Brewed Protein™ by Spiber: Fermentation to fashion
What if traditionally animal-derived materials could be made in an entirely different way?
For Stella McCartney, questioning convention has always been at the heart of design. Since founding the house in 2001, Stella has explored how innovation can challenge traditional approaches to luxury - from the materials used to the processes behind them.
For Winter 2026, this thinking continues through Brewed Protein™ by Spiber, a protein-based fibre developed through precision fermentation.
Rather than sourcing protein from animals, Spiber’s technology uses microorganisms in a controlled fermentation process to produce protein-based materials. It offers a fundamentally different approach to material creation, bringing together biotechnology and fashion to explore what fibres could look like beyond conventional production.
Stella McCartney and Spiber have been collaborating on material innovations for more than four years, developing and exploring how Brewed Protein™ can be expressed through the distinctive codes of the house.
For our most recent collection, the material appears in a series of ribbed constructions inspired by the fisherman knitwear of Stella’s Scottish upbringing. Familiar textures and silhouettes, including crewneck and shawl collared jumpers, are reinterpreted using a material developed through a radically different process.
The result brings together heritage and innovation - connecting a personal reference from Stella’s world with the possibilities of emerging material technology.
The fibre used in the Winter 2026 collection is exceptionally fine, measuring 12–14 microns in diameter. Its fineness contributes to a smooth, refined hand feel, giving the finished pieces a distinctive softness and tactile quality.
Behind that feel is a very different approach to production.
Precision fermentation allows proteins to be produced using microorganisms rather than relying on livestock farming. For fashion, this opens up new avenues for creating protein-based materials while reconsidering the systems traditionally used to make them.
The collaboration between Stella McCartney and Spiber is rooted in a shared ambition: to expand the possibilities of luxury beyond animal-derived materials.
For Stella, that ambition has been part of the house since its beginning. Being free from leather, feathers, fur and exotic skins is only one part of a wider philosophy – one that continually asks how design, science and innovation can work together to create better alternatives.
For Winter 2026, 93% of the collection is made from sustainable materials, with Brewed Protein™ joining a wider portfolio of innovative solutions being explored across the collection.
It is a reminder that the future of fashion may not simply be about using existing materials more responsibly, but about imagining entirely new ways to make them.
Brewed Protein™ by Spiber is one expression of that future – where biotechnology becomes part of the designer’s toolkit, and innovation becomes a material in its own right.
