The seminar will take place, the 8th of September, at 14h, at the ENSCBP amphitheater, Building B, allée Geoffroy Saint-Hilaire, Pessac.
Alexandre Ciaccafava, Postdoc
Max Volmer Laboratorium , Technische Universität Berlin, UniCat Cluster of excellence
Our society is facing challenging issues concerning the energetic transition from fossil fuels to renewable energy resources and also to the environmental side effects due to the huge atmospheric CO2 emissions. In the field of renewable and sustainable energy, hydrogen (H2) has become a major “green” energy vector due to its outstanding properties (highest energetic mass density, sustainable clean production from water or biomass. Alternatively, the idea of back conversion procedure from CO2 to fuels was developed, similarly to photosynthesis which is responsible for the production of fossil fuels used nowadays, by converting CO2, H2O and sunlight into reduced organic materials.
However, for such an ambitious project, efficient catalysts for H2 and CO2 conversion are required. In this context, considerable efforts have been directed towards the understanding and control of biocatalyst shaped by nature to efficiently convert H2 and CO2. Screening the biodiversity allowed to identify two valuable enzymes for such reactions. The Carbon Monoxide Dehydrogenase (CODH), key enzyme for reversible CO2 conversion was isolated from the thermophilic bacteria Carboxydothermus Hydrogenoformans (Ch), while the membrane-bound hydrogenase (MbH1) key enzyme for H2 conversion was isolated from the hyperthermophilic bacteria Aquifex aeolicus (Aa). Besides their common isolation from extremophilic bacteria, those enzymes share outstanding common properties such as high affinity for their substrate (µM range), high turnover rates (>10000s-1) and very small overpotential (< 60mV). Moreover, structural data are available for both enzymes revealing a common architecture organized around [Ni-Fe]-dependant active sites connected to hydrophobic channels for substrates/products diffusion, proton transfer pathways and [Fe-S] cluster network for fast electron transfer. Therefore those enzymes stood up as perfect model to understand H2 and CO2 conversion. Due to their similarities, both enzymes can be investigated with the same range of techniques, however while the CODH field is still in its infancy despite decades of research, the hydrogenase field enjoys a wider community carrying the research a few steps ahead in terms of fundamental knowledge and applications. In this work, both enzymes have been investigated with a broad range of complementary techniques including electrochemistry, spectroscopy, atomic force microscopy and theoretical calculations. A deeper insight into CODH’s catalytic and inhibition mechanism will be given while rational MbH1 immobilization onto electrode for efficient H2 oxidation and a prototype of H2/O2 biofuel cell will be presented.
After graduating a master in Bioinformatics, Structural Biochemistry and Genomics, Alexandre Ciaccafava obtained a PhD in structural biology in the laboratory of Bioenergetics and Protein Engineering (BIP) UMR 7281, Marseille, France, focusing on the Functional immobilization of the membrane bound hydrogenase from the hyperthermophilic bacterium Aquifex aeolicus. Then he moved to Berlin for a Postdoc in the Max Volmer Laboratorium , Technische Universität Berlin, UniCat Cluster of excellence, to investigate the anaerobic CO-dehydrogenase from the hydrogen producing bacteria Carboxydothermus hydrogenoformans with infrared spectroscopy.
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