Objective 1: Develop fermentation technologies to synthesize and expand our collection of microbial biosurfactants (i.e., mannosylerythritol lipids, trehalose lipids, cellobiose lipids, sophorolipids, rhamnolipids etc.) and assess their commercial application potential through antimicrobial activity and surfactancy. Objective 2: Develop fermentation technologies to synthesize unique polyhydroxyalkanoates (PHA) biopolymers from low-value agro-industrial byproducts. Objective 3: Develop technologies that enable high performance products from agricultural fibers and biopolymers.
The aim of this project is to enable the development of new commercial uses for microbially-produced lipid-based molecules (i.e., glycolipid biosurfactants, biopolymers) and agricultural protein fibers (i.e., keratin, collagen) such that the newly formed materials are more cost-effective and commercially valuable. By using a multi-faceted synthetic approach, both microbial glycolipids (i.e., sophorolipids, rhamnolipids, mannosylerythritol lipids, trehalose lipids etc) and biopolymers (i.e., polyhydroxyalkanoates) will be synthesized using both lipid-based production (fermentation) strategies and modified using green chemistry synthesis techniques. Metabolic engineering and fermentation optimization of the bioprocesses for both glycolipid and biopolymer synthesis will be studied. Particular attention will be directed towards production economics and the use of inexpensive feedstocks for fermentation protocols as well as the creation of new functionalities to the bio-based products in an effort to improve their application potential. Structure-function analyses will be conducted on all newly-synthesized/produced materials such that their application potential will be fully understood for such areas as antimicrobial agents, lubricant additives, plastic substitutes, to be further derivatized to form new biobased precursors and products (i.e., polyurethanes, amphiphilic biopolymers) and be combined with protein fibers to form green composites with improved tensile strength and toughness. The effect of fiber length and diameter will be assessed for maximum potential and electrospinning will be employed to produce fibrous mats for application in green composite formation. Techno-economic analyses will be performed on all synthetic processes that result in favorable products.
For Objective 1- Project scientists developed the conditions for the fermentative production of a 13-hydroxydocosanoic acid sophorolipid biosurfactant containing a 22-carbon fatty acid moiety. Sophorolipids are relatively well-known glycolipids that are produced by various members of the Starmerella clade, but the C22 sophorolipid is a unique molecule that is minimally understood from an application perspective. The yeast Pseudohyphozyma bogoriensis was used to produce the C22 sophorolipid in a 10-L volume under batch fermentation conditions. The media was composed of glucose (40 g/L) and yeast extract (2 g/L) under the conditions of 25 degrees C, impeller speed of 500 rpm, and a 1.5 L/minute aeration rate. The fermentation was completed after 14 days and resulted in a titer of approximately 50 g of C22 sophorolipid / L of growth media. While these molecules' surface tension lowering and antimicrobial activities have been previously studied, little is known about their cleaning efficiency towards various fibers. These studies are the next step in the progression towards fulfilling the goals outlined in Objective 1. For Objective 2- Project scientists have determined the growth parameters for synthesizing polyhydroxyalkanoate (PHA) biopolymers containing unsaturated side-chains, which can be utilized for further chemical modification. Various members of the genus Pseudomonas have the genetic capability to produce PHA biopolymers with double bonds in their side-chains; however, the synthesis of PHA biopolymers with terminal double bonds in their side chains is unique. A strain of Pseudomonas oleovorans was grown under shake flask conditions in simple salts media using 10-undecenoic acid as a carbon source to produce PHA biopolymers with a high concentration of terminal double bonds. These biopolymers will serve as the precursor molecules for the production of polymeric surfactants, antimicrobial biopolymers, and novel polyurethanes in subsequent studies within the context of the new 5-year project plan. In a related collaborative study, the utilization of corn stover hydrolysate and levulinic acid as fermentative co-substrates was successfully demonstrated as a means of utilizing renewable plant byproducts and inexpensive plant-derived organic acids to produce thermoplastic PHA biopolymers. These results will contribute to the efforts involved in further reducing the cost of PHA biosynthesis to provide a more cost-effective environmentally-friendly substitute for petroleum-based plastics. For Objective 3, project scientists developed methods to prepare wool (Lincoln coarse wool fibers provided by the Chargeurs Wool USA) and collagen fibers (derived from a limed hide) as fillers to fabricate PHB composites. Three different fibers were prepared: wool, untanned collagen, and vegetable-tanned collagen. Wool fibers were cut into different lengths ranging from 1-10 mm. Fine wool powders were also processed using a freeze mill (6800 Freezer/Mill, Spex Certiprep). A Willy mill was used to reduce the collagen fiber’s average length to about 0.5-4mm. Fibers and biopolymers (PHB) were mixed with a composition ranging from 0.5%, 1%, and 2% fibers, then charged into a melt flow index (MFI) tester and heated to 190 degree C. The melted mixtures were extruded into composite filament under constant pressure. Observation showed the wool containing extruded filaments is a little rough and thinner than the other ones. MFI data showed no significant difference in flow rate between pure PHB and PHB mixed with 1 or 2% fibers.
1. Improvement of the surface hydrophilicity of wool fibers. Improvement of the surface hydrophilicity of wool fibers. The hydrophobic surface of wool fiber could be a barrier for the further modification of fibers due to covalently bonded 18-methyleicosanoic acid (18-MEA). ARS scientists at Wyndmoor, Pennsylvania, introduced a base/cationic detergent (sodium carbonate solution containing cetyltrimethylammonium hydroxide (CTAB)) to alter the surface feature wool, thereby facilitating the modification of wool fiber, such as enzyme treatment. The solution could effectively hydrolyze the thioester bonds connecting fibers and 18-MEA while limiting the damage on wool. According to the water contact angle measurement, the modified wool fabric surface exhibited a very hydrophilic feature compared with control.
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