DeGraph

Graphene-based materials (GBMs), including graphene (G) and graphene oxide (GO), start to be present in all environmental compartments i.e. air, water and soils as a consequence of their diverse industrial developments. Thus, it is of fundamental interest to question about the potential adverse effects of these materials on organisms as well as their persistence in the environment. Despite the abundant bibliography focused on GBMs, there is still a limited number of studies reporting in vivo biological degradation of this type of two-dimensional nanomaterials. The aim of this proposal is to combine the knowledge and expertise of different research groups in microbiology, biotechnology and nanomaterials to explore the ability of environmental bacteria to degrade and to interact with G and GO. To perform the project, a straightforward approach will be used. First, samples from graphitic deposit sites will be collected and the diversity of indigenous bacterial communities will be deciphered and identified. Culture-dependent methods with diverse growth media and abiotic conditions (T, pH) for enriched cultures will be implemented, along complementary culture-independent methods. 16S rDNA gene sequencing of extracted DNA will be used to infer taxonomic identifications. Second, as naphthalene degraders would be also potential GBM degraders, screening of collections of bacteria (belonging to the partners of this project) isolated from hydrocarbons and metals contaminated sites for this function will be performed. Then, experiments will be set up in continuous flow-cell and columns reactors, and in batch and semi-batch flask reactors, in which fully characterized GBM materials could interact with the previously isolated bacteria, as a single strain or bacterial consortia during 45 days. The kinetic monitoring of G and GO degradation/modifications by the selected bacteria will be investigated at regular intervals by electron microscopy (TEM/SEM) and spectroscopy (XPS, Raman) methods. Besides, experiments with 13C-labelled GBMs will allow us to determine by HR-MAS NMR the carbon uptake/assimilation by bacteria. Finally, interactions of bacteria with G and GO leading to degradation of these materials or to surface modifications will also be investigated in bioflotation experiments as they can provide insights on the degradation mechanisms. Thus, the project targets to isolate bacteria, from environmental graphite-containing samples and/or strain collections, which possess potent abilities towards the degradation of GBMs. Achieving this objective, the project will improve, refine and fill the gaps of the current knowledge on the environmental fate of GBMs and more particularly on the bacterial contribution to the bioprocesses of degradation. The findings of this basic research project will help to develop prospective bioremediation processes as well as to resolve a soon-to-be societal issue.