In the present study, we found that our isolate Shewanella decolorationis NTOU1 is able to degrade acetate under anaerobic condition with concomitant implementation of extracellular electron transfer (EET). With +0.63 V (vs. SHE) poised on the anode, in a 72-h experiment digesting acetate, only 2 mM acetate was consumed, which provides 6% of the electron equivalents derived from the initial substrate mass to support biomass (5%) and current generation (1%). To clarify the effects on EET of the addition of electron-shuttles, riboflavin, anthraquinone-2,6-disulfonate (AQDS), hexaammineruthenium, and hexacyanoferrate were selected to be spiked into the electrochemical cell in four individual experiments. It was found that the mediators with proton-associated characteristics (i.e., riboflavin and AQDS) would not enhance current generation, but the metal-complex mediators (i.e., hexaammineruthenium, and hexacyanoferrate) significantly enhanced current generation as the concentration increased. According to the results of electrochemical analyses, the i-V graphs represent that the catalytic current induced by the primitive electron shuttles started at the onset potential of −0.27 V and continued increasing until +0.73 V. In the riboflavin-addition experiment, the catalytic current initiated at the same potential but rapid saturated beyond −0.07 V; this indicated that the addition of riboflavin affects mediator secretion by S. decolorationis NTOU1. It was also found that the current was eliminated after adding 48 mM N-acetyl-L-methionine (i.e., the cytochrome inhibitor) when using acetate as a substrate, indicating the importance of outer-membrane cytochrome.
CITATION STYLE
Li, S. L., Wang, Y. J., Chen, Y. C., Liu, S. M., & Yu, C. P. (2019). Chemical characteristics of electron shuttles affect extracellular electron transfer: Shewanella decolorationis NTOU1 Simultaneously Exploiting Acetate and Mediators. Frontiers in Microbiology, 10(MAR). https://doi.org/10.3389/fmicb.2019.00399
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