Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Preparing compound containing saccharide radical
Reexamination Certificate
2000-02-10
2002-03-05
Prats, Francisco (Department: 1651)
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Preparing compound containing saccharide radical
C435S072000, C435S099000, C435S274000
Reexamination Certificate
active
06352845
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to corn fiber. More particularly, the present invention pertains to methods of extracting monosaccharides from corn fiber. In a further aspect, the invention pertains to methods of separating the monosaccharides obtained from corn fiber wherein the monosaccharides are obtained according to the methods herein.
BACKGROUND OF THE INVENTION
In the future, it will become increasingly important to develop consumer products from renewable resources, especially from annually renewable resources. Corn is one example of an annually renewable resource that serves as a source of valuable consumer products. Products derived from corn serve an important role in providing useful foodstuffs to the public. Corn provides important products, such as high fructose corn syrup, ethanol, grain and corn oil. While a large percentage of the total portion of corn is utilized to manufacture these substances, as well as other high value products, a significant fraction of corn is utilized for relatively low value products, such as animal feed. Technology that would allow a higher value utilization of the remaining fractions of corn would provide increased value overall from the entire useable portions of corn.
Corn fiber is one under-utilized fraction of corn. Corn fiber is obtained as a major by-product of the milling of corn. Corn fiber comprises the outer hull portion of the corn kernel. It has been estimated that approximately 7 to 10 billion pounds of corn fiber are produced annually in the United States. The fiber is produced at milling facilities and is collected as a relatively homogeneous fraction.
A major source of corn fiber is the wet milling of corn. During this process, the higher value products are removed from corn, such as the germ of the kernel. After extraction of the high value products, the remainder, which generally constitutes corn fiber, is mixed with steep liquor, also a by-product of corn milling. The mixture of fiber and liquor is then normally dried, pelletized and sold as gluten.
Another source of corn fiber is dry milling; corn fiber obtained from dry milling is often referred to as “corn bran.” The bran by-product of dry milled corn fiber, composed primarily of hull, is mixed with other corn by-products and sold as hominy.
Both gluten feed and hominy feed are fairly low-value products. Nonetheless, these products have generally been the only commercial products prepared from corn fiber. Given the low margins of such products made from corn fiber, it is not uncommon for corn fiber to be disposed of outright, instead of undertaking the effort to prepare such low-value products.
Corn fiber makes up a significant (5 to 10 wt. %) portion of the total weight of the corn kernel. Corn fiber itself is made up of a number of components most of which, if extracted, can be commercially valuable. Specifically, corn fiber consists primarily of residual starch (10 to 25 wt. %), hemicellulose (40 to 50 wt. %), cellulose (15 to 25 wt. %), phenolic acids (3 to 5%), with the remainder present as proteins and oils. (See Wolf, et al. Cereal Chemistry, 30(1953), pp. 195-203; Chanliaud, et al., J. Cereal Science, 21(1995), pp. 195-203.) The variations in the reported composition are believed to be due to corn plant variety and growth conditions, as well as the specific methods utilized to isolate the corn fiber.
Hemicellulose is a component of corn fiber that has been of interest commercially. A number of references disclose the extraction of hemicellulose from corn fiber. However, most previous attempts to obtain useful products from corn fiber have focused almost entirely on methods to extract hemicellulose from corn fiber and the properties, particularly the color, of the hemicellulose obtained. These attempts to extract hemicellulose were likely initiated by the fact that hemicellulose has several valuable properties that make it attractive for a number of applications. In a non-exclusive list, some uses for hemicellulose include non-toxic adhesives, thickeners, emulsifiers, stabilizers, film formers and paper additives. (See e.g., Whistler, Industrial Gums, 3d Ed., Academic Press, 1993, pp. 295-308; U.S. Pat. No. 2,772,981; Wolf, et al. Cereal Chemistry, 30(1953), pp. 451-470.)
As indicated by these, as well as other references, hemicellulose can be quite difficult to extract from corn fiber. Because corn fiber hemicellulose is soluble in H
2
O, it would be expected that hemicellulose would be fairly easy to extract from corn fiber utilizing water or some other non-aggressive solvent. This is not the case, however. Hydrogen bonding and physical entanglement of the hemicellulose with the corn fiber matrix are believed to be in part responsible for the difficulty in extraction. Other reasons for the difficulty in extractability may be due to cross-linking of the hemicellulose to other components of the corn fiber cell wall via covalent bonds between esterified phenolic acid residues and arabinose residues. Protein-polysaccharide linkages may also affect the ability to extract hemicellulose from corn fiber.
Most previous attempts to extract hemicellulose from corn fiber have focused on the use of strongly alkaline materials. This is not surprising, as one definition of hemicellulose is the portion of plants that is extractable by hot alkali treatment.
Various references disclose techniques to extract hemicellulose. For example, U.S. Pat. No. 2,709,699 discloses extraction of corn fiber with aqueous alkali at a pH of from 9 to 13 at from 90 to 115° C. for a time sufficient to solubilize hemicellulose so that it can be extracted. In this reference, the hemicellulose was isolated by adjusting the solution pH with an inorganic acid, followed by precipitation of the hemicellulose in ethanol, filtering to remove the hemicellulose and drying.
In another reference disclosing the extraction of hemicellulose from corn fiber, U.S. Pat. No. 4,038,481, corn fiber is treated with alkali to solubilize the hemicellulose. The hemicellulose is then precipitated with a water miscible organic solvent. The solvents utilized are acetone, methanol, ethanol, propanol, isopropanol, isobutyl alcohol, tert-butyl alcohol, or a mixture thereof. There is no disclosure of precipitation with acetic acid in this reference.
A recent reference, WO98/40413, discloses extraction of hemicellulose by heating corn fiber with alkaline hydrogen peroxide; the peroxide may be added at the same time or after an alkaline material, such as NaOH or Ca(OH)
2
, is added. Significantly, WO98/40413 discloses the hemicellulose extractant as being heated in the presence of the alkaline hydrogen peroxide in order to obtain a suitably white hemicellulose powder from the precipitation step. However, this method is exceedingly dangerous to practice on an industrial scale because of excessive emissions of gas which may lead to significant foaming of the strongly alkaline materials and possibly to explosions.
Furthermore, although hemicellulose itself is a valuable product, the sub-components of hemicellulose are of even higher value. No reference has been located which addresses the extraction of these valuable sub-components from corn fiber. With the invention herein, it has been found that hemicellulose obtained from corn fiber may be subjected to further processing to provide carbohydrate fractions of very high value. That is, in accordance with the invention herein, it has been found possible to extract a number of valuable monosaccharide materials from corn fiber. Also in accordance with the invention herein, it has been found that hemicellulose from corn fiber may be derivatized to form corn fiber arabinoxylan esters and ethers. Methods of processing corn fiber hemicellulose in such a manner are not believed to be disclosed in the prior art.
Other than to obtain hemicellulose, there have been few attempts to exploit the remaining components of corn fiber. A notable recent exception relates to corn fiber oil. Corn fiber oil contains a significant portion of plant sterol esters. These materials
Arumugam Bhaskar K.
Blair Larry
Buchanan Charles M.
Buchanan Norma L.
Debenham John S.
Blake Esq. Michael J.
Eastman Chemical Company
Graves, Jr. Esq Bernard J.
Prats Francisco
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