Objectives: To investigate the contribution of direct electron transfer mechanisms to electricity production in microbial fuel cells by physically retaining Shewanella oneidensis cells close to or away from the anode electrode.
Results: A maximum power output of 114 ± 6 mWm(-2) was obtained when cells were retained close to the anode using a dialysis membrane. This was 3.5 times more than when the cells were separated away from the anode. Without the membrane the maximum power output was 129 ± 6 mWm(-2). The direct mechanisms of electron transfer contributed significantly to overall electron transfer from S. oneidensis to electrodes, a result that was corroborated by another experiment where S. oneidensis cells were entrapped in alginate gels.
Conclusion: S. oneidensis transfers electrons primarily by direct electron transfer as opposed to mediated electron transfer.
Keywords: Cell immobilisation; Dialysis membrane; Direct electron transfer; Extracellular electron transfer; Mediated electron transfer; Microbial fuel cell; Shewanella oneidensis.