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INVESTIGADORES

ABREVAYA Ximena Celeste

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Título:

Microbial Fuel Cells as life detection sensors for terrestrial and extraterrestrial environments

Autor/es:

ABREVAYA, X.C.; MAUAS, P.J.D.; CORTÓN, E.

Lugar:

Lisboa

Reunión:

Congreso; Ibersensors 2010; 2010

Resumen:

Microbial Fuel Cells (MFCs) are bio-electrochemical systems originally designed and applied to electrical power generation. In these devices, the power source is given by biocatalysts such as microorganisms, which as part of their metabolic process, release electrons that supply the electric current production, that can be easily measured if an adequate external resistor is incorporated in the electric circuit. At present, there is much work done with MFCs, with multiple combinations of electrode material and microorganisms (Rabaey et al. 2005; Bullen et al. 2006; Davis and Higson, 2007). In the conventional configuration, MFCs have a cathode and anode chamber, which are connected through a cation exchange membrane (such as Nafion®) (Fig 1). Usually, the anode is biotic and the cathode abiotic, since the anolyte contain microorganisms and catholyte is composed by an oxidizing agent, as oxygen or ferricyanide, among others. In the anode, electrons are released due to the oxidation of organic material which is carried out by the microorganisms. This activity is proportional to the metabolic process and therefore is related to heterotrophic metabolisms.  Since metabolism is a widespread characteristic of all kind of life on Earth and could be a common feature of all living system including extraterrestrial life (Nealson et al., 2002), MFCs could be used as life detection sensors based on metabolic activity. In the present work we show the capacity of MFCs for the detection of heterotrophic metabolisms, and its potential use to the in situ search for extraterrestrial and terrestrial life. For this purpose we used pure cultures of microorganisms (Saccharomyces cerevisiae and Natrialba magadii, an eukaryotic organism and an halophile archaeon, respectively) and a mixed community of microorganisms from humus soil, together with the corresponding comparison with the sterilized culture or soil samples. We demonstrate that the power and current density values measured in MFCs using microorganism cultures or soil samples in the anode are much larger than those obtained using sterilized cultures or soil samples, respectively. This is due to the fact that, in the absence of biocatalysts, the electrons which are transferred through the circuit are limited by the anodic reaction, which depends upon reduced substances that are present at the beginning of the experiment and then exhausted with time.

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