Redox dependent metabolic shift in Clostridium autoethanogenum by extracellular electron supply

Table 1 Comparison of growth parameters, electron uptake, metabolite concentrations and yields of heterotrophic anaerobic fermentations of C. autoethanogenum in a bio-electrochemical system in the presence and the absence of three different Co-mediators

Condition	Control^a	BES^b	BES + [Co(sep)]³⁺	BES + [Co(AMMEsar)]³⁺	BES + [Co(trans-diammac)]³⁺
Growth rate (h⁻¹)	0.053 ± 0.006	0.053 ± 0.006	0.037 ± 0.006	0.033 ± 0.006	0.06 ± 0.017
OD₆₀₀ max	1.51 ± 0.18	1.11 ± 0.03	1.30 ± 0.12	1.22 ± 0.22	1.09 ± 0.14
Current max (mA)	–	0.07 ± 0.03	1.34 ± 0.24	1.07 ± 0.19	1.18 ± 0.20
e ⁻ uptake (mmol/L)	–	0.09 ± 0.01	2.77 ± 0.74	1.28 ± 0.16	2.51 ± 0.12
Final concentration (mmol/L)
Acetate	46.43 ± 5.24	42.36 ± 0.58	48.22 ± 0.21	40.9 ± 7.38	21.11 ± 0.96
Lactate	0.28 ± 0.15	0.34 ± 0.04	0.34 ± 0.09	0.31 ± 0.11	9.87 ± 0.96
Ethanol	17.63 ± 2.95	21.57 ± 0.54	13.83 ± 1.33	19.74 ± 0.61	19.04 ± 2.4
2,3-BDO	0.73 ± 0.14	0.78 ± 0.05	0.48 ± 0.17	0.68 ± 0.19	2.21 ± 1.21
Yield (g/g_fructose)
BM	7.6 ± 1.2	6.86 ± 0.38	6.3 ± 0.36	7.74 ± 1.51	6.66 ± 1.64
Acetate	54.57 ± 4.31	50.51 ± 1.08	58.9 ± 0.36	52.06 ± 8.18	24.82 ± 2.35
Lactate	0.52 ± 0.27	0.60 ± 0.05	0.56 ± 0.21	0.56 ± 0.18	18.32 ± 2.27
Ethanol	12.76 ± 2.09	19.19 ± 0.23	10.89 ± 2.02	17.71 ± 2.28	15.69 ± 0.58
2,3-BDO	1.31 ± 0.28	0.89 ± 0.04	0.69 ± 0.07	1.09 ± 0.52	4.02 ± 1.99

Fermentation time = 100 h. All experiments were performed in biological triplicates
^aControl fermentations were performed in the same reactor set up with electrodes at open circuit
^bIn BES condition the working electrode was poised at −0.603 V (vs SHE) w/o mediator

ISSN: 2731-3654