I’m starting with a somewhat enthusiastic overview of the role synthetic biology is playing in the world of clothing and cosmetics in The Scientist and following it up with some stories about fish leather, no synthetic biology involved but all of these stories are about sustainability and fashion and, in one case, cosmetics.

Fashionable synthetic biology

Meenakshi Prabhune’s June 14, 2024 article in The Scientist, in addition to the overview, provides information that explains how some of the work on textiles and leather is being used in the production of cosmetics. She starts with a little history/mythology and then launches into the synthetic biology efforts to produce silk and leather suitable for consumer use, Note: Links have been removed,

Once upon a time, circa 2700 BC in China, empress Xi Ling Shi was enjoying her afternoon tea under a mulberry tree, when a silkworm cocoon fell from the tree into her tea. She noticed that on contact with the hot beverage, the cocoon unraveled into a long silky thread. This happy accident inspired her to acquire these threads in abundance and fashion them into an elegant fabric. 

So goes the legend, according to the writings of Confucius, about the discovery of silk and the development of sericulture in ancient China. Although archaeological evidence from Chinese ruins dates the presence of silk to 8500 years ago, hinting that the royal discovery story was spun just like the silk fabric, one part of the legend rings true.¹ The Chinese royals played a pivotal role in popularizing silk as a symbol of status and wealth. By 130 BC, emperors in the Ancient Civilizations across the world desired to be clad in silken garments, paving the Silk Road that opened trade routes from China to the West. 

While silk maintained its high-society status over the next thousands of years, the demand for easy-to-use materials grew among mass consumers. In the early 20^th century, textile developers applied their new-found technological prowess to make synthetic materials: petrochemical-based polymer blended textiles with improved durability, strength, and convenience. 

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In their quest to make silk powerful again, not by status but rather by thread strength, scientists turned to an arachnoid. Dragline silk, the thread by which the spider hangs itself from the web, is one of the strongest fibers; its tensile strength—a measure of how much a polymer deforms when strained—is almost thrice that of silkworm silk.² 

Beyond durable fashion garments, tough silk fibers are coveted in parachutes, military protective gear, and automobile safety belts, among other applications, so scientists are keen to pull on these threads. While traditional silk production relies on sericulture, arachnophobes can relax: spider farms are not a thing.

“Spiders make very little silk and are quite territorial. So, the only way to do it is to make microbes that make the protein,” said David Breslauer, cofounder and chief technology officer at Bolt Threads, a bio apparel company. 

For decades, researchers have coaxed microbes into churning their metabolites in large fermentation tanks, which they have harvested to solve dire crises in many areas. For instance, when pharmaceuticals struggled to meet the growing demand for insulin through the traditional methods of extraction from animal pancreas, researchers at Genentech sought the aid of E. coli to generate recombinant insulin for mass production in 1978.³  [emphases mine]

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Prabhune’s June 14, 2024 article notes some difficulties with spider silk, Note: Links have been removed,

… researchers soon realized that producing spider silk in microbes was no easy feat. The spider silk protein, spidroin, is larger than 300 kDa in size—a huge jump from the small 6 kDa recombinant insulin. Bulky proteins impose a heavy metabolic load on the microbes and their production yield tanks. Also, spidroin consists of repeating regions of glycine and alanine amino acids that impart strength and elasticity to the material, but the host microbes struggle with protein folding and overexpression of the corresponding tRNA molecules.⁴  

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… researchers had gotten close, but they hadn’t been able to synthesize the full spidroin protein. Since the molecular weight of the silk protein correlates with the strength of the silk thread, Zhang [Fuzhong Zhang, a synthetic biologist at Washington University in St. Louis] was determined to produce the entire protein to mimic the silk’s natural properties.⁵

To achieve this goal without pushing the metabolic limits of the bacteria, Zhang and his team literally broke down the problem. In 2018, they devised a recombinant spidroin by constructing two protein halves with split inteins—peptides known to catalyze ligation between proteins while splicing out their own residues—tagged at their ends. They synthesized the halves in separate E. coli cultures, mixed the two cultures, and ligated the proteins to yielded a recombinant spidroin of 556 kDa—a size that was previously considered unobtainable.⁶ The resulting silk fiber made from these recombinant spidroins matched the mechanical properties of natural spider silk fiber.

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While synthesizing the high molecular weight protein validated their technical prowess and strategy, Zhang knew that the yield with this approach was going to be unavoidably low. “It was not even enough to make a simple shirt,” he said.

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Zhang and his team did solve the problem of getting a higher yield but that led to another problem, from Prabhune’s June 14, 2024 article,

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Breslauer echoed the importance of this step. He recalled how scaling up was the biggest challenge when he and his cofounder Dan Widmaier, chief executive officer at Bolt Threads, first set up shop in 2009. The duo met during their graduate studies. Breslauer, a material science student at the University of California, Berkeley, was fascinated by spider silk and sought help for synthesizing the protein in microbes. Luckily, he met Widmaier, a synthetic biology graduate student who was optimizing systems to study complex proteins.

When their collaboration to produce recombinant spider silk proteins in yeast yielded promising results, the duo decided to challenge the status quo in the textile industry by commercially producing bio-silk apparel, and Bolt Threads was born. The market transition, however, was not as smooth as the threads they produced. 

“There was so little innovation in the textile space, and brands were really eager to talk about innovation. It felt like there was demand there. Turns out, the desire for storytelling outweighed the desire for actual innovation with those brands,” Breslauer said. “We didn’t realize how adverse [sic] people were going to be to the idea because it was so unfamiliar.”

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Prabhune’s June 14, 2024 article also covers leather and cosmetics, Note: Links have been removed,

David Williamson, a chemist and the chief operations officer at Modern Meadow and his team wanted to separate themselves from the herd. In their quest for sustainable alternatives, they went back to the basic biology and chemistry of the material. As leather is made from animal skin, it is rich in collagen, a structural protein abundant in the extracellular matrix of connective tissues. If the team could produce this primary component protein at scale, they would be able to process it into leather downstream. 

In about 2017, Williamson and his team developed a fermentation-based approach to produce collagen from yeast. While they achieved scalable production, there was one small hiccup. The protein properties of collagen alone did not yield the mechanical properties they needed for their leather-like material. 

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The team went to the drawing board and analyzed the amino acid residues that contributed to collagen’s characteristics to look for a substitute protein. They found an alternative that had the desirable functional elements of collagen but was also sustainable and cost effective for industrial scale up: soy protein isolate. While tinkering with their recipes, they found the perfect combination for material strength by mixing in a bio-based polyurethane polymer with the protein to yield a refined bioalloy called Bio-VERA. 

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As natural textiles are derived from animal skin, hair, or proteins, it is no surprise that many synthetic biologists in the textile space have also found a niche in cosmetics. Even as the Modern Meadow team transitioned away from their protein fermentation strategies to innovate Bio-VERA, they realized that they could still apply their expertise in skincare. While leathery is not an adjective one desires to associate with skin, collagen is an integral component in both. “When our bodies make collagen and build our extracellular matrices, one of the first proteins that they deposit is type three collagen. So, you can think of type three collagen almost like the structure or scaffold of a building,” explained Williamson.

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To cater to the increasing demand for solutions to achieve younger looking skin, Williamson and his team engineered a recombinant collagen type three protein containing part of the protein sequence that is rich in binding domains for fibroblast interactions.^9,10  “After you expose the extracellular matrix to this protein, it stimulates the fibroblasts to make more type three collagen. That type three collagen lays down type one collagen and elastin and fibronectin in a way that actually helps to turn back time, so to speak, to increase the ratio of type three collagen relative to type one collagen,” Williamson said. 

The Modern Meadow team are not the only ones to weave their textile strands into cosmetic applications. When Artur Cavaco-Paulo, a biological engineer at the University of Minho [Portugal], was studying wool fibers, he was struck by their structural similarities to human hair. “We decided that it would be a really good idea to transfer some of the knowledge that we had in wool textiles to human hair,” said Cavaco-Paulo. Particularly, he was interested in investigating solutions to fix hair strands damaged by highly alkaline chemical products. 

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Over the next few years, Cavaco-Paulo developed […] shortlisted peptides into the K18 peptide product, which is now part of a commercially available leave-in conditioner. Cavaco-Paulo serves as the chief scientific officer at the biotech company K18. 

Although he started his career with textile research, Cavaco-Paulo favors the cosmetics sector with regards to returns on research and technology investment. “The personal care market is much more accustomed to innovation and has a much better and more fluid pipeline on innovation,” seconded Breslauer. “Whereas, [in] apparel, you really have to twist arms to get people to work with your material.” Bolt Threads ventured into the personal care space when Breslauer and his team serendipitously stumbled upon an alternative use for one of their textile proteins. 

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While it’s not mentioned in Prabhune’s June 14, 2024 article, sustainability is mentioned on two of the company websites,

Bolt Threads

Bolt Threads is a material solutions company. With nature as our inspiration, we invent cutting-edge materials for the fashion and beauty industries to put us on a path toward a more sustainable future.

Through innovative collaborations with world-class brands and supply chain partners, we are on a mission to create way better materials for a way better world. Join us.

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Modern Meadow

Modern Meadow is a climate-tech pioneer creating the future of materials through innovations in biology and material science.

​Our bio-materials technology platform with nature-inspired protein solutions delivers better performance, sustainability, scalability, and cost while reducing reliance on petrochemical and animal-based inputs.​

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K18 has not adopted a ‘sustainability’ approach to marketing its hair care products.

Sustainability without synthetic biology: fish leather

In a January 3, 2022 posting I featured fish leather/skin in a story about the “Futures exhibition/festival” held at the Smithsonian Institute from November 20, 2021 to July 6, 2022.

Before getting to Futures, here’s a brief excerpt from a June 11, 2021 Smithsonian Magazine exhibition preview article by Gia Yetikyel about one of the contributors, Elisa Palomino-Perez (Note: A link has been removed),

Elisa Palomino-Perez sheepishly admits to believing she was a mermaid as a child. Growing up in Cuenca, Spain in the 1970s and ‘80s, she practiced synchronized swimming and was deeply fascinated with fish. Now, the designer’s love for shiny fish scales and majestic oceans has evolved into an empowering mission, to challenge today’s fashion industry to be more sustainable, by using fish skin as a material.

Luxury fashion is no stranger to the artist, who has worked with designers like Christian Dior, John Galliano and Moschino in her 30-year career. For five seasons in the early 2000s, Palomino-Perez had her own fashion brand, inspired by Asian culture and full of color and embroidery. It was while heading a studio for Galliano in 2002 that she first encountered fish leather: a material made when the skin of tuna, cod, carp, catfish, salmon, sturgeon, tilapia or pirarucu gets stretched, dried and tanned.

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The history of using fish leather in fashion is a bit murky. The material does not preserve well in the archeological record, and it’s been often overlooked as a “poor person’s” material due to the abundance of fish as a resource. But Indigenous groups living on coasts and rivers from Alaska to Scandinavia to Asia have used fish leather for centuries. Icelandic fishing traditions can even be traced back to the ninth century. While assimilation policies, like banning native fishing rights, forced Indigenous groups to change their lifestyle, the use of fish skin is seeing a resurgence. Its rise in popularity in the world of sustainable fashion has led to an overdue reclamation of tradition for Indigenous peoples.

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Brendan Jones provides an update of sorts in his Alaska-forward take in his February 22, 2024 article “Fish Leather Is Incredibly Strong and Beautiful. Can Makers ‘Scale Up’? Meet artisans in Alaska and BC who are sustaining, and advancing, an ancient art.” for The Tyee,

Fish leather artist June Pardue began her journey into the craft not knowing where to start. Which was a problem, considering that she had been given the job of demonstrating for tourists how to tan fish skin at the Alaska Native Heritage Center in Anchorage. “I couldn’t find anyone to teach me,” Pardue said with a laugh.

“One day a guy from Mississippi noticed me fumbling around. He kindly waited until everyone had left. Then he said, ‘Do you want me to share my grandpappy’s recipe for tanning snake skins?’”

His cocktail of alcohol and glycerin allowed her to soften the skins — as tourists looked on — for future use in clothing and bags. This worked fine until she began to grow uncomfortable dumping toxins down the drain. Now she uses plant-based tannins like those found in willow branches after the season’s first snowmelt. She harvests the branches gingerly, allowing the trees to survive for the next generation of fish tanners.

Pardue, who teaches at the University of Alaska, was born on Kodiak Island, off the southern coast of the state, in Old Harbor village. Alutiiq and Iñupiaq, she was raised in Akhiok, population about 50, and Old Harbor.

Following her bumpy start at the heritage center, Pardue has since gone on to become one of Alaska’s and Canada’s most celebrated instructors and practitioners in the field of fish leather, lighting the way for others in Alaska and Canada.

Among the people Pardue has advised is CEO and founder of 7 Leagues tannery Tasha Nathanson, who is based in Vancouver. She met with Pardue to share her idea of creating a business built on making fish leather into boots and other items for a large customer base.

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Before making her move to open a business, Nathanson spent a year running the numbers, she said. In 2022, the global fish leather market was valued at US$36.22 million. As fish tanneries open their doors and fashion houses take notice, the number is expected to grow 16 per cent annually, topping $100 million by 2030.

“Salmon certainly don’t come to mind when you think of tanning, but people are catching on,” said Judith Lehmann, a Sitka-based expert in fish leather, who took Pardue’s class. (The Tyee reached Lehmann in Panama, where she was experimenting with skins of bonito and mahi mahi.)

Growing numbers of buyers are willing to pay for not only the beauty but also the remarkable durability fish leather can offer. California-based eco-fashion designer Hailey Harmon’s company Aitch Aitch sells the Amelia, a teal backpack made of panelled salmon leather, for $795.

One company in France has started to collect fish skins from restaurants — material that would otherwise end up in trash cans — to make luxury watch bands and accessories. Designers like Prada, Louis Vuitton and Christian Dior have incorporated fish leather into their lines. Even Nike introduced running shoes made of perch skin.

Whether they know it or not, today’s trendsetters are rooted in ancient history. “People have been working with fish skins for thousands of years,” Pardue said. “Ireland, Iceland, Norway, China, Japan — it’s an age-old practice.”

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“On a molecular level, fibres in fish leather are cross-hatched, as opposed to cow leather, which is just parallel,” Nathanson explained. “So, pound for pound, this leather is stronger, which is great for shoes. And it’s more available, and eco-conscious. It’s a win across the board.”

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Jones’s February 22, 2024 article has some wonderful embedded pictures and Beth Timmins’s May 1, 2019 article for the BBC (British Broadcasting Corporation), while a little dated, offers more information about the international scene.

Synthetic biology is a scientific practice that I find disconcerting at times. That said, I’m glad to see more work on sustainable products however they are derived. On that note I have a couple of recent stories:

• “Three century long development of a scientific idea: body armor made from silk” is the title of my July 11, 2024 posting
• “Grown from bacteria: plastic-free vegan leather that dyes itself” is the title of my June 26, 2024 posting

Enjoy!