Novel putative PETase candidates from metagenomic mining of Ebrié lagoon and Kassembié lake, Côte d'Ivoire

Microplastic pollution poses a growing threat to Ivorian aquatic ecosystems, especially in urban areas where solid waste management remains inadequate. The Ébrié lagoon receives around 200,000 tons of plastic waste each year, much of which ends up in the form of microparticles in the water and sediments. Considering this, the enzymatic biodegradation of polyethylene terephthalate (PET) represents a promising bioremediation pathway, but the microorganisms capable of contributing to it in this ecosystem have remained unknown until now. This study applied a comparative shotgun metagenomic approach to samples taken from two sites with distinct levels of contamination: Biétry Bay (polluted site) and Lake Kassembié (reference site). The taxonomic analysis revealed a high microbial diversity at the two sites, with 131 unclassified bacterial species, 58% of which were exclusive to the polluted site. Functional annotation identified 15,860 hydrolases encoding genes and 195 genes from the CE1 carbohydrate esterase family. Structural validation by AlphaFold2 and TM-align identified four new putative PETases, designated BietPETase1 to BietPETase4. These results demonstrate that the microbiome of the Ébrié lagoon constitutes a reservoir of enzymes degrading PET and underline the potential of metagenomics for the discovery of plastizymes in aquatic ecosystems of Côte d'Ivoire.