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 lay er into the byproduct known as corn fiber, which is combined with Othe r materials (e.g., steep and fermentation liquids) to make corn gluten feed. Increased fuel ethanol production from corn will necessitate ot her 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 pro cedures were examined for rapid extraction of CFX from corn fiber to o btain a purified material with good recoveries. Using 2% calcium hydro xide and precipitation with ethanol yielded a relatively pure CFX mate rial but required long extraction times (16-20 h) and produced a hard, insoluble fiber residue. Extractions with 15% ammonium hydroxide yiel ded a rather impure CFX material and required similar long extraction times. Extraction with potassium hydroxide solutions were attempted us ing various combinations of time, temperature, and concentrations. Ext raction with 2% potassium hydroxide at 70 degrees C for 4-6 h, coupled with calcium hydroxide treatment of the dissolved CFX, produced a hig hly pure CFX material composed of about 94% neutral sugars (34% arabin ose, 52% xylose, 7% galactose, 8% glucose), 7% hexuronic acids, and 3% protein. The overall CFX yields were good (15%), and the residual fib er material still appeared physically suitable for use as a feed or fo r other uses.