Haraguchi K.,Japan National Food Research Institute
Carbohydrate Polymers | Year: 2010
An inulin fructotransferase (DFA III-producing) [EC 220.127.116.11] from Arthrobacter ureafaciens D13-3 was purified and characterized. The enzyme was purified from culture supernatant of the microorganism 22.3-fold with a yield of 23.6%. The enzyme showed maximum activity at pH 5.5 and 50 °C. The enzyme activity was stable up to 70 °C after 30 min heat treatment. The molecular mass of the enzyme was estimated to be 40 kDa by SDS-PAGE and 43 kDa by gel filtration, and the enzyme was considered to be a monomer. The smallest fructo-oligosaccharide as the substrate was estimated to be GF3 (nystose). The N-terminal amino acid sequence (12 amino acid residues) was analyzed as TTVYDTTVDVP. © 2010 Elsevier Ltd. All rights reserved.
Haraguchi K.,Japan National Food Research Institute
Carbohydrate Polymers | Year: 2013
A gene of inulin fructotransferase (DFA III-producing) [EC 18.104.22.168] from Arthrobacter sp. L68-1 was cloned and the nucleotide was sequenced. The gene encoded a signal peptide (32 amino acid residues) for a secretion, and the mature enzyme protein was estimated to be consisted with 410 amino acid residues. The molecular mass of the native enzyme was calculated as 43.7 kDa by the sequence data. The deduced amino acid sequence of the enzyme had 79.0% homology with that of the Arthrobacter globiformis C11-1, and had 77.4% homology with that of the Arthrobacter sp. H65-7. It also had 43.7% homology with that of inulin fructotransferase (DFA I-producing) [EC 22.214.171.124] from A. globiformis S14-3. The cloned enzyme was immobilized using Chitopearl BCW 3510 as a carrier. The immobilized enzyme was able to use 10 times without a significant loss of the enzyme activity. © 2012 Elsevier Ltd.
Ide T.,Japan National Food Research Institute |
Ide T.,Jumonji University
British Journal of Nutrition | Year: 2014
In the present study, the mRNA levels of hepatic proteins involved in the drug metabolism of rats fed α-lipoic acid were evaluated by DNA microarray and real-time PCR analyses. Experimental diets containing 0, 0·1, 0·25 and 0·5 % (w/w) α-lipoic acid were fed to four groups of rats consisting of seven animals each for 21 d. DNA microarray analysis revealed that the diet containing 0·5 % α-lipoic acid significantly (P< 0·05) increased the mRNA levels of various phase I drug-metabolising enzymes up to 15-fold and phase II enzymes up to 52-fold in an isoenzyme-specific manner. α-Lipoic acid also up-regulated the mRNA levels of some members of the ATP-binding cassette transporter superfamily, presumed to be involved in the exportation of xenobiotics, up to 6·6-fold. In addition, we observed that α-lipoic acid increased the mRNA levels of many proteins involved in antioxidation, such as members of the thiol redox system (up to 5·5-fold), metallothioneins (up to 12-fold) and haeme oxygenase 1 (1·5-fold). These results were confirmed using real-time PCR analysis, and α-lipoic acid dose dependently increased the mRNA levels of various proteins involved in drug metabolism and antioxidation. Consistent with these observations, α-lipoic acid dose dependently increased the hepatic concentration of glutathione and the activities of glutathione reductase and glutathione transferase measured using 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene as substrates, but decreased the hepatic and serum concentrations of malondialdehyde. In conclusion, the present study unequivocally demonstrated that α-lipoic acid increases the mRNA expression of proteins involved in drug metabolism and antioxidation in the liver. Copyright © The Author 2014.
Nei D.,Japan National Food Research Institute
Food Control | Year: 2014
Histamine is one cause of scombroid foodborne poisoning. The bacterial decarboxylation of amino acids leads to the formation of biogenic amines such as histamine. This study examined histamine accumulation in tuna and yellowtail fillets that had been sterilized by gamma irradiation to confirm whether factors other than bacterial activity are able to induce histamine accumulation. Fish fillets were sterilized by gamma irradiation at 35kGy and stored for 7 days at 5, 15, or 25°C, and the resulting histamine concentrations were measured. The histamine concentrations in all tested samples of tuna and yellowtail were below the detection limit of the assay used (<10mg/kg). In contrast, the tuna and yellowtail meats inoculated with Morganella morganii, a known histamine-producing bacterium, showed significant histamine accumulation at 15 and 25°C. These results indicated that non-bacterial factors do not promote histamine accumulation. Therefore, the proper control of histamine-producing bacteria is both necessary and sufficient to prevent histamine accumulation. © 2013 Elsevier Ltd.
Tsuzuki W.,Japan National Food Research Institute
Food Chemistry | Year: 2011
To elucidate the relation between heat-induced cis/trans isomerisation and thermal oxidative degradation of double bonds in unsaturated lipids, we investigated the effects of several edible antioxidants on these two molecular structural changes of double bonds in triolein (cis-9, 18:1) and trilinolein (cis-9, cis-12, 18:2), which were heated at 180°C. trans Isomerisation and oxidative degradation of each cis double bond in the triacylglycerols during heating were evaluated on the basis of the increase in the amount of trans isomers and decrease in the amount of cis isomers by gas chromatography analysis. The synchronous suppression in trans isomerisation and cis deterioration of double bonds in these triacylglycerols were found by addition of antioxidants, whose inhibitory effects were associated with their kinds and concentrations. When triolein was heated in the presence of antioxidant, suppression of heat-induced trans isomerisation was directly proportional to that of cis deterioration. The results of our analysis suggested that the appropriate addition of antioxidants to edible oils during processing and cooking would facilitate the control of not only thermal oxidative degradation but also heat-induced trans isomerisation of double bonds in unsaturated lipids. © 2011 Elsevier Ltd. All rights reserved.
Tsuzuki W.,Japan National Food Research Institute
Chemistry and Physics of Lipids | Year: 2010
We investigated the heat-induced cis/trans isomerization of double bonds in monounsaturated lipids. When triolein (9-cis, 18:1) was heated around 180 °C, small amounts of isomerization products were obtained depending on the heating period. The heat-induced isomerization of triolein was considerably suppressed by the addition of different antioxidants or under nitrogen stream, and these additives simultaneously inhibited the thermal oxidation of double bonds in triolein. Therefore, an intermediate of the thermal oxidation reaction might be responsible for the heat-induced isomerization of the double bonds in triolein. The thermodynamics of the heat-induced isomerization of triolein (9-cis, 18:1) and trielaidin (9-trans, 18:1) were investigated using Arrhenius plot. The Arrhenius activation energies of cis double bonds in triolein and trans double bonds in trielaidin were 106 kJ/mol and 137 kJ/mol, respectively. The calculated internal rotational barrier heights of these double bonds were similar to those of the double bond of 2-butene radical and significantly lower than those of non-radicalized double bonds in 2-butene. These results suggest that heat-induced cis/trans isomerization of triolein and trielaidin occurs mainly through the formation of radical species, which are the intermediates produced during thermal oxidation. The activation energy difference between the two forms suggests that trans trielaidin radicals are more stable than cis triolein radicals. The high thermodynamic stability of the trans double bonds in lipid radicals would influence the population of cis and trans isomers in edible oils and contribute to slight accumulation of trans-18:1 isomers during heating or industrial processing. © 2010 Elsevier Ireland Ltd. All rights reserved.
Tsukakoshi Y.,Japan National Food Research Institute
Analyst | Year: 2011
Here, the uncertainty budget for a total diet study (TDS) was clarified by separating the total measurement uncertainty into the uncertainty arising from the compositional heterogeneity of food items between cities (referred to as inter-city variance), the heterogeneity of food items within cities (intra-city variance), and the chemical analysis of the food samples (analytical variance) at one study design. TDS samples were collected from 14 cities in Japan. Duplicate samples collected in each city were prepared from food items purchased from different shops, and the cadmium concentrations were measured individually to obtain the intra-city variance. These results were used to show the importance of sampling design in TDSs, by evaluating a sampling method known as a multi-stage design, in which multiple samples are collected from several cities. Such schemes have been applied to TDSs, but the uncertainty involved has not been assessed. An intra-city correlation was observed between the cadmium concentrations in samples from the same city, demonstrating that the effective sample size was not simply the number of cities and shops sampled. The TDS results showed a high intra-city variance, which was greater than the inter-city variance for all of the food groups studied, and particularly for the bean and potato groups. By combining the sampling and analytical uncertainties obtained, the sampling uncertainty across different primary sampling unit sizes and secondary sampling unit sizes was obtained. As suggested by the analysis of potatoes and beans, grouping food samples from different shops in the same city can improve the representativeness of the results. © 2011 The Royal Society of Chemistry.
Koseki S.,Japan National Food Research Institute
Food Control | Year: 2013
An alternative predictive model for microbial inactivation and a novel web-based tool for the application of predictive microbiology are reviewed in this paper. The developed model, based on probabilistic concepts, enabled the identification of minimum processing conditions necessary to obtain a required log reduction, regardless of the underlying inactivation kinetics. The model also provides the probability distribution of the inactivation effect. The revised web-tool, the MRV (Microbial Responses Viewer), provides information concerning growth/no growth boundary conditions and the specific growth rates of queried microorganisms. The MRV enables users to retrieve microbial growth/no growth information intuitively. Using the MRV, food processors can easily identify appropriate food design and processing conditions. © 2012 Elsevier Ltd.
Nagao A.,Japan National Food Research Institute
Japan Agricultural Research Quarterly | Year: 2014
Various carotenoids with diverse structures are present in foods and have been reported to have beneficial effects on human health. Owing to their hydrophobicity, however, poor solubilization in the aqueous milieu of the digestive tract restricts their intestinal absorption. Fats and oils were found to increase the solubilization of carotenoids into mixed-micelles, which would therefore enhance their bioavailability. The uptake of carotenoids solubilized in the micelles by intestinal cells are thought to be mediated by simple diffusion and/or facilitated diffusion through scavenger receptors. Lipids that constituted the mixed-micelles affected the uptake of carotenoids. In particular, lysophosphatidylcholine significantly enhanced uptake. Highly polar carotenoids, meanwhile accumulated in mice but not in humans, suggesting discriminate absorption and metabolism in the latter. The metabolism of provitamin A carotenoids is well known to be mediated by the central cleavage enzyme. Recently, another cleavage enzyme was found to cleave various carotenoids asymmetrically into apocarotenoids. Xanthophylls were found to be oxidized to unstable keto-carotenoids in mice. These metabolic conversions are thought to affect the levels of bioavailable carotenoids in tissues. In this article, the solubilization into mixed-micelles, intestinal absorption and oxidative metabolism of carotenoids are reviewed to understand the factors that determine the bioavailability of carotenoids ingested from fruit and vegetables.
Okamoto S.,Japan National Food Research Institute
Chemistry and Biology | Year: 2012
Activation/exploitation of biosynthetic pathways for useful metabolites is a major current interest. The metabolism remodeling approach developed by Craney and colleagues in this issue of (Chemistry & Biology), in which small molecule probes alter the secondary metabolites produced by streptomycetes, could lead to discovery of a multitude of novel antibiotics and other drugs. © 2012 Elsevier Ltd.