Dragline spider silk stands out as one of the strongest and toughest natural materials and has motivated decades of effort to produce recombinant silk fibers in alternative hosts. However, achieving the unparalleled combination of high strength and toughness exhibited by natural spider silks has proven to be extremely difficult. In this talk, I will discuss multiple synthetic biology strategies we have developed to produce strong silk fibers from bacterial hosts. We first used a combination of microbial engineering and split intein chemistry to produce recombinant spidroins of previously unobtainable protein size (556 kDa), containing 192 repeat motifs of the Nephila clavipes dragline spidroin. Fibers spun from our synthetic spidroin were the first to fully replicate the mechanical performance of its natural counterparts by all common metrics, reaching high tensile strength (1.03 ± 0.11 GPa) and toughness (114 ± 51 MJ/m3). We further engineered the spider silk sequence by substituting the beta-nanocrystal-forming polyalanine with amyloid sequences. The resulting polymeric amyloid proteins can be more easily biosynthesized in engineered microbes, and the fibers have displayed higher strength and toughness compared to polyalanine fibers of similar molecular weight. Further increasing the molecular weight of the polymeric amyloid protein resulted in fibers with tensile strength of 0.98 ± 0.08 GPa and toughness of 161 ± 26 MJ/m3. The mechanical properties of our synthetic silk fibers surpassed most previous recombinant protein fibers and even some natural spider silk fibers. The design strategy and the biosynthetic approach can be expanded to create numerous functional materials, enabling a wide range of mechanically demanding applications.

Microbial production of renewable fibers stronger and tougher than spider silk

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.