Inactivation of Bacillus cereus spores by high hydrostatic pressure at different temperatures

The effect of pH on the initiation of germination and on the inactivation of Bacillus cereus (KCTC 1012) spores during high hydrostatic pressure processing (HPP) with pressures of 0.1 to 600 MPa at different temperatures was investigated. Two different high-pressure treatments were adopted to evaluate the effect of pH on the inactivation of B. cereus on sporulation medium and in suspension medium. Inactivation of B. cereus spores with HPP treatment was affected more by sporulation medium pH than by suspension medium pH. B. cereus spores obtained through sporulation at pH 6.0 showed more resistance to inactivation by HPP at 20, 40, and 60 degrees C than did those obtained through sporulation at pHs of 7.0 and 8.0. Constituents of B. cereus spores obtained through sporulation at pH 6.0 may undergo electrochemical charge changes comparable to those for spores obtained through sporulation at pH 7.0. The initiation of B. cereus spore germination was more sensitive to pressure around 300 MPa at 20 degrees C. Increasing processing temperatures during HPP enhanced the effect of sporulation medium pH (i.e., environmental pH) on the inactivation of B. cereus spores.     

Lipid production in Porphyridium cruentum grown under different culture conditions

Autotrophic growth of Porphyridium cruentum under 18:12 h and 12:12 h light:dark cycles showed the maximum cell concentration of 2.1 g-dry wt./L, whereas the specific growth rate, 0.042 (1/h), at 18:6 h is faster than that of 12:12 h, 0.031 (1/h), respectively. The highest lipid accumulation level, 19.3 (%, w/w), was achieved at 12:12 h cycle. Under dark cultivation condition with 10 g/L of glucose, the lipid accumulation in the cell was 10.9 (%, w/w), whereas the heterotrophic growth with glycerol as the carbon resource showed low level of cell concentration and lipid production, compared to that of glucose. The glucose was decided to be a suitable carbon resource for the heterotrophic growth of P. cruentum. The lipids from P. cruentum seemed be feasible for biodiesel production, because over 30% of the lipid was C₁₆–C_18:1. The cultivation time and temperature were important factors to increase the maximum cell concentration. Extending the cultivation time helps maintain the maximum cell concentration, and higher lipid accumulation was achieved at 25 °C, compared to 35 °C. The fed-batch cultures showed that, under the light condition, the specific production rate was slightly decreased to 0.4% lipid/g-dry wt./day at the later stage, whereas, under the dark condition, the specific production rate was maintained to be a maximum value of 1.1% lipid/g-dry wt./day, even in the later stage of cultivation. The results indicate that the heterotrophic or 12:12 h cyclic mixotrophic growth of P. cruentum could be used for the production of biodiesel in long-term fed-batch cultivation of P. cruentum.     

Antimicrobial resistance of Escherichia coli O157 from cattle in Korea

Of 45 Escherichia coli O157 isolates from cattle feces, which were collected between May 2000 and September 2003 in Korea, 32 were resistant to at least 1 antibiotic and 28 were resistant to 4 or more antibiotics, with 32, 30 and 30 of the isolates being resistant to streptomycin, tetracycline and sulfisoxazole, respectively. Two isolates were resistant to fluoroquinolones and to 10 or more of the 22 other antimicrobial agents that were tested. Thirteen antimicrobial resistant patterns were observed. The most frequent resistance type, which was found for 11 isolates, was streptomycin-tetracycline-kanamycin-ampicillin-piperacillin-cephalothin-sulfisoxazole-ticarcillin. Polymerase chain reaction (PCR) analysis of the isolates for E. coli O157 virulence markers revealed that 25 of the resistant E. coli O157 isolates tested positive for stx2 or both stx1 and stx2 genes. These findings suggest that many of the resistant E. coli O157 isolates might cause disease in humans.     

Green Tea Formulations with Vitamin C and Xylitol on Enhanced Intestinal Transport of Green Tea Catechins

The effect of green tea formulated with vitamin C and xylitol on intestinal cell transport of gallated and nongallated catechin was studied. The transport of catechins from both apical to basolateral and basolateral to apical directions was measured. The effect of vitamin C (4, 10, 20 ppm), xylitol (11, 27.5, 55 ppm), and combinations of both on the intestinal transport rate of catechins was examined. The efflux value (Pb→a/Pa→b) of (–)‐epigallocatechin (EGC), (–)‐epigallocatechin gallate (EGCG), (–)‐epicatechin (EC), and (–)‐epicatechin gallate (ECG) was 0.26, 0.22, 1.22, and 0.17, respectively, indicating that EC appeared to be less absorbed compared with other catechins. The addition of xylitol (11, 27.5, 55 ppm) and vitamin C (4, 10, 20 ppm) and in combination enhanced transport rate of nongallated catechins such as EC and EGC. For EC, vitamin C was revealed to be the most effective on intestinal transport, implying the inhibition of the efflux transport mechanism of EC. Intestinal transport of gallated catechins significantly increased from catechins formulated with vitamin C and xylitol in a dose‐dependent manner compared to the catechin‐only formulation. Results provide a potential strategy to enhance the delivery and bioavailability of catechins in humans by modulating green tea formulation with vitamin C and xylitol.     

Mechanistic relationships among PCDDs/Fs, PCNs, PAHs, CIPhs, and CIBzs in municipal waste incineration

An extensive investigation was conducted to understand polychlorinated dibenzo-p-dioxin and furan (PCDD/F) formation mechanisms and their relationship with other organic compounds. PCDD/F, chlorophenols (CIPhs), chlorobenzenes (CIBzs), polyaromatic hydrocarbons (PAHs), and polychlorinated naphthalenes (PCNs) were analyzed in the boiler exit gases of a field-scale municipal solid waste incinerator under various operating conditions. The TEQ value and the concentration of target compounds changed with incinerator operating conditions. Low mass PAHs and 246-triCIPh increased dramatically during shut downs; the latter was associated with increased 1368- and 1379-TeCDD. A strong correlation was observed between PCNs and PCDFs and adjacent PCNs homologue group were closely related to each other. This suggested that PCN formation is related with chlorination/dechlorination mechanisms similar to PCDFs. PCDDs were related with most of the CIPhs and the high chlorinated benzenes. Most of target compounds except PAHs had a positive correlation (R2 > 0.5) with TEQ and half of them showed a good relationship (R2 > 0.8) with PCDDs/Fs toxic equivalency (TEQ).     

Analysis of kimchi microflora using denaturing gradient gel electrophoresis

A polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) technique was used to determine the microfloral composition during the fermentation of kimchi, a traditional Korean fermented vegetable food. The kimchi was fermented at 10 degrees C or 20 degrees C for 30 or 20 days, respectively. DGGE of the partially amplified 16S rDNA was performed and the most intense bands sequenced. The application of this culture-independent molecular technique determined that the lactic acid bacteria Weissella confusa, Leuconostoc citreum, Lactobacillus sakei, and Lactobacillus curvatus were the main microorganisms responsible for kimchi fermentation.     

Numerical simulation of trailed vortex alleviation through chipped wingtip shapes

The shedding of strong vortices generated during take-off and landing poses serious hazards for the following aircraft. To circumvent the vortex wake hazard, a chipped wingtip shape was suggested, and a series of numerical simulations were conducted to verify the conceptual validity of such shape. Numerical simulation was performed by using the incompressible Navier-Stokes solver with the pressure-based semi-implicit method for pressure linked equations algorithm. The Reynolds stressmodel was employed to evaluatethe turbulence effects.The trailed vortices of the chipped wingtip shapes were found to be more dissipative than those of the baseline wingtip shape. The counter-rotating vortices produced by the chipped wingtip shape can weaken the primary wingtip vortex strength in the far field. Regardless of the slightly increasing the drag, the chipped wingtip shape can successfully mitigate the tangential velocity of the vortices. These types of wingtip shapes had various design parameters, such as the aspect ratio, spacing, and area of each chip. Systematic numerical simulations were conducted to evaluate the effect of these parameters. According to the parametric study results, the aspect ratio was sensitive to the increase in the drag coefficient, and the area was susceptible to the moment coefficient. Evidently, a trade-off relationship existed between the tangential velocity reduction and the drag increase.     

Resveratrol analogue,HS-1793, inhibits inflammatory mediator release from macrophages by interfering with the TLR4 mediated NF-κB activation

Food Science and Biotechnology - Resveratrol is known to have anti-inflammatory properties. However, high-dose resveratrol is required for optimal anti-inflammatory effects. HS-1793 is a derivative...     

Antioxidant Properties of Aqueous Extract of Roasted Hulled Barley in Bulk Oil or Oil‐in‐Water Emulsion Matrix

Antioxidant properties of the aqueous extracts of hulled barley (Hordeum vulgare L.) that had been roasted at 210 °C for 20 min were determined in bulk oil and oil‐in‐water (O/W) emulsions. Bulk oils were heated at 60, 100, and 180 °C, and O/W emulsions were oxidized under riboflavin photosensitization. The content of phenolic compounds was analyzed by high‐performance liquid chromatography, and in vitro antioxidant assays were also conducted. The major phenolics contained in the aqueous extract of roasted hulled barley (AERB) were p‐coumaric, ferulic, protocatechuic, chlorogenic, 4‐hydroxybenzoic, and vanillic acids. Depending on the concentration and oxidation temperature, AERB had antioxidant or prooxidant properties in bulk oil. At 60 °C, AERB at a concentration of 0.5% acted as a prooxidant, whereas at 1.0% it acted as an antioxidant. At 100 °C, AERB acted as an antioxidant irrespective of concentration. In 180 °C conditions, 0.5% AERB acted as a prooxidant, whereas other concentrations of AERB acted as antioxidants. In the case of riboflavin photosensitized O/W emulsions, AERB showed antioxidant properties irrespective of concentration. Antioxidant abilities of AERB are affected by the food matrix, including bulk oil and O/W emulsions, and concentrations of AERB, even though diverse phenolic compounds may display high antioxidant properties in in vitro assays.     

Prevalence, antibiotic susceptibility, and virulence factors of Yersinia enterocolitica and related species from ready-to-eat vegetables available in Korea

A total of 673 ready-to-eat vegetable samples were collected in Korea from 2001 to 2002 and analyzed for the presence of Yersinia spp. We analyzed biotypes, serotypes, and susceptibility to 12 antibiotics and tested for virulence genes of pathogenic Yersinia enterocolitica isolates by PCR assay. Among the samples, 27 (4.0%) were found to be contaminated with Yersinia spp. Among the 27 strains of Yersinia spp. isolates, 18 strains (66.7%) of Y. enterocolitica, 5 strains (18.5%) of Y. frederiksenii, 3 strains (11.1%) of Y. intermedia, and 1 strain (3.7%) of Y. kristensenii were identified. According to the serotypes of Y. enterocolitica isolates, O:3 (11.1%) and O:5 (11.1%) were the most predominant, followed by O:8 (5.6%) and others (72.2%). For biotypes of Y. enterocolitica isolates, 1A (77.8%) was the most predominant, followed by 3B (11.1%), 3 (5.6%), and 5A (5.6%). Also, an antibiotic susceptibility test showed that Y. enterocolitica isolates were very susceptible to the antibiotics tested but highly resistant to ampicillin (94%), cephalothin (100%), and carbenicillin (83%). PCR assays with specific primers derived from yst and ail genes of Y. enterocolitica were applied to confirm the presence of pathogenic Y. enterocolitica. Among the 18 strains of Y. enterocolitica isolates, only 3 strains (O:3/1A, UT/3B, and UT/1A isolated from Chinese cabbage, onion, and spinach, respectively) were shown to have a virulence gene.