Growth of Clostridium perfringens spores inoculated in sous-vide processed Korean traditional Galbijjim under different storage conditions

To evaluate the microbiological safety of Korean traditional seasoned beef processed by sous-vide method, Clostridium perfringens spores were inoculated into the samples, and then germination and growth of spores were observed under different temperatures for days. Also, changes in pH, water activity, and salt contents were analyzed. As the results, there was no difference in water activity and pH of the samples during the storage at any temperature. However, salt contents of the samples significantly increased as storage time increased, and the storage temperature affected the change of salt contents. C. perfringens did not grow at 4 and 10°C for 24 days however, the bacterial growth was observed at 20°C after 2 days of storage. Based on these simulation tests, the microbiological safety of sous-vide processed galbijjim can be guaranteed at 4 and 10°C for 24 days even though the raw materials were contaminated by C. perfringens spores.     

Bioinformatics and its role in the study of the evolution and probiotic potential of lactic acid bacteria

Food Science and Biotechnology - Due to their numerous well-established applications in the food industry, there have been many studies regarding the adaptation and evolution of lactic acid...     

Fabrication of color electronic paper display by using the charged particles

We fabricated a color electronic paper display (EPD) by using the charged particles. The display has 160 (xRGBW) x 480 array of pixels and four inch diagonal viewing area. Color filter technology was applied for coloration of the EPD. The fabrication process was as follows. First, ITO electrodes were patterned on top and bottom substrates. Ribs were formed to define pixels on the bottom substrate, and color filters were deposited on the ITO of top substrate. The charged particles were put into the pixel arrays defined by the ribs. Finally, the top substrate having the color filters was assembled on the bottom substrate. The resolution was 160 (xRGBW) x 480 with 4 x 4 inch area. The color gamut was about 2.49%, and the response time was 0.25 msec at 90 V. The contrast ratio was 2.36. The color EPD successfully demonstrated to display some images.     

Expression and purification of a fusion-typed pediocin PA-1 in Escherichia coli and recovery of biologically active pediocin PA-1

Pediocin PA-1 is a representative class IIa bacteriocin which is small and heat-stable and has a consensus motif, -YGNGV-. The plasmid pQE40PED, encoding pediocin PA-1 fused with His-tagged mouse dihydrofolate reductase (DHFR), was constructed and introduced into Escherichia coli M15 strain. The fusion protein was overexpressed in the strain after induction of isopropyl-beta-D-thiogalactopyranoside (IPTG) and purified by nickel-nitrilotriacetic acid (Ni-NTA) metal affinity chromatography. For the recovery of biologically active pediocin PA-1, the purified fusion protein was cleaved by Factor Xa protease and the liberated pediocin PA-1 was finally purified by ultrafiltration with a 75% yield. The molecular mass of the purified recombinant pediocin PA-1 was the same as that of native pediocin PA-1 on an electrophoresis gel.     

In vivo imaging of Escherichia coli and Lactococcus lactis in murine intestines using a reporter luciferase gene

A recombinant DNA, pMG36e::luc⁺ (5.3 kb), was constructed and transferred to Escherichia coli MC1061 and Lactococcus lactis MG1363 for in vivo imaging of the bacteria in murine intestines. E. coli MC1061 (pMG36e::luc⁺) and L. lactis MG1363 (pMG36e::luc⁺) displayed luciferase activities in vitro, where the bioluminescent signal of the E. coli was much stronger than that of the L. lactis by approximately 100-fold. These 2 recombinant bacteria were orally administered into rats. The bioluminescent signals of the E. coli and L. lactis in the gastrointestinal (GI) tracts of rats were detected and maintained up to 2 h via whole body imaging, indicating that the luciferase gene expression system for bacteria could be applied for in vivo imaging.     

Optimization of rapid detection of Escherichia coli O157:H7 and Listeria monocytogenes by PCR and application to field test

For rapid detection of Escherichia coli O157:H7 and Listeria monocytogenes, simple methods for sample preparation and PCR were established and applied to a field test. To improve specificity, primer sets LP43-LP44 and C(+)-D(-) were selected for E. coli O157:H7 and L. monocytogenes, respectively. Through centrifugation and partial heat treatment after enrichment, E. coli O157:H7 and L. monocytogenes were detected at 1 initial CFU without genomic DNA extraction in the culture and with artificially inoculated food samples including milk, chicken, ham, and pork. Based on the optimized PCR method, a feasibility test was carried out using randomly collected field samples. To remove false positives and false negatives, a PCR method using several primer sets, including the optimized primer set, and a standard culture method were used. With the PCR detection and standard culture methods, two pork samples were positive for L. monocytogenes after enrichment, indications that the PCR assay could be effectively used for rapid, sensitive, and species-specific detection of foodborne pathogens.     

Optimal production of fermented whey presenting bifidogenic growth stimulator activity

Various culture conditions for the production of fermented whey presenting bifidogenic growth stimulator (BGS) activity were evaluated using Leuconostoc mesenteroides CJNU 0147 and Lactobacillus casei CJNU 0588. The BGS activity of fermented whey produced with mixed culture of Leu. mesenteroides CJNU 0147 and L. Casei CJNU 0588 was higher than those of single cultures. The optimal temperature for the production of the fermented whey was 20°C. The anaerobic culture conditions via nitrogen gas supply had no influence on the BGS activity of fermented whey. The BGS activity of the heat-treated fermented whey samples was slightly decreased by 7.63, 11.66, and 15.12% at 80, 100, and 121°C, respectively for 15 min. Pilot-scale (75 L) fermented whey was produced using the 2 freeze-dried cell powders of CJNU 0147 and CJNU 0588 and spray-dried. The spray-dried fermented whey presented BGS activity, indicating it can be used as a functional food material.     

Leuconostoc mesenteroides producing bifidogenic growth stimulator via whey fermentation

Two whey culture supernatants of CJNU 0147 and CJNU 0400 were found to effectively enhance the growth of Bifidobacterium longum FI10564 by 1.58 fold compared to non-fermented whey medium. The 2 isolates were identified to be Leuconostoc mesenteroides (99% identity) by 16S rRNA gene sequence analysis. To determine whether the whey culture supernatant of CJNU 0147 selectively stimulate the growth of bifidobacteria, the growth rates of Escherichia coli DH5α, Enterococcus faecalis KFRI 675, Listeria monocytogenes ATCC 19111, and Staphylococcus aureus ATCC 14458 with the supernatant were measured. In these experiments, the supernatant slightly inhibited the growths of bacteria except for E. coli, indicating that the whey culture supernatant had very little influence on the growth of these bacterial strains.