Enhanced production of trehalose in Escherichia coli by homologous expression of otsBA in the presence of the trehalase inhibitor, validamycin A, at high osmolarity

Trehalose production in Escherichia coli DH5α was explored by overexpressing otsBA operon encoding trehalose-6-phosphate synthase and trehalose-6-phosphate phosphatase. Production and subsequent degradation of trehalose resulted in low production of trehalose in engineered cells overexpressing otsBA, which was primarily due to the concomitant expression of endogenous trehalase. Through an in vitro enzyme assay and flask cultures of engineered cells, trehalase expression was shown to be directly related to the expression of otsBA rather than osmotic stress. Validamycin A effectively inhibited E. coli trehalase and the intracellular accumulation of trehalose was markedly enhanced in the presence of validamycin A at an optimal concentration in the medium. The trehalose production was further increased upon growth in a hypertonic medium in the presence of validamycin A, with most trehalose accumulating as an intracellular product. The highest titer was obtained when otsBA expression was induced by a medium-copy vector, ptrc99A, with 0.5mM of isopropyl β-d-1-thiogalactopyranoside. Trehalose titer was 1.7 g/L in controlled bioreactor cultures using synthetic M9 medium supplemented with 40 g/L glycerol, 0.1mM validamycin A, and 300 mM NaCl.     

Chlorine treatment to inactivate norovirus on food contact surfaces

This study was conducted to determine the concentration and optimal treatment time of chlorine for reducing feline calicivirus (FCV) and murine norovirus (MNV) as surrogates of norovirus (NoV) on stainless steel surfaces and to develop a predictive inactivation method using a response surface methodology. The reduction levels of FCV VR-782 and MNV on stainless steel surfaces after treatment with various concentrations of chlorine (0 to 5,000 ppm) for various times (0 to 5 min) were measured. The reduction values of both FCV and MNV on stainless steel surfaces after 5,000 ppm of chlorine treatment for 5 min were 5.20 TCID(50) per coupon. The predictive results obtained by central composite design were analyzed by standard analysis of variance. The application of multiple regression analysis was related to the following polynomial equations: (i) FCV (log TCID(50) per coupon) = -0.3714 + 0.8362x(1) + 0.0011x(2) + 0.0001x(1)x(2) - 0.1143x(2)(1) -0.0001x(2)(2) (x(1), time; x(2), concentration) and (ii) MNV (log TCID(50) per coupon) = + 0.0471 + 0.0807x(1) + 0.0011x(2) + 0.0001x(1)x(2) -0.0910x(2)(1) -0.0001x(2)(2) (x(1), time; x(2), concentration). It was concluded that these polynomial equation models of reduction of FCV and MNV could be used to determine the minimum concentration of chlorine and exposure times to control human NoV on food contact surfaces.     

Effectiveness of intermittent iron treatment of two- to six-year-old Jordanian children with iron-deficiency anemia

BACKGROUND: Iron deficiency is a common nutritional problem in young children among vulnerable populations in Jordan. Several studies have shown the effectiveness of intermittent iron supplementation in improving iron status. Such a study has not been carried out in 2- to-6-year-old Jordanian children diagnosed with iron deficiency anemia in a clinical setting. OBJECTIVE: To study the effectiveness of intermittent versus daily iron treatment in a clinical setting in 2- to 6-year-old Jordanian children with iron-deficiency anemia. METHODS: About 4400 children aged 2 to 6 years who visited Prince Hashim Military Hospital in Zarqa, Jordan, from August 2000 to June 2001 were screened for age, general health, and birthweight. About 10% of these children were screened for anemia, using complete blood count (defined as a hemoglobin level < or = 10.5 g/dL, and a mean corpuscular volume < or =75 ft). Anemic children underwent further screening for iron deficiency, defined as serum ferritin level < or =12 microg/L. Children with iron-deficiency anemia, as indicated by hemoglobin < or = 10.5 g/dL, mean corpuscular volume < or =75 fL, and serum ferritin < or =12 microg/L, or as indicated by mean corpuscular volume < or =75 fL and hemoglobin < or = 10.5 g/dL, were enrolled in the study after informed oral consent by their parents. Study children (n=134) were assigned randomly to one of three groups. Subjects in group 1 (n=45), group 2 (n=45), and group 3 (n=44) received iron treatment daily, weekly, and twice weekly, respectively. Out of 134 children recruited for the study, only 63 (39 boys and 24 girls) completed the 3-month treatment period. All of the children received medicinal iron drops at a dosage of 5 mg elemental iron as ferrous sulfate per kilogram of body weight. The parents also received nutritional counseling. RESULTS: At the end of treatment, hemoglobin, serum ferritin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration increased significantly in all groups with no significant differences between groups. The increases in hemoglobin in groups 1, 2, and 3 were 2.47 +/- 0.17, 2.12 +/- 0.18, and 2.18 +/- 0.18 g/dL, respectively. Measurements of final serum ferritin concentration were available for only 12, 12, and 10 children in groups 1, 2, and 3, respectively. In all children who completed the study, except for one in group 1, hemoglobin, mean corpuscular volume, and serum ferritin reached normal values in response to iron treatment. CONCLUSIONS: Weekly and twice-weekly iron therapy with 5 mg elemental iron as ferrous sulfate per kilogram of body weight accompanied by nutritional counseling was as effective as daily iron therapy in correcting iron-deficiency anemia in 2- to 6-year-old children under the clinical conditions of this study.     

Determination of 14 polycyclic aromatic hydrocarbons in mainstream smoke from U.S. brand and non-U.S. brand cigarettes

Tobacco smoke contains thousands of chemical compounds, including many carcinogenic polycyclic aromatic hydrocarbons (PAHs). To determine the concentration ranges of PAHs in tobacco smoke and to understand what factors alter their levels, we quantitatively measured 14 PAHs in mainstream smoke from a transnational U.S. brand (Marlboro) and from locally popular brand cigarettes from 14 countries. We used standardized machine smoking conditions (35-mL puff volume, 60-s puff interval, and 2-s puff duration), extraction of total particulate matter from the Cambridge filters, and gas chromatography/mass spectrometry detection. Deliveries of total PAHs in mainstream smoke of local brands were statistically significantly higher (p < 0.01) than Marlboros in seven countries. In four countries, Marlboro cigarettes had mainstream smoke total PAH levels that were statistically significantly higher (p < 0.01) than local brands. In the remaining three countries, the differences in PAH levels were not statistically significant. Under standard machine smoking conditions, PAH levels were negatively correlated with cigarette filter ventilation levels. We found that several local brands containing primarily flue-cured tobacco filler had relatively high mainstream smoke PAH deliveries, in agreement with findings by previous researchers that flue-cured tobacco typically delivers more PAHs than other tobacco types. We also observed that PAHs were inversely correlated with total carcinogenic tobacco-specific nitrosamines and nitrate content, but these correlations were not statistically significant at the 95% confidence interval. The findings suggest that tobacco blend and nitrate levels may influence PAH deliveries, but other factors may confound this relation.     

70-nm-bandwidth achromatic waveguide coupler

We report a general approach to the design of broadband waveguide couplers. A double-parallel grating assembly is used to cancel the first chromatic order, and a proper choice of prism glass and base angle is made to compensate for the second chromatic order. The technique was applied to a Corning glass 7059 waveguide, and a spectral bandwidth of 70 nm was measured by the use of two complementary procedures.