Systematically assessing genetic strategies for engineering electroactive bacterium to promote bioelectrochemical performances and pollutant removal

Abstract

Bioelectrochemical system (BES) empowered by electrochemically active microorganisms (EAMs) has a great potential for wastewater treatment. However, their low extracellular electron transfer (EET) capability has restricted the application of BES. In this work, we applied synthetic biology methodology to fundamentally engineer electroactive bacterium for promoted wastewater treatment. At multiple layers, four different genetic engineering strategies, including directly engineering the EET pathways, engineering the bacterial universal messenger, repressing the electron competing reductase, and dynamically managing EET output, were developed and implemented in Shewanella oneidensis, an important model EAM species. The genetic engineered strains improved up to 4.8- and 2.5-fold improvement of current densities over the control in microbial electrosynthesis cell and microbial fuel cell assessments, respectively. Furthermore, using the methyl orange and Cr(VI)-laden wastewaters as the target, the engineered strains exhibited substantially promoted treatment efficiency, achieving up to 18.5- and 5.5-fold over the control. Remarkably, the dynamic control strategy achieved the greatest improvement for wastewater treatment. This study not only provides effective genetic engineering strategies to promote BES performance for wastewater treatment, but also demonstrates the importance of managing EET from the cellular resource partitioning layer for more efficient wastewater treatment.