Isolation and characterization of zein from corn distillers' grains and related fractions
1997
Wolf, W.J. | Lawton, J.W. Jr
Corn distillers' grains with solubles (CDGS), the major coproduct of fermentation of corn to produce ethanol, were extracted with 0.1M NaOH, 0.1% dithiothreitol (DTT). and 0.5% SDS yielding 35% of the total nitrogen and approximately 25% of the protein nitrogen. Gel electrophoresis revealed that the extractable proteins contained zein plus other proteins similar to the extractable proteins from corn flour. Although difficult to extract, the proteins isolated from the fermentation coproducts appeared undegraded and apparently survived gelatinization, fermentation, distillation, and drying during the production of ethanol. Extraction of CDGS with 60% ethanol at 60 degrees C yielded 1.5-3.9% of crude zein. When the ethanol contained DTT, yields of crude zein were increased to 3.2-6.6%. Protein contents of the crude zeins were only 37-57%, indicating that lipids and pigments were coextracted with the ethanol. Gel electro phoresis showed that the protein fractions extracted by ethanol contained primarily alpha-zein whereas the proteins extracted by ethanol + DTT contained alpha- + beta-zein. Further confirmation of the presence of zein in the crude prolamin preparations was obtained by amino acid analyses. The amino acid compositions of the crude zeins paralleled those of commercial zein and alpha-zein.
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