The mechanism of neutral red-mediated microbial electrosynthesis in Escherichia coli: menaquinone reduction
By Timothy D. Harrington and Vi N. Tran and Abdelrhman Mohamed and Ryan Renslow and Saeid Biria and Lisa Orfe and Douglas R. Call and Haluk Beyenal
Published in Bioresource Technology
2015
Abstract
The aim of this work was to elucidate the mechanism of mediated microbial electrosynthesis via neutral red from an electrode to fermenting Escherichia coli cultures in a bioelectrochemical system. Chemical reduction of NAD+ by reduced neutral red did not occur as predicted. Instead, neutral red was shown to reduce the menaquinone pool in the inner bacterial membrane. The reduced menaquinone pool altered fermentative metabolite production via the arcB redox-sensing cascade in the absence of terminal electron acceptors. When the acceptors DMSO, fumarate, or nitrate were provided, as many as 19% of the electrons trapped in the reduced acceptors were derived from the electrode. These results demonstrate the mechanism of neutral red-mediated microbial electrosynthesis during fermentation as well as how neutral red enables microbial electrosynthesis of reduced terminal electron acceptors.