Anaerobic fermentation of glycerol by Escherichia coli K12 for the production of ethanol

As a by-product of biodiesel production, glycerol has now become an abundant and cheap source of carbon. Conversion of this glycerol to higher value products will increase the economic viability of the biodiesel production process.;The study also investigated hydrogen and ethanol production from glucose, glycerol and crude glycerol via fermentation using Escherichia coli. The optimal conditions for fermentation of crude glycerol differ from that of pure with respect to initial glycerol concentration, supplementation and mixing speed. The maximum ethanol yield for crude glycerol was 85% of the maximum yield of ethanol of 0.42 g/g obtained at the optimum conditions of pure glycerol fermentation.;A full factorial experimental design was used to test the effects of glycerol concentration and headspace conditions on the cell growth, ethanol and hydrogen production were investigated. The results demonstrate that increase of glycerol concentration accelerates fermentation and that hydrogen production negatively affects cell growth. Maximum ethanol yield was obtained with a glycerol concentration of 10 g/L and was 0.38 g/g glycerol under membrane condition headspace. Statistical optimization showed that optimal conditions are 20 g/L initial glycerol with initial sparging of the reactor headspace for hydrogen production and 10 g/L initial glycerol with a membrane for ethanol.