Wooki Kim

Physicochemical properties of granular and non-granular cationic starches prepared under ultra high pressure

Granular and non-granular cationic starches were prepared through the reaction of tapioca and corn starches with 2,3-epoxypropyl trimethyl ammonium chloride (ETMAC) using conventional and ultra high pressure (UHP)-assisted reactions. The cationic starches were characterized with respect to morphology, degree of substitution (DS), FT-IR, (13)C NMR, X-ray diffraction pattern, solubility and swelling power, pasting viscosity, and flocculating activity. Non-granular (relative to granular) cationic starches possessed higher DS values. While DS values of non-granular cationic starches were lower for UHP-assisted (relative to conventional) reaction, granular cationic starches did not differ for both reactions. For flocculation activity, granular cationic starches with lower solubility and higher swelling power were higher than non-granular counterparts with reversed patterns in solubility and swelling power, regardless of conventional and UHP-assisted reactions. Overall results suggested that flocculation activity of cationic starches may be directly associated with their swelling powers (relative to DS values).

Biotechnological production of arbutins (α- and β-arbutins), skin-lightening agents, and their derivatives

Arbutins (α- and β-arbutins) are glycosylated hydroquinones that are commercially used in the cosmetic industry. These compounds have an inhibitory function against tyrosinase, a critical enzyme for generating pigments, which leads to the prevention of melanin formation, resulting in a whitening effect on the skin. Although β-arbutin is found in various plants including bearberry, wheat, and pear, α-arbutin and other arbutin derivatives are synthesized by chemical and enzymatic methods. This article presents a mini-review of recent studies on the production of α-arbutin and other α- and β-arbutin derivatives via enzymatic bioconversion methods. In addition, the structures of α- and β-arbutin derivatives and their biological activities are discussed. The catalytic characteristics of various enzymes used in the biosynthesis of arbutin derivatives are also reviewed.

Complete Genome Sequence of the Hyperthermophilic Archaeon Pyrococcus sp. Strain ST04, Isolated from a Deep-Sea Hydrothermal Sulfide Chimney on the Juan de Fuca Ridge

Pyrococcus sp. strain ST04 is a hyperthermophilic, anaerobic, and heterotrophic archaeon isolated from a deep-sea hydrothermal sulfide chimney on the Endeavour Segment of the Juan de Fuca Ridge in the northeastern Pacific Ocean. To further understand the distinct characteristics of this archaeon at the genome level (polysaccharide utilization at high temperature and ATP generation by a Na(+) gradient), the genome of strain ST04 was completely sequenced and analyzed. Here, we present the complete genome sequence analysis results of Pyrococcus sp. ST04 and report the major findings from the genome annotation, with a focus on its saccharolytic and metabolite production potential.

Evidence for protective effects of coffees on oxidative stressinduced apoptosis through antioxidant capacity of phenolics

This study evaluated total phenolics, total flavonoids, and antioxidant capacity of randomly selected regular and decaffeinated coffees commercially available in Korea and their protective effects in human hepatic epithelial HepG2 cell line against oxidative stress. All coffees tested exhibited potent antioxidant capacity in chemical systems and, consequently, significant protection of cells from oxidative stress in vitro in a dose-dependent manner. In particular, H2O2-induced apoptosis as evaluated by annexin V staining and flow cytometry was prevented by coffee extracts, resulting in the enhanced cell viability. Of interest, the content of total phenolics and flavonoids in coffees demonstrated a positive correlation with antioxidant capacity, indicating that the antioxidant capacity of coffees may be attributed to those phytochemicals. In accordance with previous studies, caffeoylquinic acid (CQA) and its derivatives including 3-CQA, 4-CQA, 5-CQA, 3,4-diCQA, 3,5-diCQA, and 4,5-diCQA were identified as phenolic phytochemicals by a reversed-phase HPLC, with 5-CQA being a major component. Taken together, the present study demonstrated protective effects of regular and decaffeinated coffees on cells in vitro against overwhelming oxidative stress due to richness in phenolics, especially CQA and its derivatives. Coffees, regular or decaffeinated, may serve as a good source of health-beneficial phytochemicals in diet.

Retrogradation kinetics of cross-linked and acetylated corn starches under high hydrostatic pressure

Retrogradation kinetics of conventionally and high hydrostatic pressure (HHP)-assisted chemically modified (cross-linked with sodium trimetaphosphate/sodium tripolyphosphate (STMP/STPP) and acetylated with acetic anhydride) corn starches were investigated. During storage at 4°C, the glass transition temperature (Tg′) and the ice melting enthalpy were measured using differential scanning calorimetry (DSC), and relative crystallinity was measured using an X-ray diffractometer (XRD). In both conventionally and HHP-assisted modified corn starches, the Tg′ value and relative crystallinity increased during first 7–10 days of storage, then stabilized, whereas the ice melting enthalpy decreased until 10 days of storage, then remained constant. HHP-assisted modified starch showed different retrogradation kinetics from conventionally modified starch. However, the retrogradation rates of both samples were lower than for native corn starch. Although the Tg′ value, the ice melting enthalpy, and relative crystallinity represent different physicochemical properties, all can be used as indicators for evaluation of starch retrogradation.

Infusion of catechin into native corn starch granules for drug and nutrient delivery systems

Hydrophilic nutrients, a water insoluble drug, and amino acids were used as infusion materials for analysis w ith HPLC and a micro-plate reader. Only catechin, gallic a cid, and caffeine infused into native corn starch granules. While catechin remained in the native corn starch granule after several washing steps, infused caffeine and gallic acid were washed out. A release study was also performed using pancreatin α-amylase. Infused catechin was successfully released when native corn starch granules were decomposed. Infusion and maintenance of catechin in native corn starch granules were probably due to a unique chemical structure of the benzene-tetrahydropyran group that affected interactions with starch. However, experiments using epicatechin and rutin indicated that the benzenetetrahydropyran group structure may not have been the only reason for infusion of guest materials. The 3 dimensional structure of the benzene-tetrahydropyran group probably also influenced infusion of materials.

Inactivation of the virulence factors from 2,3-butanediol-producing Klebsiella pneumoniae

The microbiological production of 2,3-butanediol (2,3-BDO) has attracted considerable attention as an alternative way to produce high-value chemicals from renewable sources. Among the number of 2,3-BDO-producing microorganisms, Klebsiella pneumoniae has been studied most extensively and is known to produce large quantity of 2,3-BDO from a range of substrates. On the other hand, the pathogenic characteristics of the bacteria have limited its industrial applications. In this study, two major virulence traits, outer core LPS and fimbriae, were removed through homologous recombination from 2,3-BDO-producing K. pneumoniae 2242 to expand its uses to the industrial scale. The K. pneumoniae 2242 ∆wabG mutant strain was found to have an impaired capsule, which significantly reduced its ability to bind to the mucous layer and evade the phagocytic activity of macrophage. The association with the human ileocecal epithelial cell, HCT-8, and the bladder epithelial cell, T-24, was also reduced dramatically in the K. pneumoniae 2242 ∆fimA mutant strain that was devoid of fimbriae. However, the growth rate and production yield for 2,3-BDO were unaffected. The K. pneumoniae strains developed in this study, which are devoid of the major virulence factors, have a high potential for the efficient and sustainable production of 2,3-BDO.

Characterization of cationic dextrin prepared by ultra high pressure (UHP)-assisted cationization reaction

Cationic dextrins were prepared through substitution reaction of dextrin with low and high addition levels of 2,3-epoxypropyltrimethylammonium chloride (ETMAC), respectively. Conventional cationization reactions were carried out for 5h under continued stirring. UHP-assisted cationization reactions were conducted at three pressurization levels of 100, 300 and 500 MPa for a pressure holding time of 30 min. Degree of substitution (DS) of UHP-assisted cationic dextrins ranged from 0.58 to 1.51, and in general, their DS values were enhanced with increasing pressure levels. FT-IR and (13)C NMR spectra indicated the presence of CN bond, which provided clear evidence about incorporation of cationic moieties onto dextrin molecules. In flocculation test, UHP-assisted cationic dextrin revealed higher flocculating activity. Overall results suggested that UHP-assisted cationization reaction could modulate reactivity and flocculating activity of dextrin by controlling pressure levels and reaction mixture compositions, and cationic dextrins likely possessed a higher potential to replace synthetic polymer-based flocculants.

Linarin down-regulates phagocytosis, pro-inflammatory cytokine production, and activation marker expression in RAW264.7 macrophages

Plant-extracted flavonoid glycosides have been reported to be bioactive compounds with pleiotropic functions, including antioxidant, anti-inflammatory, and anti-cancer effects. This study investigated the anti-inflammatory role of linarin (acacetin-7-rutinoside, which is found in Chrysanthemum indicum (Gam-Guk) and Dendranthema zawadskii (Gu-Jul-Cho)), on lipopolysaccharide-stimulated RAW264.7 macrophages. Linarin treatments exhibited no cytotoxicity up to a concentration of 30 μM, as assessed by MTT assay. The production of nitric oxide, an inflammatory mediator, was decreased by addition of linarin. The secretion of pro-inflammatory cytokines, interleukin-1β and interleukin-6, was significantly decreased in a dose-dependent manner. Linarin also decreased the phagocytic ability of macrophages following co-culture with fluorescent beads. In addition, expression levels of antigenpresenting surface markers, MHC II and CD80, were suppressed by linarin. Taken together, these results indicate that the flavonoid glycoside linarin has an anti-inflammatory effect, in part through the suppression of phagocytosis, cytokine production, and antigen presentation in macrophages.

Advances in Nutritional Research on Regulatory T-Cells

Many clinical and animal studies have shown that certain dietary components exert anti-inflammatory properties that aid in the amelioration of chronic inflammatory diseases. Among the various proposed channels through which dietary components affect immune responses, regulatory T-cells (Tregs) are emerging as key targets for the dietary prevention of chronic inflammatory diseases. In this review, immunoregulation by Tregs is briefly described, followed by a summary of recent advances and possible applications of techniques for the study of Tregs. In addition, this review provides an overview of the current knowledge on Treg regulation by certain dietary components, including vitamins, omega-3 polyunsaturated fatty acids, and polyphenols. The caveats of previous studies are also discussed in order to highlight the distinctions between dietary studies and immunological approaches. Consequently, this review may help to clarify the means by which nutritional components influence Tregs.