Supporting information for the manuscript

CO2 reduction by mixed and pure cultures in microbial electrosynthesis using an

assembly of graphite felt and stainless steel as cathode

Suman Bajracharya1,2; Annemiek ter Heijne2; Xochitl Dominguez1; Karolien Vanbroekhoven1;

Cees J. N. Buisman2; David P.B.T.B. Strik2,*; Deepak Pant1,*

1 Separation & Conversion Technologies, Flemish Institute for Technological Research

(VITO), Mol, Belgium

2 Sub-department of Environmental Technology, Wageningen University, Wageningen, The

Netherlands

* Corresponding authors.

Summary

S1: Bioelectrochemical reactor configuration for mixed culture experiments S2: Bioelectrochemical reactor configuration for pure culture experiments S3: Cyclic Voltammogram (CV) of mixed culture reactor during the operational stage S4: Cyclic Voltammogram (CV) of C. ljungdahlii H-type reactor during the

operational S5: Scanning electron micrograph of biocathode and proton exchange membrane

(PEM) from H-type reactor

S1: Bioelectrochemical reactor configuration for mixed culture experiments

Figure S1: Circular bioelectrochemical reactor/cell setup for mixed culture MES. (a) Schematic diagram of experimental setup. (b) Photograph of circular cell. (c) Photograph of cathode - assembly of graphite felt and stainless steel mesh (view from catholyte side)

S2: Bioelectrochemical reactor configuration for pure culture experiments

Potentiostat

e- e-

Anode Cathode

Proton exchange membrane

Stainless steel mesh

Graphite felt

DSA Electrical wire

Bacterial cell

Gas bubble

Reference electrode

Anode chamber

Cathode chamber

Proton exchange membrane

(b) (a)

(c)

graphite felt

Stainless steel mesh

Figure S2: H-type bioelectrochemical reactor/cell for pure culture MES. (a) Schematic diagram of experimental setup and (b) an H-type reactor photograph (c) Photograph of Cathode- graphite felt and stainless steel mesh assembly

S3: Cyclic Voltammogram (CV) of mixed culture reactor during the operational stage

Figure S3: Cyclic Voltammogram (CV) of mixed culture reactor during the operational stage at -1.1 V/Ag/AgCl. Cyclic voltammetry was carried out at 1 mV.s-1 scan rate. Hydrogen evolution occurring at more negative potential than -1 V/Ag/AgCl.

S4: Cyclic Voltammogram (CV) of C. ljungdahlii H-type reactor during the operational

Figure S4: Cyclic Voltammogram (CV) of C. ljungdahlii H-type reactor during the operational stage at -0.9 V/Ag/AgCl. Cyclic voltammetry was carried out at 1 mV.s-1 scan rate.

The change of slope at -0.9 V/Ag/AgCl indicates the start of hydrogen evolution

S5: Scanning electron micrograph of biocathode and proton exchange membrane (PEM) from H-type reactor

(A) (B)

(C) (D)

Figure S5: Scanning electron micrograph of biocathode and proton exchange membrane (PEM) from H-type cell with C. ljungdahlii MES taken at the final stage of Batch 3. Carbon felt from the biocathode (A & B). No bacterial attachment on the carbon felt is visible in the image. Rod shaped bacteria attached to the PEM (C & D). Round globular shapes are the precipitations of salts on PEM.