Yong-Jin Cho

In vitro selection of Escherichia coli O157:H7-specific RNA aptamer.

Escherichia coli (E. coli) O157:H7 is a major foodborne pathogen that causes life-threatening symptoms in humans worldwide. To rapidly and properly identify the pathogen and avoid its toxic effects, ligands which can directly and specifically bind to the virulent E. coli O157:H7 serotype should be identified. In this study, a RNA aptamer-based ligand which can specifically distinguish the pathogen E. coli O157:H7 from others was developed by a subtractive cell-SELEX method. To this end, an RNA library was first incubated with the E. coli K12 strain, and the RNAs binding to the strain were discarded. The precluded RNAs were then used for the selection of O157:H7-specific aptamers. After 6 rounds of the subtractive cell-SELEX process, the selected aptamer was found to specifically bind to the O157:H7 serotype, but not to the K12 strain. This was evidenced by aptamer-immobilized ELISA, real-time PCR analysis, or an aptamer-linked precipitation experiment. Importantly, the isolated RNA aptamer that distinguishes between the virulent serotype and the nonpathogenic strain specifically bound to an O157:H7-specific lipopolysaccharide which includes the O antigen. This novel O157:H7-specific aptamer could be of potential application as a diagnostic ligand against the pathogen-related food borne illness.

Draft Genome Sequence of Staphylococcus saprophyticus subsp. saprophyticus M1-1, Isolated from the Gills of a Korean Rockfish, Sebastes schlegeli Hilgendorf, after High Hydrostatic Pressure Processing

A bacterium designated M1-1 was isolated from the gills of a Korean rockfish, Sebastes schlegeli Hilgendorf, after high hydrostatic pressure processing. Studies of 16S rRNA phylogeny and comparative genomics demonstrated that the isolate belongs to Staphylococcus saprophyticus subsp. saprophyticus. Here, we report the draft genome sequence of S. saprophyticus subsp. saprophyticus M1-1 (KACC 16562).

Enzymatic hydrolysis of anchovy fine powder at high and ambient pressure, and characterization of the hydrolyzates

BACKGROUND At specific conditions of high pressure, the stability and activity of some enzymes are reportedly known to increase. The aim of this study was to apply pressure-tolerant proteases to hydrolyzing anchovy fine powder (AFP) and to determine product characteristics of the resultant hydrolyzates. RESULTS Anchovy fine powder enzyme hydrolyzates (AFPEHs) were produced at 300 MPa and ambient pressure using combinations of Flavourzyme 500MG, Alcalase 2.4L, Marugoto E and Protamex. When the same protease combination was used for hydrolysis, the contents of total soluble solids, total water-soluble nitrogen and trichloroacetic acid-soluble nitrogen in the AFPEHs produced at 300 MPa were conspicuously higher than those in the AFPEHs produced at ambient pressure. This result and electrophoretic characteristics indicated that the high-pressure process of this study accelerates protein hydrolysis compared with the ambient-pressure counterpart. Most peptides in the hydrolyzates obtained at 300 MPa had molecular masses less than 5 kDa. Functionality, sensory characteristics and the content of total free amino acids of selected hydrolyzates were also determined. CONCLUSION The high-pressure hydrolytic process utilizing pressure-tolerant proteases was found to be an efficient method for producing protein hydrolyzates with good product characteristics.

Quantitative evaluation of resveratrol enrichment induced by UV stimulus in harvested grapes

A mathematical model was proposed to quantitatively describe resveratrol induction in harvested grapes. In the model, k1 and k2 were defined, which were the reaction rate constants for induction during direct UV irradiation and for the time-delayed induction after removing UV irradiation, respectively. During storage after UV irradiation, k2 decreased with time, whereas k1 remained constant. The portion induced by the direct irradiation effect was much more than that induced by the time-delayed effect. When UV energy of 610.2 mJ/cm2 was applied to ‘Gerbong’ grapes with an initial resveratrol content of 1.15 μg/g, their contents were 8.99 and 9.20 μg/g at day 1 and 6 during storage at 0°C, respectively. In the same situation, resveratrol content of 8.99 μg/g improved to 10.56 μg/g during storage at 20°C. This approach which enriched a health-functional compound through the modulation of metabolism after harvest might be a valueadding method for fresh food industry.