Horizontal microbial fuel cell system producing biosurfactants in response to current generation from waste cooking oil as a fuel

Abstract

Microbial fuel cells (MFCs) are recognised as a platform technology, where several processes take place at the same time, including electricity generation. In this study, for the first time, the horizontal MFC system is proposed, capable of synthesizing biosurfactants, where their quantity is directly correlated with the power production. Waste rapeseed oil was used as a sustainable fuel to drive both processes. Initially, all tested MFCs worked as vertical systems where only negligible power generation was noted. Therefore, the MFCs were reconfigured to work as passive, horizontally-aligned system while vertical, agitated control was also investigated. Only a slight reduction of surface tension, resulted from biosurfactant synthesis, was observed in the anolyte in an agitated vertical MFC system, which produced a maximum power density of 2.37 W m−3. The horizontal MFC system led to an increase in electricity production of 104.7 % to 4.84 W m−3. Furthermore, an increase in current generation was accompanied by an increase in biosurfactant production which was observed by the drop of surface tension in anodic chamber to 50.7 mN m−1. Significant, direct correlation (r = -0.77) between power and biosurfactant generation was noted. The results showed that it is possible to establish the energy net positive production of biosurfactants, through an appropriately designed MFC system, and provided the first evidence, that the biosynthesis process is a direct response of current generation. These results represent a novel approach in monitoring of the biosynthesis of surfactants solely through the use of electrical signal and design of bioelectrochemical systems. This process occurs through electrofermentative pathways, assisted with the extracellular electron transport.