Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 13, 2009
Publication Date: August 10, 2009
Citation: Dickey, L.C., Kurantz, M.J., Parris, N., Mcaloon, A.J., Moreau, R.A. 2009. Oil separation from foam fractions of enzymatically treated wet milled corn germ dispersions. Journal of the American Oil Chemists' Society. 86:927-932. Interpretive Summary: Dry grind production of ethanol from corn creates a byproduct, distillers’ dried grains, DDG. In the US, DDG contains roughly 300 million gallons of corn oil that can be converted into a similar volume of biodiesel. The embryo of the corn, also called the germ, contains > 90% of the oil in the kernel and can be separated prior to fermentation by several new processes. Corn oil can then be separated from the germ and made available for uses other than animal feed, keeping the vegetable oil price stable despite increased consumption for biodiesel production. Sale of germ as a byproduct, in place of some of the DDG, should significantly increase the overall ethanol production revenues and thereby benefit this industry. More dry-grind ethanol production will bolster the U.S. corn market, reduce petroleum imports and slow depletion of world petroleum reserves. Corn germ price and its impact on dry grind profitability will increase if the cost of separating the oil from the germ can be reduced. Using an aqueous method, instead of hexane extraction, is one approach to cheaper oil separation. Enzyme cost was a large fraction of the cost of removing oil from an aqueous mixture; this work shows it has been reduced by a factor of at least 70.
Technical Abstract: The many recent dry grind plants that convert corn to ethanol are potential sources of substantial amounts of corn oil, if an economical method of separating it can be developed. Oil was separated from corn germ by aqueous enzymatic extraction (AEE). Batches of wet- milled corn germ in water were preheated in a pressure cooker, ground in a colloid mill, then mixed with enzymes and churned in a vertical column/mixing vessel system. Nitrogen gas was then bubbled through the column removing an overflowing foam fraction which was subsequently centrifuged to separate a free oil fraction. Using a newly commercialized enzyme solution it was found that a relatively small amount was needed to recover 80% of the oil. The low dose and low price of the enzyme indicate that the estimated enzyme cost to separate corn oil from germ, similar to the wet-milled germ extracted, makes AEE competitive with expelling, and feasible for commercialization in a dry grind plant retrofitted to separate germ.