Generation of bio-compounds from microbial catalysts fueled by CO2 and electrons, with potential for the production of biofuels and compounds of interest

This thesis is dealing with my work in the field of microbial electrochemistry of relevant microbial strains applied to microbial electrolytic cells. It consists of two main topics: the electrochemical characterization of the novel CO2 reduction reaction in the electroactive model bacterium Shewanella oneidensis MR-1 and the electrochemical characterization of strain 42OL of the Purple Non Sulfur Bacteria Rhodopseudomonas palustris. During the time I was in Japan at the University of Tokyo, I explored the possibility of carbon fixation by Shewanella oneidensis MR-1 model microbe for anodic extracellular electron transfer process. The results showed that the current consumed by the strain was indeed increasing upon bubbling with carbon dioxide, while when administering argon gas did not increase the current uptake. While I was not able to identify the product of carbon fixation at the time, a successive search in the literature revealed that Shewanella is able to produce formate in experimental conditions similar to those that I used. At University of Florence and CREA, I carried out the electrochemical characterization of a strain of Purple Non Sulfur Bacteria, Rhodopseudomonas palustris 42OL and explored the possibility of single culture electrochemically driven biological nitrogen fixation. The results are quite surprising, in fact, Rps. palustris 42OL is indeed electroactive in both anodic and cathodic modes, and in addition to that it exhibits a noteworthy current uptake in the cathodic mode while the electrochemical cell medium is bubbled with high purity nitrogen gas. Scanning Electron Microscope micrographies are also showing that Rps. palustris 42OL is directly attached to the Working Electrode and possibly forms subcellular structures like nanowires, thereby meaning that the mechanism of electron transfer to the electrode is also of direct type.