Extraction and characterization of hemicellulose from the corn fiber produced by corn wet-milling processes

The industrial processing of corn by wet-milling converts the hull layer into the byproduct known as corn fiber, which is combined with Other materials (e.g., steep and fermentation liquids) to make corn gluten feed. Increased fuel ethanol production from corn will necessitate other uses of corn fiber. More than 30% of the corn fiber is in the form of a xylan (CFX) composed mainly of xylose and arabinose. Various procedures were examined for rapid extraction of CFX from corn fiber to obtain a purified material with good recoveries. Using 2% calcium hydroxide and precipitation with ethanol yielded a relatively pure CFX material but required long extraction times (16-20 h) and produced a hard, insoluble fiber residue. Extractions with 15% ammonium hydroxide yielded a rather impure CFX material and required similar long extraction times. Extraction with potassium hydroxide solutions were attempted using various combinations of time, temperature, and concentrations. Extraction with 2% potassium hydroxide at 70 degrees C for 4-6 h, coupled with calcium hydroxide treatment of the dissolved CFX, produced a highly pure CFX material composed of about 94% neutral sugars (34% arabinose, 52% xylose, 7% galactose, 8% glucose), 7% hexuronic acids, and 3% protein. The overall CFX yields were good (15%), and the residual fiber material still appeared physically suitable for use as a feed or for other uses.