Pb(II)-phycoremediation mechanism using Scenedesmus obliquus: cells physicochemical properties and metabolomic profiling

M Danouche; N El Ghachtouli; A Aasfar; I Bennis; H El Arroussi

doi:10.1016/j.heliyon.2022.e08967

Pb(II)-phycoremediation mechanism using Scenedesmus obliquus: cells physicochemical properties and metabolomic profiling

Heliyon. 2022 Feb 15;8(2):e08967. doi: 10.1016/j.heliyon.2022.e08967. eCollection 2022 Feb.

Authors

M Danouche^{1

2}, N El Ghachtouli², A Aasfar¹, I Bennis¹, H El Arroussi^{1

3}

Affiliations

¹ Green Biotechnology Center, Moroccan Foundation for Advanced Science, Innovation and Research (MAScIR), Rabat, Morocco.
² Microbial Biotechnology and Bioactive Molecules Laboratory, Sciences and Technologies Faculty, Sidi Mohamed Ben Abdellah University, Fez, Morocco.
³ AgroBioScience (AgBS), Mohammed VI Polytechnic University (UM6P), Ben Guerir, Morocco.

Abstract

This study highlights the mechanisms of Pb(II)-phycoremediation using the Pb(II) tolerant strain of Scenedesmus obliquus. First, monitoring of cell growth kinetics in control and Pb(II)-doped medium revealed significant growth inhibition, while the analyses through flow cytometry and Zetasizer revealed no difference in cell viability and size. Residual weights of control and Pb(II)-loaded cells assessed by thermogravimetric analysis were 31.34% and 57.8%, respectively, indicating the uptake of Pb(II) into S. obliquus cells. Next, the use of chemical extraction to distinguish between the intracellular and extracellular uptake indicated the involvement of both biosorption (85.5%) and bioaccumulation (14.5%) mechanisms. Biosorption interaction of Pb(II) ions and the cell wall was confirmed using SEM-EDX, FTIR, zeta potential, zero-charge pH, and contact angle analyses. Besides, the biochemical characterization of control and Pb(II)-loaded cells revealed that the bioaccumulation of Pb(II) induces significant increases in the carotenoids and lipids content, while it decreases in the chlorophyll, carbohydrates, and proteins content. Finally, the metabolomic analysis indicated an increase in the relative abundance of fatty acid methyl esters, alkanes, aromatic compounds, and sterols. However, the alkenes and monounsaturated fatty acids decreased. Such metabolic adjustment may represent an adaptive strategy that prevents high Pb(II)-bioaccumulation in cellular compartments.

Keywords: Biochemical composition; Metabolomic profiling; Phycoremediation; Physicochemical properties; Scenedesmus obliquus.