Ethanol Production form Biodiesel-derived Crude Glycerol by Enterobacter Aerogenes

Glycerol is an inevitable byproduct of biodiesel production that has become an attractive carbon source for fermentation processes due to its availability, low price and high degree of reduction. This study demonstrated the potential of utilising the glycerol surplus through conversion to ethanol. In this work, glycerol was used as a feedstock for ethanol batch fermentation process by Enterobacter aerogenes, under pH 7.0 and 30 degrees C. E aerogenes favored oxidative- over reductive pathways and yielded the ethanol as a main fermentative product. The profiles of glycerol utilization rate, ethanol production rate, and specific growth with respect to the glycerol concentration and the ethanol production were similar for both types of the glycerol. Substrate inhibitory effect was found at 40 g L-1 initial glycerol concentration. Impurities in the crude glycerol posed no negative impact to E aerogenes, and apparently raised the ethanol concentration and yield by 32 and 21% compared those with the pure glycerol fermentation at the optimum glycerol concentration. The highest ethanol production was 204 mM on 25 g L-1 crude glycerol. The current findings showed the potential application of E aerogenes in a large scale ethanol production from the crude glycerol.