SCIENCE BEHIND THE STYLE
Company founder Efthimia Lioliou says that positive trials were underway and a small factory with a 1,000-litre fermenter was running, but support from investors and industry failed to materialise. She had been working on this project for a decade before incorporating the company in 2017.
The biotech indigo developed by Pili has a level of purity equivalent to that of petrochemical indigo. PHOTO: PILI
Fermbox Bio introduced its Synbio-Indigo in 2024, joining the ranks of biotech firms engineering microbes to produce indigo through genetic modification. Using precision fermentation, the company says it achieves high purity and consistency in its dye. “Our product matches traditional indigo,” says founder Subramani Ramachandrappa, “but with the added advantages of better sustainability, traceability, and quality.” Petrochemical indigo is said to cost around $5 per kilogramme. This low price point poses a major challenge for bacteria-made indigo, as scaling production is the only path to lowering costs. Yet maintaining living cultures in tanks or reactors becomes increasingly complex at larger volumes, requiring sophisticated engineering to ensure stable temperature, even nutrient distribution, and consistent culture media. “There are ways to reduce costs through continuous culture, reusing media, using alternative sugars instead of glucose. But these will not happen overnight!” Ms Lioliou tells Inside Denim. “Scaling is the difficult part,” agrees Dr Sun. “The fermentation process involves a series of complex parameters and improper control can lead to abnormal microbial metabolism and even cell death.” He points out that all fermented materials face the same issues. Chloris feeds its microbes glucose derived from corn (~80%), which he says allows it to lower the price. Up till now Pili has outsourced the production of its pigment, but expects, one day, to have its own factory, and thus reduce costs. For now, it is working with a network of partners in Europe, sourcing sugar exclusively from European biomass, says Mr Blache. The company has joined several research projects working on ‘second generation’ sugars derived from wood, paper, agro-industry waste and even textiles. “We would like to be the first company to use textile waste as feedstock, creating a truly circular solution,” he says. Making the switch Dyeing is widely recognised as one of the most polluting stages in textile and apparel manufacturing. The advent of an indigo pigment having a radically lower environmental footprint compared to its petrochemical counterpart should incite change. While cost remains a critical factor in a price-sensitive market, it raises the question: What proportion of a product’s total price does dye actually represent? Chloris’ factory in China can produce 10,000 tonnes a year of its Claessen Blue biotech dye. PHOTO: CHLORIS BIOCHEM
07 ISSUE 16 / 2025
Blues and indigos Pili’s Eco-Indigo shares the exact same molecular structure as the natural and synthetic varieties. Jérémie Blache, co-founder and CEO, says that what distinguishes them is their level of purity. Petrochemical indigo typically achieves 95% purity, while natural indigo ranges from 15% to 55%. Pili’s Eco-Indigo has a purity greater than 90%, making it a drop-in solution for mills. Citing instances in which plant-derived indigo has been found to be made from a blend of natural and petrochemical pigments, he says Pili’s Eco-Indigo “is controllable, auditable, traceable and high performance”. Chloris’ bacteria-made pigment, Claessen Blue, is blue, but not technically indigo. “It doesn’t have the same molecular structure as indigo, but it can produce nuances that are as dark,” says Dr Sun. His interest was sparked by microbes that naturally generate a blue hue, first documented by German scientist H. Claessen in Berlin in the late 19th century. “He did fantastic work identifying a natural microorganism that produces the dye, and this allows our process to be highly efficient,” says the synthetic biologist who has been studying natural dyestuffs for 18 years. Pigments found in nature often pose challenges, he notes, as many are toxic and can damage the very cells producing them in fermentation tanks. By choosing a pigment produced by a natural, non-modified organism, he says that Chloris can achieve higher yields. “This enables us to lower costs and bring our price close to that of synthetic indigo.”