Submitted to: Applied Biochemistry and Biotechnology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/23/2004
Publication Date: 2/1/2005
Citation: Mosier, N.S., Hendrickson, R., Brewer, M., Ho, N., Sedlak, M., Dreshel, R., Welch, G., Dien, B.S., Aden, A., Ladisch, M.R. 2005. Industrial scale-up of ph-controlled liquid hot water pretreatment of corn fiber for fuel ethanol production. Applied Biochemistry and Biotechnology. 125:77-97. Interpretive Summary: Increased production of corn ethanol has led to an over-supply of the low protein animal feed products produced as a co-product. The primary component of this feed is corn fiber. We, in collaboration with Purdue University, have estimated that yields from a bushel of corn could be increased as much as 10% if this fiber was diverted into ethanol production. Purdue University has since developed and patented a 'pretreatment' process for freeing sugars from corn fiber, thereby, making these available for fermentation. This paper describes an exciting collaboration among an industrial corn wet miller, Purdue University, Agricultural Research Service (ARS), and Department of Energy scientists to build and operate a demonstration process for pretreating 43 gallons per minute of corn fiber slurry at an ethanol facility. The results demonstrated the feasibility of this process, and subsequent studies by ARS and Purdue showed the resulting sugars were readily fermented to ethanol. Furthermore, modeling by Purdue University suggests the process could produce additional ethanol, albeit from the freed starch fraction, for only $0.84/gallon.
Technical Abstract: The pretreatment of cellulose in corn fiber by liquid hot water at 160 deg C and a pH above 4.0 dissolves 50% of the fiber in 20 min. The preatment also enables the subsequent complete enzymatic hydrolysis of the remaining polysaccharides to monosaccharides. The carbohydrates dissolved by the pretreatment are 80% soluble oligosaccharides and 25% monosaccharides. Only a minimal amount of protein is dissolved, thus enriching the protein content of the undissolved material. Replication of laboratory results in an industrial trial at 43 gpm (163 L/min) of fiber slurry with a residence time of 20 min illustrates the utility and practicality of this approach for pretreating corn fiber. The added costs due to pretreatment, fiber, and hydrolysis are equivalent to less than $0.84/gallon of ethanol produced from the fiber. Minimizing monosaccharide formation during pretreatment minimizes the formation of degradation products; hence the resulting sugars are readily fermentable to ethanol by the recombinant hexose and by pentose fermenting yeast (426A(LNH-ST)) and ethanologenic Escherichia coli. This cooperative effort and first successful trial opens the door for examining the robustness of the pretreatment system under extended run conditions as well as pretreatment of other cellulose containing materials using water at controlled pH.