Biological and Bioelectrochemical Systems for Hydrogen Production and Carbon Fixation Using Purple Phototrophic Bacteria

Domestic and industrial wastewaters contain organic substrates and nutrients that can be recovered instead of being dissipated by emerging efficient technologies. The aim of this study was to promote bio-hydrogen production and carbon fixation using a mixed culture of purple phototrophic bacteria (PPB) that use infrared radiation in presence or absence of an electrode as electron donor. In order to evaluate the hydrogen production under electrode-free conditions, batch experiments were conducted using different nitrogen (NH4Cl, Na-glutamate, N2 gas) and carbon sources (malic-, butyric-, acetic- acids) under various COD:N ratios. Results suggested that the efficiency of PPB to produce biogenic H2 was highly dependent on the substrates used. The maximum hydrogen production (H2_max, 423 mLH2/L) and production rate (H2_rate, 2.71 mLH2/Lh) were achieved using malic acid and Na-glutamate at a COD:N ratio of 100:15. Under these optimum conditions, a significant fixation of nitrogen in form of single-cell proteins (874.4 mg/L) was also detected. Under bio-electrochemical conditions using a H-cell bio-electrochemical device, the PPB were grown planktonic in the bio-cathode chamber with the optimum substrate ratio of malic acid and Na-glutamate. A redox potential of −0.5 V (vs. Ag/AgCl) under bio-electrochemical conditions produced comparable amounts of bio-hydrogen but significantly negligible traces of CO2 as compared to the biological system (11.8 mLCO2/L). This suggests that PPB can interact with the cathode to extract electrons for further CO2 re-fixation (coming from the Krebs cycle) into the Calvin cycle, thereby improving the C usage. It has also been observed during cyclic voltammograms that a redox potential of −0.8 V favors considerably the electrons consumption by the PPB culture, suggesting that the PPB can use these electrons to increase the biohydrogen production. These results are expected to prove the feasibility of stimulating PPB through bio-electrochemical processes in the production of H2 from wastewater resources, which is a field of special novelty and still unexplored

The bioelectrogenic column: a tool for bringing microbial ecology and electrochemistry into secondary school

Para transmitir conceptos científicos complejos en un entorno escolar, la utilización de experimentos llamativos representa una herramienta muy útil. En este artículo se presenta la columna bioelectrogénica, un sistema experimental que une la columna de Winogradsky clásica con las más recientes investigaciones en el campo de la microbiología aplicada. A través de su implementación es posible visualizar procesos físicos, químicos y biológicos que forman parte de la enseñanza científica en institutos de secundaria. Además, la columna bioelectrogénica ha sido ideada para demostrar la existencia de bacterias capaces de producir energía eléctrica, un fenómeno que induce curiosidad y estupor, elementos claves para estimular la participación de los estudiantes. Este sistema ha sido presentado en varias actividades de divulgación para estudiantes de secundaria y siempre ha despertado un elevado grado de interés.The use of inspiring experimental demonstrations is a fundamental tool for teaching complex scientific concepts in secondary schools. In this article we present the bioelectrogenic column, an experimental system that joins the classic Winogradsky column to the most recent findings in the field of applied microbiology. With this system we can visualise physical, chemical and biological processes that are at the heart of a sound scientific education. Furthermore, the bioelectrogenic column had been designed to demonstrate the existence of bacteria capable of producing electric energy, an astonishing phenomenon that leaves students highly inquisitives, a key for stimulating their participation. This system has been presented in various scientific outreaching activities for secondary school, always awakening a strong interest in the audience

La columna bioelectrogénica: una herramienta para introducir conceptos de ecología microbiana y electroquímica en la educación secundaria

The use of inspiring experimental demonstrations is a fundamental tool for teaching complex scientific concepts in secondary schools. In this article we present the bioelectrogenic column, an experimental system that joins the classic Winogradsky column to the most recent findings in the field of applied microbiology. With this system we can visualise physical, chemical and biological processes that are at the heart of a sound scientific education. Furthermore, the bioelectrogenic column had been designed to demonstrate the existence of bacteria capable of producing electric energy, an astonishing phenomenon that leaves students highly inquisitives, a key for stimulating their participation. This system has been presented in various scientific outreaching activities for secondary school, always awakening a strong interest in the audience.Para transmitir conceptos científicos complejos en un entorno escolar, la utilización de experimentos llamativos representa una herramienta muy útil. En este artículo se presenta la columna bioelectrogénica, un sistema experimental que une la columna de Winogradsky clásica con las más recientes investigaciones en el campo de la microbiología aplicada. A través de su implementación es posible visualizar procesos físicos, químicos y biológicos que forman parte de la enseñanza científica en institutos de secundaria. Además, la columna bioelectrogénica ha sido ideada para demostrar la existencia de bacterias capaces de producir energía eléctrica, un fenómeno que induce curiosidad y estupor, elementos claves para estimular la participación de los estudiantes. Este sistema ha sido presentado en varias actividades de divulgación para estudiantes de secundaria y siempre ha despertado un elevado grado de interés.Palabras clave: Bioelectrogénesis. Columna de Winogradsky. Ecología microbiana. Bioelectroquímica. Bacterias productoras de la electricidad. Geobacter.The bioelectrogenic column: a tool for bringing microbial ecology and electrochemistry into secondary schoolThe use of inspiring experimental demonstrations is a fundamental tool for teaching complex scientific concepts in secondary schools. In this article we present the bioelectrogenic column, an experimental system that joins the classic Winogradsky column to the most recent findings in the field of applied microbiology. With this system we can visualise physical, chemical and biological processes that are at the heart of a sound scientific education. Furthermore, the bioelectrogenic column had been designed to demonstrate the existence of bacteria capable of producing electric energy, an astonishing phenomenon that leaves students highly inquisitives, a key for stimulating their participation. This system has been presented in various scientific outreaching activities for secondary school, always awakening a strong interest in the audience.Keywords: Bioelectrogenesis. Winogradsky column. Molecular ecology. Bioelectrochemistry. Electricity-producing bacteria. Geobacter

Metabolismo anaerobio del explosivo 2,4,6-trinitrotolueno (Tnt) por bacterias del género pseudomonas

El explosivo 2,4,6-Trinitrotolueno (TNT) está presente en suelos y aguas subterráneas cercanas a instalaciones militares o civiles donde se haya realizado actividades de producción, almacenaje y procesamiento, dando lugar a frandes volúmenes de aguas residuales contaminadas con el explosivo. La toxicidad del TNT y su carácter mutagénico hacen que la limpieza de lugares contaminados con este compuesto xenobiótico constituya una prioridad para las agencias medioambientales. A través del desarrollo experimental descrito en esta Tesis Doctoral, se ha aislado y caracterizado una cepa bacteriana, denominada Pseudomonas sp. JLR11, capaza de utilizar eficientemente el TNT como única fuente de nitrógeno en condiciones anóxicas. El proceso de eliminación de TNT ha sido optimizado en un reactor de 2 litros, manteniendo en codndiciones anóxicas y operando en condiciones estancas. Se ha mostrado que el explosivo TNT desempeña en Pseudomonas sp JLR11 un doble papel: el de nutriente y el de substrato respiratorio. El metabolismo de TNT requiere de un cosubstrato adicional que actúe como donar de electrones. Distintos compuestos carbonados (glucosa, sacaros, acetato, citrato, benzoato, p- hidroxibenzoato) son cpaces de desempeñar esta función. La asimilación del nitrógeno del TNT por Pseudomonas sp.JLR11, en condiciones de narerobiosis, tiene lugar a través de la eliminación de los grupos nitro en forma de nitrito, el cual es posteriormente reducido a amonio por la enzima nitrito reductasa. El 85% del nitrógeno del TNT y el 45% del carbono de su anillo aromático se incorporaron a material celular. El hecho de que este nitroaromático pueda actuar como aceptor de electrones en el metabolismo anaerobio de esta cepa le confirere una ventaja selectiva al permititle, no sólo sobrevivir en ambientes anóxicos como sedimientos o aguas subterráneas, sino tambieén ejercer de forma activa sus capacidades degradadoras en ambientes pobres en oxígeno contaminados con TNTUniversidad de Granada, Departamento de bioquímica y Biología Molecular. Leída 27-06-0

ATR-SEIRAs characterization of surface redox processes in G. sulfurreducens

In this work we report on the occurrence of at least two different redox pairs on the cell surface of the electrogenic bacteria Geobacter sulfurreducens adsorbed on gold that are expressed in response to the polarization potential. As previously reported on graphite (Environ. Sci. Technol. 42 (2008) 2445) a typical low potential redox pair is found centered at around − 0.06 V when cells are polarized for a few hours at 0.2 V, while a new pair centered at around 0.38 V is expressed upon polarization at 0.6 V. Reversible changes in the IR band pattern of whole cells where obtained by Attenuated Total Reflection-Surface Enhanced Infrared Absorption Spectroscopy (ATR-SEIRAS) upon potential cycling around both redox pairs. Changes clearly resemble the electrochemical turnover of oxidized/reduced states in c-type cytochromes, thus evidencing the nature of the involved molecules. The expression of external cytochromes in response to the potential of the electron acceptor suggests the existence of alternative pathways of electron transport with different energy yield, though it remains to be demonstrated.Fil: Busalmen, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentina. Universidad de Alicante; EspañaFil: Esteve-Nuñez, Abraham. Centro de Astrobiología; EspañaFil: Berná, Antonio. Universidad de Alicante; EspañaFil: Feliu, Juan Miguel. Universidad de Alicante; Españ

Respiration of 2,4,6-Trinitrotoluene by Pseudomonas sp. Strain JLR11

Under anoxic conditions Pseudomonas sp. strain JLR11 can use 2,4,6-trinitrotoluene (TNT) as the sole N source, releasing nitrite from the aromatic ring and subsequently reducing it to ammonium and incorporating it into C skeletons. This study shows that TNT can also be used as a terminal electron acceptor in respiratory chains under anoxic conditions by Pseudomonas sp. strain JLR11. TNT-dependent proton translocation coupled to the reduction of TNT to aminonitrotoluenes has been observed in TNT-grown cells. This extrusion did not occur in nitrate-grown cells or in anaerobic TNT-grown cells treated with cyanide, a respiratory chain inhibitor. We have shown that in a membrane fraction prepared from Pseudomonas sp. strain JLR11 grown on TNT under anaerobic conditions, the synthesis of ATP was coupled to the oxidation of molecular hydrogen and to the reduction of TNT. This phosphorylation was uncoupled by gramicidin. Respiration by Pseudomonas sp. strain JLR11 is potentially useful for the biotreatment of TNT in polluted waters and soils, particularly in phytorhizoremediation, in which bacterial cells are transported to the deepest root zones, which are poor in oxygen

Opportunities behind the unusual ability of Geobacter sulfurreducens for exocellular respiration and electricity production

The possibility to improve the connection of cells to the electrode is significant for microbial fuel cell technology. In this communication we demonstrate that an improved connection can be made by controlling the physiological state of electricity-harvesting bacteria as Geobacter sulfurreducens.Fil: Esteve Nuñez, Abraham. Universidad de Alcala; EspañaFil: Busalmen, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Berná, Antonio. Universidad de Alicante. Departamento de Quiâ­mica Orgánica; EspañaFil: Gutierrez Garran, Cristina. Universidad de Alcala; EspañaFil: Feliu, Juan Miguel. Universidad de Alicante. Departamento de Quiâ­mica Orgánica; Españ

Electrochemical insight into the mechanism of electron transport in biofilms of Geobacter sulfurreducens

Electroactive bacterial biofilms can be produced on a polarized electrode by forcing its use as the final electron acceptor for bacterial respiration. This strategy offers the researcher the unique possibility to control the respiration process with extreme precision. The production of current, the accumulation of charge and the conducting properties of electroactive biofilms has been interrogated in this work through very basic electrochemical techniques including chronopotentiometry, chronoamperometry and cyclic voltammetry. Presented results indicate that charge can be accumulated in the biofilm conductive network, that network conductivity does not represent a limit for current production and that both the steady state current and the amount of accumulated charge depend on the redox state of cytochromes wiring the cells to the electrode. A model of biofilm conduction is presented as well.Fil: Schrott, Germán David. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Bonanni, Pablo Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Robuschi, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Esteve Nuñez, Abraham. Universidad de Alcala; EspañaFil: Busalmen, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentin