1-09: Anaerobic conversion of glycerol to ethanol by Paenibacillus macerans

Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Matthew S. Wong1, Ryan W. Black1, Thao Q. Le1, Paul Campbell2 and Daniel J. Monticello2, (1)Fermentation Process Development, Glycos Biotechnologies, Inc, Houston, TX, (2)Research and Development, Glycos Biotechnologies, Inc, Houston, TX
Glycerol has become a desirable feedstock for the production of fuels and chemicals due to its availability and low price.  The anaerobic fermentation of glycerol to ethanol by Escherichia coli requires expensive refined nutrients due to its inability to use unhydrolyzed protein.  We have developed an ethanol fermentation based on the use of a non-Genetically Modified Organism (non-GMO): an isolate of  Paenibacillus macerans.  This isolate secretes proteases into the medium, which allows the use of cheaper, less processed sources of nutrients.  We used Plackett-Burman experiments to determine the optimal temperature (42°C), pH (6.0), and starting concentration of glycerol (60 g/L) for P. macerans.  Medium optimization experiments determined that the best medium contained soybean flour (36.8 g/L) and yeast extract (6 g/L).  Wild-type P. macerans undergoes sporulation as the culture approaches stationary phase, which limits the ethanol titer.  We used traditional mutagenesis and screening methods to isolate a non-sporulating mutant.  Further experiments determined the most economical commercial source of yeast extract (Hy-Yest 413 from Sheffield Biosciences).  Currently, the process reaches a titer of 33 g/L ethanol in 72 h.  We are continuing to work to improve the process productivity and economics.
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