Spectroelectrochemical analysis of intact microbial biofilms for sustainable energy production

Metal-respiring bacteria are microorganisms capable of oxidizing organic compounds present in domestic and industrial wastewater and transferring the electrons to insoluble electron acceptors, such as solid metal oxides or electrodes (see scheme below). The peculiar behavior of these bacteria has led to their application as catalysts in bioelectrochemical systems (BESs): a sustainable technology coupling energy production with bioremediation. Crucial for the functioning of BESs is the complex protein architecture responsible for the electron transfer (ET) across the bacteria/electrode interface. The ET pathway involves several multiheme redox proteins denoted as outer membrane cytochromes (OMCs).

These OMCs are studied by a combination of surface-enhanced resonance Raman (SERR) spectroscopy and electrochemistry (Millo et al., Angew. Chem. Int. Ed.2011, 2625-). This special Raman spectroscopic technique can be employed in vivo and reveals unprecedented structural information about the heme cofactors of OMCs embedded in aggregations of living bacteria (i.e microbial biofilms) grown on electrodes. Electrochemical measurements performed in combination with SERRS allow controlling and monitoring the activity of the microbial biofilm.

This research project aims at understanding the factors controlling the heterogeneous ET across bacteria/electrode interfaces by probing (i) structural information about the OMCs, (ii) the thermodynamics and the kinetics of the ET process, and (iii) the influence of soluble redox mediators competing with OMCs.

This project will contribute to elucidate the function/structure relationship of OMCs in living cells, providing unique insight into the ET across the bacteria/electrode interface. Progress in this topic is expected to have considerable impact in the field of sustainable energy production.

Spectrochemical analysis

 

Schematic representation of a microbial cell attached to an electrode. In this scheme, the ET occurs via the outer membrane cytochromes (OMCs).

 

Contact: Diego Millo