Characterization of Electrochemically Active Bacteria Utilizing Redox Response in Microbial Electrolysis Cell

This study focuses on micro-electrochemical screening to select microbial strains capable of directly transfer electrons to the working electrode dependent on specific enzymatic machinery. The main objective of this work is to select and identify promising strains for allow the bioelectrolysis production of hydrogen. To achieve this goal, microbial composites (artificial biofilms), have been developed using Escherichia coli CGE1 from LCPME. CNRS Fransh, Pseudomonas putrifisciens (CIP 69.13) (CIP, Collection Institut Pasteur, Fransh). Shewanella oneidensis MR-1 (ATCC 700550), and Thiobacillus denitrificans, from (ATCC, American Type Culture Collection), each one enclosed in a matrix carbon nanotubes and protamine matrix, forming an artificial biofilm on buckypaper. Cyclic Voltammetry (CV) measurements were performed over a potential range of +0.4 to -0.7V at 5mV/s under 30°C, using a saturated KCl Ag/AgCl reference electrode and a stainless-steel grid counter electrode. For E. coli and P. putrifisciens, the measurement focused on the oxidation of 20mM glucose, while the former bacteria were growth with and without O2. For S. oneidensis and T. denitrificans the focus was on the reduction of fumarate and 20 mM of NaNOH3+, respectively. As results, E. coli and P. putrifisciens species show no notable electrochemical activity, with no signal of glucose oxidation, due to the absence of type C cytochromes in the cytoplasmic membrane, unlike S. oneidensis and T. denitrificans, that demonstrate a direct electron transfer.