Strategic improvement of Shewanella oneidensis for biocatalysis: Approach to media refinement and scalable application in a microbial electrochemical system

Microbial electrochemical systems offer a sustainable method for the conversion of chemical energy into electrical energy or hydrogen and the production of valuable compounds, contributing to the development of a bio-based economy. This study aimed to enhance the performance of anodic bioelectrochemical systems by improving the current density of Shewanella oneidensis as a biocatalyst through strain modification and medium refinement. The genetic modification, combining the prophage deletion and overexpression of the speC gene, resulted in a 4.2-fold increase in current density compared to the wild type. Furthermore, medium refinement and incorporating riboflavin, led to an additional 5.7-fold increase in current density. The application of the modified strain and medium in a scalable microbial electrolysis cell resulted in a current density of 1.2 A m^-², similar to what was achieved previously with an S. oneidensis and Geobacter sulfurreducens co-culture, substantiating the substantial performance increase for a pure culture of S. oneidensis. Furthermore, S. oneidensis was shown to grow in medium containing up to 500 mM sodium chloride and increasing the salt concentration to 400 mM had a minor influence on growth but significantly lowered the cell voltage of the MEC system.