KOUADIO Konan Bertin

Affiliated CEAs :

• CEA-MEM at INPHB in Yamoussoukro (Côte d'Ivoire)

• CEA-EM at EMIG in Niamey (Niger)

Title:
Study of microbial communities at gold mining sites in Côte d'Ivoire and Niger and their potential impacts on biomining and bioremediation

Summary of the scientific project
. Although often illegal, gold panning plays a very important economic role, providing a livelihood for millions of people around the world. Such is the case in West Africa, one of the world's largest gold-producing provinces, situated in terms of volume just after China, Australia and Russia. However, when poorly managed, this activity can have disastrous consequences for the environment, society and health, through the use of toxic chemicals to extract the gold (mercury, cyanide, acids, etc.), the remobilization of toxic metals associated with gold such as arsenic, lead or thallium, the obstruction of waterways, deforestation, and the pollution of water, atmosphere and soil, which compromises the use of agricultural land.

Numerous microorganisms, naturally present in these multi-polluted environments, can be useful at different stages in the cycle of a gold panning site. They enable gold to be extracted more easily and with less impact on the environment (biomining or biohydrometallurgy), by limiting the use of toxic products such as mercury, cyanide or acids. They can also provide invaluable assistance in the remediation of polluted sites by precipitating toxic elements out of solution. They can also facilitate the development of plants used to clean up soils (by phytostabilization and plant cover, or by phytoextraction to extract toxic metals and metalloids from the soil).

The aim of this thesis is to study the microorganisms present at two gold mining sites, Kokumbo in Côte d'Ivoire and Koma Bangou in Niger. At present, very few studies have focused on these microorganisms using high-throughput sequencing. The taxonomic identification of these microorganisms and the study of their genetic diversity will be carried out by Illumina-MiSeq sequencing, in order to study their biodiversity, and by predictive metagenomics in order to better understand their potential roles on the site.

Another aspect of this work involves the isolation of strains with an effect on remediation, in particular of cyanide and mercury, two toxic products used in large quantities to extract gold in West Africa. This knowledge will help to improve the management of artisanal gold mining operations, and should ultimately provide solutions for promoting gentler gold extraction, with less impact on the environment, and bioremediation solutions for water and soil.

This work will also enable knowledge and skills to be transferred to the academic world and integrated into university and higher education courses in Côte d'Ivoire and Niger (INPHB, EMIG). This work will also enable the transfer of knowledge via public authorities, local populations and the sensitization and training of gold miners for better management of mines and mining waste.