Electrosíntesis microbiana a partir de cultivos mixtos de bacterias fotótrofas rojas

Extracellular electron transfer (EET) is a process in which microorganisms due to cellular structures such cytochromes, trans-membrane proteins or outer membrane proteins are able to transfer electrons to a conductive surface of an insoluble electron acceptor. From the combination between electrochemistry and microbiology, microbial electrochemistry techniques (METs) appear. These techniques have been applied in wastewater treatment, energy production and water desalination. In spite of positive results, this field is in constant optimization in order to improve the efficiency. Furthermore, one of the novel applications is the biofuel production and high-value products generation in microbial electrochemical reactors. Even though it is in its infancy, it might have great potential owing to the low implementation cost. Purple bacteria are gram-negative bacteria, they inhabit anoxygenic aquatic environments, extreme habitats in temperature alkalinity, acidity and high salt concentrations, and in different types of wastewater such brewery wastewater. This wide ecosystem range is the result of the metabolic diversity in purple bacteria, being one of the most extended group in all Earth. These microorganisms perform anoxygenic photosynthesis and CO2 fixation, which makes them potentially useful when it comes to produce biofuel, volatile fatty acids or functional membrane proteins. The combination of purple phototrophic bacteria and METs allow us to take advantage of their adaptive qualities in order to improve the reactors. This could open new research field due to the possibilities of their metabolism, not only in biofuel production, but also in pesticide degradation, ground decontamination, toxic metals removal and nitrogen fixation. Moreover, working with purple photobacteria would allow reducing energy waste in high-value products generation process because of the working condition would not be as restrictive as other microorganisms. These conditions would be standard temperature and using a non-specific growth culture being the wastewater itself. In this project, purple photobacteria enrichment from brewery wastewater was done. The objective of this work is to study electroactive capacities of purple photobacteria and its bio-electrosynthesis potential. The microorganisms grew under infra-red and dark conditions plus three different carbon sources with different oxidative values in order to study the influence of these carbon sources in carotenoid and bacteriochlorophyll production. Spectrophotometric measurements were performed in order to characterize microbial growth under the effect of three different electron donors. The high valued products generation and carbon source consumption was measured by high performance liquid chromatography. Besides, the different communities and their variations in the mixed culture were studied by 16S sequencing being Bosea spp the most predominant genus. To conclude with, an electrochemical reactor was optimized and inoculated with the purple phototrophic bacteria previously grown on acetate and polarized at -0,5 V. Cyclic voltametries showed that purple phototrophic bacteria are able to modify electrode surface and they might also take electrons from an insoluble donor, therefore, more experiments are needed in order to confirm bio-electrosynthesis.