Coloured artificial leather invented, with both the leather and the colour created by bacteria

Artificial leather, sometimes referred to as faux or vegan leather is changing. Many artificial leathers are based on artificial polymers such as PVC and polyurethane, meaning that lots of artificial leather is nowhere near as sustainable or environmentally friendly as might be hoped because of the chemicals involved in making these polymers and the difficulty in degrading/recycling them. There have been many developments in recent years in artificial leather, including making use of plant/food waste, from feedstocks as diverse as banana crop waste and spent coffee grounds. However, these materials to do not come without disadvantages. In particular, significant effort is often necessary to turn these into useful materials, involving use of large amounts of chemicals and energy.

One of the most exciting developments in recent years has been the harnessing of the power of bacteria to develop new artificial leather, often based on the naturally strong polymer cellulose.  Bacteria can be engineered to modify properties of materials they produce and bioreactors "fed" waste. These things offer the opportunity for these processes to become both flexible and truly sustainable.

One difficulty is the issue of colour: as with animal-based leather, synthetic leathers often need to be artificially coloured, sometimes involving both bleaching and dying stages to transform the base material into a coloured product. Once again, these processes can be steps backwards on the journey to sustainability. However, work from Imperial College London, recently published in the journal Nature Biotechnology may change this totally.

Researchers at Imperial College, including Tom Ellis, a professor of synthetic genome engineering, have created a "self-dyeing" artificial leather, by modifying genes of a cellulose-producing bacteria to generate a black pigment. The upper part of a shoe was made in two weeks, which turned black after two more days. Separately, it has been shown that different bacteria can be engineered to produce coloured proteins in response to blue light. Work continues with new colours, hopefully to make many different colours of green material in future.