Baker's Yeast-Based Microbial Fuel Cell Mediated by 2-Methyl-1,4-Naphthoquinone

Abstract

Microbial fuel cell (MFC) efficiency depends on charge transfer capability from microbe to anode, and the application of suitable redox mediators is important in this area. In this study, yeast viability experiments were performed to determine the 2-methyl-1,4-naphthoquinone (menadione (MD)) influence on different yeast cell species (baker's yeast and Saccharomyces cerevisiae yeast cells). In addition, electrochemical measurements to investigate MFC performance and efficiency were carried out. This research revealed that baker's yeast cells were more resistant to dissolved MD, but the current density decreased when yeast solution concentration was incrementally increased in the same cell. The maximal calculated power of a designed baker's yeast-based MFC cell anode was 0.408 mW/m² and this power output was registered at 24 mV. Simultaneously, the cell generated a 62-mV open circuit potential in the presence of 23 mM potassium ferricyanide and the absence of glucose and immobilized MD. The results only confirm that MD has strong potential to be applied to microbial fuel cells and that a two-redox-mediator-based system is suitable for application in microbial fuel cells.

Keywords: 2-methyl-1,4-naphthoquinone; Saccharomyces cerevisiae; baker’s yeast cells; biofuel cell; graphite rod electrode; microbial fuel cell.

Figure 1

Variation of optical density (OD) during the determination of growth curves of yeast. (a) A comparison of growth curves: (i) yeast I—Saccharomyces cerevisiae with 3.75 mM menadione (MD); control I—Saccharomyces cerevisiae in the liquid YPG agar medium; (b)—a comparison of growth curves: (ii) yeast II—baker’s yeast with 3.75 mM MD; control II—baker’s yeast in the liquid YPG agar medium.

Figure 2

Antimicrobial activity of MD solution evaluated by the agar well diffusion method against yeast cells: (a)—yeast I ((i) Saccharomyces cerevisiae) at 30 °C); (b)—yeast II ((ii) baker’s yeast) at 30 °C; (c)—the histogram presents the radius of the inhibition zone at 3.75 mM concentration of MD in the solution.

Figure 3

Cyclic voltammograms recorded with the MD-modified anode at different yeast concentrations in the phosphate–acetate buffer solution. The scan rate was 0.1 V/s.

Figure 4

(a) Cyclic voltammograms registered by the yeast-modified graphite electrode at different MD concentrations. Measurements were performed in the phosphate–acetate buffer solution with the 37 mM potassium ferricyanide and 31 mM glucose. A scan rate of 0.1 V/s and a potential step of 0.01 V was applied; (b) reduction peak potentials at 0.15 V and 0.35 V vs. used MD concentration recorded using the yeast-modified graphite electrode (results were fitted using Hill’s function (Equation (1)). Measurements were performed in a three-electrode-based electrochemical cell.

Figure 5

(a) Cyclic voltammograms of graphite electrode with immobilized MD and yeast cells registered in the phosphate–acetate buffer solution (BS) with the presence and absence of glucose (Glc) and potassium ferricyanide (FCN); (b) reduction peak current density at 0.4 V vs. used MD concentration recorded using an immobilized MD- and yeast-modified graphite electrode (results were fitted using Hill’s function (Equation (2)). Measurements were performed in a three-electrode-based electrochemical cell in the phosphate–acetate buffer solution with 23 mM glucose and 23 mM potassium ferricyanide.

Figure 6

Data from replicated experiments with the MD and yeast-modified electrode.

Figure 7

(a) Potential dependence on applied load; (b) calculated power density dependence on the generated potential in a single-compartment-based Microbial fuel cell (MFC), which consisted of an MD- and yeast-modified anode and a bare graphite cathode immersed in the phosphate–acetate buffer solution containing 23 mM of potassium ferricyanide and variable concentrations of glucose: 0 mM, 1.58 mM, 7.8 mM, 14.08 mM, 23.26 mM, and 30.77 mM.