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This study investigates the effects of different strategies on poly(3-hydroxybutyrate)-P(3HB) production in a fed-batch bioreactor by Bacillus megaterium using candy industry effluent (CIE), sucrose, and rice parboiled water (RPW) as carbon sources. In biosynthesis, kinetic and stoichiometric parameters of substrate conversion into products and/or cells, productivity, instantaneous, and specific conversion rates were evaluated. The maximum concentration of P(3HB) was 4.00 g.L-1 (77% of the total dry mass) in 42 h of cultivation in minimal medium/RPW added with a carbon source based on CIE, demonstrating that the fed-batch provided an increase of approximately 22% in the polymer concentration and 32% in the overall productivity in relation to medium based on commercial sucrose. Fed-batch cultivation also had the advantage of avoiding the extra time required for inoculum preparation and sterilization of the bioreactor during the batch, which thereby increased the overall industrial importance of the process. Effluents from the candy, confectionery, and/or rice parboiling industries can be used as alternative substrates for P(3HB) production at a low cost.
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Bacillus megaterium , Ácido 3-Hidroxibutírico , Carbono , Poliésteres , Reatores Biológicos , Sacarose , HidroxibutiratosRESUMO
The use of the USP IV apparatus (flow-through cell) has gained acceptance in recent years due to its versatility and ability to discriminate due to its hydrodynamic conditions. Therefore, the objective of the present study was to develop a discriminative dissolution method in the USP IV apparatus using the open-loop configuration, as well as to propose a method to compare non-cumulative dissolution profiles obtained in the open-loop configuration considering kinetic parameters and validate its predictive power through its comparison with independent and dependent methods using five commercial immediate-release tablet drugs (one reference drug and four generic drugs) of metoprolol tartrate as a model drug. The comparison of the non-accumulated dissolution profiles consisted of determining the geometric ratio of Cmax, AUC0∞, AUC0Cmax, and Tmax (kinetic parameters) of the generic/reference drugs, whereby generic drugs "C" and "D" presented the highest probability of similarity since their 90% confidence intervals were included, or they were very close to the acceptance interval (80.00-125.00%). These results were consistent with the f2, bootstrap f2, and dissolution efficiency approaches (independent models). In conclusion, the proposed comparison method can be an important tool to establish similarity in dissolution profiles and to facilitate the development/selection of new formulations and positively ensure bioequivalence in clinical studies.
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Sulfate-rich effluents have been successfully treated in anaerobic reactors using sulfate-reducing bacteria (SRB). Many authors have demonstrated that these systems require nitrogen and phosphorous supplementation to achieve high sulfate removal rates. However, the resource ratio theory assumes that some species can be dominant according to the nutritional relations used or even without external nutrient supplementation. Thus, this study evaluated the SRB communities in batch reactors without external nitrogen and phosphorus sources based on most probable number (MPN) quantification, denaturing gradient gel electrophoresis (DGGE) analyses and sequencing. The sulfate and chemical oxygen demand (COD) removal and kinetic parameters were also determined. After 100 days of operation, the sulfate and COD removal achieved 71.8 ± 10% and 86.5 ± 10%, respectively. The SRB population increased from 8.106 to 4 × 1012 MPN 100 mL-1, and the richness of SRB bands was much higher at the end of the experiment compared to the inoculum. In addition, the sequenced bands from SRB-DGGE showed similarities to Desulfacinum infernum, Desulfobulbus sp, Syntrophobacter and Desulfomicrobium aestuarii-related sequences. Therefore, biological treatment of acid mine drainage wastewater was effective in the absence of nutrients, lowering costs and providing high sulfate removal efficiency.
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Nitrogênio , Sulfatos , Sulfatos/química , Anaerobiose , Reatores Biológicos/microbiologia , Águas Residuárias , FósforoRESUMO
Laccases are valuable enzymes as an excellent ecological alternative for bioremediation issues because they can oxidize persistent xenobiotic compounds. The production and characterization of extracellular laccases from saprotrophic fungi from disturbed environments have been scarcely explored, even though this could diversify their functional characteristics and expand the conditions in which they carry out their catalysis. Agrocybe pediades, isolated from a disturbed forest, produces an extracellular laccase in liquid culture. The enzyme was purified, identified and characterized. Copper and hexachlorobenzene do not function as inducers for the laccase produced. Partial amino acid sequences were obtained by LC-MS/MS that share similarity with laccases from other fungi. Purified laccase is a monomer with a molecular mass between 55-60 kDa and had an optimum activity at pH 5.0 and the optimum temperature at 45 °C using 2,6-dimethoxyphenol (2,6-DMP) as substrate. The Km and Vmax also determined with 2,6-DMP were 100 µM and 285 µmolâmin-1âmg-1, respectively, showing that the laccase of A. pediades has a higher affinity for this substrate than that of other Agaricales. These features could provide a potential catalyst for different toxic substrates and in the future laccase could be used in environmental recovery processes.
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Laccase is a versatile enzyme widely used for the oxidation of environmental contaminants and exhibits great potential in many others applications; however, it undergoes photo-degradation when irradiated with UVB light. The photo-stability of this biomolecule can be improved by immobilization in different encapsulation media and reverse micelles have been employed with this purpose. The laccase activity using syringaldazine as substrate has been studied in the absence and in the presence of reverse micelles of 0.15 M of sodium 1,4-bis (2-ethylhexyl) sulfosuccinate (AOT) in isooctane at W0 ([H2O]/[AOT]) = 30, before and after irradiation of the enzyme with UVB light. The kinetic parameters, i.e., Michaelis-Menten constant (KM), catalytic constant (kCAT), and catalytic efficiency (kCAT/KM), were determined by spectroscopic measurements in the micellar system and in homogeneous aqueous medium. The distribution of the substrate in two pseudo-phases (micelle and organic solvent) was taking into account in the kinetic parameters' determinations. The results obtained indicate that the nano-aggregate system confers a solubilization media in the water core of the micelle, both for the enzyme and the substrate, in which the catalytic function of the enzyme is preserved. On the other hand, in homogeneous aqueous medium kCAT/KM value, it is reduced by ~50% after UVB irradiation of the enzyme, while in micellar medium, less than 10% of the activity was affected. This mean that the enzyme achieves a considerably photo-protection when it is irradiated with UVB light in reverse micelles as compared with the homogeneous aqueous medium. This phenomenon can be mainly due to the confinement of the biomolecule inside the micelle. Physical properties of the nano-environment could affect photochemical reactions.
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Lacase , Micelas , Raios Ultravioleta , Água/química , Solventes , CinéticaRESUMO
Glucokinase (GCK) is the pancreatic ß-cell glucose sensor, and its kinetics are key to that purpose. A slow transition step, displayed as non-hyperbolic kinetics, and a low affinity for glucose characterize GCK. Mutations in GCK associated with maturity-onset diabetes of the young type 2 (MODY2) previously described reduce the functionality of the human pancreatic ß-cell, leading to diabetic clinical phenotypes. We present a kinetic characterization of the G448D mutation identified in a MODY2 patient, which is one of the first mutations to exhibit increased functionality. This mutant displays increased activity, high affinity for both Mg2+ -ATP and glucose, hyperbolic kinetics and increased phosphorylation potential. Hyperbolic kinetics and assays in the presence of glycerol indicate that G448D lacks the slow transition step crucial for the pancreatic ß-cell glucose sensor function.
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Diabetes Mellitus Tipo 2 , Glucoquinase , Humanos , Glucoquinase/genética , Mutação , Diabetes Mellitus Tipo 2/genética , GlucoseRESUMO
The effect that the fructans of Cichorium intybus and Agave salmiana have on health, as well as on the growth of some Lactobacillus species, has been demonstrated. The aim of this work was to evaluate the effect of linear and branched fructans on the growth of seven strains and some probiotic characteristics. The molecular identification of seven strains was performed. Moreover, the growth, resistance to antibiotics and simulated gastrointestinal conditions were also evaluated when these microorganisms were grown in a culture medium containing agave and chicory fructans. The strains were identified as Lactiplantibacillus plantarum, Lactiplantibacillus pentosus, Lactiplantibacillus fabifermentans and Lactiplantibacillus paraplantarum. The results suggest that the seven Lactobacillus strains were able to grow using agave (branched) and chicory (linear) fructans. The linear and branched fructans statistically influenced the kinetic parameters. The specific growth rate varied between 0.270 and 0.573 h-1 and the generation time between 1.21 and 2.45 h for all strains and culture media. All strains showed a growth of 9 Log CFU/mL in all the culture media. Production of lactic, acetic, propionic, butyric, formic and succinic acid was influenced by linear and branched fructans (p < 0.05). All the strains survived simulated gastrointestinal conditions greater than 83%. The resistance of Lactobacillus against ciprofloxacin and rifaximin was significantly affected by linear and branched fructans, but survival to gastrointestinal conditions was not affected by the type of substrate. These results highlight the use of the seven strains, which have probiotic potential; therefore, these could be applied in several biotechnological products.
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Agave , Probióticos , Agave/química , Bebidas , Meios de Cultura , Frutanos/química , Lactobacillus , MéxicoRESUMO
In this study, the kinetic parameters belonging to the cross-linking process of a modified epoxy resin, Aerotuf 275-34™, were investigated. Resin curing kinetics are crucial to understanding the structure-property-processing relationship for manufacturing high-performance carbon-fiber-reinforced polymer composites (CFRPCs). The parameters were obtained using differential scanning calorimetry (DSC) measurements and the Flynn-Wall-Ozawa, Kissinger, Borchardt-Daniels, and Friedman approaches. The DSC thermograms show two exothermic peaks that were deconvoluted as two separate reactions that follow autocatalytic models. Furthermore, the mechanical properties of produced carbon fiber/Aerotuf 275-34™ laminates using thermosetting polymers such as epoxies, phenolics, and cyanate esters were evaluated as a function of the conversion degree, and a close correlation was found between the degree of curing and the ultimate tensile strength (UTS). We found that when the composite material is cured at 160 °C for 15 min, it reaches a conversion degree of 0.97 and a UTS value that accounts for 95% of the maximum value obtained at 200 °C (180 MPa). Thus, the application of such processing conditions could be enough to achieve good mechanical properties of the composite laminates. These results suggest the possibility for the development of strategies towards manufacturing high-performance materials based on the modified epoxy resin (Aerotuf 275-34™) through the curing process.
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The presence of antibiotic residues in drinking water may be a source of contamination, which could affect the diffusion of polyphenols into the wine must during the traditional fermentation process. Antibiotic residues such as ivermectin, hydroxychloroquine, ciprofloxacin, and azithromycin on the diffusion of polyphenols and anthocyanins during wine fermentation were studied. Different samples were taken at different periods (0, 48, 96, and 168 h) to analyse the total polyphenols, anthocyanin content, and antioxidant capacity, which were correlated with Peleg's equation to establish the diffusion kinetics of these compounds. The results indicated that the presence of antibiotics reduced between 40 and 50% the diffusion of the total polyphenols and monomeric anthocyanins in red wine. The use of ivermectin showed the highest kinetic parameter k1 compared with the use of other antibiotics. This suggested that the chemical structure and molecular weight of the antibiotics could play an important role in inhibiting the metabolism of yeasts affecting the ethanol and CO2 production. Consequently, cell membranes would be impermeable and would not allow the release of polyphenols and anthocyanins. Therefore, it is necessary to establish strategies that allow future water quality control in wine production companies.
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Água Potável , Vinho , Antioxidantes/química , Vinho/análise , Antocianinas/química , Água Potável/análise , Antibacterianos/farmacologia , Antibacterianos/análise , Ivermectina/análise , Polifenóis/análiseRESUMO
This study presents a kinetic determination of copper removal from a real jewelry industry wastewater, with removal reaching 82.49% at 37°C, using fast galvanic pulse electrochemical technique in a process lasting 115 min. In the temperature range from 20 to 40°C, the mathematical model of the pseudo-first-order irreversible rate equation, with a correlation coefficient of 0.99, described the process behaviour. In this same temperature range, the Arrhenius' equation described the system, in which the temperature increase favoured the reaction kinetics. The scanning electron microscope (SEM), with energy-dispersive X-ray detector (EDX), X-ray photoelectron spectroscopy (XPS) results, and the mathematical model fitting at the temperatures of 10 and 50°C indicated the formation of copper oxide I.
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Galvanoplastia , Águas Residuárias , Adsorção , Cobre , CinéticaRESUMO
This study quantified K uptake kinetic parameters in grass species Paspalum notatum, Paspalum urvillei and Axonopus affinis to associate them with growth. Ten milliliters (10 ml) of nutrient solution were collected in two-liter pots - with five repetitions in 24 hours - in order to determine K concentrations in the samples. Shoot and root dry matter, root length, volume, diameter and surface area, as well as kinetic parameters associated with nutrient uptake (Vmax, Km, Cmin and I) were determined. Species P. notatum was the one presenting the highest root, shoot and total dry matter production, as well as the highest root volume. P. urvillei recorded the highest K content, which may be associated with thinner roots and greater root surface area. A. affinis recorded the highest Vmax value, which led to greater K uptake efficiency.
O estudo quantificou os parâmetros cinéticos de captação de K nas gramíneas Paspalum notatum, Paspalum urvillei e Axonopus affinis associados com o crescimento. Dez mililitros (10 ml) de solução nutritiva foram coletados em vasos de dois litros - com cinco repetições em 24 horas - para determinação das concentrações de K nas amostras. A matéria seca da parte aérea e raízes; comprimento, volume, diâmetro e área superficial radicular, bem como parâmetros cinéticos associados à absorção de nutrientes (Vmax, Km, Cmin e I) foram avaliados. A espécie P. notatum apresentou a maior produção de raiz, parte aérea e MS total, bem como o maior volume de raiz. P. urvillei apresentou o maior teor de K, que pode ser associado a raízes mais finas e resultando em maior área superficial. A. affinis registrou o maior valor de Vmax, o que levou a uma maior eficiência de absorção de K.
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Potássio/administração & dosagem , Nutrientes/análise , Paspalum/químicaRESUMO
Currently, the pyrolysis process is an important technology for the final treatment of plastic waste worldwide. For this reason, knowing in detail the chemical process and the thermodynamics that accompany cracking reactions is of utmost importance. The present study aims to determine the thermodynamic parameters of the degradation process of conventional thermoplastics (polystyrene (PS), polyethylene terephthalate (PET), high-density polyethylene (HDPE), polypropylene (PP) and polyvinyl chloride (PVC)) from the study of their chemical kinetics by thermogravimetric analysis (TG). Non-isothermal thermogravimetry was performed at three heating rates from room temperature to 550 °C with an inert nitrogen atmosphere with a flow of 20 mL min-1. Once the TG data is obtained, an analysis is carried out with the isoconversional models of Friedman (FR), Kissinger-Akahira-Sunose (KAS), and Flynn-Wall-Ozawa (FWO) in order to determine the one that best fits the experimental data, and with this, the calculation of the activation energy and the pre-exponential factor is performed. The validation of the model was carried out using the correlation factor, determining that the KAS model is the one that best adjusts for the post-consumer thermoplastic degradation process at the three heating rates. With the use of the kinetic parameters, the variation of the Gibbs free energy is determined in each of the cases, where it is necessary that for structures containing aromatic groups a lower energy is presented, which implies a relative ease of degradation compared to the linear structures.
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We developed a web application structured in a machine learning and molecular fingerprint algorithm for the automatic calculation of the reaction rate constant of the oxidative processes of organic pollutants by â¢OH and SO4â¢- radicals in the aqueous phase-the pySiRC platform. The model development followed the OECD principles: internal and external validation, applicability domain, and mechanistic interpretation. Three machine learning algorithms combined with molecular fingerprints were evaluated, and all the models resulted in high goodness-of-fit for the training set with R2 > 0.931 for the â¢OH radical and R2 > 0.916 for the SO4â¢- radical and good predictive capacity for the test set with Rext2 = Qext2 values in the range of 0.639-0.823 and 0.767-0.824 for the â¢OH and SO4â¢- radicals. The model was interpreted using the SHAP (SHapley Additive exPlanations) method: the results showed that the model developed made the prediction based on a reasonable understanding of how electron-withdrawing and -donating groups interfere with the reactivity of the â¢OH and SO4â¢- radicals. We hope that our models and web interface can stimulate and expand the application and interpretation of kinetic research on contaminants in water treatment units based on advanced oxidative technologies.
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Poluentes Químicos da Água , Purificação da Água , Radical Hidroxila , Cinética , Aprendizado de Máquina , Oxirredução , ÁguaRESUMO
In this research work, the quantitative characterization of a binary blend comprised of two pozzolans (sugar cane straw (SCSA)-sugar cane bagasse ashes (SCBA), bamboo leaf ash (BLAsh)-SCBA and paper sludge (PS)-fly ash (FA)) taking into account the calculated values of the kinetic parameters of the reaction in the pozzolan/calcium hydroxide system is shown. The paper shows the most significant and important results obtained by the authors in the quantitative assessment (calculation of kinetic parameters) of the pozzolanic reaction of different mixtures of pozzolanic materials that are residues from agriculture or industrial processes. This allows a direct and rigorous comparison of the pozzolanic activity of the binary combinations of materials. The values of the kinetic parameters (reaction rate constant or activation free energy) constitute a very precise quantitative index of the pozzolanic activity of the binary combinations of materials, which is very useful for its employment in the elaboration of ternary cements. This paper shows that the binary blends 1SCBA60Blash40, 1SCBA50Blash50, 1SCBA70Blash30 have a very high pozzolanic reactivity followed by PSLSFA, 2SCBA50SCSA50, PSISFA and SCWI.
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Giardia lamblia, due to the habitat in which it develops, requires a continuous supply of intermediate compounds that allow it to survive in the host. The pentose phosphate pathway (PPP) provides essential molecules such as NADPH and ribulose-5-phosphate during the oxidative phase of the pathway. One of the key enzymes during this stage is 6-phosphogluconate dehydrogenase (6 PGDH) for generating NADPH. Given the relevance of the enzyme, in the present work, the 6pgdh gene from G. lamblia was amplified and cloned to produce the recombinant protein (Gl-6 PGDH) and characterize it functionally and structurally after the purification of Gl-6 PGDH by affinity chromatography. The results of the characterization showed that the protein has a molecular mass of 54 kDa, with an optimal pH of 7.0 and a temperature of 36-42 °C. The kinetic parameters of Gl-6 PGDH were Km = 49.2 and 139.9 µM (for NADP+ and 6-PG, respectively), Vmax =26.27 µmol*min-1*mg-1, and Kcat = 24.0 s-1. Finally, computational modeling studies were performed to obtain a structural visualization of the Gl-6 PGDH protein. The generation of the model and the characterization assays will allow us to expand our knowledge for future studies of the function of the protein in the metabolism of the parasite.
Assuntos
Giardia lamblia/enzimologia , Gluconatos/química , NADP/química , Fosfogluconato Desidrogenase/química , Proteínas de Protozoários/química , Ribulosefosfatos/química , Motivos de Aminoácidos , Sítios de Ligação , Clonagem Molecular/métodos , Expressão Gênica , Geobacillus stearothermophilus/química , Geobacillus stearothermophilus/enzimologia , Giardia lamblia/genética , Gluconatos/metabolismo , Humanos , Cinética , Modelos Moleculares , NADP/metabolismo , Via de Pentose Fosfato/genética , Fosfogluconato Desidrogenase/genética , Fosfogluconato Desidrogenase/metabolismo , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Ribulosefosfatos/metabolismo , Homologia Estrutural de Proteína , Especificidade por Substrato , TermodinâmicaRESUMO
The evaluation of the nitrification kinetics in the simultaneous presence of sulfide and organic matter using zeolite as improver was the main goal of this work. According to the sensitivity and collinearity analyses, five parameters were the most sensitive in the model, whose calibrated values were: µ max, AOB = 0.02642 ± 0.002 h-1; µ max, NOB = 0.3307 ± 0.416 h-1; K S,NOB = 1.65·10-6 ± 2.85·10-6 mgHNO2-N/L; k S2 = 0.8213 ± 0.076 and n = 0.6537 ± 0.030. A good fit between the experimental data and the model's results including the effect of zeolite on the kinetic parameters was obtained, with Theil inequality coefficient values between 0.109 and 0.007 for all the variables studied, with all of these values lower than 0.3. Thus, the model proposed is robust and can simulate the nitrification process in the presence of sulfide and organic matter when zeolite was used as improver.
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Reatores Biológicos/microbiologia , Substâncias Húmicas/análise , Sulfetos/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Zeolitas/química , Cinética , Modelos Químicos , Nitratos/análise , Nitrificação , Nitritos/análiseRESUMO
Resumen Introducción: en la búsqueda de nuevos materiales útiles como dosímetros termoluminiscentes (TL) la alúmina (α-Al2O3) ha adquirido gran atención. La α-Al2O3 posee una sensibilidad TL que es perceptible a las concentraciones de impurezas y a las condiciones térmicas del crecimiento de sus cristales, por lo que encontrar nuevas variaciones del material permitirá aumentar su respuesta TL. Objetivo: analizar las curvas de brillo de matrices de alúmina pura sinterizadas bajo diferentes condiciones de calcinación y dopadas con cerio a concentración 0.1 % p/p (Al2O3:Ce), usando la función asimétrica logística, para calcular sus parámetros cinéticos termoluminiscentes y explicar el comportamiento del material. Materiales y métodos: polvo de alúmina bohemita fue utilizado para preparar muestras puras sintetizadas de bajo diferentes condiciones de calcinación (NALO y ALO). El cerio se introdujo mediante impregnación húmeda utilizando nitrato de cerio hexa-hidratado. El análisis estructural de las matrices se realizó mediante Difracción de Rayos X. La lectura TL se realizó en un TLD 4500. Resultados: la deconvolución obtenida en las curvas de brillo para los grupos ALO y NALO evidencia la presencia de tres y cuatro señales TL respectivamente, y de seis señales TL en la muestra Al2O3:Ce. Conclusión: los tratamientos térmicos aplicados introdujeron un cambio sustancial en la curva de brillo del material y en su cinética TL, en términos del número de trampas y de la cantidad inicial de portadores de carga atrapados. La introducción de impurezas de cerio produjo una modificación fundamental en la curva de brillo de las matrices de alúmina.
Abstract Introduction: in the search for new materials useful as thermoluminescent dosimeters (TL) alumina (α-Al2O3) has acquired great attention. The α-Al2O3 has a sensitivity TL that is perceptível to the concentrations of impurities and to the thermal conditions of the growth of its crystals, so finding new variations of the material will allow to increase its TL response. Objective: analyze the brightness curves of pure alumina matrices sintered under different calcination conditions and doped with cerium at a concentration of 0.1 % p/p (Al2O3:Ce), using the asymmetric logistic function, to calculate its thermoluminescent kinetic parameters and explain the behavior of the material. Materials and methods: boehmite alumina powder was used to prepare pure sintered samples of under different calcination conditions (NALO and ALO). The cerium was introduced by wet impregnation using cerium hexahydrate nitrate. The structural analysis of the matrices was carried out by X-ray diffraction. The TL reading was performed in a TLD 4500. Results: the deconvolution obtained in the brightness curves for the ALO and NALO groups evidences the presence of three and four TL signals respectively, and of six TL signals in the sample Al2O3:Ce. Conclusion: the applied heat treatments introduced a substantial change in the brightness curve of the material and its TL kinetics, in terms of the number of traps and the initial amount of charge carriers trapped. The introduction of cerium impurities produced a fundamental modification in the brightness curve of the alumina matrices.
Resumo Introdução: na busca por novos materiais úteis como dosímetros termoluminescentes (TL), a alumina (α-Al2O3) tem adquirido grande atenção. O α-Al2O3 possui uma sensibilidade TL que é perceptível às concentrações de impurezas e às condições térmicas do crescimento de seus cristais, portanto, encontrar novas variações do material permitirá aumentar sua resposta TL. Objetivo: analisar as curvas de brilho de matrizes de alumina pura sinterizadas sob diferentes condições de calcinação e dopadas com cério na concentração de 0,1 % p/p (Al2O3:Ce), utilizando a função logística assimétrica, para calcular seus parâmetros cinéticos termoluminescentes e explicar a comportamento do material. Materiais e métodos: o pó de alumina boehmite foi usado para preparar amostras de puro sinterizado sob diferentes condições de calcinação (NALO e ALO). O cério foi introduzido por impregnação a úmido com nitrato de cério hexaidratado. A análise estrutural das matrizes foi realizada por difração de raios X. A leitura TL foi realizada em um TLD 4500. Resultados: a deconvolução obtida nas curvas de brilho para os grupos ALO e NALO mostra a presença de três e quatro sinais TL respectivamente, e de seis sinais TL na amostra Al2O3: Ce. Conclusão: os tratamentos térmicos aplicados introduziram uma mudança substancial na curva de brilho do material e sua cinética de TL, em termos do número de armadilhas e da quantidade inicial de portadores de carga aprisionados. A introdução de impurezas de cério produziu uma modificação fundamental na curva de brilho das matrizes de alumina.
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The acid mine drainage (AMD) can causes negative impacts to the environment. Physico-chemical methods to treat AMD can have high operational costs. Through passive biological methods, such as anaerobic reactors, sulfate reduction, and recovery of metals are promoted. This study evaluated the performance of a horizontal anaerobic immobilized biomass (HAIB) reactor for the treatment of synthetic AMD using polyurethane foam as support material, and anaerobic sludge as inoculum. Ethanol was used as an electron donor for sulfate reduction, resulting in an influent chemical oxygen demand (COD) in the range of 500-1,500 mg/L and COD/sulfate ratio at 1. A gradual increase of sulfate and COD concentration was applied that resulted in COD removal efficiencies higher than 78%, and sulfate removal efficiencies of 80%. Higher sulfate and COD concentrations associated with higher hydraulic retention times (36 h) proved to be a better strategy for sulfate removal. The HAIB reactor was able to accommodate an increase in the SLR up to 2.25 g SO42-/L d-1 which achieved the greatest performance on the entire process. Moreover, the reactor proved a suitable alternative for reaching high levels of metal removal (86.95 for Zn, 98.79% for Fe, and 99.59% for Cu).
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Reatores Biológicos/microbiologia , Metais Pesados/análise , Mineração , Sulfatos/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Ácidos/química , Anaerobiose , Análise da Demanda Biológica de Oxigênio , Biomassa , Células Imobilizadas/microbiologia , Oxirredução , Esgotos/química , Esgotos/microbiologia , Bactérias Redutoras de Enxofre/crescimento & desenvolvimentoRESUMO
Aspergillus is used for the industrial production of enzymes and organic acids, mainly by submerged fermentation (SmF). However, solid-state fermentation (SSF) offers several advantages over SmF. Although differences related to lower catabolite repression and substrate inhibition, as well as higher extracellular enzyme production in SSF compared to SmF have been shown, the mechanisms undelaying such differences are still unknown. To explain some differences among SSF and SmF, the secretome of Aspergillus brasiliensis obtained from cultures in a homogeneous physiological state with high glucose concentrations was analyzed. Of the regulated proteins produced by SmF, 74% were downregulated by increasing the glucose concentration, whereas all those produced by SSF were upregulated. The most abundant and upregulated protein found in SSF was the transaldolase, which could perform a moonlighting function in fungal adhesion to the solid support. This study evidenced that SSF: (i) improves the kinetic parameters in relation to SmF, (ii) prevents the catabolite repression, (iii) increases the branching level of hyphae and oxidative metabolism, as well as the concentration and diversity of secreted proteins, and (iv) favors the secretion of typically intracellular proteins that could be involved in fungal adhesion. All these differences can be related to the fact that molds are more specialized to growth in solid materials because they mimic their natural habitat.
Assuntos
Aspergillus/metabolismo , Aminoácidos/metabolismo , Análise de Variância , Aspergillus/enzimologia , Metabolismo dos Carboidratos , Dióxido de Carbono/análise , Eletroforese em Gel de Poliacrilamida , Metabolismo Energético , Fermentação , Proteínas Fúngicas/análise , Proteínas Fúngicas/classificação , Proteínas Fúngicas/metabolismo , Glucose/metabolismo , Metabolismo dos Lipídeos , Nucleotídeos/metabolismo , Oxirredução , Estresse Oxidativo , Espectrometria de Massas em TandemRESUMO
The determination of optimum values of volumetric oxygen transfer coefficient (kLa) for Spathaspora passalidarum is an important aspect for the optimization of ethanol production from pentoses since oxygen plays a key role on yeast metabolism. By studying the fermentation of a xylose and glucose mixture, the highest ethanol volumetric productivity was achieved at a kLa of 45 h-1 (1.12 gethanol L-1 h-1), reducing the fermentation time to half when compared to other oxygen-limiting conditions that were considered optimum for other native strains, besides increasing xylose consumption rates. The high cell density fermentation showed to be a good strategy to be applied in industrial processes with S. passalidarum, enabling the complete exhaustion of a high initial substrate concentration (90 g L-1) in less than 24 h, with a final ethanol titer of 28.61 (± 0.42) g L-1. By performing a detailed investigation on oxidation-reduction potential (ORP), it was possible to conclude that the highest ethanol formation rates were registered at oxireduction potential values around - 100 mV, becoming an important parameter to be controlled when oxygen-limiting conditions are applied in industrial fermentations. The oxygen availability also affected the activity of enzyme XR and its preference for NADH or NADPH, directly affecting the activity of enzyme XDH and the redox imbalance on the xylose pathway. In addition, respirometric parameters were determined for the yeast S. passalidarum under an aerobic growth condition.