Interfacing nitrogen biochemistry with electrochemical output in Saccharomyces cerevisiae microbial fuel cells

Microbial fuel cells (MFCs) utilize microbial metabolism to convert organic substrates into electrical energy. Saccharomyces cerevisiae presents a promising eukaryotic biocatalyst due to its fermentative capacity and non-pathogenic nature, yet its electron transfer efficiency remains a major bottleneck. This study evaluates the influence of nitrogen source variation, peptone, tryptone, and bovine serum albumin (BSA) at concentrations of 1, 2.5, and 5 mg.mL^-1 on the electrochemical performance of Saccharomyces cerevisiae-based MFCs. Half-cell analyses, including cyclic voltammetry and rate-determining step (RDS) assessments, revealed diffusion-controlled electron transfer via cytochromes. The highest electron transfer rate constant (K_s) was obtained with peptone 5 mg.mL^-1 (1.61 ± 0.285 s^-1), followed by tryptone 1 mg.mL^-1 (1.53 ± 0.332 s^-1) and BSA 1 mg.mL^-1 (0.95 ± 0.055 s^-1). Full-cell experiments showed maximum voltage outputs of 0.132 V (peptone 5 mg.mL^-1), 0.117 V (tryptone 1 mg.mL^-1), and 0.039 V (BSA 1 mg.mL^-1), and corresponding peak power densities of 46.6, 44.0, and 7.1 mW m^-2. SEM confirmed enhanced biofilm formation with increased nitrogen concentration, supporting stronger electrochemical activity. These results highlight nitrogen source optimization as a strategic approach to enhance microbial electron transfer and energy yield in yeast-based MFC systems.