Flavin Biosynthesis Enhances Extracellular Electron Transfer in Bioengineered Escherichia coli

Area of Science:

• Bioengineering
• Microbial Electrochemistry
• Synthetic Biology

Background:

• Microbial electrochemical technologies (METs) harness microbial metabolism for energy, sensing, and synthesis.
• Efficient charge transfer in engineered microbes like Escherichia coli is crucial for MET advancement.
• Previous research focused on the metal-reducing (Mtr) pathway for direct electron transfer.

Purpose of the Study:

• To engineer Escherichia coli for enhanced charge exchange by combining direct electron transfer with flavin-mediated transfer.
• To investigate the synergistic effects of Mtr pathway and flavin secretion on microbial electrochemical performance.
• To explore novel extracellular electron transfer (EET) mechanisms for multi-modal microbial applications.

Main Methods:

• Engineered Escherichia coli strains by introducing flavin biosynthesis genes alongside the Mtr pathway.
• Quantified flavin secretion (FMN and riboflavin) using spectrophotometry.
• Measured electrical current generated by engineered strains in microbial electrochemical cells.

Main Results:

• Engineered strains exhibited a 3-fold increase in total flavin secretion (FMN and riboflavin) compared to Mtr-only strains.
• Concomitant flavin secretion increased current by ≈3.4-fold (vs. unmodified) and ≈1.5-fold (vs. Mtr-only).
• Strains favoring riboflavin secretion showed the highest current generation.

Conclusions:

• Co-expression of flavin secretion pathways complements the Mtr pathway for enhanced EET.
• This dual-mode EET mechanism offers a robust and versatile approach for microbial electrochemical applications.
• The engineered strains demonstrate potential for improved performance in energy harvesting, biosensing, and biomanufacturing.