Synthetic Biology Yields Protein Fibers That Dissolve and Reform, Offering a Recyclable Alternative to Synthetic Textiles
WashU engineers used synthetic biology to create SAM — a protein fiber combining mussel, spider silk, and amyloid sequences — that dissolves in formic acid within seconds and can be remade into equally strong fibers across multiple recycling cycles.
Overview
Engineers at Washington University in St. Louis have used synthetic biology to create a protein-based textile fiber that dissolves completely in a formic acid solution within seconds and can be reconstituted into new fibers with equivalent strength — an approach that addresses a persistent problem in the textile industry, where less than 12 percent of fiber materials are currently recycled.
The material, named SAM — short for Silk-Amyloid-Mussel — is produced by genetically modified microbes in bioreactors and was described in a study published in Advanced Materials by Jingyao Li, Juya Jeon, Kok Zhi Lee, and Fuzhong Zhang of McKelvey School of Engineering. The research was announced on May 8, 2026, according to WashU McKelvey School of Engineering.
What We Know
The SAM fiber is built by combining protein sequences from three biological sources, each contributing a distinct function. Mussel foot protein sequences control the material’s solubility in formic acid and prevent it from shrinking when wet. Spider silk and amyloid protein sequences supply tensile strength and ensure the polymer chains reconnect robustly after the material is dissolved and reformed. The combination allows researchers to tune the fiber’s recyclability and mechanical performance independently, as WashU McKelvey School of Engineering reported.
Fuzhong Zhang, Francis F. Ahmann Professor in the Department of Energy, Environmental and Chemical Engineering and co-director of WashU’s Synthetic Biology Manufacturing of Advanced Materials Research Center (SMARC), described the core finding: “We engineered recyclable protein fibers that dissolve in a formic acid solution within seconds, yet remain stable in water and strong after drying.”
The recycling mechanism relies on formic acid acting as a solvent that temporarily disrupts the protein interactions holding the fibers together without chemically altering the proteins themselves, according to The Source at WashU. Once the solvent evaporates, the raw proteins are recovered and can be respun into new fibers that retain their original properties. The team demonstrated this process across multiple rounds, and Zhang noted: “Recycling the final product multiple rounds can greatly reduce manufacturing costs over time.”
Beyond fiber-to-fiber recycling, the recovered proteins can also be reformulated into adhesive hydrogels, which are themselves recyclable back into fibers or further hydrogel products, according to WashU McKelvey School of Engineering.
The Microplastics Problem
One of the persistent environmental drawbacks of conventional synthetic textiles — nylon, polyester, and similar petrochemical-derived materials — is that they shed microscopic polymer particles during washing. These microplastics accumulate in aquatic environments and are difficult to remove. Because SAM is a protein-based material produced from biological sequences, any microparticles shed during washing would biodegrade rather than persist as synthetic microplastics, as described by The Source at WashU.
What We Don’t Know
The research has not yet disclosed the number of recycling cycles that were tested before performance degraded. No tensile strength figures were published in the accessible press materials, making a direct quantitative comparison to nylon, wool, or polyester unavailable. The study also does not address the commercial cost or scalability of producing SAM fibers at the volumes needed for industrial textile manufacturing, and it remains unclear how the formic acid used in recycling would be handled or recovered at scale.
Analysis
The SAM protein represents an application of synthetic biology that moves beyond the laboratory and into a domain — the textile industry — where biological materials have historically been restricted to natural fibers such as wool, cotton, and silk. By combining sequences from three different organisms into a single engineered protein and producing it in bioreactors, the research demonstrates that protein properties can be modularly tuned: stickiness for recyclability from mussels, strength from spider silk, and structural reconfigurability from amyloids.
Zhang specifically noted the ability to tune the mussel foot sequences to control recyclability while preventing shrinkage: “We tune the mussel foot sequences to make SAM fibers recyclable while preventing them from shrinking when they get wet.” That level of sequence-level control over macroscale material behavior is a signature of the synthetic biology approach, and it suggests a pathway for designing other protein-based materials with independently optimized properties.
The textile waste problem is substantial. With only 12 percent of fiber materials currently recycled, as reported by WashU McKelvey School of Engineering, the industry generates significant landfill and incineration waste, and the microplastics shed by synthetic fibers represent a growing ecological concern. A protein-based fiber that can be dissolved and reformed without loss of mechanical integrity — and whose shed particles biodegrade — would address both waste streams simultaneously.
The research was funded by the U.S. Department of Agriculture, the National Science Foundation, and the National Institutes of Health.