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United States Department of Agriculture

Agricultural Research Service

Research Project: AQUEOUS ENZYMATIC EXTRACTION OF CORN OIL AND VALUE-ADDED PRODUCTS FROM CORN GERM PRODUCED IN NEW GENERATION DRY-GRIND ETHANOL PROCESSES
2007 Annual Report


1a.Objectives (from AD-416)
Develop new environmentally safe aqueous/enzymatic processes to extract the edible oil from corn germ (obtained from new-generation dry-grind corn-to-ethanol plants) and develop processes to fractionate the de-oiled germ into value-added protein and carbohydrate coproducts, to improve the overall economics of making fuel ethanol in new-generation plants.


1b.Approach (from AD-416)
Corn germ from several new generation processes will be treated with mechanical (various forms of milling, homogenization and pressing), chemical (e.g. pH adjustment) and various enzymatic treatments, with the goal of causing the oil to coalesce and float upon centrifugation or other means of separation.


3.Progress Report
a. Development of a Column for Corn Oil Separation after Aqueous Enzymatic Extraction - An acrylic churning column/heat bath/stirred pot system was developed and used to show that oil could be collected with a foam overflow. This suggests that a considerable reduction in expensive centrifuge use will be achieved with this system compared to centrifugation of the entire germ dispersion (as was done on laboratory scale extractions). A computer model (SuperPro) for the aqueous extraction has been prepared to calculate the cost benefit of reducing centrifugation by prior concentration of oil, and possibly protein, in the foam from the bubble column churning system. Experimentation with the new column system will supply yields to refine the flow sheet. This research supports the ARS National Program 307, Bioenergy and Energy Alternatives, Component 1, Ethanol Coproduct Development.

b. Research was conducted under a CRADA (58-3K95-5-1087) between ARS and the Illinois Corn Marketing Board which was initiated on 01/01/05 and will terminate on 12/31/07.

This report serves to document research conducted under a CRADA (58-3K95-5-1087) between ARS and the Illinois Corn Marketing Board which was initiated on 01/01/05 and will terminate on 12/31/07. Additional details of this research can be found in the report for the subordinate project 1935-41000-069-01T. During the last year researchers at ERRC continued to compare the composition of conventional corn oil (corn oil obtained by pressing and/or hexane extraction of corn germ) versus corn oil obtained by extracting ground corn with ethanol. The analyses focused on comparing the levels of xanthophylls (lutein and zeaxanthin) in the two oils. The results indicated that the levels of each of these functional lipids were about one-hundred-fold higher in the corn oil from ethanol-extracted ground corn than in conventional corn oil.

During the year three meetings were held and numerous telephone and e-mail messages were exchanged to monitor progress of the collaboration. On September 12, 2006 and February 27, 2007, the ARS cooperator traveled to Illinois to visit with the CRADA partner to discuss CRADA research progress. On July 29-31, 2007, the ARS cooperator traveled with the CRADA partner to the International Food Technology Annual Meeting in Chicago, IL, to meet with prospective companies to discuss technology transfer options.


4.Accomplishments
a. Development of an Aqueous Enzymatic Oil Extraction Process for Corn Germ from a Commercial Corn Dry Mill - Dry milled corn germ is a coproduct of dry milling, a commercial process designed to remove the oil-rich germ from food-grade corn products to increase their shelf live by diminishing their susceptibility to oil rancidity and oxidation. Previously we have reported that oil yields of about 50% could be achieved by aqueous enzymatic extraction of oil from dry milled corn germ. The previous process required heat pretreatment of the germ and the use of a cellulase (a cellulose-degrading enzymes). During the last year we have identified a protease (a protein-degrading enzyme) which, when used in combination with cellulase, allows us to achieve oil yields of 80-90% from dry milled corn germ, without the need for heat pretreatment of the germ. This new aqueous enzymatic oil extraction process provides a new more effective way to obtain corn oil from dry milled corn germ without the use of hexane or other hazardous solvents. This research supports the ARS National Program 307, Bioenergy and Energy Alternatives, Component 1, Ethanol Coproduct Development. Goal "To develop higher-valued new coproducts or improve the existing ones from the non-starch portion of the grain, resulting in a reduced net cost of the starch used for producing ethanol."

b. Development of an Aqueous Enzymatic Oil Extraction Process for Corn Germ from New Generation Ethanol Plants – Several strategies have been developed to remove the oil-rich corn "germ" from corn kernels before their fermentation to fuel ethanol. Some of these processes are "dry," where the germ is physically removed from the unwetted germ, and some processes are "wet," where the kernel is soaked or steeped before germ separation. The corn germ can then be extracted to obtain a valuable coproduct, corn oil (~$0.30/lb). During the last year we identified an appropriate combination of commercial enzymes (a combination of a cellulase and a protease) and developed a process which allowed us to achieve oil yields of 80-90% from several samples of "new generation" corn germ. This new aqueous enzymatic oil extraction process may provide a way for ethanol plants to be able to produce a new valuable coproduct on-site, without the use of hexane or other hazardous solvents. This research supports the ARS National Program 307, Bioenergy and Energy Alternatives, Component 1, Ethanol Coproduct Development. Goal "To develop higher-valued new coproducts or improve the existing ones from the non-starch portion of the grain, resulting in a reduced net cost of the starch used for producing ethanol."

c. Ethanol Extracted Corn Kernel Oil is a Rich Source of Health-Promoting Nutraceuticals Lutein and Zeaxanthin - All commercial corn oil is obtained by pressing corn germ and/or extracting the germ with hexane. During the last year we developed a process to extract a unique type of corn oil by extracting ground corn with 100% ethanol. The levels of lutein + zeaxanthin in this "ethanol-extracted corn kernel oil" were about 220 µg/g, which is about 100 times higher than the concentration in commercial corn oil (from corn germ). This new type of corn oil contains about 3 mg of lutein + zeaxanthin per tablespoon of corn oil, so consumption of 2 tablespoons per day would supply the amount (~6 mg) that that most experts currently believe is required to slow the progression of age-related macular degeneration. If such an oil was commercially available, all consumers, and especially the aged, could greatly benefit from its composition. Because we have demonstrated that this new type of corn oil contains high levels of these valuable phytonutrients, we anticipate that it will sell for a higher price than commodity corn oil, thus returning more coproduct value to the producer. This research supports the ARS National Program 307, Bioenergy and Energy Alternatives, Component 1, Ethanol Coproduct Development. Goal "To develop higher-valued new coproducts or improve the existing ones from the non-starch portion of the grain, resulting in a reduced net cost of the starch used for producing ethanol."


5.Significant Activities that Support Special Target Populations
None


6.Technology Transfer

Number of active CRADAs and MTAs1
Number of U.S. patents granted1
Number of non-peer reviewed presentations and proceedings2
Number of newspaper articles and other presentations for non-science audiences1

Review Publications
Moreau, R.A. 2006. The quantitative analysis of lipids via hplc with a charged aerosol detector. Lipids Journal V.41, No. 7., p.727-734.

Moreau, R.A., Hicks, K.B. 2006. A reinvestigation of the effect of heat pretreatment of corn fiber and corn germ on the levels of extractable tocopherols and tocotrienols. Journal of Agriculture and Food Chemistry. 54, p.8093-8102.

Nystrom, L., Achrenius, T., Lampi, A., Moreau, R.A., Piironen, V. 2007. A comparison of the antioxidant properties of steryl ferulates with tocopherol at high temperatures. Food Chemistry 101, p.947-954.

Choi, S., Lee, S., Kim, E., Yoon, K., Parris, N., Hicks, K.B., Moreau, R.A. 2007. Antioxidant and Antimelanogenic activities of polyamine conjugates from corn bran and related hydroxycinnamic acids. Journal of Agriculture and Food Chemistry 55, p.3920-3925.

Dickey, L.C., Cooke, P.H., Kurantz, M.J., Mcaloon, A.J., Parris, N., Moreau, R.A. 2007. Using microwave heating to determine optimal corn germ oil yield with a bench-scale press. 2007. Journal of the American Oil Chemists' Society 84(5):489-495.

Last Modified: 4/17/2014
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