Fungi-based textile startup Hydefy makes its debut through a vegan fungi leather bag with Stella McCartney, bringing biotech-driven materials into luxury’s commercial conversation.
Fungi-derived textiles have been steadily gaining ground in the fashion industry, but few have made the leap from innovation pipeline to high-end product with commercial viability. Hydefy, a materials brand developed by the Fynder Group, is attempting to close that gap — and its first move is a notable one.
Unveiled during Stella McCartney’s Spring/Summer 2025 show, the brand’s launch centers on a collaboration that introduces Hydefy’s first product in the form of McCartney’s iconic Stella Ryder bag in metallic silver. The bag features a sculpted shape inspired by a horse’s back and marks what the brand calls McCartney’s “most elevated vegan bag to date.” It is now available for pre-order through the designer’s website.
“I am constantly exploring plant and fungi-based, regenerative alternatives that do not harm animals and heal Mother Earth,” said McCartney in a statement. “Harmonious to this philosophy, the innovators behind Hydefy are developing materials with fresh thinking and a focus on sustainability.”
Hydefy enters a growing field of startups working with mycelium — the root-like structure of fungi — as a base for leather-like materials. Companies including MycoWorks and Bolt Threads have attracted attention from major brands like Hermès and Stella McCartney herself. But supply constraints and high costs have kept many such materials from scaling, despite demand from brands for more sustainable options.
The global mycelium market is projected to grow from $3.1 billion in 2023 to more than $6.5 billion by 2032, according to Straits Research, with applications spanning fashion, packaging, construction, and food. Within fashion, interest in mycelium is driven by its potential to replace resource-intensive materials like leather, which contributes an estimated 130 million tons of CO2-equivalent emissions per year, according to the United Nations Food and Agriculture Organization.
Hydefy’s distinguishing feature is its use of Fy — a proprietary material derived from fungi discovered during NASA-backed research in Yellowstone National Park. The company combines the fungi with sugarcane waste through a fermentation process, resulting in a flexible, high-strength textile designed for use across industries.
“Hydefy isn’t just another alternative — it’s the future of high-performance textiles,” said Thomas Jonas, co-founder and CEO of the Fynder Group. “We’re proving that innovative materials can meet the highest standards of durability, quality, and aesthetics — offering designers new creative possibilities with a lower impact. This is a game-changer for industries that have long relied on resource-intensive, outdated materials.”
In addition to fashion, the company is targeting sectors like automotive and interiors, aiming to expand its reach beyond runway moments. Its material can be customized for color, texture, and finish, and the team offers rapid prototyping to support designers during the development phase.
The strategic debut with Stella McCartney suggests Hydefy is positioning itself not just as a biotech innovation but as a viable option for luxury applications. The bag’s commercial availability also sets it apart from other mycelium innovations that remain in limited release.
For McCartney, the partnership reinforces her long-standing interest in new materials and her refusal to use animal leather, feathers, fur, or skins in any of her products. In 2022, she previewed a Mylo mycelium-based bag developed with Bolt Threads, with limited supplies. Hydefy’s entry now fills a gap left by that material’s stall in production, offering McCartney and her customers a functional alternative with market-ready supply.
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