Assessing ecotoxicity, removal efficiency, and molecular response of freshwater microalgae to bisphenol AP

Abstract

Bisphenol AP (BPAP), an analog of BPA and endocrine disrupter, is increasingly being detected in water, signaling its rise as an environmental contaminant similar to BPA, which is known for its health implications. This study investigated the ecotoxicity of BPAP in four freshwater microalgae (Chlorella sorokiniana, Chlamydomonas mexicana, Scenedesmus obliquus, and Chlorella vulgaris), along with their removal potential and biotransformation. This was followed by de novo transcriptomic analysis to elucidate the molecular response after BPAP exposure. The toxicity (120 h-EC50) of BPAP for microalgal species ranged from 1.509 mg L−1 to 6.509 mg L−1. C. mexicana exhibited the highest removal efficiency of 86.5 % after 12 days, followed by C. vulgaris (86.0 %), S. obliquus (78.9 %), and C. Sorokiniana (56.5 %) at 1 mg L−1. Eight biotransformed BPAP products were analyzed, and their toxicity was predicted to be lower than that of BPAP using the Ecological Structure Activity Relationships software. Transcriptomic analysis of C. mexicana revealed the differential expression of 4611 genes in processes related to metabolism, cellular activities, and stress responses. Genes encoding methyltransferases, glycosyltransferases, and various oxidoreductases, including electron-transferring flavoprotein dehydrogenase and glutaredoxin, were significantly upregulated in algal cells exposed to BPAP, suggesting the potential of C. mexicana for BPAP detoxification via glycosylation and transmethylation. These results offer novel insights into the ecotoxicity, removal potential, and biotransformation of BPAP in freshwater microalgae, with transcriptomic analysis, elucidating the molecular mechanisms of BPAP detoxification for effective environmental remediation.