Date of Award:
Master of Science (MS)
Biological and Irrigation Engineering
Spider silk has long been a subject of scientific research due to its remarkable mechanical properties. Until recently, there has been no way to effectively obtain spider silk except by harvesting it from individual spiders. With advances in technology, the genes that code for the individual spider silk proteins have been isolated and genetically engineered into other hosts to produce recombinant spider silk proteins (rSSp) of varying sizes, Larger rSSp have correspondingly greater mechanical properties in any resulting materials. Using current production methods, larger rSSp cannot be produced in commercially viable quantities while simultaneously being economically viable. The current production methods have shown that small rSSp are easier to produce and purify in genetically engineered systems while maintaining favorable yields. After the small molecular weight rSSp were expressed and purified, they were polymerized to form larger molecular weight rSSp, while having maintained mechanical properties of similarly sized rSSp from other expression systems.
To accomplish this polymerization, two systems were designed that can catalyze this reaction: using a Spy System and an intein system. These two systems require no external cofactors or enzymes and occur spontaneously once initiated. The expression and purification of rSSp from both of these systems has been characterized. The Spy System did not produce high enough quantities of rSSp to be economically viable. Whereas the intein system produced yields of 5 g/L, which is higher than previously reported. The rSSp from the intein system have been made into biomaterials, such as films, hydrogels, and aerogels. The mechanical properties of these biomaterials were comparable to biomaterials from other spider silk protein production. Utilizing the intein system, projected cost estimates for the production of rSSp has been lowered from $350 to $40 per kilogram. This decreased cost of rSSp would allow a wider array of commercial applications.
Hebert, Nathan L., "Novel Methods to Produce Large Recombinant Spider Silk Proteins via Polymerization" (2018). All Graduate Theses and Dissertations. 7240.
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