Energy harvesting from microbial fuel cells: Exoelectrogen pure bacterial culture versus mixed wastewater culture

Microbial fuel cells (MFC)s are electrochemical devices that utilize the metabolic activity of bacteria to drive an electron transfer process that produces a current [1]. This study aims to compare the power generation capabilities of MFCs using exoelectogenic pure bacterial culture and mixed wastewater culture. The pure culture comprises Shewanella algae, known for its ability to produce bacterial nanowires facilitating electron transfer and current generation in MFCs. Conversely, the mixed culture consists of wastewater from dairy plant biological treatment ponds, encompassing a diverse community of microorganisms [2]. Materials and methods Two cylindrical air-cathode double-chamber MFCs were used with carbon felt electrodes. The cathodes contain aerated phosphate buffer and the anodes contain a mixed culture of dairy wastewater and sodium acetate, and a defined medium with lactic acid as fuel substrate. Polarization tests were carried out under an external resistance interval of 10000 Ω to 50 Ω to evaluate MFC performance. Results and discussion As depicted in Fig. 1, the polarization test results indicate that the maximum current produced by mixed culture MFC (6.3 mA) is 5 times higher than that produced by pure culture of Shewanella algae MFC (1.3 mA). Also, Fig. 2 shows that the mixed culture enables the MFC to produce the maximum power out of 354 mW/m², which is 4.7 times greater than the power produced using a pure culture of Shewanella algae (74 mW/m²). The results suggest that biological wastewater is a rich medium for power production in MFCs for various reasons. Firstly, mixed cultures contain a wider range of easily metabolizable organic substrates, providing abundant energy for microbial activity. This results in improved electron transfer processes and electricity production. Secondly, mixed cultures comprise diverse microbial species with different metabolic capabilities, enabling the use of multiple pathways for electron transfer and energy conversion. These diverse metabolic activities within mixed cultures lead to synergistic interactions, ultimately enhancing electron current and increasing power production compared to pure Shewanella algae cultures [3]. Conclusions Microbial fuel cells can generate more bioelectricity from mixed biological wastewater cultures than pure exoelectrogenic bacterial cultures. This superiority is due to the rich organic content of biological wastewater that allows higher electron transfer activity. Fig. 1: Polarization curves of MFCs Fig. 2: Power density curves of MFCs