Recombinant Silk Fiber Composition for Microfiber-Scale Production
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Solution Overview
Problem
Current methods for producing recombinant silk fibers are not commercially scalable and do not achieve the small diameters necessary for microfiber textiles, lacking the flexibility, strength, and other properties of natural silk fibers.
Innovation Solution
Development of proteinaceous block co-polymers with specific amino acid compositions and domain lengths, secreted by engineered microorganisms such as Pichia pastoris or Bacillus subtilis, to produce fibers with diameters suitable for microfiber textiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If recombinant silk fibers are produced using current methods in microorganisms, then production can be achieved at lab and bioprocessing scale, but the fibers do not achieve small diameters necessary for microfiber textiles and lack commercial scalability
Solution Approach 1:
The patent applies parameter changes by modifying the amino acid sequence parameters of the silk polypeptide, specifically incorporating repeat domains with defined lengths (e.g., 1-10 repeats of 15-50 amino acids each) and controlled amino acid compositions (glycine 20-40%, alanine 10-30%, proline 5-20%). These parameter adjustments enable the production of fibers with diameters of 4.48-12.7 μm suitable for microfiber textiles while maintaining commercial scalability through microbial expression systems.
2Ease of manufacture
If silk polypeptides are produced as fragments of native repeat domains, then production is achievable, but the fibers lack the flexibility, strength, and other properties of natural silk fibers
Solution Approach 1:
The patent applies segmentation by dividing the silk polypeptide into distinct functional domains: N-terminal non-repetitive domain (providing aqueous stability and secretion signals), repeat domains (providing structural strength through crystalline and amorphous regions), and C-terminal non-repetitive domain (providing pH sensitivity and molecular alignment). This segmented architecture enables both ease of manufacture through modular genetic construction and superior mechanical properties by preserving the functional integrity of each domain.
Solution Approach 2:
The patent applies composite materials principles by creating a multi-domain polypeptide structure that combines different functional elements: hydrophilic N-terminal domain for stability, hydrophobic repeat domains for strength, and pH-sensitive C-terminal domain for processing. This composite architecture replicates the complexity of natural silk while enabling controlled production and superior fiber properties including flexibility and strength.
3Productivity
If intracellular expression and purification methods are used, then silk polypeptides can be produced, but the process requires chromatography or bulk precipitation that does not lead to viable commercial scalability
Solution Approach 1:
The patent applies the extraction principle by removing the N-terminal secretion signal sequence from the expressed polypeptide to enable secretion of the silk fiber protein into the extracellular medium. This allows the product to be extracted directly from culture supernatant through simple filtration and concentration, eliminating the need for complex intracellular purification steps such as chromatography or bulk precipitation, thereby enabling viable commercial scalability.
Data Source
AI summary
The present disclosure provides methods and compositions for directed to synthetic block copolymer proteins, expression constructs for their secretion, recombinant microorganisms for their production, and synthetic fibers (including advantageously, microfibers) comprising these proteins that recapitulate many properties of natural silk. The recombinant microorganisms can be used for the commercial production of silk-like fibers.