Table 2.

Overview of selected electro-fermentation attempts of C. acetobutylicum

Parameter	Peguin et al. (1994)	Engel et al. (2019b)	Guerrero et al. (2022)	Hengsbach et al. (2023)	Nailwal et al. (2024)
Butanol titer (g$·$L−1)	6.9	6.7	8.38	9.22	6.67
YButanol/C-source (g$·$g−1)	0.42	0.135 ± 0.005	0.429 ± 0.004	0.207 ± 0.019	N/A
Average increase BtOH (yield or titer) (%)	51 (yield)	31.07 (yield)	33.87a (titer)	20.14 ± 3.66 (yield)	68.86 (titer)
Total solvents (ABE) (g$·$g−1)	0.48	0.141 ± 0.022	N/A	0.348 ± 0.045	N/A
Carbon source (g$·$L−1)	Glucose, 66	Glucose, 45	Glucose, 18	Glucose, 45	Glucose, 20–60
WE material	Carbon rod	Carbon fabric	Graphite rod	Carbon fiber brush	Graphite
WE surface (cm2)	40	8.75	N/A	90	N/A
Reference electrode	NHE	Ag/AgCl (saturated. KCl)	Ag/AgCl (3.0 M)	Ag/AgCl (saturated. KCl)	Ag/AgCl (3.5 M)
Potential (mV)	− 460 to − 660	− 600	− 850	− 800	− 400
Mediator	Methyl viologen	w/o	Neutral red	w/o	w/o
Mode/type	Batch/two-chamber BES	Batch/two-chamber BES	Batch/two-chamber BES	Batch/one-chamber BES	Batch/one-chamber BES
Special aspects			Supplemented with butyrate

^aCalculated according to values from the corresponding reference

ABE acetone-butanol-ethanol, BES bioelectrochemical system, NHE normal hydrogen electrode, N/A not available, w/o without, WE working electrode, Y yield