Engineered Shewanella oneidensis-reduced graphene oxide biohybrid with enhanced biosynthesis and transport of flavins enabled a highest bioelectricity output in microbial fuel cells

Low rate of extracellular electron transfer (EET) of exoelectrogens was a major bottleneck in restricting the performance of the microbial fuel cell (MFC) from practical applications. We used synthetic biology approaches (promoter and ribosome binding site (RBS) engineering, and cell surface engineering) to rationally design Shewanella oneidensis for enhanced flavins biosynthesis and transportation in a hydrophobic chassis to boost its EET rate and performance. Graphene oxide (GO) was subsequently used to construct an engineered Shewanella-reduced GO (rGO) 3D self-assembled biohybrid, which dramatically enhanced the thickness and cell numbers in the electroactive biofilm on the anode. Meanwhile, the absorption of flavins on the rGO sheets could not only enhance the pi-pi interaction, but also increase the local concentration of flavins, which could enhance electron shuttle (flavins)-mediated EET rate in the anodic biofilm. As a result, the maximum output power density reached 2.63 W/m(2) (similar to 18.8-folds higher than that of the wild-type S. oneidensis), the highest record of the electricity output of MFCs inoculated with S. oneidensis. Meanwhile, the inward current density of this 3D self-assembled biohybrid biofilm reached 18.78 A/m(2).