Microbial production of hydrogen and ethanol from glycerol‐containing wastes discharged from a biodiesel fuel production plant in a bioelectrochemical reactor with thionine

Abstract

H(2) and ethanol production from glycerol-containing wastes discharged from a biodiesel fuel production plant by Enterobacter aerogenes NBRC 12010 was demonstrated in bioelectrochemical cells. Thionine as an exogenous electron transfer mediator was reduced by E. aerogenes, and was re-oxidized by a working electrode applied at +0.2 V against a Ag/AgCl reference electrode by a potentiostat (electrode system). At the initial glycerol concentration of 110 mM, 92.9 mM glycerol was consumed in the electrode system with 2 mM thionine after 48 h. On the other hand, the concentration of glycerol consumed was only 50.3 mM under the control conditions without thionine and the electrodes (normal fermentation). There are no differences in the yields of H(2) and ethanol against glycerol consumed between the control conditions and the conditions with the electrode system. A pH of 6.0 was suitable for the H(2) production in the range between pH 6 and pH 7.5 in the electrode system. At pH values of 7.0 and 7.5, H(2) production decreased and formate was remarkably produced in the reaction solution. The rates of both glycerol consumption and the H(2) and ethanol production increased as the thionine concentration and the surface area of the working electrode increased. After 60 h, 154 mM of the initial 161 mM glycerol concentration in the wastes was consumed in the electrode system, which is a 2.6-fold increase compared to the control experiment. Biotechnol. Bioeng. 2007;98: 340-348. (c) 2007 Wiley Periodicals, Inc.

Understanding and harnessing the microaerobic metabolism of glycerol in Escherichia coli

“…performance of these engineered strains was superior to that reported for the conversion of glycerol to ethanol and hydrogen or ethanol and formate by other microorganisms (Ito et al, 2005;Jarvis et al, 1997;Sakai and Yagishita, 2007) and similar to that achieved with E. coli strains engineered to convert cellulosic sugars to ethanol (Underwood et al, 2002). In addition to producing ethanol, strain EF06 [pZSKLMgldA] produces formate, which implies an overall yield and rate of product synthesis almost twice of that reported for the production of ethanol from sugars.…”

Improved Utilization of Crude Glycerol By-Product from Biodiesel Production

“…In this case, hydrogen production rate was 63 mmol/L/h with ethanol yield of 0.85 mol/mol. In turn, Sakai & Yagishita (2007) reported crude glycerol bioconversion to hydrogen and ethanol by bioelectrochemical cells of wild type of Enterobacter aerogenes NBCR 12010 using thionine as an exogenous electron transfer mediator. On the basis of conducted experiments, one can say that the yield of hydrogen as well as ethanol reached more than 80%.…”

Glycerol fermentation by (open) mixed cultures: A chemostat study

“…For this purpose, strains unable to produce 1,3-propanediol are preferred in order to decrease the sideproduct formation. Examples of such strains are E. coli and Enterobacter aerogenes (Dharmadi et al, 2006;Homann et al, 1990;Sakai and Yagishita, 2007).…”