Engineering Flavin Synthesis in Bioelectronic E.coli for Multichannel Sensing

Microbes can exchange the electron with their external environment, such as iron and electrode. These extracellular electron transfer processes can be developed into bioelectronic devices, which can convert biochemical information into electrical response. One such example for a bioelectronic sensor is Mtr-expressing E.coli, which incorporated the Mtr pathway from Shewanella oneidensis MR‐1 to report sensing signal as current.^1,2 However, sensing signal in Mtr E.coli is limited to only one output channel. To provide a second reporting channel, we have introduced flavin, which was demonstrated as a redox mediator with different redox potential than Mtr pathway, to have two distinguished redox channels. By engineering the riboflavin pathway from Bacillus subtilis into Mtr-expressing E.coli, we were able to double the extracellular flavin concentration than the single Mtr E.coli. With more flavin production, the signal output as current increased from flavin-Mtr expressing E.coli. We can also distinguish different redox peaks from flavin-Mtr E.coli via electrochemical approaches. To further build up bioelectronics based on flavin-Mtr E.coli, an hydrogel-encapsulated system was utilized as a bioelectronic-capsule. These enhancements open new possibilities for engineering more sophisticated and sensitive techniques, such as multi-channel biosensors.

1. TerAvest, M. A., Zajdel, T. J. & Ajo‐Franklin, C. M. The Mtr Pathway of Shewanella oneidensis MR‐1 Couples Substrate Utilization to Current Production in Escherichia coli. ChemElectroChem (2014).
2. Su, L., Fukushima, T. & Ajo-Franklin, C. M. A hybrid cyt c maturation system enhances the bioelectrical performance of engineered Escherichia coli by improving the rate-limiting step. Biosens. Bioelectron. 165, 112312 (2020).