Modification of aqueous enzymatic oil extraction to increase the yield of corn oil from dry fractionated corn germ

Authors: Dickey, Leland; Johnston, David; Kurantz, Michael; McAloon, Andrew; Moreau, Robert

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2011
Publication Date: 3/25/2011
Citation: Dickey, L.C., Johnston, D., Kurantz, M.J., Mcaloon, A.J., Moreau, R.A. 2011. Modification of aqueous enzymatic oil extraction to increase the yield of corn oil from dry fractionated corn germ. Industrial Crops and Products. 34:845-850.

Interpretive Summary: Dry grind production of ethanol from corn creates a byproduct, distillers’ dried grains, DDG. In the US, DDG contains roughly 480 million gallons of corn oil that could be recovered prior to fermentation. The embryo of the corn, also called germ, contains > 90% of the oil in the kernel and can be separated by several new processes 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 separating the oil from the germ can be shown to be feasible. Using an aqueous enzymatic method, instead of hexane extraction, is an approach to cheaper oil separation. Aqueous extraction was previously shown to be economically attractive starting with wet-mill germ and marginal with dry-fractionated germ. This work describes an improvement to aqueous enzymatic extraction of dry-fractionated germ by incorporating amylase (starch digesting) and protease (protein digesting) enzymes to the process. This modification increased the amount of oil that could be extracted from the germ by another 26%. It is estimated that the value of the additional oil produced would be more than the cost of the enzymes and therefore could be an economical way to utilize the process. This information will be of value to the owners of the 150+ ethanol plants in the US who are investigating ways to recover high valued corn oil from their ethanol plants.

Technical Abstract: In previous aqueous enzymatic extraction experiments we reported an oil yield of 67 grams from 800 grams of dry fractionated corn germ. In the current experiments, a dispersion of 10% cooked, dry-fractionated germ in water and was treated with amylases and a cellulase complex. A foam fraction was separated from the dispersion and collected. The foam contained up to 6% free oil (separable by centrifugation) and fines oil (not centrifugally separable), protein and germ particles. Addition of amylase and glucoamylase to the commercial cellulase used in the aqueous enzymatic process increase oil yields by about 26%.