Inocula selection in microbial fuel cells based on anodic biofilm abundance of Geobacter sulfurreducens

Abstract

Microbial fuel cells (MFCs) rely on microbial conversion of organic substrates to electricity. The optimal performance depends on the establishment of a microbial community rich in electrogenic bacteria. Usually this microbial community is established from inoculation of the MFC anode chamber with naturally occurring mixed inocula. In this study, the electrochemical performance of MFCs and microbial community evolution were evaluated for three inocula including domestic wastewater (DW), lake sediment (LS) and biogas sludge (BS) with varying substrate loading (Lsub) and external resistance (Rext) on the MFC. The electrogenic bacterium Geobacter sulfurreducens was identified in all inocula and its abundance during MFC operation was positively linked to the MFC performance. The LS inoculated MFCs showed highest abundance (18 ± 1%) of G. sulfurreducens, maximum current density (Imax= 690 ± 30 mA•m-2) and coulombic efficiency (CE = 29 ± 1%) with acetate as the substrate. Imax and CE increased to 1780 ± 30 mA•m-2 and 58 ± 1%, respectively, after decreasing the Rext from 1000 Ω to 200 Ω, which also correlated to a higher abundance of G. sulfurreducens (21 ± 0.7%) on the MFC anodic biofilm. The data obtained contribute to understanding the microbial community response to Lsub and Rext for optimizing electricity generation in MFCs.

Cathode Assessment for Maximizing Current Generation in Microbial Fuel Cells Utilizing Bioethanol Effluent as Substrate

“…The EIS data for the anode and cathode thus explained that the FeC-MFC gave the highest maximum current density, followed by the AiC-MFC and the DOC-MFC. It has been found that substrate loading rate and external resistance determines the maximum charge and current, which can be generated in a MFC [5,12]. Increasing substrate loading rate at decreasing external resistance was investigated to optimize electricity generation in the MFCs as shown in Figure 5.…”

“…Bioethanol effluent is suitable as substrate for current generation in MFCs when the MFC is initiated using acetate [6]. However, further performance improvement can be achieved by the use of inocula from different environmental sources such as lake sediment [5]. In addition, an efficient cathode process is required before the use of MFC for current generation is feasible.…”

“…Typically the reduction at the cathode surface involves reduction of O 2 to H 2 O [2]. The latest research has mainly focused on the bacterial metabolism on the anode electrode surface [3], improving anode electrode materials [4], optimizing the anode inoculum [5], speeding up the initiation through selection of substrate [6], and on improving the reactor design and configuration for maximizing conversion efficiency and output [1].…”

A Viable Electrode Material for Use in Microbial Fuel Cells for Tropical Regions

“…The selection and development of AC was targeted at introducing a cost-effective electrode material for use in MFCs. The successful inoculation of AC indicated that an improvement in power generation can be achieved through post-inoculation cycles [24,25]. Numerous cycles of operation are known to improve biofilm and increase the total power generated.…”

“…Bacterial species found in AC biofilms also included G. sulfurreducens, E. cancerogenus and D. acetexigens. In the MFC study by Sun et al, all the identified bacteria except D. acetexigens were identified, which indicates a large similarity in the microbial community due to the use of wastewater, even though the inocula have been obtained from Denmark, Europe in that study [24]. EIS was thereby a fast and useful technique for evaluation of the electrode materials and the inocula.…”