Synthetic curli enables efficient microbial electrocatalysis with stainless‐steel electrode

Abstract

Microbial electrocatalysis systems (MES) provide a cutting‐edge solution to global problems associated with the environment and energy, but practical applications are hindered by the expensive electrode materials. Although stainless steel (SS) has been proposed as a promising inexpensive candidate, poor cell/SS interaction results in a low performance for MES. Here, a new synthetic biology approach was established for reinforcing the cell/SS interaction. Hybridized curli nanofibers fused with a metal‐binding domain were heterogeneously expressed onto the cell surface, which realized efficient cell binding with the SS electrode. Consequently, it enabled a ~420‐fold improvement of the anodic power output and a substantial enhancement of the cathodic Coulombic efficiency (from 0.6 to 4% to over 80%) with an SS electrode. This work demonstrates low‐cost MES with an SS electrode and introduces a new avenue to engineer the cell/electrode interaction, which is promising for future practical applications of MES.

Surface activated natural wood biomass electrode for efficient microbial electrocatalysis: Performance and mechanism

“…For microbial CO 2 transformation to formic acid, formate dehydrogenase was usually responsible for the catalytic conversion, where intracellular NAD(P)H served as the electron donor 33,34 . It was reported that S. loihica PV‐4 contained the formate dehydrogenase and had high catalytic activity in the cathode of MEC 4,19 . It was speculated that S. loihica PV‐4 could transform CO 2 to formic acid with the extracellular cathodic electron donor (Figure S8).…”

“…The MECs system was constructed in a dual‐chamber bioelectrochemical system, where the CO 2 reduction was carried out in the cathodic chamber as described in previous reports 21 . The anodic chamber of the MECs was filled with 50 mM NaCl and 1 mM H 2 SO 4 , while the cathodic chamber was added with 5 mM bicarbonate (the source of CO 2 ) and cell suspension (OD600 = 1.0) in 50 mM hydroxyethyl piperazineethanesulfonic acid buffer solution (HEPES, pH = 7.0) 19 . Carbon felt (2 cm × 3 cm) was used as the anodic electrode, while CC or BW (1 cm × 2 cm) was used as the cathodic electrode.…”

“…33,34 It was reported that S. loihica PV-4 contained the formate dehydrogenase and had high catalytic activity in the cathode of MEC. 4,19 It was speculated that S. loihica PV-4 could transform CO 2 to formic acid with the extracellular cathodic electron donor (Figure S8). Thus, the production of formic acid from CO 2 by MEC equipped with the wood electrode and inoculated with S. loihica PV-4 was tested.…”

“…Shewanella oneidensis MR-1 (ATCC 700550) or Shewanella loihica PV-4 (ATCC BAA-1088) was cultured in LB broth (peptone 10 g/L, yeast extract 5 g/L, NaCl 5 g/L, pH 7.2) with shaking (150 rpm) at 30 C for about 18 hours. 19,20 The cell culture was centrifuged and the cell pellets were collected. Then, the cell pellets were resuspended with fresh electrolyte (95% M9 salt medium [Na 2 HPO 4 , 6 g/L; KH 2 PO 4 , 3 g/L; NaCl, 0.5 g/L; NH 4 Cl, 1 g/L; MgSO 4 , 1 mM; CaCl 2 , 0.1 mM], 5% LB, 18 mM lactate) 7 at the optical density of 1 (OD600) and used for MFC or MES inoculation.…”

Light-induced Patterning of Electroactive Bacterial Biofilms

“…Prior efforts to direct electroactive biofilm formation on surfaces have focused solely on engineering cell-electrode attachment, rather than patterning, through synthetic biology and materials engineering strategies. These works were based on either (I) enhancing biofilm formation by expressing adhesive appendages on cell surfaces 49,50 and increasing c-di-GMP levels 51,52 or (II) placing complementary chemical or DNA-based structures on substrates and cell surfaces to bond cells to electrodes [53][54][55][56][57] . Compared with these previous works, our strategy does not require electrode pretreatment for electroactive biofilm patterning and can generate robust biofilms with defined dimensions.…”