[PhD Defense] Abel Cousin

PR Eric POLLET

Polymers; High-throughput screening; Biodegradation; Microorganisms; Enzymes

The studies presented in this manuscript are part of the PLASTILOOP2.0 industrial chair. Its ambition is to develop a new recycling process for two families of petroleum-based aromatic polymers, polysulfones (PSU) and poly(bisphenol A carbonate) (PBPAC). The first stage of this project, which is the subject of this thesis, focuses on the biodegradation of polymers into oligomers and branched aromatic compounds, exploring biodiversity in search of suitable biocatalysts. In order to effectively monitor the degradation of the two target polymers, we began by developing an analytical panel of five specialized methods, which we fully characterized and adapted to our conditions. These complementary methods enabled us to reliably study the hydrolysis of PBPAC and identify the products and intermediates formed. More importantly, part of this panel could be adapted to high throughput, allowing for rapid screening of biocatalysts derived from biodiversity. It was initially applied to the evaluation of a collection of 700 microorganisms isolated from soil samples contaminated with polymers, using two polycarbonates and PSU as targets. However, to date, no strain capable of degrading the polymers studied has been identified using this approach. On the other hand, this analytical panel gave us access to a parallel screening of commercial enzymes, one of which proved to be effective in depolymerizing one of the target polymers. Finally, the conclusion of this thesis consisted of optimizing the degradation conditions with this enzyme.