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Chai, Changhoon,Lee, Kyung-Soo,Imm, Goo-Sang,Kim, Young Soon,Oh, Se-Wook National Research Council 2017 Canadian journal of microbiology Vol.63 No.7
<P> Inactivating Clostridium difficile spores is difficult, as they are resistant to heat, chemicals, and antimicrobials. However, this note describes inactivation of C. difficile spore outgrowth by incubation in a solution containing a germinant (1% (m/v) sodium taurocholate), co-germinants (1% (m/v) tryptose and 1% (m/v) NaCl), and natural antimicrobials (20 nmol·L<SUP>-1</SUP> nisin and 0.2 mmol·L<SUP>-1</SUP> lysozyme). Clostridium difficile spores were resistant to nisin and lysozyme but became susceptible during germination and outgrowth triggered and promoted by sodium taurocholate, tryptose, and NaCl. The degree of inactivation of germinated and outgrowing C. difficile spores by both nisin and lysozyme was greater than the sum of that by nisin and lysozyme individually, suggesting synergistic inactivation of C. difficile spores. The germinant, co-germinants, and natural antimicrobials used in this study are safe for human contact and consumption. Therefore, these findings will facilitate the development of a safe and effective method to inactivate C. difficile spore. </P>
Principle of Emulsion PCR and Its Applications in Biotechnology
Changhoon Chai 한국동물생명공학회(구 한국동물번식학회) 2019 Journal of Animal Reproduction and Biotechnology Vol.34 No.4
Emulsion polymerase chain reaction (PCR) is performed on compartmentalized DNA, allowing a large number of PCR reactions to be carried out in parallel. Emulsion PCR has unique advantages in DNA amplification. It can be applied in many molecular biological assays, especially those requiring highly sensitive and specific DNA amplification. This review discusses the principle of emulsion PCR and its applications in biotechnology. Related technologies are also discussed.
Novel Convenient Method to Determine Wettability and Dispersibility of Dairy Powders
Lee, Jeae,Chai, Changhoon,Park, Dong June,Lim, Kwangsei,Imm, Jee-Young Korean Society for Food Science of Animal Resource 2014 한국축산식품학회지 Vol.34 No.6
This study was carried out to develop a simple, convenient, and reproducible testing device to determine wettability and dispersibility of dairy powders. The testing device consists of a sieve ($150{\mu}m$) attached to a sample chamber, sensors mounted on a supporting body and a main control unit containing a display panel. The sensors detect the difference in electrical resistance between air and water. A timer is automatically triggered by the sensor when the bottom of sample-loaded chamber contacts water in the petri dish. Wettability and dispersibility of commercial skim milk powders (SMPs) produced at different heating strengths (low-, medium-, and high-heat SMP) are compared using the new testing device. Wettability of the SMPs were correlated with particle size and are found to increase in the order of medium-, low-, and high-heat SMP regardless of the amount of sample tested. Dispersibility of SMPs showed the same trend and high heat-SMP which has the smallest particle size resulted in the lowest dispersibility. Unlike existing methods, the new testing device can determine both wettability and dispersibility of powders and successfully detected differences among the samples.
Lee, So-Yeon,Kwon, Ki-Hyun,Chai, Changhoon,Oh, Se-Wook 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.2
This study was conducted to compare the growth parameters of Listeria monocytogenes between beef isolates and Type strains in raw beef. Beef was artificially inoculated with 3 Log CFU/g levels and growth was measured during storage at various temperatures ($5-25^{\circ}C$) using conventional plating methods. The $R^2$ value for lag time (${\lambda}$) and specific growth rate (${\mu}$) were determined using modified-Gompertz model, which were greater than 0.98 at all storage temperature except at $5^{\circ}C$. $B_f$, $A_f$, and RMSE showed acceptable ranges, showed that the models are suitable for the modeling the growth of L. monocytogenes. At all temperatures, the ${\lambda}$ of L. monocytogenes beef isolates was shorter than that of the L. monocytogenes Type strains, and the ${\mu}$ of beef isolates was higher than that of Type strains. These results showed that growth pattern prediction of beef inoculated with L. monocytogenes beef isolates gives more actual results than with Type strains.