In Situ Tuning the Structure of Geobacter Biofilm for Bioelectricity Enhancement

Electroactive biofilms show great promise in bioenergy production, bioremediation, wastewater treatment, and bioelectronics. However, their applicability is impeded by energy dissipation owing to the electron transfer resistance in electroactive biofilms. Herein, we tuned the structure of a Geobacter sulfurreducens anode biofilm in situ to reduce the electron transfer resistance. Therein, the pili of G. sulfurreducens were genetically engineered with six-histidine tags, and nickel(II) ions were supplied thereafter to trigger the formation of histidine:nickel biohybrid pili via histidine-nickel coordination bonds. We reported that these treatments resulted in the intertwining of pili from different cells, which contributed to the formation of a highly structured biofilm and increased the concentration of electroactive sites in the microenvironments of the biofilm. Electrochemical analyses demonstrated that the treatments decreased the electron diffusion resistance as well as the interface electron transfer resistance and mass transfer resistance, all of which contributed to an approximately 2.4 times increase in current generation. Considering the universality of pili in microorganisms and the strong coordination interaction between histidine tags and nickel(II) ions, this study provides a general method to reduce energy dissipation in electroactive biofilms and suggests a technique to manipulate the biofilm structure, which is significant in biofilm-based technologies.