Improvement of microbial extracellular electron transfer via outer membrane cytochromes expression of engineered bacteria

Abstract

The effective contact between proteins on the electroactive membranes or nanowires determines the efficiency of the electroactive in bioelectrochemical systems (BES) biofilm. However, most electroactive biofilms are multi-layer bacterial aggregates, and the microorganisms in the outer layer cannot directly contact the electrode surface electron transfer. Herein, we construct a genetically engineered bacterium (GEB) that can express outer membrane cytochrome OmcA to improve the microbial extracellular electron transfer in the biofilm. The engineered bacterium improves the maximum power density of the mixed bacteria microbial fuel cell (MFC) by 2.36 times to 3.76 A cm−2, and increases the current density to 1.98 W m−2. This improved behavior was stable for at least three feeds. Adding the engineered bacteria generates a more compact biofilm structure and significantly improves the electrochemical performance of the anode biofilm. The engineered bacteria with the electron transfer function also increase the content of the OmcA gene in the bacterial community, thereby promoting the microbial extracellular electron transfer and increasing the proportion of electrogenic bacteria in the biofilm. With its expression of the conductive protein, the GEB can effectively improve the extracellular electron transfer efficiency of the outer layer bacteria in the biofilm of the MFC. Our study provides a new choice for building an efficient electrochemical system.