Location: Plant Polymer Research
2015 Annual Report
Objectives
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. As a result 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: Enable, from a technological standpoint, the commercial production of marketable products from the proteins in crops such as pennycress, camelina, soybean, cottonseed or corn. Sub-objective 1A. Establish pilot-scale extraction and biorefining techniques that generate protein-rich industrial feedstocks from plant crops, such as pennycress, camelina, soybeans, or cottonseed.
Sub-objective 1B. Determine ability to form solvent cast and melt processed films or articles, as well as surface and interfacial tension agents; determine if suitable chemical modifications of these proteins will provide products that can replace petroleum-based products.
Approach
Establish pilot-scale extraction and biorefining techniques that generate protein-rich industrial feedstocks from plant crops, such as pennycress, camelina, soybeans, or cottonseed. Determine ability to form solvent cast and melt processed films or articles, as well as surface and interfacial tension agents. Determine if suitable chemical modifications of these proteins will provide products that can replace petroleum-based products.
Progress Report
Pilot-scale isolation of pennycress protein isolate (PP) was undertaken using alkali solubilization-acid precipitation. The extraction utilized NaOH at elevated temperature to solubilize and extract the protein followed by acidification to precipitate the PP. After dissolution, the protein fraction was subjected to ultrafiltration/diafiltration and freeze-drying. The pilot-scale process gave a yield of ~10% and provided PP isolate having ~75% protein. Both values are lower than those noted for the bench-scale method. Protein loss was monitored through the process where it was determined that the major yield loss took place during the initial extraction and during dissolution after acid precipitation. Adjustments are being employed, such as insertion of a filtration step after alkali solubilization, increased volume of water, and increased re-dissolution time in water, to improve PP yield and product purity.
The pennycress protein (PP) produced from larger scale extractions was further characterized. Infrared analysis of PP demonstrated that the predominant secondary structure present in PP is the beta sheet; the increased H-bonding may deliver improved physical properties. The major impurities in the PP are carbohydrates. Differential scanning calorimetry has shown that PP has a glass transition temperature of ~80°C and degradation temperature of ~190°C. This suggests a fairly large processing window to allow for melt based extrusion processing. Of the many solvents tested, only formic acid was found to provide a PP solution with good properties at elevated concentration. An exponential relationship was found between PP concentration and viscosity. Quality films could be produced from PP in formic acid using glycerol and triethylene glycol as plasticizers.
Zein films and fibers have been found to have value in the delivery of reagents such as pharmaceuticals or other valued materials. These external studies have all used zein in its as-is state and small reagents. The impact of zein cross-linking, temperature and reagent size were all shown to have a significant impact on the rate of release of the reagent. Using glyoxal as a crosslinker reduced the reagent release rate by 30%. Increasing the temperature of the system can increase the rate of release by between 70 and 700%. Increasing the size of the reagent decreased the rate of release.
The impact of dehulling on protein extraction of coriander seeds was undertaken. It was found that dehulling coriander seeds increased crude protein content by 70%, to 22% from 13.0% in whole seed, reduced the crude fiber by 28%, and reduced other carbohydrates by 65%. The protein was extracted using conventional alkali solubilization and acid precipitation. The freeze-dried recovered product from ground dehulled seed had 82% protein with 36% protein yield. This is a better balance of properties than that obtained when using coriander whole seed/press cake.
Accomplishments
1. Pilot scale isolation of pennycress protein. 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. ARS scientists in Peoria, Illinois, have carried out larger scale extractions on pennycress press cake (that which is left over after oil removal) to provide larger amounts of pennycress protein (PP). To date, there is no information on the use of pennycress co-products. The utilization of all parts of the pennycress seed is of vital importance to the overall effort in developing this new product. Developing larger volumes of the PP isolate will allow other researchers to develop information on the food and non-food use of this novel protein. In this way, new high value uses will be developed that can support the overall pennycress effort which will result in an additional revenue stream for farmers and downstream processers. This additional revenue will support research efforts by other ARS scientists in developing a stake for the use of pennycress to produce biodiesel.
2. Improved value in use of pennycress protein. The development of a pilot scale process to isolate pennycress protein (PP) has allowed additional testing on pennycress protein to define possible end-uses for this new protein. ARS scientists in Peoria, Illinois, have generated new information regarding PP to define value in non-food markets. It was determined that PP has a higher amount of a certain protein structure, called the beta-sheet, which may provide improved properties allowing it to provide films or fibers with higher strength. In order to be economically processed, polymeric materials should be able to be melt extrusion processed. While melt extrusion processing has great economic value, many industrial processes employ solution processing of polymers. A study was undertaken to define potential solvents for PP. The key metrics for a PP solution are high solids (>10%) and solution clarity. Of the many solvents evaluated, formic acid was found to provide the best solution properties. Films were produced from PP in formic acid using various reagents as plasticizers. Films without defects were produced. The information generated suggests that PP may be able to be processed using either melt or solution processes in non-food applications. This will be of value in supporting the overall pennycress effort which will result in an additional revenue stream for farmers and downstream processers.
Review Publications
Hojilla-Evangelista, M.P., Selling, G.W., Berhow, M.A., Evangelista, R.L. 2015. Extraction, composition and functional properties of pennycress (Thlaspi arvense L.) press cake protein. Journal of the American Oil Chemists' Society. 92(6):905-914.
Evangelista, R.L., Hojilla-Evangelista, M.P., Cermak, S.C., Isbell, T.A. 2015. Dehulling of coriander fruit before oil extraction. Industrial Crops and Products. 69:378-384.
