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United States Department of Agriculture

Agricultural Research Service

Project Type: Appropriated

Start Date: Jul 24, 2006
End Date: Aug 09, 2010

To develop biocatalytic methods for the conversion of crop derived carbohydrates to high value polysaccharides or oligosaccharides. The project will be composed of two major objectives. 1) Develop biocatalytic methods for the conversion of starch, corn coproducts, beet sugar, or cane sugar to value-added oligosaccharides. 2) Develop green chemistry ionic liquid-based methods for the biocatalytic production of value-added oligosaccharides. Their common feature is the use of agriculturally derived carbohydrates for the production of high-value products which utilize some of the structural features of the original carbohydrates.

Glycansucrases. Our research in this area will focus on the use of alternansucrase to synthesize oligosaccharides via transfer of glucosyl units from sucrose to mono- or oligo-saccharide acceptors. As alternansucrase is better at catalyzing acceptor reactions than commercial dextransucrase, yielding a better variety of mixed-linkage products, we will first focus on this enzyme. The newly synthesized oligosaccharides are expected to support the growth of specific beneficial microbes in the gastrointestinal tract. We will develop these and other products and determine their structures. The role of oligomer structure and size (degree of polymerization) in fermentability and prebiotic activity will be investigated. This is expected to yield not only new, more strain-specific prebiotics, but will also give rise to a better understanding of the mechanism of prebiotic action. Corn coproducts. This research will utilize abundant, low-value agricultural biomass, particularly corn fiber arising as a coproduct of corn wet milling for production of starch, sweeteners, and ethanol. This is attractive as a model corn residue because it accumulates in enormous volumes in milling facilities and does not need to be collected and transported from fields as do corncobs and stover. Research will also utilize DDGS, an abundant low-value coproduct of dry grind fuel ethanol production. Both corn fiber and DDGS are rich in arabinoxylan, a complex polysaccharide with a backbone of B- (1,4) linked xylose and various side chains and other modifications. Combinations of specific enzymes will be used to cut corn fiber xylan at these linkages to produce a collection of novel oligosaccharides. Transglycosylations in ionic liquids. The approach will be to use commercial enzymes in non-aqueous ionic liquids to produce new prebiotic oligosaccharides and cyclic oligosaccharides that are unattainable in water-based systems. Various ionic liquids, enzymes, and conditions will be tested in order to optimize the non-aqueous transglycosylations. Oligosaccharides produced from this part of the project plan will be tested for prebiotic activity in vitro and in vivo. BSL-1 and Risk Group RG1 recertified September 3, 2009.

Last Modified: 5/23/2015
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