Supplied by U.S. Dept of Agriculture National Center for Agricultural Utilization Research, Peoria, Illinois BIOTECHNOLOGY LETTERS Volume 18 No.8 (August) pp.985-990 Received as revised 25 June ETHANOL PRODUCTION FROM AFEX PRETREATED CORN FIBER BY RECOMBINANT BACTERIA Mohammed Moniruzzaman l , Bruce S. Dien 2 , Betzabe FerrerI, Robert B. HespeIF, Bruce E. Dale l .\ Lonnie O. Ingram 3 , and Rodney J. Bothast 2 ' IDepartment of Chemical Engineering, Texas A&M University, College Station, TX 77843 2Fermentation Biochemistry Research Unit, USDA, ARS, NCAUR, 1815 N. University Street, Peoria, IL 61604, USA 3Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611 4Current address: Dept. of Chemical Engineering, Michigan State University, East Lansing, MI 48824, USA SUMMARY Fermentation of an enzymatic hydrolyzate of ammonia fiber explosion (AFEX) pretreated com fiber (containing a mixture of different sugars including glucose, xylose, arabinose, and galactose) by genetically-engineered Escherichia coli strain SL40 and KOll and Klebsiella oxytoca strain P2 was investigated under pH-controlled conditions. Both E. coli strains (8L40 and KO II) efficiently utilized most of the sugars contained in the hydrolyzate and produced a maximum of26.6 and 27.1 gil ethanol, respectively, equivalent to 90 and 92% of the theoretical yield. Very little difference was observed in cell growth and ethanol production between fermentations of the enzymatic hydrolyzate and mixtures of pure sugars, simulating the hydrolyzate. These results confirm the fermentability of the AFEX-treated com fiber hydrolyzate by ethanologenic E. coli. K.oxytoca strain P2, on the other hand, showed comparatively poor growth and ethanol production (maximum 20 gil) from both enzymatic hydrolyzate and simulated sugar mixtures under the same fermentation conditions. INTRODUCTION Rapid depletion of fossil fuels and increased air pollution problems provide an opportunity for expansion of renewable fuel ethanol production. Lignocellulosic materials such as agricultural and forest residues, herbaceous and woody plants, municipal solid waste, etc., are abundant and inexpensive and can serve as feedstocks for ethanol production. Com fiber also represents a renewable, lignocellulosic biomass resource that is available in sufficient quantities (l0% of the dry weight of the processed grain) from the corn wet milling industry to serve as a feedstock for ethanol fermentation. However, lignocellulose conversion to ethanol is much less developed than that of corn starch and technical constraints in the pretreatment and fermentation steps still remain. Technologies that resolve these problems can greatly improve the position of ethanol as a renewable transportation fuel. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable. 985