Attachment under current – biofilm formation by electroactive bacteria

In bioelectrochemical systems solid electrodes serve as electron donor for or acceptor from microorganisms for the production of current and/or the generation of valuable substances. The first part of this theses was the analysis of the extracellular polymeric substances (EPS) secreted by G. sulfurreducens under electroactive conditions. Biofilms were grown in on polarized graphite based electrodes of MFCs. Methods for biofilm harvest and EPS processing were established. Electroactive cultures secreted significantly more EPS compared to cells grown under fumarate respiration. The highest amount of EPS was measured for the soluble EPS fraction of G. sulfurreducens using anode respiration. Proteins were found to dominate all EPS fractions. The second part was the development of a membrane separated flow cell for the simultaneous electrochemical impedance spectroscopy and confocal laser scanning microscopy. A flow cell made from PEEK was constructed, using a transparent indium tin oxide electrode as working electrode. S. oneidensis was cultivated under MFC conditions. A decrease of the charge transfer was observed with an increasing current and an increasing cell number of cells on the WE electrode. As final part a straight forward approach to synthesize magnetic electrode particles was developed. The microwave assisted synthesis of magnetite was applied for the production of the magnetic electrode particles with activated carbon. The surface area is around 300 m2 g-1 and the particle size ranges between 20 and 200 µm. Resting cells of S. oneidensis attached to a maximum concentration of 8 · 1010 ± 3 · 109 resting cells g-1 PMAG/AC. Electrochemical examination revealed that magnetically immobilized PMAG/AC showed a capacitive current response during cyclic voltammetry.