Title: Corn Fiber: Structure, Composition, and Response to Enzymes for Fermentable Sugars and Coproducts Authors
Submitted to: Applied Biochemistry and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 25, 2007
Publication Date: May 5, 2008
Citation: Akin, D.E., Rigsby, L.L. 2008. Corn Fiber: Structure, Composition, and Response to Enzymes for Fermentable Sugars and Co-Products. Applied Biochemistry and Biotechnology. 144(1):59-68. Technical Abstract: Corn (Zea mays L.) fiber, which is the seed coat and residual endosperm left after grain processing, is a low-value residue that contains carbohydrates and aromatic compounds. Pretreatment of corn fiber to release fermentable sugars could increase ethanol production efficiency as well as make available value-added co-products. Research was undertaken to determine the composition of aromatics within cell walls of corn fiber and the use of specific enzymes to release sugars and ferulic acid. Histochemical reactions in the pericarp and aleurone layer suggested the presence of phenolic acids. Treatment of corn fiber with various alkali treatments and assessment by gas chromatography indicated a prevalence of ferulic acid, most of which was ester-linked in the cell walls. Milled corn fiber was incubated with commercial ferulic acid esterases and cellulase, and phenolic acids and sugars released into the filtrate were determined after various protocols. Enzymes containing ferulic acid esterase were effective in releasing ferulic and p-coumaric acids and sugars (e.g., glucose, xylose) in the incubation medium. Subsequent incubation of the residue with cellulase released more of these compounds. Esterase followed by cellulase released significantly more fermentable sugars and ferulic acid than cellulase alone. Various milling methods were tested to improve accessibility to enzymes and further increase the release of sugars and ferulic acids. Ball milling changed the particle distribution, significantly improved degradation, and increased the enzymatic release of fermentable sugars and ferulic acid into the medium. Pretreatment of corn fiber with ferulic acid esterases offer an opportunity to provide additional sugars and aromatic co-products from corn fiber.