Researchers at Imperial College London have genetically engineered bacteria to grow animal- and plastic-free leather that dyes itself.

Leather alternatives grown by bacteria is an up and coming research field to provide more sustainable textiles. The production process uses only a fraction of the carbon emissions, water, land use and time compared to animal leather. Unlike plastic-based leather alternatives, the bacterial leather can be made without petrochemicals and will biodegrade without harming the environment.

However, this still leaves the problem of dyeing. Synthetic chemical dyeing is one of the most environmentally toxic processes in fashion, and black dyes, especially those used in colouring leather, are particularly harmful.

To counter the dyeing problem, the researchers modified 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 material designer Jen Keane, who also works with bacterial cellulose (read more about her projects here) to grow the upper part of a shoe. After 14 days of growth in which 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.

In addition, the bacteria can be engineered to produce colours in response to blue light. By projecting a pattern onto the sheets of bacterial cellulose, the bacteria produced coloured proteins. 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.

Photos: Imperial College London