From Phytoremediation to Biorefinery: Downstream Processing of Tetradesmus obliquus Cultivated in the Presence of Cosmetic UV Filters

The use of microalgae for wastewater treatment offers a sustainable approach for removing emerging contaminants (EC) while generating biomass that might be further utilized. However, the presence of persistent organic pollutants, such as some cosmetic UV filters, raises important questions about the safety and real applicability of the resulting biomass. In particular, the fate of these contaminants during further downstream processing (DSP) in a biorefinery is unknown. In this study, Tetradesmus obliquus was cultivated in the presence of representative UV filters commonly used in sunscreen formulations, at concentrations relevant to cosmetic wastewater. The effects of individual and combined contaminants on microalgal growth were evaluated, together with the uptake of selected UV filters by the biomass. For this, an HPLC-DAD method was developed to detect and quantify the target compounds in the culture medium and biomass extracts. Preliminary results showed that contaminant exposure influenced growth in a dose-dependent fashion, while HPLC analyses indicated that a fraction of the UV filters remained in the harvested biomass. Current work focuses on developing a DSP strategy based on sequential fractionation. The objective is to determine the distribution of UV filters among the aqueous, lipid-rich, and residual solid biomass fractions, providing key insights into their fate during biomass processing and the implications for its potential valorization within a circular bioeconomy framework.