Plastic-free vegan leather shoe grown from bacteria in 14 days

A faux-leather shoe has been grown from bacteria in a lab in just 14 days and programmed to dye itself black.

The plastic-free vegan creation was cultivated by researchers at Imperial College London (ICL) from genetically engineered microbes.

It is the first time bacteria have been designed to produce a material and its own pigment simultaneously.

Researchers believe the process could be adapted to produce vegan materials with vibrant colours and even patterns, and to offer alternatives to fabrics such as cotton and cashmere.

Lead author Prof Tom Ellis, from ICL’s department of bioengineering, 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 inherently vegan, and its growth requires a tiny fraction of the carbon emissions, water, land use and time of farming cows for leather.

“Unlike plastic-based leather alternatives, bacterial cellulose can also be made without petrochemicals, and will biodegrade safely and non-toxically in the environment.”

Manufacturers are trying to move away from synthetic chemical dyeing because it is environmentally toxic. The black dyes which are used to colour leather are particularly harmful.

The self-dyeing leather alternative was created by modifying the genes of a bacteria species that produces sheets of microbial cellulose – a strong, flexible material that is already commonly used in food, cosmetics and textiles.

Genetic modifications “instructed” the same microbes that were growing the material to also produce a dark black pigment called eumelanin.

The cellulose was grown around a shoe-shaped mould to give it the shape of a traditional ‘upper’ and after 14 days had taken on the correct shape.

To encourage the shoe to turn black, it was subjected to gentle shaking at 30C (86F) to activate the production of black pigment from the bacteria so that it dyed the material from the inside.

The team, who worked with the London-based biodesign company Modern Synthesis, also made a black wallet by growing two separate cellulose sheets, cutting them to size and sewing them together.

Co-author Dr Kenneth Walker, who conducted the work at ICL and now works in industry, said: “Our technique works at large enough scales to create real-life products, as shown 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 happen when scientists and designers work together. As current and future users of new bacteria-grown textiles, designers have a key role in championing exciting new materials and giving expert feedback to improve form, function and the switch to sustainable fashion.”

As well as the prototypes, the researchers demonstrated that the bacteria can be engineered using genes from other microbes to produce colours in response to blue light.

Produced coloured proteins

By projecting a pattern, or logo, onto the sheets using blue light, the bacteria respond by producing coloured proteins which then glow.

This allows them to project patterns and logos onto the bacterial cultures as the material grows, resulting in the designs forming from within the material.

The research team is now experimenting with a variety of coloured pigments to use those that can also be produced by the material-growing microbes.

Prof Ellis added: “Microbes are already directly addressing many of the problems of animal and plastic-based leather, and we plan to get them ready to expand into new colours, materials and maybe patterns too.

“We look forward to working with the fashion industry to make the clothes we wear greener throughout the whole production line.”

The research, carried out alongside Modern Synthesis, a London-based biodesign and materials company which specialises in innovative microbial cellulose products. was published in the journal Nature Biotechnology.

Alternatives need to be desirable as well as green

By Stephen Doig

The rise of vegan and lab grown alternatives isn’t new but it’s encouraging that the movement is gathering pace among established fashion brands and emerging businesses. These new offerings are impressive in their scientific boundary breaking but do they make you want to wear them?

It’s a tricky subject; how to harness that all-important covetability with a conscience in how you make it. Stella McCartney has been one of the most vocal advocates of alternatives to both animal-derived and synthetic materials with her version of “leather” coming from Mirum, a hard-wearing product made from natural rubber.

Our grandmothers were in furs

Animal agriculture causes 18 per cent of the world’s greenhouse gas emissions, and while a great deal of leather is a byproduct of farming, clearly more sustainable methods are sorely needed. A forecast from a 2023 report predicts that cell-cultured leather is expected to expand from a $4.05 million business in 2022 to $8.15 million by 2030, so clearly there’s a movement – particularly among the new generation of consumers – to evolve how we create accessories such as shoes and bags.

Our grandmothers might have been in furs and (ethically questionable) diamonds, but their Gen Z descendants may well be in cultured bacteria backpacks (doesn’t sound quite as glamorous, does it?)

The self-dyeing element of this new vegan leather is an interesting development; the dyeing and tanning process usually involves chemical processes and a great deal of water. Global brands such as Zegna, for example, focus on a natural dyeing process, harnessing materials from local flora and fauna,.

But there’s also a great deal of greenwashing where brands claim to have created sustainable and ethical practices in finding alternatives to animal products – see the furore around fake fur being filled with toxic microplastics.

The aesthetics of the prototypes from ICL might be a little challenging – the shoe could almost be knock-off Rick Owens Paris catwalk at a push but it’s not exactly desirable to the mainstream . However, the sentiment is a noble one. It’s a step – no pun intended – in the right direction.