Laboratoire Charles Coulomb UMR 5221 CNRS/UM2 (L2C)


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18 months Postdoctoral Position - Kinetics of degradation and fragmentation of a polymer in the environment

par Christelle EVE - publié le

Pollution by microplastics is a major societal problem. However, little is known about their fate and their lifespan in the environment. The aim of this project is to understand and model the biodegradation kinetics and the physico-chemical modifications of polymers during their alteration in the environment. The first step of biodegradation is the colonisation of the surface by microorganisms, forming a biofilm. Degrading exo-enzymes are then produced with the ability to hydrolyse the polymer chains and cut them into smaller chains. Once the polymer chains are small enough, they can finally be assimilated by microorganisms.

We previously studied the enzymatic degradation of a biodegradable polymer as a function of its crystalline microstructure and developed an analytical model predicting its evolution1. In order to get closer to the real process, we will, in a second time, include the additional complexity due to the colonization of the polymer by microorganisms2.
The recruited post-doctoral researcher will carry out a three-step study on a polymer whose biodegradability in soil and compost has been demonstrated :
1- polymer in enzymatic solution for reference.
2- polymer in the presence of an artificial simplified biofilm.
3- polymer in the presence of a bacterial monoculture.

Films of various microstructures (spherulites of different sizes, shish-kebabs, ...) will be produced by different physico-chemicals pre-treatments. During polymer degradation, we will monitor over time not only the rate of enzymatic hydrolysis (titration, weight loss) but also the evolution of the erosion patterns (topographic and mechanical measurements by AFM and SEM) and the release of micro and nanoparticles or oligomers in solution (static and dynamic light scattering, SEC, HPLC). We have also developed a recognition program for areas of a typical size of a few tens of microns in a sample of several cm2, in order to be able to co-locate the biofilm and the induced erosion patterns.
This study will provide important quantitative elements for the development of innovative green solutions : enzymatic recycling, new biodegradable materials.
The part of the study involving bacterial culture will be done in collaboration with E. Gastaldi, from IATE, INRA, Montpellier.

Expected skills : we are looking for a physicist or a physico-chemist, with a good knowledge in the field of soft matter and polymers and a strong interest in living systems. The candidate will have to deal with instruments such as AFM and SEM as well as homemade setups. Strong experimental skills are therefore required. Data/images analysis expertise and ability to model the experiments will also be necessary.

1 T. Gaillard, M. George, E. Gastaldi, F. Nallet and P. Fabre, Soft Matter (2019) DOI:10.1039/C9SM01482A
2 M. Salomez, M. George, P. Fabre, F. Touchaleaume, G. Cesar, A. Lajarrige, E. Gastaldi Polymer Degradation and Stability 167 (2019) 102-113

Contacts :
Matthieu GEORGE
Pascale FABRE