Microbial fuel cells prepared with Rio de la Plata river freshwater sediments. Current production and its relationship to changes at anodophilic microbial community

SACCO NATALIA; PATACCINI GABRIELA; BONETTO MARÍA CELINA; FIGUEROLA EVA; CORTÓN EDUARDO

S. M. de Tucumán

Congreso; VII CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL SAMIGE DEL BICENTENARIO; 2011

Sociedad Argentina de Microbiología General

In a Microbial Fuel Cell (MFC) microorganisms are used to generate an electrical current. At theanodic compartment, the bacteria oxidize organic matter and in some way, electrons aretransfer to the anode. An external circuit leads the electrons to the cathode, originating anelectrical current. The operating principle of a ?Sedimentary Microbial Fuel Cell? (SMFC) issimple; an anode is embedded in anaerobic sediment, and a cathode is exposed in theoxygenated aqueous phase over the sediment; in this condition a redox gradient between theelectrodes take place. In this work two types of electrodes have been examined in a lab-scaleSMFC: plain graphite (disks) and graphite reinforced with (rods). Three SMFCs were preparedwith different characteristics: SM1: plain sediment; SM2: sediment + NaC2H3O2;, SM3:sediment + formaldehyde. Analysis was by denaturing gradient gel electrophoresis (DGGE) andscanning electron microscopy (SEM) to analyze the native bacterial communities in sedimentsand study their development as the SMFC matured. SM2 disk electrode reached a currentdensity was maintained at average of 4 mA/m 2 and PDmax was 8.72 ± 1.39 mWm -2. For rodelectrodes the values obtained was 9 mAm -2 on average, and the maximum power density(PDmax) was 13.93 ± 3.87 mWm -2. The PDmax obtained for SM1 was approx. 19 mWm -2using rod electrodes and approx. 12 mW m- 2 for disk electrodes. With SM3 fuel cell (the controlof ?non-current?) the PDmax reached during the entire experiment was 0.20 ± 0.02 mWm -2. TheDGGE allowed a comparison of band profiles corresponding to the sediment samples used forthe assembly of the SMFC and anodes SM2 and SM1. Through a cluster analysis of theobtained profiles, we show that the clustering of the electrodes added with acetate are moresimilar to the sludge, presenting, however, greater diversity associated with the addition of anextra carbon source. In the case of anode belonging to SM1, there is a lower diversitycompared to initial inoculum. This could be due to the enrichment with species capable ofadhering to the electrode surface and exchange electrons with it. The SEM micrographsobtained showed a dense biofilm embedded in an extracellular substrate surrounding theelectrodes. All the microorganisms seemed to have the same morphology, bacilli of 1.25 and 2μm approximately. Our SMFC data shows that these freshwater sediments can be useful toprovide an electric power comparable to SMFC values obtained with marine sediments. This isthe first study of a SMFC from Rio de La Plata river sediment.