Navegando por Autor "Ferreira, Sukarno Olavo"
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Item Assessment of hydrophobicity and roughness of stainless steel adhered by an isolate of Bacillus cereus from a dairy plant(Brazilian Journal of Microbiology, 2010-04-26) Bernardes, Patrícia Campos; Andrade, Nélio José de; Ferreira, Sukarno Olavo; Sá, João Paulo Natalino de; Araújo, Emiliane Andrade; Delatorre, Deyse Maria Zanom; Luiz, Lívia Maria PinheiroThe interaction between the surface of stainless steel and Bacillus cereus was studied in terms of the characteristics of interfacial interaction determined from the measurement of the contact angle of the surface of B. cereus and stainless steel in the presence or absence of B. cereus adherence. The microtopographies and the roughness of the surface of stainless steel and stainless steel adhered by B. cereus were evaluated with the help of atomic force microscopy and perfilometry. The strain of B. cereus studied was considered hydrophilic, whereas the stainless steel was considered hydrophobic. The adhesion was not thermodynamically favorable (ΔGadhesion > 0) between the stainless steel and the strain of B. cereus studied. Thus, the interaction between them was not favored by the thermodynamic aspect of adhesion. There was no difference (p > 0.05) in the roughness of the surfaces of stainless steel adhered by B. cereus when analyzed by atomic force microscope and perfilometry.Item Bactericidal activity of ethanolic extracts of propolis against Staphylococcus aureus isolated from mastitic cows(World Journal of Microbiology and Biotechnology, 2011-07-17) Santana, Henrique Freitas; Barbosa, Ana Andréa Teixeira; Ferreira, Sukarno Olavo; Mantovani, Hilário CuquettoStaphylococcus aureus is an important pathogen for both humans and animals, and it has been an ubiquitous etiological agent of bovine mastitis in dairy farms worldwide. Elimination of S. aureus with classic antibiotics is difficult, and the current study aimed to evaluate the efficacy of ethanolic extracts of propolis (EEP) against S. aureus cultivated in complex media or milk. EEP (0–0.5 mg ml^−1) decreased growth of S. aureus in BHI media and 1 mg ml^−1 was bactericidal against washed cell suspensions (10^7 CFU ml−1). Propolis extracts also killed S. aureus cells resuspended in milk, but the bactericidal dose was at least 20-fold greater. Cultures that were transferred for at least 60 generations with sub-lethal doses of propolis did not change much their sensibility to EEP. Atomic force microscopy images revealed changes in morphology and cell size of S. aureus cells exposed to EEP (0.5 mg ml^−1). Our results indicate that propolis extracts might be effective against mastitis-causing S. aureus strains in vivo, but milk constituents affect the inhibitory activity of propolis. Considering that propolis-resistance appears to be a phenotype not easily selected, the use of EEP combined or not with other antimicrobial agents might be useful for mastitis control in vivo.Item Enhanced photocatalytic activity of TiO2-impregnated with MgZnAl mixed oxides obtained from layered double hydroxides for phenol degradation(Applied Surface Science, 2015-12-01) Almeida, Marciano Fabiano de; Bellato, Carlos Roberto; Mounteer, Ann Honor; Ferreira, Sukarno Olavo; Milagres, Jaderson Lopes; Miranda, Liany Divina LimaA series of TiO2/MgZnAl photocatalysts were successfully synthesized from ternary (Mg, Zn and Al) layered double hydroxides impregnated with TiO2 nanoparticles by the co-precipitation method at variable pH with different Zn2+/Mg2+ molar ratios. The composite photocatalysts were calcined at 500 °C resulting in the incorporation of oxide zinc, in the calcined MgZnAl LDH structure. Synergistic effect between ZnO and TiO2 lead to significant enhancement of TiO2/MgZnAl photocatalytic activity. Composite photocatalysts were characterized by ICP-MS, N2 adsorption-desorption, XRD, SEM, EDS, IR and UV–vis DRS. Phenol in aqueous solution (50 mg/L) was used as a model compound for evaluation of UV–vis (filter cut-off for λ > 300 nm) photocatalytic activity. The most efficient photocatalyst composite was obtained at a 5% Zn2+/Mg2+ molar ratio, in the catalyst identified as TiO2/MgZnAl-5. This composite catalyst had high photocatalytic activity, completely destroying phenol and removing 80% of total organic carbon in solution after 360 min. The TiO2/MgZnAl-5 catalyst remained relatively stable, presenting a 15% decrease in phenol degradation efficiency after five consecutive photocatalytic cycles.Item Influence of free energy on the attachment of Salmonella Enteritidis and Listeria monocytogenes on stainless steels AISI 304 and AISI 316(LWT - Food Science and Technology, 2016-06) Ferreira, Sukarno Olavo; Casarin, Letícia Sopeña; Casarin, Fabrício de Oliveira; Brandelli, Adriano; Novello, Júnia; Tondo, Eduardo CesarBacterial attachment to stainless steels AISI (American Iron and Steel Institute) 304 and 316, the preferred material choices for food equipment, is a very important food safety consideration. The purpose of the present study was to investigate the attachment of two important food pathogens on commercial samples of these surfaces focusing on the influence of material topography characterized by Atomic Force Microscopy and considering the hydrophobicity and free energy of interaction, determined by measuring contact angle and application of thermodynamic theory principles. Results showed that S. Enteritidis and Listeria monocytogenes were able to attach to samples of stainless steels, however, initially (t = 0), the number of adhered S. Enteritidis (2.55 log CFU/cm^2) was higher than L. monocytogenes (1.68 logCFU/cm^2). Corroborating these results, the adhesion was thermodynamically more favorable for S. Enteritidis. Even though, the number of adhered cells were similar on both stainless steels samples, negative total energy was higher on AISI 316, for both bacteria. Moreover, the surface's roughness (0.032 μm and 0.021 μm) and hydrophobicity of cells and materials did not show a positive correlation with bacterial adherence.Item Morphological changes in Salmonella Typhimurium caused by the lantibiotic bovicin HC5 in association with EDTA(Annals of Microbiology, 2015-07-03) Prudêncio, Cláudia Vieira; Ferreira, Sukarno Olavo; Mantovani, Hilário Cuquetto; Vanetti, Maria Cristina DantasBacteriocins, particularly those produced by Gram-positive bacteria, have in recent years been considered promising antimicrobial agents to inhibit bacterial growth in food, and thus are potential food preservatives. These peptides generally exhibit a spectrum of action limited to Gram-positive bacteria. However, their action can be extended to Gram-negative bacteria through association with chelating agents. In the present study, we evaluated the occurrence of morphological changes on the cell envelope of Salmonella Typhimurium cells treated with bovicin HC5—a lantibiotic from Streptococcus bovis HC5—in association with EDTA. The morphological changes of the cells were visualized by atomic force microscopy (AFM), and the increase in cell membrane permeability was confirmed by the leakage of potassium ions (K+). The images displayed changes in the cell envelope, with increased surface roughness and a decreased cell volume. These changes indicate that EDTA plays a role in the destabilization of the outer membrane, allowing bovicin HC5 to act on the cytoplasmic membrane through the formation of pores, which was confirmed by the detection of potassium in the cell supernatant. These results suggest that bovicin HC5 combined with EDTA has potential for use on Salmonella cells.