Comparison of Glucose, Glycerol and Crude Glycerol Fermentation by Escherichia Coli K12

Hydrogen and ethanol production from glucose, glycerol and crude glycerol fermentation using Escherichia coli was investigated. Crude glycerol used in this study contained 80% glycerol, 2.6% ash, 12.3% moisture, 1.7% free fatty acid, 3.4% MONG (matter organic non-glycerol), 2519 mg/kg sulphur and 9000 ppm sodium. The maximum yield of ethanol from crude glycerol of 0.36 g/g, corresponding to an ethanol concentration of 3.6 g/L was obtained at 10 g/L initial glycerol concentration, 5 g/L tryptone concentration and 100 rpm mixing speed. Comparable yields were obtained at the mixing speeds of 150 and 200 rpm. On comparison, this yield corresponded to 105% of the yield (0.34 g/g) obtained from pure glycerol at the same conditions and 85% of the maximum yield (0.42 g/g) of ethanol obtained from pure glycerol at 10 g/L initial glycerol concentration, 10 g/L tryptoneconcentration and 200 rpm mixing speed. Additionally, Escherichia coli growth for glycerol was characterized and compared to that for glucose with 10 % substrate concentration at 37°C and 200 rpm mixing speed. The net growth rate for glucose and glycerol were 0.43 and 0.26 h-1, respectively. The maximum dry weight attained for glucose and glycerol were 0.12 and 0.04 g/L, respectively.