Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Biodiesel is a promising alternative to petroleum-based transportation fuels because it is chemically analogous to petrodiesel and can be used in compression engines and distributed using the existing infrastructure. However, its production results in large amounts of glycerol-containing wastewater, the treatment of which is an economic liability for the industry. The ‘in situ’ generation of enhanced-value co-products from crude glycerin has been identified as the most promising step to simultaneously reduce the cost of biodiesel production and generate additional revenue for the industry through product diversification. Consequently, we developed a microbial consortium for the conversion of glycerol into ethanol and electricity in bioelectrochemical systems (BESs). The ethanol can be recycled as a feedstock for the transesterification reaction and the electricity can be used to partially offset the energy needs of the biodiesel plant. The platform consists of a glycerol-fermenting bacterium, Clostridium cellobioparum, and an exoelectrogen, Geobacter sulfurreducens. C. cellobioparum ferments glycerol into ethanol and other fermentative byproducts including lactate, acetate, formate, and H2. G. sulfurreducens converts the fermentative byproducts into electricity in a BES, thereby reducing feedback inhibition and improving glycerol fermentation. Both organisms were adaptively evolved for tolerance to industrially relevant glycerol concentrations (10% w/v). Co-cultivation of the evolved strains stimulated microbial growth, ethanologenesis and the conversion of fermentative byproducts into electricity. These results highlight the potential of consortia-driven BESs for the bioprocessing of glycerin wastes.