Microalgae-mediated bioremediation: Metabolomic profiling and Adaptive Responses under Amoxicillin-induced stress

This study examines the effects of varying concentrations (25, 50, 100, and 150 mg/L) of Amoxicillin-3000 (AMOX), a widely prescribed beta-lactam antibiotic, on the growth of the microalga Chlorella sorokiniana UUIND6. Results revealed that low AMOX concentration (25 mg/L) stimulated best algal growth, prompting further exploration of AMOX degradation processes, identification of transformation products, biochemical composition of microalgae. Photodegradation, both direct (light) and indirect (induced by microalgae) was examined. LCMS identified similar transformation product in both the photodegradation with a m/z ratio of 367.1. Moreover, microalgae-induced c photodegradation resulted in negligible zone of inhibition after 96 h, achieving an impressive 98.8% degradation, significantly surpassing the 85.5% degradation observed with light alone. Modifications in abiotic factors also influence the stoichiometry of microalgae cells, resulting in significantly higher lipid (31.24 ± 2.93%) and protein (44.12 ± 1.75%) content compared to control cells (lipid 23.6 ± 2.4%, protein 31.62 ± 1.52%), indicating notable metabolic alterations (p<0.05) under AMOX-induced stress. Additionally, increased reactive oxygen species (ROS) scavenging activity (48.89 ± 2.51%) suggests photosynthetic impairment and a decrease in TPC and TFC content, aiding in the prevention of oxidative stress. Overall, this study highlights the advantages of Chlorella-induced bioremediation of AMOX via photodegradation over light-driven processes. It presents a practical, sustainable approach for mitigating ecological risks in freshwater ecosystems and provides insights into antibiotic removal mechanisms and performance in microalgae-based systems under environmentally relevant conditions.