Plastics are the king of industrial materials, and even the biological field is dedicated to developing almost imaginable plant replicas. However, plastic is not the only industry all-rounder that bio-based producers should be looking at. Protein fibers nearly rival it in the range of applications and even surpass it in some areas, balancing strength and flexibility with a potentially lower environmental impact.
Common examples of protein fibers are wool, fur, silk, keratin, collagen and elastin, many of which have been used in the past as currency, hunting bowstrings, paper, textiles and wound dressings. Today, protein fibers are mainly used in clothing and cosmetics, but gene-editing technology is opening up a wider range of applications.
What is protein fiber?
Like plastics, proteins are polymers called polyamides. All proteins are made up of repeating amino acid units, and different arrangements of amino acid units lead to very different properties. Some proteins may be hard and brittle, but with some processing they can gain elasticity and strength. This rare combination is useful in applications where the material must withstand high impact stresses and heavy loads while being yielding and flexible.
Natural proteins need to be processed before they are suitable for special applications. State-of-the-art methods to enhance protein fiber production are at the intersection of gene editing and fermentation production.
Does protein fiber have to come from animals?
Most of the everyday protein fibers we encounter come from farmed animals, such as wool from lambs or silk from cocoons.
But plants can also be a source of protein fibers. ABrand Technology Company has been making plant protein fibers from proteins.CoatsKnit Eco S makes a smooth, drapey apparel textile from protein fibers made from byproducts of soybean production.
What are the advantages of sustainability?
The relative sustainability of different materials is highly correlated, but protein fibers tend to have an advantage over bioplastics in one area: biodegradability. Protein fiber textiles are biodegradable, fully recyclable and do not break down into microplastics.
This marks the difference between bioplastics and petroleum-based plastics at the molecular level. This means they are generally unable to disrupt security in the natural environment - a problem given the huge gaps in global recycling infrastructure.
There are also savings associated with land use. Newer lab-produced protein fibers involve organisms, but are much smaller and less resource-intensive than sheep microbes.
Spiber, a Japanese textile materials company, was founded in 2007 to produce brewer's protein using specialized microorganisms. Brewer's protein is a laboratory-produced protein fiber that falls somewhere between a natural substance and a man-made substance.
The gene-edited protein fiber materials offer sustainability advantages over traditional protein fibers, such as wool, as they do not require an animal source, only an initial tissue sample. This eliminates the need for carbon- and land-intensive herds and could mean that lab-produced protein fibers achieve a lighter ecological footprint.
Another benefit is that the potential applications for protein fibers are expanding as a result of gene editing, allowing them to take on new applications that unmodified proteins cannot. This means they may replace the use of bio-based and oil-based plastics in an increasing number of areas.
Spieber fermented spider silk
The most talked about protein fiber in the startup world today is spider silk and its laboratory variants.
Spider silk has been chosen as one of the strongest materials on a weight basis due to its industry potential. It is also flexible and can be used in functional apparel applications such as ballistic protective gear and outdoor clothing, where petrochemical fibers currently dominate.
However this material is difficult to obtain simply from natural resources. Unlike silkworms, spiders are too aggressive for swarming and farming. Japanese startup Spiber has solved the problem of sourcing spider silk with its line of gene-edited bacteria.
But Spieber went further than simply copying naturally occurring materials. Through gene editing, they improved the function of spider silk, producing a protein fiber never before found in nature. The trademarked name is Brewing Protein for the Raw Materials Market.
Spieber altered the genes responsible for spider silk production so that they encoded a slightly optimized form of spider silk that was more suitable for human use - in their case, clothing.
This altered protein-coding DNA is then inserted into Spieber's manufacturing bacteria, which replicate this material on a large scale in vivo, ready for extraction and processing.
The company also claims that its genetically modified spider silk is even better than silk quilts in terms of ecological footprint because it avoids the alkali and other chemicals used in processing.
Fermentation is often a more environmentally friendly way to produce bio-based materials than farmed mammals that require food, water and land.
Spiber's success in securing $68 million in funding in April 2024 reflects a huge vote of confidence from the textile industry, despite a general downturn in venture capital funding for the startup. This reflects the huge demand in the apparel industry for materials that meet a number of criteria that conscious consumers adhere to:sustainability, animal ethics, and functionality.
Customized Protein
As a synthetic protein fiber company, Spiber gets the most attention, but the other two big players are German biotech companies Brain Biotech and AMSilk.
These German silk startups began working together in 2023 to develop new functional materials using computer-aided design and laboratory testing. One year on, the venture filed its first patent application for registration.
Like Spieber, this collaboration is aimed at apparel. However, it has a broader focus on the manufacture of protein fiber materials for other high-specification “high-performance” applications such as medical and automotive interiors.
Brain's role in the partnership focuses on their synbio software platform, which enables researchers to more systematically design and develop new protein variants.Brain uses artificial intelligence predictions and computer modeling to learn which genetic modifications produce specific results that contribute to industrially functional biomaterials.
Using these tools, the company systematically adapted the amino acid building blocks of the silk proteins in their library. After testing these modified proteins in the lab, they gave the best performing proteins to AMSilk for textile prototyping.
While Brain designs the raw materials, Munich-based, customer-oriented AMSilk produces and sells practical textiles. Similar to Spiber, AMSilk's approach to protein manufacturing is sophisticated fermentation: the company lets bacteria “copy” the proteins Brain develops and reproduce them in large quantities.
Ansell is in the process of scaling up its production lines to improve efficiency. It aims to increase its precision fermentation output from “kilograms” to “tons” and hopes to support this through a partnership with Danish company 21st.Bio earlier this year.
Beyond Clothing
To date, protein innovations have been targeted at the apparel market. The feed-through between new protein fiber startups and the apparel industry is not surprising: fashion multinationals have the wealth to support emerging biomaterials, which are still expensive to produce at scale.
However, protein fibers have a wider range of end uses. These include elastin and dendrin, which are commonly found in mammals and insects and are at least five times more elastic than rubber hands.
Launch Smart Resin utilizes genetic engineering to produce an elastin additive powder that is “incorporated” into the manufacturing process of goods that require durability and a certain degree of elasticity, such as athletic shoe soles.
Keratin is another protein commonly associated with the cosmetics industry as a conditioner for damaged hair, skin and nails. However, European startup Edge Line is bringing the chemical into areas where industrial flame retardants are difficult to decarbonize.
Kerline produces FullKer, a protein-based flame retardant that replaces traditional antimony trioxide, a highly toxic substance.Kerlin makes the additive from keratin extracted from animal proteins recovered from waste in the agri-food and textile industries, which also makes it a recycling technology.
Scientists are also investigating how protein fibers can replace fossil polymers as materials for separation membranes. They have also been proposed as polymer replacements for ropes, nets, seat belts, etc.
There could be technological spillover between protein startups targeting clothing and those targeting materials for industrial use. Improvements in protein gene editing technology by startups like Spiber mean more powerful tools for discovering novel protein arrangements in the future.
