CONVERSION OF LIGNOCELLULOSE TO ETHANOL USING A RECOMBINANT E. COLI STRAIN

Authors: Dien, Bruce; Iten, Loren; Nichols, Nancy; Cotta, Michael

Submitted to: Society of Industrial Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 8/14/2003
Publication Date: 8/14/2003
Citation: Dien, B.S., Iten, L.B., Nichols, N.N., Cotta, M.A. 2003. Conversion of lignocellulose to ethanol using a recombinant E. coli strain [abstract]. Society of Industrial Microbiology. p. 102.

Interpretive Summary:

Technical Abstract: Production of fuel ethanol from lignocellulose has the potential to meet 10% or more of our transportation fuel needs. However, most sources of lignocellulose contain significant amounts of xylan, up to 33%, which necessitates using microorganisms that ferment pentose sugars. Recombinant Escherichia coli strains, engineered to selectively produce ethanol, metabolize a wide spectrum of sugars, including pentoses. However, they normally ferment sugars to a mixture of organic acids and ethanol. We have developed a series of E. coli strains that selectively produce ethanol by complementing non-fermentative mutants (pfl-, ldh-) with plasmid pLOI297 (Lonnie Ingram, Univ. of FL). Plasmid pLOI297 encodes the adh and pdc genes from Zymomonas mobilis, expression of which allows for the conversion of pyruvate to ethanol. The strains not only selectively produce ethanol because competing fates for pyruvate have been eliminated, but also stably maintain the plasmid in the absence of antibiotics. We have used the best of these strains (FBR5) to ferment a variety of hydrolysates prepared from lignocellulose. The fermentations are usually completed in less than 60 hr, and ethanol yields are over 90% of theoretical. However, the fermentations used an expensive rich medium formulation. Current work on developing a less costly, industrially realistic medium formulation will be described.