Efficiency of sodium hypochlorite and calcinated calcium in killing Escherichia coli O157:H7, Salmonella spp., and Staphylococcus aureus attached to freshly shredded cabbage.

The effects of the disinfectants NaClO and calcinated calcium on the food-borne pathogens Staphylococcus aureus, Escherichia coli O157:H7, and Salmonella spp. attached to shredded cabbage leaves were examined. After these bacteria were attached to shredded leaves for 1 h, the leaves were treated with NaClO and/or calcinated calcium. About 2.6-log and 3.5-log reductions of E. coli O157 were achieved by treatment with NaClO (100 ppm, pH 6.0, 10 min) and calcinated calcium (0.1%, 20 min), respectively. The combination of 100 ppm NaClO and 0.1% calcinated calcium resulted in a 3- to 4-log reduction in the pathogen populations without apparent deteriorative effects. The bacterial numbers in the treated cabbage did not increase during storage at 4 degrees C. However, sensory evaluation including appearance and flavor indicated that the quality of the treated cabbage declined during storage. In conclusion, the combination of NaClO and calcinated calcium was useful in treatment before eating.

Efficiency of sodium hypochlorite, fumaric acid, and mild heat in killing native microflora and Escherichia coli O157:H7, Salmonella typhimurium DT104, and Staphylococcus aureus attached to fresh-cut lettuce.

The effect of the disinfectant sodium hypochlorite (NaClO), with or without mild heat (50 degrees C) and fumaric acid, on native bacteria and the foodborne pathogens Staphylococcus aureus, Escherichia coli O157:H7, and Salmonella Typhimurium DT104 attached to iceberg lettuce leaves was examined. The retail lettuce examined consistently harbored 6 to 7 log CFU/g of native bacteria throughout the study period. Inner leaves supported 1 to 2 log CFU/g fewer bacteria than outer leaves. About 70% of the native bacterial flora was removed by washing five times with 0.85% NaCl. S. aureus, E. coli, and Salmonella allowed to attach to lettuce leaves for 5 min were more easily removed by washing than when allowed to attach for 1 h or 2 days, with more S. aureus being removed than E. coli or Salmonella Typhimurium. An increase of time for attachment of pathogens from 5 min to 2 days leads to decreased efficiency of the washing and sanitizing treatment. Treatment with fumaric acid (50 mM for 10 min at room temperature) was the most effective, although it caused browning of the lettuce, with up to a 2-log reduction observed. The combination of 200 ppm of sodium hypochlorite and mild heat treatment at 50 degrees C for 1 min reduced the pathogen populations by 94 to 98% (1.2- to 1.7-log reduction) without increasing browning.

Efficacy of acidified sodium chlorite treatments in reducing Escherichia coli O157:H7 on Chinese cabbage.

Efficacy of acidified sodium chlorite for reducing the population of Escherichia coli O157:H7 pathogens on Chinese cabbage leaves was evaluated. Washing leaves with distilled water could reduce the population of E. coli O157:H7 by approximately 1.0 log CFU/g, whereas treating with acidified chlorite solution could reduce the population by 3.0 log CFU/g without changing the leaf color. A similar level of reduction was achieved by washing with sodium chlorite solution containing various organic acids. However, acidified sodium chlorite in combination with a mild heat treatment reduced the population by approximately 4.0 log CFU/g without affecting the color, but it softened the leaves. Moreover, the efficacy of the washing treatment was similar at low (4 degrees C) and room (25 degrees C) temperatures, indicating that acidified sodium chloride solution could be useful as a sanitizer for surface washing of fresh produce.

Detection of recombinant DNA segments introduced to genetically modified maize (Zea mays).

Polymerase Chain Reaction (PCR) techniques are increasingly used for the detection of genetically modified (GM) crops in foods. In this paper, recombinant DNAs introduced into the seven lines of GM maize, such as Event 176, Bt11, T25, MON810, GA21, DLL25, and MON802, are sequenced. On the basis of the obtained sequence, 14 primer pairs for the detection of the segments, such as promoter, terminator regions, and construct genes, were designed. To confirm the specificities of the designed primer pairs, PCR was performed on genomic DNAs extracted from GM and non-GM maize, GM and non-GM soy, and other cereal crops. Because the presence of the corresponding DNA segments was specifically detected in GM crops by the designed primer pairs, it was concluded that this method is useful for fast and easy screening of GM crops including unauthorized ones.

How do chondrocytes aggregate on fibroin substrate.

The effects of substrate material on the spatio-temporal behavior of cells is an important issue. Although cell aggregation has been observed on various fibroin substrates, the mechanisms of this aggregation have yet to be fully clarified. In this study, cell aggregation behavior on fibroin substrates were evaluated, focusing on the distance between each cell and the direction of individual cell migration. Our results showed that on fibroin substrates cells did not attract each other. However cells stayed close to adjacent cells over 24 hours of cultivation.

[Inhibitory effect of essential oils, food additives, peracetic acid and detergents on bacterial histidine decarboxylase].

The aim of this study is to examine whether various essential oils, food additives, peracetic acid and detergents inhibit bacterial histidine decarboxylase. Crude extract of Morganella morganii NBRC3848 was prepared and incubated with various agents. Histidine decarboxylase activity was significantly inhibited (p<0.05) by 26 of 45 compounds tested. Among the 26 agents, sodium hypochlorite completely decomposed both histidine and histamine, while peracetic acid caused slight decomposition. Histidine and histamine were stable in the presence of the other 24 agents. These results indicated that 25 of the agents examined were inhibitors of histidine decarboxylase.

[Antibacterial activity of essential oil vapor for histamine-producing bacteria].

In this study, we evaluated the antibacterial activity of essential oil vapors against histamine-producing bacteria Morganella morganii NBRC3848 and Raultella planticola NBRC3317. We measured the minimum inhibitory dose (MID) of 14 essential oils towards these two strains. Allyl isothiocyanate (AIT) and salicylaldehyde (SA) vapors showed higher antibacterial activity than the other 12 essential oil vapors. Both AIT and SA vapors suppressed growth of total aerobic bacteria and histamine-producing bacteria in bigeye tuna and mackerel meat during storage at 12°C. These vapors also inhibited histamine accumulation in bigeye tuna meat and mackerel meat. Thus, application of AIT and SA vapors is effective for preventing increase of histamine-producing bacteria and histamine formation in fish meat.

[Control of halophilic histamine-producing bacteria by using natural antimicrobials and other agents].

We have investigated the control of halophilic histamine-producing bacteria, Photobacterium phosphoerum and Photobacterium damselae by using vapor of essential oils and other agents. Three of fourteen essential oils showed high antibacterial activity against histamine-producing bacteria. Among food additives and detergents, ten of twenty-one food additives and seven of nine detergents also showed antibacterial activity. Low concentrations of sodium chloride suppressed the growth of both species. We examined the resistance of these bacteria to dryness on food contact surfaces. After 0.5 hours, no viable cells were detected. So, the bacteria were sensitive to dry conditions. These results should contribute to development of the techniques to prevent histamine food poisoning.

[Antibacterial effect of food additives and detergents against histamine-producing bacteria on food contact material surfaces].

We investigated the antibacterial activity of food additives and detergents against histamine-producing bacteria on food contact material surfaces. Based on minimum inhibitory concentration (MIC) testing with Morganella morganii NBRC3848, Raoultella planticola NBRC3317 and Enterobacter aerogenes NCTC10006, we screened nine food additives and four detergents with relatively high inhibitory potency. We prepared food contact material surfaces contaminated with histamine-producing bacteria, and dipped them into fourteen agents (100 µg/mL). Sodium hypochlorite, benzalkonium chloride, benzethonium chloride, n-hexadecyltrimethylammonium chloride and 1-n-hexadecylpyridinium chloride showed antibacterial activity against histamine-producing bacteria. We prepared low concentrations of the five agents (10 and 50 µg/mL) and tested them in the same way. Sodium hypochlorite showed high antibacterial activity at 10 µg/mL, and the other four showed activity at 50 µg/mL. So, washing the material surface with these reagents might be effective to prevent histamine food poisoning owing to bacterial contamination of food contact surfaces.

[Food protective property of new liquid food container PID (Pouch in Dispenser) for microbes].

We examined the content protection characteristics of the PID (Pouch in Dispenser) when it was used in the usual manner and when it was polluted artificially. When the PID was used in the usual manner, the nozzle was opened, and experiments were carried out with and without air-blowing. The invasion of bacteria into the PID was not detected. Also, no bacteria were detected in the material poured from the nozzle of the PID. When 3 strains of bacteria suspensions were intentionally smeared on the nozzle of the PID, invasion of bacteria was observed. When the PID was wiped with a dirty cloth, no invasion of bacteria into the PID was detected. It may be necessary to label the PID with the instruction that the nozzle should not be touched. The effected of changes in the water activity and pH, and the preservatives used, may also need to be considered, depending on the contents in the PID.

Behavior of Yersinia enterocolitica in Foods.

Yersinia enterocolitica are ubiquitous, being isolated frequently from soil, water, animals, and a variety of foods. They comprise a biochemically heterogeneous group that can survive and grow at refrigeration temperatures. The ability to propagate at refrigeration temperatures is of considerable significance in food hygiene. Virulent strains of Yersinia invade mammalian cells such as HeLa cells in tissue culture. Two chromosomal genes, inv and ail, were identified for cell invasion of mammalian. The pathogen can cause diarrhoea, appendicitis and post-infection arthritis may occur in a small proportion of cases. The most common transmission route of pathogenic Y. enterocolitica is thought to be fecal-oral via contaminated food. Direct person-to-person contact is rare. Occasionally, pathogenic Y. enterocolitica has been detected in vegetables and environmental water; thus, vegetables and untreated water are also potential sources of human yersiniosis. However, the isolation rates of pathogenic Y. enterocolitica have been low, which may be due to the limited sensitivity of the detection methods. To identify other possible transmission vehicles, different food items should be studied more extensively. Many factors related to the epidemiology of Y. enterocolitica, such as sources, transmission routes, and predominating genotypes remain obscure because of the low sensitivity of detection methods.

[Antimicrobial efficacy of benzyl isothiocyanate].

The potential value of benzyl isothiocyanate (BIT) vapor for food preservation was investigated in comparison with allyl isothiocyanate (AIT) vapor. Measurements of minimum inhibitory concentration (MIC) against various bacteria and fungi indicated that BIT vapor shows higher antibacterial activity towards Gram-positive bacteria, including lactic acid bacteria, than AIT vapor. BIT has a similar inhibitory effect to AIT against Gram-negative bacteria, yeast and fungi, except that it was less effective against Pseudomonas fluorescens JCM 5963. Both BIT and AIT have a strong inhibitory activity against yeast and fungi. AIT vapor suppressed growth of total aerobic bacteria in bigeye tuna meat and pork mince during storage at 10 degrees C and 30 degrees C, while BIT vapor had no effect. Also, AIT vapor strongly inhibited mycelial development of Aspergillus sojae JCM 2251 and Penicillium expansum IAM 13777 inoculated on rice cakes, while BIT vapor only slightly suppressed their growth. BIT has antimicrobial activities, but further studies are needed to establish its suitability for use in food preservation.

Primary structure analysis and functional expression of erythrose reductases from erythritol-producing fungi (Trichosporonoides megachiliensis SNG-42).

NADPH-dependent erythrose reductases (ERs) in erythritol-producing fungi, Trichosporonoides megachiliensis SNG-42, catalyze the reduction of D-erythrose. We previously characterized the biochemical properties of three isozymes of ERs (ER-I, ER-II, and ER-III). Using internal amino acid sequences of ER-III and ER-I with peptide mapping, we cloned three cDNAs (er1, 1121-bp (AB191474); er2, 1077-bp (AB191475); er3, 1119-bp (AB191476)). The er3 cDNA encoded a polypeptide 36,044 Da, and its deduced amino acid sequence was same as that of the native ER-III. The three recombinant enzymes expressed in Escherichia coli were purified to homogeneity. The recombinant enzymes of ER1, ER2, and ER3 showed similar electrophoretic properties to that of the native ER-I, ER-II, and ER-III on SDS- and Native- but not on IEF-PAGE. All three recombinant enzymes showed substrate specificity towards C-4 and C-3 aldehydes similar to that of the native ER-III. These results strongly suggest that cloned er1, er2, and er3 cDNAs encode erythrose reductases.

Determination of arsenite, arsenate, and monomethylarsonic acid in seawater by ion-exclusion chromatography combined with inductively coupled plasma mass spectrometry using reaction cell and hydride generation techniques.

This paper describes a robust and sensitive method for the determination of arsenic species in seawater by ion-exclusion liquid chromatography (LC) combined with inductively coupled plasma mass spectrometry (ICP-MS) using reaction cell and hydride generation (HG) techniques. A good separation of arsenite, arsenate, and monomethylarsonic acid was achieved using an ion-exclusion column packed with a sulfonated polystyrene resin and a dilute nitric acid at pH 2.0 as the eluent, even when a large volume, i.e. 200 mul, of seawater samples containing a large amount of matrix was repeatedly injected. Separations of the chloride ion due to the matrix and arsenic species were partially performed; however, the extensive peak of ArCl due to high content of Cl(-) in a sample overlapped peaks of the three arsenic species on (75)As measurement by ICP-MS. This ArCl polyatomic interference was efficiently eliminated by collision of ArCl molecules with helium in an octopole reaction cell which was introduced prior to a mass spectrometer. Detection limits of the three arsenic species in a sample containing 2% Cl(-), the concentration of which is comparable to that in a seawater sample, by LC-ICP-MS with the octopole reaction system (ORS), ranged from 21 to 25 pg As ml(-1); these values were three-six times lower than those by LC-ICP-MS without ORS. As another technique for ArCl interference elimination, HG prior to ICP-MS was also successfully used not only to reduce the interference but also to improve the detection limits to 3.4-4.5 pg As ml(-1). The developed LC-ICP-ORS-MS and LC-HG-ICP-MS were validated by analyzing a certified reference material (CRM) of seawater. In addition, no serious decrease in analytical performance of present methods was observed in the experimental periods of half a year for LC-ICP-ORS-MS and 1 year for LC-HG-ICP-MS, respectively. The latter method was successfully applied to characterize seasonal variations of three arsenic species in deep seawater and surface seawater.