Integrated Biocatalysis in Microbial Fuel Cells: Coupling Saccharomyces cerevisiae Fermentation and Acetobacter aceti Oxidation for Biomass Valorization

Microbial fuel cells (MFCs) convert the chemical energy of biomass into electricity through microbially driven redox reactions. We evaluated a single-chamber, membrane-less MFC fed with sugarcane molasses and inoculated with a two-member consortium: Saccharomyces cerevisiae (glucose → ethanol fermentation) and Acetobacter aceti (ethanol → acetate oxidation). Three anode–cathode pairs were tested—bronze–Zn, copper–Zn, and graphite–Zn—across 27 units and 20 operating cycles. During ethanol oxidation, A. aceti oxidizes ethanol to acetic acid and, in our configuration, this biocatalytic step is designed to contribute electrons to the bronze, copper, or graphite anodes. These electrons, together with those generated by galvanic reactions in the electrode pair, flow through the external circuit to the zinc cathode, where oxygen reduction closes the circuit. The cells reached open-circuit potentials > 0.8 V, with performance following the hierarchy graphite–Zn > copper–Zn > bronze–Zn, consistent with the superior biocompatibility and lower corrosion of carbonaceous anodes. Multivariate analysis using PLS-SEM confirmed that redox indicators and electrode composition were strong determinants of voltage output (R2 = 0.911) and demonstrated high predictive relevance (Q2 = 0.906) for the voltage construct. These findings show that coupling yeast fermentation with acetic acid–bacteria oxidation enables synthetic-mediator-free electron transfer in a simple single-chamber configuration and shows that electrode material selection is a primary lever for achieving stable potentials for biomass valorization.