Background: Extracellular electron transfer ( EET ) is essential in improving the power generation performance of electrochemically active bacteria ( EAB ) in MFCs. Klebsiella has been proved to be an EAB capable of EET. Here, we cover the anode of MFC-1 with a layer of microfiltration membrane to block the effect of the biofilm mechanism, and then explore the EET of the electron mediator mechanism of Klebsiella quasipneumoniae sp.203 and electricity production performance of a K.quasipneumoniae sp.203-inoculated MFCs.
Results: Herein, we covered the anode of microbial fuel cells (MFCs) with a layer of microfiltration membrane to block the effect of the biofilm mechanism, and then explore the EET of the electron mediator mechanism of K.quasipneumoniae sp.203 and electricity production performance. In the absence of short-range electron transfer, we found that K.quasipneumoniae sp.203 can still produce certain power generation efficiency and redox activity. It was proved that in the case that EAB cannot attach to the growth anode, K.quasipneumoniae sp.203 can still perform EET through the electron mediator mechanism. To further verify the effect of electron mediators on electrochemical performance of MFCs, in the first cycle of well-functioning MFCs, the self-produced sterile supernatant was added to the different stages of electricity generation performance. We found that adding electron mediators during the rising phase, the MFCs can reach a maximum output voltage of 442mV in about 24 hours, which is about 70mV higher than MFC-Normal. Therefore, the addition of electron mediators can effectively improve the electrical performance in the stable growth stage of anode EAB in MFCs. Finally, we combined the CV analysis and HPLC-MS to analyze the anode supernatant of MFCs. It was speculated that K.quasipneumoniae sp.203 produced more than one electron mediator, which were 2,6-DTBHQ, 2,6-DTBBQ, ACNQ and DHNA.
Conclusions: To the best of our knowledge, the three modes of EET did not exist separately. K.quasipneumoniae sp.203 will adopt the corresponding electron transfer mode or multiple ways to realize EET according to the living environment to improve electricity generation performance.