RESUMO
The catalytic oxidation of phenethoxybenzene as a lignin model compound with a ß-O-4 bond was conducted using the Keggin-type polyoxometalate nanocatalyst (TBA)5[PMo10V2O40]. The optimization of the process's operational conditions was carried out using response surface methodology. The statistically significant variables in the process were determined using a fractional factorial design. Based on this selection, a central circumscribed composite experimental design was used to maximize the phenethoxybenzene conversion, varying temperature, reaction time, and catalyst load. The optimal conditions that maximized the phenethoxybenzene conversion were 137 °C, 3.5 h, and 200 mg of catalyst. In addition, under the optimized conditions, the Kraft lignin catalytic depolymerization was carried out to validate the effectiveness of the process. The depolymerization degree was assessed by gel permeation chromatography from which a significant decrease in the molar mass distribution Mw from 7.34 kDa to 1.97 kDa and a reduction in the polydispersity index PDI from 6 to 3 were observed. Furthermore, the successful cleavage of the ß-O-4 bond in the Kraft lignin was verified by gas chromatography-mass spectrometry analysis of the reaction products. These results offer a sustainable alternative to efficiently converting lignin into valuable products.
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Thermophilic bacteria able to survive extreme temperature stress are of great biotechnological interest due to their extracellular production of bioactive molecules as a part of a survival strategy, or by intracellular modifications. In the present study, thermophilic Bacillus haynesii CamB6, isolated from a Chilean hot spring, was studied for the formation of different stress response molecules. The polymeric pigment produced by the bacterial strain was characterized by different physicochemical techniques. On exposure to ranges of temperature (50-60 °C), pH (5.0-7.0), and sources of nitrogen and carbon (1-5 g·L-1), the bacteria responded with a biofilm network formation in a hydrophobic polystyrene surface. Biofilm formation under fed-batch conditions was also statistically validated. The bacteria showed a planktonic pellicle network formation in the presence of induced hypoxia and salinity stress (19.45 g·L-1) under static conditions. Salinity stress also resulted in the intracellular response of brown pigment production. The pigment was structurally and functionally characterized by UV-Vis absorbance and the presence of different characteristic peaks via FTIR analysis (bacterial pyomelanin fingerprints) were assessed. A high thermal stability and TGA profile indicated the brown pigment was a probable pyomelanin candidate. Micropyrolysis (Py-GC/MS) showed that isoprene, pyrrole, benzene, pyridine, and their derivatives were the major components detected. In addition, acetic acid, indole, phenol, and its derivatives were observed. The absence of sulfocompounds in the pyrolyzed products agreed with those reported in the literature for pyomelanin. The pigment surface morphology was analyzed via SEM, and the elemental composition via EDS also demonstrated the similarity of the brown pigment to that of the melanin family. The pyomelanin pigment was observed to be bioactive with promising antioxidant capacity (H2O2, Fe2+) compared to the standard antioxidant molecules. In conclusion, B. haynesii CamB6 demonstrated the formation of several biomolecules as a stress response mechanism that is bioactive, showing its probable biotechnological applications in future.
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Piscirickettsia salmonis is the etiological agent of piscirickettsiosis, the most prevalent disease in salmonid species in Chilean salmonids farms. Many bacteria produce N-acyl-homoserine lactones (AHLs) as a quorum-sensing signal molecule to regulate gene expression in a cell density-dependent manner, and thus modulate physiological characteristics and several bacterial mechanisms. In this study, a fluorescent biosensor system method and gas chromatography-tandem mass spectrometry (GC/MS) were combined to detect AHLs produced by P. salmonis. These analyses revealed an emitted fluorescence signal when the biosensor P. putida EL106 (RPL4cep) was co-cultured with both, P. salmonis LF-89 type strain and an EM-90-like strain Ps007, respectively. Furthermore, the production of an AHL-type molecule was confirmed by GC/MS by both P. salmonis strains, which identified the presence of a N-acetyl-L-homoserine Lactone in the supernatant extract. However, It is suggested that an alternate pathway could synthesizes AHLs, which should be address in future experiments in order to elucidate this important bacterial process. To the best of our knowledge, the present report is the first to describe the type of AHLs produced by P. salmonis.
Assuntos
4-Butirolactona , Percepção de Quorum , 4-Butirolactona/análogos & derivados , Acil-Butirolactonas , Bactérias , Cromatografia Gasosa-Espectrometria de Massas , PiscirickettsiaRESUMO
Extracellular vesicles (EVs) or exovesicles are a heterogeneous group of small cell-derived membranous structures that carry complex cargoes including lipids, proteins, RNA, and DNA. Emerging evidence suggest that EVs secreted by kinetoplastid parasites play a cardinal role in the pathogenesis of diseases they cause, becoming valuable structures for understanding parasite-host interactions. Moreover, the characterization of EVs molecular cargo may provide a new approach to develop alternative tools for diagnosis and therapy of infectious diseases. EVs have a potential use as biomarkers since it contains a repertoire of DNA species that could be detected at different stages of infection by PCR-based assays. Here, we provide a detailed protocol for the isolation of Trypanosoma cruzi-derived EVs and purification of its DNA cargo for subsequent characterization. The methods described here are transferrable to other medically important parasites that are well adapted to grow in vitro and, therefore, suitable volume of EVs-containing supernatants can be obtained.
Assuntos
Vesículas Extracelulares , Parasitos , Trypanosoma cruzi , Animais , DNA , Interações Hospedeiro-Parasita , Trypanosoma cruzi/genéticaRESUMO
The fast pyrolysis of waste tires (WTs) is studied by quasi-isothermal thermogravimetric (TGA) analysis, kinetic modelling and an analytical pyrolyzer coupled with gas chromatography/mass spectrometry (Py-GC/MS). The TGA demonstrated that the WTs pyrolysis is ruled by devolatilization/condensation and depropagation reactions, up to 482⯰C. At higher temperatures, the cyclization and aromatization of primary products take place to form mostly monoaromatics. Py-GC/MS experiments were performed under kinetic regime according to the thermal map established by the ratio between BiotÌs (31.25) and Py-numbers (7.7â 106). Limonene (51%) and isoprene (20.5%) were the major compounds detected at temperatures below 435⯰C, while above 600⯰C limonene was converted to mono-aromatics (SBTXâ¯=â¯28.7%). The approach to equilibrium of Diels-Alder reaction demonstrated that there is an equilibrium-ruled behavior between isoprene and limonene, particularly at Tâ¯>â¯600⯰C. The Ea values calculated by the Starinks model ranged from 101.5 to 176.7â¯kJ/mol, while for model-based kinetics it was 152.7â¯kJ/kmol. The integration of TGA, kinetic modelling and Py-GC/MS provided insights into pyrolysis reaction mechanism.
Assuntos
Temperatura Alta , Pirólise , Cromatografia Gasosa-Espectrometria de Massas , Cinética , TemperaturaRESUMO
Iron ligands as 1,2-dihydroxybenzenes (1,2-DHBs) have been used to increase the oxidizing ability of Fenton systems. However, these kinds of ligands become toxic quinones in the process creating an environmental problem since these compounds cannot be easily separated from a solution. To avoid this problem, in the present work, water-insoluble tannins, obtained from Pinus radiata bark, were used as a source of 1,2-DHBs to promote the oxidizing ability of the Fenton process. The developed system was tested using atrazine, as a substrate, which is a toxic and recalcitrant compound, present in different sources of water. The best reaction conditions established by the experimental design were as follows: pH of 3.6; 2.4â¯mmol L-1 of H2O2; 150⯵molâ¯L-1 of Fe(III); and 800â¯mgâ¯L-1 of tannins. A significant increase in the efficiency of the degradation of atrazine by the heterogeneous Fenton process was observed under these conditions. The repetitive use of the insoluble tannins for Fenton-like processes showed a similar oxidizing ability and did not produce the lixiviation of phenols or other aromatic compounds. Together, the results showed that insoluble tannins could be used safely at least five times to promote the reactivity of Fenton systems.
Assuntos
Atrazina/química , Catecóis/química , Poluentes Ambientais/química , Herbicidas/química , Peróxido de Hidrogênio/química , Ferro/química , Taninos/química , Pinus , Casca de PlantaRESUMO
1,2-dihydroxybenzenes (DHBs) are organic compounds which are widely studied as they are applied to advanced oxidation processes (AOPs). These compounds are also related to the development of oxidative stress, wood biodegradation, and neuronal disease in humans. DHBs are metal ligands with pro-oxidant and antioxidant properties. These activities are related to their chelation properties and a consequence of the deprotonation of their hydroxyl groups. In literature, there are several pKa values for the hydroxyl groups of DHBs. These values vary depending on the experimental conditions or the algorithm used for calculation. In this work, an experimentally validated computational method was implemented in aqueous solution for pKa determination of 24 DHBs. The deprotonation order of the hydroxyl groups in DHB was determined observing a selective deprotonation, which depended on the ability of the substituent to donate or withdraw electron density over the ring.
RESUMO
Fenton reactions driven by dihydroxybenzenes (DHBs) have been used for pollutant removal via advanced oxidation processes (AOPs), but such systems have the disadvantage of DHB release into the aqueous phase. In this work, insoluble tannins from bark can be used to drive Fenton reactions and as a heterogeneous support. This avoids the release of DHBs into the aqueous phase and can be used for AOPs. The production of ·OH was investigated using a spin-trapping electron paramagnetic resonance technique (5-dimethyl-1-pyrroline-N-oxide/·OH) in the first minute of the reaction and a high-performance liquid chromatography-fluorescence technique (coumarin/7-hydroxycoumarin) for 20 min. The ·OH yield achieved using insoluble tannins from Pinus radiata bark was higher than that achieved using catechin to drive the Fenton reaction. The Fenton-like system driven by insoluble tannins achieved 92.6 ± 0.3 % degradation of atrazine in 30 min. The degradation kinetics of atrazine was linearly correlated with ·OH production. The increased reactivity in ·OH production and insolubility of the ligand are promising for the development of a new technique for degradation of pollutants in wastewater using heterogeneous Fenton systems.
Assuntos
Derivados de Benzeno , Poluentes Ambientais , Radical Hidroxila , Pinus/química , Taninos , Derivados de Benzeno/análise , Derivados de Benzeno/química , Poluentes Ambientais/análise , Poluentes Ambientais/química , Poluentes Ambientais/isolamento & purificação , Recuperação e Remediação Ambiental , Radical Hidroxila/análise , Radical Hidroxila/química , Solubilidade , Taninos/análise , Taninos/químicaRESUMO
Introducción. Las infecciones por Staphylococcus aureus meticilino resistente adquirido en la comunidad son un problema grave y frecuente en pediatría. Objetivo. Describir la resistencia a los antibióticos enlas infecciones bacteriémicas por Staphylococcus aureus (SA) de la comunidad. Comparar las características de las infecciones bacteriémicas por SA según la resistencia a la meticilina. Material y métodos. Cohorte prospectiva entre enero de 2010 y diciembre de 2014. Criterios de inclusión: niños de entre 30 días y 16 años de edad hospitalizados en el Hospital de Pediatría J. P. Garrahan por infecciones adquiridas en la comunidad, con desarrollo de SA en hemocultivos. Criterios de exclusión: antecedente de internación reciente, asistencia a un centro relacionado con los cuidados de la salud, vivir en una comunidad cerrada o catéter venoso. Se compararon características microbiológicas, demográficas y clínicas según la sensibilidad a la meticilina. Análisis estadístico: Stata10. Resultados. Se incluyeron 208 niños; varones: 141 (68%). La mediana de edad fue 60 meses (rango intercuartilo 29-130). Tenían enfermedad de base 34 pacientes (16%). En 136 niños (65%), se identificó Staphylococcus aureus meticilino resistente. La resistencia a la clindamicina fue 9%. Se encontraron diferencias estadísticas significativas en la frecuencia de enfermedad subyacente, bacteriemia persistente, sepsis al momento del ingreso, foco secundario de infección, ingreso a unidades de cuidados intensivos y necesidad de cirugía. Fallecieron 12 pacientes (6%); todos tuvieron identificación de Staphylococcus aureus meticilino resistente adquirido en la comunidad. Conclusiones. En la cohorte estudiada, predominó el Staphylococcus aureus meticilino resistente. La resistencia a la clindamicina fue del 9%. Las infecciones por Staphylococcus aureus meticilino resistente adquirido en la comunidad predominaron en niños sanos. En los pacientes con Staphylococcus aureus meticilino resistente, fue más frecuente la bacteriemia persistente, el ingreso a unidades de cuidados intensivos y la cirugía.
Introduction. Community-acquired methicillin-resistant Staphylococcus aureus infections are a common, serious problem in pediatrics.Objective. To describe antibiotic resistance in community-acquired Staphylococcus aureus (SA) bacteremias. To compare the characteristics of SA bacteremias in terms of methicillin resistance.Material and methods. Prospective cohort enrolled between January 2010 and December 2014. Inclusion criteria: infants and children between 30 days old and 16 years old hospitalized at the Hospital de Pediatría J. P. Garrahan due to community-acquired infections with SA growth identification in blood cultures. Exclusion criteria: having a history of recent hospitalization, attending a health care facility, living in a closed community, or having a venous catheter. Microbiological, demographic, and clinical characteristics were compared in terms of methicillin susceptibility. Statistical analysis: Stata10.Results. A total of 208 children were included; boys: 141 (68%). Their median age was 60 months old (interquartile range: 29-130). Thirty-four patients (16%) had an underlying disease. Methicillin-resistant Staphylococcus aureus was identified in 136 children (65%). The rate of resistance to clindamycin was 9%. Significant statistical differences were observed in the rate of underlying disease, persistent bacteremia, sepsis at the time of admission, secondary source of infection, admission to the intensive care unit, and surgery requirement. Twelve patients (6%) died; community-acquired methicillin-resistant Staphylococcus aureus was identified in all of them.Conclusions. In the studied cohort, methicillin-resistant Staphylococcus aureus was predominant. The rate of resistance to clindamycin was 9%. Community-acquired methicillin-resistant Staphylococcus aureus infections prevailed among healthy children. Among patients with methicillin-resistant Staphylococcus aureusinfections there was a higher rate of persistent bacteremia, admission to the ICU and surgery
Assuntos
Humanos , Masculino , Lactente , Pré-Escolar , Criança , Adolescente , Infecções Estafilocócicas/microbiologia , Infecções Estafilocócicas/tratamento farmacológico , Staphylococcus aureus/efeitos dos fármacos , Bacteriemia/microbiologia , Bacteriemia/tratamento farmacológico , Fatores de Tempo , Testes de Sensibilidade Microbiana , Estudos de Coortes , Infecções Comunitárias Adquiridas/microbiologia , Infecções Comunitárias Adquiridas/tratamento farmacológico , Staphylococcus aureus Resistente à MeticilinaRESUMO
INTRODUCTION: Community-acquired methicillin-resistant Staphylococcus aureus infections are a common, serious problem in pediatrics. OBJETIVE: To describe antibiotic resistance in community-acquired Staphylococcus aureus (SA) bacteremias. To compare the characteristics of SA bacteremias in terms of methicillin resistance. MATERIALS AND METHODS: Prospective cohort enrolled between January 2010 and December 2014. Inclusion criteria: infants and children between 30 days old and 16 years old hospitalized at the Hospital de Pediatria J. P. Garrahan due to community-acquired infections with SA growth identification in blood cultures. Exclusion criteria: having a history of recent hospitalization, attending a health care facility, living in a closed community, or having a venous catheter. Microbiological, demographic, and clinical characteristics were compared in terms of methicillin susceptibility. Statistical analysis: Stata10. RESULTS: A total of 208 children were included; boys: 141 (68%). Their median age was 60 months old (interquartile range: 29-130). Thirty-four patients (16%) had an underlying disease. Methicillin-resistant Staphylococcus aureus was identified in 136 children (65%). The rate of resistance to clindamycin was 9%. Significant statistical differences were observed in the rate of underlying disease, persistent bacteremia, sepsis at the time of admission, secondary source of infection, admission to the intensive care unit, and surgery requirement. Twelve patients (6%) died; community-acquired methicillin-resistant Staphylococcus aureus was identified in all of them. CONCLUSIONS: In the studied cohort, methicillin-resistant S taphylococcus aureus was predominant. The rate of resistance to clindamycin was 9%. Community-acquired methicillin-resistant Staphylococcus aureus infections prevailed among healthy children. Among patients with methicillin-resistant Staphylococcus aureus infections there was a higher rate of persistent bacteremia, admission to the ICU and surgery.
INTRODUCCIÓN: Las infecciones por Staphylococcus aureus meticilino resistente adquirido en la comunidad son un problema grave y frecuente en pediatría. OBJETIVO: Describir la resistencia a los antibióticos enlas infecciones bacteriémicas por Staphylococcus aureus (SA) de la comunidad. Comparar las características de las infecciones bacteriémicas por SA según la resistencia a la meticilina. Material y métodos. Cohorte prospectiva entre enero de 2010 y diciembre de 2014. Criterios de inclusión: niños de entre 30 días y 16 años de edad hospitalizados en el Hospital de Pediatría J. P. Garrahan por infecciones adquiridas en la comunidad, con desarrollo de SA en hemocultivos. Criterios de exclusión: antecedente de internación reciente, asistencia a un centro relacionado con los cuidados de la salud, vivir en una comunidad cerrada o catéter venoso. Se compararon características microbiológicas, demográficas y clínicas según la sensibilidad a la meticilina. Análisis estadístico: Stata10. RESULTADOS: Se incluyeron 208 niños; varones: 141 (68%). La mediana de edad fue 60 meses (rango intercuartilo 29-130). Tenían enfermedad de base 34 pacientes (16%). En 136 niños (65%), se identificó Staphylococcus aureus meticilino resistente. La resistencia a la clindamicina fue 9%. Se encontraron diferencias estadísticas significativas en la frecuencia de enfermedad subyacente, bacteriemia persistente, sepsis al momento del ingreso, foco secundario de infección, ingreso a unidades de cuidados intensivos y necesidad de cirugía. Fallecieron 12 pacientes (6%); todos tuvieron identificación de Staphylococcus aureus meticilino resistente adquirido en la comunidad. CONCLUSIONES: En la cohorte estudiada, predominó el Staphylococcus aureus meticilino resistente. La resistencia a la clindamicina fue del 9%. Las infecciones por Staphylococcus aureus meticilino resistente adquirido en la comunidad predominaron en niños sanos. En los pacientes con Staphylococcus aureus meticilino resistente, fue más frecuente la bacteriemia persistente, el ingreso a unidades de cuidados intensivos y la cirugía.
Assuntos
Bacteriemia/tratamento farmacológico , Bacteriemia/microbiologia , Infecções Estafilocócicas/tratamento farmacológico , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/efeitos dos fármacos , Criança , Pré-Escolar , Estudos de Coortes , Infecções Comunitárias Adquiridas/tratamento farmacológico , Infecções Comunitárias Adquiridas/microbiologia , Feminino , Humanos , Masculino , Staphylococcus aureus Resistente à Meticilina , Testes de Sensibilidade Microbiana , Fatores de TempoRESUMO
Staphylococcus aureus es uno de los principales agentes etiológicos de infecciones en niños provenientes de la comunidad y del ámbito hospitalario. La gravedad de estos cuadros se asocia a factores de virulencia, entre los que se encuentra la leucocidina de Panton-Valentine. Tanto Staphylococcus aureus resistente como sensible a la meticilina producen esta leucocidina, aunque con frecuencia variable. Presentamos a dos niños con infección grave por Staphylococcus aureus sensible a la meticilina productor de leucocidina de Panton-Valentine con complicaciones osteoarticulares y endovasculares. Es fundamental la sospecha diagnóstica, el tratamiento antibiótico adecuado y el manejo quirúrgico precoz para mejorar el abordaje de estas infecciones. Se debe mantener la vigilancia epidemiológica para detectar la frecuencia de las infecciones causadas por estas bacterias.
Staphylococcus aureus is a major etiologic agent of infections in children from the community and the hospital setting. The severity of these conditions is associated with virulence factors, including the Panton-Valentine leukocidin. Both methicillin resistant and sensitive Staphylococcus aureus produce this leukocidin although with varying frequency. We present two children with severe infection by sensitive Staphylococcus aureus producer of Panton-Valentine leukocidin with musculoskeletal and endovascular complications. It is essential the suspected diagnosis, appropriate antibiotic treatment and early surgical management to improve the approach of these infections. Epidemiological surveillance should be mantained to detect the frequency of infections caused by these bacteria.
Assuntos
Humanos , Masculino , Feminino , Criança , Infecções Estafilocócicas/diagnóstico , Infecções Estafilocócicas/microbiologia , Infecções Estafilocócicas/terapia , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/metabolismo , Toxinas Bacterianas/biossíntese , Exotoxinas/biossíntese , Leucocidinas/biossíntese , Meticilina/farmacologia , Antibacterianos/farmacologia , Índice de Gravidade de Doença , Testes de Sensibilidade MicrobianaRESUMO
Staphylococcus aureus is a major etiologic agent of infections in children from the community and the hospital setting. The severity of these conditions is associated with virulence factors, including the Panton-Valentine leukocidin. Both methicillin resistant and sensitive Staphylococcus aureus produce this leukocidin although with varying frequency. We present two children with severe infection by sensitive Staphylococcus aureus producer of Panton-Valentine leukocidin with musculoskeletal and endovascular complications. It is essential the suspected diagnosis, appropriate antibiotic treatment and early surgical management to improve the approach of these infections. Epidemiological surveillance should be mantained to detect the frequency of infections caused by these bacteria.
Staphylococcus aureus es uno de los principales agentes etiológicos de infecciones en niños provenientes de la comunidad y del ámbito hospitalario. La gravedad de estos cuadros se asocia a factores de virulencia, entre los que se encuentra la leucocidina de Panton-Valentine. Tanto Staphylococcus aureus resistente como sensible a la meticilina producen esta leucocidina, aunque con frecuencia variable. Presentamos a dos niños con infección grave por Staphylococcus aureus sensible a la meticilina productor de leucocidina de Panton-Valentine con complicaciones osteoarticulares y endovasculares. Es fundamental la sospecha diagnóstica, el tratamiento antibiótico adecuado y el manejo quirúrgico precoz para mejorar el abordaje de estas infecciones. Se debe mantener la vigilancia epidemiológica para detectar la frecuencia de las infecciones causadas por estas bacterias.