Bio-electric field accelerated the formation of electroactive biofilm and the selection of Geobacter during start-up period.

Abstract

Prolonged startup severely restricts practical deployment of microbial electrochemical systems (MESs). Conventional strategies to accelerate electroactive biofilm (EAB) formation require costly chemicals or complex electrode modification. Herein, we report a facile strategy using a sustained low-strength bulk electric field (EF, 8 mV/cm, maintained for 75 % of each operational cycle) to accelerate EAB formation and selectively enrich Geobacter during the start-up period of MES. After 4-day EF acclimation, treated EABs yielded 4.2-fold higher turnover cyclic voltammetry redox current and 41 % lower charge-transfer resistance relative to the no-EF control. The EF-stimulated EAB also reached 1.64-fold higher biomass, with electroactive microorganisms constituting 96.8 % of the biofilm community (64.1 % in controls); Geobacter surged from an initial 1.3 % to 77.0 %, compared with only 32.7 % in controls. Unlike electrode-electrolyte interfacial polarization, the full-volume bulk EF may enrich negatively-charged electroactive bacteria presumably via electric-field-driven directional transport that promotes adhesion and proliferation. This additive-free approach enables mature EAB formation on electrodes within days, representing a promising laboratory-scale concept for prefabricating functional EAB-coated electrodes; further validation is required for real-world on-site MES implementation.

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