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United States Department of Agriculture

Agricultural Research Service

Research Project: Modification of Natural Polymers by Novel Processes

Location: Plant Polymer Research

2011 Annual Report


1a.Objectives (from AD-416)
The long-term objective of this project is to develop processes to enhance the conversion of cereal crops and residues into value added polymers, demonstrate the useful properties and applications of these biobased materials, reduce dependence on petroleum and increase utilization of environmentally friendly renewable resources. Objective 1: Develop technologies that enable commercially viable products composed of lipid and amylose or modified starch complexes with novel micro- and nano-sized spherulitic morphologies; Objective 2: Develop reactive extrusion-based technologies that enable commercially viable graft co-polymers from starches and lignocellulosics; Objective 3: Develop novel chemical and thermal processes that enable the commercially viable production of derivatives of starches, lignins, and lignocellulosics; Objective 4: Develop novel biocatalytic processes to produce commercially viable derivatives of starches, lignins, and/or lignocellulosics.


1b.Approach (from AD-416)
New biobased products and sustainable processing technologies are needed to replace industrial and consumer products made from petroleum based feedstocks. This project focuses on making polymeric materials with a variety of useful applications from starch and associated low cost coproducts of corn processing and harvesting. In order to accomplish this, modified biopolymers with new or improved properties need to be prepared and processing technologies which are more efficient, i.e. use safer or less solvent, are faster, have more complete reaction and fewer byproducts need to be developed. Specific objectives for this project include:.
1)prepare novel spherulitic starch-polymer composites via jet-cooking;.
2)prepare starch graft copolymers with controlled structure by reactive extrusion and evaluate applications;.
3)prepare modified starches, celluloses and lignins with novel structures via processing with ionic liquids, microwaves and autoclave heating; and.
4)prepare new starch and lignin graft copolymers as well as polyglutamic acid and polyhydroxyalkanoates by enzymatic and microbial catalysis. Overall, this research will lead to biobased polymer products which will have new or improved properties, have lower cost, are more environmentally friendly and thus will be more acceptable to consumer markets.


3.Progress Report
The overall goal of this project is to develop processes to enhance the conversion of cereal crops and byproducts from cereal crop processing into value added polymers and thus generate expanded markets and reduce dependence on petroleum. Specifically, modified corn starches, corn cellulose, and lignin with novel properties are prepared by chemical, enzymatic, and physical processing techniques. In initial studies, experimental conditions for the preparation and processing of starch-polymethylacrylate (PMA) plastics that are reproducible in replicate experiments were developed. ARS Plant Polymer Research Unit Scientists at the National Center for Agricultural Utilization Research in Peoria, IL, determined that temperature control was a critical factor in the preparation of starch-PMA graft copolymers. Researchers also determined that PMA could be graft polymerized onto the spherulite reinforcing agents used in these studies, thus improving their compatibility with the continuous plastic phase. This research will enable us to accurately evaluate the reinforcing effects of starch-based spherulites on plastics products prepared from starch-PMA graft copolymers. Promising results have been recently generated using reagents that place isolated and conjugated olefins on starch that can be later chemically modified giving unique improved starch graft copolymers. Starch was reacted with monomers and radical sources using a procedure called controlled radical polymerization to give polymers with a smaller range of molecular weights. To date, we have found that such reactions provide polymers with a smaller range of molecular weight in high yield. However, the number of polymers bound to starch is very low. Efforts are in progress now to vary reaction conditions and radical sources to drive this to higher values. Viscoelastic properties of starch-polyacrylamide graft copolymers prepared by reactive extrusion were found to recover quickly after shearing. This unique behavior suggests that such graft copolymers may have viscoelastic properties suitable for certain biomedical applications such as hydrogels in tissue engineering and for encapsulation and regenerative medicine. The solubility of different agricultural materials in different ionic liquids was assessed. Solubilities depended on the particular ionic liquid with 1-ethyl-3-methyl-1H-imidazolium (EMIM) acetate often performing the best. Acetates and mixed esters of certain agricultural waste materials were prepared in an efficient manner. Polyglutamic acid (PGA) was prepared by fermentation of corn byproducts and soy flour with bacteria known or suspected of producing PGA from the Agriculture Research Service Culture Collection and American Type Culture Collection. Of the 21 cultures selected, none produced PGA when grown on corn distiller’s solubles. Bacterial cultures extracted from natto soybeans were also grown on moist corn fiber, distiller’s dry grains with solubles, corn gluten meal, corn steep liquor, and soy flour. Bacterial growth was visible on all substrates but PGA production (as visualized by viscous exudates) occurred only on soy flour.


4.Accomplishments
1. Aqueous cellulose gels from corn cobs. There is little current commercial utilization of corn cobs so new value-added uses would add to farm income. ARS Plant Polymer Research Unit scientists at the National Center for Agricultural Utilization Research in Peoria, IL, found that sodium hydroxide/bleach extract of corn cobs forms a clear gel in water. The gel was made up of tiny interlocking cellulose microfibrils. The strength of the gel was much higher than cellulose gels prepared in the past from other agricultural materials and other methods. The gel can be used by food and biomaterials industries for production of food products, cosmetics and medical dressings.

2. Antioxidant starches. Corn starches with new properties and applications could be created if techniques were developed to attach new types of molecules onto starch. In particular, it is desirable to combine good film-forming properties of starch with the antioxidant/antimicrobial properties of plant polyphenols such as lignin or tannins. However, there have been no previous reports of such adducts since starch and polyphenols do not easily react. ARS Plant Polymer Research Unit scientists at the National Center for Agricultural Utilization Research in Peoria, IL, have now shown that starch-lignin copolymers can be prepared using an enzyme in the presence of air. The starch-lignin copolymers made with an enzyme should be suitable for food and medical uses. Because lignin can be an antioxidant, the direct addition of this copolymer to food and cosmetics may reduce oxidation and prolong storage. The copolymer may also be made into films and fibers for applications like food packaging and wound dressing. This information will benefit scientists in academia and food/medical industries who are involved in making coatings for food preservation, increasing antioxidant levels in foods, improving air and UV stability of cosmetics, and making antibacterial medical dressings.


Review Publications
Cheng, H.N., Biswas, A. 2011. Chemical modification of cotton-based natural materials: products from carboxymethylation. Carbohydrate Polymers. 84:1004-1010.

Nichols, N.N., Sutivisedsak, N., Dien, B.S., Biswas, A., Lesch, W.C., Cotta, M.A. 2011. Conversion of starch from dry common beans (Phaseolus vulgaris L.) to ethanol. Industrial Crops and Products. 33(3):644-647.

Byars, J.A., Fanta, G.F., Felker, F.C. 2011. Rheological properties of starch-oil composites with high oil:starch ratios. Cereal Chemistry. 88(3):260-263.

Last Modified: 4/24/2014
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