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

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

S. M. de Tucumán

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

Sociedad Argentina de Microbiología General

n a Microbial Fuel Cell (MFC) microorganisms are used to generate an electrical current. At the anodic compartment, the bacteria oxidize organic matter and in some way, electrons are transfer to the anode. An external circuit leads the electrons to the cathode, originating an electrical current. The operating principle of a ?Sedimentary Microbial Fuel Cell? (SMFC) is simple; an anode is embedded in anaerobic sediment, and a cathode is exposed in the oxygenated aqueous phase over the sediment; in this condition a redox gradient between the electrodes take place. In this work two types of electrodes have been examined in a lab-scale SMFC: plain graphite (disks) and graphite reinforced with (rods). Three SMFCs were prepared with different characteristics: SM1: plain sediment; SM2: sediment + NaC2H3O2;SM3: sediment + formaldehyde. Analysis was by denaturing gradient gel electrophoresis (DGGE) and scanning electron microscopy (SEM) to analyze the native bacterial communities in sediments and study their development as the SMFC matured. SM2 disk electrode reached a current density was maintained at average of 4 mA/m2 and PDmax was 8.72 ± 1.39 mWm-2. For rod electrodes 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 control of ?non-current?) the PDmax reached during the entire experiment was 0.20 ± 0.02 mWm-2. The DGGE allowed a comparison of band profiles corresponding to the sediment samples used for the assembly of the SMFC and anodes SM2 and SM1. Through a cluster analysis of the obtained profiles, we show that the clustering of the electrodes added with acetate are more similar to the sludge, presenting, however, greater diversity associated with the addition of an extra carbon source. In the case of anode belonging to SM1, there is a lower diversity compared to initial inoculum. This could be due to the enrichment with species capable of adhering to the electrode surface and exchange electrons with it. The SEM micrographs obtained showed a dense biofilm embedded in an extracellular substrate surrounding the electrodes. All the microorganisms seemed to have the same morphology, bacilli of 1.25 and 2 µm approximately. Our SMFC data shows that these freshwater sediments can be useful to provide an electric power comparable to SMFC values obtained with marine sediments. This is the first study of a SMFC from Rio de La Plata river sediment.