Second nature
Emulating the properties of a squid’s suction cups or, more prosaically, those of wool, two new biotech protein fibres are in the works at Tandem Repeat. What began in a biomimetic materials lab at Penn State University is now close to being ready for market.
The array of protein fibres derived from fermentation stands to grow significantly when, and if, all ongoing research and pilot projects come to market. Three such fibres are at a relatively advanced stage of readiness. Some have already launched commercially.
Spiber’s aptly named Brewed Protein Fiber has woven its way into the collections of high-end mills and brands. The Japanese company, founded in 2007, has been operating an industrial fermentation plant in Thailand since 2021. Another pioneer in the field is AMSilk, a German company founded in 2008. Last year, it exhibited its first yarn and fabric samples at Pitti Filati and Première Vision. The third company, Tandem Repeat, was incorporated in 2020 by Melik Demirel, a professor at Penn State University. This spring, to test the market, he launched a short production run of sweaters made from Procell, a yeast-brewed protein fibre, under the Sonachic label.
Early attempts to make manmade protein fibres, as alternatives to natural silk and wool, which are also protein fibres, date back to the late 19th century and the work of a Scottish inventor, Adam Millar, on gelatine-based fibres, as Melik Demirel tells Sportstextiles.
Further research in this field led to the development of protein fibres derived from milk casein in the 1930s (Lanital and, later, Merinova), and from soybean or even peanuts in the 1940s. “All these fibres were made from animal or vegetal proteins, but they were mechanically weak and expensive to make. When polyester came around, it took over the market,” he says.
Building on this heritage, Prof Demirel first began studying squid, and specifically the teeth around its suction cups whose properties, including the ability to self-heal, he believes can offer promising possibilities for advanced materials. The DNA of this protein was integrated into bacteria and reproduced using precision fermentation. Research on the Squitex fibre is ongoing, notably for military applications, but the researcher decided to shift his focus to a less costly fermentation method using yeast and biomass.
“Biomass fermentation is significantly cheaper than precision fermentation,” he says. Yeast can be fed biomass waste from the brewing and biomanufacturing sectors, particularly the pharmaceutical industry. He explains that this by-product cannot be sold as animal feed if it comes from pharmaceuticals and is usually destroyed. “This makes our raw material nearly free,” he tells Sportstextiles.
The fermentation process produces protein in powder form that can be turned into pulp and made into filaments using a wet-spinning process, like that used for lyocell. The protein fibre, named Procell, is then cut into a staple yarn for knitting, weaving or nonwovens. It can be blended with any other fibre, including cotton, wool or polyester. The biomaterial yarn, he says, has twice the strength of wool and costs half the price. “Today, at lab scale, we can easily beat the price of wool. In the long run, we could even beat the price of cotton,” he says. Procell could thus be one of the rare next-gen biotech fibres to break the cost barrier.
Tandem Repeat produced 500kg of Procell in 2024 and has plans to increase this to 10 tonnes during 2025. Initial production was done at a pilot-scale plant at the Thuringian Institute for Textiles & Plastics Research (TITK) in Germany. The company is now working with a European lyocell producer to increase production to 300 tonnes in 2026. Procell yarns and fabrics are currently made in Turkey.
Like Spiber’s Brewed Protein Fiber, Procell is naturally golden in colour, but it can be dyed. The hand-feel of the first fabrics varies with staple lengths, notes the founder. “A fabric made from 80 mm staple fibres feel like wool, while those made from 38 mm fibres feel more like cotton.”
Producing fibres from fermentation is said to be less taxing on the environment, as it does not require land, as wool does, or mulberry plantations, as silk does. The biomaterial is biodegradable, with the advantage of being customisable to deliver various properties.
Tandem Repeat has filed more than 20 patents for its technology and processes. Compared to other biotech start-ups, it has received moderate levels of funding, $2 million in venture capital and $6.8 million in grants.
Testing the market
Tandem Repeat is in talks with brands to bring Procell to market, but the apparel industry’s long lead-times, and non-disclosure agreements, inspired the university professor to test the market directly, even if on a small scale. Earlier this year, a short run of 50 sweaters made from a blend of 50% Procell and 50% wool was produced and sold online under the Sonachic label. The test was positive, he tells Sportstextiles, but selling one item at a time is slow, and he is looking for a wholesaler to increase volumes and raise revenue to support the company through the long process of brand adoption.
In addition to yarns and fabrics, the company is also developing thermal insulation padding, a project for military applications. “The United States does not produce much wool, and polyester fillers will melt and drip when exposed to high temperatures. This is a major issue for military personnel,” he notes. Procell will not melt, has high thermal properties, and could thus be a better solution.
The US department of defence is also interested in the self-healing properties of Squitex. “It possesses active thermoregulating properties” when coated or integrated into a Procell fibre, says Prof Demirel. “As you sweat, it changes the thermal properties of the fibre, and this is unique,” he adds, referencing a paper he authored that was published in Nature. The Squitex coating could be applied to any fibre, he says.
Tandem Repeat was awarded $1.5 million by the Biden administration’s Climate Positive programme to build a factory in North Carolina, a project that is awaiting approval by the Trump administration. For this project, the Tandem Repeat team prepared a document outlining the infrastructure and engineering requirements for a future factory. “We have detailed all necessary information on machinery needs and processing, including lifecycle analysis data. A factory could be built in Canada, Taiwan, Germany, Turkey or Vietnam, anywhere really, and ideally in all of these countries,” he says. Funding is needed for this to happen, and he believes private-equity capital could be raised to build the first facility, before licensing the technology to interested parties.
There is a market for Procell, he insists, pointing to the evolution of wool production over the years. “There was a time when 2 million tonnes of wool were produced yearly. It has since fallen to 1 million tonnes, and is not evolving. I am not looking to take wool’s market share but to retrieve the 1 million tonnes that wool has lost over the years,” he insists.
Taking the long view, he observes that it was millennia ago that humans started to domesticate silkworms for silk and rear sheep to produce wool from the fleeces. The domestication of yeast to make bread or beer also goes way back. Now, he says, we can domesticate yeast to make fibres.
A short run of sweaters, made in a blend of 50% Procell and 50% wool was launched earlier this year to test market acceptance.
Credit: Sonachic / Tandem Repeat
