Heterogeneous Structure Regulated by Selection Pressure on Bacterial Adhesion Optimized the Viability Stratification Structure of Electroactive Biofilms.

Abstract

As the core of microbial fuel cells (MFCs), the components and structure of electroactive biofilms (EABs) are essential for MFC performance. Bacterial adhesion plays a vital role in shaping the structure of EABs, but the effect of bacterial adhesion under selection pressure on EABs has not been systematically studied. Here, the response of the composition, structure, and electrochemical performance of EABs to the selective adhesion pressure due to the selective coordination of Fe(III) and Co(II) with thiol and the different affinities for bacteria on hybrid electrodes (Fe1Co, Fe4Co, and Fe10Co) were comprehensively investigated. Compared with carbon cloth (CC), the appropriate selective adhesion pressure of Fe4Co activated the dead inner core of EABs and optimized their viability stratification structure. Both the total viability and the viability of the inner core layer in the Fe4Co EAB (0.67, 0.70 ± 0.01) were higher than those of the CC (0.46, 0.54 ± 0.01), Fe1Co (0.50, 0.48 ± 0.03), and Fe10Co (0.51, 0.51 ± 0.03). Moreover, a higher proportion of proteins was detected in the Fe4Co EAB, enhancing the redox activity of extracellular polymeric substances. Fe4Co enriched Geobacter and stimulated microbial metabolism. Electrochemical analysis revealed that the Fe4Co EAB was the most electroactive EAB, with a maximum power density of 2032.4 mW m-2, which was 1.7, 1.3, and 1.1 times that of the CC (1202.6 mW m-2), Fe1Co (1610.3 mW m-2), and Fe10Co (1824.4 mW m-2) EABs, respectively. Our findings confirmed that highly active EABs could be formed by imposing selection pressure on bacterial adhesion.