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United States Department of Agriculture

Agricultural Research Service

Research Project: Improved Utilization of Proteinaceous Crop Co-Products and Residues

Location: Plant Polymer Research

2012 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:
The use of ultrafiltration-diafiltration (UF-DF) in purifying corn germ protein has continued. The wet milled germ was reduced to 0.4 mm before extraction. This reduction gave higher protein extraction (40%) relative to previous techniques (~27%). Purity of the extract improved from 30 to 40%. The UF-DF protein extract was more soluble (50%) than acid-precipitated (AP) protein (30%). Surprisingly the UF-DF protein had the same solubility in acidic, neutral, and alkaline conditions. This enhanced solubility brings higher value. The protein was a better emulsifier than protein recovered by our baseline method. We anticipate that other UF-DF properties, such as foaming, will also be improved. Emulsification and foaming properties are important in products such as paints, shaving foams, and facial creams. Extraction of proteins from alfalfa leaves and stems using various solvents was performed. Water-soluble protein was the dominant fraction (40%), while saline-soluble protein had the least amount (3%). For pennycress seed, we compared traditional acid-precipitated and saline extraction (SE) to extract protein. SE gave higher protein extraction (40% vs. 34%), but both produced pennycress protein of high purity (90%). Pennycress protein is highly soluble in acidic (68%), neutral (74%), and alkaline media (90%), has good foaming and emulsifying ability. We have evaluated impact of nine salts with differing capabilities of interacting with proteins on zein properties. We found that these salts act as plasticizers. Guanidine thiocyanate gave higher elongations than control while magnesium thiocyanate gave zein articles with lower elongation. As elongation is increased, tensile strength decreases. The use of these salts in zein formulations with high tensile strength but low elongation did not result in improved elongation. The use of anhydrides to modify zein (in solution and melt) and soy (solution only) proteins has been studied. The modification of soy has been hampered by insolubility. Zein has been modified by acetic anhydride (Ac2O) and poly(ethylenemaleic anhydride). Solutions of zein modified with Ac2O can be electrospun to give fiber mats composed of a mix of round and ribbon fibers. Value in use is in progress. Historically zein has been used in the textile fiber market and re-introduction into this market will require additional fundamental knowledge. While acetic acid (AcOH) and 90% ethanol-water (EtOH-H2O) have both been shown to provide electrospun fibers, mixtures of these solvents have not been studied. In AcOH the 1.0 micron fibers are round while in EtOH-H2O the 4 micron fibers are ribbons. The change in fiber structure occurs at 30% AcOH/70% EtOH-H2O. The sample viscosity begins to increase significantly at this point. Efforts are in progress to understand what other solution properties may be changing with these solvent changes.


4.Accomplishments
1. Isolation of proteins from pennycress and alfalfa. Pennycress seed oil is being developed as a biodiesel source, but little is known about the seed’s protein, which is a likely co-product from oil processing. Similarly, alfalfa, which is used primarily as animal feed, has drawn attention as a potential source for cellulosic bio-ethanol. Success of an alfalfa-based cellulosic-ethanol industry would require development of new uses of the alfalfa co-products (e.g. protein). ARS, Plant Polymer Research Unit scientists at the National Center for Agricultural Utilization Research in Peoria, IL, have identified the major protein classes in pennycress seed and alfalfa leaves or stems. Based on the fractionation results, extraction methods were designed that use simple solvents to produce high-purity protein extracts. We are also demonstrating that pennycress seed proteins have notable functional properties, such as solubility in variable aqueous systems emulsification and foaming that would be desirable for industrial applications. Products that rely on emulsification, foaming, and water-holding capacity include water-based paints, shaving creams, and facial creams. Thus, developing novel uses based on these properties will increase the value of pennycress and alfalfa crops.

2. Development of a new corn protein based product. One of the reasons that zein (corn protein) has received little interest from industry for the production of ‘plastic’ parts, is its relatively poor solvent resistance. Before the advent of polymers based on fossil fuels, zein was modified using formaldehyde. While formaldehyde can be used effectively, it does require costly investment to handle it safely. Alternative technologies are necessary to allow the conversion of zein into valued products with improved solvent resistance requiring relatively low investment. ARS, Plant Polymer Research Unit scientists at the National Center for Agricultural Utilization Research in Peoria, IL, have found that certain anhydrides may be capable of converting zein into solvent durable materials at low investment. These results are significant to companies evaluating the use of zein in making ‘plastic’ articles and increase the value of this coproduct.


Review Publications
Selling, G.W. 2012. Electrospun fiber and cast films produced using zein blends with nylon-6. Journal of Applied Polymer Science. 123(5):2651-2661.

Last Modified: 4/24/2014
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