Enhancing microbial electrosynthesis by releasing extracellular polymeric substances: Novel strategy through extracellular electron transfer improvement

Microbial electrosynthesis (MES) is a promising process in which microbes obtain electrons from electrodes, producing high value-added chemicals from CO₂. Electrons from the cathode are the only energy source for reducing CO₂; thus, the electron transfer rate is the key to the conversion efficiency of the entire MES system. Here, we report a strategy that promotes the release of extracellular polymeric substances (EPSs) by adding a surfactant to enhance microbial extracellular electron transfer (EET) in an MES system. The addition of the nonionic surfactant Tween 80 not only enables the cathode biofilm to secrete more EPSs, and thus, improve its electrochemical activity, but it also adjusts the composition of the mixed microbial community to promote the enrichment of the primary acetogen, namely, Acetobacterium. Consequently, the acetate production rate of the MES system with 80 mg/L Tween 80 addition was 1.42 times higher than that of the control, and its coulombic efficiency increased from 47.12 ± 2.71 % to 76.33 ± 1.08 %. This new strategy for releasing EPSs via surfactant treatment improves EET, and consequently, enhances MES efficiency.