THEOretically driven engineering of BIOsynthetic textile DYes – THEOBIODY

The textile industry is considered responsible for 4% of the global greenhouse gases emissions. Among the whole manufacturing process, dyeing steps are the most impacting ones: each year, over 100 million tons of fibres are manufactured requiring about 2 million tons of dyes, thus generating a considerable amount of waste. Dye manufacturing consists in two phases: 1) the synthesis of building blocks (usually polyaromatic) and; 2) the functionalization of those building blocks to introduce auxochromic or solubilizing groups, relying on harsh and wasteful processing conditions.
To date, the private company PILI has brought an answer to phase 1 and is the owner of a recombinant microorganism strain able to express heterologously the biosynthetic route of a simple anthraquinone (AQ) chromophore at unprecedented titres. PILI’s bioengineered bacteria represent a primary breakthrough in the field towards a genuinely low-cost access to AQ dye production: switching from petroleum derived to biobased dye intermediates reduces the global warming potential and cumulative energy demand by a factor of 9. Nonetheless, for the second phase of dyes production consisting in the functionalization of the AQ building blocks no sustainable solution is available to date and highly polluting nitration/reduction and sulfonation reactions are still playing a prominent role in large-scale production.
The THEOBIODY project aims at providing sustainable solutions for the second phase of dyes production – functionalisation – using a theoretically driven molecular engineering of the renewable aromatic scaffolds produced biosynthetically by PILI. To this end, quantum chemical modelling and screening will be combined with recent synthetic advances in green chemistry such as photocatalysis and flow chemistry to produce AQ dyes with targeted colours in a rational and environmentally friendly manner
Within the THEOBIODY project we will first setup computational protocols enabling the accurate prediction of all the tinctorial properties of the bio-derived AQ scaffolds that will be used to screen in a cost, time and environmentally efficient way among the best dye candidates (WP1).
Once the most relevant target dyes identified, the second goal of this project is to optimize their synthetic routes by combined theoretical and experimental approaches (Phase 2 of dyes manufacturing, WP2 and WP3). Indeed, considering both the well-known photosensitizer behavior of AQs and the tendency of widely used oxygenated, aminated or thiol-derived auxochrome groups to generate radicals, we envisage a photocatalytic approach as versatile and environmentally friendly synthetic route to access a large variety of dyestuffs candidates. Photocatalytic routes open an atom-economical access to radical chemistry, without relying on stoichiometric toxic reagents and heating at high temperatures, they can be carried out with organic dyes as environmentally benign photocatalysts (including the AQ substrate itself) and they can nowadays be safely and cost-competitively scaled-up using continuous flow processing.
Nonetheless, selectivity remains a major issue and the reaction mechanisms associated with these transformations are far to be easily optimized on the sole experimental basis. The THEOBIODY project aims at making use of a theoretical approaches prior and in combination with experiments to identify and optimize possible regioselective synthetic routes to target dyes. This objective is challenging from both the theoretical and experimental point of view and requires the complementary expertise of the three partners: iCLeHS (theory), PILI (industrial and biosynthetic routes) and CNAM (photocatalysis and flow chemistry)
Overall, the success of the THEOBIODY project will allow to pave the route of a fully environmentally friendly and cost-competitive access to biobased textile dyes through theoretically driven synthesis up to their optimization in a pre-industrial production context.