Bioanodes/biocathodes formed at optimal potentials enhance subsequent pentachlorophenol degradation and power generation from microbial fuel cells

• Bioanodes formed at +200 mV and biocathodes at −300 mV enhanced MFC performances.
• Startup times were reduced to 320 h (bioanode) and 420–440 h (biocathodes).
• PCP degradation rates and power generation were enhanced.
• Recalcitrant organic degraders and/or exoelectrogens/electrotrophs were observed.

Bioanodes formed at an optimal potential of 200 mV vs. SHE and biocathodes developed at − 300 mV vs. SHE in bioelectrochemical cells (BECs) enhanced the subsequent performances of microbial fuel cells (MFCs) compared to the un-treated controls. While the startup times were reduced to 320 h (bioanodes) and 420–440 h (biocathodes), PCP degradation rates were improved by 28.5% (bioanodes) and 21.5% (biocathodes), and power production by 41.7% (bioanodes) and 44% (biocathodes). Accordingly, there were less accumulated products of PCP de-chlorination in the biocathodes whereas PCP in the bioanodes was more efficiently de-chlorinated, resulting in the formation of a new product of 3,4,5-trichlorophenol (24.3 ± 2.2 μM at 96 h). Charges were diverted to more generation of electricity in the bioanodes at 200 mV while oxygen in the biocathodes at − 300 mV acted as a primary electron acceptor. Dominant bacteria known as recalcitrant organic degraders and/or exoelectrogens/electrotrophs included Desulfovibrio carbinoliphilus and Dechlorospirillum sp. on the bioanodes at 200 mV, and Desulfovibrio marrakechensis, Comamonas testosteroni and Comamonas sp. on the biocathodes at − 300 mV. These results demonstrated that an optimal potential was a feasible approach for developing both bioanodes and biocathodes for efficient PCP degradation and power generation from MFCs.

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