Microbial fuel cells (MFCs) contain micro-organisms which oxidize organic matter to generate power. These fuel cells present a convenient source of power generation in environments rich in organic matter. However, they do not yet function at high enough efficiencies to be industrially viable. Conjugate oligo-electrolytes (COEs) have been shown previously to be able to increase the efficiency of MFCs. These molecules have semi-conductive properties, and embed into the membrane of the microbes. The mechanism by which COEs increase efficiency is poorly understood, presenting a barrier to future optimization. Previous research has demonstrated an increase in current generation in a complex media. Here, a similar effect has been demonstrated in a defined media. The consumption of substrate can be monitored to show that COES enhance the production of current in non-fermentable pathways without a corresponding increase in substrate consumption. This provides insight into the effects of COEs on the metabolism of cells, and it indicates the mechanism by which COEs increase current is not linked to an increase in the rate of substrate consumption. This will inform further research into the mechanism by which COEs increase current, suggesting a future focus on electron transference and mediator production.