Adèle Luthi-Maire
Ph.D. student
Department of Chemistry
Laval University

Supervised by:

Julien Gigault (Regular member)

Research project description

Study of degradation products of comon plastics by bacteria

Introduction: More and more bacteria are being identified as capable of degrading plastic, but most studies focus on modifying the plastic or bacterial communities. Of the few studies targeting degradation products, none takes into account the possibility of splitting plastic into micro and nano plastics. Objectives: - Develop a new analytical method to identify degradation molecules, whether polymers or nano- and microplastics. - Analyze the degradation products obtained during plastic degradation by bacteria selected for their ability to degrade plastic via ex-situ measurements from cultures in micro-fluidic chips. - Apply the method to environmental samples in order to isolate new plastic-degrading communities and compare degradation capacities as a function of environment.Study sites: 3 study sites are targeted, representing extreme conditions. - the former Cap Rouge landfill in Quebec City, Quebec, Canada - Ittoqqortoormiit open dump, Greenland - a former dump site in the Guadeloupe mangrove swamp, CaribbeanMaterial and methods: Bacteria are grown in a carbon-free nutrient medium. The source of carbon required for their growth is the plastic (PE, PS, PET or PVC) added to the medium. For objective 2, the bacteria have been previously isolated by other teams and are inoculated directly into the medium. For Objective 3, the bacteria come from plastics collected from landfill sites. In both cases, after exposure, the nutrient media are recovered. The biological material is separated from the plastic molecules. The fraction containing the degradation molecules is analyzed: the sample is pyrolyzed to thermodegrade the plastic particles, then the molecules (from pyrolysis and biodegradation by bacteria) are separated by gas chromatography and identified by mass spectrometry. It will also be possible to measure particle size if plastic polymers are found in the samples. Expected results: Bacteria are expected to degrade plastics not only into monomers, but also into micro and nano plastics and other more diverse types of molecules derived from the polymer's various fracture zones. Different bacteria are likely to degrade plastics into different molecules, depending on the conditions in which they grow. It is also expected that not all bacteria will degrade with the same ease. Polyethylene (PE) and polyethylene terephthalate degrade more easily than polyvinyl chloride (PVC) and polystyrene (PS).

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