Insights into the effect of cerium oxide nanoparticle on microalgal degradation of sulfonamides.

Nanoparticles have been commercially used worldwide; however, there is a lack of information of their environmental impacts and ecotoxicity. In this study, the effect of cerium oxide nanoparticle (CeONP) on a green microalga Scenedesmus obliquus, and microalgal biodegradation of four sulfonamides (sulfamethazine, sulfamethoxazole, sulfadiazine, and sulfamethoxazole) was investigated. There is insignificant inhibition of microalgal growth induced by CeONP; however, it substantially influenced the expression of genes involved in key cellular metabolic activities of S. obliquus. For example, genes involved in photosynthetic activity (psbA) and energy production (ATPF0C) were downregulated with exposure to CeONP. The low concentrations of CeONP improved microalgal degradation of sulfonamides. This may be because of the upregulated genes encoding hydrogenase and oxidoreductase. The exploration of this study has provided a new understanding of the environmental impacts of CeONP on microalgae-based biotechnologies for treatment of wastewater containing emerging organic contaminants.