Protein-based textile fibres that dissolve in formic acid solution and reform into fibres of equivalent strength have been developed using genetically engineered microbes. Any microparticles shed during washing are biodegradable, unlike synthetic fibres, which release persistent microplastics into aquatic environments throughout their life cycle. The material can be remade across multiple cycles without loss of strength or properties.
- Only about 12 per cent of textile fibre materials currently enter recycling, and most petrochemical-based fibres continue releasing persistent microplastics across their full life cycle.
- The material, called SAM (a silk-amyloid-mussel protein hybrid), combines genetic sequences from mussel foot proteins, spider silk and amyloid proteins, with each component independently controlling strength and recyclability.
- The spider silk and amyloid sequences within SAM form strong interactions that reconnect the polymer chains after each dissolution cycle, restoring the material to its original properties.
- The findings, by Jingyao Li et al, have been published in 'Biosynthesized Silk-Amyloid-Mussel Proteins as Dissolution Recyclable Materials With Tunable Supercontraction' in Advanced Materials.
HOW IT WAS BUILT: The SAM material was developed in the lab of Fuzhong Zhang, Francis F. Ahmann Professor in the Department of Energy, Environmental and Chemical Engineering at the McKelvey School of Engineering, Washington University in St Louis, and co-director of the Synthetic Biology Manufacturing of Advanced Materials Research Centre (SMARC). The protein-based materials are produced in bioreactors using genetically engineered microbes.
- SAM is a silk-amyloid-mussel protein hybrid, constructed by combining genetic sequences from mussel foot proteins, spider silk and amyloid protein aggregations.
- Protein engineering techniques were used to knit these sequences together so that the strength and recyclability of the resulting material could be independently controlled.
- Conventional recycling either produces weaker plastics due to additives and contaminants, or breaks chemical bonds through resynthesis, adding greatly to costs and emissions. In general, the stronger a material, the harder it is to recycle.
- Formic acid solution, the solvent used to dissolve SAM fibres, is an affordable, volatile industrial solvent already used in leather processing, textile dyeing, animal feed preservation and cleaning.
- When formic acid breaks down the protein interactions binding the fibre, the protein itself remains unchanged, allowing raw materials to be recovered through solvent evaporation and reused.
PUTTING IT TO THE TEST: SAM fibres have been dissolved and remade across multiple cycles, producing consistent high strength each time. The mussel foot protein sequences in SAM are tuned to control dissolution behaviour while preventing the fibres from shrinking when wet. Recycled raw proteins from SAM can also be repurposed into adhesive hydrogels, which can themselves be further recycled back into fibres or hydrogels.
- SAM fibres dissolve in formic acid within seconds and, after solvent evaporation, the recovered proteins reform into fibres that match the performance of the original material.
- The spider silk and amyloid sequences ensure strong interactions that reconnect the polymer chains after each recycling cycle, restoring the material to its original strength and properties.
- Recovered proteins can also be repurposed to produce adhesive hydrogels for various applications, which can themselves be further recycled into fibres or hydrogels.
- Biomanufacturing has historically been too costly for mainstream use, limiting researchers to luxury applications, but with a circular system of resources, costs start to drastically lower across successive production rounds.
