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United States Department of Agriculture

Agricultural Research Service

Title: Fermentations with New Recombinant Organisms

Authors
item Bothast, Rodney
item Nichols, Nancy
item Dien, Bruce

Submitted to: Biotechnology Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 5, 1999
Publication Date: N/A

Interpretive Summary: United States fuel ethanol production in 1998 exceeded the record production of 1.4 billion gallons set in 1995. Most of this ethanol was produced from over 550 million bushels of corn. Expanding fuel ethanol production will require developing lower cost feedstocks, and only biomass feedstocks are available in sufficient quantities to substitute for corn starch. A major technical hurdle to converting biomass to ethanol is developing an appropriate microorganism for the fermentation of mixed sugars. The most successful research approaches to develop novel biocatalysts that will efficiently ferment mixed sugar syrups include genetic engineering of bacteria and yeasts. We evaluated the fermentation of corn fiber hydrolyzates by various genetically engineered strains available to us. Each strain produced good ethanol yield. Progress with new recombinant microorganisms will continue with the eventual development of organisms suitable for commercial ethanol production.

Technical Abstract: United States fuel ethanol production in 1998 exceeded the record production of 1.4 billion gallons set in 1995. Most of this ethanol was produced from over 550 million bushels of corn. Expanding fuel ethanol production will require developing lower cost feedstocks, and only lignocellulosic feedstocks are available in sufficient quantities to substitute for corn starch. A major technical hurdle to converting lignocellulose to ethanol is developing an appropriate microorganism for the fermentation of mixed sugars. The most successful research approaches to develop novel biocatalysts that will efficiently ferment mixed sugar syrups include isolation of novel yeasts that ferment xylose, genetic engineering of Escherichia coli and other gram negative hosts for ethanol production, and genetic engineering of Saccharomyces cerevisiae and Zymomonas mobilis for pentose utilization. We objectively evaluated the fermentation of corn fiber hydrolyzates by the strains made available to us. E. coli K011, E. coli SL40, FBR3, Zymomonas CP4(pZB5), and Saccharomyces 1400 (pLNH32) fermented corn fiber hydrolyzates to ethanol in the range of 21-34 g/liter with yields ranging from .41 to .50 g ethanol per g sugar consumed. Each research approach holds considerable promise, with the possibility existing that mature strains of each recombinant may be suitable for commercial ethanol production.

Last Modified: 9/23/2014
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