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141.
Human milk samples from three healthy donors were investigated in order to evaluate the antibacterial activity during lactation against Escherichia coli ATCC 25922 and Listeria monocytogenes. The concentration of the main human-milk antimicrobial proteins (lactoferrin (LF), lysozyme (LZ) and secretory immunoglobulin A (sIgA)) was determined by ELISA. Results showed that human milk exhibited antibacterial activity against List. monocytogenes, although it was weakly active against Esch. coli ATCC 25922. The observed antilisterial activity was positively correlated with LZ concentration. In addition, the effect of gastrointestinal proteases, at different pH conditions, that prevail in the stomach of infants (pH 2.0-6.5), on antilisterial activity and protein degradation was evaluated. Hydrolysis with pepsin at pH 4.0-6.5, followed by treatment with pancreatic enzymes, resulted in a decreased hydrolysis of LZ, LF and sIgA and an enhanced antibacterial activity against List. monocytogenes. It is suggested that partial degradation of certain milk proteins at the gastrointestinal level may produce peptides that could act synergistically with the remnant intact proteins. 相似文献
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Antimicrobial peptides derived from food proteins constitute a new field in the combined use of antimicrobial agents in food. The best examples of milk-derived peptides are those constituted by bovine lactoferricin [lactoferrin f(17-41)] (LFcin-B) and bovine αs2-casein f(183-207). The aim of this work was to study if the antimicrobial activity of a natural compound employed in food preservation, nisin, could be enhanced by combination with the aforementioned milk-derived peptides. Furthermore, the possibility of a synergistic effect between these peptides and bovine lactoferrin (LF) against Escherichia coli and Staphylococcus epidermidis was also studied. Finally, the most active combinations were assayed against the foodborne pathogens Listeria monocytogenes and Salmonella choleraesuis. Results showed a synergistic effect when LFcin-B was combined with bovine LF against E. coli. In the same way, the combination of LFcin-B with bovine LF was synergistic against Staph. epidermidis. Bovine LF and nisin increased their antimicrobial activity when they were assayed together with bovine αs2-casein f(183-207). It is important to note the synergistic effect among LFcin-B and bovine LF, because both compounds might be simultaneously in the suckling gastrointestinal tract and could, therefore, have a protective effect on it. The other synergistic effect high-lighted is that between αs2-casein f(183-207) and nisin against L. monocytogenes because of the ability of L. monocytogenes to develop resistance to nisin. 相似文献
143.
Andressa Cristina de Mattos Bezerra Danieli de Oliveira Silva Gustavo Henrique Machado de Matos Josuel Pereira dos Santos Jr. Claudio Neves Borges 《仪器科学与技术》2019,47(1):90-106
Raman spectroscopy can be used to evaluate the quality of fuels in a remote, rapid, and nondestructive manner without the need for reagents. In this study, Raman was used to quantify anhydrous ethanol in commercial gasoline and to detect peaks due to compounds commonly used for the adulteration of commercial gasoline. Samples of commercial gasoline were collected from fuel stations in the region of Santos, SP, Brazil. Samples of naphtha from the refinery, pure ethanol, and ethanol diluted in distilled water at concentrations close to the range used in the gasoline were also obtained and characterized. Raman spectra were collected using a dispersive Raman spectrometer (830?nm, 2?cm?1 resolution in the 400–1800?cm?1 spectral range). As expected, the spectra of commercial gasoline showed pronounced peaks of naphtha and ethanol. By using the peak intensities of the ethanol diluted in water, the ethanol concentration was found to be in the range of 27%?±?1% in most of the samples; some samples presented ethanol concentrations as high as 28.8%, suggesting adulteration. Some samples presented peaks at 766, 798, and 995?cm?1 with higher intensities, suggesting the presence of an adulterant with organic characteristics, such as solvents with aromatic rings. Raman spectroscopy has been shown to be effective in determining the adulteration of commercial gasoline, which may contribute to rapid quality control of fuels at the point of sale. 相似文献
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Assessment of heavy metals remobilization by fractionation: comparison of leaching tests applied to roadside sediments 总被引:1,自引:0,他引:1
The pollution emitted by traffic activities and road maintenance is an area of great interest as contaminants can be transported to roadside sediments and pose a risk to environmental and human health. In the presentwork, deposited pollution in roadside sediments has been assessed by sampling along a highly traveled highway in Barcelona and the surrounding area. The available amounts of the heavy metals was determined by applying different leaching tests and calculating the concentration enrichment ratio (CER) and the environmental concentration guideline values (ECG). To gain information on the heavy metals (HMs) fractionation, the sequential extraction scheme (SES), established by the Standard Measurement and Testing (SM&T), was implemented, and the results were compared with those obtained by single leaching tests. An anthropogenic enhancement of certain metals was observed after considering both the CER and ECG values. However, if only ECG values were considered, an overestimation of the anthropogenically enhanced pollutants was obtained due to disregarding geochemical and particle size variability. CER values provide a more realistic assessment by determining different levels of anthropogenic impact. Thus, CER values suggest a minimum anthropogenic apportion for metals such as Cd, Cr, and Ni, whereas different situations from significant to extreme anthropogenic contribution were observed for Zn, Pb, and Cu. These results have been complemented by other leaching tests that minimize the time-consuming environmental evaluation. In this study, HCI extraction produces suitable results for a quick screening since they correlate well with the corresponding SES: Cu(r2 = 0.798), Pb(r2 = 0.958) and Zn(r2 = 0.901). Mild extractants have been observed to be limited to highly polluted samples due to their low leaching power. The information obtained following this procedure helps to identify hazardous areas that need a remedial strategy. 相似文献
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Roberta Bastos Vasques Marjory Moreira Levy Matheus Souza Rodrigues Francisco Wagner de Queiroz Almeida Neto Leonardo Paes da Silva Gustavo Leitão Vaz Álvaro Augusto Oliveira Magalhães Pedro de Lima-Neto Walney Silva Araújo 《工业材料与腐蚀》2021,72(8):1417-1432
Phosphate ester was investigated as a corrosion inhibitor for AISI 1018 carbon steel in carbon dioxide-saturated chloride solutions at different temperatures and pressures. The corrosion tests were realized by electrochemical techniques, weight loss measurements, bubble tests, and a high-pressure/high-temperature autoclave system. The corrosion tests demonstrated that the investigated molecule is an excellent corrosion inhibitor. The inhibiting effect is even bigger at high pressure and temperature than at atmospheric pressure and room temperature. The thermodynamic parameters were calculated and determined to obey the Langmuir isotherm. Polarization studies revealed that the evaluated inhibitor is a mixed type. 相似文献
150.
de Siqueira Gustavo Oliveira Canuto Sérgio Gonçalves Marcos André Laender Alberto H. F. 《International Journal on Digital Libraries》2020,21(1):61-73
International Journal on Digital Libraries - Throughout the history of science, different knowledge areas have collaborated to overcome major research challenges. The task of associating a... 相似文献