Desenvolvimento de biocélulas a combustível microbianas: uso didático, novo biocatalisador e novo modelo de arquitetura

Abstract

The central proposal of this work was the construction and characterization of Microbial Fuel Cells (MFC) using low cost materials, new biocatalyst and new model of single chamber architecture. Three different systems were developed by altering the anodic biocatalyst (Saccharomyces cerevisiae or kefir microbiota), the architecture (one or two chambers) and the type of electron acceptor at the cathode (potassium ferricyanide or the prussian blue coordination compound). All MFCs used methylene blue as a mediator and were tested / characterized by means of power and polarization curves. In the first part of the work an approach was taken on the didactic use of MFCs with the use of Saccharomyces cerevisiae and two chamber architecture, and proposed experiments to evaluate the effect of presence / absence of mediator, different substrates, inhibitors, cell viability and oxygen over the MFC response. In the second part, the same architecture was used for the evaluation of the microbial consortium kefir as an anodic biocatalyst. The fermentation was monitored at intervals of 24h to 72h with the techniques of linear voltammetry (for the construction of power and polarization curves), cyclic voltammetry, current interruption, spectrophotometry, total microorganism counts, and measurements of the parameters physical-chemical pH, titratable total acidity, viscosity and carbohydrate consumption. The last part of the work was focused on the architecture and the cathode, in which a one chamber MFC was developed using hydraulic connections and a prussian blue film electrodeposited on carbon cloth as an electron acceptor. Images obtained by scanning electron microscopy and dispersive energy spectroscopy confirmed the formation of the electroactive film. It was demonstrated the possibility of obtaining electric energy from the brewery residue using this third device. The power generated was used as a common parameter to compare the performance of each of the systems, obtaining maximum values of 41 mW m-2 (two chambers, S. cerevisiae), 54 mW m-2 (two chambers, kefir culture), 136 mW m-2 (one chamber, S. cerevisiae) and 68 mW m-2 (one chamber, brewery residue).