Page Banner

United States Department of Agriculture

Agricultural Research Service


Location: Plant Polymer Research

2011 Annual Report

1a. Objectives (from AD-416)
The long-term objective of this project is to develop novel products utilizing current and new co-products from the industrial processing of agricultural materials. By accomplishing this, our research will reduce dependence on non-renewable materials and produce higher value products that will benefit a large segment of our economy. Objective 1: Develop technologies that enable commercially viable biobased materials from the proteinaceous co-products produced during cereal and soy processing. Objective 2: Develop novel extraction techniques that enable the commercially viable biorefining of new protein-rich industrial feedstocks such as alfalfa and pennycress.

1b. Approach (from AD-416)
Improve extraction, isolation and derivatization techniques; develop new routes to isolate and characterize proteinaceous materials from corn, soy, pennycress and alfalfa. Proteins will need to be physically or chemically modified in solution and in melt state in order to impart valued properties required for the desired applications.

3. Progress Report
Significant progress has been made in the areas of protein isolation, purification, and development of improved zein products and processes. Studies have been completed on the cross-linking reactions of glyoxal, formaldehyde and poly(ethylenemaleic anhydride)(PEMA) with zein solution. These results are the first to characterize the chemical reaction of zein. PEMA, as a polymer, has safety advantages. Compression molded samples and fabrics made using PEMA have improved solvent resistance. Zein has been found to form a compatible film with nylon-6 when using less than 10% nylon-6. Film tensile strength was improved by 33%. Surprisingly, the nylon-6/zein films also had improved solvent resistance. Fibers were also produced which were shown to be resistant to water. Zein was subjected to extrusion processing up to seven times at a temperature of 140 degress C (higher temperature affects physical properties) to test recyclability. After passing through the extruder four times, differences were seen in the polymer molecular weight and color. Polymer physical properties appeared unaffected by multiple passes. This suggests that zein based articles could be recycled through an extruder up to three times. Found that ammonium thiocyanate [NSCN] can improve elongation when combined with tri(ethlylene glycol) [TEG]. When 2, 4, and 8% NSCN and 17.5% TEG are added to zein, elongation increases from 52% to 223, 500, and 1680% respectively. These improvements are unprecedented at the levels of additives used. Unfortunately, tensile strength decreases dramatically as well. Research is underway to understand how NSCN affects elongation in order to reduce the tensile strength impact. Two-step extraction (dilute saline then dilute alkali) followed by ultra/ diafiltration (UF-DF) had the highest corn-germ protein extraction efficiency (46%), while acid-precipitation (AP) had the lowest yield (16%) of corn germ protein. Using only dilute saline solution or the enzyme-aided procedure had similar extraction efficiencies (33%). The product obtained by AP had the highest protein content (51%), while other methods all contained approximately 35% protein. Zein can be derivatized with a diisocyanate (MDI) in the melt state and provide compression molded samples with improved modulus while retaining tensile strength and flexibility. Modification is necessary as zein-nanoclay composites have some deficient properties relative to control. Nanoclays are available that have groups on them that can react with MDI, so that the MDI will couple the pigment and the zein. It is expected that the resulting zein-nanoclay-MDI composite will have superior properties suitable for replacing petroleum based products. To maximize pennycress (a new source biodiesel) value, it must be fully utilized. We have found that dilute saline had the highest yield (23%) at removing quality protein (83%) from pennycress seed or press-cake (left over after oil extraction). The main impurities were carbohydrates. Research is in progress on examining how upstream seed processing affects protein extraction as well as defining the functional properties of the extracted proteins.

4. Accomplishments
1. Improved zein product. Zein is the main corn protein produced during the industrially processing of corn. By developing a zein based article with improved properties, the co-products produced by the bio-ethanol and corn starch industries will have higher value, providing economic benefits to these industries. ARS Plant Polymer Research Unit scientists at the National Center for Agricultural Utilization Research in Peoria, IL, found that poly(ethylenemaleic anhydride)(PEMA) has been used to modify zein to provide improved properties. Two of the main deficiencies of zein are poor solvent resistance (water turns articles into gum) and low strength (breaks too easily). As PEMA is a polymer, it is one of the safest reagents tested to date to modify zein. PEMA modified zein provides films and molded articles with improved solvent resistance and strength. Unlike other historic reagents, PEMA films do not require an additional thermal treatment to impart solvent resistance. These films could be used as an industrial coating (e.g. paint or paper) or the technology could be adapted for the production of traditional ‘plastic’ parts using standard plastic processing. Successful scale-up and transfer of this technology will allow zein based materials to replace articles produced using fossil fuels.

2. Zein polymer blend. Fully utilizing the co-products of industrial corn processing will have a beneficial impact on this large sector of our economy. Corn protein, zein, is one of the main potential co-products from corn processing. Historically, articles made using zein had deficient strength (breaks too easily) and solvent resistance (water turns articles into gum). It has been found by the polymer industry, that blending two polymers may provide a product with an improved balance of properties; at times the blends have deficient properties. There are very few examples of blends of zein where properties are improved. ARS Plant Polymer Unit scientists at the National Center for Agricultural Utilization Research in Peoria, IL, found that nylon-6 (commercially produced in billions of pounds) and zein form compatible blends. Surprisingly, incorporating small amounts of nylon-6 (2-8%) into zein provide films with improved strength. In addition, solvent resistance of the films is improved. Solutions of nylon-6/zein can be used to make small diameter fibers that have improved solvent resistance as well. These films could be used as industrial coatings such as in the paint or paper industries. Successful scale-up and transfer of this technology will have a very large beneficial impact on the bio-ethanol industry.

Review Publications
Selling, G.W. 2010. The effect of extrusion processing on zein. Polymer Degradation and Stability. 95(12):2241-2249. Available:

Shogren, R.L., Selling, G.W., Willett, J.L. 2011. Effect of orientation on the morphology and mechanical properties of PLA/starch composite filaments. Polymers and the Environment. 19(2):329-334.

Selling, G.W., Woods, K.K., Biswas, A. 2011. Electrospinning formaldehyde cross-linked zein solutions. Polymer International. 60(4):537.

Sessa, D.J., Woods, K.K., Mohamed, A., Palmquist, D.E. 2011. Melt-processed blends of zein and polyvinylpyrrolidone. Industrial Crops and Products. 33(1):57-62.

Sessa, D.J., Woods, K.K. 2011. Purity assessment of commercial zein products after purification. Journal of the American Oil Chemists' Society. 88(7):1037-1043.

Selling, G.W., Biswas, A., Woods, K.K. 2011. Electrospun zein fibers using glyoxal as the cross-linking reagent. Journal of Applied Polymer Science. 60(4):537-542.

Last Modified: 06/24/2017
Footer Content Back to Top of Page