associated model is formulated as a linear fractional integer program whose objective is to minimize the maximum mean queue length on any established processor, while satisfying a side constraint such as budget constraint. Within the framework of branch and bound procedure, fractional subproblems are optimized by solving a sequence of linear programming problems. Computational experience with randomly generated 25 test problems is presented.

Staphylococcus aureus strains are important foodborne pathogens that produce various toxins. To evaluate the risk of the enterotoxins, four S. aureus strains from kinbap and two clinical samples were isolated and identified, and their expression of the enterotoxin genes were analyzed using a reverse transcription real-time PCR. Various enterotoxin genes were detected, including sea, seg, seh, sei, sen, seo, and sem, where each isolate contained one or two. When the mRNA detection of the enterotoxin genes was analyzed using a reverse transcriptase PCR, various levels of expression were found depending on the species and enterotoxin gene. Therefore, it is reasonable to suggest that the poisoning risk of S. aureus can be effectively evaluated based on the gene expression at the mRNA level.

Enterococcus faecalis is an important bacterium for use as a probiotic and is an opportunistic pathogen in human beings. The antibiotic resistance acquired by E. faecalis is restricted to antibiotics used in the clinical setting. While screening for alternative antibiotics for use against multidrug-resistant E. faecalis , we isolated a virulent enterococcal bacteriophage, SAP6, belonging to the family Siphoviridae . To our knowledge, this study is the first to report the complete genome sequence of bacteriophage SAP6, which might be used as a therapeutic agent in combination with alternative antibiotics for multidrug-resistant E. faecalis .