Synthetic Spider Silk Production: Alfalfa vs. E. coli

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Randolph Lewis


Spider silk is a biodegradable and biocompatible material that is stronger than steel, and more elastic than nylon. Due to spider's cannibalistic and territorial nature, an engineered synthetic process is necessary for spider silk production. Both Escherichia coli and alfalfa are promising hosts for spider silk production at a commercial level. In E. coli this is due to the ease of cloning and it's fast regeneration time; whereas the appeal alfalfa has is due to its richer tRNA pool and the ability the plant has to create proteins on the same size scale as spider silk, 200-320 kDa. Two current limiting factors in spider silk production are: 1) low yields and 2) the synthetic fibers have been unable to match the mechanical properties of natural fibers. Past research has shown that spider silk's mechanical features are tunable by both genetic sequence and post-spin draw manipulations. The size of the synthetic construct is directly correlated to the mechanical characteristics, so the larger the protein the stronger the resulting fiber will be. E. coli's tRNA pool does not innately have sufficient proline and glycine tRNAs for spider silk production. Through molecular cloning additional tRNAs have been inserted into the expression vectors and spider silk has been inserted into the genome of both alfalfa and E. coli. Improvement in both yield and protein size through production in E. coli or alfalfa will create the first commercially viable process for synthetic spider silk.

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