Measurements of dissolved oxygen in bioleaching reactors by optode application

Giebner, Fabian; Eisen, Sebastian; Schlömann, Michael; Schopf, Simone

doi:10.1016/j.hydromet.2016.08.001

Cited by 5 publications

(4 citation statements)

References 23 publications

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“…The rate of oxygen consumption was determined by means of optodes (Fibox 3, PreSens-Precision Sensing GmbH, Regensburg, Germany) (Giebner et al, 2017). In short, fresh iron-grown cultures of L. ferriphilum DSM 14647 were harvested by centrifugation at 8,000 × g for 15 min and, after removal of supernatant, a volume of 0.1 ml resuspended cells was added to a 3 ml measuring cuvette containing 2.6 ml of DSMZ 882 culture medium (pH 1.8) with increasing NaCl concentrations, ranging from 0 to 180 mM NaCl.…”

Section: Methodsmentioning

confidence: 99%

Osmotic Imbalance, Cytoplasm Acidification and Oxidative Stress Induction Support the High Toxicity of Chloride in Acidophilic Bacteria

et al. 2019

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In acidophilic microorganisms, anions like chloride have higher toxicity than their neutrophilic counterparts. In addition to the osmotic imbalance, chloride can also induce acidification of the cytoplasm. We predicted that intracellular acidification produces an increase in respiratory rate and generation of reactive oxygen species, and so oxidative stress can also be induced. In this study, the multifactorial effect as inducing osmotic imbalance, cytoplasm acidification and oxidative stress in the iron-oxidizing bacterium Leptospirillum ferriphilum DSM 14647 exposed to up to 150 mM NaCl was investigated. Results showed that chloride stress up-regulated genes for synthesis of potassium transporters (kdpC and kdpD), and biosynthesis of the compatible solutes (hydroxy)ectoine (ectC and ectD) and trehalose (otsB). As a consequence, the intracellular levels of both hydroxyectoine and trehalose increased significantly, suggesting a strong response to keep osmotic homeostasis. On the other hand, the intracellular pH significantly decreased from 6.7 to pH 5.5 and oxygen consumption increased significantly when the cells were exposed to NaCl stress. Furthermore, this stress condition led to a significant increase of the intracellular content of reactive oxygen species, and to a rise of the antioxidative cytochrome c peroxidase (CcP) and thioredoxin (Trx) activities. In agreement, ccp and trx genes were up-regulated under this condition, suggesting that this bacterium displayed a transcriptionally regulated response against oxidative stress induced by chloride. Altogether, these data reveal that chloride has a dramatic multifaceted effect on acidophile physiology that involves osmotic, acidic and oxidative stresses. Exploration of the adaptive mechanisms to anion stress in iron-oxidizing acidophilic microorganisms may result in new strategies that facilitate the bioleaching of ores for recovery of precious metals in presence of chloride.

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Section: Methodsmentioning

confidence: 99%

Osmotic Imbalance, Cytoplasm Acidification and Oxidative Stress Induction Support the High Toxicity of Chloride in Acidophilic Bacteria

et al. 2019

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“…The oxygen consumption rate was determined by means of optodes (Fibox 3, PreSens-Precision Sensing GmbH, Regensburg, Germany) [22]. In short, fresh iron-grown 100 mL-cultures of L. ferriphilum DSM 14647 were harvested by centrifugation at 8,000 x g for 15 min, the supernatant was removed, and the pelleted cells were resuspended in 0.1 mL the remaining growth medium, before being added to a 3-mL cuvette containing 2.6 mL of DSM 882 culture medium pH 1.8 with 0 or 180 mM NaCl for non-adapted and adapted cell cultures, respectively.…”

Section: Oxygen Consumptionmentioning

confidence: 99%

Transcriptomic analysis of chloride tolerance in Leptospirillum ferriphilum DSM 14647 adapted to NaCl

et al. 2022

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Chloride ions are toxic for most acidophilic microorganisms. In this study, the chloride tolerance mechanisms in the acidophilic iron-oxidizing bacterium Leptospirillum ferriphilum DSM 14647 adapted to 180 mM NaCl were investigated by a transcriptomic approach. Results showed that 99 genes were differentially expressed in the adapted versus the non-adapted cultures, of which 69 and 30 were significantly up-regulated or down-regulated, respectively. Genes that were up-regulated include carbonic anhydrase, cytochrome c oxidase (ccoN) and sulfide:quinone reductase (sqr), likely involved in intracellular pH regulation. Towards the same end, the cation/proton antiporter CzcA (czcA) was down-regulated. Adapted cells showed a higher oxygen consumption rate (2.2 x 10−9 ppm O2 s-1cell-1) than non-adapted cells (1.2 x 10−9 ppm O2 s-1cell-1). Genes coding for the antioxidants flavohemoprotein and cytochrome c peroxidase were also up-regulated. Measurements of the intracellular reactive oxygen species (ROS) level revealed that adapted cells had a lower level than non-adapted cells, suggesting that detoxification of ROS could be an important strategy to withstand NaCl. In addition, data analysis revealed the up-regulation of genes for Fe-S cluster biosynthesis (iscR), metal reduction (merA) and activation of a cellular response mediated by diffusible signal factors (DSFs) and the second messenger c-di-GMP. Several genes related to the synthesis of lipopolysaccharide and peptidoglycan were consistently down-regulated. Unexpectedly, the genes ectB, ectC and ectD involved in the biosynthesis of the compatible solutes (hydroxy)ectoine were also down-regulated. In line with these findings, although hydroxyectoine reached 20 nmol mg-1 of wet biomass in non-adapted cells, it was not detected in L. ferriphilum adapted to NaCl, suggesting that this canonical osmotic stress response was dispensable for salt adaptation. Differentially expressed transcripts and experimental validations suggest that adaptation to chloride in acidophilic microorganisms involves a multifactorial response that is different from the response in other bacteria studied.

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“…The physicochemical parameters include pH (Dorado et al 2012;Liang et al 2013;Mishra et al 2008;Mousavi et al 2008;Xiang et al 2010;Yang et al 2009), temperature (Hong and Valix 2014;Lambert et al 2015), redox potential (Vilcáez, Suto, and Inoue 2008;Zhao et al 2015) and oxygen content and its availability (Giebner et al 2016;Mazuelos et al 2017;Thurston, Mandernack, and Shanks 2010), among others.…”

Section: Factors Influencing the Bioleaching Processmentioning

confidence: 99%

“…Giebner et al (2015) suggested that another obvious approach is to quantify the consumption of the electron acceptor oxygen since the instant consumption of this electron acceptor can be only attributed to microorganisms activity. They affirmed that the application of a Clark electrode could be the easiest and cheapest technique for respirometry control but, taking into account that Atkinson and Smith (1973) observed that this kind of electrodes consume oxygen due to its operation, Giebner et al (2016) adapted an optode-based technique of respirometry control. This technique was adapted to measure oxygen consumption of Acidithiobacillus ferroxidans and, thus, to determine its metabolic activity.…”

Section: Introductionmentioning

confidence: 99%

Study and optimisation of copper bioleaching process for electronic waste valorisation

Benzal Montes

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In the current economical context, the use of waste material with economic potential should be a priority. In this sense, the increasing production of electrical and electronic equipment waste (WEEE) makes these materials a potential source for valuable and scarce metals. For this reason, it is important to develop new metal recovery methodologies economically that are more profitable, sustainable and environmental friendly. A possible solution to this problem is to take advantage of the metabolic activity of certain microorganisms, mainly bacteria, to regenerate the responsible agents for the extraction of metals from the matrix in which they are contained once the useful life of them has ended. This process is known as bioleaching or biological leaching. In this thesis, a study of this biotechnological process for metal recovery from WEEE has been carried out. Firstly, bioleaching to recover copper from low-grade chalcopyrite was studied to establish the bases of the methodology, already applied in the biomining field, as well as to check the feasibility of the technique in this field. Subsequently, bioleaching was extended to be applied in the field of the electronic waste, thus recovering metals from printed circuit boards (PCB) based on their high metal content and their limited availability in the nature. Given the interest of this process, not very studied in the field of the electronic waste, an adjustment of those parameters that allow optimizing the operation is necessary. For this reason, the effect of several parameters has been studied such as pH effect, PCB concentration or particle size, as well as the most appropriate system to perform the process (flasks, bioreactor or column). After bioleaching, the extracted metals remain in the leaching solution, so a last step to obtain the metals in their metallic state again and separated from the initial matrix should be perform which closes the recovery cycle. The study to recover the bioleached copper has been carried out more superficially in this thesis, focusing on cementation as a simple and cheaper alternative to other more complex processes such as electrolysis. In addition to the metals extraction through bioleaching, this thesis has been also focused on studying the limits of the technology due to the complex and varied composition of the waste, such as the toxic effect that bioleached metals could cause to the microorganisms involved in the process or the evaluation of possible substrate inhibition. The measurement of the biological activity may be the solution when there are limitations of quantifying biomass in systems where the formation of precipitates can be habitual, as in bioleaching occurred. For this reason, a microrespirometry-based procedure has been developed that allows to directly measure the oxygen consumption and, thus, the microbial activity at real time. In microrespirometry, the formation of precipitates does not interfere with the measurement which allows obtaining a reliable result of the microbial concentration. Thus, after affirming the feasibility of bioleaching as a simpler, cheaper and environmental friendly alternative to traditional physical-chemical processes, this thesis establishes the most favourable conditions to obtain the greatest possible copper recovery through bioleaching. These bases are the previous phase to scale-up the technology to be implemented in an industrial environment. En el actual contexto económico, el provecho de materiales residuales con potencial económico debería ser prioritario. En este sentido, la creciente producción de residuos eléctricos y electrónicos (REES) convierte estos materiales en una potencial fuente de metales muy valiosos y escasos. Por este motivo, es importante desarrollar nuevas tecnologías de valorización de metales que sean económicamente más rentables, sostenibles y respetuosas con el medio ambiente. Una posible solución para este problema consiste en aprovechar la actividad metabólica de determinados microrganismos, principalmente bacterias, para regenerar los agentes responsables de la extracción de metales de la matriz donde se encuentran inmovilizados una vez finalizada la vida útil del aparato eléctrico que los contiene. Este proceso es conocido como biolixiviación o lixiviación biológica. En esta tesis se ha llevado a cabo el estudio de este proceso biotecnológico para la recuperación de metales procedentes de REES. En primer lugar, se estudió la biolixiviación para recuperar cobre a partir de calcopirita de baja ley para establecer el procedimiento de la metodología, ya aplicada en el campo de la biominería, y comprobar la viabilidad de la técnica en este campo. Posteriormente, la biolixiviación fue aplicada al campo de los residuos electrónicos, realizando así la extracción de metales de placas de circuito impreso (PCB, del inglés, printed circuit boards), basándose en la gran cantidad de metales que éstos contienen y su limitada disponibilidad en la naturaleza. Ante el interés de este proceso, no muy estudiado en el campo de los residuos electrónicos, es necesario ajustar aquellos parámetros que permitan optimizar la operación. Por este motivo, se ha estudiado el efecto de varios parámetros que afectan al proceso como el pH, la concentración de residuo o el tamaño de partícula, así como también el sistema más adecuado para llevar a cabo el proceso (matraz, biorreactor o columna). Tras la biolixiviación, los metales extraídos permanecen en solución por lo que es necesario realizar una última etapa para llegar a obtener los metales en su estado metálico nuevamente, aunque separado de la matriz inicial en este caso, y cerrar así el ciclo de la recuperación. En esta tesis el estudio para recuperar el cobre lixiviado se ha realizado de forma más superficial, centrándose en la cementación como alternativa simple y económica a otros procesos más complejos como la electrólisis. Además de la extracción de metales mediante biolixiviación, esta tesis también se ha centrado en estudiar factores que limitan la tecnología debido a la compleja y variada composición de los residuos, como es el efecto tóxico que pueden provocar los metales biolixiviados sobre los microorganismos involucrados en el proceso, así como la evaluación de la inhibición por sustrato. La medición de la actividad biológica puede ser la solución cuando haya limitaciones de cuantificar la biomasa en sistemas donde la formación de precipitados suele ser habitual, como es el caso de la biolixiviación. Por este motivo se ha desarrollado un procedimiento basado en la microrespirometría que permite obtener de forma directa el consumo de oxígeno y, por tanto, la actividad a tiempo real de una muestra biológica. En las microrespirometrías la formación de precipitados no interfiere en la medición por lo que permite obtener un resultado fiable de la concentración microbiana. Así pues, tras afirmarse la viabilidad de la biolixiviación como alternativa más simple, económica y medioambientalmente sostenible a los procesos físico-químicos tradicionales, esta tesis establece las condiciones más favorables para obtener la mayor recuperación de cobre posible mediante biolixiviación. Estas bases son la fase previa para escalar la tecnología a implementar en un entorno industrial.

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Measurements of dissolved oxygen in bioleaching reactors by optode application

Cited by 5 publications

References 23 publications

Osmotic Imbalance, Cytoplasm Acidification and Oxidative Stress Induction Support the High Toxicity of Chloride in Acidophilic Bacteria

Osmotic Imbalance, Cytoplasm Acidification and Oxidative Stress Induction Support the High Toxicity of Chloride in Acidophilic Bacteria

Transcriptomic analysis of chloride tolerance in Leptospirillum ferriphilum DSM 14647 adapted to NaCl

Study and optimisation of copper bioleaching process for electronic waste valorisation

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