In just fourteen days, an artificial leather shoe was grown from bacteria in a laboratory and programmed to paint itself black.
The plastic-free vegan creation was grown from genetically engineered microbes by researchers at Imperial College London (ICL).
It is the first time that bacteria have been designed to produce a material and its own pigment at the same time.
Researchers believe the process can be adapted to produce vegan materials with vibrant colors and even patterns, and to provide alternatives to fabrics such as cotton and cashmere.
Lead author Prof. Tom Ellis, from ICL's bioengineering department, said: "Inventing a new, faster way to produce sustainable, self-dyed leather alternatives is a major achievement for synthetic biology and sustainable fashion.
"Bacterial cellulose is naturally vegan and its growth requires a small portion of the CO2 emissions, water, land use and time required to raise cows for leather.
"Unlike plastic-based leather alternatives, bacterial cellulose can also be made without petrochemicals and will biodegrade safely and non-toxicly in the environment."
Manufacturers are trying to move away from synthetic chemical dyeing because it is toxic to the environment. The black dyes used to color leather are especially harmful.
The self-dyeing leather alternative was created by modifying the genes of a species of bacteria that produces sheets of microbial cellulose - a strong, flexible material already widely used in food, cosmetics and textiles.
Genetic modifications also "instructed" the same microbes that grew the material to produce a dark black pigment called eumelanin.
The cellulose was grown around a shoe-shaped mold to give it the shape of a traditional 'upper' and had taken the correct shape after 14 days.
To encourage the shoe to turn black, it was gently shaken at 30 °C (86 F) to activate the bacteria's production of black pigment, thus dyeing the material from the inside.
The story continues
The team, working with London biodesign company Modern Synthesis, also created a black wallet by growing two separate cellulose sheets, cutting them to size and sewing them together.
Co-author Dr Kenneth Walker, who carried out the work at ICL and now works in industry, said: "Our technique works on a large enough scale to create real products, as evidenced by our prototypes.
"From here we can consider aesthetics as well as alternative shapes, patterns, textiles and colours.
"The work also shows the impact that can occur when scientists and designers work together. As current and future users of new bacteria-grown textiles, designers play a key role in championing exciting new materials and providing expert feedback to improve form, function and the transition to sustainable fashion."
In addition to the prototypes, the researchers have shown that the bacterium can be manipulated using genes from other microbes to produce colors in response to blue light.
Colored proteins produced
By projecting a pattern or logo onto the sheets with blue light, the bacteria respond by producing colored proteins that then glow.
This allows them to project patterns and logos onto the bacterial cultures as the material grows, causing the designs to form from the material.
The research team is now experimenting with a variety of colored pigments to utilize the pigments that can also be produced by the material-growing microbes.
Professor Ellis added: "Microbes are already tackling many of the problems of animal-based leather and plastic directly, and we plan to prime them to expand into new colours, materials and perhaps patterns too.
"We look forward to working with the fashion industry to make the clothes we wear greener across the production line."
The research is being conducted in collaboration with Modern Synthesis, a London-based biodesign and materials company specializing in innovative microbial cellulose products. was published in the journal Nature Biotechnology.
Alternatives must be both desirable and green
By Stephen DoigThe rise of vegan and lab-grown alternatives isn't new, but it's encouraging that the movement is gaining momentum among established fashion brands and emerging companies. These new offerings are impressive because they cross scientific boundaries, but do they make you want to wear them?
It's a difficult subject; how to harness that all-important desire with a conscience in the way you make it. Stella McCartney is one of the most outspoken advocates of alternatives to both animal and synthetic materials, with her version of 'leather' coming from Mirum, a hard-wearing product made from natural rubber.
Our grandmothers wore fur
Livestock farming is responsible for 18 percent of global greenhouse gas emissions, and while much leather is a byproduct of agriculture, more sustainable methods are clearly needed. A forecast from a 2023 report predicts that cell-cultured leather is expected to grow from $4.05 million in sales in 2022 to $8.15 million in 2030. So there is clearly a movement - especially among the new generation of consumers - to way we make accessories such as shoes and bags.
Our grandmothers may have worn fur and (ethically questionable) diamonds, but their Generation Z descendants might be carrying backpacks filled with cultured bacteria (doesn't sound so glamorous, right?)
The self-dyeing element of this new vegan leather is an interesting development; The dyeing and tanning process usually involves chemical processes and a lot of water. Global brands such as Zegna, for example, focus on a natural dyeing process, using materials from local flora and fauna.
But there is also one a lot of greenwashing where brands claim to have created sustainable and ethical practices in finding alternatives to animal products - see the fuss surrounding faux fur being filled with toxic microplastics.
The aesthetic of ICL's prototypes may be a bit challenging - the shoe could almost be Rick Owens' Paris runway at the push of a button, but for the mainstream it's not exactly desirable. The sentiment, however, is noble. It's a step - no pun intended - in the right direction.
