scholarly journals Effect of pH on the Electrochemical Behavior of Hydrogen Peroxide in the Presence of Pseudomonas aeruginosa

2021 ◽  
Vol 9 ◽  
Author(s):  
Javier Espinoza-Vergara ◽  
Paulo Molina ◽  
Mariana Walter ◽  
Miguel Gulppi ◽  
Nelson Vejar ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Pseudomonas Aeruginosa ◽  
Enzymatic Activity ◽  
Electrochemical Behavior ◽  
Electrochemical Techniques ◽  
Stable State ◽  
Reduction Reaction ◽  
Maximum Activity ◽  
Open Circuit ◽  
Mueller Hinton

The influence of pH on the electrochemical behavior of hydrogen peroxide in the presence of Pseudomonas aeruginosa was investigated using electrochemical techniques. Cyclic and square wave voltammetry were used to monitor the enzymatic activity. A modified cobalt phthalocyanine (CoPc) carbon electrode (OPG), a known catalyst for reducing O2 to H2O2, was used to detect species resulting from the enzyme activity. The electrolyte was a sterilized aqueous medium containing Mueller-Hinton (MH) broth. The open-circuit potential (OCP) of the Pseudomonas aeruginosa culture in MH decreased rapidly with time, reaching a stable state after 4 h. Peculiarities in the E / I response were observed in voltammograms conducted in less than 4 h of exposure to the culture medium. Such particular E/I responses are due to the catalase’s enzymatic action related to the conversion of hydrogen peroxide to oxygen, confirming the authors’ previous findings related to the behavior of other catalase-positive microorganisms. The enzymatic activity exhibits maximum activity at pH 7.5, assessed by the potential at which oxygen is reduced to hydrogen peroxide. At higher or lower pHs, the oxygen reduction reaction (ORR) occurs at higher overpotentials, i.e., at more negative potentials. In addition, and to assess the influence of bacterial adhesion on the electrochemical behavior, measurements of the bacterial-substrate metal interaction were performed at different pH using atomic force microscopy.

Prediction and Measurement of Corrosion Rates of Stainless Steel in Concentrated Sulfuric Acid

CORROSION ◽  
10.5006/0709 ◽  
2013 ◽  
Vol 69 (6) ◽  
pp. 543-550 ◽  
Author(s):  
S. Jones ◽  
K. Coley ◽  
J. Kish
Keyword(s):  
Stainless Steel ◽  
Sulfuric Acid ◽  
Corrosion Behavior ◽  
Electrochemical Behavior ◽  
Open Circuit Potential ◽  
Electrochemical Techniques ◽  
Open Circuit ◽  
Corrosion Rates ◽  
Transient Nature ◽  
Concentrated Sulfuric Acid

When exposed to concentrated sulfuric acid, stainless steel exhibits unique electrochemical behavior. This behavior can be observed as an oscillation in open-circuit potential between the active and passive states. The transient nature of the corrosion behavior under these conditions results in a distinct challenge for measuring and predicting corrosion rates. Using a series of commercial alloys with various nickel contents, this paper outlines the utilization of electrochemical experimentation to refine the prediction of corrosion rates. The paper also discusses some of the difficulties associated with many traditional electrochemical techniques such as potentiodynamic scans when used for characterizing systems that undergo oscillations in open-circuit potential.

Comparison of Electrochemical Behavior of Cu-10Ni-10Zn Alloy and Cu in Aqueous Solutions

2015 ◽  
Vol 229 (3) ◽  
Author(s):  
Waheed A. Badawy ◽  
Mohamed M. El-Rabiei ◽  
Hashem M. Nady ◽  
Mohammed A. Samy
Keyword(s):  
Electrochemical Behavior ◽  
Electrochemical Impedance ◽  
Electrochemical Techniques ◽  
Pure Copper ◽  
Open Circuit ◽  
Chloride Ions ◽  
Alloy Surface ◽  
Metallic Surface ◽  
Copper Dissolution ◽  
Basic Solutions

AbstractThe electrochemical behavior of Cu-10Ni-10Zn alloy and Cu was investigated in acidic, neutral and basic solutions. The effect of chloride ions in neutral solutions was also studied. Conventional electrochemical techniques and electrochemical impedance spectroscopy were used. The corrosion rate of these materials in acidic solutions is relatively high compared to that in neutral or basic solutions. The open-circuit potential of the alloy is nearly the same as that of pure copper in the different media, indicating that the processes which occur on the alloy surface are mainly governed by copper dissolution. In chloride solutions the rate of Cu corrosion is remarkably high. In the alloy, the copper dissolution was suppressed by the presence of nickel and zinc, due to the formation of complex oxide layers. The impedance data were fitted to equivalent circuit models that explain the different electrochemical processes occurring at the electrode/electrolyte interface. SEM and EDAX have shown that the alloy surface is enriched with Ni. In neutral solutions the chloride ions are penetrating the metallic surface.

scholarly journals Ti-Mo alloys: corrosion study in solutions simulating commercial gels

2018 ◽  
Vol 1 (4) ◽  
Author(s):  
Aline Varella Rodrigues ◽  
Antonio Carlos Guastaldi
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Behavior ◽  
Photoelectron Spectroscopy ◽  
Electrochemical Techniques ◽  
Open Circuit ◽  
Promising Candidate ◽  
Fluoride Ions ◽  
Ti Alloys ◽  
Mo Content ◽  
Cp Ti

Regarding to the influence of chloride and fluoride ions on the corrosion resistance, the electrochemical behavior of Ti alloys has been deeply studied. In this work, the main goal was to investigate the electrochemical behavior of cp-Ti and Ti-Mo alloys containing 6, 10 and 15 wt% of Mo concentrations. All the samples were immersed in different solutions, such as 0.15 mol L-1 Na2SO4, 0.15 mol L-1 Ringer, 0.15 mol L-1 Ringer plus 0.036 mol L-1 NaF and 0.036 mol L-1 NaF. Simulating the commercial fluorinated gels, the NaF solutions naturally-aerated were prepared with 1450 ppm of fluoride ions. The electrochemical techniques applied in this work were the open-circuit potential, cyclic voltammetry, besides the technique for chemical identification, which was X-ray photoelectron spectroscopy. The formation and growth of TiO2 and MoO2 were identified, without pitting corrosion. The electrochemical stability and the corrosion resistance of the Ti-Mo alloys decreased in the solutions containing chloride and fluoride ions, with an appreciative decrease especially in the fluorinated medium. The Ti-Mo alloy with higher Mo content concentration was the material with higher corrosion resistance. Therefore, it is a promising candidate as a biomaterial, once the osseointegration needs a satisfactory corrosion resistance for being achieved.

ATIVIDADE ANTIMICROBIANA IN VITRO DO EXTRATO AQUOSO, HIDROALCOÓLICO E ALCOÓLICO DE FOLHAS DE ESPÉCIES DA FAMÍLIA LAMIACEAE

2018 ◽  
Vol 4 ◽  
Author(s):  
Karlynne Freire Mendonça ◽  
José Klauber Roger Carneiro ◽  
Maria Auxiliadora Silva Oliveira
Keyword(s):  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Enterococcus Faecalis ◽  
Streptococcus Pyogenes ◽  
Mentha Arvensis ◽  
Ocimum Gratissimum ◽  
Mueller Hinton ◽  
Plectranthus Amboinicus

Objetivos: avaliar a atividade antimicrobiana em extrato aquoso, hidroalcoólico e alcoólico das folhas de espécies da família Lamiaceae frente a bactérias de interesse. Método: Foram escolhidas quatro espécies: Ocimum gratissimum, Plectranthus amboinicus, Mentha arvensis e Plectranthus barbatus. A partir das folhas foram confeccionados os extratos aquoso, hidroalcoólico e alcoólico nas concentrações 100mg/mL, 50mg/mL e 25mg/mL. Foram selecionadas as bactérias Streptococcus pyogenes, Enterococcus faecalis, Staphylococcus aureus e Pseudomonas aeruginosa para os ensaios de antibiose em Ágar Mueller-Hinton. Resultados: P. barbatus, em seu extrato hidroalcoólico mostrou ativo nas três concentrações para bactéria S. aureus, e ainda foi ativo para P. aeruginosa, demonstrando no extrato alcoólico atividade frente as bactérias. Para M. arvensis e P. amboinicus, seus extratos hidroalcoólico e alcoólico apresentaram atividade para S. aureus. Conclusão: Sugere-se que as espécies em questão apresentem boa atividade antimicrobiana, sendo necessária a realização de mais estudos para melhor entender esse mecanismo.

scholarly journals Bioprocess development for enhanced endoglucanase production by newly isolated bacteria, purification, characterization and in-vitro efficacy as anti-biofilm of Pseudomonas aeruginosa

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Atef M. Ibrahim ◽  
Ragaa A. Hamouda ◽  
Noura El-Ahmady El-Naggar ◽  
Fatma M. Al-Shakankery
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Yeast Extract ◽  
Statistical Design ◽  
Life Time ◽  
Maximum Activity ◽  
Bioprocess Development ◽  
Ammonium Sulfate Precipitation ◽  
Face Centered ◽  
Central Composite

AbstractEndoglucanase producing bacteria were isolated from Egyptian soils and the most active bacterial strain was identified as Bacillus subtilis strain Fatma/1. Plackett–Burman statistical design was carried out to assess the effect of seven process variables on endoglucanase production. Carboxymethyl cellulose (CMC), yeast extract and peptone were the most significant variables that enhanced the endoglucanase production and thus were selected for further optimization using face-centered central composite design. The highest yield of endoglucanase (32.37 U/mL) was obtained in run no. 9, using 18 g/L CMC, 8 g/L peptone, 7 g/L yeast extract and 0.1 g/L FeSO4.7H2O. The optimized medium showed about eightfold increase in endoglucanase production compared to the unoptimized medium. The produced crude enzyme was further purified by ammonium sulfate precipitation, then DEAE-Sepharose CL6B column. The purified enzyme was shown to have a molecular weight of 37 kDa. The enzyme showed maximum activity at pH 8.0, temperature of 50 °C, incubation time of 60 min. The half-life time (T1/2) was 139.53 min at 50 °C, while being 82.67 min at 60 °C. Endoglucanase at concentration of 12 U/mL effectively removed 84.61% of biofilm matrix of Pseudomonas aeruginosa with marked reduction in carbohydrate content of the biofilm from 63.4 to 7.9 μg.

Application of Electrochemical Techniques to Characterization of the Corrosion Behaviors of GW63 Alloys

2007 ◽  
Vol 546-549 ◽  
pp. 571-574
Author(s):  
Xing Wu Guo ◽  
Jian Wei Chang ◽  
Shang Ming He ◽  
Peng Huai Fu ◽  
Wen Jiang Ding
Keyword(s):  
Electrochemical Impedance ◽  
Electrochemical Techniques ◽  
Open Circuit ◽  
Cyclic Polarization ◽  
Time Curve ◽  
Completely Monotonic ◽  
Treatment Conditions ◽  
Impedance Variation ◽  
Corrosion Behaviors

The corrosion behavior of GW63 (Mg-6wt.%Gd-3wt.%Y-0.4wt.%Zr) alloys in 5% NaCl aqueous solution has been investigated by PARSTAT 2273 instrument. The Open Circuit Potential (ECORR) vs. time curve, cyclic polarization (Pitting Scans) curve and Electrochemical Impedance Spectroscopy (EIS) was measured for the GW63 alloys in as-cast and T6 heat treatment conditions. The EIS results indicated that the tendency of impedance variation for as-cast condition was monotonic decreasing, however, the tendency of variation for T6 condition was not completely monotonic but the total tendency was decreasing. The values of impedance of GW63 alloy at 0.1 Hz are about 103 ohm-cm2 for as-cast and T6 condition.

Study on the Electrochemical Behavior of Ferric Stearate and its Electro-Catalytic Oxidation of Hydrogen Peroxide

2009 ◽  
Vol 610-613 ◽  
pp. 161-164
Author(s):  
Li Li Liang ◽  
Xue Gang Luo ◽  
Xiao Yan Lin
Keyword(s):  
Hydrogen Peroxide ◽  
Cyclic Voltammetry ◽  
Catalytic Oxidation ◽  
Tin Oxide ◽  
Electrochemical Behavior ◽  
Doctor Blade ◽  
Conductive Glass ◽  
Oxidation Of Hydrogen ◽  
Electro Catalytic Oxidation ◽  
Catalytic Effects

A ferric stearate electrode was made by doctor-blade methods using the Fluorine tin oxide (FTO) conductive glass. The electrochemical behavior of ferric stearate electrode was studied by the cyclic voltammetry. The electro-catalytic effects of ferric stearate on H2O2 were also investigated by cyclic voltammetry.

Pseudomonas aeruginosa transition from environmental generalist to human pathogen

2021 ◽  
Vol 13 (1) ◽  
pp. 11
Author(s):  
Gabriela Vasco ◽  
Gabriel Trueba
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Human Body ◽  
Biofilm Formation ◽  
Reduction Reaction ◽  
Human Pathogen ◽  
Opportunistic Bacteria ◽  
Oxidation Reduction ◽  
Mammalian Tissues ◽  
Oxidation Reduction Reaction ◽  
Source Sink

Opportunistic bacteria Pseudomonas aeruginosa is one of the major concerns as an etiological agent of nosocomial infections in humans. Many virulence factors used to colonize the human body are the same as those used by P. aeruginosa to thrive in the environment such as membrane transport, biofilm formation, oxidation/reduction reaction, among others. P. aeruginosa origin is mainly from the environment, the adaptation to mammalian tissues may follow a source-sink evolution model; the environment is the source of many lineages, some of them capable of adaptation to the human body. Some lineages may adapt to humans and go through reductive evolution in which some genes are lost.  The understanding of this process may be critical to implement better methods to control outbreaks in hospitals.

scholarly journals Avaliação da atividade antimicrobiana in vitro do extrato de Tabernaemontana catharinensis A. DC

2011 ◽  
Vol 13 (2) ◽  
pp. 197-202 ◽  
Author(s):  
D.M Gonçalves ◽  
J.H.B Araújo ◽  
M.S Francisco ◽  
M.A Coelho ◽  
J.M Franco
Keyword(s):  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Mueller Hinton

Diversas espécies de Tabernaemontana têm sido estudadas devido a diversidade de alcalóides com atividade farmacológica. O objetivo desse trabalho foi avaliar a capacidade antimicrobiana in vitro do extrato das cascas do caule de Tabernaemontana catharinensis A. DC.em cepas de Staphylococcus aureus e Pseudomonas aeruginosa, microrganismos causadores de diversas infecções. Os testes de susceptibilidade bacteriana foram realizados usando o método de Kirby Bauer, consistindo na difusão em disco do antibiótico em meio de cultivo Mueller Hinton. Os testes de inibição foram realizados com soluções do extrato bruto seco de T. catharinensis dissolvido em etanol 70% (v/v) na concentração 1,0 mg mL-1, que aplicada nos discos de área 20 mm², apresentaram concentração de 0,005 mg mm-2. Como controle negativo, realizou-se ensaios com placas contendo P. aeruginosa, e discos com etanol 70% (v/v), e como controle positivo, discos com os antibióticos ceftriaxona sódica (0,25 mg mm-2 de área do disco), tetraciclina (0,005 mg mm-2) e cefalexina (0,005 mg mm-2). A solução do extrato na concentração de 0,005 mg mm-2 inibiu o Staphylococcus aureus, com diâmetro médio do halo de 0,6 cm. O halo de inibição para o Pseudomonas aeruginosa foi em média 1,2 cm. A tetraciclina, a cefalexina, e o controle negativo (etanol 70% v/v) não demonstraram ação antimicrobiana. O halo de inibição usando ceftriaxona foi em média 2,2 cm para P. aeruginosa e 1,0 cm para Staphylococcus aureus.

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