Un hongo de la madera que produce electricidad/A tree fungus that produces electricity

The white-rot fungus T. versicolor. Photograph by Martina Berg

Sabine Sané, estudiante de doctorado del grupo de investigación Micro Energy Harvesting del Departamento de Ingeniería de Microsistemas (IMTEK) de la Universidad de Friburgo, ha encontrado la forma de que una especie de hongo de la madera sirva para producir electricidad.
Este nuevo concepto de conversión energética es el tema de portada de ChemSusChem, una revista científica sobre química, sostenibilidad, energía y materiales. La investigación fue apoyada por científicos del grupo de investigación dirigido por el Dr. Sven Kerzenmacher en el Laboratorio del Prof. Dr. Roland Zengerle para aplicaciones de MEMS (sistemas microelectromecánicos).
Las células de biocombustible producen electricidad, por ejemplo de desechos orgánicos, de una forma sostenible y que preserva recursos. Pueden emplear enzimas como catalizadores que permiten que se produzcan reacciones electroquímicas que generan electricidad. En contraste con los catalizadores basados en metales preciosos que se utilizan en las células de combustible convencionales, estas enzimas se pueden obtener a bajo coste a partir de materias primas renovables. Sin embargo, su vida es demasiado corta para algunas aplicaciones.
El nuevo concepto desarrollado por los científicos de Freiburg resuelve este problema asegurando que la célula de combustible se alimenta continuamente con el biocatalizador. El proveedor de la célula de combustible es Trametes versicolor, un hongo de la madera, que se encuentra en climas templados: libera la enzima fúngica Laccasa (una enzima oxidasa que contiene cobre) en la disolución que baña el cátodo - polo positivo de la célula – lo que permite la conversión electroquímica de oxígeno.
Los experimentos llevados a cabo por los investigadores han demostrado que este método puede alargar la vida útil de los cátodos hasta 120 días, y parece probable que se pueden lograr tiempos de vida considerablemente más largos. En comparación, los cátodos sólo tienen una vida útil de 14 días si no se les suministra más enzima. Dado que la solución enzimática se puede suministrar directamente a la pila de combustible sin necesidad de un costosa y larga purificación, los costes se reducen a un mínimo.
Las potenciales aplicaciones de este concepto incluyen células de combustible microbianas que generan electricidad a partir de aguas residuales, una tecnología que también está desarrollando el grupo de investigación de Kerzenmacher

The tricopper site found in many laccases. Each copper center is bound to the imidazole sidechains of histidine (color code: copper is brown, nitrogen is blue).

Sabine Sané, doctoral candidate in the Micro Energy Harvesting research group at the Department of Microsystems Engineering (IMTEK) of the University of Freiburg, has found a way to make a species of tree fungus useful for the production of electricity.
The new energy conversion concept was chosen as the cover story of ChemSusChem, a scientific journal for chemistry, sustainability, energy, and materials. The research was supported by scientists from a research group led by Dr. Sven Kerzenmacher at Prof. Dr. Roland Zengerle’s Laboratory for MEMS Applications.
Biofuel cells produce electricity that is environmentally friendly and conserves resources, for instance from organic waste material. They can use enzymes as catalysts to enable electrochemical reactions that generate electricity. In contrast to precious metal catalysts in conventional fuel cells, these enzymes can be obtained at low cost from renewable raw materials. For many technical applications, however, their lifetime is too short.
The new concept developed by the Freiburg scientists solves this problem by ensuring that the fuel cell is continually resupplied with the biocatalyst. The supplier of the fuel cell is Trametes versicolor, a tree fungus that is also found in temperate climates: It releases the fungal enzyme Laccase (a copper-containing oxidase enzyme) into a solution surrounding the cathode – the positive pole of the cell – where it enables the electrochemical conversion of oxygen.
Experiments conducted by the researchers demonstrate that this method can be used to extend the lifetime of the cathodes to as much as 120 days, and even considerably longer lifetimes seem possible. By comparison, the cathodes only have a lifetime of 14 days if they are not supplied with more of the enzymes. Since the enzymatic solution can be supplied directly to the fuel cell without time-consuming and expensive purification, the costs are reduced to a minimum.
Potential applications for the concept include microbial fuel cells that generate electricity from wastewater, a technology Kerzenmacher’s research group is also developing.

Tomado de/Taken from University of Freiburg
Overcoming Bottlenecks of Enzymatic Biofuel Cell Cathodes: Crude Fungal Culture Supernatant Can Help to Extend Lifetime and Reduce Cost S. Sané, C. Jolivalt, G. Mittler, P.J. Nielsen, S. Rubenwolf, R. Zengerle, S. Kerzenmacher (2013) ChemSusChem 6 p. 1209-1215. DOI: 10.1002/cssc.201300205
Available online without a subscription until 17 July 2013 at: http://onlinelibrary.wiley.com/doi/10.1002/cssc.201300205/abstract
Abstract
Enzymatic biofuel cells (BFCs) show great potential for the direct conversion of biochemically stored energy from renewable biomass resources into electricity. However, enzyme purification is time-consuming and expensive. Furthermore, the long-term use of enzymatic BFCs is hindered by enzyme degradation, which limits their lifetime to only a few weeks. We show, for the first time, that crude culture supernatant from enzyme-secreting microorganisms (Trametes versicolor) can be used without further treatment to supply the enzyme laccase to the cathode of a mediatorless BFC. Polarization curves show that there is no significant difference in the cathode performance when using crude supernatant that contains laccase compared to purified laccase in culture medium or buffer solution. Furthermore, we demonstrate that the oxygen reduction activity of this enzymatic cathode can be sustained over a period of at least 120 days by periodic resupply of crude culture supernatant. This is more than five times longer than control cathodes without the resupply of culture supernatant. During the operation period of 120 days, no progressive loss of potential is observed, which suggests that significantly longer lifetimes than shown in this work may be possible. Our results demonstrate the possibility to establish simple, cost efficient, and mediatorless enzymatic BFC cathodes that do not require expensive enzyme purification procedures. Furthermore, they show the feasibility of an enzymatic BFC with an extended lifetime, in which self-replicating microorganisms provide the electrode with catalytically active enzymes in a continuous or periodic manner