Bacteria against petrochemicals

Colors are everywhere. Both plants and materials produce a palette of so-called natural colors on a daily basis. But these colors are also produced chemically (synthetic dyes), to shape and brighten our worlds. Color is therefore an integral part of our experiences in the world; and while many people work with it on a daily basis, few, in reality, question its origin.

It was this research on the origin of colors that led to the founding of PILI. For this team of biologists, chemists and designers, it is a question of understanding where color comes from, how microorganisms - unicellular fungi and bacteria - produce it biologically, and ultimately, how to replace synthetic dyes derived from petrochemistry with a dye produced ecologically thanks to microbiology.

99% of the dyes currently used, especially in industries, in fact still come from this chemical manipulation made from petroleum molecules. It is no longer a secret that these large-scale petrochemical productions lead to massive CO2 emissions, with a very high carbon footprint. By working in microbiology, the PILI team is therefore trying to design a new way of producing color: ecological, sustainable, circular and accessible.

At the origin of PILI was an idea. That of a designer and a biologist, Marie-Sarah Adenis and Thomas Landrain, to discover where colors come from. Present everywhere, colors are however not trivial. Nature has an already broad spectrum of them: Roquefort blue, rot or even fungi are just a few examples of colorations produced - schematically - in the following way: more or less complex molecules absorb part of the light spectrum and return another part, thus creating a color. But the industry produces on a large scale.

This is why she needed to find solutions to produce an ever wider range of dyes that are resistant, durable over time and easily attached to the materials that we want to tint. These affordable dyes are mostly used by manufacturers. This leads to an obvious founding problem for PILI: petrochemicals cause huge CO2 emissions and dyes are therefore doubly polluting: both in their production and in their uses. How then to produce dyes in a manner ecological and on a large scale?

Simple experiments have paved the way for collaborative work with bacteria: by giving them what they want (to eat), they produce what we want (color). And since a good idea rarely goes unnoticed, the company quickly generated interest in the industry, looking for less polluting dyes. From a tinkering between biologists, a real creation project on an industrial scale began to be built. structured by Jérémie Blache, who is now CEO of the company. Biologists, chemists, designers have joined the ranks of the startup and PILI has now had around thirty employees.

To understand PILI well is to fully understand the meaning of the word ecological. What is sustainable in the long term and not harmful to the planet is ecological. Natural, on the other hand, does not always mean ecological: produced on a large scale, palm oil is natural but far from being ecological. This distinction between natural and ecological is important, because it makes it possible to understand the importance of finding a large-scale alternative to both petroleum derivatives and so-called natural dyes.

It would take an area of indigotine cultivation equivalent to Germany to create enough indigotine - the color indigo - to tint all the jeans produced worldwide. Indigotier, which produces the color of jeans, has a yield of the order of 50 kg/ha/year. Annual global demand exceeds 80,000 tons. Replacing petrochemical dye is therefore physically impossible with this type of dye.

Creating dyes in an ecological way therefore means thinking them viable on a large scale and sustainable in the long term (colors do not tire quickly). It is for this reason that the PILI team decided to take the textile industry as the very first field of experimentation by working on indigo. The textile industry is one of the most polluting and consuming industries of dyes. Acting, even if only on one color, would already have a significant impact on CO2 emissions.

So how does this process work in practice? It works by using the bacterium by then making a more or less complex genetic construction within the genome. By adding several enzymes in a row (from plants or fungi), we can create indigotine (a molecule) similar to that created by plants for petrochemicals.

“Basically, it's the same as brewing beer. Bacteria are raised in large tanks called fermenters, except that instead of yeasts brewing barley, bacteria mix agricultural waste. The colors come out. If we need to change the color or its properties, we work in chemistry (and not petrochemistry) with processes such as photocatalysis that do not involve fossil materials.”

This process makes it possible to recreate existing molecules such as indigo - no new molecules. This stable indigo emits 80% less CO2 and is used in the same way as dyes produced by petrochemicals. This therefore does not lead to any change in techniques or materials - which would greatly complicate things for manufacturers and limit the impact of this discovery in the short term.