title: Bioelectrochemical ethanol production through mediated acetate reduction by mixed cultures.
abstract: Biological acetate reduction with hydrogen is a potential method to convert wet biomass waste into ethanol. Since the ethanol concentration and reaction rates are low, this research studies the feasibility of using an electrode, in stead of hydrogen, as an electron donor for biological acetate reduction in conjunction of an electron mediator. Initially, the effect of three selected mediators on metabolic flows during acetate reduction with hydrogen was explored; subsequently, the best performing mediator was used in a bioelectrochemical system to stimulate acetate reduction at the cathode with mixed cultures at an applied cathode potential of -550 mV. In the batch test, methyl viologen (MV) was found to accelerate ethanol production 6-fold and increased ethanol concentration 2-fold to 13.5 +/- 0.7 mM compared to the control. Additionally, MV inhibited n-butyrate and methane formation, resulting in high ethanol production efficiency (74.6 +/- 6%). In the bioelectrochemical system, MV addition to an inoculated cathode led directly to ethanol production (1.82 mM). Hydrogen was coproduced at the cathode (0.0035 Nm(3) hydrogen m(-2) d(-1)), so it remained unclear whether acetate was reduced to ethanol by electrons supplied by the mediator or by hydrogen. As MV reacted irreversibly at the cathode, ethanol production stopped after 5 days.
authors: Sub-department of Environmental Technology, Wageningen University, Bomenweg 2, 6708 HD Wageningen, The Netherlands.
authors: Kirsten J J
authors: KJ
authors: Steinbusch
authors: Hubertus V M
authors: HV
authors: Hamelers
authors: Joris D
authors: JD
authors: Schaap
authors: Christel
authors: C
authors: Kampman
authors: Cees J N
authors: CJ
authors: Buisman
mesh_terms: D000085:Acetates / Q000378:metabolism*; D004563:Electrochemistry; D000431:Ethanol / Q000378:metabolism*; D010084:Oxidation-Reduction
chemical_list: D000085:Acetates; D000431:Ethanol