ARS | Publication request: DEVELOPMENT OF MICROBIAL BIOCATALYSTS TO PRODUCE FUELS FROM AGRICULTURAL BIOMASS

Submitted to: United States Japan Natural Resources Protein Panel
Publication Type: Proceedings
Publication Acceptance Date: November 15, 2003
Publication Date: November 15, 2003
Citation: Cotta, M.A., Nichols, N.N., Dien, B.S., Li, X. 2003. Development of microbial biocatalysts to produce fuels from agricultural biomass. Proceedings 32nd annual United States Japan Natural Resources Protein Panel. p. 387-393.

Technical Abstract: Use of agricultural biomass, other than cornstarch, to produce fuel ethanol requires a microorganism that can ferment the mixture of sugars derived from hemicellulose. E. coli metabolizes a wide range of substrates and has been engineered to produce ethanol in high yield from sugar mixtures. E. coli metabolizes glucose in preference to other sugars, and as a result, utilization of the pentoses in hemicellulose-derived sugar mixtures is delayed and may be incomplete. Residual sugar lowers the ethanol yield and is problematic for downstream processing of fermentation products. Therefore, a catabolite repression mutant that simultaneously utilizes glucose and pentoses would be useful for fermentation of complex substrate mixtures. We constructed ethanologenic E. coli strains with a glucose phosphotransferase (ptsG) mutation and used the mutants to ferment glucose, arabinose, and xylose, singly and in mixtures, to ethanol. Yields were 87-94% of theoretical for both the wild-type and mutants, but the mutants had an altered pattern of mixed sugar utilization. ptsG mutants metabolized the pentoses simultaneously with glucose, rather than sequentially. Based upon fermentations of sugar mixtures, a catabolite repression mutant of ethanologenic E. coli is expected to provide more efficient fermentation of hemicellulose hydrolysates by allowing direct utilization of pentoses.