Acclimation Strategy Using Complex Volatile Fatty Acid Mixtures Increases the Microbial Fuel Cell (MFC) Potential

The start-up of microbial fuel cells (MFCs) requires biofilm development onto electrodes and acclimation of the microbial community to specific substrates. This process is time-consuming and shows low effectivity when complex substrates are utilized. The varying proportions and complex mixtures of volatile fatty acids (VFAs) in bioprocess effluents makes it difficult to predict the power output of VFA-based MFCs when this technology is coupled to a previous bioprocess. In this work, the effect of the degree of reduction of single VFAs on MFC potential was investigated, and a novel acclimation procedure involving the feeding of gradually more complex VFA mixtures is proposed. The power output obtained with butyric acid (6.1 ± 2 mW m−2) was higher than that obtained with propionic acid (5.0 ± 1 mW m−2), as expected based on their degree of reduction. The MFC potential generated by an acetic acid-fed MFC reached 60 mV, but an acetic-butyric acid mixture reduced the cell potential by one order of magnitude. The subsequent addition of propionic acid to the acetic-butyric mixture increased the MFC potential from 1.9 ± 0.1 mV to 35 ± 10 mV in sequential feeding cycles. Consequently, the feeding sequence of acetic, acetic-butyric, and acetic-butyric-propionic acids is proposed as an efficient strategy for the acclimation of MFCs to complex substrates. © 2017 Wiley-VCH Verlag GmbH %26 Co. KGaA, Weinheim

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