Optimization of a cathodic electro-fermentation process for enhancing co-production of butanol and hydrogen via acetone-butanol-ethanol fermentation of Clostridium beijerinckii

Abstract

To develop an effective acetone-butanol-ethanol (ABE) fermentation process for the enhanced co-production of butanol and H2, a series of neutral red mediated cathodic electro-fermentation (CEF) processes of Clostridium beijerinckii NCIMB 8052 were conducted with/without exogenous butyric acid as the co-substrate of glucose. The cathode potential, NR dosage, glucose concentration and exogenous butyric acid concentration were optimized progressively. The results showed that the most favorable cathode potential, NR dosage, glucose concentration and exogenous butyric acid was -0.60 V (vs Ag/AgCl), 0.50 mmol/L, 30 g/L and 3.00 g/L, respectively. With the optimal condition, the metabolism in the CEF process of C. beijerinckii NCIMB 8052 was well manipulated, resulting the excellent production of butanol and H2 as high as 10.85 ± 0.45 g/L and 4.33 ± 0.40 L/L-medium, respectively. The excellent butanol yield of 0.40 ± 0.00 g/g-glucose (0.60 ± 0.01 mol-C/mol-C) and H2 yield of 161.69 ± 19.28 mL/g-glucose resulted an energy recovery (ER) and energy recovery efficiency (ERE) as high as 446.90 ± 21.39 kJ/L-medium and 95.85 ± 1.62%, respectively. The optimized CEF process demonstrates an effective approach to manipulating the microbial metabolism of Clostridia for the enhanced co-production of butanol and H2.