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Title: FERMENTABILITY OF CONCENTRATED CORE FIBER HYDROLYSATES FOR ETHANOL PRODUCTION

Author
item O Brien, Dennis
item Senske, Gerard

Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2003
Publication Date: 1/15/2004
Citation: Bioresource Technology 92 (2004). pp. 15-19

Interpretive Summary: While most ethanol produced today comes from corn, increasing demand for fuel ethanol has prompted research into new biomass feedstocks. A source of biomass derived from corn is corn fiber, the bran component of the corn kernel. If corn fiber could be efficiently hydrolyzed to simple sugars and fermented to ethanol, the economics of ethanol from corn could be significantly improved. In this study, corn fiber hydrolysate was concentrated by reverse osmosis, a membrane-based process, to increase the low levels of sugars in the hydrolysate. The ability of these concentrated hydrolysates to be successfully fermented was assessed. This type of information is essential to the design of fermentation processes utilizing biomass feedstocks. Successful research would lead to increased ethanol yield from corn, benefitting both farmers and ethanol producers.

Technical Abstract: Utilization of lignocellulosic feedstocks for ethanol production in the U.S. will require processes incorporating efficient physicochemical and biological conversion operations. Dilute acid hydrolysis of hemicellulose-rich biomass often produce hydrolysates of low or moderate sugar levels which when fermented result in low ethanol broth concentrations. Dilute acid hydrolysates of corn fiber were concentrated twofold in a plate-and-frame reverse osmosis unit with no loss of sugar in order to determine the fermentability of hydrolysates containing high sugar levels. Fermentation of hydrolysates containing 140-191 g/L total sugars by Escherichia coli KO 11 resulted in incomplete sugar utilization and decreasing ethanol yields at higher concentrations. Analysis of the role of inhibitors acetic acid, furfural, and hydroxymethyl furfural indicated that while acetate likely has a minor impact on fermentability, the major limitation in the utilization of concentrated hydrolysates to achieve high ethanol broth concentrations is the inherent ability of the fermenting organism.