Molecular insights into how organophosphate esters regulate conventional contaminants removal by Chlorella sorokiniana for synthetic wastewater treatment.

Organophosphate esters (OPEs) are typical types of emerging contaminants that are widely presented in wastewater. While they can serve as phosphorus (P) sources for microalgae growth, their toxicity disrupts metabolic processes, posing challenges to microalgae-based bioremediation. This study elucidated the regulatory effects of OPEs on the removal of ammonia (NH-N) and phosphate (PO-P) from synthetic wastewater by Chlorella sorokiniana, as well as the concurrent OPEs degradation, while unveiling the molecular mechanism of these interactions. OPEs exposure (1 and 10 mg/L) initially inhibited nutrient assimilation, reducing NH₄⁺-N and PO₄³⁻-P removal by 21.78 %-46.59 % and 7.46 %-26.07 %, respectively. The suppression was primarily attributed to oxidative stress-induced DNA damage, leading to G2/S cell cycle arrest, and metabolic disruptions particularly in crucial nitrogen assimilation enzymes (GS, GDH) and genes (IMPL2, IPPK) related to Pi supply strategy adjustment. Meanwhile, OPEs continuously impaired heterotrophy (NaAc matabolism), restricting energy supply for nutrient uptake. Despite this initial inhibition, microalgae exhibited adaptive recovery through photosynthetic regulation and EPS secretion. Enhanced linear electron transfer (LET) and Calvin cycle facilitated photoautotrophy, while EPS played a crucial role in OPEs adsorption and degradation via photosensitization and biosorption, achieving 41.53 %-54.50 % OPEs removal without additional energy input. Transcriptome analysis, combined with KEGG-based pathway annotation, was performed to elucidate the molecular mechanisms underlying these physiological responses. This study unveils a novel stress adaptation mechanism in microalgae, demonstrating their ability to mitigate OPEs toxicity and restore nutrient removal efficiency. The findings provide new insights into the synergistic bioremediation of emerging and conventional pollutants, offering a sustainable strategy for low-carbon wastewater treatment.