Hak-Jong Choi

Influence of growth conditions on the production of a nisin-like bacteriocin by Lactococcus lactis subsp. lactis A164 isolated from kimchi.

The influence of growth parameters on the fermentative production of a nisin-like bacteriocin by Lactococcus lactis subsp. lactis A164 isolated from kimchi was studied. The bacteriocin production was greatly affected by carbon and nitrogen sources. Strain A164 produced at least 4-fold greater bacteriocin in M17 broth supplemented with lactose than other carbon sources. The amount of 3% yeast extract was found to be the optimal organic nitrogen source. While the maximum biomass was obtained at 37 degrees C, the optimal temperature for the bacteriocin production was 30 degrees C. The bacteriocin production was also affected by pH of the culture broth. The optimal pH for growth and bacteriocin production was 6.0. Although the cell growth at pH 6.0 was nearly the same level at pH 5.5 and 6.5, the greater bacteriocin activity was observed at pH 6.0. Exponential growth took place only during an initial period of the cultivation, and then linear growth was observed. Linear growth rates increased from 0.160 g(DCW) x l(-1) x h(-1) to 0.245 g(DCW) x l(-1) x h(-1) with increases in lactose concentrations from 0.5 to 3.0%. Maximum biomass was also increased from 1.88 g(DCW) x l(-1) to 4.29 g(DCW) x l(-1). However, increase in lactose concentration did not prolong the active growth phase. After 20 h cultivation, cell growth stopped regardless of lactose concentration. Production of the bacteriocin showed primary metabolic kinetics. However, bacteriocin yield based on cell mass increased greatly during the late growth phase. A maximum activity of 131x10(3) AU x ml(-1) was obtained at early stationary growth phase (20 h) during the batch fermentation in M17L broth (3.0% lactose) at 30 degrees C and pH 6.0.

Weissella kimchii sp. nov., a novel lactic acid bacterium from kimchi.

A gram-positive, catalase-negative, non-sporulating, facultatively anaerobic, short rod-shaped bacterium, with cells measuring 0.3-0.5 x 1-2 microm and designated strain CHJ3T, was isolated from partially fermented kimchi, a traditional Korean fermented vegetable food. The strain produced CO2 gas, D-lactate from glucose and dextran from sucrose and hydrolysed aesculin and arginine. It also fermented N-acetylglucosamine, amygdalin, arbutin, cellobiose, D-fructose, galactose, beta-gentiobiose, gluconate, D-glucose, maltose, D-mannose, salicin, sucrose and D-xylose. The G+C content of the DNA was 48.2 mol%. Phylogenetic analysis of 16S rRNA showed that strain CHJ3T is a member of the genus Weissella. The nearest phylogenetic relative of strain CHJ3T was Weissella confusa, with 16S rRNA similarity of 98.3%. However, strain CHJ3T could be differentiated from W. confusa on the basis of some phenotypic characteristics, analysis of whole-cell protein patterns and DNA-DNA hybridization data. These data suggest that strain CHJ3T be classified in the genus Weissella as a novel species, Weissella kimchii sp. nov. The type strain is CHJ3T (= KCCM 41287T = DSM 14295T = KCTC 3746T).

Curcumin Attenuates TNF‐α‐induced Expression of Intercellular Adhesion Molecule‐1, Vascular Cell Adhesion Molecule‐1 and Proinflammatory Cytokines in Human Endometriotic Stromal Cells

Curcumin, a naturally occurring polyphenolic compound from Curcuma longa, has long been used in folk medicine as an antiinflammatory remedy in Asian countries. Endometriosis is a chronic gynecological inflammatory disorder in which immune system deregulation may play a role in its initiation and progression. A number of mediators, including cell adhesion molecules such as intercellular adhesion molecule‐1 (ICAM‐1) and vascular cell adhesion molecule‐1 (VCAM‐1); proinflammatory cytokines such as tumour necrosis factor‐α (TNF‐α), interleukin‐1 (IL‐1), IL‐6 and IL‐8; and chemokines such as monocyte chemotactic protein‐1 (MCP‐1), play key roles in the pathogenesis of endometriosis. The aim of our study was to explore the effect of curcumin on the expression of these critical molecules in human ectopic endometriotic stromal cells isolated from women with endometriosis. Endometriotic stromal cells treated with curcumin showed marked suppression of TNF‐α‐induced mRNA expression of ICAM‐1 and VCAM‐1. Curcumin treatment also significantly decreased the TNF‐α‐induced cell surface and total protein expression of ICAM‐1 and VCAM‐1 in a dose‐dependent manner. In addition, treatment of endometriotic stromal cells with curcumin markedly inhibited TNF‐α‐induced secretion of IL‐6, IL‐8 and MCP‐1. Furthermore, curcumin inhibited the activation of transcription factor NF‐κB, a key regulator of inflammation, in human endometriotic stromal cells. These findings suggest that curcumin may have potential therapeutic uses in the prevention and treatment of endometriosis. Copyright

Enhanced nisin production by increasing genes involved in nisin Z biosynthesis in Lactococcus lactis subsp. lactis A164

AbstractNisin Z production in Lactococcus lactis subsp. lactis A164 was improved by introducing multicopy genes, nisZ, nisRK, or nisFEG, involved in nisin biosynthesis into A164 strain. A similar growth profile was obtained from all strains tested. However, the cells expressing nisRK produced 25,000 AU nisin Z ml−1 compared to 16,000 AU ml−1 by the control strain. Northern blot analysis revealed that over-expression of nisRK promoted the transcription of the nisZ gene. The A164 strain expressing multicopy nisFEG also had an increased nisin Z production (25,000 AU ml −1) but produced the nisin more slowly than the cells expressing multicopy nisRK.

Weissella cibaria WIKIM28 ameliorates atopic dermatitis-like skin lesions by inducing tolerogenic dendritic cells and regulatory T cells in BALB/c mice.

The occurrence of atopic dermatitis (AD), a chronic inflammatory skin disease, has been increasing steadily in children and adults in recent decades. In this study, we evaluated the ability of the lactic acid bacterium Weissella cibaria WIKIM28 isolated from gatkimchi, a Korean fermented vegetable preparation made from mustard leaves, to suppress the development of AD induced by 2,4-dinitrochlorobenzene in a murine model. Oral administration of W. cibaria WIKIM28 reduced AD-like skin lesions, epidermal thickening, and serum immunoglobulin E levels. Furthermore, the production of type 2 helper T (Th2) cytokines such as interleukin (IL)-4, IL-5, and IL-13 decreased in peripheral lymph node cells. Moreover, the intake of W. cibaria WIKIM28 increased the proportion of CD4+CD25+Foxp3+ regulatory T (Treg) cells in mesenteric lymph nodes (MLNs) and IL-10 levels in polyclonally stimulated MLN cells. In conclusion, the oral administration of W. cibaria WIKIM28 isolated from gatkimchi ameliorated AD-like symptoms by suppressing allergic Th2 responses and inducing Treg responses. These results suggest that W. cibaria WIKIM28 may be applicable as a probiotic for the prevention and amelioration of AD.

Occurrence of viable, red-pigmented haloarchaea in the plumage of captive flamingoes

Flamingoes (Phoenicopterus spp.) whose plumage displays elegant colors, inhabit warm regions close to the ocean throughout the world. The pink or reddish color of their plumage originates from carotenoids ingested from carotenoid-abundant food sources, since flamingoes are unable to synthesize these compounds de novo. In this study, viable red-colored archaeal strains classified as extremely halophilic archaea (i.e., haloarchaea) and belonging to the genera Halococcus and Halogeometricum were isolated from the plumage of flamingoes in captivity. Detailed analysis for haloarchaeal community structure in flamingo feathers based on metagenomic data identified several haloarchaeal genera and unclassified sequences of the class Halobacteria at the genus level. Carotenoid pigment analyses showed that a bacterioruberin precursor carotenoid in haloarchaea was identical to one of the pigments found in flamingo plumage. To the best of our knowledge, this is the first report of viable extremophilic archaea in avian plumage, thus contributing to our understanding of the ecology of haloarchaea. The potential influence of haloarchaea as an environmental factor determining avian plumage coloration should be investigated in further studies.

Effects of sevoflurane on collagen production and growth factor expression in rats with an excision wound

Background: Sevoflurane is a widely used inhalation anesthetic, but there are no studies on its effect on the wound‐healing process. This study was undertaken to evaluate the effect of exposure time to sevoflurane on wound healing.

Health benefits of lactic acid bacteria isolated from kimchi, with respect to immunomodulatory effects

Kimchi is a traditional Korean fermented vegetable product, which is fermented by various lactic acid bacteria (LAB), including the genera Lactobacillus, Leuconostoc, Pediococcus, and Weissella. While the immunomodulatory effects of LAB isolated from dairy products are relatively well established, little is known about whether kimchi LAB are capable of modulating a variety of host immune responses. Recent studies have shown that several kimchi LAB that show probiotic properties regulate the balance of T-helper cell response by inducing macrophage activation and enhance the differentiation and activation of regulatory T cells, resulting in the alleviation of allergies and atopic dermatitis in animal models. In this review, current knowledge will be discussed about the beneficial effects of kimchi LAB, including the effects of different strains on immunological functions, and the potential use of kimchi LAB strains as immunomodulators in various immunological settings for therapeutic purposes.

Extending the shelf life of kimchi with Lactococcus lactis strain as a starter culture

Lactococcus lactis subsp. lactis WK11 was introduced as a starter in kimchi fermentation to investigate the role of starter cultures in extending the shelf life of kimchi. Kimchi, with an initial inoculum size of 107 CFU/g as well as control kimchi without the starter culture, were prepared and fermented for 56 days at 8°C. The addition of L. lactis prolonged the optimal fermentation period (pH 4.2, acidity 0.6–0.8%) up to more than 2 times. The starter culture, L. lactis WK11, persisted throughout the kimchi fermentation, as confirmed by regular monitoring of the L. lactis population by PCR-DGGE. Taken together, our results suggest that L. lactis starter culture may be useful for extending the shelf-life of kimchi without adverse effects of kimchi with a longer shelf life.

Protective effect of soy powder and microencapsulation on freeze-dried Lactobacillus brevis WK12 and Lactococcus lactis WK11 during storage

Food-grade cryoprotective agents, i.e., skim milk, soy powder, yeast extract, and trehalose were tested for viability of lactic acid bacteria (LAB, Lactobacillus brevis WK12 and Lactococcus lactis WK11) during freeze drying. Ten percentage of soy powder showed a strong protective effect upon viability of both LAB, showing 1.85×1011 CFU/mL for L. brevis WK12 and 1.89×1011 CFU/mL for L. lactis WK11. Microencapsulation in Ca-alginate beads increased viability of LAB, compared to nonencapsulated cells. Moreover, there was a synergetic effect on the stability of LAB when encapsulated LAB in Ca-alginate beads were soaked in 10% of soy powder prior to freeze-drying. When temperature increased, however, survival of LAB decreased. Four weeks after storage the highest viability was observed at -18°C for L. brevis WK12 and L. lactis WK11, showing 1.80×1011 CFU/mL and 1.78×1011 CFU/mL, respectively. These results suggest that soy powder may be useful for enhancing viability of LAB with microencapsulation.