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Title: Optimizing electroactive bacteria for the practical implementation of bioelectrochemical systems

Speaker: Catarina Paquete

Affiliation: Ricardo Louro Lab, ITQB NOVA

Abstract: 

The increase of world’s energy demand and the requirement of decreasing the use of fossil fuels have led to the development of alternative energy sources. Bioelectrochemical systems (BES) are currently emerging as a versatile sustainable technology for electricity production. These systems allow the conversion of chemical energy stored in organic wastes (e.g. wastewaters) into electricity or value-added compounds using microorganisms as catalysts. It is the ability of the microorganism (so-called electroactive) to exchange electrons with an electrode that is at the heart of these systems. Despite their promising potential, BES have not yet achieved economic viability for commercial applications, being still confined to lab-scale research projects. This is mainly due to the low power densities that can be obtained by these systems, being the microbial electron transfer rate to electrodes one of the dominant factors limiting current output.

Electroactive organisms use multiheme c-type cytochromes to exchange electrons with the electrode, and it has been shown that electron transfer processes performed by these proteins are among the main factors in controlling the electron transfer rate to electrodes. The detailed characterization of the electron transfer processes performed by these proteins are mainly obtained using pure proteins, neglecting important parameters such as the cellular milieu, that can influence protein folding, stability and even the reactivity of the proteins. Toward this, in vivo studies have become imperative to explore the molecular basis of the electron transfer processes performed by the multiheme cytochromes in living cells, and identify the factors that limit electron transfer in extracellular electron transfer pathways.

This presentation will be focused on the recent in vivo studies to explore the electron transfer processes performed by multiheme cytochromes in living cells, and on the different approaches used to enhance cytochromes and improve metabolically driven electron transfer rates to the level needed for the practical implementation of BES.