Microbes are already grown to make sustainable textiles or dyes for industry, but the breakthrough at Imperial marks the first time bacteria have been engineered to produce a material and its own pigment simultaneously.
The researchers said their self-dyeing vegan, plastic-free leather is a step forward for more sustainable fashion. Their findings are detailed in Nature Biotechnology.
The new process could also theoretically be adapted to have bacteria grow materials with various vibrant colours and patterns, and to make more sustainable alternatives to other textiles such as cotton and cashmere.
In a statement, lead author Professor Tom Ellis, from Imperial College London’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.”
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With funding from the Engineering and Physical Sciences Research Council and BBSRC, the researchers created the self-dyeing leather alternative by modifying the genes of a bacteria species that produces sheets of microbial cellulose. The genetic modifications 'instructed’ the same microbes that were growing the material to also produce the dark black pigment, eumelanin.
They worked with designers to grow the upper part of a shoe (without the sole) by growing a sheet of bacterial cellulose in a bespoke, shoe-shaped vessel. After 14 days of growth wherein the cellulose took on the correct shape, they subjected the shoe to two days of gentle shaking at 30°C to activate the production of black pigment from the bacteria so that it dyed the material from the inside.
They also made a black wallet by growing two separate cellulose sheets, cutting them to size, and sewing them together.
As well as these prototypes, the researchers demonstrated that the bacteria can be engineered using genes from other microbes to produce colours in response to blue light. 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 patterns and logos forming from within the material.
Co-author Dr Kenneth Walker, who conducted the work at Imperial College London’s Department of Bioengineering 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.”
The researchers are now experimenting with a variety of coloured pigments to use those that can also be produced by the material-growing microbes.
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