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Corn+Soybean Digest

So What's Zein?

Ethanol plants could begin seeing demand for zein (pronounced ZEE-in), one of ethanol's byproducts, coming from new market areas in the months ahead. New uses for the well-known corn protein are on the horizon, thanks to efforts of researchers at the ARS National Center for Agricultural Utilization Research (NCAUR) in Peoria, IL.

NCAUR chemist David Sessa developed a new method for purifying zein to remove its color and odor components. Those two elements make zein undesirable for use in a variety of products, including biomedicines.

UNPURIFIED ZEIN is currently used in specialty coatings, such as for paper. The new process makes commercial production of purified zein economically viable. It may now be suitable for cosmetic and biomedical applications.

“Sessa's process is not only elegant, it's a very cost-effective way to use zein, which is now readily available from ethanol byproducts,” says Bruno Marino, consultant to Global Protein Products, Inc. “Global Protein will be using Sessa's process and take our pilot scale operation to a commercial scale.”

Marino says Global Protein isn't ready to discuss the types of products they'll produce with zein, but notes there is an industrial demand for the product.

“Chewing gum manufacturers would like to use zein,” he says. “Its properties also make it a viable option for use in the medical field. Because of its plant origin, there's no danger of prion (an animal protein known to cause disease) or viruses. It appears to be the only plant-based component suitable for tissue scaffolding, used for skin regeneration.”

UNTIL SESSA MADE his breakthrough, activated carbons were used to bind and trap the compounds causing zein's color and odor. Between 37% and 95% of zein was lost in the process, causing the end product to be very costly. Sessa's study of the existing process led him to use zeolites, silicate or clay-based particles, whose pores act as molecular sieves to trap zein's color and odor compounds. He's been able to reduce zein's absorption to 25% to minimize the loss and make the process both more satisfactory and economical.

Because zein is an incomplete protein and has little nutritional value, its use for commercial products doesn't threaten world food costs or supplies.

In 2007, 7.8 billion gallons of ethanol production resulted in 14.6 million metric tons of dried distillers' grains (DDGs). Extracting zein from DDGs will make it a more economically appealing product; it was previously derived from corn gluten meal.

“If you can accomplish that with low cost, you open up all sorts of doors,” he says.

Zein was first identified in 1897. It forms tough, glossy, hydrophobic grease-proof coatings highly resistant to microbial attack. Potential uses for zein manufactured at low cost include fiber, adhesives and ink. Zein can be transformed into a renewable and valuable maize coproduct, in Global Protein's opinion.

“As such, a commercial supply of zein could have a positive effect on corn pricing, but many uncertainties remain,” Marino says. “High-value applications for zein are now particularly attractive as a result of Sessa's technology, offering a consistent source of the material not previously available. Zein will likely be recognized as a preferred renewable biopolymer by those seeking a green edge in their products.”

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